华北地台区古近纪—新近纪岩相古地理特征

Characteristics of lithofacies paleogeography during Paleogene-Neogene in the area of North China platform

华北地台区古近系—新近系在渤海湾盆地非常发育,在南华北地区也有较大厚度,而在鄂尔多斯盆地则不甚发育,仅在西北部有少量沉积。渤海湾盆地古近纪以断陷型沉积为主,主要为滨浅湖相沉积,物源来自多个方向,如北部的燕山褶皱带、西部的太行山隆起、南部的鲁西隆起、东部的辽东隆起区以及盆地内部的沧县隆起和埕宁隆起等。南华北地区古近纪发育大小不一多个沉积中心,以河流相沉积为主;鄂尔多斯盆地古近纪仅在西北部出现沉积,发育河流相,缺失古新统—始新统沉积。新近系沉积区主要位于渤海湾盆地、南华北地区以及鄂尔多斯盆地外围的地堑中,主要为河流相和滨浅湖相沉积。新近纪早期渤海湾盆地大面积隆升,导致湖盆收缩,部分地区遭受剥蚀夷平,中晚期盆地整体形成统一坳陷,主要为河流相沉积,局部发育滨浅湖相;南华北地区进入裂谷期后坳陷发育阶段,大面积接受沉积,主要发育河流相沉积。华北地台区西部沿鄂尔多斯盆地周缘形成了一套以河流相与滨浅湖相为主的山前盆地沉积。华北地台区古近纪—新近纪油气的有利勘探区域为渤海湾盆地。

Paleogene-Neogene strata in the area of North China platform is very thick in Bohai Bay basin, but relatively thin in southern North China. In the Ordos basin, however, Paleogene-Neogene strata are only developed in northwest area. During Paleogene, the main sedimentary type in Bohai Bay basin was rift-type deposition and the main sedimentary facies were shore- shallow lake, whose source came from multiple areas, such as Yanshan fold belt in the north, Taihang Mountain uplift in the west, Luxi uplift in the south, Liaodong uplift in the east and Cangxian uplift and Chengning uplift in the interior of the basin. The southern North China was divided into many depressions with different sizes during Paleogene, with the development of sediments of fluvial facies. During Paleogene, the deposition only occurred in the northwest of Ordos basin, where fluvial sediments were developed. During Neogene, sedimentary zones were mainly located in the Bohai Bay basin, southern North China and the peripheral graben of Erdos basin, mainly with the development of fluvial facies and shore-shallow lacustrine facies. Large areas of Bohai Bay basin were uplifted during early Neogene, leading to the shrinkage of the lake basin and the denudation of parts of the areas. During the mid-late Neogene the basin formed a unified depression, the sedimentary facies were mainly fluvial facies and locally shore-shallow lacustrine facies. Southern North China entered into the depression development stage after rifting during Neogene, when large areas accepted deposition and developed fluvial facies. The western region along the periphery of the basin of Ordos formed a set of fluvial facies and shore shallow lake facies foreland basin deposits. Favorable exploration region of oil and gas was Bohai Bay basin during Paleogene-Neogene.