Abstract

The Vema Fracture Zone orthogonally intersecting the Mid-Atlantic Ridge along 11° N is a complex tectono-sedimentary system, through which bottom water is transferred from the western to the eastern Atlantic. The southern surrounding of the fault valley is an extended (about 320 km) transverse ridge. At the early stages of the Vema System evolution, the ridge was located at shallow depths in the photosynthesis zone, which led to the formation of extensive biogenic carbonate buildups on its surface. Spreading, general sinking of the system, and associated movements along faults caused disintegration of ultramafic basement and bioherms with subsequent fractionation of colluvial–pelagic sediments and their eastward transport by bottom currents. The formation of coarse-grained residual sands completely devoid of pelitic material is associated with the high flow rates of Antarctic bottom waters. The presence of rounded pebbles of organogenic limestones and ultramafic rocks with traces of bioproductivity indicates that clastic material was transferred over a few hundred kilometers.

中文翻译：

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中大西洋维玛断裂带的残留沉积物

摘要

沿着11°N与大西洋中脊垂直相交的Vema断裂带是一个复杂的构造-沉积体系，底水通过该系统从西部大西洋转移到东部大西洋。断层谷的南部周围是一个延伸的（约320 km）横向山脊。在Vema系统演化的早期，山脊位于光合作用区的浅层深度，这导致了其表面上大量生物碳酸盐堆积的形成。系统的扩散，总体下沉以及沿断层的相关运动引起超镁铁质基底和生物层的崩解，进而使冲积-上层沉积物分离，并由海流向东输送。完全没有胶粉质物质的粗粒残留砂的形成与南极底水的高流速有关。具生物生产力痕迹的有机成因石灰岩和超镁铁质岩石的圆卵石的存在表明碎屑物质已转移了数百公里。