the topography and geology of the region through which the Brunswick
Canal was being constructed (map 40). On one of the plates of the work
is a section from the ocean westward 21 miles. About 10 miles west of
St. Simon’s Island the canal passed through Six-mile Swamp. This is
connected at its northern end with Altamaha River, at the southern with
Turtle River. The swamp has thus the appearance of a lake which has
become filled with alluvial deposits. These consist of a compact clay,
usually yellow and impregnated with iron. There are thin strata of soft,
chalky marl and many fragments of petrified wood. At the bottom of this
deposit were found the bones of _Megatherium_, _Elephas_, _Mammut_,
_Equus_, and _Bison_. Beneath the clay stratum was sand with marine
shells. Overlying the clay was a thin stratum of vegetable and sandy
loam. The bones occurred at a depth of from 4 to 6 feet. In no instance,
except when they had been washed out into the salt-water creek, was
there any abrasion of the surface or incrustation of marine shells.
The geologist Charles Lyell (Second Visit, etc., vol. I, p. 347) stated
that part of a skeleton of a megatherium, dug out in cutting the canal,
was so near the surface that it was penetrated by the roots of a pine
tree. As a considerable number of the bones of one skeleton were found
together, Lyell supposed that a whole carcass had been floated down the
river to the spot.
Even before remains of fossil vertebrates had been found at Brunswick,
bones had been discovered at Skidaway Island, near Savannah. As early as
1823, S. L. Mitchill (Ann. N. Y. Lyc. Nat. Hist., vol. I, p. 58)
announced the finding of teeth of _Megatherium_ at this place. More than
20 bones of the same animal were reported from the same locality in 1824
by William Couper. In 1846 (Hodgson’s “Memoir on Megatherium,” pp.
25–30), Dr. Joseph Habersham published a list of the species discovered
up to that time. Lyell (Second Visit, etc., vol. I, p. 313) gave an
account of his visit to the locality and noted the species obtained. The
following list appears to contain all found there:
Elephas columbi (p. 157).
Mammut americanum (p. 120).
Bison sp. indet. (p. 262).
Equus leidyi? (p. 194).
Megatherium mirabile (p. 36).
Mylodon harlani (p. 37).
Terrapene canaliculata.
The box-tortoise _Terrapene canaliculata_ was described by the writer in
1907 (Bull. Amer. Mus. Nat. Hist., vol. XXIII, p. 850, figs. 5–7) on
fragmentary materials found in the U. S. National Museum. These had been
sent there by Dr. J. P. Scriven, who had been active in collecting the
fossil vertebrates about Savannah. Whether the remains of this
box-tortoise were found on Skidaway Island or in Whitemarsh Island is
uncertain.
Besides these species, found on Skidaway island, two species, _Mammut
americanum_ and _Mylodon harlani_, have been found at Heyner’s (or
Hainer’s) Bridge. This is about 7 miles south of Savannah, where the
road crosses Vernon Creek (Lyell, “Travels in North America,” vol I, pp.
163–164). Here the stream is called White Bluff Creek. In order that the
reader may get a clear understanding of the conditions at this important
locality, a map found in Hodgson’s Memoir is reproduced (map 40).
The whole region south of Savannah, between the mouths of Savannah and
Ogeechee Rivers, is low and much divided into islands by streams
connected with the rivers mentioned. A considerable part of these
islands consists of marshes, which are usually overflowed by the tides.
Most of the fossil bones were found along the southern bank of Skidaway
River, in two places, apparently about 0.5 mile apart and near the
western end of the island. On the map Hodgson has named the locality
Fossilossa. Here Skidaway River made a bend which caused the bank to be
eroded away, thus exposing the bones. According to Couper (Hodgson’s
Memoir, p. 40), the bones were embedded in the marsh formation at about
the level of very low-water. Lyell (Second Visit, etc., vol. I, p. 314)
stated that the bones occurred in a dark peaty soil, or marsh mud, above
which was a stratum of sand 3 or 4 feet thick; while below the peaty
soil and below sea-level was sand containing many marine fossil shells,
all belonging to species yet living on the neighboring coast.
The authors quoted state that at various places along the Georgia coast
are found stumps of trees, cypress, cedar, and pine, in the deposits of
the salt marshes and at a depth of from 2 to 4 feet below high-water.
This is taken as evidence of subsidence in that region.
