Re-Flooding of Carbonate Bank-Tops and Initiation of Calci-Turbidite Deposition: Timing and Processes during Late Quaternary Deglacial Transitions

Jorry, Stephan J.¹, André W. Droxler¹, Emily Pohlman¹ (1) Rice University, Houston, TX

The late Quaternary has experienced important climatic variations and high-amplitude fluctuations of sea level at glacial/interglacial cycle frequency during which carbonate platform tops have been exposed and re-flooded several times. This study focuses on the timing of calci-turbidites deposited in the deep surroundings of isolated carbonate platforms. Three basins, in the Bahamas, the northern Nicaragua Rise, and the Gulf of Papua, were selected to represent pure carbonate versus mixed systems in quiescent versus tectonically active settings, and various carbonate bank top morphologies. In spite of these differences, each record illustrates a clear relationship between the timing of bank top re-flooding and initiation of significant carbonate export by gravity flows into the basins. Pure carbonate systems from the Bahamas and the Northern Nicaragua Rise show that calci-turbidite deposition started simultaneously at the 2/3 of the transgression during the MIS6/MIS5e transition. The analysis of a long-piston core from the Walton Basin (Northern Nicaragua Rise) demonstrates that the established highstand shedding model for calci-turbidite deposition in the last glacial/interglacial cycle is also applicable for the previous three 100-kyr cycles. This observation demonstrates that earthquakes did not play a major role as trigger mechanism. In the mixed siliciclastic/carbonate system of the Gulf of Papua, where a large amount of siliciclastic sandy and muddy turbidites has been accumulated in the deep Pandora Trough during the late Quaternary, the deposition of a wide and unique calci-turbidite and the onset of fine aragonite coincide with the timing of the Meltwater Pulse 1B sea-level rise (Holocene/Pleistocene transition).