Early Cretaceous fault-depression development characteristics of western Tabei sag, Erlian Basin
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摘要: 本文通过选取二连盆地塔北凹陷西部地区3条典型地震剖面,运用2D Move软件分别对其进行平衡剖面恢复以及伸展量、伸展率的计算,分析了塔北凹陷早白垩世以来地质演化过程和构造演化特征。研究结果表明:(1)塔北凹陷整体受北西侧主干正断层的影响,形成西断东超形态的“单断式箕状”断陷湖盆,垂向上具有“下断上坳”的结构特征。(2)塔北凹陷各时期的伸展量、伸展率变化特征与构造演化历程相耦合,呈现出先增强后减弱,表明伸展作用 “由弱向强再减弱”的趋势。(3)塔北凹陷主要经历了四期构造运动:①阿尔善组沉积时期,塔北凹陷断裂初始发育,沉降受正断层活动控制,塔北凹陷初具雏形;②腾格尔组沉积时期,凹陷内部断裂持续发育,整体受断陷控制明显,伸展量和伸展率逐渐增大,并且在腾格尔组二段沉积时期达到顶峰;③赛汉组沉积时期凹陷整体受断裂影响微弱,沉积中心逐渐远离主干断层,总体表现为坳陷沉降和超覆不整合发育;④赛汉组沉积末期至今,断陷活动消亡,盆地逐渐收缩,地形趋于平缓,此后塔北凹陷一直处于抬升状态。Abstract: This study restored the balanced cross sections of the Tabei sag and calculated the extension amounts and extension rates of the sag using three typical seismic profiles selected from the western Tabei sag,Erlian Basin using the 2D Move software.Then,it analyzed the geological and tectonic evolution characteristics of the Tabei sag since the Early Cretaceous.The results indicate that:(1)Due to the effects of the main normal fault layer on the northwest side,the whole Tabei sag has evolved into a single-faulted dustpan-shaped faulted lake basin that is faulted in the west and is overlapped in the east.Moreover,it consists of a fault in the lower part and a depression in the upper part vertically.(2)The variation characteristics of the extension amounts and extension rates in each period of the Tabei sag match the tectonic evolution process of the sag,and all of them show a strong to weak trend,indicating that the extension in the Tabei sag is in a weak-strong-weak trend.(3)The Tabei sag mainly underwent four tectonic movements:①During the sedimentary period of the Aershan Formation,the faults in the Tabei sag began to develop,the sag subsided under the control of normal fault activities, and the Tabei sag began to take shape.②During the sedimentary period of the Tenggeer formation,the faults inside the sag continued to develop,and the whole sag was significantly controlled by the fault depression.The extension amount and extension rate gradually increased and reached their peaks during the upper Tenggeer formation.③During the sedimentary period of the Saihan formation,the Tabei sag was slightly affected by faults overall,and the sedimentary center was gradually far away from the main fault. During this period, the Tabei sag was characterized by depression,subsidence,and overlap unconformity.④Since the end of the Saihan formation,the fault depression activities have disappeared,the basin has gradually contracted, and the terrain has tended to be flat.Since then,the Tabei sag has been continuously uplifting.
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Key words:
- balanced cross section /
- tectonic characteristic /
- tectonic evolution /
- Tabei sag /
- Erlian Basin
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