Clast Fabric of Till and its Development
Clast Fabric of Till and its Development
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Till碎屑织物及其开发
DOI：
10.1306/74d71ff0-2b21-11d7-8648000102c1865d
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发表时间：
1970
期刊：
影响因子：
--
通讯作者：
J. Lindsay
中科院分区：
文献类型：
--
作者：
J. Lindsay
摘要南极二叠纪宝塔组碎屑岩中的长轴碎屑组构根据组构模式的强度和取向，可分为几种形态类型。这些组构是大量过程的结果，这些过程既发生在冰川上，因为碎屑在活跃变形的冰中被输送，也发生在沉积时的冰-沉积物界面上。宝塔组的一些碎屑组构可能是在海盆中发育的，在沉积过程中有类似数量的碎屑组构完全重组。然而，最大比例的图表在性质上介于英吉利形成的织物和沉积过程中形成的织物之间。这表明，在大多数耕作单位的沉积过程中，冰下条件使得冰面组构一般只有部分重组。碎屑组构在冰下重组的程度在很大程度上取决于沉积时冰-沉积物界面的剪应力分布，而剪应力又取决于底部的粗糙度和沉积速率。因此，碎屑组构不仅提供了古冰流方向的信息，而且对确定冰层沉积过程中冰-沉积物界面的普遍条件也很有价值。
ABSTRACT Long-axis clast fabrics from tillites of the Permian Pagoda Formation in Antarctica can be classified into several morphologic types depending on the strength and orientation of the fabric modes. The fabrics result from a large number of processes which take place both englacially, as the clast is being transported in actively deforming ice, and subglacially at the ice-sediment interface at the time of deposition. A few of the clast fabrics from the Pagoda Formation probably developed englacially and a like number were completely reorganized during deposition. However, the largest proportion of the diagrams are intermediate in character between those of fabrics formed englacially and those formed during deposition. This suggests that the subglacial conditions are such during depositio of most till units that the englacial fabrics are generally only partially reorganized. The degree to which subglacial reorganization of the clast fabric takes place depends in large part on the distribution of shear stress at the ice-sediment interface at the time of deposition which in turn depends on bottom roughness and the rate of deposition. Thus clast fabric not only provides information on paleo-ice flow direction but is also valuable in determining the conditions prevailing at the ice-sediment interface during till deposition.