Notwithstanding the amount of work done at Bigbone Lick, the geology of the locality, and especially of the bone-bearing levels, is not well known. Most persons who have labored there were interested almost wholly in getting as many bones as possible and then in getting away. Cooper, as cited, published a map of the region and indicated where the excavations had been made up to that time. This map is here presented, redrawn (map [41]). From Cooper’s account it appears that all of the bones had been found within a very circumscribed area, near a number of salt springs. The bones occurred on the surface and as deep as 25 feet. Cooper attributed this variation of depth to the unevenness of the surface, his idea being that the bone-bearing stratum occupied a certain level. He concluded that the valley had been filled up to a depth of not less than 30 feet by unconsolidated beds of various kinds, of which the uppermost was a light-yellow clay. This appeared to have been brought down from the higher grounds by flowing water. In it were found bones of buffaloes and other modern animals. Below this came a thinner layer of darker color, softer and more gravelly, which contained remains of reedy plants and fresh-water mollusks. It is described as being sometimes very thin or even wanting. It was in this layer that the bones, or most of them, were buried. It was itself underlain by a bed of blue clay of a very compact and tenacious kind. Cooper added that this bone-bearing layer appeared sometimes to be embedded in the blue clay.

The next important investigations made at this place, so far as the writer knows, are those instituted by Professor N. S. Shaler in 1868 (Geol. Surv. Kentucky, 2d ser., vol. III, 1877, pp. 196–198; Allen’s “The American Bison,” 1876, pp. 232–236). He reported that he had sent to the Museum of Comparative Zoology at Harvard at least a ton of bones. Immediately at the salt springs Shaler appears not to have been able to discover any order in the disposition of the bones. “It is only at points remote from the springs, where the beds seem to have been formed by a mixture of the creek mud and the waste from the springs, that we find the remains in the order which will enable us to form some opinion as to the succession of occurrence of these animals at this point.” At one place he thought he had succeeded in finding a distinct order of succession. Just where this place was he did not indicate, nor what kinds of deposits were passed through. The depth reached appears to have been only 8 feet. Unfortunately, the great collection made by Shaler has remained unstudied, except the remains of the buffalo (J. A. Allen, “The American Bison,” 1876, with plates).

Shaler thought that the beds of glacial drift did not extend south of Ohio River. The discovery that the Illinoian drift-sheet covers most of Boone County (Leverett, Monogr. U. S. Geol. Surv., vol. XLI, pp. 257–258) throws much light on the history of the locality. It appears rather strange that Shaler did not find rocks of far northern origin at Bigbone Lick. The geologic history appears to be something like this. When the Illinoian ice-sheet crossed the Ohio there was present the predecessor of Bigbone Creek. Inasmuch as the glacial sheet did not remain there long, a rather thin deposit was laid down in the creek. This is probably represented by the bed of blue mud mentioned by Cooper. When the glacier retired, the locality became a swamp covered probably by vegetation and receiving mud and gravel brought there by the stream and washed down from the surrounding hills. Doubtless the salt springs existed then as now and attracted thither elephants, mastodons, and other species. What were all the changes undergone there between the Illinoian and Wisconsin drift stages can not be guessed; but during the latter time, when the Ohio was carrying down vast quantities of detritus, some from the glaciated regions, some from the non-glaciated, its muddy waters were often backed up into Bigbone Creek, as they are sometimes now, and they left there the upper yellow clay described by Cooper, or at least most of it. When the Wisconsin stage had passed and Bigbone Creek was free to work in that valley, erosion began. As the creek was cutting down its bed to the present level it doubtless often changed its position, and in this way produced the irregularity of surface which both Cooper and Shaler mention.

Notwithstanding its widely extended reputation, Bigbone Lick has furnished relatively few species of vertebrates, and there is question regarding the antiquity of some of these. About the presence of Mammut americanum there is no doubt. About the presence of elephants also there can be no question; and the writer is quite certain that both Elephas primigenius and E. columbi occurred there. Undoubtedly Equus complicatus has been collected there; also Boötherium bombifrons, Symbos cavifrons, Bison antiquus, and B. bison; but it is not certain that the remains of the last-named species are not of Recent times. Shaler mentions the presence of Bison latifrons, but he probably had in mind B. antiquus. The type of B. latifrons was found in another creek valley. The occurrence of the Cervus canadensis, Odocoileus virginianus, and Alces americanus is mentioned by Cooper, who stated that he thought he had seen traces of all of them. Shaler was doubtful as to the elk. In Allen’s monograph on American bison, on page 234, Shaler admits the moose. The following is a list of the species which have been reported from Bigbone Lick. References are made to pages where further information is given on the species.

