MISSISSIPPI.

(Text-figure [22].)

The geological history of the lower part of the Mississippi Valley during Quaternary times appears to be particularly difficult to understand and at present is far from being unraveled. It is easy to see that such a region will offer great difficulties. Here debouches into the ocean a majestic river which drains not only the glaciated portions of the United States from western New York to northwestern Montana, but the larger part of the region south of this from the Blue Ridge to the Rocky Mountains, and brings down every year enormous quantities of sand and silt, which are dropped partly on its flood-plain, but mostly near its mouth. Through the ages during which this has been proceeding, this river has been ever changing its bed, sometimes eroding away one bank, sometimes the opposite one; so that its flood-plain is, in most places below the mouth of the Ohio, many miles wide, varying, according to Russell (“Rivers of North America,” 1898, p. 267) from 5 miles to 80 miles in width. During the Quaternary there have been also elevations and subsidences of the bed at least from Cairo northward, as a result of which at one epoch the current was hastened and the valley cut out deeper; at another the current was checked, the channel clogged up, and the river forced to seek a new channel or even new temporary or permanent outlets to the Gulf (E. A. Smith, Geol. Surv. Alabama, 1894, pp. 30–34).

To get a correct idea of the Pleistocene geology of the lower Mississippi region, one must understand the situation at the beginning of this epoch. I. C. Russell, on page 267 of his work just quoted, calls attention to the differences displayed by the valley of the river within the glaciated region and that south of it. South of the mouth of Ohio River the wide flood-plain of the Mississippi lies from 300 to 500 feet below the general level of the bordering uplands. He states further that the hard rock bottom of the valley is only imperfectly known, but that the records of wells and borings show that an ancient valley has been filled with alluvium to a depth of at least 100 or 200 feet in its northern part and to an increasing depth southward. If to this thickness, given by Russell, we add the depth, 300 to 500 feet, which the flood-plain occupies below the bordering uplands, we get a measure of the depth of the great trench which once existed where now lies the flood-plain of Mississippi River. In his paper on the underground waters of southern Louisiana (Bull. 1, Louisiana Geol. Surv., 1905, p. 42, plate II) Harris presents the record of the Fabacher well, which was bored at New Orleans. At a depth of about 1,200 feet fossil remains were brought up which appeared to be of Pleistocene age. It is evident from these facts, as in the case of those obtained from the rivers of Texas, that at about the beginning of the Pleistocene, or more probably during the time of the so-called Lafayette, at the close of the Pliocene, the country east of the Rocky Mountains, at least, stood for a long time at a much higher level than at present and that, as a result of this elevation, there was an enormous general erosion of the face of the country and a great widening and deepening of the river valleys. This time of elevation was quite certainly followed by a prolonged period of depression, during which these canyon-like trenches and their tributaries, up to their last ramifications, were nearly completely refilled. This refilling must have occurred during the early stages of the Pleistocene, for in the materials are buried the bones of early Pleistocene animals. As quoted below, in considering the geology at Natchez, Chamberlin and Salisbury state that since the Natchez formation, 200 feet thick, was laid down, the trench of the Mississippi, 60 miles wide, has been excavated. One might change this expression and say that it had been re-excavated, but not to its original depth.

When we reflect that the greater part of the sediments which, during the Pleistocene epoch, were deposited at the mouth of Mississippi River and on its flood-plain from Kentucky southward, were certainly derived from the glaciated portions of its great valley, and that those regions were alternately affected by the events of five glacial and four interglacial epochs, we must conclude that corresponding deposits or phenomena of some kind exist throughout the valley. The matter is, however, so complicated that many years must elapse before a satisfactory solution will have been reached.

In his Report on the Geology and Agriculture of the State of Mississippi, 1860 (1863–65), the geologist E. W. Hilgard, on pages 5 to 46, described under the name of Orange sand a deposit which characterizes the greater part of the surface of that State. He referred this to the Quaternary and regarded it as being the southern equivalent of the northern drift. This formation is now believed to belong mostly at least to the Pliocene. Besides the Orange sand, Hilgard (op. cit., pp. 194–201) referred other formations to the Quaternary. These in order would be as follows, the latest above:

5. Modern alluvium. 4. Second bottom, or Hommock deposits. 3. Yellow loam deposits. 2. The Bluff formation. 1. Orange sand.

