Middle and Late Quaternary Depositional Sequences and Cycles in the Eastern Mediterranean
- Dorrik A. V. Stow
Published Online: 29 APR 2009
Copyright © 1992 The International Association of Sedimentologists
Deep-Water Turbidite Systems
How to Cite
Murat, A. and Got, H. (1991) Middle and Late Quaternary Depositional Sequences and Cycles in the Eastern Mediterranean, in Deep-Water Turbidite Systems (ed D. A. V. Stow), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444304473.ch21
Department of Geology, University of Southampton, UK
- Published Online: 29 APR 2009
- Published Print: 11 NOV 1991
Print ISBN: 9780632032624
Online ISBN: 9781444304473
- Quaternary sediments;
- hemipelagic sediments;
- oceanographic conditions;
- interplaying factors
Although most of the Quaternary sediments of the eastern Mediterranean appear reworked, extensive areas of hemipelagic sediments occur, mainly in the central part of the basin (Mediterranean Ridge). The most obvious character of these muddy sediments is the numerous changes in colour. They result from the organic carbon content as well as from concentration and chemical form of metallic elements (Mn, Fe, Cu, Zn). The succession of coloured layers is arranged into sequences developed between two sharp contacts; a complete sequence involves five lithofacies, from an oxidized layer at the base to a reduced sapropel at the top, and displays progressive internal changes of colour from ochre, beige, greyish-beige, grey and black layers: several sequence-variants (top-truncated, base-truncated, recurrent) are identified. These sequences are a consequence of changes in oceanographic conditions, i.e. from oxidizing to reduced environments, resulting in different organic and mineral contents.
Based on detailed studies of Quaternary sediments collected by coring, a synthesized standard succession representative of the ordered sequences in the eastern Mediterranean is proposed, from about 650 000 yr as deduced from the calculated rate of sedimentation of 1.7 mm 1000 yr−1. This succession appears modulated by cyclic events: large-scale periods (200 000 yr) of reduced and oxidized sequences correlate with major alternate phases of flooding and reduced flow of the Nile River during the Quaternary. Subsequent sequences of shorter time-scale (20 000–50 000 yr) results from two factors: heaviest monsoons leading to an increase of the influx of the Nile River and global climatic changes (Eurasian ice sheet meltwater); these two factors act synchronously or independently along the studied time-span.
These interplaying factors result in periodic stages of increasingly restricted conditions in the basin and explain the complexity of the eastern Mediterranean succession, at least since 650 000 yr ago.