The Gulf of Carpentaria palaeoenvironments: OSL dating and nannofossil evidence

摘要: The Gulf of Carpentaria is a near-equatorial region, domain in which past environmental changes are not well understood, but much the world's weather has its origin. Being situated adjacent to Western Pacific Warm Pool, responsible for largest transfer heat and moisture between surface atmosphere, an epicontinental sea (maximum depth 70 m) bordered east by Torres Strait (12 m depth) west deeper Arafura Sill (53 depth), area sensitive Asian monsoon ENSO, have crucial importance on worldwide scale. Furthermore, this region could be key point monitor palaeocirculation Indian oceans that records switching off global thermohaline circulation during glacial/interglacial alternations. tectonically stable, therefore no corrections necessary when interpreting palaeo-sea level curve. Throughout Late Quaternary, times sea-level lowstands, gulf was separated from open waters oceans, forming Lake with outlet channels Sea. In 1997, six sediment cores were collected using giant piston-corer deployed Marion Dufresne, as part International MArine Global changEs Study (IMAGES). This study provides interpretation palaeoenvironments over last 180 ka means OSL dating analysis abundance distribution coccolith assemblages within series cores. usefulness Dating technique such covering marine lacustrine conditions been demonstrated establishing time frame changing environments since MIS 6.6. shallowness Carpentaria, restricted basin size, allow use Optically Stimulated Luminescence (OSL) date sediment. Indeed, these parameters mean quartz grains bleached soon before deposition thus event real deposition. From thirteen samples processed, twelve dates ranging 7 ± 1 178 18 ka, estimated three Carpentaria. These also calculation sedimentation rate, ranges 4.3 cm central 7.8 kaon western margin. results consistent modern rate observed A clear reduction starting about 90-100 ago noticed cores, however needs confirmed further other levels. Coccolithophores planktonic algae distributed ocean nearshore littoral lagoonal environments. They secrete minute calcified plates, coccoliths, major component pelagic carbonates. Coccolith preserved sediments excellent proxies palaeoceanographic conditions. lack coccoliths either due bad preservation or freshwater environment. confirm at least two non-marine/marine cycles, some short intervals, minor incursions seawater non-marine sequence. collated presented maps illustrating discrete closure breach sequences related Quaternary fluctuations, corresponding alternations When viewed together, compilation data enables development detailed spatial temporal understanding palaeoenvironmental history 6.6 (ca. ka). sedimentary record evidence dry wetter episodes interpreted intensification cyclonic activity. may linked ENSO events oceanic atmospheric processes.