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Book Chapter

Tectonic and Eustatic Influences Upon the Sedimentary Environments of the Upper Ordovician Strata of New York and Ontario

By
David Lehmann
David Lehmann
Department of Earth and Environmental Sciences, University of Rochester, Rochester, New York 14627
1
Present address: Huntingdon Engineering and Environmental, 535 Summit Point Drive, Henrietta, New York 14467
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Carlton E. Brett
Carlton E. Brett
Department of Earth and Environmental Sciences, University of Rochester, Rochester, New York 14627
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Ronald Cole
Ronald Cole
Department of Earth and Environmental Sciences, University of Rochester, Rochester, New York 14627
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Published:
January 01, 1994

Abstract

The Upper Ordovician stratigraphic succession in New York and Ontario is superficially similar to a very large eustatically-controlled sequence. These strata are bounded by unconformities, and analogs of systems tracts are present. Submarine fan siltstones, sandstones, and shales comprise the lowstand systems tract analog; the transgressive systems tract analog is represented by a stratigraphically condensed section, and the highstand systems tract analog is characterized by an upward-coarsening, and generally upward-shallowing, succession of strata. The diachroneity of the systems tract analogs and of sequence-bounding unconformities suggest, however, that this stratigraphic succession was most strongly influenced by tectonic forces associated with the Taconic Orogeny.

In the Taconic foreland basin of New York and Ontario, thrust- and sediment-loading drove subsidence so that the Middle to Late Ordovician Trenton carbonate ramp progressively oversteepened and collapsed. In New York, the oversteepening is represented by a stratigraphic succession in which carbonate-dominated deposits are disconformably overlain by flysch. In the Toronto, Ontario region, which was more distal to the thrust sheets and, presumably, more proximal to the Late Ordovician tectonic hinge, the disconformable relationship between the underlying carbonates and the overlying siliciclastics grades to conformity. In New York and Ontario, progressive southeast to northwest oversteepening of the carbonate ramp resulted in a geographically diachronous shift from carbonate-dominated deposition to organic-rich mud deposition; a sediment-starvation surface (a condensed section) is often associated with this shift. The siliciclastic strata that overlie the condensed section record the prograding Queenston clastic wedge. Paleocurrent and stratigraphic data suggest that movement along Taconic, or older rejuvenated, basement normal faults was an important control on basin subsidence and filling.

Smaller scale isochronous stratigraphic changes that cross-cut facies patterns may record eustatic events. These possible eustatic events include: (1) an Early Maysvillian deepening event, recorded by the Collingwood Formation in Ontario; (2) a basal-Pulaski progradational event; and (3) a mid-Queenston transgression.

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Contents

SEPM Concepts in Sedimentology and Paleontology

Tectonic and Eustatic Controls on Sedimentary Cycles

John M. Dennison
John M. Dennison
University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
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Frank R. Ettensohn
Frank R. Ettensohn
University of Kentucky, Lexington, Kentucky
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SEPM Society for Sedimentary Geology
Volume
4
ISBN electronic:
9781565762275
Publication date:
January 01, 1994

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