Bedford Shale Research Articles

Evidence for Possible Late Paleozoic Alleghenian Deformation Structures in the Devonian Rocks of Erie County, Ohio, USA

Partially exposed bedrock beneath Pleistocene glacial till in Erie County (north-central Ohio) displays unusual structural deformation in the Devonian Berea Sandstone, Bedford Shale, and Ohio Shale. These folded and faulted units are exposed in creeks as anticlines and synclines. Past studies of this area proposed Pleistocene ice movement and soft-sediment deformation during the Late Paleozoic as the deformation mechanisms, but these hypotheses cannot explain the extent of layer displacement or the contradiction between the southwest travel direction of the ice sheet and the structural sense of motion on the folded units. A new interpretation using field data and constructing geologic profiles explains the development of these structures. This study investigated 17 anticlines that trend in different directions. Four of these anticlines are tightly folded with steep or overturned flanks and thrust-faulted Ohio Shale in their cores. Structural analysis of these folds shows that the incompetent shaly units of the Plum Brook–Ohio–Bedford and competent Berea Sandstone were folded above the Delaware–Niagara carbonates as a result of the compressional stress during the Late Paleozoic. Development of these tight or overturned folds, and change in trend of the anticlines, is caused by unusual stratigraphic thickness variations in the Berea and Bedford units. Preserved and undeformed fine sedimentary structures, and sharply faulted beds, in the Berea and Bedford indicate that soft-sediment deformation was not the cause of the regional structural deformation. Finally, the absence of physical features of glacially deformed bedrock demonstrates that Pleistocene glacial ice shove was not the cause of deformed bedrock units in the study area.

THE MANUFACTURE OF AN INSULATING BRICK FROM DIATOMACEOUS EARTH

Development of an Insulating Brick.—Pulverized diatomaceous earth was blended with each of the four clays, Tennessee ball, Bedford shale, Rock Hill, Tionesta, in percentages of 0, 5, 10, 15, 20, 30, 50 clay. Dry pressed briquettes were made using 50 to 60% water, and were burned at cones 06, 02 and 2. Heat conductivity tests were made upon the best bodies of the series.

Palaeoecology and sedimentology of the dysaerobic Bedford fauna (late Devonian), Ohio and Kentucky (USA)

Oxygen-deficient biofacies models rely on lithologic and paleontologic attributes to identify distinctive biofacies interpreted to reflect levels of oxygenation in anaerobic, dysaerobic, and aerobic parts of a stratified water column. This study of the Bedford fauna from the Bedford Shale of Ohio and Kentucky and from adjacent black-shale units reports faunal distributions different from those predicted by the accepted models. This study suggests that, although oxygenation was an important factor that determined the taxonomic makeup of the fauna, bacterially mediated nutrient recycling and substrate characteristics were more important than oxygenation in determining faunal distribution in the dysaerobic zone.

Sedimentology of the Berea Sandstone (Early Mississippian) and the Bedford Shale (Latest Devonian), Williams Field, Michigan: ABSTRACT

Sedimentology of the Berea Sandstone (Early Mississippian) and the Bedford Shale (Latest Devonian), Williams Field, Michigan: ABSTRACT

Shallow Seismic Reflection Confirmation of Berea Gas Pool Structure and Faulting, Portage County, Ohio: ABSTRACT

The Mississippian Berea Sandstone is a reservoir for shallow gas in Suffield Township, Portage County, Ohio, in the informally named St. Joseph's Church field. Production of natural gas from the Berea reservoir is from sandstone up to 60 ft (18 m) thick with porosity in the 15-25% range. The field, which is at about 400 ft (720 ft above sea level), lies updip from the Akron-Suffield fault zone and more or less along strike from the Berea gas field in Randolph Township to the southeast. The trap for the gas is anticlinal and overlying Sunbury shale (so called Coffee shale) is the seal. Initial field pressures were about 80-100 psi (552 kPa). A shallow seismic survey of 6 refraction and 26 CDP reflection lines was made, using a six-channel Bison recording unit. Reflections were obtained from depths down to 800 ft through well-documented formations of known lithology, including glacial till (kame and non-kame), Sharon Shale, Sharone Sandstone, Sunbury Shale, Berea Sandstone, Bedford Shale, and Ohio Shale. Correlation of the seismic data with logs from three separate wells drilled with cable tools was used to derive interval velocities for depth control. Seismic reflections from the top of the Berea Sandstone weremore » consistent over the area with depths from wells. Unexpectedly high elevations of the Berea Sandstone on the southern crest of the anticlinal dome lay in a straight line trending east-west. This suggests the presence of a fault with a general east-west strike and vertical displacement of 15-18 ft. Marginal gas production was encountered just north of the plotted fault on a line between the best producing wells on 450-500 ft centers. Better gas-producing wells lie on the downthrown side of the small eastwest fault and close to the fault. The fault is probably one of many in the area and may be a splinter fault of the Akron-Suffield fault zone.« less

