TOPOGRAPHICAL AND GEOLOGICAL NOTICES,
BY
JOHN RICHARDSON, M.D., F.R.S., &c.
SURGEON AND NATURALIST TO THE EXPEDITION.
[Read before the Geological Society.]
A very limited portion of my time could be allotted to geological inquiries. For eight months in the year the ground in the northern parts of America is covered with snow; and during the short summer, the prosecution of the main object of the expedition rendered the slightest delay in our journey unadvisable. The few hours that could be stolen from the necessary halts, for rest and refreshment, were principally occupied in the collection of objects for the illustration of botany and zoology. It is evident, that an account of the rock formations, drawn up under such circumstances, cannot be otherwise than very imperfect; but I have been led to publish it from the belief that, in the absence of more precise information, even the slightest notice of the rocks of the extreme northern parts of the American continent would be useful to those employed in developing the structure of the crust of the earth; the more especially, as it is not probable that the same tract of country will soon be trod by an expert geologist. The specimens of rocks I obtained have been deposited in the Museum of the Geological Society, and are referred to in the ensuing pages by the numbers affixed to them. The notices are arranged nearly in the order of the route of the expedition, commencing with Great Bear Lake, where our winter quarters were situated.
GREAT BEAR LAKE.
Great Bear Lake is an extensive sheet of water, of a very irregular shape, being formed by the union of five arms or bays in a common centre. The greatest diameter of the lake, measuring about one hundred and fifty geographical miles, runs from the bottom of Dease Bay, which receives the principal feeding stream, to the bottom of Keith Bay, from whence the Bear Lake River issues, and has a direction from N.E. to S.W. The transverse diameter has a direction from N.W. by W. to S.E. by E., through Smith and M'Tavish Bays, and is upwards of one hundred and twenty miles in length. M'Vicar Bay, the fifth arm of the lake, is narrower than the others, and being a little curved at its mouth, appears less connected with the main body of water. The light bluish-coloured water of Great Bear Lake is every where transparent, and is particularly clear near some primitive mountains, which exist in M'Tavish Bay. A piece of white rag, let down there, did not disappear until it descended fifteen fathoms. The depth of water, in the centre of the lake was not ascertained; but it is known to be very considerable. Near the shore, in M'Tavish Bay, forty-five fathoms of line did not reach the bottom. Owing to the barometers supplied to the expedition having been broken in an early period of its progress, the height of the surface of Bear Lake above the Arctic Sea could not be ascertained; but it is, probably, short of two hundred feet.[20] If this supposition comes near the truth, the bottom of M'Tavish Bay is below the level of the sea, and towards the centre of the basin of the lake the depression is probably still greater. The great lakes, Huron, Michigan, and Superior, which discharge their waters into the St. Lawrence, are reported to sink three hundred feet below the level of the ocean; and the Lake of the Mountains, or Chipewyan Lake and Great Slave Lake,[21] through which the Mackenzie flows, have, it is highly probable, some portions of their beds below the sea level.
In the autumn of 1825, I coasted the western and northern shores of the Great Bear Lake; and in the spring of 1826, travelled on the ice along its eastern and southern arms, leaving no part of its shores unexamined on these two surveys, except the north side of M'Tavish Bay. I did not, however, on these occasions, make excursions inland.
PRIMITIVE ROCKS.—GREAT BEAR LAKE.
At the south-east corner of M'Tavish Bay, primitive rocks form a hilly range which, at the distance of a mile or two from the shore, attains an elevation of eight hundred or one thousand feet. The steep face of the range forms the shore of the lake for fifteen miles, and perhaps further, on a direction from N.W. by W. to S.E. by E., and is prolonged on the latter bearing, at the back of the lower country lying towards Point Leith. The general form of the hills is obtuse-conical, in some instances approaching to dome-shaped. None of them rise much above the others, and the vallies between them are seldom wide or deep. At a distance, some of the masses of rock appear round-backed; and in certain points of view, the crest of the ridge seems to consist of mammillary peaks. On a nearer approach, the individual hills are found to be composed of rounded eminences, having summits, generally, of an oblong form, and consisting of smooth, naked rock. Small mural precipices are frequent, and many detached blocks of stone lie beneath them. Between the eminences, there are level spots destitute of vegetation, and covered with small stones or gravel not much worn. A considerable portion of the gravel is granite or quartz, the debris, perhaps, of the rocks, of which the hills consist; it contains also some pieces of slate, and not a few of quartzose sandstone, neither of which I observed in situ. In the course of a walk of two miles over these hills, the only rock I observed was granite, verging in a few places towards gneiss, and generally whitish, with black mica. Sometimes the felspar is brownish-red, and the rock not unfrequently contains disseminated augite? The weathered surface of the stone was every where of a brick-red colour. In many spots the rocks split into such thin slaty looking tables that they have the appearance of being stratified. The slaty masses are, generally, vertical; but in one hill they were observed dipping 80° to the south-east. The direction of the tabular masses is mostly across the oblong summits of the hills. The appearances of stratification were not observed to extend through a whole hill, and seemed, in fact, to be confined to the more decomposable granites; but the naked rocks are every where traversed by smooth fissures. The blocks, which lie under the cliffs, have sometimes a tabular form, but more generally come nearer to a cube or rhomboid, and present one or two very even faces. Few veins were noticed. In the more sheltered vallies, some clumps of white or black spruce trees occur; but the hills are barren.
The point of land which lies between M'Tavish and M'Vicar Bays has low shores; but five or six miles inland, an even-backed ridge rises gradually to the height of three or four hundred feet, and abuts obliquely against the primitive hills. I did not visit this ridge, and the snow prevented me from seeing any flat beds of rocks, if such exist on the shore. On one point, however, near the north end of Dease Bay, many large angular blocks of whitish dolomite were piled up, and I have little doubt of the rock existing in situ in that immediate neighbourhood.
M'Tavish Bay is forty miles long, and twenty wide, and its depth of water, near the eastern shore, exceeds forty-five fathoms. Some shoals of boulders skirt the coast near Point Leith. M'Vicar Bay is about seventy miles long, and from eight to twelve wide; and at the "fishery," in a narrow part, not far from its bottom, its depth of water, two miles from the shore, is twelve fathoms. Dease Bay is equal to M'Tavish Bay in extent, and opens to the S.W. into the body of the lake. The high lands at the N.E. end, or bottom of this bay, have an even outline, and appear to attain an elevation of eight or nine hundred feet, at the distance of six or seven miles from the shore. Near its east side lie the lofty islands of Narrakazzæ which rise seven hundred feet above the lake. Dease River, the principal feeder of the lake, falls into the bottom of Dease Bay. It is two hundred yards wide, and from one to three fathoms deep near its mouth. A few miles up this river a formation of soft red sandstone occurs, which will be noticed hereafter.
LIMESTONE.—GREAT BEAR LAKE.
At the mouth of Dease river there are hills five or six 228*hundred feet high, composed principally, or entirely, of dolomite in horizontal strata. Some of the beds consist of a thick-slaty, fine-grained dolomite, containing dispersed scales of mica, which is most abundant on the surfaces of the slates. 228Most of the beds, however, consist of a thin-slaty, dull, purplish dolomite, traversed by veins of calc-spar. The structure of this rock is compact, approaching to fine granular; and some of the beds have what quarry-men term "clay-facings," that is, they are encrusted with a thin film of indurated clay.
Greenstone slate? occurs in horizontal beds on the north shore, eight or nine miles to the westward of Dease River: and at Limestone Point,[22] about twenty miles from the river, a small range of hills terminates on the borders of the lake, in shelving, broken cliffs, about two hundred feet high. These cliffs consist chiefly of nearly compact light-coloured dolomite, interstratified with greenstone, and a brownish-red limestone, such as occurs in the hills at the mouth of the Dease River. In contact with the greenstone, there is a bed of talcose limestone, having a curved, slaty structure; most of the beds of dolomite are hard, and pass into chert.
ALUMINOUS SHALE.—GREAT BEAR LAKE.
The north shore of Bear Lake is low, and is skirted by many shoals, formed by boulders of limestone. No rocks, in situ, are exposed between Limestone Point and the Scented Grass Hill, a remarkable promontory, which separates Smith and Keith bays. Its height above the lake is betwixt eight and nine hundred feet, and in form and altitude it corresponds with the Great Bear Mountain, which, lying opposite to it, separates M'Vicar and Keith bays. I did not ascend either of these hills; but cliffs, corresponding in character to those of the aluminous shale-banks at Whitby, flank their bases; and the same formation probably extends along the north shore of Keith Bay, and some way down Bear Lake River. The ground skirting the Scented Grass and Great Bear Mountains is much broken, and consists of small, rounded and steep eminences, separated by narrow vallies and small lakes. Several shelving cliffs, about one hundred feet high, and some miles in extent are washed by Bear Lake. 251
244
246
247
249
250
248
They consist of slate-clay and shale, more or less bituminous, and the dip of the strata is in several places to the N.W. by N. At the foot of the Scented Grass Hill a rivulet has made a section to the depth of one hundred feet, and here the shaly beds are interstratified with thin layers of blackish-brown, earthy-looking swinestone, containing selenite and pyrites. Globular concretions of the same stone, and of a poor clay iron-stone, also occur in beds in the shale. The surfaces of the slates were covered with an efflorescence of alum and sulphur. Many crystals of sulphate of iron lie at the bottom of the cliff, and several layers of plumose alum, half an inch thick, occur in the strata. At the base of Great Bear Mountain, the bituminous shale is interstratified with slate-clay, and I found imbedded in the former a single piece of brown coal, in which the fibrous structure of wood is apparent. Sections of slate-clay banks, and more rarely of bituminous shale, occur in several places on the north shore of Keith Bay. In one place, about seven or eight miles from Bear Lake River, a bed of plastic and bituminous clay occurs, and in another, near Fort Franklin, there is a deposit of an earthy coal, which possesses the characters of black chalk.
It is probable that a magnesian limestone underlies this formation of bituminous shale. I have already mentioned the beds of dolomite, which are exposed on the north side of Bear Lake, and similar beds occur to the southward of the Great Bear Mountain, forming cliffs on the shores of M'Vicar Bay. At Manito Point, on the west side of the isthmus that connects Great Bear Mountain to the main shore, a low ridge of limestone rocks terminates on the borders of the lake, forming some bold cliffs and a remarkable cave. The stone has a gray colour and bituminous smell, and contains much interspersed calc-spar. The strata dip to the north-west.
VICINITY OF FORT FRANKLIN, GREAT BEAR LAKE.
Fort Franklin stands on the northern shore of Keith Bay, about four miles from Bear Lake River, upon a small terrace, which is elevated twenty-five or thirty feet above the lake. The bay, contracting towards the river, is about four miles wide opposite to the fort, and the depth of water there does not exceed four fathoms. Farther from the river, the east and west shores of Keith Bay recede to the distance of thirty miles from each other, and the depth of water in the centre of the channel greatly increases. The bottom of this bay, wherever it could be distinguished, was observed to be sandy, and thickly strewed with round boulders[23] of various primitive rocks of large size, which were particularly abundant near the river, and with large square blocks of limestone, most plentiful near the cape formed by the Scented Grass Hill. In the small bay between the fort and the river, shoals are formed by accumulations of boulders, and the shores are thickly strewed with them. 261 to 308Many of these travelled blocks consist of flesh-red granite, having only a small quantity of black mica, exactly resembling the primitive rocks seen in M'Tavish Bay, but noticed no where else near the lake. Boulders of the same description occur in shoals at the mouth of M'Tavish Bay, and on the shores which skirt the Scented Grass Hill which faces that bay, to all which places they may have been brought from the parent rock, by a current flowing from the east. On the northern shore of Bear Lake the great majority of the boulders consists of limestone. 266 282Two varieties of granite, which occur amongst the boulders, were recognised as being abundant rocks at Fort Enterprise, which is situated about one hundred and seventy miles south-east from M'Tavish Bay. Some of the boulders were of a peculiar-looking porphyry exactly resembling that which occurs in the height of land betwixt the Coppermine River and Dease Bay; several of sandstone and conglomerate, which probably came from the same quarter; of greenstone, perhaps, from the Copper Mountains, and of limestone from the northern shores of the lake, and from the isthmus of the Great Bear Mountain; all these places lying to the eastward or north-east.
