沉积层序及海平面旋回的分类级别———旋回周期的成因讨论

摘　要　沉积层序可区分为巨层序、大层序、中层序、正层序、亚层序和小层序6 个级别的 单位, 其时间延续大致分别为500 ～ 600 Ma , 60 ～ 120 Ma, 30 ～ 40 Ma , 2 ～ 5 Ma , 0.1 ～ 0.4 Ma 和0.02～ 0.04 Ma 。沉积层序虽不同程度地受区域性构造运动和其他因素的影响, 但 具有明显的全球性和周期性。除大层序可能是由克拉通规模的热旋回引起的海平面相对变化 所造成的外, 其他级别的层序可能主要由全球海平面变化旋回所控制, 并与天文周期有关。 地球做为银河系和太阳系的一个行星, 其地质演化不可避免地受到其他星系及其内部星体运 行规律的影响, 沉积层序可能是地球水圈响应于天体运动周期的沉积记录。

HIERARCHY OF DEPOSITIONAL SEQUENCES AND EUSTATIC CYCLES A DISCUSSION ON THE MECHANISM OF SEDIMENTARY CYCLES

Depositional sequences may be distinguished into six ranks of units as giga ,mega ,meso ,ortho ,sub and micro sequence, and are interpreted to be formed during the eustatic cycles with time intervals of 500～600Ma, 60～120Ma,30～40Ma,2～5Ma,0 1～0 4Ma and 0 02～0 04Ma respectively. All of them are thought to be essentially related to astronomical cycles, except the megasequence which may be caused by the long term geothermal cycles on cratons. We deem that the depositional sequences, though often influenced variably by local tectonics and other factors, are primarily global and periodic in nature. We also hold that, as one of the planets within the Galaxy, the earth must have been affected in various ways by other asteroids, and that the depositional sequences are merely the responses of the hydrosphere to the astronomical cycles in sedimentation.