Tectonic Characteristics, Formation And Evolution Of Upper Paleozoic In Luoyi-yichuan Basin, West Henan Province

In the light of the plate tectonic and the new study on the continental dynamic theories, this work is aimed to effectively trace the tectonic characteristics and evolution of upper Paleozoic in the Luoyang-yiyang-yichuan basin on the basis of the previous geological and seismic works in the study area.The Luoyang-yiyang-yichuan basin is located in the western Henan uplift, tectonically situated in the joint area of the NNE uplift and EW tectonic zone in the center of China, which is a Meso-Cenozoic fault-sag basin developed on the base of Indochina-early Yanshan folded belts.According to the geological features, the formation and the relationship of strata, the deformation diversity of strata of different period in Luoyi-yichuan basin, it can be divided into four structural layers: Sinian-lower Paleozoic structural layer;upper Palaeozoic- lower Mesozoic structural layer, Cretaceous- Paleogene structural layer, Neocene- quaternary structural layer .The tectonic characteristics of each structural layer is depicted in detail as follows: 1 Sinian-lower Paleozoic structural layerThe regional parallel unconformity betweeen the Cambrian,Ordovician and Upper- Carboniferous layers in the study area is strongly affected by the severe Caledonian -Early Hercynian tectonic events.2. Upper Paleozoic- lower Mesozoic structural layerAs a result of the Indochina and Early Yanshan tectonic compressive events, the Jurassic layer is not appeared finitely in the region and preserved in the basin. The thrust along Sanmenxia-Xiashi fault with direction from south to north bring the denudation of Paleozoic-Mesozoic strata so that the presinian layers is widely distributed in the southwest area on the fault. The prominent structural style of the large northeast region on the fault is alternate erect broad syncline and anticline developed mostly by Paleozoic and Triassic. Sanmenxia-Xiashi and Shimen-Wenquanjie thrust belts are synchronous regional faults with similar characteristics, between which is the thrust block with strong deformation, extensively developed folds and faults. The orientation of regional compress strain is approximate NW.3. Cretaceous- Paleogene structural layerThe NE and approximate EW extensional sag basin and its corresponding normal faults that control the distribution of paleogene sediments result from Mid-late Yanshan extensional tectonic events. The early Himalayan compressive tectonic events cause the deformation of Paleogene and its underlying formation and the angle unconformity between Paleogene and Neocene-quarternary in western of Henan province. The structural deformation of the Paleogene is characterized evidently by thrust block and broad folds.4. Neocene- quaternary structural layerAffected by the Mid-late Himalayan tectonic movement, the angle unconformity occurred between the Neocene- quaternary and underlying Paleogene. The tectonic settings of formation of this basin was controlled by the weak extensional depression.Through comprehensive analysis of the residual strata sequence , sedimentary system and the structural deformation characteristics of different structural layers in the Luoyi-Yichuan basin, this paper have presented a fresh tectonic evolved process that the basin has experienced:1. the Caledonian uplift and denudation stage;2. Late Paleozoic and early Mesozoic development and evolution stage of inland basin;3. Late Triassic and early Jurassic Indo-Chinese compressive fold stage;4. The Mid-Late Jurassic semi-foreland basin formation and Early Yanshan compressive deformation stage;5.Late Cretaceous and Early Tertiary fault sag basin formation and structuraldeformation stage;6. Late Tertiary -The Quaternary weak extensional-depression stage.