ART. XXXIV.-Geology of South Alabama; by C. S. HALE, Mobile.

Or the three divisions included in the tertiary system, the upper, middle and lower,—or agreeably to the nomenclature of Mr. Lyell, the pliocene, miocene, and eocene-only the last has been found with certainty to exist in Alabama; and even this appears to be limited to the older portion of the series. For certain deposits of this formation, which occur in the Carolinas and Florida, contain fossils specifically distinct from those of the Alabama beds, and which evince that the former localities embrace a newer part of the series.

The geographical limits of the formation, on the north, may be defined by an imaginary line passing between the Upper and Lower Peach-tree landings, on the Alabama river; through Moscow on the Tombecbee, thence by the Suearnochee creek, through Kemper and Carrol counties, Miss., to Arkansas state, and to Natchitoches on the Red river. On the south, the last knobs of the coralline white limestone beds disappear beneath the overlying sands and clays near the junction of the Alabama and Tombecbee rivers. And on the Mississippi the equivalents of these beds terminate near its junction with the Red river, forming a zone about sixty miles in width.

The surface of this region is generally very uneven, consisting principally of the white limestone beds, which have been furrowed out into detached precipitous masses, laying bare, in many instances, the subsequent strata, and the whole is often covered by more recent deposits of sand and clay.

The following is the order of the eocene series of Alabama. 1. (or lowest) Clay bed.

2. Lignite.

3. Sand and shells.

4. Clay bed with oysters.

5. Marly arenaceous limestone.

6. Clay bed with oysters.

Section of the Claiborne bluff.

The best natural section of these beds occurs at Claiborne, and may be regarded as normal deposits. This cliff which is nearly two hundred feet in height, includes the entire series of the formation with the exception of a few strata at the two ex

tremes.

The basal bed of the cliff which may be seen here at extreme low water, is a sandy deposit, partially developed at this locality, but in other places it exhibits very decided characteristics, as an important part of the group. We have identified its existence

through a wide geographical range. Its northern outcrop may be seen near Black's and Wood's bluffs, on the two main water courses. Its thickness varies from fifteen to twenty feet. It consists of fine quartzose sand, mixed with silicate of iron, and is sometimes marly by testaceous remains, with which it greatly abounds. The best development of this deposit occurs in Clark county on Bashui creek and its branches. It is here densely charged with fossils, including nearly all the different species of testacea common in the other parts of the series, together with many new ones, some of which are unique. Of the latter may be noticed a species of Rostellaria, differing from Lea's R. Lamarckii in having a more attenuated rostrum, and a very prominent tubercle situated on the back of the body whorl. Also a new species of Voluta, having a general resemblance to V. luctator of the London clay, but differing in a remarkable deposit of enamel behind the aperture, forming a large bourelet covering half the spire to the summit, enveloping also the folds of the columella, and otherwise flattening and deforming the symmetry of the aperture. Also a new species of Tornatella: shell robust, spirally fluted with flattened ribs, spire attenuated, two stout folds on the columella, outer lip denticulated. A new species of Ranella transversely ribbed, cancellated, with small intermediate varices between the two principal ones, and coarse indentations on the inner margin of the outer lip. Another species answering to Cassidaria carinata, Lam., figured in Lyell's Principles of Geology, as a characteristic of the European equivalents; the only difference exhibited in our shell is that of possessing three instead of four rows of tubercles. The bed under consideration which we designate No. 3, is the source of several mineral springs, as the Tallahatta, Bladon, Monroeville, Lauderdale, and some others of less notoriety. These all appear to be identical in their mineral properties, which are evidently derived by infiltration from the ingredients of the subjacent bed of lignite through which they percolate. But this bed of lignite, (No. 2,) for other reasons may be considered a very important part of the series. lies upon the lowest bed of the group, which last, No. 1, consists of bituminous clay, more or less sandy and sometimes containing large masses of sandy concretions. This clay bed is about twenty-five feet in thickness and rests conformably upon the subjacent cretaceous beds. It may be traced along the Alabama river from Tate's ferry to near the Upper Peach-tree landing, where it terminates; also on the Tombecbee river from Wood's bluff to its termination, at Black bluff. It appears to be destitute of fossils; but with its associated bed of lignite, it forms a very distinct line of demarkation between the tertiary and cretaceous systems. At Grayson's landing on Coal bluff, as it is sometimes called, the deposit of lignite is well developed in con

It

nexion with the overlying sand and subjacent clay bed. thickess here amounts to four feet. The color is dull black, texture compact with occasional thin fibrous laminations, structure massive, sometimes fragmentary; it burns without swelling or caking, and abounds with sulphate of iron both crystallized and amorphous.

Want of leisure has prevented a suitable examination of its organic remains. The vegetable part however furnishes decided evidence of its intertropical character. Between our two principal water courses this deposit of lignite lines the bottom and sides of the streams through a zone ten or fifteen miles in width. It occurs in a western direction in Pigeon creek on the border of the state of Mississippi, near the northern limits of Washington county. It is found also at Natchitoches on Red river, where the underlying bed consists of a grayish plastic clay, very adhesive; on Bedia's creek near the Trinity river, Texas; at Robin's ferry on the Brazos; and at Bastrop on the Colorado. At all these places the lignite occupies the same relative position in the series, and is probably continuous through the whole of this extent, marking the former coast line.

The greensand deposit, No. 3, already noticed as partially developed at the base of Claiborne bluff, passes insensibly into No. 4, an argillaceous muddy deposit above, with a thickness varying from fifteen to twenty feet. The fossils of this bed are limited almost exclusively to the Ostrea genus; the only exceptions appear to be the Cardita planicosta, two or three species of Turritella and an Arca. The stratum No. 4, also makes its appearance at Coffeeville landing on the Tombecbee, where it exhibits the same identical fossiliferous character.

