Turonian Oceanic Red Beds in the Eastern Alps: Concepts for palaeoceanographic changes in the Mediterranean Tethys.

Author(s)

Stephanie Neuhuber, Michael Wagreich, Ines Wendler, Christoph Spötl

Abstract

Several transitions of Lower to Middle Turonian pelagic marl¿limestone-cycles into Oceanic Red Beds were studied at high

resolution to gain a better understanding of the Tethyan marine system before and during red bed initiation and development.

Samples were analysed for mineralogy, geochemistry, and stable isotope composition. In particular, carbonate geochemistry of

diagenetically largely unaltered calcite was used to explore palaeoceanographic changes in the western Tethys. Principal component

analysis of carbonate chemical data showed that the development of red coloured pelagic sediments is accompanied by a

shift towards highly oligotrophic conditions in the surface ocean as well as a decrease in hydrothermal activity. The formation of

red beds is most likely associated with a shift towards more oxic conditions in basins with black shale deposits that eventually

resulted in enrichment of thiophile elements in the entire basin. Depletion in nutrients (most likely phosphate) and red bed

deposition followed the maximum flooding in the Early Turonian. Highly productive marsh areas from the proximal European

shelf were reworked and supplied nutrients during transgression. A gradual nutrient depletion during sea level highstand might be

the cause of significantly diminished nutrient availability. Carbonate production in this low latitude setting was influenced by

orbital variation in insolation (20 ka cycle). Stable carbon isotope stratigraphy reveals low sedimentation rates (between 1 and

7 mm/kyr) and a duration of episodes of Cretaceous oceanic red bed deposition between 30 and 360 kyrs.

Organisation(s)

Department of Geology

External organisation(s)

Universität Bremen, Leopold-Franzens-Universität Innsbruck

Journal

Palaeogeography, Palaeoclimatology, Palaeoecology

Volume

251

Pages

222-238

No. of pages

17

ISSN

0031-0182

Publication date

2007

Peer reviewed

Yes

Austrian Fields of Science 2012

105121 Sedimentology

Sustainable Development Goals

SDG 14 - Life Below Water

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