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Palaeoclimate indicators (clay minerals, calcareous nannofossils, stable isotopes) compared from two sections in the late Jurassic of the Volga Basin (SE Russia)статья
Статья опубликована в высокорейтинговом журнале
Информация о цитировании статьи получена из
Web of Science,
Scopus
Статья опубликована в журнале из списка Web of Science и/или Scopus
Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.
- Авторы: Ruffell A.H., Price G.D., Mutterlose J., Kessels K., Baraboshkin E., Gröcke D.R.
- Журнал: Geological Journal
- Том: 37
- Год издания: 2002
- Издательство: John Wiley & Sons Inc.
- Местоположение издательства: United States
- Первая страница: 17
- Последняя страница: 33
- DOI: 10.1002/gj.903
- Аннотация: A study of clay mineral and calcareous nannofossil abundances in late Jurassic-early Cretaceous sediments from the Volga Basin, SE Russia, is presented. From these results, we are able to compare some general patterns of mineralogical and palaeontological change for the Volga Basin to the palaeocliniate models developed for northern Europe and beyond. The two successions examined comprise calcareous mudstones with black organic-rich shale horizons, overlain by a series of phosphatic silty sands. Clay mineralogical results show a progressive decrease in kaolinite and the concomitant increase of smectite and illite through the middle Volgian, followed by an abrupt increase in kaolinite in the late Volgian. The clay mineral evidence suggests increasing aridity at the end of the Jurassic, similar, in part, to many western European successions. Because of differential setding of clay minerals, superimposed upon this possible climatic signature is likely to be the effect of relative sea-level change. Calcareous nannofossil analysis from a single section reveals a shift through the middle Volgian from low nutrient, warm water assemblages dominated by Watznaueria to cooler surface water and high nutrient assemblages dominated by Biscutum constans. These observations suggest that increased aridity is also associated with climatic cooling. Black shales are associated with increased productivity, higher sea levels and increases in smectite content. Hence, periods of low (chemical) hinterland weathering during semi-arid conditions are paradoxically associated with relatively nutrient-rich waters, and organic-rich shales. Comparison of published carbon and oxygen stable isotope results from this and other sections to the clay mineral and nannofossil data confirms the palaeoclimatic interpretation. This study significantly improves the published biostratigraphically constrained clay mineral database for this time period, because other European and North American successions are either non-marine (and thus poorly dated), absent (through penecontemporaneous erosion) or condensed.
- Добавил в систему: Барабошкин Евгений Юрьевич