Late Devonian ammonoids from Ohio and adjacent states

Three late Devonian ammonoid-bearing levels are described from the area of Cleveland, Ohio. These appear to represent the German Platyclymenia, Clymenia and Wocklumeria Stufen, clear evidence for which has been lacking previously in eastern North America. The lowest level, around the base of the Cleveland Shale, yieldsSporadoceras, Cyrtoclymenia, Platyclymeniaand a new species,Pleuroclymenia(?)ohioense. The middle level, near the top of the Cleveland Shale, bearsCymaclymenia, SporadocerasandPrionoceras. The highest level, just above the base of the Bedford Shale, hasPrionoceras quadripartitum. This species, and a fauna of the basal Bedford, have been located also in the area of Columbus, Ohio. AnEpiwocklumeria(?) sp. is recorded from Indiana. Attention is drawn to the international importance of the late Famennian and Lower Carboniferous ammonoid sequence which can now be recognized in Ohio.

Defining the nature and location of a Late Devonian–Early Mississippian pycnocline in eastern Kentucky

The pycnocline, the intermediate layer in a tripartite, density-stratified water column, is an important element in recent explanations of the origin of anaerobic sediments. Dysaerobic sediments deposited where the pycnocline intersects the bottom are distinct from overlying aerobic and underlying anaerobic sediments and were used to define the position of the paleopycnocline on a Late Devonian-Early Mississippian sea bottom in eastern Kentucky. Surface and subsurface mapping of the Bedford-Berea sequence and equivalent parts of the New Albany and Chattanooga Shales reveals approximately coeval aerobic, dysaerobic, and anaerobic facies that permitted mapping of the paleopycnocline, apparently the first time the actual sea-bottom position of a paleopycnocline has been defined. The Bedford-Berea (Devonian-Mississippian) sequence is situated between the black Ohio Shale (Devonian) below and the black Sunbury Shale (Mississippian) above. The black shales reflect deposition in a deepening, transgressive sea where anaerobic conditions were easily established and maintained. The intervening Bedford-Berea sequence, however, represents deposition in aerobic and dysaerobic environments during a shallowing, regressive episode as deltas prograded to the south and west in eastern Kentucky. The gray sandstones, siltstones, and shales of the Bedford-Berea sequence have been interpreted as pinching out between the black shales above and below in east-central Kentucky. Each of the above units, however, has a distinctive signature on gamma-ray logs. Comparison of gamma-ray logs and radioactivity profiles with corresponding cores, drillers9 logs, and exposures indicates that black-shale equivalents are present beyond the point where the gray Bedford Shale pinches out; this also is supported by limited biostratigraphic data. This transition from gray Bedford shales to black-shale equivalents marks the approximate position of the ancient pycnocline and has been mapped in the subsurface and on the outcrop in eastern Kentucky. The ancient pycnocline closely parallels the Bedford-Berea delta front, suggesting major control by the delta. The continued influx of oxygen-rich, sediment-laden waters from the delta apparently prevented the northward and eastward migration of the pycnocline up the delta front. The introduced oxygen and sediment, however, were effective only in breaking up the pycnocline over a distance of ∼25 to 40 km from the active delta fronts. Stratigraphic, paleontologic, and geographic constraints indicate that the paleopycnocline was not horizontal but sloped northeastward from shallower waters near the Cincinnati Arch to deeper waters off the delta fronts.

Preliminary account of Late Devonian palynomorph assemblages from the Bedford Shale and Berea Sandstone Formations of central Ohio, U.S.A.

Abstract. Diverse assemblages of well preserved miospores and microplankton have been obtained from a series of samples collected across the boundary between the Bedford Shale and Berea Sandstone Formations in central Ohio. The miospores indicate a Late Devonian (pre-Carboniferous Tournaisian)* age for each of the samples. The microplankton support this age determination. A number of microplankton species not previously recorded from North America are present.