There occur here however a new species of Turbinolia, resembling very much the Turbinolopsis ochracea of Lamourouxtwo or three new species of Lonsdale's new genus Endopachys, also a new species of Lunulite. This stratum may also be seen at Bell's landing on the Alabama, where its thickness amounts to fifty feet. At the bottom of this cliff with the Ostrea common in the stratum, I found the Cardita planicosta of very large dimensions.

The next in the ascending series is a limestone deposit with sandy and argillaceous ingredients variously intermixed. The few species it contains are common also in the other beds, and probably were introduced here in some adventitious way. I have not been able to discover this deposit anywhere else except in the Claiborne section.

To this limestone deposit, another clay bed, No. 6, succeeds, being about twenty feet in thickness. It is remarkable for nothing else but a band of oysters of the selliform species, all of which are of a mature size, and probably lived on the spot. This

clay bed with oysters, occurs again five miles below on the river, in the same relative situation in the series; in both of which instances the oysters are full grown; whereas in the lower bed both at Claiborne and Coffeeville, they are principally of immature size, a peculiarity which may possibly be owing to the circumstance of their exposure in the latter case to the influence of a current, when small and easily drifted.

The next bed, No. 7, is a deposit of fine yellow quartzose sand with a small mixture of silicate of iron; in some instances it is highly ferruginous. It contains nearly all the different species of fossils found in the series. Its medium height is about fifteen feet. I obtained, at different times, from this stratum, various species of radiata, mollusca, reptiles, fish, and mammifers, amounting in all to about three hundred. Those which embrace the greatest number of individuals, belong to the genera, Cytherea, Cardita, Crassatella, Pectunculus, Crepidula, Oliva, Turritella, Dentalium, and Corbula. Several of these species are grouped in distinct layers or bands; but the greater portion of them seem to have been promiscuously thrown together, as if they had been exposed to the violent agitation of the waves. The testacea of this bed are all marine and nearly all of them of the littoral kind. Not a single species of land or freshwater shells has yet been found in any of these beds.

A small seam of earthy lignite, disseminated in small fragmentary masses, forms a somewhat striking feature about midway in the yellow sand; and associated with it were found the only remains yet discovered of terrestrial mammalia. The greater portion of the fossils peculiar to this bed have already been described. We shall therefore omit the notice of such, and at present merely allude to those in our cabinet which are unique. One of the most remarkable of these is that of a Nautilus, which appears to be restricted to this deposit. Our specimen is too imperfect to admit of a very particular description. In its entire state it could not have been less than one foot in diameter. We have also obtained from this deposit several new species of Echinoderms, and Madrepores, and many new species of Molluscs, of the genera Fusus, Terebra, Ancillaria, Phasianella, Murex, Turretilla, Solarium, Scalaria, Pyrula, Venus, Arca, Tellina.

Of fish, there are remains of the Pristis, spines of the Ray, various species of palatal teeth, vertebræ of many unknown species, and teeth and vertebræ of the shark. Of terrestrial mammalia there are several maxillary fragments of small quadrupeds. The most interesting relic of this class is the cranium of a quadruped, whose type is now exclusively confined to the southern part of this continent. It belongs to an extinct genus of the Edentate order of animals, and is allied to the existing armadillos. Our fossil answers to a skeleton lately found in the tertiary beds near Buenos Ayres,

called the glyptodon. The occipital surface of the skull slopes forward, from the plane of the occipital foramen, at an angle of 45°. In the small existing armadillos it is vertical. In the glyptodon this surface is divided by a medium vertical ridge, and separated from the upper surface of the skull by a transverse ridge. The interorbital part of the upper surface of the cranium is somewhat broad, and nearly flat, and concave at its posterior half. The anterior part of the base of the cranium, shows the large cavities of the olfactory bulbs, and the remains of an extensive cribriform process, evincing that the organ of smell was well developed. The existing species of this order of animals inhabit the warm and temperate parts of South America. It is characterized by the sloth, the ant-eater, and the armadillo. In their habits they are nocturnal and gregarious, burrow in the ground, and feed on dead bodies, reptiles, the root of the manioc, and other succulent plants. Were this the only relic of the family that has been found in this part of the continent, it might seem presumptuous to deduce any special conclusion from its occurrence in our tertiary beds. A single individual might, for once, have wandered beyond the limits of its habitat, or by some accidental means have been transported into a foreign situation. But since other kindred remains of this family, the megatherium, for instance, have been found in this part of the continent, we may reasonably conclude that it was once their proper abode, and zoologically connected with the southern division. What might have been its condition then, and what are the changes that have since occurred to have caused the present diversity of the two faunas, are inquiries that force themselves upon our consideration. That this diversity has been produced by external physical causes, such as change of climate, and modifications of the earth's surface, can scarcely be doubted; for no other reason can be assigned why a living typical representation of these extinct species, should not still be found north as well as south of the Mexican gulf.

That the geographical distribution of faunas has changed since the opossum lived in the British isles, and the mastodon was indigenous to both North and South America, are interesting facts to be accounted for in the adaptation of the nature and habits of animals to the external circumstances in which they are placed. Such an adaptation furnishes the reason of the limitation of the present congeners of our species to their South American locality. And we have only to suppose an assimilation of conditions between the two parts of the continent, and perhaps the substitution of an unbroken connection by means of the continuation of the table lands of Mexico, or the Carribean Islands, in order to produce a similar correspondence between our present and extinct

faunas.