and foul bottom waters, however, became stirred and purified by stronger currents than had existed in Cleveland time, and these currents locally stirred up the black mud and relaid it as the initial deposit of the Bedford. With the sweetening of the waters a bottom fauna entered the basin and lived most abundantly where the bottom mud was least stirred by currents. But the organisms were mostly small forms with thin shells that were badly broken up by the moving water. Soon the rate of the coming of mud into the basin increased, and locally stronger currents swept in and deposited great lenses of fine sand. The muddied waters disagreed with the fauna, which dwindled and vanished rather early, so that the waters of the basin during the greater part of Bedford time held but little life. The waters probably entered from the south, and the basin was landlocked on the west, north, and east sides. Neither the formation nor its fauna are known in western Pennsylvania. Rapid deposition seems to have quickly shallowed the basin, and the upper part of the Bedford, particularly the red Bedford, suggests deposition on shallow mud flats during climatic aridity. CARBONIFEROUS PERIOD MISSISSIPPIAN EPOCH Berea sedimentation.-At the end of the Bedford epoch an uplift of the lands on the north and west carried the Cleveland district above sea level and converted it into a low plain but with a surface gradient sufficiently steep and with bordering lands sufficiently high to enable the streams to bring down quantities of sand. The transporting currents channeled away the underlying muds of the Bedford and filled the excavations with sand, the channels being deepest where the land was highest—that is, at the northwest. The sands were spread broadly over the low plain that formed the general delta region. Abundant fragments of land plants were brought down by occasional floods and buried in the sands, and lumps of wet clay were also transported and deposited. Floods also brought down schools of freshwater fishes, some of which became stranded in pools on the delta surface as the flood waters fell, were killed by the drying up of the pools, and were covered by the sands of another flood and preserved as fossils. The numerous specimens of the fossil fish Gonatodus brainerdi found on the surface of a single layer in a single locality at Chagrin Falls are to be accounted for by some such process. While the delta formation was being laid down in the Cleveland district the southeast slope of the land caused the deposits to be made beneath sea level in that direction, and this delta formation thus grades laterally into a finer-grained sandstone that carries marine 2953-307 fossils, as the Berea does in western Pennsylvania and in southern Ohio. During Berea time slow subsidence was in progress, and the sea came nearer and nearer to the Cleveland district, so that in the final stages of the deposition the delta surface was approximately at sea level, and storm waves could occasionally sweep in over this surface and bring a few worn marine shells to be deposited upon and be covered by the sand. In contrast with that of the Bedford the Berea climate seems to have been moist and cool, as suggested by the abundant plant fragments and their carbonized condition and by the clay lumps found in the sands. Orangeville sedimentation.—Continued depression, which lowered the adjacent lands, brought about a cessation of the sand supply and terminated Berea deposition. A renewal of marine conditions in northern Ohio followed. The waters slightly reworked the surface material of the Berea and produced from it a thin sandy stratum that subsequently became cemented by pyrite and forms the peculiar black layer of sand that is everywhere the Orangeville base. There was a break in sedimentation as one set of conditions passed into the other, but only for a short time. Then mud began to be washed into the subsiding basin, but the process was soon interrupted for a brief time by the incursion of sand that forms the thin Aurora sandstone near the base of the formation. The deposition of mud was. quickly resumed and continued with little variation until the full thickness of the formation had been deposited. The conditions. were those of black shale formation, including quiet water and foul bottom from decaying organic matter. Bottom life was scarce, but swimming forms, including large sharks, thrived, especially early in the epoch. Sharpsville and Meadville submergence.-The black shales of the Orangeville are followed by the sandy beds of the Sharpsville. The change in sedimentation indicates oscillation and increased altitude in the bordering lands. The sharpness of the break suggests a pause in sedimentation, though there is no evidence of uplift, and the interval seems to have been very brief. The Sharpsville currents cleared out the foul waters of the Orangeville basin, and a fairly abundant. fauna came in. Fragments of land plants are common, showing that the northern shore of the Sharpsville basin was not far away. The basin gradually deepened, and the sand was followed by the mud of the Meadville shale, with occasional incursions of sand that became more frequent in the later stages of Meadville time. Conditions. were more favorable for an abundant marine fauna than any that had prevailed in the district since Onondaga and Hamilton time, and they became steadily more favorable as Meadville time went on. Yet barren beds alternate with the fossiliferous beds, hence it is evident that conditions varied and the fauna increased or diminished as they changed. Nothing positive can be said concerning the climatic conditions that prevailed in the district during Orangeville and Meadville time. In discussing beds of about the same age in Michigan, Lane 10 states that "the abundance of mica and sand indicates rapid land waste and rock decay, while the abundant bits of vegetation show that there was abundant plant life. Both facts point to a relatively humid climate.' These conclusions seem probable and applicable to the Meadville, whose climate was very likely moist and cool, though less markedly so than that of the Berea. It was tending toward the arid condition that followed. Later Mississippian time.