It is a matter of importance to know how those animal remains reached
their place of burial. It has been suggested that whole carcasses had
been floated down the streams and sunken where the bones are found. This
is possible, but not probable. The peaty nature of the deposit inclosing
the bones appears to be opposed to this view; nor could disarticulated
bones have been washed down far from above, for they show no signs of
attrition. The most probable explanation is that these animals lived and
died about where their bones were discovered. At some past time the
surface stood at a higher level than at present, although low enough to
be more or less marshy. It probably supported a dense forest growth, and
hither the species listed above resorted, with many others not yet
discovered.
The animals inhabiting the region represent the same fauna found at so
many places in Florida and Texas. The writer believes that they existed
during the early part of the Pleistocene, approximately during the
Aftonian interglacial; and that some of the species, as _Megatherium_,
_Mylodon_, _Equus_, and _Tapirus haysii_ became extinct before the
advent of the Wisconsin glacial stage, probably a long time before this.
FLORIDA.
(Maps 7, 8, 15.)
For the most recent descriptions of the geology of Florida one must
consult the Annual Reports of the Florida Geological Survey, issued by
the State geologist, Dr. E. H. Sellards, and Water supply Paper 319 of
the U. S. Geological Survey, prepared by George C. Matson and Samuel
Sanford and published in 1913. In the latter work are two large maps,
one representing the topography of the State and the distribution of the
various geologic formations; the other presents a generalized view of
the distribution of Pleistocene terraces, as recognized by Matson and
Sanford. The Second Annual Report of the Florida Geological Survey
contains a map similar to the first mentioned.
From these maps it will be seen that the surface of Florida is largely
occupied by Pleistocene deposits. According to Matson and Sanford, these
deposits present themselves as disposed mostly in three principal
terraces; and these are believed to indicate that the State was at one
time largely submerged beneath the sea and that its present condition
was attained after three principal upward movements. As shown on plate V
of the geologists just named, the northern half of the peninsula at the
time of greatest depression was represented by a number of islands, two
of considerable size. One of these was situated at the northern end of
the peninsula, the other near its center. The materials laid down around
these islands and bordering the dry land along the northern border of
the western half of the State form what is called the Newberry terrace.
Its surface stands now at a height varying from 70 to somewhat more than
100 feet above sea-level. A second elevation exposed the deposits which,
at least in part, constitute the next terrace, the Tsala Apopka. Its
surface is a plain having an elevation of 40 to 60 feet above sea-level.
At this stage the islands of the peninsula had coalesced, and the dry
land extended southward nearly to the present Lake Okeechobee. A broad
belt along the Atlantic and Gulf coasts, now dry land, was still
occupied by salt water. A third elevation of the land left exposed the
lowest terrace, the Pensacola, that bordering the Atlantic and Gulf
coasts and including the southern end of the peninsula somewhat farther
north than Lake Okeechobee. The elevation of this terrace varies from
that of sea-level up to about 40 feet.
The materials composing the terraces in Florida are principally sand
with local deposits of clays. In the southern part of the State
important beds of limestone are found in the Pensacola terrace. These
beds are shown on Matson and Stanford’s geological map. At St. Augustine
and along the coast southward are beds of sea-shells cemented into
coquina. Where cementation has not occurred there are beds of loose
shells and of marl and sand.
The writer has already (p. 346) expressed his opinion regarding the
Coastal Plain terraces found in the States farther north. He finds in
Florida nothing to contradict, but much to confirm, that opinion.
Whatever may be the origin of Newberry and Tsala Apopka terraces, they
were not laid down in salt water. From the descriptions of the deposits
there the stratification and the alternation of the materials do not
exist that one might expect; but, above all, there seem to be no marine
fossils to attest to the presence of the sea. In Florida, too, here and
there over these higher lands there are found, in place of marine
fossils, the remains of many extinct land animals, as mastodons,
elephants, horses, ground-sloths, and the like.
As regards the Pensacola terrace, there are found at its base, within a
few feet above or below sea-level, deposits containing remains of such
animals as have just been mentioned, besides many others. Often the
state of preservation of these remains and the condition of their burial
are such that we must conclude that the animals lived and died on the
spot. Furthermore, these animals constitute an assemblage corresponding
to that found in western Iowa, in Nebraska, and in Oregon, which are
believed to have existed during the first interglacial stage. It
corresponds also to that met with under similar conditions and at the
same level at Savannah, at Charleston, at Brunswick, and at Long Branch.
In most cases, too, this fossiliferous stratum is overlain with very
scant deposits. By some geologists and palæontologists the animals are
regarded as belonging to the Pliocene.
If the reference of the fossil vertebrates mentioned is not wholly
wrong, it follows that the lowest terrace or plain along the coast was
not laid down late in the Pleistocene, but at an early stage, and the
higher plains must have been formed at still earlier times.
