Although carbonate ramps are widely described from the geological record, there is still a debate on the relative influence of water temperature, trophic conditions and type of carbonate factories on their development. The ca 2400 km long Australian North West Shelf is among the largest Cenozoic carbonate provinces worldwide, and records a transition from an early Miocene ramp to a middle Miocene rimmed platform. This change is observable on publicly available seismic data, giving the opportunity to investigate environmental influences on platform evolution. This study combines macroscopic and petrographic descriptions of early Miocene strata cropping out in the Cape Range Anticline (North West Cape, southern end of the North West Shelf) and of time-equivalent well cuttings from the adjacent, offshore Exmouth Sub-basin. Particular emphasis is placed on the identification of larger benthic foraminifera at a broad generic level, because differing taxa have a limited range of habitable conditions that serve as environmental proxies. The results show that early Miocene strata are dominantly composed of larger benthic foraminifera with minor coralline algae in the proximal platform, grading to micropackstones in the more distal platform. A ramp margin is inferred from the lithological data on the basis of the lack of framework builders and the presence of open oceanic indicators. Facies shallow upward through individual outcrops, with a proximal to distal trend towards the north-west. These trends along outcrops are consistent with the seismic interpretations. Identification of taxa with warm, oligotrophic water affinity suggests that the ramp was formed in an oligotrophic and warm ocean, despite the absence of coral reefs. Changes of carbonate facies with depth do not seem to be associated with changes in ramp morphology, and the latter may have been controlled by physical oceanic parameters, such as offshore currents and waves.

中文翻译：

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澳大利亚西北大陆架温暖海洋中早中新世碳酸盐岩斜坡发育

尽管地质记录中广泛描述了碳酸盐斜坡，但关于水温、营养条件和碳酸盐工厂类型对其发展的相对影响仍存在争议。该CA2400 公里长的澳大利亚西北大陆架是世界上最大的新生代碳酸盐岩省份之一，记录了从中新世早期斜坡到中中新世边缘地台的过渡。这种变化可以在公开可用的地震数据上观察到，从而有机会研究环境对平台演变的影响。本研究结合了开普山脉背斜（西北开普，西北大陆架南端）中出露的早中新世地层的宏观和岩相学描述，以及来自相邻的离岸埃克斯茅斯子盆地的时间等效井切屑。特别强调在广泛的一般水平上识别较大的底栖有孔虫，因为不同的分类群具有有限范围的可作为环境代理的宜居条件。结果表明，早中新世地层主要由较大的底栖有孔虫组成，近端平台有少量珊瑚藻，较远端平台分级为微堆积石。根据缺乏框架构建器和存在开放海洋指标，从岩性数据中推断出斜坡边缘。相通过个别露头向上浅，具有向西北向近端到远端的趋势。这些沿露头的趋势与地震解释一致。具有温暖、贫营养水亲和力的分类群的鉴定表明，尽管没有珊瑚礁，但斜坡是在贫营养和温暖的海洋中形成的。碳酸盐岩相随深度的变化似乎与斜坡形态的变化无关，