Chitinozoans from the Ordovician-Silurian Boundary Beds in the Eastern Cincinnati Region in Ohio and Kentucky

Author Institution: Geological Survey of Sweden ; Department of Geology and Mineralogy, The Ohio State UniversityRepresentatives of seven species of chitinozoans, one of which is new (Ancyrochitina belfastensis n. sp.), were isolated from samples of the lowermost Silurian Belfast Member and of slightly younger beds of the Brassfield Formation and of the Upper Ordovician Preachersville Member of the Drakes Formation at two localities in southern Ohio and north-central Kentucky in an attempt to determine the size of the stratigraphic gap at the Ordovician-Silurian paraconformity. Based on comparisons with successions in Estonia and on Anticosti Island, Quebec, the chitinozoans suggest that the stratigraphic gap between the systems, which is likely to be due to a global sea level drop associated with the Gondwana glaciation, represents an interval from the Ashgillian D. complanatus Zone to the early Llandoverian C. cyphus Zone and hence corresponds to about four graptolite zones. The present study is the first record of Silurian chitinozoans from Ohio

Lower and Middle Paleozoic Geology of Southern Ohio

On cover: "Field Excursion 10. Guidebook, Sixth Gondwana Symposium 19-23 August, 1985."This guidebook was produced for a field trip for the participants of the Sixth Gondwana Symposium held at the Ohio State University on August 19-23, 1985. The purpose of the field trip is to provide an overview of Upper Ordovician through Lower Mississippian geology of southern Ohio and northernmost Kentucky on the eastern flank of the Cincinnati Arch. Included in the field trip is archeologically and geologically interesting Serpent Mount "cryptoexplosion" structure. The guide gives basic information about the geology at each stop

Middle and Upper Ordovician conodont and graptolite biostratigraphy of the Marathon, Texas graptolite zone reference standard

Volume: 21Start Page: 723End Page: 75

The base of the global Dapingian Stage (Ordovician) in Baltoscandia: conodonts, graptolites and unconformities

In the recently completed and formally ratified new series and stage classification of the Ordovician System, the base of the Middle Ordovician Series coincides with the base of the global Dapingian Stage. In the Global Stratotype Section and Point (GSSP) of this stage, which is located at Huanghuachang in southern China, the base of the Dapingian Stage is defined its the level of first appearance of the conodont Baltoniodus triangularis. The fact that this species, along with some other taxa present at the Dapingian GSSP, Occurs in many sections in Baltoscandia makes it possible to recognise with considerable precision the level of this global stage boundary in Sweden, Estonia, northwestern Russia, and Denmark. In several, but not all, regions, especially in the East Baltic, the global stage boundary coincides with the base of the regional Volkhov Stage and Call be tied to the base of the Megistaspis polyphemus Trilobite Zone. The regionally somewhat different relationships between the position of the global stage boundary and a very widespread hardground complex are probably due to the occurrence of local and/or regional unconformities in the upper Floian-lower Dapingian interval. Although biostratigraphically important graptolites are present in the study interval in some Baltoscandic sections, the precise graptolite correlation of the base of the Dapingian Stage remains somewhat unclear, although it appears to be near, or at, the base of the Isograptus victoriae victoriae Zone (Ca 2)

Chemostratigraphy in the Swedish Upper Ordovician: Regional significance of the Hirnantian delta C-13 excursion (HICE) in the Boda Limestone of the Siljan region

Samples from the Boda Limestone and immediately overlying strata at Osmundsberget in de Siljan region have produced an excellent Hirnantian isotope excursion (HICE) curve, in which the excursion interval is about 22 m thick and the HICE reaches maximum delta C-13 values of between +5 parts per thousand and +6 parts per thousand. Both the HA and HB stratigraphic unconformities are recognized in the study succession as well as in the coeval stratigraphic interval in the Loka Formation in Vastergotland and at Meifod in central Wales. A comparison between these and some other shallow-water successions in North America and northern Europe shows striking similarities in the delta C-13 curve, the lithology, and the stratigraphic sequence development. This is taken as support for the idea that glacio-eustacy exercised a major control on the depositional pattern in shallow-water successions during Hirnantian time. This applies also to the Osmundsberget succession where the formation of carbonate mounds was stopped by the HA regression that was caused by a major glaciation in Gondwana

The lowermost Silurian of Jamtland, central Sweden: conodont biostratigraphy, correlation and biofacies

