渤海湾泥质海岸带近现代地质环境变化研究(Ⅰ):意义、目标与方法

GEO-ENVIRONMENTAL CHANGES ON THE BOHAI BAY MUDDY COAST (Ⅰ):SIGNIFICANCE,GOALS AND METHODS

渤海湾泥质海岸带的近现代地质环境变化研究 ,是通过两种形式 (大比例尺区域地质调查和综合研究 )在两个方面即垂向的浅表沉积物和平面上的地表形态变化同时展开的。( 1 )海岸带深覆盖区区域地质调查 ( 1∶5 0 0 0 0 )分为 4个层次 :基底 (前第四纪 )研究、早中更新世研究、晚更新世 -全新世多学科综合研究、中晚全新世 -现代多学科高分辨率综合研究。( 2 )海岸带综合研究采用多期图形对比、短半衰期同位素示踪与测年等方法 ,围绕近百年来地表形态、沉积速率变化及海岸线变迁展开。 ( 3)正在形成的系统工作方法 :包括Eijkelkamp槽型取样器获取浅表地层的无扰动岩心、岩心编录、手持GPS定位 ;少量辅助性机械钻孔岩心( 30～ 1 0 0m ,全取心 )研究 ;地质点水准 (与国家高程联网的 )测量 ;有孔虫、介形虫、孢粉、OSL、1 4 C测年 (加速器质谱法与液体闪烁计数器法 )、磁学研究和 2 1 0 Pb/1 37Cs测年 ,以及多期图形 (历史地图、地形图、航片与卫星遥感影像 )的计算机处理与对比、假三维表达的综合研究等。

As a branch of the National Land Resource Investigations, the coastal geological work has been carrying out on both coastal plain and intertidal zone along the Bohai Bay, China. This work, focused mainly on the late Pleistocene and Holocene shallow strata and the modern surficial morphological changes, helps to find out the facts of the recent and present day coastal geo environmental changes, tendencies of the changes and potential influence on the coastal sustainable development. Coastal mapping is composed of four fold objectives including the bedrock study (pre Quaternary), early to middle Pleistocene study, late Pleistocene to Holocene multidisciplinary study and, finally, as most important, late Holocene and present day multidisciplinary study with high resolution. Coastal comprehensive studies are mainly dealing with shoreline migration, morphological changes, accumulation rate in the past century. The common procedures as normal routing include detailed field logging, portable GPS loc, leveling measurement by Geodimeter for each core and Eijkelkamp coring with distribution density of 1core/1.6～3.3km 2, specific mechanical drilling boreholes of 30～100 m in depth. Detailed laboratory work consists of palaeobiostratigraphy (foraminifera, ostrocoda and pollen grain analyses), OSL/ 14 C/ 210 Pb/ 137 Cs/U series dating, palaeomagnetic study and sedimentary analysis, etc. Pseudo 3D representation has been given for the coastal mapping areas, especially for the middle to late Holocene period with time resolution of less than 1 000 years.