nature of the drainage near the ice border. Where the ice caused a ponding of water in valleys that drained toward it a clayey drift was laid down, but where the water was free to escape from melting ice the drift is loose textured because of partial removal of the fine material. In the Cleveland district there was probably a general ponding of water along the ice border, as all the streams drained toward the ice, so that clayey drift is to be expected. What little sand and gravel are present seem likely to be referable to the action of water under hydrostatic pressure within the ice sheet rather than to free drainage outside.

As the ice movement that brought in copper ores appears to have crossed the Erie Basin in a north-south direction, it may have produced the north-south striae in northern Ohio and on islands in the western part of the Erie Basin noted by Newberry, Gilbert, and Winchell, as reported by Newberry," who says that the glacial marks that have a nearly north-south trend are nearly obliterated by the stronger, fresher, and more numerous grooves whose bearing is nearly east-west.

ILLINOIAN DRIFT

The Illinoian ice sheet is the earlier of the two that moved westward through the Erie Basin and spread southward into Ohio. In the eastern part of Ohio its southern limit is nearly coincident with that of the latest or Wisconsin glaciation, but in central and western Ohio (pl. 18) it extended farther south than the Wisconsin ice. The Illinoian drift is exposed in a narrow strip outside the later drift from a point near Mansfield southward along the west edge of the Muskingum drainage basin to Ross County and thence southwestward to the Ohio River in Adams County. It nowhere extends far beyond the Ohio River. It reaches about 10 miles beyond the river opposite Cincinnati and about the same distance near Bedford, Ky.

In the Cleveland district the Illinoian drift is exposed along the shore of Lake Erie east of the Cuyahoga River at many points, and it is slightly exposed where the old Rocky River came into the lake west of its present mouth. Exposures where recent excavations had been made north of Collinwood, examined by the writer in 1920, show a very hard blue till thickly set with small pebbles and traversed by joints and deeply weathered seams that are oxidized to a deepbrown color. This till is about as solid as frozen earth, and its removal by the pounding of the waves of Lake Erie is about as slow as that of the shale formations along the shore west of the Cuyahoga. In places the entire lake bluff is composed of fresh and easily excavated till, referable to the latest, or Wisconsin glaciation. In places there are overlying lake deposits. This part of the shore, therefore, affords interesting sections for study and comparison of both drifts.

Newberry, J. S., Geology of Ohio, vol. 2, p. 10, 1874.

The Illinoian drift probably forms a considerable part of the filling in the ancient Cuyahoga and Rocky River valleys, but like the pre-Illinoian drift it has not been fully separated from overlying drift of later age.

POST-ILLINOIAN LOESS

Where the Illinoian drift is exposed outside the limits of the Wisconsin drift in Ohio it is covered by a thin deposit of silt loam known as loess, which was laid down by the wind.. That this loess deposit is much younger than the Illinoian drift is known from the fact that the surface of that drift had become greatly eroded and weathered before the loess was laid down. The loess is of pre-Wisconsin age, for it occurs beneath the Wisconsin drift in southwestern Ohio. The loess may have extended over northern Ohio, but no exposures have been noted within the Cleveland district. Its thickness in central Ohio is usually less than 10 feet. It is dark brown and seems to have been completely leached of its calcareous material. Molluscan remains have been noted in buried portions of the loess under Wisconsin drift in southwestern Ohio, but none have been observed in the part outside the Wisconsin drift, perhaps because they have been leached

out.

LATEST OR WISCONSIN DRIFT

General features. In the latest or Wisconsin glaciation the limit of the ice in eastern Ohio was between 60 and 75 miles south of the shore of Lake Erie (pl. 18), which was beyond the divide between the Erie drainage and the drainage to the Ohio River. The water from the melting ice therefore had free discharge southward along various lines to the Ohio. The valleys of these streams are filled for long distances with sand and gravel that consist of the same rock materials as are found in the glacial deposits and that are very different from the formations bordering the streams.

