渤海湾泥质海岸带近现代地质环境变化研究(Ⅱ):成果与讨论  

GEO-ENVIRONMENTAL CHANGES ON THE BOHAI BAY MUDDY COAST(Ⅱ): RESULTS AND DISCUSSIONS

作　　者：王宏[1] 

机构地区：[1]中国地质调查局天津地质矿产研究所,天津300170

出　　处：《第四纪研究》2003年第4期393-403,共11页Quaternary Sciences

基　　金：中国地质调查局国土资源大调查项目 (批准号 :1 9961 3 0 0 0 0 1 4;0 1 0 0 2 0 1 1 0 94;0 1 992 0 1 1 0 5 4和 70 2 0 1 2 0 1 0 0 5 )资助

摘　　要：渤海湾泥质海岸带国土资源大调查以其特有的方法、手段和要求 ,获得了一批带有地质调查特点的、关于全新世地层与近现代地质环境变化的阶段性成果 ,主要包括 :1 )该地区海岸带全新世地层具有 4种沉积类型 :(A)远离海岸的传统的“三分”型 ;(B)海相层与陆 (海陆过渡 )相层的多次交替 ;(C)末次冰期后期未接受沉积 ,全新统半咸水的海陆过渡相直接覆于历时约 1 0～ 2 0ka的沉积间断面上 ,向上 ,进一步发育为海相层 ;(D)沿海低洼地区在末次盛冰期后的晚更新世晚期即已进入海侵阶段 ,晚更新世晚期与全新世早期的海陆过渡相沉积是连续的 ,向上继续发育海相层。 2 )从以海水影响为主的开放潮坪 (及浅海区 )环境转变为 (陆源影响逐渐加强的 )湖 -盐沼环境 ,是研究区中晚全新世地质环境转变的重要特征 ,建立了表征这两种不同环境的非正式地层单位 (“灰色单元”与“黄色单元”)。 3)牡蛎礁与贝壳堤的对比方案 ,以牡蛎礁对应潮坪的贝类繁盛期 ,牡蛎礁中的水平再搬运夹层和 /或上覆泥质盖层(往往形成“岭地”)对应贝壳堤成堤。 4)大比例尺区调地质点 (浅孔 )揭示了中晚全新世 (近现代 )地质环境变化 ,编绘出约 45 0 0calB .P .以来小于 1ka时段的二维、假三维环境系列图。一个实例是Ⅱ贝壳堤向陆侧的洼地甚至早于?This article is a general and brief view of our results achieved in the muddy coastal geological investigation, a part of the National Land Resource Investigations, on the Bohai Bay coast during the recent years. (1) For the coastal Holocene regime, four types of stratigraphic patterns are found (A) Traditional ‘triple' subdivision of the Holocene strata often exist on the distal belt apart from the shore; (B) Interfingering between marine and terrestrial deposits;(C) A big gas, lasted 10 to 20 ka , existed in between the LGM and early Holocene. Holocene deposition started directly from brackish deposits; and (D) For depressions such as estuary, channel and neotectonic subsiding trench in the proximity of shore, marine transgression may start as early as 15 ka in the working area. No sharp boundary between Pleistocene and Holocene can be found because successive brackish deposition existed after LGM to the early Holocene. (2) ‘Binary structure', characterized by change from open tidal flat with seawater influence to the lagoonal and salt marshy environment with marine and terrestrial influences during the mid to late Holocene. For easier use in field, this ‘informal units' are called as the ‘Gray Unit' and ‘Yellow Unit', respectively. (3) A working hypothesis of correlating between the oyster reefs and cheniers suggests that the building up of the oyster reef body was simultaneously with the thriving of molluscan shells on the muddy intertidal zone during the calm period; while the reworked oyster shells/shelly fragment beds, intercalated in the reef body were in phase with the chenier construction (i.e. to pile up of the shells) during the unstable period. (4) Coastal mapping enables pseudo 3D representation of recent and present geo environmental changes of the late Holocene with resolution of less 1 ka. A paradigm is exemplified that a buried depression, being earlier than the Chenier Ⅱ, existed at the landward side of the chenier. A buried linear ridge, NNW direction, margining the d

关 键 词：渤海湾 泥质 海岸带 近现代地质环境变化 全新世沉积结构类型 全新世地层 贝壳堤 牡蛎礁 

分 类 号：P737.1[天文地球—海洋地质]