西南地区二叠纪层序地层及海平面变化

Permian sequence stratigraphy and sea-level changes in southwestern China

关键词:  层序地层  海平面变化  二叠系  西南地区  特提斯型(华南型)  经典型(欧美型)

Key words:  sequence stratigraphy  sea-level change  Permian  southwestern China Tethys type(South China type)  classic type (Euramerica type)

摘要:

西南地区二叠系可划分为2个二级层序、11个三级层序,它们代表11次三级海平面升降旋回,其中有6次可与欧美地区二叠纪海平面变化相对比,它们是伦纳德(Leonardian)早期、瓜达卢普(Guadalupian)早期、瓜达卢普(Guadalupian)晚期、卡赞(Kazanian)早期、鞑靼(Tatarian)早期和鞑靼(Tatarian)晚期的海平面旋回。研究表明,该区二叠纪相对海平面变化作为全球海平面变化和同沉积构造活动相互作用的产物,它与欧美地区乃至联合古陆发展具反向效应,即具有以海侵型碳酸盐沉积序列为典型的主体海平面上升的特点。作者认为显生宙全球海平面旋回曲线的二叠纪部分总体具有两种类型或分支:其一是以海侵型碳酸盐沉积序列为主的反映海平面主体上升的特提斯型或华南型;其二是以海陆过渡—陆相海退沉积序列为主的揭示海平面主体下降的经典型或欧美型。作者强调,全球二叠纪海侵型全球海平面旋回曲线应以西南地区为代表。

Abstract:

The Permian strata in southwestern China may be divided into two second-order sequences and eleven third-order sequences representing eleven third-order cycles of sea-level changes, of which six cycles, i. e. early Leonardian, early Guadalupian, late Guadalupian, early Kazanian,early Tatarian and late Tatarian sea-level cycles may be correlated with those in Euramerica. The results of research in this paper show that the Permian relative sea-level changes in the study area are dominantly controlled by global sea-level changes and synsedimentary tectonism, and reverse to those in Euamerica,even in Pangea, where the sea-level changes are characterized by the sea-level rises representing the transgressive sedimentary carbonate sequences. Two types or branches may be recognized for the Permian part of the Phanerozoic sea-level curves:one is the so-called Tethys type or South China type characterized by the sea-level rises representing transgressive sedimentary carbonate sequences;another is so-called classic type or Euramerica type characterized by the sea-level falls representing transitional-regressive sedimentary carbonate sequences. The authors contend that the Permian transgressive global sea-level curves should be represented by those for South China.