Formation of varve-like laminae off Pakistan: decoding 5 years of sedimentation
Published:January 01, 2002
A. Lückge, L. Reinhardt, H. Andruleit, H. Doose-Rolinski, U. Von Rad, H. Schulz, U. Treppke, 2002. "Formation of varve-like laminae off Pakistan: decoding 5 years of sedimentation", The Tectonic and Climatic Evolution of the Arabian Sea Region, P. D. Clift, D. Kroon, C. Gaedicke, J. Craig
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We studied Holocene sediments from the northeastern Arabian Sea near Pakistan, which were obtained from the same location in 1993 and 1998, to determine the composition and origin of laminated sediments for this 5 year time interval. Methods included geochemical, sedimentological and palaeontological analyses. We then compared our results with meteorological records, and satellite and sediment trap data. We suggest that short-term (few days) heavy rainfall periods in the hinterland and at the coast lead finally to flood events causing the deposition of light-coloured layers as event deposits on the continental slope. These layers are characterized by low percentages of biogenic compounds (i.e. organic matter, coccoliths and diatoms) and interpreted to have been deposited mainly during the winter season, when heavy rainfall can be expected. The thickness of the light layers seems to be related to the intensity of precipitation during a single flood event. In the 1997-1998 El Niño year, which was characterized by the strongest anomalies for the last 20 years, the thickest layer was deposited. The dark layers accumulate over the remaining larger part of the year and are characterized by an elevated input of biogenic material (marine organic matter, skeletal opal, foraminifera and coccoliths).
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The Tectonic and Climatic Evolution of the Arabian Sea Region
Over long periods of time the tectonic evolution of the solid Earth has been recognized as the major control on the development of the global climate system. Tectonic activity acts in one of two different ways to influence regional and global climate: (i) through the opening and closing of oceanic gateways and its effect on the circulation patterns in the global ocean; (ii) through the growth and erosion of orogenic belts, resulting in changes in oceanic chemistry and disruption of atmospheric circulation. The Arabian Sea region has several features that make it the best area for studies of climate and palaeoceanographic responses to tectonic activity, most notably in the context of the South Asian monsoon and its relationship to the growth of high topography in the adjacent Himalayas and Tibet.
The Tectonic and Climatic Evolution of the Arabian Sea Region brings together a collection of recent studies on the area from a wide group of international contributors. The paper range from high resolution, Holocene palaeoceanographic studies of the Pakistan margin to regional tectonic reconstructions of the ocean basin and surrounding margins throughout the Cenozoic. Marine geophysics, stratigraphy, isotope chemistry and neotectonics come together in a multidisciplinary approach to the study of interactions of land and sea. while much work remains to be done to understand fully the tectonic and climatic evolution of the Arabian Sea, a great deal has been achieved since the last major review, as detailed in the 26 contributions. This volume is essential reading for palaeoceanographers, sedimentologists and geophysicists. It will also be interest to structural geologists and those working in the petroleum industry.