The Bluff formations were described as occupying a narrow belt along the borders of the Mississippi bottom in northern Mississippi and along the river itself in the southern part of the State. He stated that the fossils belonged to terrestrial species, and quoted Leidy’s list of vertebrates, already mentioned, remarking that the blue clay which furnished them was said to belong to the Bluff formation. He reported that the snails found in the Bluff formation seemed all to belong to living species. The yellow loams occupied a large part of the surface of the State, overlying the Orange sand and forming a great part of the soils of the State. The succeeding formations were found along many of the rivers.

In 1869 (Amer. Jour. Sci., vol. XLVII, pp. 331–346), Hilgard reported the results of a geological reconnaissance of Louisiana. In this he proposed the name Port Hudson group for extensive deposits of clays which were especially well displayed at Port Hudson. This formation was further described by Hilgard in 1872 (Smithson. Contrib. Knowl., vol. XXIII, No. 248, p. 5). Two geological sections taken near Port Hudson were presented, one of which is here reproduced.

Section midway between Port Hudson and Fontana.
6.Yellow loam, sandy below8–10
5.White and yellow hardpan18
Orange and yellow sand, sometimes ferruginous sandstone, irregularly stratified8–15
4.Heavy greenish or bluish clay7
3.White indurate silt, or hardpan18
2.Heavy green clay with porous calcareous concretions above, ferruginous below; some sticks and impressions of leaves30
1.Brown muck with cypress stumps3–4
White or blue clay with cypress stumps

The cypress stumps of No. 1 were numerous and well preserved.

The writer reproduces Hilgard’s geological map of the lower Mississippi region, in which is represented the distribution of the Port Hudson according to that writer’s views (fig. 22). It will be seen that it was supposed to pass eastward into the coast region of Mississippi, Alabama, and Florida. Westward from Atchafalaya River it was believed to occupy a large part of southern Louisiana and to pass into Texas and around the Gulf coast to near the Rio Grande. It will be observed that in the latter State it corresponds in a general way to what has been called by Deussen the Lissie formation.

Fig. 22.—The Mississippi embayment. Redrawn from Hilgard. Used to show the distribution of the Port Hudson group.

Although Hilgard represents on his map an alluvial deposit as covering the region of the delta, a belt along the western side of the great river as far up as Cairo, and the wide tract between Mississippi and Yazoo Rivers, a study of his paper shows that he believed that much of these regions was underlain by his Port Hudson. He recognized it at Greenwood on the Yazoo, 60 miles east of the Mississippi; at Vicksburg, and at various places in the delta. Usually its upper surface occurs at about low-water level along rivers, and elsewhere is met with in digging wells. At Vicksburg it was encountered by Grant’s Army in digging his famous canal. It was believed by Hilgard that the same deposit was present at Petite Anse, overlying the Orange sand and overlain by more recent deposits.

Inasmuch as Hilgard believed that the Orange sand was laid down at the time when the northern drift was being deposited, he had to refer his Port Hudson to a later time, and this time he seemed to regard as being the epoch called by Dana the Champlain.

McGee referred the deposits of the lower Mississippi Valley (sometimes called the Mississippi embayment) to his Columbia formation (12th Ann. Rep. U. S. Geol. Surv., plate I, p. 392). This formation, in his view, had been laid down during a great subsidence of the borders of the continent and when the waters of the Gulf reached as far north as the mouth of Ohio River or beyond. He relegated Hilgard’s Orange sand to the Pliocene and recognized four phases as belonging to the Pleistocene. These were, beginning below: (1) Port Hudson; (2) Orange sand (of Safford, not that of Hilgard); (3) loess; (4) brown (or yellow) loam. Of these divisions there were really only three, for he regarded the loess as only a phase of the loam and as lying sometimes above, sometimes below the latter. He recognized the Port Hudson clays as flooring the entire flood-plain of the Mississippi from the mouth of the Ohio well toward the gulf shore. The formation was believed to be usually a low-lying one; but at Natchez (as seen by his section given on page 391) it is elevated high above the present flood-plain.