At Vero, as will be shown on page 382, a large assemblage of fossil
vertebrates has been secured. The bed furnishing the oldest fossils,
those of the bed known as No. 2 and believed to be of about first
interglacial age, is underlain by a bed of marine shells, also of
Pleistocene age. This bed is regarded by Dr. E. H. Sellards as being
equivalent to the coquina which is so well known at St. Augustine; and
the same formation is found here and there along both coasts of the
peninsula (Matson and Sanford, op. cit., p. 192). Probably not all
deposits that are called coquina are of the same age, but the deposits
in question pass, on the landward side, beneath the deposits which bear
vertebrate fossils. The bed at Vero, No. 2, must have been laid down
after an uplift had brought above sea-level the bed of shells No. 1, on
which No. 2 reposes; that is, between the time of deposition of No. 1
and No. 2 there must have elapsed a considerable interval of time. The
shell deposit, therefore, probably belongs to the first glacial epoch,
the Nebraskan. Inasmuch as a similar vertebrate fauna is found on both
the eastern and the western coasts of the peninsula, it follows that any
Pleistocene deposits underlying these vertebrate-bearing beds belongs to
the Nebraskan stage; in places these have great thickness. Matson and
Sanford (op. cit., pp. 194–195) concluded that the maximum thickness of
the Pleistocene in southern Florida, disregarding the sandhills, is
probably about 125 feet. Even if it were a matter of importance to
determine in or on which terraces the vertebrate fossils are found, it
would not always be easy to do so. The majority of specimens have been
discovered around the coasts of the State, and therefore in deposits
referred to the youngest terrace. In other cases it is difficult to
determine the terrace in which fossils are buried, partly because of
imperfect records as regards locality, kind of deposits, and depth of
burial, partly because each terrace extends up the river valleys beyond
its general border. The various fossil-bearing localities will therefore
be taken up by counties, beginning at the western end of the State and
ending at the southern end.
_Jackson County._—As already recorded on page 121, a tooth of _Mammut
americanum_ has been found at Marianna. No details have been recorded.
The Newberry terrace extends nearly or quite to this town. If it could
be shown that this tooth had been buried in that terrace when it was
formed, it would probably have to be referred to the time of the first
glacial stage.
_Gadsden County._—It appears that no vertebrate remains belonging to the
Pleistocene have been found in this county, except a tooth of _Mammut
americanum_ (p. 157) which was discovered somewhere in Little River.
_Wakulla County._—On page 157 the finding of a tooth of _Elephas
columbi_ somewhere along St. Marks River has been mentioned; also the
discovery of a part of a skeleton of either a mastodon or an elephant
somewhere about Wakulla Springs.
_Columbia County._—A mastodon tooth has been found in this county 3
miles northwest of Fort White (p. 121). To which terrace it belonged or
what is its place in Pleistocene time it is impossible to say.
_Nassau County._—At Stokes Ferry have been found some teeth of an
extinct horse (p. 194), a fragment of a tooth of an elephant (p. 180)
and some ear-bones of a whale. Veatch and Stephenson (Bull. 26, Geol.
Surv. Georgia, p. 394) report that these appeared to come from either
the Charlton formation or the Satilla. If the Charlton really belongs to
the Pliocene it is not probable that the fossils were derived from it;
if they were derived from the Satilla, they do not belong to late
Pleistocene.
_Duval County._—On page 106 of the Eighth Annual Report of the Florida
Geological Survey, Sellards reported the finding of remains of _Mammut
americanum_ (p. 122), _Elephas columbi_ (p. 157), an undetermined
species of _Bison_ (p. 262), and an undetermined species of _Odocoileus_
(p. 232), near Pablo Beach, at station 120 on the Inland Waterway Canal.
Here, too, has been discovered a bone of _Trachemys? nuchocarinata_.
Sellards stated that the position of the beds here is the same as that
of the other localities along the Atlantic coast, the fossils being
found in sand and muck which rest upon Pleistocene shell-marl. The
locality is, of course, on the youngest terrace; but that, in the
opinion of the writer, belongs to the early Pleistocene.
_St. John’s County._—At a place 28 miles south of St. Augustine, along
the Inland Waterway Canal, Mr. Fred P. Allen, of St. Augustine,
collected on the Almero farm remains of _Mammut americanum_ (p. 122),
_Elephas columbi_ (p. 158), _Mylodon harlani?_ (p. 37), _Equus_ sp.
indet. (p. 194), the box-tortoise _Terrapene antipex_, and a dermal
plate of perhaps _Alligator mississippiensis_. These were found in the
banks of the canal. Here, at least, the horse and the mylodon, taking
into consideration the geological circumstances, indicate early
Pleistocene, equivalent to the first interglacial stage.
