The great extinct dog Ænocyon dirus was first found near Evansville (p. [32]), and the coyote, Canis latrans, has been reported from Boone County. The latter is said to have been found in association with the mammoth (Cope and Wortman, 14th Ann. Rep. Geol. Surv. Indiana, p. 7).
ILLINOIS.
(Map [38].)
As a foundation for a knowledge of the Pleistocene geology of Illinois, the student must take Leverett’s work entitled “The Illinois Glacial Lobe.” This is Monograph XLVIII of the U. S. Geological Survey, a volume of 817 pages, with maps and figures. For a knowledge of the changes which occurred around the south end of Lake Michigan on the retirement of the Wisconsin glacier, see Dr. Frank C. Baker’s work, “The Life of the Pleistocene, or Glacial, Period” (Univ. Ills. Bull. XVII, 1920).
Illinois is eminently a glaciated State, as is to be recognized on Leverett’s plate VI. A little triangle in the northwestern corner, comprising about 600 square miles, and an irregular tract of perhaps 3,000 square miles at the southern end of the State constitute the whole of the unglaciated area out of 56,650 square miles. Two glacial stages are prominent, the Wisconsin and the Illinoian. The first was laid down by the Lake Michigan lobe, which sent its icy mass southwestward as far as Shelbyville. Westward the border moraine extends to Peoria, then north to west of Princeton, then northeast to enter Wisconsin 55 miles west of Lake Michigan. Eastward, of course, the deposits of till and the moraines extend into Indiana. North of the Shelbyville moraine is the Champaign. A more powerful moraine is the Bloomington, which forms a loop through the State, extending from Danville, Illinois, through Bloomington to Peoria, where it appears to have overridden the Shelbyville and thence northward, forming the outer border of the Wisconsin drift area. North of this moraine is located that called the Marseilles, while sweeping around the south end of Lake Michigan into Indiana and Michigan is the Valparaiso system.
South and west of the area of the Wisconsin drift is the Illinoian. At Mount Vernon the border crosses the Wabash and traverses Illinois, striking the Mississippi River at Carbondale. It then follows the Mississippi north to a point above Keokuk, where it enters Iowa. It reenters Illinois between Rock Island and Clinton and extends into Wisconsin.
On Leverett’s map (Monogr. XXXVIII, plate VI) there is indicated in northern Illinois, between the Illinoian and the Wisconsin, a tract supposed to belong to the Iowan; but Alden (U. S. Geol. Surv., Prof. Pap. 106, 1918, p. 173) holds that there is no good evidence that the Iowan extends into southern Wisconsin and Illinois. The supposed Iowan (op. cit., plate III) is mapped as Illinoian.
The glacial stage which preceded the Illinoian is the Kansan. This in Iowa extends eastward to the Mississippi, and one might naturally expect that it would be found underlying the Illinoian east of the river. Leverett (Monogr. XXXVIII, p. 105) presents evidences of its presence in western Illinois. Among these evidences is the presence in Hancock and Adams Counties of another till sheet below the Illinoian and separated from it by a black soil. This Kansan or some other pre-Illinoian till sheet has been found in many places in Illinois (op. cit., pp. 107–118).
Animal remains are not likely to be inclosed in the materials of the moraines or of the intermorainal till; but this is possible. A musk-ox or a hairy mammoth might have died not far away from the foot of a stationary or advancing glacier and its bones might have become incorporated in the moraine. Furthermore, inasmuch as any glacial stage began while the glacier was yet in the far north and ended only when it got back there, many non-glacial deposits belonging to that glacial stage were probably laid down south of it; and it would be difficult or impossible to distinguish these from interglacial deposits. However, it was these deposits which were laid down after the glacial ice had withdrawn, whether glacial or interglacial, which are of more interest to the palæontologist, because in them are to be found the fossil remains of animals and plants.
The last of the interglacial stages, that which immediately preceded the Wisconsin and followed the Iowan, is known as the Peorian. This takes its name from a locality a few miles east of Peoria (Leverett, Monogr. XXXVIII, p. 187). Here the Shelbyville till sheet is underlain by a bed of fossiliferous loess from 8 to 12 feet in thickness. Beneath the loess is fully 100 feet of Illinoian drift. This loess seemed to the geologists who examined it to be a deposit of more recent date than the Sangamon.