The Late Ordovician-Early Silurian succession in Jamtland includes the marine Kogsta Siltstone, which is unconformably overlain by the shallow-water Ede Quartzite that grades into the open-marine Berge Limestone. A Hirnantia shelly fauna dates the uppermost Kogsta Siltstone as Hirnantian, and shelly fossils indicate an Aeronian age for the Berge Limestone. Biostratigraphically highly diagnostic conodonts of the early-middle Aeronian Pranognathus tenuis Zone provide the first firm date of the Upper Ede Quartzite and the lowermost Berge Limestone. The Lower Ede Quartzite has not yielded fossils, but sedimentological data suggest it to be of Hirnantian age and reflect the glacio-eustatic low-stand. The contact between the Lower and Upper Ede Quartzite, here taken to be the Ordovician-Silurian boundary, appears to be an unconformity associated with a stratigraphic gap that at least includes the Rhuddanian Stage. The biostratigraphically important conodonts Pranognathus tenuis, Kockelella? manitoulinensis, and Pranognathus siluricus are recorded from Sweden for the first time, and these and other conodonts are used for correlations with coeval units in Europe and North America. In a regional review of Aeronian conodont faunas, three intergrading, apparently depth-related, conodont biofacies are recognised, the Jamtland conodonts representing the one characteristic of the shallowest water

Late Ordovician graptolites from the North American Midcontinent

Volume: 40Start Page: 965End Page: 101

Late Ordovician-Early Silurian delta C-13 chemostratigraphy in the Upper Mississippi Valley: implications for chronostratigraphy and depositional interpretations

A pioneer study of the previously unknown delta C-13 chemostratigraphy in the Ordovician/Silurian boundary interval in eastern Iowa and northeastern Illinois resulted in the discovery of the Hirnantian Isotope Carbon Excursion (HICE). The presence of this major isotope excursion in the Mosalem Formation in Iowa and the Wilhelmi Formation in Illinois, which indicates that the excursion interval in these units is of Hirnantian (latest Ordovician) rather than Early Silurian age, necessitates a revised chronostratigraphic classification of these units. Although the precise level of the Ordovician/Silurian boundary remains somewhat uncertain in the absence of the diagnostic graptolites, it is herein placed in the upper part, but well below the top, of the Mosalem Formation and at the top of the Wilhelmi Formation. During a major regression following the deposition of the Maquoketa Shale, the upper part of the latter elastic unit was in some places deeply eroded, resulting in a topographically dissected landscape with upland areas separated by wide incised valleys. During a subsequent late Hirnantian transgression, these palaeovalleys were gradually filled with marine sediments, but the upland areas were not transgressed until earliest Silurian times. The new chemostratigraphical evidence is in good agreement with the available biostratigraphical data, especially from corals, conodonts, and brachiopods. A preliminary chemostratigraphical study of the presumably coeval Edgewood Group successions in Pike County, northeastern Missouri failed to document any heavy delta C-13 values characteristic of the HICE and some, or all, of the Hirnantian values obtained there may be diagenetically overprinted

Katian (Upper Ordovician) delta C-13 chemostratigraphy and sequence stratigraphy in the United States and Baltoscandia: A regional comparison

delta C-13 values of numerous limestone samples from Katian (Upper Ordovician) successions in Oklahoma and the Upper Mississippi Valley document the presence of at least three of the four positive excursions that have been recognized in the lower-middle Katian interval in the Cincinnati region in Ohio. Kentucky, and Indiana. A comparison with Estonia reveals that five out of the six positive excursions now recorded through the Katian succession in the Cincinnati region are present in the coeval stratigraphic intervals in Estonia, which suggests that these represent global perturbations in the carbon cycle A study of the relations between flooding events and delta C-13 excursions shows that only some of the excursions occur in transgressive intervals whereas other excursions are in regressive strata and hence, this is in conflict with the idea that positive carbon isotope excursions are forced by rises in sea level Part of a previously published attempt to use Upper Ordovician sequence stratigraphy for trans-Atlantic correlation is shown to be seriously out of phase with the biostratigraphy and chemostratigraphy Several of the sequences recognized in the Cincinnati region do not appear to have counterparts in Estonia, which suggests that they do not reflect eustatic, but local, conditions (C) 2010 Elsevier B V All rights reserved

The middle Darriwilian (Ordovician) delta C-13 excursion (MDICE) discovered in the Yangtze Platform succession in China: implications of its first recorded occurrences outside Baltoscandia

The middle Darriwilian delta C-13 excursion (MDICE), one of the least known of the Ordovician delta C-13 excursions, has previously been recorded only from the Middle Ordovician of Baltoscandia. Analysis of many recently collected limestone samples from the Guniutan Formation at two Yangtze Platform localities show elevated delta C-13 values in the same biostratigraphic interval (Microzarkodina ozarkodella Conodont Subzone) as the MDICE in Baltoscandia, which justifies identification of the Chinese delta C-13 excursion as the MDICE. These occurrences, which are in strata that show striking lithological and conodont faunal similarity to the Swedish Holen Limestone and some coeval units in Estonia, indicate that the MDICE, the stratigraphically oldest of the named Ordovician delta C-13 excursions, is likely to have a world-wide distribution and to have great potential for local and long-range chemostratigraphic correlations