Gilbert D. Harris, geologist in charge of the geological survey of Louisiana, and Arthur C. Veatch, assistant geologist, have contributed much to our knowledge of the Pleistocene geology of the State. Reference to their works will be found in the descriptions of several fossil-bearing localities, especially in the description of Petite Anse.

Harris, in 1905 (Bull. 1, Geol. Surv. Louisiana, p. 13), expressed the conclusion that the longer the geology of southern Louisiana is studied the more futile appears the attempt to make satisfactory subdivisions in the Quaternary deposits—subdivisions that have any definite time or structural limits. He regarded it as a mistake to assign to the Port Hudson a special place in geologic time.

Chamberlin and Salisbury in 1906, as quoted below, made no mention of the Port Hudson formation; but that part of it supposed to be found at Natchez was evidently included in their Natchez formation.

Inasmuch as Petite Anse and Natchez have furnished more species of fossil vertebrates than any other localities in their States, and likewise human relics supposed to be of equal age with the extinct mammals, these places will receive especial attention.

Natchez is the most important locality in Mississippi as regards Pleistocene vertebrate palæontology. So far as the writer knows the first mention of the occurrence of vertebrate fossils here was a note by Dr. G. Troost in 1835 (Trans. Geol. Soc. Penn., vol. I, p. 143), who stated that he had in his possession a tooth of a mastodon found at Natchez.

In 1845 (Proc. 6th Meet. Assoc. Amer. Geologists and Naturalists, pp. 77–79), Dr. M. W. Dickeson, of Natchez, read a paper entitled “On the Geology of the Natchez Bluffs,” in which he distinguished 22 several beds. These were said to be of varying thickness and distinctly marked, but all composed of various colored clays and sands, and containing numerous organic remains, embedded wood, and detrital matter. Probably by far the greater part of these beds were of subordinate importance and do not appear to have been noted since that time. Beneath the surface soil Dickeson recognized a mass of yellow loam 20 to 30 feet in thickness, exceedingly fine and free from gravel. In this had been found shells of Helix and scattered bones of mastodons. Below this came a bed of ferruginous sands and gravels 4 feet thick. This was succeeded below by what he called the mastodon bed, in which Dickeson had detected remains of more than 30 individual mastodons. The thickness of this was not given. The next stratum, his No. 6, was a fine clay of blue color, from 12 to 15 feet thick. In this and his No. 22, an ash-colored clay, at low-water mark, he discovered remains of what has since proved to be Megalonyx jeffersonii. The localities where his fossils were found were not given with exactness.

At a meeting of the Academy of Natural Sciences, October 6, 1846 (Proc., etc., vol. III, p. 107), Dickeson exhibited a large collection of fossil bones obtained by him in the vicinity of Natchez. Among these were the head and lower jaw of the Megalonyx already mentioned. He stated that the stratum that contains these organic remains is a tenacious blue clay that underlies the diluvial drift east of Natchez and which diluvial deposit abounds in bones and teeth of the Mastodon giganteus. Associated with the megalonyx were remains of bear, bison, deer, and horse. The collection was more notable because of the presence of a part of a human innominate bone. Dickeson affirmed that this had been taken out of the blue clay about 2 feet below three associated skeletons of the megalonyx; and it is further stated to have accorded in respect of color, density, etc., with those of the megalonyx and other associated bones. This bone is now in the collection of the Academy of Natural Sciences, Philadelphia.

