(See

sandstone than the rest, but the beds all alternate with shale. pl. 4.) A few miles farther south the small creeks show an even more sandy zone about 30 feet above the base of the formation. On Brandywine Creek the Bedford is only 65 feet thick, the basal 50 feet being nearly all blue shale, upon which lies 7 feet of massive sandstone and 9 feet of alternating shale and sandstone, with the Berea directly above. On Chippewa Creek the sandstone is much lower, more in the position of the Euclid lentil, and the top of the formation is red shale.

In strong contrast to these stand the sections farther west, of which those on Skinners Run and the Rocky River will serve as examples. On Skinners Run the Bedford is about 90 feet thick. The lower 25 feet consists chiefly of black shale, containing many irregular bands and lenses of blue sandstone, large concretions, and much marcasite. The beds are greatly disturbed. The sandstone beds decrease laterally to thin sheets of sandy material that may wholly pinch out within several yards. Vertical shoots run off from these beds along joint cracks and much resemble narrow dikes of igneous rock, but the material in them is a mixture of sand and marcasite, the marcasite in many places in considerable masses. The shales dip in all directions and show numerous small folds and faults, but none of these disturbances involve a great thickness of the rock, and the overlying and underlying shale is not affected. (See pl. 5.) These conditions indicate that the disturbance took place at the time of deposition and was probably due to the currents that brought in the sands. Above this black shale lies 20 feet of blue shale and flags succeeded by about 50 feet of soft red shale.

The Rocky River section is very similar to this one, the Bedford having a thickness of about 80 feet. The lower 25 feet consists of black shale, with a blue band midway, and at the top and bottom a bed of calcareous sandstone that contains Bedford fossils. Above lies 15 feet of blue shale, capped by 40 to 45 feet of soft red shale.

The thickness of the formation within the district ranges from 40 to 110 feet. The greater part of this difference is due to irregular wearing away of the upper beds by the currents that brought in the sands of the Berea formation.

Fossils. Most of the Bedford shale is barren of fossil remains, but in most sections rather abundant fossils may be found in the basal few feet. In these barren shale formations search for fossils is most likely to meet with success just above and just below the black Cleveland shale. The best localities for collecting Bedford fossils in the district are in Tinkers and Brandywine creeks, where they occur in soft shale and in hard concretions, and in the branches of Euclid Creek, where they occur in somewhat calcareous, sandy shale. In the soft shale many shells are present, but they are all crushed.

In

the sandy shale the fossils have kept their shape better, but the shell is gone. Very few are found in the sandstones. They would be plentiful at Cleveland if the base of the formation were well exposed, and large collections may be made from artificial excavations, such as the new Baldwin Reservoir.

The fauna has long been known but has never been thoroughly studied and described. As the bulk of the forms are of undescribed species, only a very imperfect list of them can be given. The pelecypods are chiefly represented by species that have a strong likeness to Devonian (Hamilton) forms. Similar forms are, however, found in the undoubted Mississippian elsewhere. The brachiopods do not as strongly suggest the Devonian.

Several ostracodes occur; also crinoids, too badly preserved to be

determinable; and rarely remains of fishes. One specimen of a hexactinellid sponge has been found. has been found. Near the base of the formation, on Mill Creek, numerous specimens of Lycopodites are found in a single layer.

The basal, fossiliferous layer on Euclid Creek is a hard sandy calcareous shale, and the fauna shows a quite different expression there compared with that in the soft shale at Cleveland and Bedford. The species are the same but differ much in abundance in the two localities, a difference which seems certainly due to the contrasted conditions of sedimentation in the two places.

Break at base of Bedford shale.-At the base of the Bedford shale in many sections is the zone described above, of differing thickness, which consists of reworked black shale from the Cleveland below. This zone is more likely to be present where the basal Bedford is sandy than where it consists of soft shale. The greatest known thickness of this zone is on Skinners Run, but nearly all the sections at and west of

Cleveland show some such material. At other localities-Tinkers and Brandywine Creeks, for example-where the Bedford begins with soft shale, no reworked black shale is shown, but instead a very sharp contact and the basal blue shale is a compact bed that is composed in very large part of shell fragments in a mud matrix. Among the fragments are many whole shells of invertebrates that evidently lived on the bottom composed of the fragments. A considerable pause in deposition is indicated, during which the fauna came in and lived for a considerable time in clear water, the shells being broken up and accumulating on the bottom. The writer has failed to discover, however, any evidence that the sea withdrew and land conditions prevailed during this interval, though it is believed that such were the conditions between the Chagrin and Cleveland epochs. Deposition was interrupted before the Bedford shale was laid down, but the interruption was unaccompanied by emergence.

CARBONIFEROUS SYSTEM

By H. P. CUSHING

MISSISSIPPIAN SERIES

BEREA SANDSTONE

Definition. The Berea sandstone was named by Newberry from the village of Berea, which is situated on this formation and where the rock has been much quarried for many years. It is here a coarse sandstone formation with a general thickness of 60 feet but becomes locally much thicker. Many layers are cross-bedded, many are ripple marked, and the lower part of the formation is thicker bedded and more massive than the upper.

