Investigations on sediment core Co1010 from Rauer Group, Antarctica

The Rauer Group is an archipelago in Prydz Bay, East Antarctica. The ice-free islands and the surrounding shallow marine areas provide valuable archives for the reconstruction of the late Pleistocene and Holocene environmental and climatic history of the region. Two sediment records from two marine inlets of Rauer Group have been studied for their sedimentological, geochemical, and biological characteristics. Radiocarbon ages from one of the inlets indicate ice-free conditions within the last glacial cycle, probably during the second half of Marine Isotope Stage 3. Subsequent ice sheet coverage of Rauer Group during the Last Glacial Maxiumum (LGM) can be inferred from a till layer recovered in one of the basins. The inlets became ice-free prior to 11,200 cal yr BP, when biogenic sedimentation started. Deglacial processes in the catchments, however, influenced the inlets until ~9200 cal. yr BP as evidenced by the input of minerogenic material. Marine productivity under relatively open water conditions indicates an early Holocene climate optimum until 8200 cal. yr BP, which is followed by a cooler period with increased sea ice. Warmer conditions are inferred for the mid Holocene, when both basins experienced an input of freshwater between ~5700-3500 cal. yr BP, probably due to ice-sheet melting and increased precipitation on the islands. Neoglacial cooling in the late Holocene since c. 3500 cal yr BP is reflected by an increase in sea ice in both inlets.劳尔群岛（Rauer Group）是东南极洲（East Antarctica）普里兹湾（Prydz Bay）内的群岛群。无冰岛屿及周边浅海区域为该区域晚更新世（late Pleistocene）与全新世（Holocene）环境及气候历史的重建提供了珍贵的研究载体。研究人员针对劳尔群岛两处海湾的沉积记录，对其沉积学、地球化学及生物学特征开展了系统研究。其中一处海湾的放射性碳年代（radiocarbon ages）数据显示，末次冰期旋回内该区域曾处于无冰状态，大概率处于海洋同位素第3阶段（Marine Isotope Stage 3）的后半段。从其中一个盆地获取的冰碛层（till layer）可推断，劳尔群岛在末次冰盛期（Last Glacial Maximum，LGM）期间曾被冰盖覆盖。两处海湾于距今11200校准年（cal yr BP）前便已脱离冰盖覆盖，彼时生物沉积作用（biogenic sedimentation）正式启动。不过，流域内的冰退过程直至约9200校准年BP仍对海湾产生影响，这一点可通过陆源矿物物质（minerogenic material）的输入得到佐证。相对开阔水域环境下的海洋生产力（marine productivity）数据表明，全新世早期存在气候适宜期，直至距今8200校准年BP；此后则进入海冰（sea ice）增多的气候转凉阶段。中全新世时期的气候被推断为偏暖，彼时两个盆地均在约5700~3500校准年BP期间接收淡水输入，这可能源于冰盖消融及岛屿上的降水增加。约3500校准年BP以来的全新世晚期出现新冰期降温（neoglacial cooling），其表现为两处海湾的海冰占比均有所上升。