Stable carbon and oxygen isotope ratios of foraminifera and organic carbon of ODP Hole 188-1167A (Table 2)@en

Ocean Drilling Program Leg 188, Prydz Bay, East Antarctica is part of a larger initiative to explore the Cenozoic history of the Antarctic Ice Sheet through direct drilling and sampling of the continental margins. In this paper, we present stable isotopic results from Ocean Drilling Program (ODP) Site 1167 located on the Prydz Channel Trough Mouth Fan (TMF), the first Antarctic TMF to be drilled. The foraminifer-based d18O record is interpreted along with sedimentary and downhole logging evidence to reconstruct the Quaternary glacial history of Prydz Bay and the adjacent Lambert Glacier Amery Ice Shelf System (LGAISS). We report an electron spin resonance age date of 36.9±3.3 ka at 0.45 m below sea floor and correlate suspected glacial–interglacial cycles with the global isotopic stratigraphy to improve the chronology for Site 1167. The d18O record based on planktonic (Neogloboquadrina pachyderma (s.)) and limited benthic results (Globocassidulina crassa), indicates a trend of ice sheet expansion that was interrupted by a period of reduced ice volume and possibly warmer conditions during the early–mid-Pleistocene (0.9–1.38 Ma). An increase in d18O values after ~900 ka appears to coincide with the mid-Pleistocene climate transition and the expansion of the northern hemisphere ice sheet. The d18O record in the upper 50 m of the stratigraphic section indicates as few as three glacial–interglacial cycles, tentatively assigned as marine isotopic stages (MIS) 16–21, are preserved since the Brunhes/Matuyama paleomagnetic reversal (780 ka). This suggests that there is a large unconformity near the top of the section and/or that there may have been few extreme advances of the ice sheet since the mid-Pleistocene climate transition resulting in lowered sedimentation rates on the Prydz Channel TMF. The stable isotopic record from Site 1167 is one of the few available from the area south of the Antarctic Polar Front that has been linked with the global isotopic stratigraphy. Our results suggest the potential for the recovery of useful stable isotopic records in other TMFs.南极东部普里兹湾的大洋钻探计划（Ocean Drilling Program, ODP）第188航次，是通过直接钻探与大陆边缘采样，探究南极冰盖（Antarctic Ice Sheet）新生代演化历史这一大型研究计划的组成部分。本研究报道了位于普里兹海峡槽谷口扇（Prydz Channel Trough Mouth Fan, TMF）的大洋钻探计划1167站位的稳定同位素分析结果——该站位是首个被钻探的南极槽谷口扇。基于有孔虫的δ¹⁸O记录，结合沉积学与井下测井证据，本研究重建了普里兹湾及邻近的兰伯特冰川-埃默里冰架系统（Lambert Glacier Amery Ice Shelf System, LGAISS）的第四纪冰川演化历史。我们在海底以下0.45米处获得了36.9±3.3千年的电子自旋共振（electron spin resonance）测年结果，并将疑似的冰期-间冰期旋回与全球同位素地层学进行对比，以优化1167站位的年代序列。基于浮游有孔虫（*Neogloboquadrina pachyderma*（s.））以及有限的底栖有孔虫（*Globocassidulina crassa*）数据得到的δ¹⁸O记录显示，冰盖扩张的趋势曾被早更新世-中更新世（0.9~1.38 Ma）期间的冰量减少阶段（或伴随气候变暖）打断。约900 ka之后δ¹⁸O值升高，这似乎与中更新世气候转型及北半球冰盖扩张事件相吻合。地层剖面上部50米的δ¹⁸O记录显示，自布容-松山古地磁倒转（780 ka）以来，仅保存了至少3次冰期-间冰期旋回，暂将其归为海洋同位素阶段（marine isotopic stages, MIS）16~21。这表明该剖面顶部附近存在大规模沉积不整合面，或者自中更新世气候转型以来，冰盖极少发生极端前进事件，进而导致普里兹海峡槽谷口扇的沉积速率降低。1167站位的稳定同位素记录是南极极锋（Antarctic Polar Front）以南少数可与全球同位素地层学建立关联的记录之一。本研究结果表明，在其他槽谷口扇中也具备获取有价值的稳定同位素记录的潜力。