Wenlockian

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Carlton E. Breit - One of the best experts on this subject based on the ideXlab platform.

  • placement of the Wenlockian ludlovian boundary in western new york state
    Lethaia, 1991
    Co-Authors: Steven T. Loduca, Carlton E. Breit
    Abstract:

    Despite many years of detailed examination focused on the Silurian strata of New York State, the position of the Wenlockian/Ludlovian boundary has, to date, not been satisfactorily cstablished. Reccnt discovery of early Ludlovian graptoloid graptolites, however, provides the first conclusive biostratigraphic evidence for placement of this chronostratigraphic boundary within the New York sections. The carly Ludlovian genera Saetograptus and Spinograptus were recovered from a thin, but laterally persistent bed of argillaceous dolostone located near the base of the Goat Island Formation. This occurrencc indicates that the Wenlockian/Ludlovian boundary is at or near the contact between the Goat Island Formation and the underlying Gasport Formation, considerably lower than had previously been suspected. □Silurian, Wenlockian, Ludlovian, graptolites, stratigraphy. biostratigraphy.

  • Placement of the Wenlockian/Ludlovian boundary in western New York State
    Lethaia, 1991
    Co-Authors: Steven T. Loduca, Carlton E. Breit
    Abstract:

    Despite many years of detailed examination focused on the Silurian strata of New York State, the position of the Wenlockian/Ludlovian boundary has, to date, not been satisfactorily cstablished. Reccnt discovery of early Ludlovian graptoloid graptolites, however, provides the first conclusive biostratigraphic evidence for placement of this chronostratigraphic boundary within the New York sections. The carly Ludlovian genera Saetograptus and Spinograptus were recovered from a thin, but laterally persistent bed of argillaceous dolostone located near the base of the Goat Island Formation. This occurrencc indicates that the Wenlockian/Ludlovian boundary is at or near the contact between the Goat Island Formation and the underlying Gasport Formation, considerably lower than had previously been suspected. □Silurian, Wenlockian, Ludlovian, graptolites, stratigraphy. biostratigraphy.

Steven T. Loduca - One of the best experts on this subject based on the ideXlab platform.

  • placement of the Wenlockian ludlovian boundary in western new york state
    Lethaia, 1991
    Co-Authors: Steven T. Loduca, Carlton E. Breit
    Abstract:

    Despite many years of detailed examination focused on the Silurian strata of New York State, the position of the Wenlockian/Ludlovian boundary has, to date, not been satisfactorily cstablished. Reccnt discovery of early Ludlovian graptoloid graptolites, however, provides the first conclusive biostratigraphic evidence for placement of this chronostratigraphic boundary within the New York sections. The carly Ludlovian genera Saetograptus and Spinograptus were recovered from a thin, but laterally persistent bed of argillaceous dolostone located near the base of the Goat Island Formation. This occurrencc indicates that the Wenlockian/Ludlovian boundary is at or near the contact between the Goat Island Formation and the underlying Gasport Formation, considerably lower than had previously been suspected. □Silurian, Wenlockian, Ludlovian, graptolites, stratigraphy. biostratigraphy.

  • Placement of the Wenlockian/Ludlovian boundary in western New York State
    Lethaia, 1991
    Co-Authors: Steven T. Loduca, Carlton E. Breit
    Abstract:

    Despite many years of detailed examination focused on the Silurian strata of New York State, the position of the Wenlockian/Ludlovian boundary has, to date, not been satisfactorily cstablished. Reccnt discovery of early Ludlovian graptoloid graptolites, however, provides the first conclusive biostratigraphic evidence for placement of this chronostratigraphic boundary within the New York sections. The carly Ludlovian genera Saetograptus and Spinograptus were recovered from a thin, but laterally persistent bed of argillaceous dolostone located near the base of the Goat Island Formation. This occurrencc indicates that the Wenlockian/Ludlovian boundary is at or near the contact between the Goat Island Formation and the underlying Gasport Formation, considerably lower than had previously been suspected. □Silurian, Wenlockian, Ludlovian, graptolites, stratigraphy. biostratigraphy.

Mark A. Kleffner - One of the best experts on this subject based on the ideXlab platform.

  • Conodont biostratigraphy and depositional history of strata comprising the Niagaran sequence (Silurian) in the northern part of the Cincinnati Arch region, west-central Ohio, and evolution of Kockelella walliseri (Helfrich)
    Journal of Paleontology, 1994
    Co-Authors: Mark A. Kleffner
    Abstract:

