Organic biomarker records of terrigenous organic matter input to the Indonesian Archipelago, western equatorial Pacific, 0-160,000 years BP: Implications for regional climate

The western equatorial Pacific is a highly dynamic region, playing a significant role in both tropical and extra-tropical climates through its strong influence on the El Niño-Southern Oscillation (ENSO) phenomenon and the position of the Inter-tropical Convergence Zone (ITCZ). While the modern behaviours of these climate systems are reasonably well understood, past behaviours are subject to debate. N-alkanes (biomarkers that are unique to terrestrial leaf waxes) can be used to monitor fluvial influx of terrigenous material to the ocean from adjacent landmasses. Here we present records of n-alkane abundance and composition from seven sediment cores along a N-S transect across the equator (6°N to 10°S) in an effort to reconstruct changes through time in the riverine delivery of terrestrial organic matter and the vegetation of the hinterland, which are both inferred to ultimately be linked to precipitation. We find that the concentration of n-alkanes is higher during glacial periods than during interglacial periods in all of our records. This could be interpreted to reflect synchronous changes in precipitation along the entire N-S transect on these timescales, rather than meridional shifts in the convection centre. Alternative interpretations will also be discussed, including the effects of variable dilution and changes in sea level, which will affect the relative position of the core sites with respect to the riverine source of the n-alkanes.