The soil in the immediate vicinity of Fort Franklin is sandy, or gravelly, and covers, to the depth of one or two feet, a bed of clay of unknown thickness. Gravel taken from a spot thirty feet above the present high-water level of the lake, and out of the reach of any stream or torrent, contained rounded pebbles of granite, of greenstone, of quartz rock, of lydian stone, and of various sandstones, of which some were spotted, and others presented zones of different colours. These sandstones form a considerable portion of the gravel.[24]
The clay which lies under the soil is of a bluish-gray colour, and is plastic but not very tenacious. It is more or less mixed with gravel. During the greater part of the year it is firmly frozen; the thaw in the two seasons we remained there never penetrating more than twenty-one inches from the surface of the earth. In spots where the sandy soil is wanting, the clay is covered a foot deep, or more, by mosses, mostly bryum palustre, and some marsh hypna and dicrana, in a living state, for they seem to be converted very slowly into peat in this climate.
The ground rises gradually behind the fort, until it attains, at the distance of half a mile from the lake, the height of two hundred feet, forming, when viewed from the southward, an even ridge, running nearly east and west—which ridge is, in fact, the high bank of the lake, as it corresponds in height with the summit level of the banks of Bear Lake River, and of the southern shore of Keith Bay. The country extending to the northward, from the top of the bank, is nearly level, or has a very gentle ascent for about five miles, when a more abrupt ridge rises to perhaps three hundred or four hundred feet above the lake. The view from the summit of this second eminence is very extensive, the whole country as far as the eye can reach appearing to be a level, from which several narrow precipitous ridges of limestone arise. But, although the country around these ridges appears from a distance to be level, or very slightly undulated, yet it abounds in small eminences and steep-sided vallies of various shapes, some being rounded and basin-shaped, others long and narrow. Lakes and swamps are here so numerous, that the country, for at least sixty miles to the northward, is impassable in summer, even to the natives. There are many mounds of sand and gravel, and fragments of sandstone are frequent; but having travelled in this direction only in winter, when the ground was covered to the depth of upwards of three feet with snow, I had not an opportunity of examining its geological structure. White spruces cover the drier spots; larches, black spruces, and willows abound in moist places; the sandy hillocks are clothed with aspens, and the sides of the vallies support some canoe birches, with a thick undergrowth of dwarf birches, alders, and rose-bushes. The eminence from whence the view just described was obtained, appears like a ridge only in approaching it from the lake, for it rises very little above the general level of the country behind it. It has a direction from N.W. by N. to S.E. by S., and terminates about eight miles to the eastward of the fort, in a small bluff point on the shores of the lake and there the strata consist of slate-clay slightly bituminous. The banks immediately behind the fort also exhibit, in their ravines, a bluish slate-clay.
The land on the south side, or bottom, of Keith Bay, presents a nearly similar aspect to that just described, rising, on the borders of the lake, to the height of one hundred and fifty feet, and then running back to a great distance nearly level. It may be characterized as full of hollows, narrow vallies, ravines, and lakes; but it is not hilly, although it is traversed by ridges of limestone, which rise like walls through the flat country. The nearest of these ridges terminates on the borders of the lake at the Manito Point, (noticed in page vii.) It may be proper to remark here, that, in addition to the limestone ridges visible from Fort Franklin, or from the heights behind it, the summit of Clark Hill, bearing south, and forming part of a ridge about fifty miles distant, was distinctly seen. This hill lies behind Old Fort Norman on the Mackenzie, and has more the outline of a granitic rock, although some of the peaks which skirt it have the serrated crests which the limestone ridges in this quarter show. It was guessed to be 1500 feet high above the Mackenzie.
This sketch of the general features of the country about Fort Franklin being premised, the ensuing geological notices follow in the order of the route of the Expedition.
BEAR LAKE RIVER—SANDSTONE, LIMESTONE.
Bear Lake River is about seventy miles long, from its origin in the lake till it falls into the Mackenzie, and throughout its whole length, its breadth is never less than one hundred and fifty yards, except at the Rapid, a remarkable place, about the middle of its course. It is from one to three fathoms deep, and very rapid, its velocity being estimated at six miles in the hour. Its waters are clear as they issue from the lake, but several branches of considerable size bring down muddy water, particularly one which flows from the north, and falls in below the rapid.
Above the rapid, the valley of the river is very narrow, the banks every where sloping steeply from the level of the country. Their summit line, which is nearly straight, is about one hundred and fifty feet above the bed of the river. In some places they have an even face elevated at an angle of about forty-five degrees, and they are not unfrequently cut by ravines into pretty regular figures, resembling hay-ricks, or the parapet of a fort, the ravines representing the embrasures. Sections made by the river presented generally sand or clay; the sand probably proceeding from the disintegration of a friable, gray sandstone, which showed itself occasionally in a more solid form. The rapidity of our voyage, however, afforded us little opportunity of searching for the solid strata which are generally hid by the debris of the bank. About twelve miles above the rapid, a small-grained, friable sandstone, of a yellowish gray colour, and irregular earthy fracture, is associated with beds of bluish-gray slate-clay. These beds consist of concretions of various sizes and irregular shapes, but which may be said to approach in general to a depressed orbicular form; their surfaces are coloured purplish-brown by iron, and studded with crystals of sulphate of lime. This slate-clay contains many small round grains of quartz, and is exactly similar to that which occurs at the rapid, and which will be afterwards noticed. In other places the banks are covered by the debris of a slate-clay slightly bituminous, resembling wacke in its mode of disintegrating.
The Rapid is caused by the river struggling through a chasm bounded by two perpendicular walls of sandstone, over an uneven bed of the same material. On escaping from this narrow passage, it winds round the end of a lofty cliff of limestone, which forms part of a ridge that is continued through the country on both sides of the river.
Viewed from the summit of this ridge, which rises about eight hundred feet above the river, the country towards Bear Lake appears level. The view down the river presents also a plain country, bounded on the Mackenzie by another limestone ridge, which, unless the eye was deceived by the distance, gradually inclined to the one at the rapid, and appeared, by joining it to the northward, to form a great basin. These ridges are also prolonged to the southward. The plain is covered with wood, intersected by chains of lakes, and seemed to lie rather below the summit level of the banks of Bear Lake River. It is only comparatively, that the country deserves the name of plain, for its surface is much varied by depressions, ravines, and small eminences, that do not, however, destroy the general level appearance when seen from a distance. The view from the hill is terminated, to the westward, by the distant chain of the Rocky Mountains, running nearly N.W. by N. A little below the rapid, a small stream from the southward flows into the Bear Lake River, near whose sources the Indians procure an excellent common salt, which is deposited from the springs by spontaneous evaporation.
The walls of the rapid are about three miles long, and 120 feet high. 25They are composed of horizontal beds, the lower of which consist of an earthy-looking stone, intermediate between slate-clay and sandstone, having interiorly a dull yellowish-gray colour. Concretions, with smooth surfaces, about the thickness of a swan's quill, pass perpendicularly through the beds like pins, are prolonged beyond the partings, and bear some resemblance to portions of the roots or branches of a tree. The seam surfaces are very uneven. These beds are parted by thin, slaty layers, of a stone similar in appearance, but rather harder, and containing many 18
19
1827interspersed scales of mica, and also some minute portions of carbonaceous matter in the form of lignite. The thin layers contain impressions of ferns, and from the debris at the bottom of the cliff I gathered impressions of the bark of a tree (lepidodendron) and some ammonites in a brown iron-shot sandstone.[25] 18, 20, 21,
22, 23, 24,
26, 27,
28The upper beds are composed of a fine grained, quartzose, gray sandstone, having an earthy basis, and occasionally interspersed carbonaceous matter. Some of the beds are a foot and a half thick, and have sufficient tenacity to be fitted for making grindstones; most of the sandstone is, however, rather friable. Near the summit there is interposed a bed of fine-grained dolomite, and a friable sandstone, which forms the crest of the cliff, and exhibits in its weathering battlement-shaped projections and pinnacles. Covering this sandstone, but not quite to the margin of the cliff, there is a layer of slaty29 limestone, having a bluish or blackish-gray colour, a dull fracture, and rather compact structure. In the lower beds of the cliff there are some globular and disk-shaped concretions, of an indurated iron-shot slate-clay, or poor clay-iron-stone,30 containing pyrites. They vary in magnitude from six inches to a foot and a half in diameter, and appear to be formed of concentric layers, which are rendered apparent by the weathering of the stone. The sandstones and shales of the rapid have a strong resemblance in appearance to those of the coal measures; but pitch-coal was not detected at this place. Several distinct concretions of indurated slate-clay, assuming the appearance termed cone in cone, were picked up among the boulders on the banks of Bear Lake River, some way below the rapid, but they were not traced to their parent beds. They effervesce with acids.
Between the walls of the rapid and the limestone ridge there is a piece of meadow-ground, having a soft, clayey soil, in which, near the base of the hill, a small rivulet flows to join the river. The bed of this rivulet presents accumulations of boulders of large size, arranged so as to form two terraces, the upper of which is considerably above the highest level either of the rivulet, or of Bear Lake River. The boulders consist of varieties of granite, gneiss, mica-slate with garnets, greenstone and porphyry. 50One of the porphyries is a beautiful stone, composed of hyacinth-red felspar, and irregular crystals of milky quartz, with a few specks of a dark green mineral, and very much resembles a rock which is not uncommon in the gneiss districts about Fort Enterprize. 45,
47,
50,
51,
49Many of the boulders consist of conglomerates and sandstones that strongly resemble those of the old red sandstone formation, which forms the height of land between Dease Bay and Coppermine rivers. Also some flinty slates, mixed, in thin layers, with compact, yellowish limestone, and some pebbles of jasper interleaved with flinty slate.
