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Ruban D.A.,Southern Federal University | Zorina S.O.,Central Research Institute of Geology of Industrial Minerals | Conrad C.P.,University of Hawaii at Manoa
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2010

A detailed examination of transgressions and regressions that occurred during the Thanetian (58.7-55.8. Ma) may provide an important constraint on the global palaeoenvironment. Seven tectonically "stable" regions (the eastern Russian Platform, Northwestern Europe, Northwestern Africa, Northeastern Africa, the Arabian Platform, the northern Gulf of Mexico, and Southern Australia), represent exceptional records of transgressive-regressive (T-R) cyclicity. Their chronostratigraphic frameworks are sufficiently well constrained to permit accurate correlation. Surprisingly, except for a generally regressive trend occurring in the late Thanetian, no common T-R cycles can be delineated, which indicates an absence of global-scale T-R cyclicity during the Thanetian. Furthermore, we find no clear correspondence between documented T-R patterns and previously reported eustatic changes. We suggest that a warm climate and an absence of major glaciations in the early-middle Thanetian, coupled with only slow eustatic change expected from tectonic processes, stabilized Thanetian eustatic sea level. Regional subsidence or uplift, possibly generated by mantle flow in the form of dynamic topography, governed transgressions and regressions locally and resulted in an inconsistency between T-R cycles in different parts of the globe. The late Thanetian regressive episode, which preceded the Paleocene-Eocene Thermal Maximum, may be linked to an advance of glaciation. © 2010 Elsevier B.V. Source


Ruban D.A.,Southern Federal University | Zorina S.O.,Central Research Institute of Geology of Industrial Minerals | Conrad C.P.,University of Hawaii at Manoa | Afanasieva N.I.,Central Research Institute of Geology of Industrial Minerals
Proceedings of the Geologists' Association | Year: 2012

Chronostratigraphically-justified records of regional transgressions and regressions are important for understanding the nature of the Paleocene shoreline shifts on a global scale. Review of previously synthesized data from 7 tectonically "stable" regions, namely the eastern Russian Platform, Northwestern Europe, Northwestern Africa, Northeastern Africa, the Arabian Platform, the northern Gulf of Mexico, and Southern Australia, allows a comparison of transgressions and regressions interpreted in these regions. No common patterns are found in the early Danian and late Selandian, which reflects small or zero eustatic fluctuations that are overwhelmed locally on coastlines by regional tectonic motions and local changes in dynamic support of surface topography by mantle flow. Sea level was stabilized during these stages by a warm climate and a lack of planetary-scale tectonic changes. We have detected a middle-late Danian regression that occurred in 5 of 7 study regions, and can be explained by glacial advance at ∼62-63. Ma or by concurrent subduction of the Izanagi-Pacific ridge beneath eastern Asia. An early-middle Selandian transgression also occurred in 5 regions, probably, as a result of a hyperthermal at ∼61. Ma that coincided with emplacement of large igneous provinces in the oceanic domain. Both events are characterized by significant diachroneity, which can also be explained by the influence of regional tectonic subsidence or uplift. Results of the present study permit us to propose a tentative framework for a new Paleocene eustatic curve that is constrained globally using available records of transgressions and regressions. © 2011 The Geologists' Association. Source


Ruban D.A.,Southern Federal University | Zorina S.O.,Central Research Institute of Geology of Industrial Minerals | Zorina S.O.,Kazan Federal University
Journal of African Earth Sciences | Year: 2015

In their recent paper, Farouk and El-Sorogy (2015) present a reconstruction of the Danian-Selandian relative sea-level changes for the Western Desert of Egypt and an interpretation of eustatic versus tectonic controls on the latter. However, the relative sea-level changes should be distinguished from the shoreline shifts (also for the purposes of inter-regional comparisons). From three alternative global curves, two confirm the authors' conclusions, although it is questionable whether these curves are suitable for the purposes of such an analysis. It cannot be excluded that the relative sea-level fall in the late Danian was caused by the same regional tectonic uplift that resulted in the hiatus at the Danian/Selandian boundary. More research (including quantitative palaeobathymetric modelling) is necessary to understand the relative importance of the eustatic and tectonic controls on the sea-level changes established in the Western Desert of Egypt. © 2015 Elsevier Ltd. Source

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