MARYLAND AND DISTRICT OF COLUMBIA.

For obvious reasons the Pleistocene geology of the District of Columbia is considered in connection with that of Maryland. This region is of especial interest, because of the long time and the care which has been bestowed on it by geologists and because the conclusions reached have been applied to the geological study of States both toward the north and toward the south.

The most complete exposition of the Pleistocene geology of the region is to be found in the volume of the Maryland Geological Survey entitled “Pliocene and Pleistocene,” published in 1906. The geological treatise itself was written by George Burbank Shattuck and is illustrated by many maps and text-figures. Included in this is a bibliography of the subject which occupies 17 pages. There is a chapter by W. B. Clark, Arthur Hollick, and F. A. Lucas, on the interpretation of the palæontological criteria; another by F. A. Lucas on the mastodons and the elephants. The Pleistocene mollusks found in the State, 40 species, were described and figured by W. B. Clark; while the plants, also nearly 40 in number, were described and figured by Arthur Hollick.

The history of the development of our present knowledge of the geology of Maryland and the classification of its formations up to 1906 is given by Shattuck in the volume just cited (pp. 25–40). This geologist recognized in the superficial deposits of the State five formations (fig. 15). These are, beginning with the oldest, Lafayette, Sunderland, Wicomico, Talbot, and Recent.

Fig. 15.—Diagram showing the ideal arrangement of the supposed terraces in the Maryland Coastal Plain. From Shattuck.

The Lafayette is regarded as having been laid down during the Pliocene. The Sunderland, Wicomico, and Talbot form three terraces, of which the Sunderland is the oldest, most elevated, and farthest away from the larger bodies of water. It is composed of clay, peat, gravel, and boulders supposed to have been brought in by the ice. The coarser materials appear to occupy usually the lower parts of the formation. The elevation near Washington is about 200 feet, but southward it descends gently, until in St. Mary’s County it is only about 60 feet. The thickness varies from about 80 feet to nothing. According to Shattuck, at the time of deposition of the Sunderland the coast was depressed to an extent of about 200 feet, so that its materials were laid down either in salt water or in that of wide estuaries. No deposits belonging to it have been found in the eastern peninsula. In the western peninsula considerable areas are recognized along the Potomac up to Washington and along the Patuxent and Chesapeake Bay to Baltimore and Elkton. Except in the southern part of this peninsula, the Sunderland is found only in widely separated patches. No marine organisms are known to have left their remains in the Sunderland, but forest trees of a number of existing genera and several extinct species have been described by Hollick in the volume cited.

The Wicomico formation is described as occupying a large portion of the central and higher parts of the eastern peninsula; in the western it forms a narrow and often interrupted fringe around the Sunderland. North of Washington and Annapolis it occurs only in patches. Its materials are very similar to those of the Sunderland. Its greatest elevation is about 100 feet above sea-level, and this, according to Shattuck’s view, marks the amount of depression of the land at that time. The thickness may be as much as 70 feet, but is usually much less. No marine fossils proper to the period have been discovered in the deposits, but at a point in Prince George’s County plant remains have been found in a deposit about 20 feet thick.

The Talbot formation forms a fringe, sometimes of great width, sometimes narrow or interrupted, along all the large bodies of water in this State and in Delaware. It is the lowest of the terraces. The greatest elevation is about 45 feet; the thickness does not exceed 40 feet. The materials noted are those of the other two formations—clay, peat, sand, gravel, and ice-borne boulders. At several points along Chesapeake Bay and on the lower part of Patuxent and Potomac rivers, deposits containing plant remains have been discovered, including pines, cypress, hickory, beech, elm, and black locust. In contrast with the other formations, the Talbot has furnished many marine fossils, mostly mollusks; but in all cases the localities are close to the present coast.

