Marine depositional events controlled by sediment supply and sea-level changes |
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| Authors: | G Einsele |
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| Institution: | (1) Geologisches Institut der Universität Tübingen, Sigwartstrasse 10, D-72076 Tübingen, Germany |
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| Abstract: | Under conditions of high fluvial or coastal sediment supply, individual sandy storm layers (tempestites) and turbidites form after significantly shorter time intervals than Milankovitch cycles. To provide the material for mass flows of very high volume, large, mountainborne rivers require about ten thousand years. With little sediment supply, however, all event deposits become rare or are missing.Third-order sequences (about 1–4 Ma) vary considerably in thickness depending on the sedimentation rates in the basins. Thick and widely extended mud flows and megabreccias are preferentially triggered by sea level fall below the shelf edge. Mixed siliciclastics-carbonate systems along the foot of carbonate shelves generally become coarser grained and poorer in carbonates during lowstands. Turbidite successions also frequently occur in lowstand deposits, but may be present in the other systems tracts as well if a delta is prograding continually.The position of tempestites in third or higher order shallow water sequences is less clear. In studies on the migration of coastal sands in relation to falling and rising sea level, one should distinguish, apart from sediment supply, between settings with and without substantial wave scour. The generation of sandy tempestites appears to be favoured if coastal progradation and wave scour operate simultaneously for example during late highstand and early lowstand. |
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| Keywords: | Depositional events Sea level changes Sediment supply |
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