The limestone ridge below the rapid stands on a narrow base, whose transverse diameter does not exceed a quarter of a mile. Its summits are generally conical, but very rugged and craggy; the highest peak I had an opportunity of visiting is about a mile from Bear Lake River, and it has been already stated to be estimated at eight hundred feet above that stream, or nine hundred and fifty above the sea. The general direction of the ridge is from S.E. by S. to N.W. by N., or nearly parallel to the great Rocky Mountain chain, and to the smaller ridges betwixt it and that chain. Its prolongation through the flat surrounding strata, to the southward of Bear Lake River, can be traced for at least forty miles, and it is visible at nearly an equal distance, as it runs through the still more level country to the northward; but here, as has been already said, it appears to incline towards the similar ridge which is cut by the Mackenzie, at the mouth of the Bear Lake River, and is about twenty-five miles to the W.S.W., in a direct line. That part of the ridge which I had an opportunity of visiting, consisted entirely of limestone, generally in thick beds. Its stratification was not very evident, and in my very cursory examination the general dip was not clearly ascertained. A precipitous cliff, four hundred feet high, facing the S.E., and washed by the Bear Lake River, presents strata, inclined to the S.W. at an angle of 45°, which may be perhaps considered as the general dip; for the ridge on that side slopes down to the surrounding country at an angle of about 30° or 40°, while on the N.E. side it presents lofty precipices formed by the cropping out of the strata. 39, 34
40Many of the beds in this hill consisted of a blackish-gray fine grained limestone, intersected by veins of calc-spar; but several layers of gray and dark coloured dolomites, and some of a yellowish-gray rauchwacke, were interstratified with them, and the upper parts of the precipitous cliff, 35, 36and also of the highest peak, consisted of a calcareous breccia, containing rounded pieces of brown limestone, and angular fragments42, 43, 44 of chert; and the faces of some cliffs, on the N.E. side of the hill, were incrusted with a fine crystalline gypsum to the depth of from one to two feet.[26]
The banks of Bear Lake River below the rapid have a more gentle declivity than those above it, and they occasionally recede from the stream, so as to leave a grassy slope varying from a few yards to half a mile in breadth. The sections of these banks by torrents present only sand or clay; and the hollows of the ravines are lined with boulders principally of primitive rocks. No stone was observed in situ from the rapid until we came to the junction of the river with the Mackenzie.
The Bear Lake River flows into the Mackenzie at a right angle, and on its north bank, at its mouth, there is a hill, which has been already noticed as forming part of a ridge visible from the one at the rapid, with which it probably unites to form a great basin. These two hills seem to belong to the same formation. 61, 62,
60The body of the hill consists of highly-inclined beds of blackish-gray limestone, with sparry veins, and of brownish-gray dolomite, which cannot be distinguished in hand specimens from that of the hill at the rapid. The superior beds are formed of a calcareous breccia.[27] 57,
58, 59,
63, 64,
65Associated with these strata, however, there are beds of limestone, highly charged with bitumen; and at the base of the hill there are beds of bituminous shale, some of which effervesce with acids, whilst others approach in hardness, and other characters, to flinty slate. These shaly beds were seen by Captain Franklin and Mr. Kendall in autumn 1825, and they also saw, at that time, some sulphureous springs and streams of mineral pitch issuing from the lower parts of the limestone strata: but the whole of them were hid by the height of the waters of the Mackenzie in the spring of 1826.[28] 69, 66,
67, 68The same cause prevented me from seeing some beds of lignite and sandstone, at the same place, of which Captain Franklin obtained specimens.
LIGNITE FORMATION.—MACKENZIE'S RIVER.
Having noticed the general features of this portion of the river, I have next to state, that the formation constituting its banks may be characterized as consisting of wood-coal in various states, alternating with beds of pipe-clay, potter's clay, which is sometimes bituminous, slate-clay, gravel, sand, and friable sandstones, and occasionally with porcelain earth. The strata are generally horizontal, and as many as four beds of lignite are exposed in some parts, the upper of which are above the level of the highest river-floods of the present day.
The lignite, when recently detached from the beds, is pretty compact, but soon splits into rhomboidal pieces, which again separate into slates more or less fine. It burns with a very fetid smell, somewhat resembling that of phosphorus, with little smoke or flame, leaving a brownish-red ash, not one-tenth of the original bulk of the coal. The blacksmith found it unfit for welding iron when used alone, but it answered when mixed with charcoal, although the stench it created was a great annoyance. Different beds, and even different parts of the same bed, presented specimens of the fibrous brown-coal, earth-coal, conchoidal brown-coal, and trapezoidal brown-coal of Jameson. Some of the pieces have the external appearance of compact bitumen, but they generally exhibit, in the cross fracture, the fibrous structure of wood in concentric layers, apparently much compressed. Other specimens have a strong external resemblance to charcoal in structure, colour, and 48lustre. A frequent form of the lignite is that of slate, of a dull, brownish-black colour, but yielding a shining streak. The slate is composed of fragments, resembling charred wood, united together by a paste of more comminuted woody matter, mixed, perhaps, with a small portion of clay. In the paste there are some transparent crystals of sulphate of lime, and occasionally some minute portions of a substance like resin. These shaly beds bear a strong resemblance to peat, not only in structure but also in the mode of burning, and in the light whitish ashes which are left. The external shape of stems or branches of trees, is best preserved in some fragments impregnated with slate-clay, and occasionally with siliceous matter, which occur imbedded in the coal. The bark of these pieces has been converted into lignite. Some of them exhibit knots, such as occur where a branch has decayed, and others represent the twists and contortions of wood of stunted growth. The lignite is generally penetrated by fibrous roots, probably rhizomorpha, which insinuate their ramifications into every crevice.
The beds of lignite appear to take fire spontaneously when exposed to the atmosphere. They were burning when Sir Alexander Mackenzie passed down the river in 1789, and have been on fire, in some part or other of the formation, ever since. In consequence of the destruction of the coal, large slips of the bank take place, and it is only where the debris has been washed away by the river that good sections are visible. The beds were on fire when we visited them, and the burnt clays, vitrified sand, agglutinated gravel, &c. gave many spots the appearance of an old brick-field.
81The gravel interstratified with the lignite, consists of smooth pebbles of Lydian stone, of flinty slate, of white quartz, of quartzose sandstone, and conglomerate, like the sandstones and conglomerates of the old red sandstone formation, of claystone, and of slate-clay, varying in size from a pea to that of an orange. The gravel is often intermixed with a little clay, which gives the bed sufficient tenacity to form cliffs, but does not prevent the pebbles from separating, in the attempt to break off hand specimens. It is seamed by thin layers of fine sand: beds of sandstone are of occasional occurrence.
Potter's clay occurs in thick beds, has generally a gray or brown colour, and passes, in some places, into a highly bituminous thick-slaty clay, penetrated by ramifications of carbonaceous matter resembling the roots of vegetables.
The pipe-clay is deserving of particular notice. It is found in beds from six inches to a foot thick, and mostly in contact with the lignite. It has commonly a yellowish-white colour, but in some places its hue is light lake-red. The natives use it as an article of food in times of scarcity and it is said to have sustained life for a considerable time. It is termed white mud by the traders, who whitewash their houses with it. It occurs also in lignite deposits on the upper branches of the Saskatchewan, and is associated with bituminous shale on the coast of the Arctic Sea. Mr. Nuttall mentions a similar substance, under the name of pink-clay, as being found in the lignite deposits on the Arkansa.[29]
The porcelain earth was observed only at one place where the beds were highly inclined, and there it appeared to replace the sandstones of other parts of the deposit. It has a whitish colour, and the appearance, at first sight, of chalk; but some of its beds, from the quantity of carbonaceous matter interspersed through them, having a grayish hue. Its beds are from two to three yards thick.
In a note[30] I have mentioned the most remarkable sections of this formation which occur on the banks of the Mackenzie. The depth of the formation was not ascertained, but the sections will show the thickness of the beds which were exposed. The height above the sea of the summit of the banks it forms on the Mackenzie, was estimated to be from two hundred and fifty to three hundred feet.
NOTICES OF OTHER LIGNITE FORMATIONS.
Similar formations of lignite occur near the foot of the Rocky Mountain range farther to the southward; but I have not, after many inquiries, heard of any traces of them in the eastern parts of the Hudson's Bay lands. Sir Alexander Mackenzie, after describing the general course of the Rocky Mountains, says that "along their eastern edge, there occurs a narrow strip of marshy, boggy, and uneven ground, which produces coal and bitumen;" and that "he saw these on the banks of the Mackenzie in lat. 66°, and, in his second journey, on the Peace River, in lat. 56° and 146° W. long.;" and further, that "the same was observed by Mr. Fidler, on the south branch of the Saskatchewan, in lat. 52° long. 112½° W." Mr. Alexander Stewart, an intelligent chief factor of the Hudson's Bay Company, and well acquainted with those countries, informs me that there are beds of coal on fire, on the Smoking River, or east branch of the Peace River, and on the upper parts of the Rivière la biche, or Elk River; and that coal, although not on fire, occurs at Lesser Slave Lake, on a line with the other two localities. Mr. Small, a clerk to the Hudson's Bay Company, likewise acquaints me, that coal occurs at Edmonton, on the north branch of the Saskatchewan, in beds, sometimes seven or eight feet thick. Most of the coal is thin-slaty; but some beds yield shining, thick lumps, which break, as he expresses it, like Spanish liquorice. It lies over beds of bluish-gray sandstone, and is associated with a white clay, which froths in water and adheres to the fingers.
Mr. Drummond brought specimens from the spot which Mr. Small alludes to and remarks, that the lignite occurs in beds from six inches to two feet thick, separated by clay and sandstones. 1051, 1052, 1053His specimens of the lignite are precisely similar to the slaty and conchoidal varieties, which occur at the mouth of the Bear Lake River; 1055and there is an equal resemblance betwixt the sandstones from the two places. 1053The slaty beds of lignite, at Edmonton, pass into a thin, slaty, friable sandstone, much impregnated by carbonaceous matter, and containing pieces of fibrous lignite. 1056, 1062In the neighbourhood of the lignite there are some beds of rather indurated, but highly bituminous shale, and the clayey banks contain clay-iron stones, in form of septaria. Mr. Drummond likewise found beds of a beautiful bituminous coal, which Professor Buckland, from its peculiar fracture, considers to be tertiary pitch-coal. The banks of the Saskatchewan, near the same place, exhibit beds of a very compact stone, having a brown colour, and inclosing many fragments of bituminous 1058, 1059, 1060limestone and some organic remains; likewise beds of a somewhat similar stone, but full of drusy cavities, and more resembling a recent calcareous tufa. I could not learn how far these beds were connected with the lignite deposit.
Captain Franklin[31] saw beds of lignite and tertiary pitch-coal at Garry's Island, off the mouth of the Mackenzie, and there is an extensive deposit of it near the Babbage River, on the coast of the Arctic Sea, opposite to the termination of the Richardson chain of the Rocky Mountains.
MACKENZIE RIVER FROM SLAVE LAKE TO THE BASE OF THE ROCKY MOUNTAINS.
Having now described the strata in Bear Lake River, together with the exposed beds of the lignite at its mouth, as far as opportunities of observation enable me, and also added a slight account of similar formations which occupy a like situation at the foot of the Rocky Mountain range, were I to adapt the order of my notices strictly to the route of the expedition, I should next describe the banks of the Mackenzie from the junction of the Bear Lake River downwards to the Arctic Sea. It seems, however, more advisable to commence at the origin of the Mackenzie, in Great Slave Lake, and give as connected a view as I can of the principal geological features of that great river.
The west end of Slave Lake is bounded by horizontal strata of a limestone, whose characters shall be afterwards given in detail; and I have merely to remark, at present, that it forms flat shores, which are skirted by shoals of boulders of limestone, and of primitive rocks. Much drift timber is accumulated in the small bays at this end of the lake, which, in process of time, is converted into a substance like peat. A chain of islands extends obliquely across the lake at the origin of the river, or where the current is first felt; and the depth of the water there is less than six feet. Below this, there is a dilatation termed the first little lake, and the river afterwards contracts to less than a mile in breadth; forming in one place, when the water is low, a strong rapid. A second dilatation, about twenty-five miles below the first, is termed the second little lake. The shores throughout this distance are generally flat and covered with boulders of limestone, compact felspar, granite, gneiss, and sienite, and there are many of these stones imbedded in a tenacious clay, which forms the beach. A ridge, having an even outline, and apparently of small elevation, commences behind Stony Point, in Slave Lake, some distance inland, and, running nearly parallel to the river, disappears about Fishing River, a stream which joins the Mackenzie, below the Second Little Lake. The Horn Mountains, a ridge of hills, of considerably greater elevation, and having a more varied outline than that on the south shore, are first visible on the north side of the Second Little Lake, and continue in sight nearly as far as the junction of the "River of the Mountains," or "Forks, of the Mackenzie," as the traders term the union of the two rivers. 120
121The only rocks seen in situ between Slave Lake and the Forks, were a bituminous shale of a brownish-black colour, in thin slates, and a slate-clay of a pure yellowish-gray colour, which, as well as the bituminous shale, forms steep banks.
