Evaluation of Reciprocal Sedimentation during the Last Glacial Sea Level Cycle on a Tropical Mixed Siliciclastic-Carbonate Margin, Ashmore Trough, Gulf of Papua

Tropical mixed siliciclastic-carbonate systems are important for understanding global change, geochemical cycling, and resource management. Mixed margins are often evaluated by reciprocal sedimentation, a concept used to explain how variations in sea level control the distribution and accumulation of siliciclastic and carbonate sediment. This concept is rarely assessed during the last glacial interglacial cycle when sea level and precise dating techniques can constrain sediment accumulations. This study of Ashmore Trough, Gulf of Papua, integrates a full suite of data including core, seismic, and multi-beam data to better understand sedimentation and to evaluate reciprocal sedimentation in tropical mixed siliciclastic-carbonate systems.

Over the last 140 kyr, the composition and accumulation of sediment shed from the Gulf of Papua margin to surrounding slopes and basins have changed dramatically. Carbonate input to the basin reached maximum values during sea-level rise and highstand, decreased during early sea-level fall, and reached minimum values during late sea-level fall and lowstand. Siliciclastic input was greatest during early sea-level fall and late sea-level rise, abundant only on the proximal slope during late sea-level fall, and decreased during lowstand and highstand. Carbonate accumulation in Ashmore Trough was accurately predicted by reciprocal sedimentation, however, the siliciclastic record contains complexities not accounted for by this concept. The proposed depositional model demonstrates how sea level, climate change, and margin physiography all contribute to the complexity of siliciclastic accumulation. Overall, reciprocal sedimentation can be used to predict carbonate accumulation in tropical mixed siliciclastic-carbonate systems, however, a firm understanding of sea level, sedimentary processes, climate, and regional physiography is required to accurately predict the siliciclastic component.