The writer does not accept the theory that the materials forming what have been called the Sunderland, Wicomico, and Talbot terraces have been to any great extent laid down in the sea. Some part of the Talbot, that lying near the present coast, has undoubtedly had such an origin. Nor has the Coastal Plain suffered, so far as is determinable, any such amount of depression as the theory mentioned requires. The materials of the Sunderland and Wicomico have, in the writer’s opinion, been brought down by rivers whose beds lay at levels nearly as high as those of the real or supposed terraces. When the Talbot materials were laid down, the rivers and estuaries of the coast had been cut down nearly to their present levels, and this was not long after the beginning of the Pleistocene.

The authors of the submergence theory admit that no satisfactory evidence of the presence of marine organisms, vertebrate or invertebrate, are to be found in the body of the assumed terraces, except again in parts of the Talbot which immediately border the ocean or the great estuaries. It is almost inconceivable that the ocean could occupy the Coastal Plain from New Jersey to Mexico for thousands of years and lay down great thicknesses of clay, sand, and gravel without having left somewhere beds of molluscan shells in such situations that they would have been discovered. While these marine fossils are lacking, there are found on all these terraces from Maryland to Florida and to the Rio Grande an abundance of land vertebrates such as elephants, mastodons, horses, camels, peccaries, and many other forms. Nor do our palæobotanists have difficulty in finding oaks, walnuts, hickories, poplars, etc. On the theory of submergence there are missing all the things that ought to be found and there are met with just the things that would not be expected.

A figure is here reproduced (fig. 15) from the Maryland Pliocene and Pleistocene volume, page 66, with the explanation there accompanying it. The reader may judge for himself whether the sea could occupy the Atlantic coast since Pliocene times without leaving any traces of marine fossils, while at the same time there were preserved in those terraces remains of land animals and land vegetation.

Another section (fig. 16) is reproduced from Folio 179 of the U. S. Geological Survey, the authors of which are G. W. Stose and C. K. Swartz. The uppermost terraces are by these authors supposed to belong to the late Pliocene, the formation formerly known as the Lafayette. These figures suggest that the one set of terraces have some connections with the other set.

Fig. 16.—Section across Potomac River near Big Pool, Maryland. Shows gravel-covered terraces. Folio 179, U. S. Geol. Survey.

Beginning at the southern extremity of Maryland, we notice the occurrence of remains of Mammut americanum at or near St. Mary’s City. Other remains of the same animal have been secured near St. Clements in St. Mary’s County (p. [112]). Both of the localities are situated on territory mapped by Shattuck as Wicomico; but as remarked on page [112], our knowledge of the conditions under which the fossils were found is not sufficient to allow us to say more than that they belong to the Pleistocene. The species existed from early to late Pleistocene and can not be used to determine the age of the deposits.

Along Patuxent River, in Charles County, not far from Benedict, Cope (Proc. Acad. Nat. Sci. Phila., 1867, p. 155) recognized jaws and teeth of Grison macrodon and of Tagassu lenis (p. [220]). Both are extinct species.

According to Shattuck’s map of 1906, this region is covered by the Talbot formation; but inasmuch as the species named were obtained from pits furnishing Miocene marl, one can not be sure that they are not older than the supposed Talbot. It would probably require a search in the land records in order to determine exactly where the objects were found. The presence of Elephas primigenius suggests that this animal had been pushed down here during one of the glacial stages.

Nearly a hundred years ago an elephant tooth (p. [154]) was found somewhere in Queen Anne County, but it would probably be now impossible to determine the locality. In case the elephant tooth was found near Chesapeake Bay, as is very probable, there is no record of any Pleistocene vertebrate having been found in the central and eastern parts of the eastern peninsula.

In the eastern peninsula remains of Pleistocene vertebrates have been recorded from only two localities, Oxford Neck, Talbot County, and an undetermined locality in Queen Anne County. From Oxford Neck, Cope (Proc. Amer. Philos. Soc., vol. XI, 1869, p. 178) reported Elephas primigenius, E. columbi, Cervus canadensis, Odocoileus virginianus, Chelydra serpentina, and Terrapene eurypygia.

