Diatom biostratigraphy in sediments of ODP Sites 204-1251 and 204-1252

Sites 1251 (44°34.213'N, 125°4.440'W; 1211 m water depth) and 1252 (44°35.167'N, 125°5.569'W; 1039 m water depth) were drilled on the eastern flank of the southern summit of Hydrate Ridge off Oregon in the northeast Pacific Ocean, where well-stratified sediments were deposited at a rapid rate. Unconformities and debris flow layers of middle Pleistocene age were found at both sites. Their ages are of great importance in constructing the geohistory of Hydrate Ridge. Detailed diatom biostratigraphy of the middle to late Pleistocene of Sites 1251 and 1252 was carried out for this purpose.

对站位1251（北纬44°34.213′，西经125°4.440′；水深1211米）与站位1252（北纬44°35.167′，西经125°5.569′；水深1039米）开展的钻探作业，实施于东北太平洋俄勒冈海域外的水合物脊（Hydrate Ridge）南部峰顶东坡区域，该区域沉积物沉积速率快且层理发育完整。两处站位均发现了中更新世时期的不整合面与碎屑流沉积层。上述沉积层的年代信息，对于重建水合物脊的地质演化历史具有重要意义。为此，本研究针对站位1251与1252的中晚更新世地层开展了详细的硅藻生物地层学分析。