渝东构造样式分析与成因解析

详细的构造分析与解析表明,渝东经历了晚元古代—古生代弱造山与稳定的克拉通盆地、中生代强造山与周缘前陆盆地、新生代造山后与残余盆地3个发育世代;现今构造格局与样式实为多期构造变形形迹的复合、联合与叠加。从总体上看,研究区纵向上可划分为3个构造层,其区域构造形态总体呈现前展式逆冲推覆薄皮构造样式,局部构造共见有7种变形样式。其中,下构造层主要发育双重构造与断弯褶皱;中构造层多发育断弯与断展褶皱;上构造层以形成滑脱、断展与突破构造为主;形成时代大致经历了晚燕山、早喜马拉雅、晚喜马拉雅三期;总体体现西冲的NE向逆冲构造体系形成期最早、东南方向逆冲的NEE向冲褶系形成期其次、东冲的NNE—近SN向逆冲褶皱系形成期最晚。研究区北部构造形成早于中南部,北端NWW—EW向逆冲褶皱系干扰、限制着中北部NE—NEE向逆冲推覆系向北延伸,中部发育的转换(调节)带区段具有比较明显的调节作用。

PATTERN ANALYSES AND GENETIC INTERPRETATION ABOUT THE GEOTECTONICS OF YUDONG (EAST CHONGQING)

Derailed structural analyses and interpretations indicate that Yud on g area has undergone three development stages from weak orogeny and stable crato nic basin during Late Proterozoic-Paleozoic, strong orogeny and peripheral fore land basin during Mesozoic to post-orogenic and residual basin during Cenozoic, and the modern structural pattern and mode are actually resulted from compound, association and superposition of multiple stages of tectonic deformations. As a whole, the study area can be divided into three structural layers. The regional tectonic morphology is in a thin-skin structural pattern of advance propagatio n-type thrust nappe, and the local tectonics occurs in seven variant patterns. Here in the lower structural layer occur duplex structures and fault-bend folds , in the middle structural layer occur fault-bend folds and fault-propagation folds, while in the upper structural layer mainly occur surge folds, fault-prop agation folds and pop-up structures. Formation of these structures involves thr ee stages from Late Yanshanian, Early Himalayan and Late Himalayan. Generally, t he west-thrusting and NE-trending thrust structure system was formed earliest, the SE-thrusting and NEE-trending thrust fold system was formed secondly, and the east-thrusting and NNE-SN-trending thrust fold system was formed last. T he structure in the north of the study area was formed earlier than that the mid dle and south. The NWW-EW-trending nappe fold system in the north end actually disturbed and constrained the northward extension of the NE-NEE-trending thru st nappe system in the middle-north, while the transform (regulation) zone as d eveloped in the middle has obvious accommodation effect.