—In the Cleveland district no record remains of any deposits that may have been formed between the end of the Meadville and the beginning of Sharon deposition. The Black Hand and Logan formations of central Ohio lie above the Meadville, and their character indicates increased slopes in bordering lands, so that the streams carried coarser, often much coarser material. As these formations are present 25 miles to the south, it is possible that they were deposited over the Cleveland district and then worn away before the Sharon was laid down. It is also possible that the sea was withdrawn from the district at the end of the Meadville epoch and so remained during Black Hand and Logan time. The former alternative requires more erosion than the latter to produce the surface upon which the Sharon was deposited and allows less time in which to do it. The sea was certainly withdrawn at least as early as the end of the Logan epoch, the entire district becoming land. A later Mississippian submergence, which was most prolonged in the region of the Mississippi Valley, involved southern and central Ohio for a time, and a thin deposit of calcareous mud, now the Maxville limestone, was laid down in a clear, shallow sea, but there is no evidence that this invasion reached as far north in Ohio as the Cleveland district. During this later part of the Mississippian epoch the climate became arid, and there was a salt lake in the Lower Peninsula of Michigan, where gypsum and rock salt were deposited during part of the time. At the end of the Mississippian epoch the sea was withdrawn over a wide area. The Cleveland district had become gently warped along an axis of elevation that coincides with the Chagrin. Valley, and the warped beds were deeply truncated by erosion during this interval. The entire thickness of the Meadville shale was worn away along the axis of the warp, and much of its thickness elsewhere. If the Black Hand and Logan were deposited in the Cleveland district they were completely eroded away at this time. 10 Lane, A. C., Michigan Geol. Survey, vol. 7, pt. 2, p. 23, 1900. PENNSYLVANIAN EPOCH Pottsville time.-Eastern Appalachia increased in altitude as a phase of the uplift that ended the Mississippian sedimentation, and from this elevated land great quantities of gravel and sand were carried down and spread out on the lower grounds on the west, beginning the Pottsville deposition. These early continental deposits of the Pennsylvanian epoch were confined to the Appalachian troughs but slowly spread westward and in the latest part of Pottsville time reached Ohio, and the gravel and sand that now form the Sharon conglomerate were then laid down. The deposit is distinctly of continental, not marine nature. The method of formation of this coarse gravel, whose pebbles must have come from a great distance, has never been satisfactorily explained. It bears a resemblance to some glacial gravel, and Newberry long ago invoked glacial ice as the agency for the transportation of the material. The explanation is possible, but the proof is yet lacking. After the deposition of the gravel and sand swamps covered much of the district, and the vegetal accumulation that now forms the Sharon coal was deposited. This was followed by recurrent deposition of sand, mud carrying many lime-iron concretions, marine limestone, coal, and iron carbonate. These upper formations have since been entirely eroded away from the Cleveland district but are found in the quadrangles next to the south and unquestionably were originally deposited here. Remainder of Pennsylvanian time.-During the remainder of Pennsylvanian time eastern Ohio was flat and close to sea level, most of the time above but occasionally somewhat below it. Deposits of lime mud and of clay mud were laid down in the periods of submergence, in part in marine waters, in part in brackish waters of estuaries. At other times, possibly in periods of emergence, sand deposits were laid down, probably as deltas. There were times also when large parts of the surface were covered with swamps, in which plant débris accumulated. Streams crossing the swamps occasionally washed away the débris from their channels, to be deposited elsewhere, and filled the channels with sand. With the passage of long time these vegetal accumulations have become altered into the coal beds. In eastern Ohio and Kentucky, western Pennsylvania, and West Virginia such beds, each of slight thickness, were deposited before the end of Carboniferous time, making a total thickness of nearly 3,000 feet. The surface of the accumulating mass maintained its closeness to sea level throughout, so that it must have undergone a slow, progressive subsidence, which about kept pace with deposition. Eastern Ohio was in the western part of the basin and received a small thickness of such deposits. The Cleveland district may have been near enough to the western margin to receive only a very little material or even no deposit at all, though its altitude was probably very low. Denudation of the surface since Carboniferous time has removed all trace of beds later than the Sharon conglomerate, and it is very problematical how great a thickness of later beds was ever deposited here. The deposits were sufficiently heavy, however, to crush some of the quartz pebbles in the Sharon. In strong contrast to the climatic aridity of late Mississippian time, the Pennsylvanian climate must have been moist in order to permit the abundant and varied terestrial vegetation. DEFORMATION OF THE STRATA The final stages of the Paleozoic era witnessed a great deformation in eastern North America, which consisted of folding and faulting in the Appalachian region and of uplift and slight folding in the region to the west. This deformation but slightly affected the Cleveland district, except that it carried the area well above sea level, where it has remained ever since. The amount of uplift is unknown but was at least several hundred feet. The warping of the rocks was slightly increased beyond that which they suffered at the end of the Mississippian epoch and earlier. The chief effect was to uplift the region bodily, in diminishing amount from east to west, giving it a general slope to the northwest and west and causing the original streams of the time to flow in the same directions. MESOZOIC ERA By H. P. CUSHING In the Cleveland district all the topographic features produced by the erosion of early Mesozoic time seem to have been obliterated by later wear, and the general course of events must be inferred from that of other parts of the Appalachian province, where such features yet remain. At the beginning of the era the surface of eastern Ohio must have stood at least several hundred feet above sea level and sloped to the west or northwest. The main streams had their sources far to the southeast, near the axis of uplift, and flowed across the district in a general westerly or northwesterly direction. The time was long, and the district seems to have been worn down to a nearly featureless plain that lay not far above sea level, to have been reelevated, and to have been once more worn down. There is no evidence that it passed beneath sea level during this time, and no trace of the earliest Mesozoic plain remains in the district. The second plain, which was formed by erosion during the Cretaceous period, is approximately represented by the summit levels of the remnants of the |