In 1846 the English geologist, Sir Charles Lyell, studied the geology of the region at Natchez (Second Visit to U. S. N. A., ed. 2, vol. II, pp. 194–201). With him were Dr. Dickeson and B. L. C. Wailles, afterwards State geologist of Mississippi (Wailles, Agric., Geol. Miss., 1854, p. 213). In the yellow loam of the bluffs Lyell recognized loess deposits, from their resemblance to those of the Rhine. These he estimated to occupy the upper 60 feet of the bluff, and in them were found 20 species of land-snails, all yet living. He reported that this loess sometimes passed into a lacustrine deposit which contained shells of Lymnæa, Planorbis, Paludina, Physa, and Cyclas, and that with the land-snails had been found, at different depths, remains of the mastodon, while in clay under the loam (meaning evidently the loess) and above the sand and gravel, entire skeletons of the megalonyx had been met with, associated with bones of the horse, bear, stag, ox (Bison). Lyell noted especially the recent development of deep ravines. One of these, called the Mammoth Ravine, had been formed, he was assured, within the preceding 35 years. Its length was 7 miles and its depth 60 feet. In this ravine was found the human innominate bone referred to above. He was shown this bone, and states that Dr. Dickeson was persuaded that the bone had been taken out of the clay underlying the loam (loess). This indicates that Dickeson himself did not take out the human bone. Lyell thought that, like most of the other fossils, it had been picked up in the bed of the stream, which would simply imply that it had been washed out of the cliffs, and that it may have been dislodged from some Indian grave near the top. He (p. [197]) stated that the place where the bone was found was 6 miles from Natchez. The reader may consult further Lyell’s account of his observations at Natchez in volume III of the American Journal of Science, 1847, page 266.

In 1854 Wailles (op. cit., p. 286) published a list of the vertebrate fossils which had been found in the State. This list had been prepared by Dr. Leidy. While no localities are mentioned in either publication, it is quite certain that most, if not all, of the species had been found at Natchez. Wailles (p. [285]) stated that the most prolific locality was on Pine Ridge, in townships 7 and 8 north, range 3 west, 6 miles north of Natchez. While the name is not used, it is supposed that reference is here had to the Mammoth Ravine mentioned by Lyell. Leidy’s list was as follows:

Hilgard (Agric. Geol., Mississippi, 1860, p. 196, a work not issued until the early part of 1863), republished Leidy’s catalogue of species just mentioned and stated that these had been found in a solid blue clay.

In J. W. Foster’s “Prehistoric Races of the United States,” published in 1873, p. 61, is a statement made by Professor C. G. Forshey, in which he says that he visited the locality where the human innominate bone was found and that it was in Bernard’s Bayou, 2.5 miles north from Natchez. This does not accord with the statement of Wailles, who lived near Natchez and who visited the locality in company with Lyell and Dickeson. Forshey presented reasons for concluding that the bone was not derived from the Bluff formation. He stated that the mastodon bones and all others, of which there were many, were rotten, and that it was only with difficulty that any of them could be preserved. On the other hand, Leidy, in speaking of the bones of the megalonyx found in the Mammoth Ravine (Smithson. Contrib. Knowl., vol. VII, art. 5, p. 6), and of those of the Mylodon (op. cit., p. 48), says that they were in a good state of preservation.

In his work on the Lafayette formation published in 1891 (12th Ann. Rep. U. S. Geol. Surv., pp. 347–521), McGee discussed the geology about Natchez. On page 397 he presented a composite section obtained along about 3 miles of the bluff. This in a modified form is here given.

Section at Natchez.
feet.
7.Loess10 to 50
6.Brown loam10 to 40
5.Stratified loamy sand5 to 15
4.Tenacious blue clay (Port Hudson)10 to 15
3.Cross-stratified sand, with pebbles30 to 50
2.Stratified gravel5 to 15
1.Greenish and blue clay, to above low water (Grand Gulf, Tertiary)5 to 10

McGee noted that these divisions (except the Port Hudson and Grand Gulf) are purely arbitrary, inasmuch as the character and thickness of the beds change more or less within no great distances.

He noted the fact that the loess abounded in mollusks mostly of land and swamp species; also that some of the gravelly beds well down towards the Port Hudson clays had yielded bones and teeth of elephants and mastodons.

In 1898, Dr. B. Shimek visited Natchez and studied especially the loess (Amer. Geologist, vol. XXX, pp. 279–298, with plates X-XVI). He estimated the thickness of the loess as not exceeding 30 feet. He collected from this loess more than 4,600 shells of mollusks; and these proved to belong to 39 species or well-recognized subspecies. These species are all terrestrial in habit and all are now found living either on the hills in the immediate vicinity or in similar situations in other parts of the South. Shimek came to the conclusion that the loess of that region had been deposited by the action of the winds. He was unable to find any “brown loam” above the loess, the presence of which other authors had affirmed.

