Diatom abundance and stratigraphy of ODP Hole 162-983A

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.

取自加达尔漂移（Gardar Drift）983站位（Site 983）的沉积物中，沉积速率较高且保存完好、数量丰沛的硅藻，为我们提升高纬度北大西洋地区更新世硅藻生物地层分辨率提供了契机。本次研究共识别出8项更新世硅藻基准面事件，并首次将其直接锚定至983站位的氧同位素记录与古地磁地层学。这8项基准面事件分别为：（1）弯喙原杆藻（Proboscia curvirostris）于0.3 Ma时的末次出现（Last Occurrence, LO）；（2）尤氏海链藻（Thalassiosira jouseae）于0.3 Ma时的末次出现（LO）；（3）莱因霍尔德氏菱形藻（Nitzschia reinholdii）于0.6 Ma时的末次出现（LO）；（4）化石菱形藻（Nitzschia fossilis）于0.68 Ma时的末次出现（LO）；（5）种子菱形藻（Nitzschia seminae）于0.84 Ma时的末次出现（LO）；（6）种子菱形藻（N. seminae）于1.25 Ma时的首现（First Occurrence, FO）；（7）弯喙原杆藻（Proboscia curvirostris）于1.53 Ma时的首现（FO）；（8）小箱形伪真弯藻（Pseudoeunotia doliolus）于1.89 Ma时的首现（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地区具有同步性。基于上述基准面事件，本研究为更新世时期的高纬度北大西洋地区建立了4个硅藻生物地层带。983站位的硅藻丰度与保存状况记录，为更新世气候波动对高纬度北大西洋地区硅藻生产力的影响提供了直接实证。