Distribution and occurrence.-The Berea is the lowest persistent formation in the district that strongly resists erosion. It owes to this quality its position as the capstone of one of the terraces of the escarpment that overlooks the Erie Plain. East of the Cuyahoga it has an average thickness of 50 feet and its belt of outcrop is about half a mile wide; it forms a prominent terrace with a somewhat irregular margin along the 900-foot contour, fronting Lake Erie. Similar terraces are found on both sides of the Cuyahoga Valley. West of the Rocky River the formation thickens and its altitude diminishes; hence the breadth of outcrop increases to several miles.

The chief outcrops of the Berea, as of the other formations, are along the streams. The principal streams flow in shallow valleys of slight descent across the formation and fall over its northern edge into gorges whose walls are shale below and sandstone above. The weak shales are rapidly eaten back, and many sandstone ledges overhang their support. These ledges eventually become undermined, and large blocks break off and work their way down the banks and clog the stream. Such blocks are particularly abundant on Chippewa Creek. Besides the creek exposures the Berea is exposed in many more places in the interstream areas than most of the other formations,

because of its resistance to erosion. Outcrops are especially numerous along its escarpment fronts. It has also been exposed in very many artificial openings, such as quarries and railroad and road cuts. Character and thickness.-In this district the Berea is composed chiefly of medium-coarse pure quartz sand, loosely cemented into what is known as a clay-bond sandstone. The cementation is nowhere complete and differs considerably in closeness from bed to bed, so that the rock as a whole is rather porous and is heavily charged with water underground. Some layers are very slightly cemented. The mason finds the rock easy to cut and dress. The usual color is light gray, but some beds are specked with yellow-brown, and in some localities much of the rock is of this color. Over much of the district the formation can be separated into a lower division made up chiefly of thick, massive beds and an upper division of thin beds. Crossbedding is a prominent feature nearly everywhere, and locally at least half the thickness possesses this character. (See pl. 6.)

Under cover gray is the prevailing color of the rock, with the iron in the form of pyrite; above the ground water the pyrite has oxidized and stained the rock light or deep brown, according to the amount present. Many beds are ripple marked; some are slightly pebbly, with all the pebbles of quartz; some contain a few clay-iron concretions; and rarely nodules of soft, compact clay occur, evidently deposited as clay balls by the currents that transported the sand.

The underground water in the formation is confined there because of impervious shales above and below; hence many springs issue wherever the base crops out. The spring waters are likely to be mineralized; many deposit limonite, a less number are strongly sulphurous, and at several localities (Brandywine Creek, Tinkers Creek) the water is so strongly charged with calcium carbonate that it has formed considerable deposits of travertine at the base of the sandstone.

The formation ranges in thickness from as little as 5 feet (Boston Mills) to as much as 150 feet (Berea) within the area shown on the map and passes both those limits in near-by territory. Locally at Akron it is entirely absent, and at Amherst it is at least 225 feet thick. In many places great variation in thickness is shown within a short distance, owing to irregularity of its base. This feature is much more conspicuous in the Berea quadrangle than in the Cleveland quadrangle.

Fossils. The Berea sandstone in places contains plant fragments in abundance, especially in the upper part of the formation, but only at a few localities does it contain animal remains. At Cleveland the surface of one bed of the stone is a mass of the plant fragments. The plant tissue has usually been altered to a thin film of black, coaly material. Here and there recognizable leaves of plants are found, such as Annularia longifolia?, long ago reported by Newberry from Bedford and frequently found since.

Many specimens of a single species of paleoniscid fish, Gonatodus brainerdi, have been found in the quarries at Chagrin Falls, and rarely single specimens have been forthcoming elsewhere, as at Berea, Newburg, and Independence. The quarries at Chagrin Falls are in the upper, thin-bedded portion of the formation, and the fossil fishes are abundant on the surface of one particular layer and there only.

Very rarely single specimens of marine brachiopods are found in the upper, thin beds of the formation. The writer has seen three

FIGURE 4.-Contact of Berea sandstone on Bedford shale in railroad cut in Newburg Township, Cuyahoga County. Scale, 1 inch=30 feet

or four. All were badly worn and broken and appeared as if they had undergone much transportation by waves or currents.

It is thus seen that the fossils of the Berea in northern Ohio are not marine forms, and their evidence aids in the determination that the Berea here is not a marine formation.

Break at base of Berea sandstone.-In nearly all sections the Berea rests on the Bedford shale with prominent erosional discordance. Wherever good exposures of the contact occur, it is seen to be irregular, in many places highly so. The upper surface of the Bedford has been considerably eroded by currents, and the eroded channels have

Feet

-50

FIGURE 5.-Berea-Bedford contact in cut on the Belt Line Railroad 2 miles southwest of Brooklyn, showing a Berea channel more than 30 feet deep cut in the shale

been filled with Berea sand. Most of these channels are shallow but deep ones occur, and these are largest and most abundant in the district west of Cleveland. (See pl. 7.)

The minor irregularities of the base are well shown in a long cut of the Pittsburgh & Lake Erie Railroad high on the east slope of the valley of the Cuyahoga east of Willow. The exposure is no longer very satisfactory, owing to the rapidity with which the Bedford shale decomposes and becomes covered with vegetation, yet it still shows the irregular base of the sandstone. (See fig. 4.)

One of the larger channels is sectioned by a deep cut along the Belt Line Railroad 2 miles southeast of Brooklyn, near the west