Berea Sandstone Reservoirs in Ashland and Medina Counties, Ohio: ABSTRACT

The Berea Sandstone is one of the better known rock formations in Ohio. It occurs at shallow depths throughout a broad belt in central Ohio and crops out to the north and west of these counties. Stratigraphically, the Berea Sandstone is part of the Waverly Group and is underlain by the red and gray Bedford Shale and overlain by the black Sunbury Shale, all of which are of Early Mississippian age. In Ashland and Medina Counties, the Berea may be divided into two separately identifiable units. The upper unit, called the blanket Berea in outcrop, is approximately equivalent to the cap Berea in the subsurface. The second unit, which lies below the cap Berea varies considerably in its thickness. The thickness of the Berea Sandstone (excluding the cap) ranges from zero to over 125 ft (38 m) in the study area. The thickness changes occur within very short distances (i.e., 100-200 ft or 30-60 m) owing to the original depositional conditions responsible for the formation of the sand body. The traditional, long-standing, and generally accepted view is that the Berea Sandstone was deposited in Ashland and Medina Counties in southward-flowing river channels. More recent drilling in these counties has demonstrated that these sand channels are not continuous, but are isolated sandstone bodies in which petroleum has accumulated. The reservoir capacity of the Berea is between 8 and 22% with an average porosity of 15%. The sandstone consists of loosely cemented, medium to fine-grained quartz with only rare shale breaks below the cap Berea. In Ashland and Medina Counties, Berea wells generally produce oil. Initial production in this area ranges between 1 or 2 bbl and to 40 BOPD after treatment. Reservoirs in the Berea Sandstone generally are productive where the sandstones are thick. They are also productive where the sandstone is thinner, but high on structure. Although a high structural position is preferred, the critical consideration is the thickness of the sandstone body and the reservoir geometry. End_of_Article - Last_Page 1920------------

Stratigraphy and Resource Assessment of Mississippian and Devonian Oil Shales of Northeastern Kentucky: ABSTRACT

Heightened interest in the organic carbon-rich shale of Mississippian and Devonian age as a source of oil has resulted in intensive leasing along the shale outcrop belt in Kentucky. Twelve cores of shale from Lewis and Fleming Counties were examined and analyzed in an effort to relate details of stratigraphy to the oil-rich horizons and to outline areas of minable potential resources. Formations of interest are the Sunbury Shale (Lower Mississippian) and the Ohio Shale (Upper Devonian). The generalized stratigraphy (Lower Mississippian through Upper Devonian) is, in descending order: Borden Formation, Sunbury Shale, Berea Sandstone, Bedford Shale, and Ohio Shale. Useful key markers in the sequence are the Three Lick Bed and the Foerstia zone, which are both in the Ohio Shale. The Three Lick Bed divides the Ohio Shale into the Cleveland Member, above, and the Huron Member, below. The Ohio Shale is underlain by Silurian Bisher Limestone and Crab Orchard Formation. Organic content is high in the Sunbury Shale and in the upper part of the Cleveland Member of the Ohio Shale. In cores, the total thickness of the Sunbury ranges from 12.0 to 18.4 ft (3.7 to 5.6 m). The combined thickness of Berea Sandstone and Bedford Shale ranges from 28 to 122 ft (8.5 to 37.2 m). The Cleveland shale ranges from 50 to 65 ft (15.2 to 19.8 m). Assuming a stripping ratio of 2.5 to 1, more than 2.9 × 106 acre-ft (3.6 × 103 cu hm) of shale having a Fischer-assay oil yield greater than 11 gal/ST (38 l/MT) is minable by means of existing methods. A conservative estimate of the amount of the potential strippable shale-oil resource in these two counties is more than 2 × 109 bbl. End_of_Article - Last_Page 897------------

