Diatom abundance and stratigraphy of ODP Hole 162-983A@en

High accumulation rates and the presence of well-preserved, abundant diatoms in Site 983 sediments from the Gardar Drift gave us the opportunity to refine the Pleistocene diatom biostratigraphic resolution of the high-latitude North Atlantic. Eight Pleistocene diatom datum events are identified and, for the first time, tied directly to the oxygen isotope record and paleomagnetic stratigraphy of Site 983. These datum events are (1) the last occurrence (LO) of Proboscia curvirostris at 0.3 Ma, (2) the LO of Thalassiosira jouseae at 0.3 Ma, (3) the LO of Nitzschia reinholdii at 0.6 Ma, (4) the LO of Nitzschia fossilis at 0.68 Ma, (5) the LO of Nitzschia seminae at 0.84 Ma, (6) the first occurrence (FO) of N. seminae at 1.25 Ma, (7) the FO of Proboscia curvirostris at 1.53 Ma, and (8) the FO of Pseudoeunotia doliolus at 1.89 Ma. Most of these datums are found to be synchronous between the middle and high latitudes of the North Atlantic and the North Pacific. On the basis of these datums, four high-latitude North Atlantic diatom zones are proposed for the Pleistocene. The record of diatom abundance and preservation at Site 983 gives evidence for the influence of fluctuating Pleistocene climatic conditions on diatom productivity in the high-latitude North Atlantic.来自加达尔漂移区（Gardar Drift）的983站位（Site 983）沉积物具备较高的硅藻堆积速率，且保存完好、数量丰富，这为我们优化北大西洋高纬度区域更新世（Pleistocene）硅藻生物地层分辨率提供了可行契机。本次研究共识别出8项更新世硅藻生物地层基准面事件，并首次将其与983站位的氧同位素记录（oxygen isotope record）及古地磁地层学（paleomagnetic stratigraphy）直接建立关联。这些基准面事件分别为：1. 弯喙伪裸杆藻（Proboscia curvirostris）在0.3 Ma处的末次出现（Last Occurrence，LO）；2. 朱氏海链藻（Thalassiosira jouseae）在0.3 Ma处的末次出现（LO）；3. 莱因霍尔德菱形藻（Nitzschia reinholdii）在0.6 Ma处的末次出现（LO）；4. 化石菱形藻（Nitzschia fossilis）在0.68 Ma处的末次出现（LO）；5. 塞米纳菱形藻（Nitzschia seminae）在0.84 Ma处的末次出现（LO）；6. 塞米纳菱形藻（Nitzschia seminae）在1.25 Ma处的首次出现（First Occurrence，FO）；7. 弯喙伪裸杆藻（Proboscia curvirostris）在1.53 Ma处的首次出现（FO）；8. 囊状假真弯藻（Pseudoeunotia doliolus）在1.89 Ma处的首次出现（FO）。研究表明，多数此类基准面事件在北大西洋中高纬度与北太平洋区域呈现同步性。基于上述基准面事件，本研究为更新世建立了4个北大西洋高纬度硅藻生物地层带。983站位的硅藻丰度与保存状态记录，为更新世气候波动对北大西洋高纬度区域硅藻生产力的影响提供了实证支撑。