Stratigraphic Sedimentology of Tertiary Cool-Water Limestones, SE Australia
Stratigraphic Sedimentology of Tertiary Cool-Water Limestones, SE Australia
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澳大利亚东南部第三纪冷水石灰岩的地层沉积学
DOI：
10.1306/d4268202-2b26-11d7-8648000102c1865d
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发表时间：
1995
影响因子：
2
通讯作者：
N. James
中科院分区：
文献类型：
--
作者：
Thomas D. Boreen;N. James
澳大利亚东南部维多利亚海岸沿着海崖出露的中第三纪石灰岩，堆积在冷水、远端变陡斜坡或开阔陆棚的内部。所有沉积物均为生物群落，主要由苔藓虫、棘皮动物、底栖有孔虫、腕足动物和软体动物颗粒组成。浅的粒状相还含有珊瑚藻类、石英和白榴石，而深的泥质相包括造礁珊瑚、介形虫、海绵骨针、南极有孔虫和陆源粘土。基本的沉积单元是米级的潮下旋回或韵律。浅陆棚旋回是由海洋胶结硬地或石英颗粒滞后覆盖的向上变浅、交错层状或洞穴状颗粒灰岩，而中陆棚旋回是向上变粗和增厚的，靠近远端风暴岩。此类周期被解释为由海平面驱动、气候控制的磨蚀波底和膨胀波底振荡形成。深陆棚韵律是苔藓虫泥灰岩和钙质粘土的互层，被认为是由气候影响的碳酸盐生产力波动和陆源稀释作用产生的。低位体系域是沉积或侵蚀的。层序边界是复杂的、多世代的、主要是海底表面（凝聚旋回边界），可以在海上追踪到多个遗漏表面和整合接触面。盆地内的相转移导致堆积的、浅向上的颗粒灰岩旋回的浓缩低位楔的沉积。海进体系域是与相后退和突然加深相关的厚苔藓虫泥灰岩-钙质粘土韵律。这种韵律岩通常在地层上向上渐变为风暴岩旋回。高位体系域是一种高度水平的楔形岩体，具有浅向上的颗粒状旋回。这些石灰岩提供了现代冷水碳酸盐陆棚沉积物与更古老的中生代和古生代类似沉积物记录之间的地层学关键联系。
ABSTRACT Mid-Tertiary limestones, exposed as sea cliffs along the coast of Victoria, southeastern Australia, accumulated on the inner part of a cool-water, distally steepened ramp or open shelf. All sediments are bioclastic, dominated by particles of bryozoans, echinoderms, benthic foraminifers, brachiopods, and molluscs. Shallow, grainy facies also contain coralline algae, quartz, and glauconite, while deep, muddy facies include ahermatypic corals, ostracodes, sponge spicules, planktic foraminifers, and terrigenous clays. The fundamental depositional unit is a meter-scale, subtidal cycle or rhythm. Shallow-shelf cycles are shallowing-upward, cross-bedded or burrowed grainstone capped by a marine-cemented hardground or quartz-granule lag, while mid-shelf cycles are upward-coarsening and thickening, proximal to distal tempestites. Such cycles are interpreted to form by eustatically driven, climatically controlled oscillations in abrasion wave base and swell wave base. Deep shelf rhythms are interbedded bryozoan marl and calcareous clay, thought to be generated by climatically influenced fluctuations in carbonate productivity and terrigenous dilution. Lowstand systems tracts are depositional or erosional. Sequence boundaries are complex, multigeneration, mostly submarine surfaces (condensed cycle boundaries) that can be traced offshore into multiple omission surfaces and conformable contacts. Basinward facies shifts result in deposition of condensed lowstand wedges of stacked, shallowing-upward grainstone cycles. Transgressive systems tracts are thick bryozoan marl-calcareous clay rhythms associated with facies backstepping and abrupt deepening. Such rhythmites typically grade stratigraphically upward into tempestite cycles. Highstand systems tracts are highly progradational, wedge-shaped rock bodies of shallowing-upward grainy cycles. These limestones provide the critical link of stratigraphy between modern cool-water carbonate shelf deposits and the older Mesozoic and Paleozoic record of similar sediments.