Mineralogic and Chemical Composition of Antrim Shale, Michigan: ABSTRACT

The Antrim Shale is the Michigan basin equivalent of Devonian-Mississippian black shales of the eastern United States. The Dow Chemical Co., with DOE funding, has investigated the possibility of in-situ gas production from the Antrim by underground combustion. This paper summarizes some results obtained in the shale characterization program that was a part of that study. Antrim Shale is rather uniform in composition and contains about 30% Si, 8% Al, 4% Fe, 2% Mg, 3% Ca, 2% S, and 5% organic carbon. Mineralogically, Antrim Shale consists of 50 to 60% quartz, 20 to 35% illite, 5 to 10% kaolinite, 0 to 5% chlorite, and up to 5% pyrite. Calcite and dolomite, when present, occur as limestone nodules, lenses, and interbeds up to 5 ft (2 m) thick in the lower half of the Antrim. Bedford Shale, which overlies the Antrim in eastern Michigan, contains more total clays, illite and kaolinite, and less quartz. Ellsworth Shale, which interfingers with the upper part of the Antrim in western Michigan, contains up to 25% dolomite. Antrim Shale contains up to 12.8% organic material, as measured by low-temperature ashing. Bitumen contents range from 0.2 to 0.8%. Average molecular weights of bitumen components are 360 to 370. Deeper drill holes have higher bitumen contents. Kerogen, which makes up the rest of organic material, is of low functionality, about 1 functional group per 25 carbon atoms. Hydroxyl (1 group/50 C atoms) and alkene double bonds (1 group/50 C atoms) are the most common groups present. End_of_Article - Last_Page 983------------

Fluctuations in a late devonian-early Mississippian phytoplankton flora of Ohio, U.S.A

Fossil diversity and abundance fluctuations of Late Devonian (Famennian)—Early Mississippian (Tournaisian) phytoplankton assemblages were determined in a stratigraphic sequence of samples in Barberton test core 3, from northeast Ohio. Both diversity and abundance were relatively high during deposition of the lower Chagrin Shale (Upper Devonian) and both decreased during deposition of the upper Chagrin Shale. The overlying Cleveland Shale (Upper Devonian) is characterized by sharply increased abundance with a corresponding (although less marked) increase in diversity; in contrast, both abundance and diversity were at relatively low levels during deposition of the Lower Mississippian Bedford Shale, the uppermost unit of the sequence. These trends agree with the phytoplankton periodicity model presented by Tappan, which indicates large-scale extinction at the end of the Devonian. Many of the acritarch and prasinophycean algal taxa have restricted stratigraphic occurrences within the section studied, making them useful for local and perhaps worldwide correlation. The stratigraphically restricted taxa provide a basis for the proposal of five biostratigraphic zones within the Upper Famennian (Upper Devonian) and a portion of the Lower Mississippian. In ascending order occur: the Gorgonisphaeridium ohioense Assemblage Zone, the Acriora petala Assemblage Zone, the Muraticavea enteichia Range Zone, the Cymatiosphaera labyrinthica Range Zone, and the Navifusa drosera Assemblage Zone.

Phytoplankton Abundance and Diversity During the Late Devonian and Early Mississippian of Ohio: ABSTRACT

The Upper Devonian Chagrin and Cleveland Shales contain a diverse and abundant organic-walled microplankton assemblage of acritarchs and leiospheres with associated spores, whereas the Lower Mississippian Bedford Shale phytoplankton assemblage is greatly reduced. Ten-gram samples were examined at intervals of 10 ft or less for the entire 573 cores through the 3 formations, to determine microplankton abundance and diversity. In these samples, spores are the most abundant element, followed by leiospheres and then acritarchs. More than 50 species of acritarchs and leiospheres, mostly new, have been identified in 62 samples of the Upper Devonian section, whereas one Gorgonosphaeridium species occurs abundantly in all Upper Devonian samples and is present in most Lower Mississippian samples. General acritarch diversity decreases slightly up-section in the Chagrin Shale, and increases slightly in the basal Cleveland Shale; the decrease is more marked in the upper Cleveland Shale, and is most notable in the Bedford Shale. Acritarch abundance also lessens up-section through the Upper Devonian formations, with minima in the upper fourth of the Chagrin Shale and the upper half of the Cleveland Shale. Acritarchs are very scarce in the Bedford Shale. As total phytoplankton abundance shows a marked decrease up-section, from the middle of the Chagrin Shale to the top of the Bedford Shale, a drop in net primary productivity is indicated for the Late Devonian and Early Mississippian of Ohio. End_of_Article - Last_Page 812------------

