Abstract:
By the depositional sequence, characteristics of petrology, paleo-ecology and landscape characteristics, this article discussed the cretaceous depositional system in Xinjiang Basin, Jiangxi. The author first discusses the relationship between the depositional system and Danxia landform. There are four kinds of depositional systems in Cretaceous of Xinjiang Basin: alluviation (proluvial), delta, lake, fan delta. Lower Cretaceous are of mainly semideep-deep lacustrine facies and fan delta sedimentary facies. In upper Cretaceous, the sedimentary facies distribution from south to north are flood alluvial facies, braided river, delta, beach-shallow lake, delta, braided river, flood alluvial facies. Further studied found that developed a large number of interconnected alluvial fan apron in the North and South margins of Xinjiang Basin, While the typical Danxia landforms are developed within a few places. The reason is not all of the alluvial fan can formed Danxia landform, the conditions of Danxia landform development is preserved much period superposition of the alluvial fan. According to the principle of sequence stratigraphy, must have certain space to make every alluvial fan product can be preserved. Through detailed field observation found that alluvial fan can develop deep valley only in the place of development of fracture. Deep valley can preserved alluvial fan to provide material basis of Danxia landforms. Because there is not enough space developed in Piedmont slope of the Multi stage alluvial fan, at long-term denudation area, is not easy to preserve, can not form the Danxia landforms, or Danxia landforms are small, scattered. In addition, Danxia landform development controlled by sedimentary subfacies and phase. Mainly for the continental basin filling homogeneity degree difference, difference between clastic granularity and cementation state of different sedimentary facies, resistant to weathering ability and ways is different. For example, the micro phase glutenite of main channel , braided stream in alluvial system conglomerate relatively hard, resistant to weathering and erosion capability. But sheetflood with relatively fine sediments such as sandstone, siltstone weathering resistant ability is weak, easily erosion by weathering and water. After the relatively weak interlayer difference weathering and erosion, mountain gravity unbalance, collapse along vertical joints, hard conglomerate, glutenite formed red cliffs, different modelling stone, or a similar strip protrusions or depressions, larger pits can be further developed into rock grooves or cave.The research results show that the Danxia landform of Xinjiang Basin spatial distribution and basin alluvial fan, braided river facies distribution has a good consistency, its developmental types obviously affected by sedimentary subfacies and facies.
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