ROCKY MOUNTAINS.
About twenty-five or thirty miles below the forks, the first view is obtained of the Rocky Mountains, which there appear to consist of short-conical peaks, scarcely rising two thousand feet above the river. Some distance lower down, the river, changing its course from W.N.W. to N.N.E., turns sharply round the mountains, which are there disposed in ridges, having bases from one to two miles wide, and a direction of S.S.W. or S.W. by S. being nearly at right angles to the general course of the great range to which they belong. The eastern sides of the ridges present a succession of wall-sided precipices, having beneath them shelving acclivities formed by debris, and exhibiting on their faces regular lines of stratification. The western sides of the ridges are of more easy ascent. The vallies which separate these ridges and open successively to the river, are narrow, with pretty level bottoms, but very steep sides well clothed with trees. In the first ridge, the strata seemed to dip to the northward at an angle of 35°. In some of the others they were horizontal, or had a southerly dip. The third ridge presents, when viewed from the westward, a magnificent precipice, seemingly about one thousand two hundred feet high, and which extends for at least fifteen miles. After passing this ridge, the river inclines to the eastward, and the forms of the hills are less distinctly seen.
As I could not visit the Rocky Mountains, I know nothing of their structure except from report. An interpreter in the Hudson's Bay Company's service, who had travelled over them, informed me that there are fourteen or fifteen ridges, of which the three easternmost are the most rugged, those that succeed being broader and more rounded. 122This man gave me a specimen of a pearl-gray semi-opal, resembling obsidian, brought from the third or fourth ridge. The natives, by means of fire, cause this stone to break off in thin, flat, conchoidal fragments, with which they form arrow-heads and knives. The thin pieces are nearly transparent on the edges. 123He also gave me a specimen of plumbago, from the same quarter, and some specular iron.
Mr. Macpherson, of the Hudson's Bay Company, in a letter respecting the Rocky Mountains, near Fort au Liard, on the River of the Mountains, or south branch of the Mackenzie, informs me, that "these mountains may be traced into somewhat uniform ranges, extending north-westerly and south-easterly, nearly parallel with the River of the Mountains, and are in appearance confusedly scattered and broken, rising here and there into high peaks." 124, 125This gentleman had the kindness to send me specimens of a cherty rock, some of which, he states, were from the third range westward from the river, and others from a spur which projects in a southern direction from the fourth range, and rises about six hundred feet above the adjacent valley. These specimens cannot be distinguished from those of Limestone Point, on the north shore of Great Bear Lake[32], Mounts Fitton and Conybeare, two remarkable peaks which terminate the Eastern range of the Rocky Mountains on the shores of the Arctic sea, were found by Captain Franklin to consist of transition rocks, of which an account is given in the subjoined note.[33]
Sir Alexander Mackenzie, towards the conclusion of the interesting narrative of his voyages, says, of the Rocky Mountain range, "The last line of division is, the immense ridge, or succession of ridges of the stony mountains, whose northern extremity dips in the Arctic Sea in latitude 70° north, and longitude 135° west, running nearly south-east, and begins to be parallel to the coast of the Pacific ocean from Cook's inlet, and so onwards to the Columbia. From thence it appears to quit the coast, but still continuing with less elevation to divide the waters of the Atlantic from those of the Pacific. In these snow-clad mountains rises the Mississippi, if we admit the Missouri to be its source, which flows into the Gulph of Mexico; the river Nelson which is lost in Hudson's Bay; Mackenzie's river that discharges itself into the North Sea, and the Columbia emptying itself into the Pacific Ocean. The breadth of the mountains from Cook's inlet to the Columbia is from four to eight degrees easterly." I may add, that the great rivers mentioned by Mackenzie not only take their origin from the same range of mountains, but almost from the same hill; the head waters of the Columbia and Mackenzie being only about two hundred yards apart in latitude 54½°. Mr. Drummond, who crossed the mountains at that place, informs me, that the Eastern side of the range consists of conglomerate and sandstone, to which succeed limestone hills exceedingly barren, and afterwards clay-slate and granite.
James, the intelligent naturalist, who accompanied Major Long on his first expedition, says of the Rocky Mountains to the southward of the Missouri, "They rise abruptly out of the plains which lie extended at their base on the east side, towering into peaks of great height, which renders them visible at the distance of more than one hundred miles from their base. They consist of ridges, knobs, and peaks, variously disposed, among which are interspersed many broad and fertile valleys. James's peak, one of the more elevated, was ascertained by trigonometrical measurement to rise 8500 feet above the common level. The rocky formations are uniformly of a primitive character, but a deep crust of secondary rocks appears to recline on the east side of the mountains, extending upwards from their base many hundred feet." In another place, he says, "The woodless plain is terminated by a range of naked and almost perpendicular rocks, visible at the distance of several miles, and resembling a vast wall parallel to the base of the mountain. These rocks are sandstone, and rise abruptly to an elevation of one hundred and fifty or two hundred feet." The sandstone walls seem to present an appearance not very dissimilar to some of the cliffs seen from the Mackenzie.
Having thus mentioned as briefly as I could the extent of the information I was able to collect, respecting the Rocky Mountain range, I may remark, that a formation of primitive rocks, but little elevated above the general level of the country, appears to run from near the west end of Lake Superior, gradually and slightly converging towards the Rocky Mountains, until it attains the east side of Great Bear Lake. In lat. 50°, the two ranges are nearly seven hundred miles apart, and there, and as far as lat. 60°, the space between them is principally occupied by horizontal strata of limestone. There is also much limestone in the narrower interval north of 60°, but the strata are more inclined, and form abrupt hills and ridges, particularly about lat. 66°, where the primitive rocks on the east of Bear Lake are within two hundred miles of the Rocky Mountains. Sir Alexander Mackenzie has noticed that a chain of great lakes skirts this eastern range of primitive rocks, where they are approached by the flat limestone strata which lie to west of them. Thus the primitive rocks bound Great Slave Lake to the eastward of Slave River, and the flat limestone strata occupy the country westward of that lake, as has been already mentioned.
After this digression, which seemed necessary for the purpose of giving a general idea of the structure of the country, I return to the description of the banks of the Mackenzie.
MACKENZIE RIVER FROM THE FIRST SIGHT OF THE ROCKY MOUNTAINS TO BEAR LAKE RIVER.
At the sharp turn of the river round the Rocky Mountains, its east bank swells gently into a hill several feet high. Below this the banks are broken into conical masses by ravines, and present a finely variegated outline. A pretty high ridge, looking like a continuation of the Horn Mountains, is visible on the east side some distance inland. Opposite to the Big Island there is a green hill three or four hundred feet high, which, as we descended the river, showed itself to be part of a range that had a direction apparently to the N.N.W., and towards its northern end became more rugged and craggy, exhibiting cliffs and rude embrasures, at the same time increasing in height to eight hundred or one thousand feet. The boulders on the beach change their character considerably about this place. Farther up, the yellowish-white limestone which occurs in Slave Lake formed a great portion of them; but here a greenish-gray, and rather dark-coloured, compact limestone, with a flat conchoidal fracture, replaces it. Variegated-sandstone, and some purplish, felspathose-sandstone, or compact felspar, also occur pretty frequently, together with slaty limestone, bituminous-shale, lydian-stone, pitchstone-porphyry, and various sienites, granites, and greenstones, almost all porphyritic.
The Rock by the river's side presents the first solid strata that occur on the immediate banks of the river after passing the Forks. It is a round bluff hill about five hundred feet high, with a short obtuse-conical summit. A precipice three hundred feet high, washed by the river, is composed of strata of limestone, dipping N.W. by W. at an angle of 70°; but the strata in other parts of the hill have in appearance the saddle-formed arrangement. 127The limestone is of a blackish-gray colour, slightly crystalline structure, and much resembles the stone of the principal beds in the hills at the rapid and mouth of Bear Lake River. Its beds are from one to two feet thick, and much intersected by small veins of calc-spar. There are also some larger veins a foot and a half thick, which traverse the strata obliquely, having their sides lined with calc-spar, and their centres filled with transparent gypsum. 128
127
131
132I observed a small imbedded pebble of white sandstone in the gypsum. Some of the beds of limestone consist of angular distinct concretions. A small island lying off this rock, having its strata dipping south at an angle of 20°, presents a bed a foot thick, entirely composed of these angular concretions, covered by a thin-slaty limestone, and reposing on thicker beds, all of which are dark-coloured. No organic remains were observed.
A few miles below the "Rock by the river side," a very rugged ridge appears on the eastern bank. It has sharp craggy summits, and is about five or six hundred feet high. For nearly sixty miles below this place the river continues about eight hundred yards wide, bounded by banks chiefly of clay; but in some places of a clayey shale having a bluish colour. The banks are in many places one hundred and fifty feet high, with a beach beneath covered with boulders. A little above the site of the Old Fort Norman the river dilates, and is full of islands; and a short way inland, on the east side, stands Clark's Hill, which is visible from Fort Franklin, and is supposed to be near 1500 feet high. It is shaped somewhat like the amphibolic-granite mountain of Criffel in Galloway, and in its immediate neighbourhood there are some less lofty, but very rugged and precipitous hills, resembling in outline the ridges of limestone on Bear Lake River. From this place to the commencement of the lignite formation, already described, the banks of the Mackenzie are high and clayey.
MACKENZIE RIVER FROM BEAR LAKE RIVER TO THE NARROWS.
Below Bear Lake River the general course of the Mackenzie for eighty miles is about N.W. by W., when a remarkable rapid is produced by ledges of stone which cross its channel. The width of the river varies in this distance from one to three miles, but the water-course is narrowed by numerous islands, and the current continues strong. The Rocky Mountains are visible, running in a direction from S.E. to N.W. Judging merely by the eye, we did not estimate their altitude above four thousand feet, and I may remark, that the snow disappears from their summits early in the summer. A back view of the hill at the mouth of Bear Lake River is also obtained for upwards of twenty miles, but the ridge of which it forms a part curves inland, probably uniting, as was formerly remarked, with the one which crosses Bear Lake River near the middle of its course. The banks of the Mackenzie are in general from one hundred and twenty to one hundred and fifty feet high in this part, and there are occasional sections of them, but we had little leisure to examine their structure. In the voyage of 1826 we drifted down the stream night and day, landing only when necessary to cook our provisions; and in the following geological notices, as far as the passage of the river named the Narrows, I have done little more than describe the specimens collected by Captain Franklin, when he ascended the river by the tow-line in 1825. The few notes that the rapidity of our voyage permitted me to make, as to the direction of the strata, &c., were inserted in the book that was purloined by the Esquimaux at the mouth of the river.
