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 below 8–10
5. White and yellow hardpan 18
Orange and yellow sand, sometimes ferruginous sandstone,
irregularly stratified 8–15
4. Heavy greenish or bluish clay 7
3. White indurate silt, or hardpan 18
2. Heavy green clay with porous calcareous concretions above,
ferruginous below; some sticks and impressions of leaves 30
1. Brown muck with cypress stumps 3–4
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.
[Illustration:
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:
Felis atrox Leidy.
Ursus americanus fossilis.
U. amplidens Leidy.
Equus americanus Leidy.
Cervus virginianus fossilis.
Bison latifrons Leidy.
Boötherium cavifrons Leidy.
Elephas primigenius.
Tapirus americanus fossilis.
T. haysii Leidy.
Megalonyx jeffersonii Harlan.
M. dissimilis Leidy.
Mylodon harlani Owen.
Ereptodon priscus Leidy.
Mastodon giganteus.
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. Loess 10 to 50
6. Brown loam 10 to 40
5. Stratified loamy sand 5 to 15
4. Tenacious blue clay (Port Hudson) 10 to 15
3. Cross-stratified sand, with pebbles 30 to 50
2. Stratified gravel 5 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_.
Megalonyx jeffersonii (p. 40).
M. dissimilis (p. 41).
Mylodon harlani (p. 41).
Ereptodon priscus (p. 41).
Equus complicatus (p. 200).
E. leidyi (p. 200).
Tapirus haysii (p. 208).
T. terrestris (p. 208).
Odocoileus virginianus (p. 233).
Symbos cavifrons (p. 254).
Bison latifrons? (p. 265).
Mammut americanum (p. 125).
Elephas columbi? (p. 180).
Castoroides ohioensis (p. 280).
Ursus americanus.
U. amplidens.
Felis atrox.
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).
TENNESSEE.
(Figure 23.)