Geology of the Bedford Shale and Berea Sandstone in the Appalachian Basin

Geology of the Bedford Shale and Berea Sandstone in the Appalachian Basin

Geology of the Bedford Shale and Berea Sandstone in the Appalachian Basin

Geology of the Bedford Shale and Berea Sandstone in the Appalachian Basin

STRATIGRAPHY OF THE BEREA SANDSTONE AND ASSOCIATED ROCKS IN NORTHEASTERN OHIO AND NORTHWESTERN PENNSYLVANIA

Research Article| November 01, 1951 STRATIGRAPHY OF THE BEREA SANDSTONE AND ASSOCIATED ROCKS IN NORTHEASTERN OHIO AND NORTHWESTERN PENNSYLVANIA WALLACE DE WITT, JR. WALLACE DE WITT, JR. BOX 272, NEW PHILADELPHIA, OHIO. Search for other works by this author on: GSW Google Scholar GSA Bulletin (1951) 62 (11): 1347–1370. https://doi.org/10.1130/0016-7606(1951)62[1347:SOTBSA]2.0.CO;2 Article history received: 21 Jun 1951 first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation WALLACE DE WITT; STRATIGRAPHY OF THE BEREA SANDSTONE AND ASSOCIATED ROCKS IN NORTHEASTERN OHIO AND NORTHWESTERN PENNSYLVANIA. GSA Bulletin 1951;; 62 (11): 1347–1370. doi: https://doi.org/10.1130/0016-7606(1951)62[1347:SOTBSA]2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract This paper summarizes stratigraphic information obtained in a field study of Upper Devonian and lower Mississippian rocks of northeastern Ohio and northwestern Pennsylvania. The upper part of the Chagrin shale has been traced from northeastern Ohio into the Riceville shale in northwestern Pennsylvania. The Cleveland member of the Ohio shale has been traced from its type locality near Cleveland eastward into the Grand River valley in western Ashtabula County, Ohio, where the black shale of the Cleveland appears to grade laterally into the upper part of the gray Chagrin shale. The Bedford shale and the Berea sandstone have been traced eastward from northern Ohio to the vicinity of Meadville in central Crawford County, Pennsylvania. The Bedford shale is underlain by the Cleveland member of the Ohio shale west of the Grand River valley and by the Cussewago sandstone in extreme northeastern Ohio and in northwestern Pennsylvania east of Meadville. The Cussewago sandstone, which forms a good key bed, is not a part of the Berea sandstone as has been suggested previously by some geologists. The Cussewago sandstone was derived from a different source and deposited from a different direction than either the Berea sandstone or the Corry sandstone. In northwestern Pennsylvania, the Bedford shale was found to be the same as White's Cussewago shale and Chadwick's Hayfield shale. In the vicinity of Meadville, Pennsylvania, the Bedford shale and the Berea sandstone grade laterally into a thin unit of siltstones and intercalated shale, here named the Shellhammer Hollow formation. Farther east, near Riceville, Pennsylvania, the Shellhammer Hollow formation grades laterally eastward into the Corry sandstone. The Corry sandstone, therefore, can not be considered an eastern siltstone facies of the Berea sandstone as has been suggested previously, although it is a near temporal equivalent of the Berea sandstone. A very coarse-grained deltaic sandstone occurs above the stratigraphic horizon of the Corry sandstone in part of southeastern Erie County, Pennsylvania. This local sandstone is here named the Hungry Run sandstone member of the Orangeville shale. A thin silt-stone, characterized by many short curved markings, is an excellent stratigraphic marker in the basal part of the Orangeville shale, above the Berea sandstone, the Shellhammer Hollow formation, and the Corry sandstone. This siltstone, here named the Bartholomew siltstone member, has been traced widely over southern Erie County, Crawford County, and northwestern Venango County, Pennsylvania. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

