PALEOCEANOGRAPHIC CHANGES IN THE TIMOR AND FLORES SEAS DURING THE LAST GLACIAL MAXIMUM AND DEGLACIATION: THE IMPORTANCE OF 230TH NORMALIZATION PROXY

This study utilizes the ²³⁰Th normalization method to estimate particle fluxes and focusing factors in two cores from the Flores and Timor Seas. In the Flores Sea both the mass accumulation rates (MARs) and ²³⁰Th normalized fluxes indicate higher productivity during the Last Glacial Maximum than during the Holocene, which is in agreement with other studies from this oceanographic region. In the Timor Sea the MARs indicate higher productivity during the Last Glacial Maximum, however the ²³⁰Th normalized fluxes show no change. These results imply that post- or syn- depositional addition of lateral sediment may be a significant factor in the Timor Sea. Focusing factors derived from the ²³⁰Th data support this theory, where values are Ψ = >15 during the LGM, Ψ = >12 at times during the deglaciation, and Ψ = >9 during the Holocene. We offer three possible explanations for the high focusing factors in the Timor Sea: 1) deep-water current-enhanced deposition; 2) sea-level driven downslope movement on the Sahul Shelf; and/or 3) sediment supply from the Java arc-continent collision. We favor the 3^rd explanation, sediment supply from the Java arc-continent collision, where lateral sediment focusing in the Timor Sea would have been sourced from the arc-continent collision. This explains the lack of sediment focusing in the Flores Sea that is shielded from the arc-continent collision, and receives significantly lower contributions of arc-continent collision derived sediment. This study highlights the importance of accurately reconstructing particle fluxes, and the advantages of the ²³⁰Th normalized flux technique.