摘要
提出了对东濮凹陷沙河街组成盐环境解释的新观点。认为在东濮凹陷中自沙河街组四段沉积中晚期开始 ,海水随着海面升降 ,间歇性地进入由北东向的兰聊断裂和长垣断裂构成的古河谷。高位期 ,海水以相对暂时性抬高的形式淹没本区 ,致使凹陷南部成为向东南或南开口的河口湾 ,构成盐湖沉积的先期沉积环境 ;到低位期 ,海水退出凹陷区 ,部分海水因受东西向同沉积走滑断裂 (高平集—习城集一线 )高地的阻隔而潴留 ,局限在高平集—习城集断层至文明寨—范县断层的同沉积构造凹陷中 ,潴留海水蒸发、浓缩 ,形成盐类。在较深的凹地 ,受陆源淡水的影响较小 ,卤水浓度相对较高 ,依次沉积了具有深水沉积特点的碳酸盐岩、石膏、石盐等 ;而在水体较浅的凹地 (如砂坪、泥坪环境 ) ,则易受季节性洪水影响 ,卤水淡化 ,沉积了具有明显浅水特征的灰质泥岩。
More than sixty beds of salts and other evaporites with a thickness of nearly one thousand meters are developed in the Shahejie Formation of the Palaeogene in the Dongpu Depression. Since the evaporite deposits have close relations with the formation and accumulation of oil and gas, their origin has drawn much attentions from many researchers over last few years. Suggestions of the high mountain-deep basin and thermal brines welling up along fault from deep strata are more popular in these considerations. In contrast to these suggestions, the model that evaporite deposits resulted from episodic filling of sea water into an estuary is proposed in this paper. The salt deposits in the Shahejie Formation can be classified into 12 units and their precipitation from brine started from the middle and late period of the Shahejie Formation deposition after the sea water invaded into the palaeovalley between the Lanliao Fault and the Changyuan Fault when sea level rose. The total 12 units of salt deposits are thought to be precipitated during the middle and late period of the Shahejie Formation. During this period seawater invaded into the palaeovalley formed by the Lanliao Fault and the Changyuan Fault (NE direction) and retained by barrier which is caused probably by syndepositional Gaopingji-Xichengji strike-slip Fault(EW direction). After sea level dropped the retained seawater was concentrated in the deep or shallow settings of the drowned palaeovalley (estuary) and evaporite precipitation took place. Based on the study of ichnology and sedimentology, 12 cycles of sea level changes probably happened in the sedimentary period of the Shahejie Formation. It is worth to note here that the 12 units of salt deposits coincident with cycles of sea level changes should not be surprising.
出处
《古地理学报》
CAS
CSCD
2000年第4期66-75,共10页
Journal of Palaeogeography：Chinese Edition
基金
"八五"石油天然气总公司重点科技攻关项目 (85 - 10 3- 0 3- 0 1)
关键词
东濮凹陷
老第三系
沙河街组
沉积模式
河口湾
沉积学
Dongpu Depression, Palaeogene, salt deposits, estuary, coastal trace fossils, depositional model, sedimentology
