B. SHARPSVILLE SANDSTONE ON BRANDYWINE CREEK AT LITTLE YORK Shows the sandstone of the upper part of the formation and the upper layers of the alternating shales and flags below.

BASAL PORTION OF SHARON CONGLOMERATE IN QUARRY AT SCOTLAND, CHESTER TOWNSHIP, GEAUGA COUNTY
View looking north. Exposure consists chiefly of conglomerate but with sandstone above. Cross-bedding shows well at right.

View looking east.

VIEW IN ROAD CUT A SHORT DISTANCE NORTH OF THE QUARRY SHOWN IN PLATE 9
Shows a thickness of 12 feet of somewhat higher beds: sand

trict. In the Chagrin Valley region, a few miles to the east, the Sharon rests on the upper part of the Orangeville shale, only 100 feet above the top of the Berea, and the Meadville and Sharpsville are absent. A little farther east the Meadville and Sharpsville reappear, and the interval between the Berea and the Sharon steadily increases eastward. Southwest from Cleveland this interval also becomes greater, and in Medina and Wayne Counties, within 25 miles of the south margin of the district, two additional formations, the Black Hand and the Logan, come in above the Meadville, and the interval between the Sharon and the Berea has expanded to about 1,000 feet, ten times its thickness in the Chagrin Valley.

The surface on which the Sharon rests also shows local irregularities, the conglomerate filling small channels cut in the underlying beds, of the usual type of the channels at the base of the Berea sandstone.

QUATERNARY SYSTEM

By FRANK LEVERETT

PLEISTOCENE SERIES

GENERAL FEATURES

As the Cleveland district lies within the glaciated region of North America its indurated rock formations are mantled more or less completely by glacial deposits, consisting of till or boulder clay and associated beds of sand and gravel. (See pl. 21.) A part of the district was for a time covered by the waters of glacial lakes, which were held between the retreating ice border and the divide that now separates the St. Lawrence or Great Lakes drainage from that of the Ohio River. At the shores of the glacial lakes ridges of sandy gravel were formed, and on their beds deposits of sand and silt were laid down. In the glacial epoch there were at least four distinct stages of glaciation, separated by intervals of deglaciation, in which the ice sheets withdrew. Each of these glacial stages is marked by a deposit of glacial drift, and the intervals of deglaciation are marked by soils and weathered surfaces of the several drifts. The oldest drift carries different names in the several parts of the glaciated region. It is called Jerseyan in the part east of the Alleghenies, and this name would probably apply in the Cleveland district, as it embraces drift that covered the district between the Alleghenies and Mississippi Valley as well as that in the district east of the Alleghenies, both laid down by ice from the Labrador part of the ice sheet. In the district west of the Mississippi the oldest drift has been called sub-Aftonian, pre-Kansan, and Nebraskan; the second is generally known as Kansan drift; the third from the Labrador part of the ice sheet, Illinoian, the third from the Keewatin part, Iowan; and the drift of the latest glacial stage is called the Wisconsin.

PRE-ILLINOIAN DRIFT (KANSAN?)

48

An old drift is exposed in northwestern Pennsylvania a outside the later drifts, but its relation to the Jerseyan drift remains to be determined. Its degree of erosion and weathering seems to be about the same as that experienced by the Kansan drift and less than that displayed by the Jerseyan. The glaciation that laid down this drift probably covered the Cleveland district, but its drift in this area is buried beneath that of later glacial stages, the Illinoian and Wisconsin, which are well displayed here. This ice invasion seems to have crossed the Erie Basin from north to south, whereas the Illinoian and Wisconsin invasions each had an axial movement lengthwise of the Erie Basin. It was probably this glaciation that brought in copper ores from the Lake Superior Basin, now found in the drift of central and northern Ohio. There may be remnants of the resulting drift in the Cleveland district below the level of the streams and in the Erie Basin. The data afforded by borings along the Cuyahoga Valley throw very little light on the question of the presence of pre-Illinoian drift. In none of the deep borings has a buried soil been reported. The drillers report the occurrence at various depths of a blue puttylike clay, gumming badly on bits, which is interbedded with more stony clay. The thickness of the soft clay beds is 25 to 30 feet or more, and there are two or three such beds in some of the wells. These beds appear to be ponded-water deposits rather than alluvial material, and they can scarcely be cited as evidence of interglacial stream work. The excavations for the Cleveland waterworks tunnel were reported by Newberry to have been in a pebbly blue clay that contained striated rocks and thus differed from the nearly pebbleless clay exposed in the ravines in the southern part of the city and in places along the lake shore. These excavations were carried in places to a depth of more than 100 feet below Lake Erie and reached the bedrock. They may therefore have passed through the oldest drift. A boring made by the Standard Oil Co. at the mouth of Kingsbury Run, in Cleveland, was reported by Newberry to have struck rock at a level of 228 feet below the surface of Lake Erie. In a depth of 238 feet the drill section shows 222 feet of blue clay and 16% feet of sand and gravel in eight separate beds, each only a few inches thick. The great preponderance of clay characterizes nearly all the borings in the Cuyahoga Valley. Some of the borings, as indicated in the discussion of the bedrock surface (pp. 21-24), penetrated nearly to sea level before striking rock.

The exposed part of the pre-Illinoian drift in northwestern Pennsylvania varies greatly in constitution, being governed largely by the

4a Further study of the pre-Wisconsin drift in northwestern Pennsylvania since the above was written has led Mr. Leverett to regard it as of Illinoian age.-W. C. Alden.