End-Member Modeling of Siliciclastic Grain-Size Distributions: The Late Quaternary Record of Eolian and Fluvial Sediment Supply to the Arabian Sea and its Paleoclimatic Significance
Published:January 01, 1999
Maarten A. Prins, Gert Jan Weltje, 1999. "End-Member Modeling of Siliciclastic Grain-Size Distributions: The Late Quaternary Record of Eolian and Fluvial Sediment Supply to the Arabian Sea and its Paleoclimatic Significance", Numerical Experiments in Stratigraphy: Recent Advances in Stratigraphic and Sedimentologic Computer Simulations, John W. Harbaugh, W. Lynn Watney, Eugene C. Rankey, Rudy Slingerland, Robert H. Goldstein, Evan K. Franseen
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Numerical-statistical algorithms are used to model end-member grain-size distributions of pelagic and hemipelagic siliciclastic sediments of the Arabian Sea. The grain-size distributions of sediments from the Oman continental slope, the Owen Ridge, the Pakistan continental slope, and the Indus Fan can be adequately described as mixtures of three end members. The spatial variation in relative contribution of the end members is interpreted in terms of transport processes and provenance. In the western Arabian Sea, deposition is dominated by two end members that represent "proximal" and "distal" eolian dust. A third end member, which dominates the deposits of the middle Indus Fan, represents fluvial mud deposited from low-density turbidity currents (lutite flows).
At any given location, the temporal changes in the relative contribution of the end members can be interpreted in terms of climate change. The ratio of contributions of the two eolian end members (i.e., the grain-size distribution of the eolian dust) on the Owen Ridge (NIOP492) reflects the strength of the summer monsoon. Deposition on the upper Indus Fan (NIOP458) is dominated by "distal" eolian dust and fluvial mud. The ratio of contributions of eolian and fluvial sediment reflects continental aridity. The ratio of contributions of the two eolian end members (i.e., the grain-size distribution of the eolian dust) on the upper Indus Fan reflects the strength of the winter monsoon.
Our reconstruction of the late Quaternary variations in Arabian Sea monsoon climate corresponds well with interpretations of the loess-paleosol sequences on the Chinese Loess Plateau. In both areas, the bulk of the annual precipitation is confined to the summer monsoon season. Intensification of the summer monsoon during interglacials, which has been identified as the principal control on pedogenesis on the Loess Plateau, also explains increased discharge of Indus River-derived muds to the northern Arabian Sea. Independent evidence for summer monsoon strength, provided by the eolian grain-size record of the western Arabian Sea, fully supports this conclusion. The strength of the summer monsoon thus provides an aridity forcing mechanism for both the Arabian Sea and the Loess Plateau. The grain size of the eolian dust in the northern Arabian Sea and on the Loess Plateau indicates intensified winter monsoons during glacials.
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Numerical Experiments in Stratigraphy: Recent Advances in Stratigraphic and Sedimentologic Computer Simulations
Numerical Experiments in Stratigraphy: Recent Advances in Stratigraphic and Sedimentologic Computer Simulations - This volume presents the results derived from a three-day workshop held at the University of Kansas, Lawrence, Kansas, from May 15 through May 17, 1996. The objectives of the workshop were to document, characterize, demonstrate, and compare different computing procedures that have been utilized in simulating stratigraphic sequences. Both inverse and forward simulation modeling procedures are represented. The results of the workshop and the papers assembled here include: (1) an enhanced understanding of similarities and differences between models and modeling philosophies, (2) increased communication among modeling groups and geoscientists, (3) critical evaluation of applications and assessment of how models have been utilized, and (4) improvements and refinements in techniques for generating and describing model input and output.