    The Dayton, Osgood, and Laurel Formations and the Euphemia, Springfield, and basal part of the Cedarville Dolomites near the axis of the Cincinnati Arch in northeast Preble County, Ohio, belong in the uppermost part of the Ozarkodina sagitta rhenana to lower part of the Ozarkodina? crassa Chronozone and are late early to middle Wenlockian in age. The Dayton–Cedarville succession on the eastern flank of the Cincinnati Arch in north-central Greene County, Ohio, belongs in the uppermost part of the Pterospathodus celloni to upper part of the Ancoradella ploeckensis Chronozone and is late Llandoverian to early middle Ludlovian in age.The sea transgressed across the exposed and eroded Brassfield Formation to begin deposition of the Dayton Formation on the eastern flank of the Cincinnati Arch in Greene County, Ohio, during the late Llandoverian and completely flooded all of west-central Ohio by the late early Wenlockian. The region remained covered by a sea of fluctuating depth during deposition of the Dayton Formation–Cedarville Dolomite succession from the Wenlockian through early middle Ludlovian.Kockelella walliseri (Helfrich) evolved from K. ranuliformis (Walliser) during the middle Wenlockian (upper part of Ozarkodina sagitta rhenana Chronozone) by development of a lateral process adjacent to the cusp on the Pa element and by minor modification of the Pb element and some of the ramiform elements. Specimens from upper Llandoverian and lower Wenlockian strata previously assigned to K. walliseri belong to a different species, Kockelella sp. A Fordham, 1991. The evolutionary trends in the K. walliseri lineage, progressive restriction of the basal cavity and increasing development of the length of the lateral processes in the Pa element, parallel the trends in the K. amsdeni–K. stauros–K. variabilis lineage and resulted in the divergence of Kockelella cf. K. stauros Bischoff, 1986, from the main lineage in the middle Wenlockian.

  • Conodont biostratigraphy of the upper part of the Clinton Group and the Lockport Group (Silurian) in the Niagara Gorge region, New York and Ontario
    Journal of Paleontology, 1991
    Co-Authors: Mark A. Kleffner
    Abstract:

    Twenty-nine conodont species are represented in formations comprising the upper part of the Clinton Group and the Lockport Group at four localities in Niagara County, New York, and adjacent Ontario, Canada. Four previously unrecognized species of Ozarkodina represented in two samples from the Oak Orchard Formation are described. Ozarkodina sagitta rhenana (Walliser) and O. sagitta sagitta (Walliser) appear to form an evolutionary lineage in which the latter evolved from the former during the late early Wenlockian by slight modification of the Pa element. Elements in the other corresponding positions in their respective apparatuses are virtually identical. The Williamson Shale, Irondequoit Limestone, Rochester Shale, and DeCew Formation of the Clinton Group belong in the upper part of the Pterospathodus amorphognathoides to the middle part of the Ozarkodina sagitta sagitta Chronozone, and are early to early middle Wenlockian in age. The Gasport, Goat Island, Eramosa, and Oak Orchard Formations of the Lockport Group belong in the middle part of the O. sagitta sagitta to the lower part of the Ancoradella ploeckensis Chronozone, and are early middle to late Wenlockian in age.

Darryl N. Hayashida - One of the best experts on this subject based on the ideXlab platform.

  • A paleoclimate simulation of the Wenlockian (Late Early Silurian) world using a general circulation model with implications for early land plant paleoecology
    Palaeogeography Palaeoclimatology Palaeoecology, 1994
    Co-Authors: George T. Moore, Stephen R. Jacobson, Charles A. Ross, Darryl N. Hayashida
    Abstract:

    Abstract The Silurian Period (439–409 Ma) is known for its extensive organic-rich, graptolitic, black shales and graptolitic, shelf carbonates. Physical conditions drive paleoclimate and control the zonal deposition of lithotopes. Moreover, the paleoclimate created a paleoceanic environment favorable for widespread generation, deposition, and preservation of plankton. The relationship between the paleogeographic framework, including paleotopography, and the resultant bio- and lithostratigraphy are suitable for study with a general circulation model (GCM). For this study we chose the Wenlockian Stage (430–424 Ma), the late Early Silurian. The Wenlockian northern hemispheric surface was dominated by a large ocean, the southern hemisphere by the giant Gondwanan continent. Much of Gondwana's extensive margin was in the mid-latitudes. Laurentia and Baltica occupied a tropical position, and Siberia and Kazakh laid in warm temperate latitudes to the north. Silurian stratigraphy fits a paleoatmosphere with elevated greenhouse conditions. Estimated Silurian atmospheric CO 2 values vary between wide limits. We used 1120 ppm CO 2 4x that of the pre-industrial level and at the lower end of the range of estimates. The paleoclimate was forced by the paleogeography of each hemisphere's circulation. The northern hemisphere Silurian simulation is dominated by strong zonal circulation in all seasons. In contrast, the continental southern hemisphere reacts to the summer heating and winter cooling of Gondwana. This simulation furnishes paleoclimatic conditions that help explain the distribution of early land plants. This paleoclimate simulation supports a humid coastal paleoenvironment for early Silurian land plants. Furthermore, these results imply that relative humidity was more important than precipitation rates, and that intercontinental spore dispersal between Laurentia/Europe and Gondwana was not wind-aided. The GCM provides a good match with Silurian lithological and paleobiological data.

Breit, Carlton E - One of the best experts on this subject based on the ideXlab platform.

  • Placement of the Wenlockian/Ludlovian boundary in western New York State
    'Wiley', 1991
    Co-Authors: Loduca, Steven T, Breit, Carlton E
    Abstract:

    Despite many years of detailed examination focused on the Silurian strata of New York State, the position of the Wenlockian/Ludlovian boundary has, to date, not been satisfactorily established. Recent discovery of early Ludlovian graptoloid graptolites, however, provides the first conclusive biostratigraphic evidence for placement of this chronostratigraphic boundary within the New York sections. The early Ludlovian genera Saetograptus and Spinograptus were recovered from a thin, but laterally persistent bed of argillaceous dolostone located near the base of the Goat Island Formation. This occurrence indicates that the Wenlockian/Ludlovian boundary is at or near the contract between the Goat Island Formation and the underlying Gasport Formation, considerably lower than had previously been suspected