It is proper now to determine, if possible, during which of the Pleistocene stages each of these species lived. It is quite probable that none of the individual animals that have been dug up at Bigbone Lick lived there before the Illinoian glacial stage. To find such, if they have been preserved there, the excavations would have to be carried much deeper. The writer assumes that any of the animals that lived there in the interval between the Illinoian and the Wisconsin stages lived, died, and were buried during the Sangamon stage. Megalonyx jeffersonii may belong to the Sangamon or to the Late Wisconsin, for we know nothing about the depth at which the bones and teeth were secured. Mylodon harlani is not known to have existed anywhere after the Wisconsin, and hence we may refer it to the Sangamon. Equus complicatus also may with certainty be referred to the Sangamon; likewise Tapirus haysii, in case the type was not found in South Carolina. As to the cervids Odocoileus virginianus, Cervus canadensis, Alces americanus, their status is doubtful. They might go back to the Sangamon or have lived there at any time up to and during the Recent. The reindeer is most likely to have existed there during the Wisconsin ice-stage. The fine specimen of Cervalces scotti at Princeton University was found in New Jersey in deposits overlying Wisconsin drift, but it may be taken as certain that the species had existed before the time of the Wisconsin. There is no record of depth, matrix, or associated fossils in the case of the type of this species, which was found at Bigbone Lick. It is natural to refer the two species of musk-oxen to the Wisconsin stage; but there are indications that at least Symbos cavifrons has been found at other localities in pre-Wisconsin deposits. Shaler recorded it as being found near the bottom of his excavation with the horse and with the bison which he called Bison latifrons, but which is Bison antiquus. It and Symbos cavifrons probably belong to the Sangamon.

From the fact that bones of the mastodon and the two species of elephants were found by Shaler in the deeper deposits, it is probable that the individuals represented belonged to the Sangamon or some other pre-Wisconsin deposit; but, inasmuch as all three species lived after the Wisconsin, there seems to be no known reason why some of their bones may not have been buried in the late and superficial deposits at Bigbone Lick. As to the bones of the bear found at this place little can be said.

The numerous remains of Bison bison appear by all accounts to have been found only in the uppermost parts of the deposits. Shaler was of the opinion that the buffalo (Allen’s “The American Bison,” p. 234) had come to the region east of Mississippi River at a very late period, after the disappearance from Bigbone Lick of the elephants, the mastodon, and Symbos. It seems to the present writer that the presence of the existing buffalo east of the Mississippi only after the passing of the Wisconsin ice-sheet is quite certain; but that it came only after the extinction of the great proboscideans is hardly to be sustained. In many localities over the country remains of all three species have been found in swamps overlying the Wisconsin drift. In 1890 (Amer. Naturalist, vol. XXIV, p. 953), Professor Lucien Underwood described a fine skull of the American buffalo which had been found in making a sewer at Syracuse, New York. Underwood stated that it had been found in black muck, at a depth of 10 feet; but Mr. John Cunningham, superintendent of grounds at the university, who saw the place and secured the skull from the laborer who encountered it, told the present writer that the depth was 17 feet. It would seem that that bison had lived on the shores of Onondaga Lake not long after the Wisconsin glacier had withdrawn from the place.

We do not know under what geological conditions the type of Bison latifrons was found; but it pretty certainly came from post-Illinoian deposits, probably Sangamon, along possibly Woolper’s Creek in Boone County. Proboscidean remains have been reported from the Kentucky side of the Ohio in the region of Cincinnati, but it would be hazardous at present to assign them a geological age. The same may be said about the mastodon remains found in digging the canal around the falls, although the low level along the river seems to indicate the Late Wisconsin.

A collection, forming probably two farm-wagon loads, was made several years ago at Bluelick Springs, by Mr. Thomas W. Hunter. The springs having failed, Mr. Hunter undertook to dig down and restore the flow. In this he failed, but he did find great quantities of bones, mostly those of the mastodon, but also of elephants, buffaloes, and a few others (p. [129]). There were about 100 mastodon teeth, many tusks, and large pieces of these; and of these pieces about 20 had been planed off so as to be flat on one or on two sides, as if they had lain in the bottom of a stream and the water and sand had worn them down on one side and then the tusks had been turned over and undergone a planing of the opposite side. Among the bones were two ungual phalanges of Megalonyx jeffersonii (p. [44]), and remains of the elk (p. [243]), and deer (p. [234]). To none of the species found there need one assign a higher antiquity than late Pleistocene; but some might have been older. In Scott County, between Stamping Ground and Georgetown, there has been found, in the bottom of an old sink-hole, a part of a lower jaw with teeth of Tapirus haysii (p. [210]). The time of existence of this animal is to be regarded as lying somewhere back of the Wisconsin glacial stage. With this jaw, Professor Arthur M. Miller sent to the writer some pieces of jaws of Tapirus haysii (p. [210]) which had been found in an old stream-deposit at Yarnallton, Fayette County. From a fissure filled with calcite, at Monday’s Landing, Mercer County, there has been sent to the writer, by Professor Miller, a molar tooth of a horse (p. [202]). Nothing more can be said of this horse than that it is older than the Wisconsin stage. It may be as old as the first interglacial.