An account of the Quaternary formations of Alabama may be found in Eugene A. Smith’s “Report on the Geology of the Coastal Plain of Alabama.” This was published in 1894, and the part pertaining to the Pleistocene is found on pages 28 to 65. Along the coast Smith recognized the presence of a formation which he called the Biloxi. The upper part of this was regarded as belonging to the Recent, while the lower portion was thought to be the equivalent of Hilgard’s Port Hudson, those deposits numbered 1 to 4 in the section shown on page [387], under Geology of Mississippi. The thickness of the Port Hudson is given as about 100 feet. Borings revealed the presence of shells and lignitized wood.
Along the rivers which traverse the Coastal Plain are found three terraces. The first or lowest is that which is subject to annual overflow. The second terrace, “the second bottom,” occurs along most of even the smaller streams of the Coastal Plain. It may be as much as a mile wide. The height above low water may vary from 10 to 15 feet in the lower courses of the rivers to 60 feet farther up stream. Near water-level a blue clay is frequently found which contains stumps, roots, and other remains of vegetation, often well preserved. Smith concluded that this second terrace was the substantial equivalence in time to the Port Hudson.
Smith presents a geological section taken along Black Warrior River, in Hale County, 150 miles above Mobile. The section included about 50 feet. As caving went on, stumps and logs were frequently brought into view. Similar sections were found on Coosa River, above Montgomery, and on Alabama River, 50 miles above Mobile.
The third terrace is found at elevations of from 50 to 100 feet above the second. It is sometimes 3 miles or more in width.
In his paper on the Citronelle formation (Prof. Paper U. S. Geol. Surv., 98, pp. 167–208), Matson discusses briefly (pp. 189–190) the Pleistocene of the area studied by him. This extends from the western end of Florida to Mississippi River. Here he recognized four terraces, from the youngest to the oldest, the Pensacola, the Hammond, the Port Hickey, and the St. Elmo. The St. Elmo merges into the Natchez formation, which Matson, quoting Chamberlin and Salisbury, regarded as sub-Aftonian. The Port Hickey terrace is stated to take its name from a locality on the Mississippi River where the typical materials of the Port Hudson formation are exposed. The Port Hickey terrace may, as suggested by Matson, be of post-Iowan age. Naturally, these correlations require confirmation.
Berry has described fossil plants (Amer. Naturalist, vol. XLI, pp. 689–697; Amer. Jour. Sci., ser. 4, vol. XXIX, pp. 387–398) which were found along Chattahoochee River, not far below Columbus, Georgia; on Warrior River, up to 356 miles above Mobile. Pleistocene deposits must occur along all the larger streams still farther north, and these deposits will yield in time bones and teeth of vertebrated animals.
Notwithstanding the considerable area of Pleistocene deposits discovered in Alabama, the number of species of vertebrates met with is remarkably small. On page [40] is recorded the finding of Megalonyx jeffersonii somewhere about Tuscumbia. At Newbern, Hale County, have been found an incisor tooth of a horse (p. [200]) and a molar of a bison (p. [264]). At Bogue Chitto, Dallas County, have been collected Equus leidyi (p. [200]), Mammut americanum, and Elephas imperator. The last species indicates that the deposits probably belong in the Aftonian. The writer knows of no other localities in the State where vertebrate fossils of the Pleistocene have been obtained.
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).