At Chesapeake Beach, William Palmer, of the U. S. National Museum, discovered a few remains of Pleistocene vertebrates. One of these is a tooth of an undetermined species of Bison, probably not the existing one. Another species is probably Equus leidyi (p. [189]). Three teeth appear to represent the peccary Tagassu lenis (p. [220]). In 1921, Dr. Adolph H. Schultz, of the Johns Hopkins Medical School, presented to the U. S. National Museum another specimen of T. lenis which he had found at Chesapeake Beach. Inasmuch as the fossils were picked up after having fallen from their resting-place, it is impossible to say to which formation they belonged. In the opinion of the writer, none of the three species indicates a late Pleistocene time.

On the opposite side of the western peninsula, at Marshall Hall, Charles County, there was found long ago a tooth which the writer refers to Equus leidyi.

Coming north into the District of Columbia, we find recorded the discovery of remains of horses and possibly at two different times. According to Darton’s work (Folio 70, U. S. Geol. Surv.), there is some later Columbia laid down along the route of the Chesapeake and Potomac Canal above Georgetown. This would now doubtless be regarded as belonging to the Talbot. It seems to follow that either the Talbot is much older than has been supposed or that some of the extinct horses continued on until a comparatively late time in the Pleistocene.

Within the limits of the city of Washington there has been found a tooth of probably Elephas primigenius at a depth of 35 feet, in the Wicomico formation (see p. [178]). On any theory of the origin of the terraces, the presence of the tooth at that depth in the ground and at that elevation appears to indicate a considerable geological age for the animal. To what extent materials may have been washed down from the surrounding higher land may be difficult to determine.

In Prince George County, near Mitchellville, have been found two teeth of an extinct horse (p. [188]). These are as yet unidentified. They are in the U. S. National Museum, No. 8813.

Near Towson, in Baltimore County, a mastodon tooth has been found (p. [112]); but beyond proving that there is at that locality some Pleistocene deposit, it gives us little information.

In 1920 (Proc. U. S. Nat. Mus., vol. LVIII, pp. 96–109), the writer described a collection of vertebrate fossils, collected in a cave or fissure in limestone at Cavetown, Washington County, by anthropologists from Phillips Academy, Andover, Massachusetts. The following is the list of species that were found in the collection:

Of the 22 species here recognized 12 are extinct. This large number of itself indicates that their time of existence was not recent. Similarly, the presence of 2 species of horses, several species of peccaries, and of a saber-tooth tiger points to a rather ancient period. The writer believes that the assemblage belongs to the Sangamon stage of the Pleistocene.

Fig. 17.—Generalized section across the Allegheny Valley at Parkers Landing, West Virginia, showing various stages of erosion and valley fill. U. S. Geol. Surv. Folio 178.

In Washington County, probably along Lane’s Creek, was found, in digging a mill-race, the skull of a mastodon (p. [112]). Further east, near Clear Spring, and about a mile above the entrance of Conococheague Creek into the Potomac, was discovered a tooth of a mastodon (p. [113]). This had been washed out of some deposit along this creek, probably not far away from where it was found. As Stose has shown (Hancock Folio, No. 179, U. S. Geol. Surv.), along the Potomac and its tributary streams there are extensive Pleistocene deposits of sand and gravel, laid down when the river was as much as 200 feet above its present level. It is probable that such deposits date from the early Pleistocene (fig. 17). A more important locality for Pleistocene vertebrates is that near Corriganville, about 3 miles west of north of Cumberland, Maryland. The cave is in Allegany County, west of Wills Creek and south of Jennings Run, about 0.5 mile south of the village of Corriganville. An account of this locality, with a list of the species determined up to that time, has been published by Gidley (Proc. U. S. Nat. Mus., vol. XLVI, 1913, pp. 93–102). In cutting through a spur of limestone in making a railroad, at a depth of about 100 feet there was exposed a cave or fissure which contained many bones and teeth. Gidley secured some hundreds of specimens belonging to about 35 species. Unfortunately nothing has been published which shows the relation of this cave to the terraces which are found along Potomac River and its tributaries. Through the kind offices of Mr. F. S. Rowe, welfare agent of the Western Maryland Railway, the writer has received from the division engineer, Mr. P. Cain, of Cumberland, a topographic map of Allegany County and a profile of the road extending through the rock cut. From these it appears that the level of the track, at the fissure, is 837 feet above sea-level. This seems, therefore, to be considerably above the highest terrace along the Potomac in that region. It is to be supposed that the fissure was formed long before the animal remains accumulated in it.