About fifty miles below Bear Lake River there is an almost precipitous cliff of bituminous-shale, one hundred and twenty feet high, strongly resembling the cliffs which occur near the bases of the hill of Scented-Grass and Great Bear Mountain in Bear Lake already described[34], and at the mouth of the Clear Water River in lat. 56½°. In the two former localities the shale is in the neighbourhood of horizontal strata of limestone; and in the latter it actually reposes on the limestone, which extends in horizontal strata as far as Great Slave Lake, is connected with many salt springs, and possesses many of the characters ascribed to the zechstein formation. 133Captain Franklin observed the beach under the shale cliffs of the Mackenzie to be strewed not only with fragments of the shale, but also with much lignite, similar to that which occurs at the mouth of the Bear Lake River. Twelve or fourteen miles below these cliffs there is a reach seventeen or eighteen miles long, bounded by walls of sandstone in horizontal beds. 134
135 Specimens obtained by Captain Franklin at the upper end of the reach consist of fine-grained quartzose sandstone[35] of a gray colour, and having a clayey basis, resembling those which occur in the middle of Bear Lake River. At the commencement of the "Great Rapid of the Mackenzie" there is a hill on each side of the river, named by Captain Franklin the eastern[36] and Western mountains of the Rapid. The Rocky Mountains appear at no great distance from this place, running about N.W. by W., until lost to the sight; and as the Mackenzie for forty or fifty miles below, winds away to the northward, and, in some reaches, a little to the eastward, they are not again visible, until the river has made a bend to the westward, and emerges from the defile termed "the Narrows."
The "Eastern mountain of the rapid" seems to have a similar structure, with the "Hill by the River's side," the hill at the mouth of Bear Lake River, and the other limestone ridges which traverse this part of the country. 136From some highly inclined beds near its base I broke off specimens of a limestone, having an imperfectly crystalline structure, and a brown colour, which deepens into dull black on the surfaces of its natural seams. A piece of dark-gray, compact limestone, having the peculiar structure137
138 to which the name of "cone in cone" has been given, was found on the beach; also several pieces of chert, and some fragments 139
141of a trap-rock, consisting of pieces of greenstone, more or less iron-shot, cemented by calc-spar.
Immediately below the rapid there are horizontal layers of sandstone which form cliffs, and also the bed of the river. Captain Franklin obtained specimens of this stone, which do not differ from the sandstones above the rapid. 142
143
140 And amongst the debris of the cliff he found other specimens of the "cone in cone," such as it occurs in the clayey beds of the coal measures, and also some pieces of crystallized pyrites.
About forty miles below the rapid, the river flows through a narrow defile formed by the approach of two 144
144a
145
146
147
144blofty banks of limestone in highly-inclined strata, above which there is a dilatation of the river, bounded by the walls of sandstone, which have weathered, in many places, into pillars, castellated forms, caves, &c. The sandstone strata are horizontal, have slate-clay partings, and seams of a poor clay-iron stone, but do not differ in general appearance from the sandstone beds at the rapid, except that a marly stone containing corallines, and having the general colour and aspect of the sandstone beds, is associated with them at this place.
The very remarkable defile, below these sandstone beds, is designated "the second rapid" by Sir Alexander Mackenzie, and "the ramparts" by the traders, a name adopted by Captain Franklin. Mackenzie states it to be three hundred yards wide, three miles long, and to have fifty fathoms depth of water. If he is correct in his soundings, its bed is probably two hundred and fifty feet below the level of the sea. The walls of the defile rise from eighty to one hundred and fifty feet above the river, and the strata are inclined to the W.N.W., at an angle of seventy or eighty degrees. It is worthy of remark, that the course of the river through this chasm is E.N.E., and that just above the eastern mountain of the rapid it runs about W.S.W. through the sandstone strata, as if it had found natural rents by which to make its escape through the ridge of hills which cross its course here. Similar elbows occur in various parts of the River, and they may be almost always traced to some peculiarity in the disposition of the hills which traverse the country.
Captain Franklin gathered many specimens of the limestone strata of the Ramparts, which are specified in a note.[37] 148, 149Some of the beds at the upper part of the Ramparts consist of a granular foliated limestone, which was not noticed elsewhere on the banks of the river, but the greater part are of limestone, strongly resembling that which has been already described, as forming the ridges in this quarter. Most of the beds are impregnated wholly, or in patches, with bitumen. Some of these specimens contain corallines and terebratulæ; and at the lower end of the defile there are horizontal strata of limestone, covered by a thin layer of flinty slate.
Below the ramparts the river expands to the width of two miles, and for a reach or two its banks are less elevated. In lat. 66¾°, about thirty miles from the ramparts, there are cliffs which Captain Franklin in his notes, remarks, "run on an E. by S. course for four miles, are almost perpendicular, about one hundred and sixty feet high, and present the same castellated appearances that are exhibited by the sandstone above the defile of the "ramparts." 159, 160,
161, 162
163, 164,
165, 166
167, 168,
169, 170The cliffs[38] are, in fact, composed of sandstones similar, in general appearance, to those which occur higher up the river; but some of the beds contain the quartz in coarser grains, with little or no cement. The beds are horizontal, and repose on horizontal limestone,[39] from which Captain Franklin broke many specimens in 1825. We landed at this place in 1826 to see the junction of the two rocks, but the limestone was concealed by the high waters of the river. Captain Franklin's specimens are full of shells, many of which are identical with those of the flat limestone strata of the Athabasca River. 171 One bed appears to be almost entirely composed of a fine large species of terebratula, not yet described, but of which Mr. Sowerby has a specimen from the carboniferous limestone of Neho, in Norway. Some of the beds contain the shells in fragments; in others, the shells are very entire.
About forty miles below these sandstone walls the banks of the river are composed of marl-slate, which weathers so readily, that it forms shelving acclivities. 172In one reach the soft strata are cut by ravines into very regular forms, resembling piles of cannon shot in an arsenal, whence it was named Shot-reach.
The river makes a short turn to the north below Shot Reach, and a more considerable one to the westward, in passing the present site of Fort Good Hope. The banks in that neighbourhood are mostly of clay, but beds of sandstone occasionally show themselves. The Indians travel from Fort Good Hope nearly due north, reach the summit of a ridge of land on the first night, and from thence following the course of a small stream they are conducted to the river Inconnu, and on the evening of the 4th day they reach the shores of Esquimaux Lake. Its water is brackish, the tide flowing into it. The neck of land which the Indians cross from Fort Good Hope is termed "isthmus" on Arrowsmith's map, from Mackenzie's information; and its breadth, from the known rate at which the Indians are accustomed to travel, cannot exceed sixty miles. The ridge is named the Carreboeuf, or Rein-deer Hills, and runs to lat. 69°, forming a peninsula between the eastern channel of the Mackenzie and Esquimaux Lake.
A small stream flows into the Mackenzie some way below Fort Good Hope, on the banks of which, according to Sir Alexander Mackenzie, the Indians and Esquimaux collect flints. He describes these banks as composed of "a high, steep, and soft rock, variegated with red, green, and yellow hues; and that, from the continual dripping of the water, parts of it frequently fall, and break into small, stony flakes, like slate, but not so hard. Amongst these are found pieces of petroleum, which bears a resemblance to yellow wax, but is more pliable." The flint he speaks of is most probably flinty-slate; but I do not know what the yellow petroleum is, unless it be the variety of alum, named rock-butter, which was observed in other situations, forming thin layers in bituminous shale.
About twenty miles below Fort Good Hope there are some sandstone cliffs,[40] which Captain Franklin examined in 1825. 173, 174The sandstones are similar to those occurring higher up the river, but some of the beds contain small pieces of bituminous shale; and they are interstratified with thin layers of flinty-slate, and of flinty-state passing into bituminous shale. 175, 176The flinty-slate contains iron pyrites, and its layers are covered with a sulphureous efflorescence. Some of the beds pass into a slate-clay, which contains vegetable impressions, and some veins of clay-iron stone also appear in the cliff.
Sixty miles below Fort Good Hope the river turns to the northward, and makes a sharp elbow betwixt walls of sandstone eighty or ninety feet high, which continue for fifteen or178
179
180
181, 182
183 twenty miles. Captain Franklin named this passage of the river "The Narrows."[41] The sandstones of the Narrows lie in horizontal beds, and have generally a dark gray colour. They are parted by thin slaty beds of sandstone, containing small pieces apparently of bituminous coal, and some casts of vegetables. Most of the beds contain scales of mica, and some of them have nodules of indurated iron-shot clay which exhibit obscure impressions of shells. A bed of imperfectly crystalline limestone was seen by Captain Franklin underlying the sandstones.
MACKENZIE RIVER BELOW "THE NARROWS."
The Mackenzie, on emerging from the Narrows, separates into many branches, which flow to the sea through alluvial or diluvial deltas and islands. The Rocky Mountains are seen on the western bank of the river, forming the boundary of those low lands; and the lower, but decided ridge, of the Rein-deer Hills holds nearly a parallel course on the east bank. The estuary lying between these two ranges, opens to the N.W. by N. into the Arctic Sea. I have already mentioned the specimens of rocks obtained at the few points of the Rocky Mountains that were visited,[42] and therefore shall now speak only of the Rein-deer Hills. We did not approach them until we had passed for thirty miles down a branch of the river which winds through alluvial lands. At this place there are several conical hills about two hundred feet high, which appeared to consist of limestone. Specimens taken from some slightly-inclined beds near their bases, consisted of a fine-grained, dark, bluish-gray limestone. After passing these limestone rocks, the Rein-deer Hills were pretty uniform in appearance, having a steep acclivity with rounded summits. Their height, on the borders of the river, is about four hundred feet, but a mile or two inland they attain an elevation of perhaps two hundred feet more. Their sides are deeply covered with sand and clay, arising most probably from the disintegration of the subjacent rocks. 184, 185A section made by a torrent, showed the summit of one of the hills to be formed of gray slate-clay, its middle of friable gray sandstone much iron-shot, and its base of dark bluish-gray slaty clay. The sandstone predominates in some parts of the range, forming small cliffs, underneath which there are steep acclivities of sand. It contains nearly an equal quantity of black flinty slate, or lydian stone, and white quartz in its composition, and greatly resembles the friable sandstones of the lignite formation at the mouth of Bear Lake River. 186In some parts the soil has a red colour from the disintegration of a reddish-brown slate-clay. 187The summits of the hills that were visited were thinly coated with loose gravel, composed of smooth pebbles of lydian-stone, intermixed with some pieces of green felspar, white quartz, limestone, and chert. In some places almost all the pebbles were as large as a goose-egg, in others none of them exceeded the size of a hazel nut. The Rein-deer Mountains terminate in lat. 69°, having previously diminished in altitude to two hundred feet, and the eastern branch of the river turns round their northern extremity. White spruce trees grow at the base of these hills as far as lat. 68½°; north of which they become very stunted and straggling, and very soon disappear, none reaching to lat. 69°.
Sir Alexander Mackenzie, who, on his return from the sea, walked over these hills, says, "Though the country is so elevated, it is one continued morass, except on the summits of some barren hills. As I carried my hanger in my hand, I frequently examined if any part of the ground was in a state of thaw, but could never force the blade into it beyond the depth of six or eight inches. The face of the high land towards the river is, in some places, rocky, and in others a mixture of sand and stone, veined with a kind of red earth, with which the natives bedaub themselves." It was on the 14th of July that he made these observations. On the 5th of the same month, in a milder year, we found that the thaw had penetrated nearly a foot into the beds of clay at the base of the hills.
ALLUVIAL ISLANDS AT THE MOUTH OF THE MACKENZIE.
