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.