渤海湾西岸全新世地层的分段与划组

Segmentation and grouping for the Holocence epoch strata in the west coast of Bohai Gulf

本文以岩性地层、气候地层(CaCO_3含量、古温度和Rb/Sr比值等)、年代地层、沉积化学地层和生物组合地层等资料为基础,根据地层规范以及建组要求将渤海湾西岸全新世地层划分为3个组:独流镇组(Qh_3dl)、大黄洼组(Qh_2dh)和西翟庄组(Qh_1xz)。其地层埋深界线及测年界线分别为:晚全新世独流镇组(Qh_3dl)与中全新世大黄洼组(Qh_2dh)的分组埋深界线为3.70 m,^(14)C年龄界线大致为2 820±80 a B.P.～2 390±60 a B.P.左右;中全新世大黄洼组(Qh_2dh)与早全新世西翟庄组(Qh_1xz)的分组埋深界线为14.10 m,^(14)C年龄界线大致为7 800±120 a B.P.～8 650±85 a B.P.左右;早全新世西翟庄组(Qh_1xz)与晚更新世塘沽组(QP_3tg)的分组埋深界线为18.70 m,测年^(14)C年龄界线大致为9 405±120 a B.P.～10 300±790 a B.P.左右。根据沉积地球化学环境指标(CaCO_3含量、古温度和Rb/Sr比值等)划分出第Ⅰ气候冷段～第Ⅴ气候冷段;根据C_(org)/P_2O_5、Fe^2/Fe^3等含量曲线综合分析划出第Ⅰ·还原带～第Ⅴ·还原带。综合分析显示:气候冷期时往往处于还原环境,与此同时,海平面则呈波动下降趋势。

Based on the projects of “Comprehensive Geological Survey in Ninghe County, Tianjin” , “Comprehensive Geological Survey in Jinghai County, Tianjin” and “Qilihai Geological Park”, a few drilling holes are setted out in this area, take ZK01-ZK09 holes, B HN10 hole and BJM18 hole, SQO1-SQ29 holes and TK01-TK09 holes for example, the stratotype section of the Holocence epoch strata in the west coast of Bohai Gulf are segmented and divided into groups. According to stratigraphic code and grouping requirement, combing the data of lithologic stratigraphy,chronostratigraphy, chemistry strate and biological assemblages strate, the author divided the stratotype section of the holocence epoch strata into three groups：Duliuzhen group, Dahuangwa group, Xizhaizhuang group. The segmentation boundary between upper Holocence Duliuzhen group profiles and middle Holocence Dahuangwa group profiles are from 5. 10 m to 5.25 m; the segmentation boundary between middle Holocence Dahuangwa group profiles and lower Holocence Xizhaizhuang group profiles are from 13.80 m to 14.10 m; the segementation boundary between lower Holocence Xizhaizhuang group profiles and lower Pleistoncene Tanggu group profiles are from 18.48 m to 18.70 m. The division of Ⅰ -Ⅴ cold climate section is accordance with the chemical environment related indexes,for example,the content of CaCO3, pollen paleotemperature and the retio of Rb/Sr. The division of Ⅰ. - Ⅴ.oxidation-reduction zone is accordance with the comprehensive analysis for the concentration curve of Cors/P2O5, Fe^2＋/Fe^3＋.