杨山晚古生代沉积盆地成因类型及其与桐柏-大别造山带关系的探讨

杨山晚古生代沉积盆地位于桐柏-大别山北麓,它具有明显的前陆盆地沉积特点,由早期(D₂?—C₁)的复理石建造到晚期(C₁—P?)的磨拉石建造;古生物地理分析表明其与华北、扬子陆块都有密不可分的联系,其间不可能有古洋盆的存在,因而它应当是桐柏一大别造山带碰撞造山过程中形成的前陆盆地。杨山晚古生代前陆盆地的形成说明,扬子陆块和华北陆块的陆-陆碰撞起始于晚泥盆世之前(S₃—D₂),而桐柏-大别造山带中生代的构造事件则可能代表一次大规模陆内逆冲-推覆作用。

THE GENETIC TYPE OF YANGSHAN UPPER PALEOZOIC BASIN AND ITS RELATION TO THE TONGBAI-DABIE OROGENIC BELT

The Upper Paleozoic Yangshan basin, geographically located at the northern foot of Tongbai-Dabie mountains, is a typical peripheral foreland basin of Tongbai-Dabie orogenic belt. The Xinyang-Shucheng zone, which is the eastern part of the main suture zone between Yangtze and North China plates, is located north to Yangshan foreland basin. Yangshan Upper Paleozoic sedimentary basin is a foreland basin formed accompanying the collision between Yangtze and North China plates. This resulted in the dose resemblance of the Upper Paleozoic bio-assemblages in Yangshan foreland basin to those in Yangtze and North China plates, and the sedimentary derivation from both Yangtze and North China plates. Its sedimentary sequence consists of the early (D-C₁) flysh formation and the late (C-P) molasse formation. This is one of the typical sedimentary characteristics of foreland basin. From the biostratigraphic study and regional geological data, North China and Yangtze were one continent during Upper Paleozoic. There was no oceanic basin between them. The identification of Yangshan Upper Paleozoic foreland basin indicates the S₃-D₂ continent-continent collision between Yangtze and North China plates. This type of peripheral foreland basin is called "proto-foreland basin" in this paper. And the Mesozoic foreland basin south to Tongbai-Dabie mountains was formed during the large scale intracontinental subduction between Yangtze plate and Tongbai-Dabie block. During this intracontinental subduction, Tongbai- Dabie block which is a part of the northern passive margin of Yangtze plate was detached from and overthrusted onto Yangtze plate. This type of peripheral foreland basin is called "outer foreland basin" here. "Proto-foreland basin" and "outer foreland basin" form the "bi-foreland basin" of one collision orogenic belt. The "bi-foreland basin" model is also possiby developed in Himalayan and Uralian orogenic belts, etc. It is significant for the study on collision orogenic belt.