The space between the Rocky Mountains and Rein-deer Hills, ninety miles in length from lat. 67° 40' to 69° 10', and from fifteen to forty miles in width, is occupied by flat alluvial islands, which separate the various branches of the river. Most of these islands are partially or entirely flooded in the spring, and have their centres depressed and marshy, or occupied by a lake; whilst their borders are higher and well clothed by white spruce trees. The spring floods find their way, through openings in these higher banks, into the hollow centres of the islands, carrying with them a vast quantity of drift timber, which, being left there, becomes water-soaked, and, finally, firmly impacted in the mud. The young willows, which spring up rapidly, contribute much towards raising the borders of the stream, by intercepting the drift sand which the wind sweeps from the margin of the shallow ponds as they dry up in summer. The banks, being firmly frozen in spring, are enabled to resist the weight of the temporary floods which occur in that season, and before they are thawed the river has resumed its low summer level. The trees which grow on the islands terminate suddenly, in lat. 68° 40'.
I have already mentioned, that a large sheet of brackish water, named Esquimaux Lake, lies to the eastward of the Rein-deer Mountains, running to the southward, and approaching within sixty miles of the bend of Mackenzie's River at Fort Good Hope. This lake has a large outlet into Liverpool Bay, to the westward of Cape Bathurst, and there are many smaller openings betwixt that bay and Point Encounter, near the north end of the Rein-deer Hills, which are also supposed to form communications betwixt the lake and the sea. The whole coast-line from Cape Bathurst to the mouth of the Mackenzie, and the islands skirting it, as far as Garry and Sacred Islands, present a great similarity in outline and structure. They consist of extensive sandy flats, from which there arise, abruptly, hills of an obtuse conical form, from one to two hundred feet above the general level. Sandy shoals skirt the coast, and numerous inlets and basins of water divide the flat lands, and frequently produce escarpments of the hills, which show them to be composed of strata of sand of various colours, sometimes inclosing very large logs of drift timber. There is a coating of black vegetable earth, from six inches to a foot in thickness, covering these sandy hummocks, and some of the escarped sides appeared black, which was probably caused by soil washed from the summit.
It is possible that the whole of these eminences may, at some distant period, have been formed by the drifting of moveable sands. At present the highest floods reach only to their bases, their height being marked by a thick layer of drift timber. When the timber has been thrown up beyond the reach of ordinary floods, it is covered with sand, and, in process of time, with vegetable mould. The Elymus mollis, and some similar grasses with long fibrous roots, serve to prevent the sand-hills from drifting away again. Some of the islands, however, consist of mud or clay. Captain Franklin describes Garry's Island as presenting cliffs, two hundred feet high, of black mud, in which there were inclined beds of lignite. 188Specimens of this lignite have the same appearance with the fibrous wood-coal occurring in the formation at the mouth of Bear Lake River, and, like it, contain resin.189
190 Imbedded in the same bank, there were large masses of a dark-brown calc-tuff, full of cavities containing some greenish earthy substance. Some boulders of lydian stone strew the beach. The cliffs of Nicholson's Island also consisted of sand and mud, which, at the time of our visit, (July 16th,) had thawed to the depth of three feet. This island rises four hundred feet above the level of the sea, and is covered with a thin sward of grasses and bents.
SEA-COAST.—BITUMINOUS ALUM SHALE.
The main land to the east of Nicholson's Island, as far as Cape Bathurst, presents gently swelling hills, which attain the height of two hundred feet at the distance of two miles from the beach, and the ground is covered with a sward of moss and grasses. At Point Sir Peregrine Maitland there are cliffs forty-feet high of sand and slaty clay, and the ravines are lined with fragments of whitish compact limestone, exactly resembling that which occurs in Lakes Huron and Winipeg, and which was afterwards seen forming the promontory of Cape Parry, bearing E.N.E. from this place. The beach, on the south side of Harrowby Bay, not far from Point Maitland, was thickly strewed with fragments of dark red and of white sandstone, together with some blocks of the above-mentioned limestone, and a few boulders of sienite.
From Cape Bathurst the coast line has a S.E. direction, and is formed by precipitous cliffs, which gradually rise in height from thirty feet to six hundred. The beds composing these cliffs appear to be analogous to those of the alum-shale banks at Whitby, and similar to those which skirt the Scented-grass Hill and Great Bear Mountain, in Great Bear Lake. The Scented-grass Hill is distant from Cape Bathurst about three hundred miles, on a S.E. bearing, which corresponds, within a point, with the direction of the principal mountain chains in the country. 191There is evidently a striking similarity in the form of the ground plan of these two promontories. At the extremity of Cape Bathurst the cliffs consist of slaty-clay, which, when dry, has a light bluish-gray colour, a slightly greasy feel, and falls down in flakes. The rain-water had penetrated the cliff to the depth of three yards from the summit; and this portion was frozen, on the 17th July, into an icy wall, which crumbled down as it thawed. On proceeding a little further along the coast, some beds were observed that possessed, when newly exposed to the air, tenacity enough to be denominated stone, but which, under the action of water, speedily softened into a tenacious bluish-clay.
At Point Traill we were attracted by the variegated colours of the cliff, and on landing found that they proceeded from192
193
197
198
199 clays baked by the heat of a bed of bituminous-alum-shale which had been on fire. Some parts of the earth were still warm. The shale is of a brown colour and thin slaty structure, with an earthy fracture. It contains many interspersed crystals of selenite; between its lamina there is much powdery alum, mixed with sulphur, and it is traversed by veins of brown selenite, in slender prismatic crystals. The bed was much broken down, and hid by the debris of the bank, but parts in it was200
194
195
196 several yards thick, and contained layers of the wax-coloured variety of alum, named Rock-butter. The shale is covered by a bed of stone, chiefly composed of oval distinct concretions of a poor calcareous clay-iron stone. These concretions have a straight cleavage in the direction of their short axis, and are often coated by fibrous calc-sinter and calcedony. The upper part of the cliff is clay and sand passing into a loosely cohering sandstone. The strata are horizontal, except in the neighbourhood of ravines, or of consumed shale, when they are often highly inclined, apparently from partial subsidence. The debris of the cliff form declivities, having an inclination of from fifty to eighty degrees, and the burnt clays variously coloured, yellow, white, and deep red, give it much the appearance of the rubbish of a brick-field. The view of the interior, from the summit of the cliff, presents a surface slightly varied by eminences, which swell gently to the height of fifty or sixty feet above the general level. The soil is clayey, with a very scanty vegetation, and there are many small lakes in the country.
Ten miles further on, the alum-shale forms a cliff two hundred feet high, and presents layers of the Rock-butter about two inches thick, with many crystals of selenite on the201 surfaces of the slates. The summit of the cliff consists of a bed of marly gravel two yards thick, which is composed of pebbles of granite, sienite, quartz, lydian-stone, and compact limestone, all coated by a white powdery marl. The dip of the strata at this place is slightly to the northward.
A few miles to the south-east of Wilmot Horton River the cliffs are six hundred feet high, and present acclivities having an inclination of from thirty to sixty degrees, formed of weathered slate-clay. Some beds of alum-shale are visible at the foot of these cliffs, containing much sulphate of alumina and masses of baked clay.
Two miles further along the coast the shaly strata were on fire, giving out smoke, and beyond this the cliffs become much broken but less precipitous, having fallen down in consequence of the consumption of the combustible strata. These ruined cliffs gradually terminated in green and sloping banks, whose summit was from one to two miles inland, and about six hundred feet above the sea level. Considerable tracts of level ground occurred occasionally betwixt these banks and the beach. Wherever the ground was cut by ravines, beds of slate-clay were exposed. On reaching the bottom of Franklin Bay, we observed the higher grounds keeping an E.S.E. direction until lost to the view, becoming, however, somewhat peaked in the outline.
SEA COAST.—LIMESTONE.
Parry's Peninsula, where it joins the mainland, is very low, consisting mostly of gravel and sand, and is there greatly indented by shallow bays, but it gradually increases in height towards Cape Parry. The bays and inlets are separated from the sea by beaches composed of rolled pieces of compact limestone; and which, although they are in places only a few yards across, are several miles in length. The northern part of Parry's Peninsula belongs entirely to a formation which appears from the mineralogical characters of the stone composing the great mass of the strata, and the organic remains observed in it, to be identical with the limestone formations of Lakes Winipeg and Huron.
202
204On the north side of Sellwood Bay, in lat. 69° 42', cliffs about twenty feet high are composed of a fine-grained[43] brownish dolomite, in angular distinct concretions, and containing corallines and veins of calc-spar. 203In the same neighbourhood there is a bed of grayish-black compact luculite with drusses of calc-spar, very similar to the limestone which occurs in highly inclined strata at the "Rock by the River Side," on the Mackenzie, and in horizontal strata in an island near that rock, where it forms angular concretions.
After passing Sellwood Bay, the north and east shores of Cape Parry, and the islands skirting them, present magnificent cliffs of limestone, which, from the weathering action of the waves of the sea, assume curious architectural forms. Many of the insulated rocks are perforated. Between the bold projecting cliffs of limestone there are narrow shelving beaches, formed of its debris, that afford access to the interior. The strata have generally a slight dip to the northward, and the most common Rock is a yellowish-gray dolomite which has a very compact structure, but presents some shining facets of disseminated calc-spar. This stone, which is not to be distinguished by its mineralogical characters from the prevailing limestone of Lake Winipeg, and at the passage of La cloche in Lake Huron, forms beds six or eight feet thick, and is frequently interstratified with a cellular limestone, approaching to chert in hardness, and exhibiting the characters of rauchwacke. In some parts, the rauchwacke is the predominating rock, and has its cells beautifully powdered with crystals of quartz or of calc-spar, and contains layers of chert of a milky colour. The chert has sometimes the appearance of calcedony, and is finely striped.
208, 209The extremity of Cape Parry is a hill about seven hundred feet high, in which beds of brownish dolomite, impregnated with silica, are interstratified with a thin-slaty, gray limestone, having a compact structure.[44] The vegetation is very scanty, and there are some spots covered with fragments of dolomite, on which there is not the vestige even of a lichen. Many large boulders of greenstone were thrown upon the N.W. point of Cape Parry. The islands in Darnley Bay, between Capes Parry and Lyon, are composed of limestone.
SEA-COAST.—FORMATION OF SLATE-CLAY, SANDSTONE, AND LIMESTONE, WITH TRAP-ROCKS.
From Cape Lyon to Point Tinney, the rocks forming the coast-line are slate-clay, limestone, greenstone, sandstone, and calcareous puddingstone.
214Near the extremity of Cape Lyon the slate-clay predominates, occurring in straight, thin, bluish-gray layers, which are interspersed with detached scales of mica. 215It sometimes forms thicker slates, that are impregnated with iron, and occurs alone, or interstratified in thin beds with a reddish, small-grained limestone. The strata, in general, dip slightly to the N.E., and form gently-swelling grounds, which at the distance of about fifteen miles to the southward terminate in hills, named the Melville Range. These hills are apparently connected with those which skirt the coast to the westward of Parry's Peninsula, have rather a soft outline, and do not appear to attain an altitude of more than seven or eight hundred feet above the sea. Ridges of naked trap-rocks, which traverse the lower country betwixt the Melville hills and the extremity of the Cape, rise abruptly to the height of one hundred or one hundred and fifty feet, and have, in general, an E.N.E. direction. When these trap ridges reach the coast, they form precipices which frequently have a columnar structure, and the nearly horizontal strata of slate-clay are generally seen underlying the precipices. In many places the softer clay strata are worn considerably away, and the columns of greenstone hang over the beach. Columns of this description occur at the north-eastern extremity of the Cape, and the slate-clay is not altered at its point of contact with the greenstone. The soil in this neighbourhood is clayey, and some small streams have pretty lofty and steep clayey banks; the shaly strata appearing only at their base. A better sward of grasses and carices exists at Cape Lyon, than is usual on those shores. Many boulders of greenstone and large fragments of red sandstone strew the beach.
