叠合盆地早期断陷对隆起带与凹陷带的控制——柴北缘隆起带与凹陷带的成因新认识

基于构造解析、盆-山耦合、地震剖面解释等认为,柴北缘西段隆起带与凹陷带分别受控于早、中侏罗世断陷,其中鄂博梁、冷湖构造带发育于早侏罗世"南断北超"的次级箕状断陷上.早侏罗世地层在背斜核部厚度的增大及基底由"凹"转"隆"的原因,是缘于箕状断陷北倾的高角度正断层在早侏罗世晚期—中侏罗世旋转变缓,而在晚侏罗世-白垩纪发生构造反转的结果.鄂博梁构造带与冷湖构造带属于"凹"上"隆";而昆特依凹陷带与赛什腾凹陷带发育于中侏罗世"北断南超"的次级断陷上,其凹陷是缘于中侏罗世南倾的高角度正断层在后期的构造挤压体制下不能发生构造反转,因此,昆特依、赛什腾凹陷带属于"凹"上"凹".在挤压构造体制下,叠合盆地内是发育隆起带抑或是凹陷带,关键在于早期断陷盆地陡坡带高角度正断层能否发生构造反转.

Control of the Early Faulted Depression of Superimposed Basins on Uplift Belts and Depression Belts——A new explanation for the origin of uplift belts and depression belts in the northern Qaidam Basin

Based on structural analysis,coupling relations between basins and mountains,interpretation for seismic sections,it is suggested that the uplift belts and depression belts in the western part of the northern Qaidam Basin are controlled by the early-middle Jurassic faulted depression,the Erboliang and Lenghu tectonic belts of the uplift belts are formed in an early Jurassic subsidiary half-graben faulted depression with faulting in south and overlapping in north.The increasing thickness of early Jurassic strata in the core of anticline and basement changing from depression to uplift is resulted from that the high angle normal fault dipping north of half graben faulted depression gradually rotated into low angle from late Early Jurassic to Middle Jurassic,and structural inversion from late Jurassic to cretaceous.Therefore,Erboliang and Lenghu tectonic belt belong to uplift belt over depression belt.The Kunteyi and Saishiteng depression belts are formed in a subsidiary faulted depression with faulting in north and overlapping in south in the Middle Jurassic,so that the high angle Jurassic normal faults dipping south do not occur structural inversion under the later compressive structural regime.So the Kunteyi and Saishiteng depression belts belong to depression belt over depression belt.Under a compressive structural regime,it is vital for uplifts belt and depression belts in a superimposed basin in the high angle normal faults in the steep slope zone of early faulted depression basin whether structural conversion occurs or not.