_Levy and Alachua Counties._—Geologically these counties furnish
important localities because of the presence of the Alachua clays
(usually referred to the lower Pliocene or even the Upper Miocene) and
deposits belonging to all three of the Pleistocene terraces, Newberry,
Tsala Apopka, and Pensacola. The Alachua clays first require
consideration, for in them have been found a considerable number of
species of vertebrates which usually indicate Pleistocene deposits. The
localities where Alachua clays have furnished vertebrate fossils, as
indicated on Matson and Sanford’s map (Water Supply Paper 319, U. S.
Geol. Surv., plate I), are situated, one around Archer, Alachua County
(the type locality), second, about 5 miles west of Williston, in Levy
County, and a third about 5 miles east of Newberry, in Alachua County.
The clays referred to form accumulations in depressions on the surface
of the Ocala limestone, itself belonging to the Eocene. The deposits are
said to average in depth about 10 feet, but are often thinner and
occasionally much thicker. They have furnished a considerable number of
species of vertebrates. A list, prepared by Dr. Leidy, of those found at
Archer was published in 1892, in Bulletin 84 of the U. S. Geological
Survey, on page 129. Besides these, Leidy had previously reported a
tapir, a small crocodile or alligator, and a bone thought to belong to
the extinct _Cervus americanus_ (_Cervalces scotti?_), but which was not
afterward mentioned. The rhinoceroses and the camels were described by
Leidy and Lucas in 1896 (Trans. Wagner Free Inst., vol. IV, pp. 1–61
with plates).
Herewith is presented a list of such vertebrates as have been found at
Archer. It appears necessary to retain for the rhinoceroses the specific
names given them by Leidy.
Gomphotherium floridanum (p. 121).
Odocoileus osceola? (p. 232).
Procamelus major (p. 224).
P. minor (p. 224).
P. minimus (p. 224).
Teleoceras proterus (p. 211).
Aphelops longipes (p. 211).
Tapirus haysii? (p. 207).
Hipparion ingenuum (p. 195).
Megatherium mirabile (p. 37).
Alligator (or Crocodylus) sp. indet.
The following vertebrates have been collected east of Williston, in the
place mentioned in Dall’s report of 1892, on page 129, as Mixon’s:
Gomphotherium floridanum (p. 121).
Procamelus major (p. 224).
Teleoceras proterus (p. 211).
Hipparion ingenuum (p. 196).
Hipparion plicatile (p. 196).
Thinobadistes segnis (p. 37).
Manatus antiquus?.
Pseudemys cælata.
Atractosteus lapidosus.
The list from the locality east of Newberry (Hallowell’s place of Dall’s
report) is rather short. _Equus littoralis_, _Odocoileus osceola?_,
_Hipparion_ sp. indet., and _Parahippus_ sp. indet. have been reported
(Rep. Florida Geol. Surv., vol. V, p. 58; vol. VIII, pp. 42, 94). At
Neals, Alachua County. _Tapirus terrestris?_, _Gomphotherium
floridanum_, and _Hipparion_ sp. indet. have been collected (Sellards as
cited). At Juliette, same county, _Gomphotherium floridanum_ has been
secured, and at Hernando the same species; also _Hipparion_ sp. indet.
and _Procamelus_ sp. indet. (Sellards Florida Geol. Surv., vol. V, p.
58). Along Santa Fe River, in the Buttgenbach mines, 6 miles north of
Wade, have been found teeth of _Equus_ and a tooth of _Bison_.
At Dunnellon, about 25 miles south of Williston, from the phosphate
mines along the Withlacoochee River, have been obtained fossil
vertebrates so similar to those found in the Alachua clays that Sellards
concluded to unite his Dunnellon formation and the Alachua clays into
one to be called the Alachua formation (6th Ann. Rep. Florida Geol.
Surv., p. 161). The list of vertebrates found at and about Dunnellon is
as follows, including the species dredged in Withlacoochee River:
Megalonyx sp. indet. (p. 38).
Chlamytherium septentrionale (p. 138).
Ursus sp. indet.
Felis sp. indet.
*Gomphotherium floridanum (p. 122).
Mammut americanum (p. 122).
Elephas imperator (p. 162).
Trichechus manatus.
*Parahippus sp. indet. (p. 196).
*Hipparion plicatile (p. 196).
Equus leidyi (p. 196).
Tapirus sp. indet. (p. 207).
*Aphelops longipes (p. 211).
*Procamelus minor (p. 225).
Odocoileus osceola (p. 233).