Shimek found no traces of mammalian bones in the loess and was inclined to doubt that they occur there. He does not appear to have visited the locality from which most of the bones were reported.

Chamberlin and Salisbury, in 1906 (Geology, vol. III, p. 386, fig. 513), discussed briefly the geological situation at Natchez. The Natchez formation (evidently including the Port Hudson) has a thickness of about 200 feet and is made up of materials derived mostly from the so-called Lafayette, on which it there rests unconformably. In this Natchez formation are also crystalline pebbles and calcareous clays assignable to wash from the glacial regions. Between this Natchez formation and the overlying loess a marked interval is indicated. The authors are inclined to assign the Natchez deposits to the earliest part of the Pleistocene, viz, to the Aftonian and the drift epoch preceding the Aftonian. Since the time when the Natchez formation was deposited the great trench of the Mississippi Valley, about 60 miles wide, has been excavated.

Already on page [391] has been given the list of fossil mammals which Leidy made out for the State geologist of Mississippi, B. L. C. Wailles. A revision of this is here presented, with the addition of Castoroides ohioensis.

According to Lyell (Amer. Jour. Sci., vol. III, 1847, p. 268), Megatherium and Castoroides had been found in the bluffs at Natchez.

From this list of mammals it is possible perhaps to reach some conclusion regarding the geological age of the deposits containing them. In case we accept without reserve the species, 16 in number, as determined, only 3, Tapirus terrestris, Odocoileus virginianus, and Ursus americanus, are yet living, leaving about 81 per cent of the whole as being extinct, and what was called Tapirus terrestris was probably an extinct form. This alone makes it probable that the time of their existence was early in the Pleistocene. All three of the supposed existing species may, however, prove to belong to extinct species closely related to those whose names they yet bear.

Certain species may be left out of consideration because of paucity of specimens and our consequent lack of knowledge of them. These are Megalonyx dissimilis, Ereptodon priscus, and Ursus amplidens.

In case the high percentage of extinct species is not recognized as being decisive, we may consider the assemblage from another point of view. Certain species of the list appear to have existed throughout the Pleistocene, at least from the time of the first interglacial stage. These are Megalonyx jeffersonii, Mammut americanum, Elephas columbi, and Castoroides ohioensis, and their presence indicates only a Pleistocene time. Others of the list are not known to have existed after the time of the last Wisconsin drift-sheet, and may be supposed to have become extinct before that time. These are Mylodon harlani, Equus complicatus, Equus leidyi, Tapirus haysii, and Bison latifrons. All of these quite certainly existed until after the Illinoian drift period, probably into the Sangamon interglacial, except apparently Equus leidyi.

The list contains no species of primitive mastodons belonging to the genus Gomphotherium, no species of Hipparion, no camels; and Elephas imperator appears to be missing. There is, therefore, no necessity for believing that the mammal-bearing deposits at Natchez are as old as the Sheridan, or Aftonian stage, but the ancient forms mentioned may at any time turn up there or elsewhere in the immediate region.

The presence of Symbos cavifrons might be supposed to point to a rather late date in the Pleistocene; but evidence has accumulated which indicates that it reaches back farther in time than we have supposed. Taking all into consideration, the writer concludes that the fossil vertebrates found at Natchez date back at least as far as the time of the Illinoian drift stage. There is nothing to prove that they are not as old as the Aftonian stage, except the apparent absence of camels, Elephas imperator, mastodons belonging to Gomphotherium, and a multiplicity of species of Equus.

Unfortunately, vertebrate fossils, especially those known to belong to definite horizons in the Pleistocene, are, aside from Natchez, rarely found; but near Orizaba, in Tippah County, a tooth of a horse has been discovered which appears to have been Equus leidyi (p. [200]). Remains of a deer (p. [234]) have been found in a railroad cutting at Aberdeen, Monroe County. Mastodons are not uncommon, as may be seen on consulting the pages where these animals in Mississippi are discussed (pp. 124 to 126).