At Point Pearce, four or five miles to the eastward of Cape Lyon, a reddish, small-grained limestone forms perpendicular cliffs two hundred feet high, in which a remarkable cavern occurs. Near these cliffs the slate-clay and reddish limestone are interstratified, and form a bold rocky point, in which the strata dip to the N.E. at an angle of 20°. The coast line becomes lower to the eastward, and at Point Keats a fine-grained, flesh-coloured sandstone occurs. This sandstone is quartzose, does not possess much tenacity, and is without any apparent basis.
At Point Deas Thompson the limestone re-appears, having reddish-brown and flesh-red colours, and a splintery fracture. There are some beautiful Gothic arches formed in the cliffs there by the weathering of the strata.
Five miles farther along the coast, near Roscoe River, the same kind of limestone forms cliffs twenty-five feet high, and is covered by thin layers of soft slate-clay. On the top of these cliffs we observed a considerable quantity of drift-timber and some hummocks of gravel. The spring tides do not rise above two feet. The Melville Range approaches within three miles of the coast there, and presents a few short conical summits, although the hills composing it are mostly round-backed.
At Point De Witt Clinton, a compact blackish-blue limestone, traversed by veins of calc-spar, forms a bed thirty feet thick,217
218
219 which reposes on thin layers of a soft, compact, light, bluish-gray limestone or marl. The cliffs at this place are altogether about seventy feet high, but their bases were concealed by accumulations of ice. Veins filled with compact and fibrous gypsum traverse the upper limestone. Naked and barren ridges of greenstone, much iron-shot, cross the country here, in the same manner as at Cape Lyon. The soil consists of gravel and clay; the former mostly composed of whitish magnesian limestone; and the vegetation is very scanty.
At Point Tinney, in lat. 69° 20', cliffs of a calcareous puddingstone, about forty feet high, extend for a mile along the coast. The basis, in most of the beds, is calc-spar; but in some small layers it is calcareous sand. The imbedded pebbles are smooth, vary in magnitude, from the size of a pea to that of a man's hand, and are mostly or entirely of chert, which approaches to calcedony, and, when striped, to agate in its characters. Perhaps, much of the gravel which covers the country is derived from the destruction of this conglomerate rock.
SEA COAST.—LIMESTONE.
From Point Clifton to Cape Hearne, the whole coast consists of a formation of limestone precisely similar to that which occurs on Lake Winipeg and Parry's Peninsula.
Dolomite, the prevailing rock in this formation, is generally in thin layers, and has a light smoke-gray colour, varying occasionally to yellowish gray, and buff. Its structure is compact, with little lustre, except from facets of disseminated calc-spar. It sometimes passes into milk-white chert, which forms beds. In some places the dolomite alternates with cellular limestone, which is generally much impregnated with quartz, and has its cavities powdered with crystals of that mineral. No organic remains were observed in the strata, but fragments, evidently derived from some beds of the formation, contained orthoceratites, like those of Lake Huron. The strata, though nearly horizontal, appear to crop out towards the north and east, forming precipices about ten feet high, facing in that direction, and running like a wall across the country. In many places, however, and particularly at Cape Krusenstern, the strata terminate in magnificent cliffs upwards of two hundred feet high, the country in the interior remaining level. Mount Barrow is a small hill of limestone, of a remarkable form, being a natural fortification surrounded by a moat. The coast line is indented by shallow bays, and skirted by rocks and islands.
In the whole country occupied by this formation, the ground is covered with slaty fragments, sometimes to the depth of three feet or more. These slates appear to have been detached from the strata they cover, by the freezing of the water, which insinuates itself betwixt their layers. At Cape Bexley, the fragments of dolomite cover the ground to the exclusion of all other soil; and in a walk of several miles, I did not see the vestige of a vegetable, except a small green scum upon some stones that formed the lining of a pond which had dried up. In this neighbourhood there are a number of straight furrows a foot deep, as if a plough had been drawn through the loose fragments. After many conjectures as to the cause of this phenomenon, I ascertained that the furrows had their origin in fissures of the strata lying underneath.
At the commencement of this formation between Point Tinney and Point Clifton, the coast is low, and a stream of considerable magnitude, named Croker River, together with many rivulets, flow into the sea. Its termination to the southward of Cape Hearne is also marked by a low coast line, which is bounded by the bold rocky hills of Cape Kendall.
FORMATION SIMILAR TO THAT AT CAPE LYON.
The beach between Cape Hearne and Cape Kendall is in some places composed of slate-clay, and of a clay resembling wacke. Many large boulders of greenstone occur there. Cape Kendall is a projecting rocky point, about five or six hundred feet high, and nearly precipitous on three sides, which are washed by the sea. On the north, its rocks consist entirely of greenstone, but on the south side of the Cape the greenstone in lofty columns reposes on thin-slaty beds of fine-grained, bluish-gray limestone. Back's Inlet presents on each side a succession of lofty precipitous headlands, which have the shape termed, by seamen, "the gunner's quoin." Most of the islands and points near the mouth of the Coppermine have this form, and are composed of trap rocks. 220One of Cowper's islands on which we landed consists of beds of greenstone cropping out like the steps of a stair.
A low ridge of greenstone exists at the mouth of the Coppermine river, and from thence to Bloody-fall, a distance of ten miles, the country is nearly level, with the exception of some low ridges of trap which run through it. The channel of the river is sunk about one hundred and fifty feet below the surrounding country, and is bounded by cliffs of yellowish white sand, and sometimes of clay, from beneath which, beds of greenstone occasionally crop out.
At Bloody-fall, a round-backed ridge of land, seven or eight hundred feet high, crosses the country. It has a gentle ascent on the north, but is steep towards the south. The river at the fall makes its way through a narrow gap, whose nearly precipitous sides consist of tenacious clay, the bed and immediate borders of the stream being formed of greenstone.[45] From thence to the Copper Mountains, gently undulated plains occur, intersected in various parts by precipitous ridges of trap rocks, and the river flows in a narrow chasm, sunk about one hundred feet below their level. A few miles above Bloody-fall, strata of light gray clay-slate, dipping to the north-east, at an angle of 20°, support some greenstone cliffs on the banks of the river. 222
223
224From this place to the Copper Mountains the rocks observed in the ravines were a dark reddish-brown, felspathose sandstone, and gray slate-clay, in horizontal strata, with greenstone rising in ridges. The soil is sandy, and in many places clayey, with a pretty close grassy sward. Straggling spruce trees begin to skirt the banks of the river about eighteen or twenty miles from the sea.
COPPER MOUNTAINS.
The Copper Mountains rise perhaps eight or nine hundred feet above the bed of the river, and at a distance, present a somewhat soft outline, but on a nearer view they appear to be composed of ridges which have a direction from W.N.W. to E.S.E. Many of the ridges have precipitous sides, and their summits, which are uneven and stony, do not rise more than two hundred, or two hundred and fifty feet above the vallies, which are generally swampy and full of small lakes. The only rocks noticed when we crossed these hills on the late journey, were clay-slate, greenstone, and dark red sandstone, sometimes containing white calcareous concretions, resembling an amygdaloidal rock. On our first journey down the Coppermine River, we visited a valley where the Indians had been accustomed to look for native copper, and we found there many loose fragments of a trap rock, containing native copper, green malachite, copper glance, and iron-shot copper green; also trap containing greenish-gray prehnite with disseminated native copper, which, in some specimens was crystallized in rhomboidal dodecahedrons. Tabular fragments of prehnite, associated with calc-spar and native copper, were also picked up, evidently portions of a vein, but we did not discover the vein in its original repository. The trap-rock, whose fragments strewed the valley, consists of felspar, deeply coloured by hornblende. A few clumps of white spruce trees occur in the vallies of the Copper Mountains, but the country is in general naked. The Coppermine River makes a remarkable bend round the end of these hills.
After quitting the Copper Mountains, and passing a valley occupied by a chain of small lakes in lat. 67° 10', long. 116° 45', we travelled over a formation whose prevailing rocks are spotted sandstone and conglomerate, and which forms the height of land betwixt Bear Lake and the Coppermine River. The ascent to this height from the eastward is gradual, but the descent towards Bear Lake is more rapid. The country is broken and hilly, though the height of the hills above the sea is perhaps inferior to that of the Copper Mountains. The vallies through which the small streams that water the country flow, are narrow and deep, resembling ravines, and their sides are clayey. The ground is strewed with gravel.
The sandstone has very generally a purplish colour, with gray spots of various magnitudes. It is fine grained, hard, has a somewhat vitreous lustre and contains little or no disseminated mica.
The conglomerate consists of oval pebbles of white quartz, sometimes of very considerable magnitude, imbedded in an iron-shot cement. Many of the pebbles appear as if they had been broken and firmly re-united again. The conglomerate passes into a coarse sandstone.
Porphyry and granite form hills amongst the sandstone strata.
The porphyry has a compact basis, like hornstone, of a dull brown colour, which contains imbedded crystals of felspar and quartz, and occasionally of augite. It forms some dome-shaped and short conical hills.
The granite is disposed in oblong ridges, with small mural precipices. It has, generally, a flesh-red colour, and contains some specks of augite, but little or no mica. The granite and porphyry were observed only on the east side of the height of land, the brow of which, and its whole western declivity, is formed of sandstone. Boulders of granite and porphyry, precisely similar to the varieties which occur in situ on the height of land, are common on the beach at Fort Franklin, and on the banks of the Mackenzie above Bear Lake.
To the westward of the height of land, the country on the banks of Dease River is more level, and few rocks in situ were seen, until within five or six miles of Bear Lake, where the stream flows through a chasm, whose sides are composed of a soft, fine-grained red sandstone, like that which occurs in the vale of Dumfries, in Scotland. Several ravines here have their sides composed of fine sand, inclosing fragments of soft sandstone.
About three miles from the mouth of Dease River we came to a limestone formation, which has been already noticed in the account of the geological structure of the shores of Great Bear Lake.
EASTERN CHAIN OF PRIMITIVE ROCKS.
The preceding part of the paper describing the rock formations which were noticed on the route of the expedition from Great Slave Lake down the Mackenzie along the shores of the Arctic Sea, the Coppermine, Great Bear Lake, and Great Bear River, being a distance of three thousand miles, I shall, by way of supplement, mention very briefly some of the more southern deposits.
The first I have to speak of is the chain of primitive rocks to which I have alluded in page 289, as extending for a very great distance in a north-west direction, and inclining in the northern parts slightly towards the Rocky Mountain Chain. Dr. Bigsby, in his account of the geology of Lake Huron says, that "The primitive rocks on the northern shores of that lake are part of a vast chain, of which the southern portion, extending probably uninterruptedly from the north and east of Lake Winipeg, passes thence along the northern shores of Lakes Superior, Huron, and Simcoe, and after forming the granitic barrier of the Thousand Isles, at the outlet of Lake Ontario, spreads itself largely throughout the state of New York, and there joins with the Alleghanies, and their southern continuations." It is not my intention to say any thing further of the rocks in the districts of which Dr. Bigsby speaks, although in travelling from the United States to Lake Winipeg the expedition passed over them. That zealous geologist has already given, in various publications, many interesting and accurate details of the formations on the borders of the great lakes; an account of those which lie some degrees farther to the north is inserted in the second volume of the Geological Transactions,—and there are some notices of them in the Appendix to the narrative of Captain Franklin's First Journey. My object at present is, merely to trace the western boundary of the primitive rocks in their course through the more northerly parts of the American continent.
