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首页> 外文期刊>Journal of Asian earth sciences >Lifestyles of the palaeoproterozoic stromatolite builders in the Vempalle Sea, Cuddapah Basin, India
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Lifestyles of the palaeoproterozoic stromatolite builders in the Vempalle Sea, Cuddapah Basin, India

机译：印度库达帕盆地范帕尔海古元古代叠层石建造者的生活方式

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摘要

The distribution and changing pattern of stromatolites in the Vempalle Formation of the Cuddapah Basin, India, have been investigated with emphasis on external morphologies, internal fabrics, growth patterns and sediment associations. The stromatolitic limestone occurs in a low angle ramp type carbonate platform, with complete exposures from shallow shelf to basinal fades, provides record of changes in reef-building capacity of stromatolites with change in the depositional milieu. Changing pattern and style of the stromatolites clearly reflect depth partitioned growth of the microbial community. Small and scattered stromatolites, commonly with wavy parallel laminations or stratifications occurred in inner-ramp settings, where they are build up to the sea level. Tepee structure and desiccation cracks in associated sediments and salt pseudomorphs point to shallow water to occasional exposure condition. Large bioherms with columnar and conical stromatolites developed in the headland (mid ramp), which were in continuous interaction with strong waves of the open sea. Growth of the bioherms changed the landform with time and generated a high sloping edge with a sheer drop that extended out into the sea, forming distally steepened ramp. Outer ramp lithofacies characterized by thick layers of shale succession with thin beds of laterally persistent stromatolitic beds with low synoptic relief build-ups. These biotic components, along with the absence of wave-related structures, place the outer ramp below the base of wave action zone. Ooid banks developed in the mid ramp area are in the high surfing zone. High flux of nutrients and high-light show positive correlation; thus the high growth pattern is best observed within the photic zone where wave action is maximum. The ability to change from low synoptic relief algal laminites to high synoptic relief columnar stromatolites point to their adaptive power. The key factor that controlled the shape of these Palaeoproterozoic stromatolites is the dynamic interactions between mat growth, currents and sediment supply. Presence of concentric and radial fibrous ooids indicates change in climate and salinity of the sea.
机译：研究了印度Cuddapah盆地Vempalle组的叠层石的分布和变化模式，重点是外部形态，内部构造，生长模式和沉积物缔合。层间质石灰岩发生在低角度斜坡型碳酸盐台地中，从浅层陆架到盆地性衰落完全暴露，提供了层状沸石礁沉积能力随沉积环境变化的变化记录。叠层石的样式和样式的变化清楚地反映了微生物群落的深度分区增长。小型且散布的叠层石通常在内部斜坡环境中形成波浪状平行叠片或分层，并在海平面上升。相关沉积物和盐假晶的圆锥形结构和干燥裂缝指向浅水区，偶有暴露条件。在陆岬（坡道中部）形成了带有柱状和圆锥形叠层石的大型生物礁，它们与公海的强波浪持续相互作用。生物群落的生长随时间改变了地形，并产生了一个高坡度的边缘，陡峭的下降延伸到海中，形成了向远端倾斜的斜坡。外斜坡岩相以页岩层厚层为特征，侧向持久的层积岩层薄层，低层地形起伏。这些生物成分以及不存在与波浪相关的结构，将外部坡道置于波浪作用区底部以下。在坡道中部地区发育的卵石带处于高冲浪区。营养物质的高通量和强光显示出正相关；因此，在波作用最大的光区内最好观察到高生长模式。从低天气浮雕藻类薄片岩转变为高天气浮雕柱状叠层石的能力表明了它们的适应能力。控制这些古元古代叠层石形状的关键因素是垫层生长，洋流和沉积物供应之间的动态相互作用。同心的和放射状的纤维质的存在表明气候和海洋盐度的变化。

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