In a paper published in 1920 (Proc. U. S. Nat. Mus., vol. LVII, pp. 651–678, plates LIV, LV, text-figs. 1–10) Gidley added to his former list four species of peccaries, as follows: Platygonus cumberlandensis, P. intermedius, Mylohyus exortivus (all new), and M. pennsylvanicus. In another communication he reported also a deer, a wolverine, a beaver, a lynx, a badger, a marten, an eland, and a crocodile or an alligator (Rep. Smithson. Inst. for 1918, pp. 281–287). Many of the identifications are merely provisional.

Provisional list of fossils found near Corriganville.

1. Alligator or Crocodylus sp. indet. 2. Blarina brevicauda?. 3. Vespertilio grandis. 4. Vespertilio sp. indet. 5. Myotis sp. indet. 6. Ursus vitabilis. 7. Ursus americanus?. 8. Canis armbrusteri. 9. Canis sp. indet. 10. Vulpes? sp. indet. 11. Mustela vison?. 12. Gulo luscus?. 13. Taxidea sp. indet. 14. Lynx sp. indet. 15. Mammut americanum. 16. Equus sp. indet. (p. [189]). 17. Tapirus haysii? (p. [204]). 18. Platygonus cumberlandensis (p. [220]) 19. P. intermedius (p. [220]). 20. P. vetus? (p. [220]). 21. Mylohyus exortivus (p. [220]). 22. M. pennsylvanicus (p. [220]). 23. Odocoileus sp. indet. 24. Taurotragus americanus. 25. Ochotona princeps?. 26. Lepus americanus?. 27. Lepus sp. indet. 28. Sciurus hudsonicus. 29. Sciuropterus alpinus?. 30. Marmota monax?. 31. Castor sp. indet. 32. Neotoma sp. indet. 33. Microtus chrotorrhinus?. 34. Synaptomys borealis?. 35. Synaptomys sp. indet. 36. Peromyscus leucopus?. 37. Napæozapus sp. indet. 38. Erethizon sp. nov.

On account of the present unstudied condition of the collection, it is difficult to reach conclusions that are satisfactory. It appears, however, that there are at least 6 hitherto undescribed species, one-fifth of the whole number. Another 6, if at all correctly determined, indicate a wide removal from their ranges of the present day. Lepus americanus now lives well toward the north, coming down to Saginaw, Michigan. Ochotona princeps lives in the Rocky Mountains of British America. Synaptomys borealis is known only from the region about Great Bear Lake, Mackenzie, Canada. Microtus chrotorrhinus has its habitat in Quebec and the northeastern United States. The species of Napæozapus are Canadian in their range, but descend to southeastern Maryland and to North Carolina in the mountains. Sciuropterus alpinus is found from Alaska to Hudson Bay, but descends on the Pacific coast to southern California. This northern habitat of so many supposed species suggests that the fissure received its contents during one of the glacial stages, and this may be the case. However, it is not unlikely that these species and some others are really undescribed ones. One may reasonably expect to find in a fauna containing Equus and Tapirus a much higher percentage of extinct species than Gidley has recorded.

The most remarkable member of the fauna is Taurotragus americanus, a species closely related to the eland of southern Africa (Gidley, Smiths. Misc. Coll., vol. LX, No. 27). Its presence in western Maryland gives a vivid impression of the widely extended journey that some animals have made from one continent to others. The same species has since been found in collections made at Alton, Illinois (p. [339]), and at Kimmswick, Missouri (Proc. U. S. Nat. Mus., vol. LVIII, p. 113).

According to the author’s views, the fauna found at Cumberland, like that of localities in western Virginia, belongs to a time somewhere about the middle of the Pleistocene. Most of the species may be supposed to have lived there during the warm Sangamon stage; others, as the wolverine, at a somewhat earlier or later time when the climate was cooler.