Date of Award

Spring 1997

Project Type

Dissertation

Program or Major

Earth Sciences: Geology

Degree Name

Doctor of Philosophy

First Advisor

Dork Sahagian

Abstract

Quantified Eustatic Curve (QEC) for Bajocian (Mid Jurassic) through Santonian (Upper Cretaceous) was constructed on the basis of the stratigraphy of the Russian Platform. The Mesozoic tectonic stability of the central part of the Russian Platform provided a valid frame of reference upon which to base the eustatic curve. As such, this curve can be considered a reliable representation of eustasy. The stratigraphic hiatuses left by unconformities in the central part of the Russian Platform were filled with stratigraphic information from the more continuous stratigraphy of the subsiding regions such as Ryazan Saratov Trough and Northern Siberia. The curve makes it possible to filter the eustatic signal from basin stratigraphic data (in any basin) and thereby quantify basin subsidence and sedimentation history more accurately than previously possible.

In order to test its validity the QEC was compared to the existing eustatic reconstructions for Jurassic-Cretaceous of the European and U.S. mid-continent sections. Good correlation (within limits of biostratigraphic resolution) of sea-level events interpreted from the regions with different tectonic histories made it possible to prove eustatic nature of several sea-level events. These include transgressive/highstand episodes: (1) late Bathonian; (2) late Callovian; (3) middle Oxfordian; (4) late Oxfordian; (5) late Albian; (6) Cenomanian/Turonian boundary; (7) mid-Volgian, and regressive events such as: (1) latest early Oxfordian; (2) middle late Oxfordian. Good agreement with some discrepancies was found for: early-mid Callovian, Kimmeridgian, Hauterivian, Aptian, Late Albian-Turonian intervals of the QEC. Additional testing is needed to prove their eustatic origin.

West Siberian basin served as a first site for an application of the QEC. Sequence stratigraphic analysis of the Jurassic and Neocomian sections of the selected regions in West Siberia led to identification of depositional sequences and an improved understanding of their depositional histories. Good correlation (100% correspondence for Oxfordian) was found between the QEC and sea-level change patterns inferred from Late Bathonian-Kimmeridgian and Valanginian-Hauterivian stratigraphic intervals of West Siberia. This result demonstrates the main role of eustasy as a factor controlling the deposition of the Mid-Upper Jurassic and "Clinoform Neocomian" sections.

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