black mud. There is much marcasite (iron sulphide) in the rock, chiefly as concretions. On weathering the iron oxidizes, staining the shale brown and forming sulphates, and the rock breaks down into brown slaty fragments, the surfaces of many of which are mottled with thin crystals of gypsum or pickeringite. Most of the shale has a very pronounced cleavage and on weathering splits readily into thin, even sheets. Some beds are much more massive, and the rock splits irregularly and with difficulty and weathers into concentric shells that break up into flat flakes. These beds are found in the upper part of the formation or alternate with the more slaty beds. The lower division or Olmsted shale member consists chiefly of black shale but contains also beds of blue shale and of thin gray sandstone and here and there a thin calcareous bed with the peculiar structure known as cone in cone. Much of the black shale in the Olmsted member is softer and less black and slaty than the black shale of the upper division, though beds of both types alternate. The blue shale is blue-gray, soft, and fissile and weathers into thin leaves, in this respect differing materially from the soft shale of the Chagrin, which weathers down to masses of sticky clay. The Olmsted member is absent from the Cuyahoga Valley. The sandstones of the Cleveland shale are thin, laminated micaceous light-gray flags, much like those in the Chagrin but usually smoother and less apt to show the rough markings found on the under surfaces of many of the Chagrin flags. They are mostly confined to the lower part of the Olmsted member. In the upper part very thin layers of white papery flags occur in places. The cone-in-cone beds consist of thin light-gray limestone, from 1 to 3 inches thick, are of lenticular form, and pinch out at no great distance. They are common in the western sections of the Olmsted member of the Cleveland but are unknown east of the Rocky River. They are not found in the upper division of the formation so far as known. Fossils. Throughout most of the Cleveland shale fossil remains or traces of any kind are very scarce. But here and there a bed holds them in abundance, and all beds contain a few. The fossils are of few kinds, consisting of remains of fishes, fragments of plants, shells of a few species of brachiopods, chiefly of the inarticulate group, shells of uncertain nature but probably belonging to a crustacean, and tiny conodonts. The more common brachiopods are Orbiculoidea herzeri and Lingula melie, but they are of very erratic distribution. Within the area shown on the map the writer has found them only on Euclid Creek and in the sections in southern Cleveland (Mill Creek, Belt Line cut, Cleveland & Youngstown cut). Here they are found only in the extreme upper layer of the black shale, which is only a few inches thick and which presents features suggesting that it consists of reworked black mud and really belongs with the overlying Bedford certain beds elsewhere present are lacking, or that the Cleveland rests on different horizons of the Chagrin from place to place. The Big Creek and Rocky River sections are in the zone of rapid thickening of the Cleveland by additions at its base; the additions are chiefly black shale but include a few bands of blue fissile shale. The Chagrin beneath becomes much more sandy than at Cleveland and Euclid. There is no question as to the distinctness of the two formations at the contact, which is everywhere sharp. The contact is usually at the top of one of the flagstone bands but drops from one such band to another successively in passing west, and locally the Cleveland rests on soft shale. Where it rests on shale the thin streak of yellow clay is usually present between the two, and the variable marcasite basal layer of the Cleveland is present in many places also, with its characteristic oolitelike marcasite grains. Even where the Cleveland lies on flagstone a film of yellow clay in some places intervenes between this and the black shale, and the marcasite layer also appears here and there. The evidence is fairly convincing that the Cleveland rests on different beds of the Chagrin from place to place or lies on a surface beveled off by erosion before it was deposited. In the sections west of the Rocky River (Dover Bay, Cahoon and Porter Creeks, Eagle Cliff, and Avon Point) it is very difficult to determine the actual base of the Cleveland shale, because the beds added to the base of the Cleveland contain much blue shale and some flagstone, and at the same time blackish shales appear in the Chagrin, so that there is no sharp, lithologic break, as there is farther east. Yet in all these sections (with one possible exception) a break was located at a contact between a band of black shale above and a blue shale or flagstone below, marked by a streak of yellow clay and an intermittent marcasite band, as in the sections above described. The crustacean Spathiocaris cushingi is found in every section in the black shale down to the horizon of this break and is not found below it so far as the writer has been able to discover. The plant fragments in the shales above and below this line represent different forms. This break is 22 feet above the lake level on Cahoon Creek and from 2 to 8 feet above it in the cliff sections around Avon Point. Careful scrutiny is needed to locate it, and it may easily escape recognition. This break is thought by the writer to be the local representative of the widespread break farther south at the base of the Chattanooga shale and to be a more significant break than those at the base of the Bedford shale and of the Berea sandstone described below. BEDFORD SHALE Definition. The Bedford shale was named by J. S. Newberry from the very excellent section of the formation that is exposed in the gorge of Tinkers Creek at Bedford. It there has a thickness of about 85 feet and is composed chiefly of soft blue shale, in which are CLIFF OF CHAGRIN SHALE NEAR EUCLID CREEK, THREE-FOURTHS OF A MILE SOUTH OF EUCLID View looking east. The cliff is about 80 feet high. The thin harder bands here and there and the shallow rainwash gullies show plainly. At the top the base of the black Cleveland shale appears. A. SHALE BANK OF CLEVELAND BRICK & CLAY CO. NEAR CLEVELAND Section in foreground shows 20 feet of black and blue Cleveland whole and BB feet of Chagrin shole View shows about 20 feet of drift and Bedford shale, which must BEDFORD SHALE IN OLD QUARRY ON EUCLID CREEK, 14 MILES NORTH OF SOUTH EUCLID |