中国南方三叠纪层序地层及海平面变化

SEQUENCE STRATIGRAPHY AND SEA LEVEL CHANGES IN SOUTHERN CHINA DURING THE TRIASSIC

摘要:

随着地震地层学的不断发展,层序地层学脱胎而出,成为当今沉积学界研究沉积层序、沉积体系域和海平面变化的有力途径。这一工作在国外研究已达到相当的水平,提交了一系列优秀的成果。近年来,由于有关层序地层学的理论和方法不断传入我国,从而也开始了这方面的研究工作。我们运用层序地层学的理论和方法,对中国南方三叠系进行了沉积层序、沉积体系域及与海平面变化关系的初步研究,获得了一些尚未十分成熟的成果。草写此文,以期能引起同行们的兴趣和共同探讨层序地层学这一新兴学科。

Abstract:

The Triassic strata and sedimentary facies are of widespread occurrence in southern China. The stratigraphic division and correlation are accurate as a result of the detailed sedimentological studies of the Triassic strata by the previous workers. The emphasis in this paper will be on sequence stratigraphy and sea level changes in southern China during the Triassic. Two types of sequence boundaries have been distinguished for the Triassic strata:Type Ⅰ sequence boundary including Indian-Olenekian, Oienekian-Anisian, Anisian-Ladinian and early Ladinian-late Ladinian, and Type Ⅱ sequence boundary including Permian-Indian on the basis of which two types of the depositional sequences have been correspondingly recognized for the Triassic strata in southern China. The Indian is involved in Type Ⅱ depositional sequence composed of shelf margin systems tract, transgressive systems tract and highstand systems tract. In the Olenekian, there are three depositional sequences (belonging to Type Ⅰ depositional sequence), i. e. T₁f⁴-T₁j², T₁j²-T₁j⁴ and T₁j⁴-T₁j⁵, composed of lowstand systems tract, transgressive systems tract and highstand systems tract, whereas in the Anisian-Ladinian, there are two depositional sequences, i. e. T₁j⁵-T₂l² and T₂l²-T₂l⁴, composed of lowstand systems tract, transgressive systems tract and highstand systems tract. According to the relationship between the systems tracts cited above and sea level changes, the curves showing the sea level changes in southern China during the Indian-Ladinian (Triassic) are also established by the authors in the present paper.