--> Abstract: Switch in Carbonate-Siliciclastic Sediment Delivery and Accumulation During the Last 130 KY, Gulf of Papua Shelf Edge and Adjacent Basins, by Andre W. Droxler, Jason Francis, Stephan Jorry, Brooke Carson, Jerry Dickens, and Luc Beaufort; #90078 (2008)

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Switch in Carbonate-Siliciclastic Sediment Delivery and Accumulation During the Last 130 KY, Gulf of Papua Shelf Edge and Adjacent Basins

Andre W. Droxler1, Jason Francis1, Stephan Jorry1, Brooke Carson1, Jerry Dickens1, and Luc Beaufort2
1Earth Science, Rice University, Houston, TX
2CNRS, CEREGE, Aix-en-Provence, France

During the last glacial sea level cycle (130 ky), the composition and flux of sediment, shed to and accumulated on the Gulf of Papua (GoP) shelf edges, adjacent slopes, and sea floor of Ashmore and Pandora Troughs, have changed dramatically through time. Highstand intervals, such as MIS 5e and Holocene MIS 1, are characterized by the occurrence and high fluxes of bank derived aragonite and Mg-calcite; offshore slopes and basin floors become carbonate-rich. During the early regression when sea level had fallen down to ~ 40-70 m, neritic carbonate production on atolls and barrier/back barrier reefs shut down, whereas flux of siliciclastic sediment dramatically increased across all of Ashmore Trough. The distal and central parts of Ashmore slope became sediment starved during the late sea level regression and lowstand. Its more proximal northern slope continued to receive a high flux of siliciclastics throughout the lowstand, when the GoP coastline had migrated to the modern shelf edge. A large volume of sandy and muddy siliciclastic sediment, bypassing this part of Ashmore, accumulated as numerous turbidite layers in the adjacent flat-floored and enclosed central part of Pandora Trough. The initial sea level rise during early deglaciation created favorable conditions for the establishment/growth of coralgal reefs along the modern shelf edge on top of the former lowstand siliciclastic coastal deposits. The timing of a calci-turbidite accumulation and the first appearance of bank-derived aragonite and Mg-calcite in the fine carbonate fraction in the basins coincide to a time interval when sea level had risen to ~ 50 - 40 m, marking the first re-flooding of the modern atoll tops which remained exposed for most of the glacial cycle.

 

AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas