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苏北盆地晚白垩世—新近纪原型盆地分析

舒良树, 王博, 王良书, 何光玉   

  1. 南京大学 地球科学系, 南京 210093
  • 收稿日期:2005-12-20 修回日期:2005-12-20 出版日期:2005-12-20 发布日期:2005-12-20

Analysis of Northern Jiangsu Prototype Basin from Late Cretaceous to Neogene

SHU Liang-shu, WANG Bo, WANG Liang-shu, HE Guang-yu   

  1. Department of Earth Sciences, Nanjing University, Nanjing 210093, China
  • Received:2005-12-20 Revised:2005-12-20 Online:2005-12-20 Published:2005-12-20

摘要: 苏北盆地是我国东部中新生代箕状含油气盆地群,主要由东台坳陷、盐-阜坳陷和建湖隆起三大构造单元组成;坳中有凸,隆中有凹,一系列凸、凹构造组成盆地的二级单元。运用盆地原型分析方法,对盆地的蚀源区、沉降史、沉积中心、盆地边界构造和沉积间断等进行了研究,并估算了沉降量和剥蚀量。在此基础上,提出苏北盆地的形成经历了挤压的前陆盆地、弧后扩张的裂陷盆地、大规模拉张的断陷盆地和热沉降的坳陷盆地等四个演化阶段;认为盆地沉积物主要来自5个蚀源区:NE面的滨海隆起、NW面的鲁苏隆起、西面的大别山、SW面的张八岭以及南面的扬州一宁镇古生代沉积岩区;提出建湖隆起从始新世末期以来长期处于暴露和剥蚀状态,有条件为北侧的盐阜坳陷、南侧的东台坳陷提供部分成油气物质的认识。进一步确定苏北盆地曾经历过仪征、吴堡、真武和三垛等4次抬升剥蚀事件,这些事件对不对称箕状盆地的形成起了很大的作用。区内盆地的南侧边界多呈上陡下缓的“犁式”正断层,并呈阶梯状逐次朝北下掉,盆地北侧岩层与下伏层多呈超覆关系,形成“南断北超”的盆地面貌。主断层常出现上部下滑(新)、下部逆冲(老)的反转构造现象,因而苏北盆地具有多期复合迭加的特点。本区沉积中心多表现为不对称的深凹区,沉积厚度巨大,是研究区生油层系的重要场昕。

Abstract: The Northern Jiangsu basin is an oil-gas bearing half graben-like basin of Middle Caenozoic era in Eastern China, and is mainly made up of three structural units: the Dongtai sag, the Yancheng - Funing sag and the Jianhu upheaval. The heaves in sags and depressions in upheavals are the minor units of the basin. Based on the prototype analysis method, this paper deals with erosion source area, subsidence history, evolution of sedimentation center, borderline structure and sedimentation intervals of the northern Jiangsu basin, and also estimates its subsidence quantity and denudation quantity. The paper suggests that basin's formation and evolution process can be divided into four stages: compressed foreland basin, back arc tensile rift basin, massive tensile fault basin and heatsinking sag basin. Its rich sediments came from following five erosion source areas: the Binhai upheaval on the northeast of the basin, the Shandong- Jiangsu upheaval on the northwest of the basin, the Dabie mountain on the west of the basin, the Zhangbaling mountains on the southwest of the basin, and the Paleozoic sedimentary area of Yangzhou - Nanjing and Zhenjiang on the south of the basin ; There were four uplifting and denudation events ( the Yizheng event, the Wubao event, the Zhenwu event and the Sanduo event) during the basin evolution, which played a very important role for the formation of the asymmetric dustpan-shaped basin. The resumed subsidence history of the basin commendably reflects the evolution history of the basin from Late Cretaceous to Neogene.