I have already quoted Sir Alexander Mackenzie's original and important remark, of the principal lakes in those quarters being interposed betwixt the primitive rocks and the secondary strata, lying to the westward of them—Lake Winipeg is an instance in point. It is a long, narrow lake, and is bounded throughout on its east side by primitive rocks, mostly granitic, whilst its more indented western shore is formed of horizontal limestone strata. The western boundary of the primitive rocks, extending on this lake about two hundred and eighty miles, has nearly a north-north-west direction. From Norway Point, at the north end of the lake, to Isle à la Crosse, a distance of four hundred and twenty miles in a straight line, the boundary has a west-north-west direction. For two hundred and forty miles from Isle à la Crosse to Athabasca Lake, the course of the primitive rocks is unknown to me; but from Athabasca Lake to M'Tavish's Bay, in Great Bear Lake, a distance of five hundred miles, their western edge runs about north-west-by-west, and is marked by the Slave River, a deep inlet on the north side of Great Slave Lake, and a chain of rivers and lakes, (including great Marten Lake,) which discharge themselves into that inlet.
Captain Franklin on his voyage crossed this primitive chain nearly at right angles to its line of direction, in proceeding from Hudson's Bay to Lake Winipeg—it was there two hundred and twenty miles wide.
The hills composing the chain are of small elevation, none of them rising much above the surrounding country. They have mostly rounded summits, and they do not form continuous ridges; but are detached from each other, by vallies of various breadth, though generally narrow, and very seldom level. The sides of the hills are steep, often precipitous. When the vallies are of considerable extent, they are almost invariably occupied by a lake, the proportion of water in this primitive district being very great; from the top of the highest hill on the Hill River, which has not a greater altitude than six hundred feet, thirty-six lakes are said to be visible. The small elevation of the chain may be inferred from an examination of the map, which shows that it is crossed by several rivers, that rise in the Rocky Mountains, the most considerable of which are the Churchill and the Saskatchewan, or Nelson River. These great streams have, for many hundred miles from their origin, the ordinary appearance of rivers, in being bounded by continuous parallel banks; but on entering the primitive district, they present chains of lake-like dilatations, which are full of islands, and have a very irregular outline. Many of the numerous arms of these expansions wind for miles through the neighbouring country, and the whole district bears a striking resemblance, in the manner in which it is intersected by water, to the coast of Norway and the adjoining part of Sweden. The successive dilatations of the rivers have scarcely any current, but are connected to each other by one or more straits, in which the water-course is more or less obstructed by rocks, and the stream is very turbulent and rapid. The most prevalent rock in the chain is gneiss; but there is also granite and mica-slate, together with numerous beds of amphibolic rocks.
LIMESTONE OF LAKE WINIPEG.
To the westward of the chain of primitive rocks, through a great part, if not through the whole of its course, lies an extensive horizontal deposit of limestone.
Dr. Bigsby, in the Geological Transactions, has described, in detail, the limestone of Lake Huron, and is disposed to refer "the cavernous and brecciated limestone of Michilimackinac to the magnesian breccia, which is in England connected with the red marl;" whilst the limestones of St. Joseph, and the northern isles, he considers as more resembling the well-known formation of Dudley, in Staffordshire. The limestone of Thessalon Isle, in which there occurs the remarkable species of orthoceratite which he has figured, he describes as decidedly magnesian. I observed this orthoceratite in the limestone strata of one of the isles forming the passage of La Cloche in Lake Huron. The limestone deposits of Lake Winipeg and Cape Parry exactly resemble that of La Cloche in mineralogical characters, and in containing the same orthoceratite which was also found by Captains Parry and Lyon at Igloolik.
The colour of the limestone of Lake Winipeg is very generally yellowish-white, passing into buff, on the one hand, and into ash-gray on the other. A reddish tinge is also occasionally observed. Much of it has a flat fracture, with little or no lustre, and a fine-grained arenacious structure. A great portion of it, however, is compact, and has a flat conchoidal and slightly splintery fracture. This variety passes into a beautiful china-like chert. 1001, 1014Many of the beds are full of long, narrow vesicular cavities, which are lined sometimes with calc-spar, but more frequently with minute crystals of quartz. The beds of this formation seldom exceed a foot in thickness, and are often very thin and slaty. The arenacious and cherty varieties frequently occur in the same bed; sometimes they form distinct beds. The softer kinds weather readily into a white marl, which is used by the residents to whitewash their houses. Wherever extensive surfaces of the strata were exposed, as in the channels of rivers, they were observed to be traversed by rents crossing each other at various angles. The larger rents, which were sometimes two yards or more in width, were however, generally parallel to each other for a considerable distance.
Professor Jameson enumerates terebratulæ, orthoceratites, encrinites, caryophyllitæ, and lingulæ, as the organic remains in the specimens brought home by Captain Franklin on his first expedition. Mr. Stokes and Mr. James De Carle Sowerby have examined those which we procured on the last expedition, and found amongst them terebratulites, spirifers, maclurites, and corallines. The maclurites belonging to the same species, with specimens from Lakes Erie and Huron, and also from Igloolik, are perhaps referrible to the Maclurea magna of Le Sueur. 1015
1019 Sowerby determined a shell, occurring in great abundance in the strata at Cumberland-house, about one hundred and twenty miles to the westward of Lake Winipeg, to be the Pentamerus Aylesfordii.
The extent to the westward of the limestone deposit of Lake Winipeg is not well known to me; but I have traced it as far up the Saskatchewan as Carlton House, and its breadth there is at least two hundred and eighty miles. For about one hundred miles below Carlton House, the river Saskatchewan flows betwixt banks from one to two hundred feet in height, consisting of clay or sand, and the beds of limestone are exposed in very few places. The plains in the neighbourhood of Carlton abound in small lakes, some of which are salt. The country which the Saskatchewan waters for one hundred and ninety miles before it enters Lake Winipeg, is of a different kind. It is still more flat than that about Carlton, and is so little raised above the level of the river, that in the spring-floods the whole is inundated, and in several places the river sends off branches which reunite with it after a course of many miles. In this quarter the soil is generally thin, and the limestone strata are almost every where extensively exposed. To the southward of Cumberland House, the Basquiau Hill has considerable elevation. I had not an opportunity of visiting it; but in the flat limestone strata, near its foot, there are salt springs, from which the Indians sometimes procure a considerable quantity of salt by boiling; and there are several sulphureous springs within the formation.
I observed no beds of conglomerate in it, and no sandstone associated with it; but the extensive plains which lie betwixt Carlton House and the Rocky Mountains are sandy, and beds of sandstone are said to be visible in some of the ravines.
The line of contact of the limestone with the primitive rocks of Lake Winipeg, is covered with water; but at the Dog's-Head, and near the north end of Beaver Lake, they are exposed within less than a mile of each other. To the southward of the Dog's-Head in Lake Winipeg, and in a few other quarters, some schistose rocks, belonging to the transition series, are interposed between the two formations.
Before quitting the formations of Lake Winipeg, I may remark, that the height of that lake above the sea is perhaps equal to that of Lake Superior, which is eight hundred feet.
LIMESTONE OF THE ELK AND SLAVE RIVERS.
The next formation I have to mention is one which appears to possess most of the characters ascribed by German geologists to the zechstein. It extends from the north side of the Methy carrying-place down the Clearwater, Elk, and Slave Rivers, and along the south shore of Great Slave Lake to the efflux of the Mackenzie. The line I have traced was the route of the expedition, and is also very nearly that of the eastern boundary of the limestone. Primitive rocks occur in Lake Mammawee, Athabasca Lake, and on the Stony River; and on several parts of the Slave River they are separated from the limestone only by the breadth of the stream. On Great Slave Lake, the Stony Island, on the north-east side of the mouth of Slave River, is composed of granite, whilst the limestone strata are exposed at Fort Resolution on the south-west side.
The limestone in this extensive tract is commonly in thin and nearly horizontal beds, and much of it exactly resembles in mineralogical characters the dolomite and chert of Lake1027, 1028 Winipeg. It is interstratified with thin beds of soft white marl; and in a few places with a marly sandstone. Extensive beds of stinkstone also occur, and many beds of limestone containing fluid bitumen in cavities. The bitumen is in such quantity, in some quarters, as to flow in streams from fissures in the rock; and in an extensive district, around Pierre au Calumet on the Elk River, slaggy mineral pitch fills the crevices in the soil, and may be collected in large quantities by digging a well.
A calcareous breccia also exists in various places, particularly on the Slave River. Springs depositing from their waters sulphur, and sulphate of lime, slightly mixed with sulphate of magnesia, muriate of soda, and iron, are common and copious. A few miles to the westward of the Slave River, there is a ridge of hills several miles long, and about two hundred feet high, having several beds of compact, grayish gypsum exposed on its sides. From the base of this hill there issue seven or eight very copious, and many smaller springs, whose waters deposit a great quantity of very fine muriate of soda by spontaneous evaporation. The collected rivulets from these springs form a stream which is, at its junction with the Slave River, sixty yards wide and eight or ten feet deep.
1020 to 1026The organic remains, in this deposit, according a list kindly furnished by Mr. Sowerby, consist of spirifers, 1029 to 1032one of which is the spirifer acuta; several new terebratulæ, of which one resembles the T. resupinata, a cirrus, some crinoidal remains, and corals.
At the union of Clearwater and Elk Rivers, the limestone beds are covered to the depth of one hundred and fifty feet with bituminous shale.
I have stated, that on Slave River this limestone formation succeeds immediately to primitive rocks, but I am not acquainted with the rocks that lie to the eastward of it on the Elk River. The traders report that there are extensive deposits of sandstone on the eastern arm of the Athabasca Lake, and, perhaps, these sandstones extend nearly to Clearwater River. Sand covers the limestone on that river to the depth of eight or nine hundred feet, and the fragments of sandstone in it are large, numerous, and not worn.
The quantity of gypsum in immediate connection with extremely copious and rich salt springs, and the great abundance of petroleum in this formation, together with the arenacious, soft, marly, and brecciated beds interstratified with the dolomite, and above all, the circumstance of the latter being by far the most common and extensive rock in the deposit, led me to think that the limestone of the Elk and Slave Rivers was equivalent to the zechstein of the continental geologists. My opinion, however, on this subject is, from a total want of practical acquaintance with the European rock formations, of little weight; and several eminent geologists are, after an examination of the organic remains and mineralogical characters of the specimens brought home, inclined to consider the formation as analogous to the carboniferous or mountain-limestone of England.
As to the limestone formation of Lake Winipeg, I have no doubt of its identity with that occurring in the islands at the passage of La Cloche, in Lake Huron, and also with that at Cape Parry and at Cape Krusenstern, on the coast of the Arctic Sea. It is probable, also, that these four deposits belong to the same epoch with the limestone of Elk and Slave Rivers, although they differ in containing little or no petroleum. It is proper to mention, however adverse it may be to the opinion I have ventured to hint at above, of these extensive horizontal deposits of limestone being referable to the zechstein, that the limestone of Lake Huron is generally considered as belonging to the mountain-limestone; and Professor Jameson, from a review of the organic remains occurring in the Lake Winipeg deposit, considered that it also belonged to that formation. The formation of Cape Lyon may be, with less danger of a mistake, referred to the transition or mountain-limestone.
THE END.
