15. GENESIS AND EVOLUTION OF SMALL-SCALE STRUCTURES IN THE TOE OF THE BARBADOS RIDGE ACCRETIONARY WEDGE1
15. GENESIS AND EVOLUTION OF SMALL-SCALE STRUCTURES IN THE TOE OF THE BARBADOS RIDGE ACCRETIONARY WEDGE1
复制标题
15. 巴巴多斯海岭增生楔趾部小规模结构的起源和演化1
DOI：
--
复制
发表时间：
1990
期刊：
影响因子：
--
通讯作者：
J. Behrmann
中科院分区：
文献类型：
--
作者：
K. Brown;J. Behrmann
Leg 110的岩心记录了在基底滑脱带向深海平面剖面的初始扩展和随后楔体增厚期间产生的小规模结构的发展。在宏观增生前缘，亚水平压应力主要集中在离刮剖面而非逆冲下沉积。相比之下，与基底滑脱带相关的地层可能经历由简单剪切和可能的压扁应变（后者可能是由于上覆楔变厚而增加的构造负荷的结果）共同造成的层平行伸展。随着位移的增加，与基底滑脱和其他逆冲有关的强烈鳞状织物带似乎变厚。这种增厚，加上越来越多的逆冲（包括序内逆冲和非序内逆冲），可能解释了为什么楔体的50%体积受到674点（距离吸积前缘18公里）的鳞状结构的影响。一般的顺层和逆冲倾角在楔体中增加，这很可能是对叠瓦状逆冲褶皱和逆旋转的反应。在距增生前缘18 km处发育强烈的地层破坏、同构造碳酸盐脉体、偶有等斜褶皱（含轴向平面织构）和网状构造。此时沉积物孔隙度仍在40%以上，目前在小于400mbsf的深度发现了小尺度结构。显然，这些熟悉的古代增生楔结构可以在增生后不久在多孔沉积物的浅层发育。
Cores from Leg 110 document the development of small-scale structures generated both during the initial propaga tion of the basal decollement zone into the abyssal plane section and the subsequent thickening of the wedge. At the macroscopic accretionary front, sub-horizontal compressive stresses become localized in the off-scraped section rather than in the underthrust sediments. In contrast, strata associated with the basal decollement zone may experience layer parallel extension resulting from a combination of simple shear and possible flattening strains (with the latter being the possible consequence of increased tectonic loading due to the thickening of the overlying wedge). The zone of intense scaly fabrics associated with the basal decollement and other thrusts appears to thicken with increasing displacement. This thickening, together with increasing numbers of thrusts (of both an in-sequence and out-of-sequence nature), may account for why 50% of the volume of the wedge is affected by scaly fabrics of Site 674, 18 km back from the accretion ary front. General bedding and thrust dips increase back in the wedge, most probably in response to both folding and back rotation of imbricate thrusts. Intense stratal disruption, Syntectonic carbonate veins, occasional isoclinal folds (with axial planar fabrics), and web structures are all developed by 18 km from the accretionary front. At this point, the sediments still have porosities in excess of 40%, and the small-scale structures are found at present depths of less than 400 mbsf. Apparently, these familiar fabrics of ancient accretionary wedges can develop at shallow depths in porous sediments soon after accretion.