碎屑岩-碳酸盐岩巨旋回及其形成机理

CLASTIC ROCK-CARBONATE ROCK MEGACYCLES AND THEIR GENETIC MECHANISM

摘要:

全球整个地史时期,特别是震旦纪以来沉积的沉积岩序列,不论是稳定地区,还是活动地区,几乎都是由大小不等的碎屑岩-碳酸盐岩旋回组成。碎屑岩-碳酸盐岩巨旋回主要受地外因素控制。较小的碎屑岩-碳酸盐岩旋回则主要受地球本身因素控制。稳定地区浅水沉积的碎屑岩-碳酸盐岩巨旋回主要受地外因素控制。活动地区或深水地区沉积的碎屑岩-碳酸盐岩巨旋回除受地外因素控制外,还与构造活动等地球本身因素有关。本文着重讨论碎屑岩-碳酸盐岩巨旋回是如何受地外因素控制的,希图能抛砖引玉。由于笔者水平和掌握的资料有限,谬误之处难免,敬希读者批评指正。

Abstract:

Almost all the vertical sequences of sedimentary rocks are composed of clastic rock-carbonate rock cycles of varying sizes. An individual clastic rock-carbonate rock megacycle (first-order cycle) tends to be assembled by the lower clastic rock associations and upper carbonate rock associations. The large-scale unconformity interfaces are always found at the top and bottom of these cycles. A typical elastic rock-carbonate rock cycle covers three stages for its formation: weathering and denudation or terrestrial clastic deposition, marine clastic deposition and marine carbonate deposition. The formation of the clastic rock and carbonate rock associations is interpreted to be controlled mainly by transgression and regression which, in turn, are affected by expansion and shrinkage of the earth and cold and temperate climates which, in turn, are also related to the variations in gravitational constant when the solar system moves around the centre of the Galaxy. Thus the superposition of the elastic rock and carbonate rock associations may be responsible for the formation of the clastic rock-carbonate rock megacycles as a consequence of the periodic changes in gravitational constant with time.