Milankovitch forcing of bioturbation intensity in deep-marine thin-bedded siliciclastic turbidites.
EARTH PLANET SC LETT
130 - 138.
Trace fossils have been used to infer a Milankovitch-type control on pelagic and hemipelagic sediments, but there have been no comparable studies in deep-marine siliciclastic turbidite successions. Here, we present the results of a quantitative analysis of trace-fossil abundance and intensity in an essentially continuous, Middle Eocene, 230-m-long (Well A6) core, comprising very thin- and thin-bedded siliciclastic turbidites in the deep-marine Ainsa basin, Spanish Pyrenees. After removing the sediment slides and debris flow deposits, as these represent geologically instantaneous events approximately two orders of magnitude thicker than the typical laminated turbiditic sediments in the core, spectral analysis was conducted on the bioturbation intensity data. Spectral analysis of bioturbation intensity in the A6 core suggests, for the first time from a Siliciclastic turbidite succession at a tectonically active plate margin (thrust-top basin in a foreland basin) a, cyclicity that is interpreted to reflect the 41-kyrand an similar to 112-kyr (possibly an average of the 95- and 125-kyr) Milankovitch frequencies. We propose that this drove environmental changes in bottorn-water conditions in the Ainsa basin, most likely leading to critically varying levels of oxygenation (stratification) of bottom waters. Our age model for the Ainsa basin (similar to 4 km of deep-marine sediments in similar to 10 Myr) yields an average sediment accumulation rate of -40 cm kyr(-1), that is consistent with that inferred from the spectral analysis (similar to 30 cm kyr(-1)) for fine-grained sedimentation. An implication of these results is that global environmental change, probably glacio-eustasy, acted as a driver on cleep-marine siliciclastic sedimentation patterns during the Middle Eocene. (C) 2008 Elsevier B.V. All rights reserved.
|Title:||Milankovitch forcing of bioturbation intensity in deep-marine thin-bedded siliciclastic turbidites|
|Keywords:||Milankovitch forcing, bioturbation intensity, deep-marine, siliciclastic turbidites, TRACE-FOSSIL MODEL, CALCITE COMPENSATION, BIPOLAR GLACIATION, SPANISH PYRENEES, MIDDLE EOCENE, BOTTOM WATERS, AINSA BASIN, PLEISTOCENE, SEDIMENTS, SPAIN|
|UCL classification:||UCL > School of BEAMS > Faculty of Maths and Physical Sciences > Earth Sciences|
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