BLACK HAND SANDSTONE AND CONGLOMERATE IN OHIO

The lower and middle Mississippian strata of Ohio, known as the Waverly series, consist of five formations, from older to younger: the Bedford shale, the Berea sandstone, the Sunbury shale, the Cuyahoga formation, and the Logan formation. They were laid down in the great shallow basin known as the Appalachian geosyncline. The floor of the basin rose and sank from time to time so that shore conditions with mud, sand, and conglomerate might prevail at any place, to be succeeded by deeper water and limestone formation. Sometimes it was dry, and again deltas spread across it. This resulted in a succession of deposits, varying in character as the condition surrounding their deposition changed. The Black Hand sandstone and conglomerate member of the Cuyahoga formation of Ohio has been one of the perplexing problems of the Waverly series. This conglomeratic sandstone, correlated with the Big Injun sandstone of southeastern Ohio, forms the scenic cliffs and deep gorges of Old Man9s Cave, the Rock House, Ash Cave, Cantwell Cliff, Conkle9s Hollow, and Cedar Falls, in the Hocking County region. The conglomerate facies of this sandstone occurs in elongate masses, from Vinton County at the south into Richland and Ashland counties to the north, a distance of more than 100 miles. The individual conglomerate lobes trend slightly west of north. The character of the sediments, which are marine, and the dip of the bedding planes suggest deposition in shallow water in rather strong currents with scouring action. All the evidence indicates that the currents came from the south; the true bedding planes dip 3°–15° and range in direction from N. to NE. to E. to NW. The pebbles of the conglomerate, which are quartz, are a quarter of an inch to more than 2 inches long. They are well rounded, indicating that they have been reworked several times. The source of this quartz is believed to be to the north and northeast. When traced horizontally from the conglomeratic masses, the Black Hand member thins and contains more shale, and the sandstones are finer and do not exhibit the strong cross-bedding and evidence of scouring action. The change in facies is accounted for by the explanation that the area, during the deposition of the Black Hand member, was a shallow interior sea in which bars, spits, beaches, and deltas were developed. What appears to be a bar was built on the west side of the area. Quiet lagoons were present in which finer sands and muds accumulated. The thickness of the Black Hand (Big Injun) conglomerate suggests that the area was sinking during the accumulation of the Black Hand conglomerates. The variation in thickness of the Black Hand and the irregular contour of its top suggest a dis-conformity with the Berne conglomerate member above, at the base of the Logan.

Flow Structures in the Berea Sandstone and Bedford Shale of Central Ohio

The structures in the Berea sandstone and the Bedford shale described in the past as concretionary or layers are shown to result from contemporaneous mass movements on the free surface of deposition. The top of the disturbed rock was generally truncated by erosion before the overlying undisturbed beds were laid down. Lateral movements are evident in many instances and at many levels in the formations. These movements and others in which lateral movement is not readily apparent are interpreted as surface flows and slides. The causes of subaqueous flows are reviewed in an attempt to find the reason for the flows. The conclusion is reached that they may have started spontaneously in the soft sediment as it accumulated under the conditions which obtained. Important causes of such flows include an increasing weight of sediment, a slight surface slope, and occasional beds or seams of clay which flowed readily and also acted as a lubricant between sand layers, permitting them to slide past one another.

Chagrin Formation of Ohio

Introduction In northeastern Ohio the Ohio black shale of early reports was divided by Dr. Newberry into the Huron, Erie, and Cleveland shales, 2 of which the Erie was later renamed the Chagrin by Professor Prosser, 3 the entire succession up to the Berea thus becoming : Berea grit Bedford shale Cleveland black shale Chagrin formation Huron black shale in which the type Huron may be largely contemporaneous with the Chagrin 4 and only partly identical with the “Huron” beneath the Chagrin, in the well logs. More recently these strata of northeastern Ohio have been most carefully described by Prosser, 5 whose work furnishes the foundation for the present writing. In northwestern Pennsylvania Dr. I. C. White described the following succession in Erie and Crawford counties, adjacent to Ohio and western New York : 6 Corry sandstone Cussewago shale Cussewago sandstone Riceville shale Venango group Chemung beds Girard shale Portage beds Oil Lake group The relations . . .

Diastrophic importance of the unconformity at the base of the Berea grit in Ohio

Introduction In 1874 J. S. Newberry made the following statements in the Ohio reports: “In most localities where the Bedford shale is exposed the upper surface is very irregular, and it; is evident that the formation has been extensively eroded by the agency which transported the beds of sand, now consolidated into, the Berea grit.” 2 “The best exposures of the entire thickness of the Bedford shale are on the Black River below Elyria. . . . It will also be noticed here that the upper surface of the shale is very irregular, showing that the currents of water which transported the sand—now the Berea sandstone—cut away the shale, then a red clay, in broad and deep channels. As these were filled with sand, the under surface of the sandstone is very uneven and its thickness variable.” 3 This unconformity, noted so long ago by Newberry, is wide-spread, . . .