中国南方二叠纪海平面变化及升降事件

在对中国南方二叠纪层序地层、充填特征及沉积演化认识基础上,通过研究海平面升降变化及事件后认为:华南二叠纪相对海平面升降旋回与其层序数量一致,升降型式可有两种且互成影像;二级海平面升降包括“二分式”和“单分式”,前者以扬子区为代表,后者典型见于华夏区;海平面升降事件发生在栖霞早期、茅口早期、茅口末期、吴家坪早期及长兴中后期;二级、三级海平面变化在升降样式、数量、相位上与欧美各地有所不同,其成因与所处构造域有关。

Permian Sea-level Changes and Rising-Falling Events in South China

On the basis of sequence stratigraphy,fills and evolution of sedimentary basin,a primary research on the Permian sea level and eustatic changes,rise and fall events in South China have been studied in this paper. Eleven cycles of relative sea level rising falling,which is equal to the depositional sequences,are recognized in Permian in South China.Of them,two patterns of the relative sea level rising falling are distinguished out.The first is a change tendency of continuously slower rising→faster falling that is dominated in the Yangtze Craton,and the second is vice versa that is common in most parts of Cathayan Craton,especially in eastern shallow Cathayan Craton.The two patterns of relative sea level rising falling are just in symmetric tendency. Also the changing patterns of the second order eustasy are divided into “One and half" type and “Single" type through the Permian which are the representatives of Yangtze Craton and Cathayan Craton respectively.Here,the “One and half"type means that there are on complete second order cycle and less than half cycle in Permian in Yangtze Craton and western margin of the Cathayan Craton.And the “Single"type shows that there is just one complete rising falling cycle in the same period in the eastern shallow Cathayan Craton. There are five events of sea level rising and falling,i.e.,the rising event in early Qixia stage,the highest sea level stand event at the earliest Maokou stage,the lowest sea level stand event at the terminal Maokou stage,the rising event in primary Wujiaping stage,and the falling event at middle Changxing stage separately.It is proposed that most of the sea level rising and falling events are relevant to the regional tectonics superposed by the second eustasy. The patterns of sea level and eustatic changes are distinctly different from those in Euramerica.The time of the highest eustatic stand is aged as the earliest Maolou Stage,which approximately equals to the early Artinskian in Europe,to the early Leonardian in North America.But it is showed in the late Maolou Stage on the Vail Curve in 1977,and in the terminal Carboniferous in the Gondwana Land in the T R cycles by Ross and Ross in 1985.The lowest eustatic stand in the Yangtze Craton lies in the terminal Early Permian (latest Maokou Stage),but displays in earliest Permian on the Vil Curve (1977),and in latest Permian in the T R cycles by Ross and Ross in 1985.The total tendency of eustatic change in the Cathayan Craton is similar to that on the Vail Curve although the highest eustatic stand of the former formed earlier than the later.It is supposed that the controls are probably different in variable tectonic settings becaus the Yangtze Craton and western Cathayan Craton belong to the Tethyan tectonic field,and the eastern Cathayan Craton,Euramerica to the Pacific tectonic field.