黄河三角洲地区YRD-1402孔沉积物光释光年代学与沉积环境

STUDY OF OPTICALLY STIMULATED LUMINESCENCE(OSL)CHRONOLOGY AND SEDIMENTARY ENVIRONMENTS OF THE YELLOW RIVER DELTA AREA WITH CORE YRD-1402

YRD-1402孔是位于黄河三角洲地区的40.3m全取心钻孔。通过对YRD-1402孔沉积物的沉积特征分析,结合光释光、AMS14 C测年、粒度和底栖有孔虫数据,将其自下而上分为4个沉积单元,分别为DU 4、DU 3、DU 2和DU 1。通过分析,认为DU 4以近岸浅水潮下带-滨岸沉积为主,对应于该地区第三海相层;DU 3属于河流沉积;DU 2为滨岸沼泽、滨岸至近岸浅水陆架沉积,DU 1属于AD 11—1048年形成的黄河三角洲沉积,DU 2和DU 1对应于第一海相层。光释光年代学表明第三海相层发育于氧同位素5期(MIS 5),而第二海相层被MIS 3中晚期至全新世发育的河流沉积所侵蚀。光释光测年范围可达十几万年,可以有效扩大14 C法的测年上限。样品的条件实验表明光释光测年可以很好地测定其年代值。

A 40.3mlong core of YRD-1402 was recovered in the Yellow River Delta area.Based on the observation of sedimentary characters,in combination of OSL and AMS 14 Cdating,grain-size analysis,and benthic foraminifera identification,the core is subdivided into four depositional units,DU 1to DU 4in a descending order.The DU 4was deposited in a shallow water environment from subtidal zone to coastal and corresponds to the so-called third marine sedimentary bed;and the DU 3,DU 2and DU 1were deposited in a fluvial environment,coastal marsh to coastal or shallow shelf,and the delta of the Yellow River in the period of AD 11-1048,respectively.The DU 2and DU 1correspond to the so-called first marine sedimentary bed.And the OSL chronology indicates that the DU 4(the third marine sedimentary bed)was formed in marine isotope stages 5(MIS 5).The second marine sedimentary bed is absent from the core,probably due to the river erosion during the middle to late MIS 3to early Holocene in the study area.The dating range of OSL is more than 100 ka and thus can effectively expand the dating limit of 14 C dating.The experimental conditions of the samples show that the OSL dating could be effectively used for young sediment dating.