The edge of the drift has a general east-west course from the Pennsylvania line to the vicinity of Mansfield, Ohio. It there turns abruptly southward (pl. 18) because of an extension of the ice into the Scioto Basin and runs along on or near the divide between the Scioto and Muskingum Rivers to Ross County, keeping a few miles farther west than the edge of the Illinoian drift in this interval. From Ross County its general course is westward through the southern part of western Ohio. It comes within 12 miles of the Ohio River near Cincinnati, and it passes into Indiana directly west of Hamilton.

When the ice sheet had its greatest extension it was so thick that the underlying basins and ridges were wholly concealed by it, but as it became reduced in thickness from melting, the ridges and highlands became uncovered. As a result the edge of the ice took on a lobelike form. One of the lobes occupied the Grand River Basin in eastern Ohio (pl. 18 and fig. 8), and the ice spread from this basin

toward the highlands on the east, south, and west. At that time the Cleveland district was being overridden by ice that was moving in a direction east of south toward the same highlands over which the Grand River lobe was spreading on its west border. There was a coalescence of this ice with that of the Grand River lobe for a few miles south of the shore of Lake Erie, but a great reentrant angle between the two masses of ice soon developed on these highlands. The water from the melting of the ice then issued into this angle and found a southward egress through the lowest places among the ridges and hills into the drainage channels that led to the Ohio River. The ice border stood so long on certain lines that morainic belts developed. These belts indicate how the ice border became changed from its general east-west course to the much more sinuous course around the basins and over the intervening highlands.

At a certain stage in its retreat the ice that moved across the Cleveland area came to have its border on the present divide between the St. Lawrence and Mississippi Basins, at the site of the city of Akron. At that time there issued from it a great volume of water, which flowed southward across this divide into the drainage tributary to the Muskingum River near Massillon. Its course is marked by a welldefined river channel, which is not now occupied by a stream. The head of this channel at Akron is about 390 feet above the level of Lake Erie, or 963 feet above sea level. Moraines showing the position of the ice border at that time extend into Akron from the east and west and pass the head of this channel.

Up to this time the water from the melting ice had an outlet to the south, and the moraines are made up largely of loose-textured drift, from which a considerable part of the fine detritus that had been contained in the ice was carried by the outflowing streams. When the ice border had retreated to a position within the present Lake Erie drainage basin, the water could not escape freely but became ponded, especially in the Cuyahoga Valley, and the ponding reached a sufficient height to give an outflow across the divide. Under these conditions the fine material contained in the melting ice was not carried away but was deposited where the ice melted. As a result the glacial deposits let down on this slope of the Erie drainage basin are very largely of a clayey character, though in places sand and gravel are found underneath a surface deposit of clayey drift. The moraines that were developed where the ice front halted in the course of its retreat are very weak and in places are difficult to trace. Parts of their lines, however, are sufficiently well defined to show the sinuosity of the ice border, with recesses on the uplands on each side of the Cuyahoga Valley and a great protrusion of ice into the valley.

The part of the Cleveland district that was uncovered earliest seems to lie in Richfield Township, Summit County, and neighboring parts

of Hinckley Township, Medina County, and Royalton and Brecksville Townships, Cuyahoga County. It is a very high area, much of it between 1,200 and 1,300 feet above sea level. At about the same time a narrow strip of upland along the east border of the Cleveland quadrangle became free from ice.

The first-named area is limited on the east, north, and west by the Defiance moraine, there having been a great recess in the ice border here when that moraine was forming. The second area lies east of the moraine in a recess east of the Cuyahoga Valley. There are a few places in the southern part of the Cleveland quadrangle, outside the Defiance moraine, where the drift surface is somewhat more undulating than the ordinary ground moraine-for example, immediately west of Furnace Run along the south edge of the Cleveland quadrangle and around the corner of Medina and Summit Counties. There is also a group of knolls south of the county line 11⁄2 miles west of this corner. Between these knolly spots the surface is generally smooth, like the ordinary ground moraine. There is a strip of knolly drift in northeastern Richfield Township about 2 miles long and a quarter of a mile wide, formed by a lobe of ice that lay in the Cuyahoga Valley. It stands about 100 to 150 feet higher than the border of the neighboring part of the Defiance moraine, which runs parallel to it less than a mile to the east. No continuation was found west of the Brecksville road. A well on this strip just east of that road and others midway of its length have reached depths of 50 feet or more without striking bedrock. Although it is not definitely connected with the knolly spots above noted, this strip is like them in being older than the Defiance moraine.

