Late Quaternary variability in sediment residence time and provenance in the Gulf of Carpentaria, northern Australia

Uranium (U) isotopes in detrital marine sediments provide a means to estimate sediment residence time—the duration particles spend in the landscape prior to deposition. When paired with physical parameters such as specific surface area, these data offer insight into sediment sourcing and transport processes. Here, we apply comminution dating to two sediment cores from the Gulf of Carpentaria (GoC), spanning the past 120 ka. Residence times were calculated using a Monte Carlo simulation under two scenarios: with and without post-depositional 234U recoil loss. The latter produced geologically consistent results, ranging from ∼5 to 38 ka, while the former yielded mostly unrealistic (negative) values.
Core MD972132, dominated by northern catchments, exhibits significantly shorter residence times (mean = 12.6 ka) than MD972133 (mean = 24.4 ka), reflecting faster sediment routing or reduced alluvial storage. Temporal trends suggest longer residence times during MIS 3, coinciding with regional aridity and limited fluvial connectivity, and shorter residence times post-LGM as sediment delivery increased with monsoonal intensification. Principal component analysis and clustering further differentiate sediment provenance between cores. Our results show that U-isotope-based residence time estimates, when integrated with sedimentological data, can resolve sediment routing dynamics in large tropical catchments and track climate-driven shifts in source–sink connectivity over glacial–interglacial cycles.