Sedimentary Evolution Since Palaezoic To Mesozoic In The North And Central Part Of Shanxi

The north-central Shanxi is adjacent to the eastern part of which is the Taihang Mountain intraplate orogen belt, northeast part is close to the southern tip of the Yanshan intraplate orogenic belt, northern part is not far from the northern margin of North China and the western part is close to Ordos Basin.The study area outcrops complete strata, is the ideal place to study sedimentary evolution of the basin.This paper based on north-central Shanxi Early Paleozoic-Mesozoic sedimentary basin sedimentary characteristics, lithological changes, sedimentary environment analysis,the sand body Pavavalung measurement, the framework grain types of Sandstone and Comparative Analysis of the quantity, discusses the sedimentary evolution of sedimentary basin in early Paleozoic-Mesozoic, the provenance position of late Paleozoic-Mesozoic and the parent rock combination in different periods, it is held that:1、Early Paleozoic, north-central Shanxi since Maozhuangqi of Cambrian seawater invaded from the eastern and northern, had gone through the Maozhuang period coastal depositional environment, Xuzhuang period shallow sea sedimentary environment of carbonate platform, lagoon, tidal flat, Zhangxia peried Tidal Shoal environment, Gushan period carbonate bamboo Beach Station floor-subtidal restricted sea alternating environment,Changshan period intertidal dam environment, Fengshan period restricted sea-wide sea-continental shelf environment. Ordovician has gone through the yeli period intertidal bamboo leaves beach environment,subtidal restricted sea environment and the wide sea-continental shelf alternately environment, Liangjiashan period limiting sea depositional environment, Xiamajiagou period evolution of supratidal carbonate floor-wide sea-continental shelf-tide floor and wide sea shelf alternately environment, Shangmajiagou period tidal carbonate stage floor environment-wide sea-continental shelf-intertidal lagoon environment.2、Sedimentary evolution of the Late Paleozoic sedimentary basins:In Benxi formation, north-central Shanxi is a broad coastal environment, Experienced the lagoon tidal flat-carbonate platform margin shoal-backshore the peat bog sedimentary evolution stage. Taiyuan period, the sedimentary basins of north-central Shanxi in the the delta front marine environment-delta environment, which appeared twice carbonate stage; The Shanxi period, north-central Shanxi evolved into the continental River depositional environment, which develops of the delta plain distributary channel phase and flood basin.During the deposition of Shi Hezi, Sedimentary basin of north-central Shanxi evolved into the continental rivers, lakes environment.3、Mesozoic sedimentary basin of north-central Shanxi evolved into meandering river sedimentary environment in Liujiagou period, Heshanggou period and Ermaying period.The Tongchuan period was braided river-lake delta depositional environment.Datong early, north-central Shanxi mainly developed to meandering river depositional system; Medium, growth lacustrine delta distributary channel, interdistributary bay and lake facies mudstone, silicalite.Late, mainly developed to point bar facies of meandering river and flood basin facies;In Yungang period,north-central Shanxi mainly developed to point bar facies of meandering river, levee and flood basin facies;Tianchihe period,developed to meandering river depositional environment with a typical dual structure,growth point bar facies of meandering river and river and lake facies.4、Ancient stream measurement results of north-central Shanxi late Paleozoic sedimentary basin sand show that, Late Paleozoic river flows were generally from north to south,and the terrigenous denudation area was in Yinshan area of Inner Mongolia of the north of the basin。Late Paleozoic Sandstone skeleton grain type, quantity relative ratio analysis and provenance tectonic background analysis shows Yinshan area provenance of the basin north was the tectonic background of plate uplift. Benxi-Shanxi period terrestrial resource area is in widely exposed Cambrian Ordovician, and even, in Upper Proterozoic sedimentary cover denuded. In Xiaoshihezi and Shangshihezi period, provenance tectonic action in the north side of the basin perform that to continue touplift, and weathering erosion gradually lead to ancient metamorphic rocks and the previously intrusive granite body exposed on surface, together with the distribution of a certain area of the sedimentary cover to supply provenance for sedimentary basin.5. Triassic period, terrigenous denudation area of the north-central shanxi sedimentary basins is still in the north side of the Yinshan area. The sandstone layer framework particle type and quantity relative ratio in this period show that the Yinshan area which lies North basin have been widely show off in a large area of the old metamorphic rock and premature intrusive granite,but only small sedimentary cover remains.At the same time, intermediate-acid volcanics which is form the Premature eruption of Inner Mongolia orogenic belt is also the source of the basin depoditing.6、Middle Jurassic sandstone of north-central Shanxi paleocurrent measurements indicate that the period of the ancient river flows changed, Terrigenous erosion area was in the east of the Basin,which along the Taihang Mountains, began to uplifted in the Middle Jurassic early and provided provenance to its west side basin. The Jurassic sandstone framework grain types and compared provenance tectonic background analysis showed that during the uplift, In Datong period,along the Taihang Mountains,the pre-deposition of the Permo-Carboniferous and even weathering and erosion product of the Lower Paleozoic strata was the main source, While a small amount of ancient metamorphic and weathering and erosion product of advance intrusive igneous rocks provide a secondary source for the basin sediments.To the Yungang period and Tianchi River period, the Taihang Mountains area exhumation deepen,the weathering products of extensive outcrops of ancient metamorphic rock and pre-invasive igneous rocks provided main source to basin sedimentary in the period,Meanwhile, the remnants of the sedimentary cover and the eruption of the volcanic rocks in the same period of Jurassic in east side of Taihang Mountains proved basin sediments provenance.