Bison sp. indet. (p. 263).
The species marked by an asterisk are regarded by Doctor Sellards and
others as belonging to the Miocene or Pliocene (8th Ann. Rep. Florida
Geol. Surv., p. 94). See also Sellards, 1913 (5th Ann. Rep. Florida
Geol. Surv., p. 58; 8th Rep., p. 104).
On the basis of the fossil vertebrates it can hardly be denied that the
Alachua clays and the phosphate mines at Dunnellon are of the same
geological age. According to Sellards, the formation belongs to the
upper Miocene or to the lower Pliocene. Merriam (Bull. Dept. Geol. Univ.
Cal., vol. X, p. 439) refers it to the Pliocene. Although there is
present a strong palæontological element which represents the
Pleistocene, the reference of the formation to the late Miocene or early
Pliocene has seemed to be required by the presence of _Gomphotherium_,
_Procamelus_, _Teleoceras_, and _Hipparion_. The Pleistocene species are
usually accounted for on the supposition that they are intrusions from
more recent deposits.
A figure from Sellards (Geol. Surv. Florida, vol. VII, p. 53), only
slightly modified is intended to show the relation of the
phosphate-bearing formations to those underlying them (fig. 21).
It is worth our while to consider whether or not the reference of the
Alachua formation to the Miocene or early Pliocene is required by
palæontological evidence. _Gomphotherium_ is characterized by having
molar teeth which on abrasion at one or both ends of each crest, present
a trefoil pattern of the enamel; also by having a band of enamel on each
of the upper tusks. Now, teeth having the same structure are not
uncommon in deposits of undoubted Pleistocene age in Kansas and Texas.
That the animals possessing these teeth had tusks with enamel bands is
not known, but it is quite possible that such enamel bands were present.
[Illustration:
FIG. 21.—Diagrammatic sketch of geologic structure of Florida from
north to south passing through the hard rock and pebble phosphate
fields, showing relation of the phosphate deposits to the underlying
formations. After Sellards.
]
1. Georgia-Florida State line.
2. Suwannee River.
3. Lake City.
4. Santa Fe River.
5. Withlacoochee River.
6. Lakeland.
7. Arcadia.
8. Caloosahatchee River.
9. Gulf Coast.
_a_ Upper Oligocene phosphatic marls.
_b_ Ocala limestone.
_c_ Hard rock phosphate.
_d_ Bone Valley formation.
_e_ Pleistocene deposits (Pliocene and Pleistocene of Sellards).
The genus _Hipparion_ is not confined to the Tertiary. Teeth have been
discovered in the Aftonian of Iowa (Hay, Geol. Surv. Iowa, vol. XXIII,
p. 150) and in Missouri (op. cit., p. 149). The writer has described a
species of the genus, _Hipparion cragini_, collected by Professor Cragin
in the Sheridan beds in Kansas (Kansas Univ. Sci. Bull., vol. X, p. 42).
One may be justified in suspecting that _Procamelus_ lived on into the
Pleistocene. Not only has it been found associated with Pleistocene
fossils in five places in Florida—Archer, Williston, Dunnellon,
Hernando, and Ocala—but it has been met with in possible Pleistocene
deposits (the Idaho formation) in Idaho, which furnishes _Equus_,
_Cervus_, _Castor_, and _Stegomastodon mirificus_ (the type of which
belongs in the Sheridan beds). Furthermore, the writer has had occasion
to describe a collection of fossils, believed to belong to the early
Pleistocene, which was obtained at Anita, Coconino County, Arizona.
Among these fossils are two species of _Procamelus_ much like those
described by Leidy from the Alachua formation (Proc. U. S. Nat. Mus.,
vol. LIX, pp. 622–626). The writer believes that the genus _Procamelus_
persisted into the early Pleistocene.
Two species of rhinoceros have been collected in the Alachuan formation,
_Teleoceras proterus_ Leidy and _Aphelops longipes_ Leidy. Both occurred
at Archer, while _T. proterus_ was found near Williston and _A.
longipes_ at Dunnellon. A rhinoceros has been discovered in the Idaho
formation, with the Pleistocene species named above in connection with
_Procamelus_ of these beds. In Oregon Cope made a collection which has
been examined by Dr. W. D. Matthew (Bull. Amer. Mus. Nat. Hist., vol.
XVI, p. 321). Here again _Teleoceras_ was supposed to have been found
with _Hipparion_, camels belonging to _Camelops_ (or _Procamelus_),
_Elephas_, and _Equus_. Matthew thought that there had happened, either
before the fossils were collected or afterwards, a mingling of elements
of two distinct faunas.