Aside from the places where the drift is aggregated in knolls, it is generally but a few feet to bedrock in the part of the Cleveland quadrangle outside the Defiance moraine. The drift is generally a clayey till of fresh appearance. On the east side of the Brecksville road north of Furnace Run is an exposure of rusty gravel which may be of pre-Wisconsin age, but no other exposures of old-looking drift

were seen.

Defiance moraine.-The Defiance moraine, named from the city of Defiance, in northwestern Ohio (fig. 8), enters the Cleveland quadrangle from the east a short distance south of the northeast corner. It is here separated into two distinct strips of knolly drift, between which is a narrow smooth strip. The two knolly strips become united about 11⁄2 miles north of Randall. The moraine passes over a prominent sandstone ridge, 1,200 to 1,240 feet above sea level, in the northeastern part of the Cleveland quadrangle. On the west slope of this ridge the moraine, in a short distance, drops below the 1,100-foot contour. For about 4 miles north of Bedford the moraine controls the course of a northern tributary of Tinkers Creek, which follows the

outer border of the moraine southward. On crossing Tinkers Creek, south of Bedford, the moraine follows its south bluff southwestward for 2 miles and then takes a southward course past Northfield to the limits of the Cleveland quadrangle. The south end of the morainic loop is only a mile farther south, at Peninsula. The moraine there crosses to the west side of the Cuyahoga River and doubles back to the north, into the Cleveland quadrangle. It crosses from Summit into Cuyahoga County near the northeast corner of Richfield Township, takes a northwest course to Chippewa Creek at Brecksville, and follows the south side of that creek to the west line of Brecksville Township. The moraine is ill-defined for about 2 miles west of this line but becomes more definite near the headwaters of Chippewa Creek, about 11⁄2 miles southwest of Walling Corners, and follows the general course of the road that leads from Walling Corners to North Royalton, being nearly on the brow of the Pottsville escarpment. It turns southward near North Royalton, and for 3 miles determines the southward course of the East Branch of the Rocky River, which follows its outer edge. In Hinckley Township this branch of the Rocky River turns to the north, and the moraine crosses its valley near Hinckley village, about a mile south of the south edge of the Cleveland quadrangle. Its course is thence westward through the southern part of the Berea quadrangle for about 6 miles before it. passes into the Medina quadrangle. The main part of the moraine lies south of Big Brook, in Hinckley Township, but in the vicinity of Bennetts Corners there is an inner ridge along the north side of Big Brook, which is traceable from the area near the head of the brook eastward for 2 miles.

The course of the Defiance moraine is controlled very largely in the Cleveland district by the topographic conditions, there being a great protrusion southward into the Cuyahoga Valley, forming a lobe about 8 miles long, which tapers from a width of 6 miles at the north to about 3 miles at the south end. The uplands on each side of the Cuyahoga Valley cause pronounced reentrants in its course. The moraine is about 950 feet above sea level at the end of the lobe in the Cuyahoga Valley and rises northward on each side of the valley to more than 1,200 feet at the reentrant angles. On the east side it reaches an altitude of fully 1,240 feet, and on the west side, north of North Royalton, the measured altitude of one point on it is 1,265 feet. On the high land west of the East Branch of the Rocky River, in the southeastern part of the Berea quadrangle, it is slightly less than 1,200 feet, although in northern Brunswick Township the moraine passes south of a ridge of Sharon conglomerate which is 1,220 feet high. It is only about 900 feet above sea level in the valley of the East Branch of the Rocky River near Hinckley village.

The thickness of the drift in this moraine is somewhat greater than on the level tracts on each side, the difference corresponding nearly

.