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首页> 外文期刊>Stratigraphy >Foraminiferal biostratigraphy and paleoenvironments of the Oligocene-Miocene carbonate succession in Campos Basin, southeastern Brazil
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Foraminiferal biostratigraphy and paleoenvironments of the Oligocene-Miocene carbonate succession in Campos Basin, southeastern Brazil

机译：巴西东南部坎波斯盆地渐新世-中新世碳酸盐岩演替的有孔虫生物地层学和古环境

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摘要

The present investigation of the Cenozoic carbonate succession of the Campos Basin, offshore southeastern Brazil, has resulted in a high resolution biostratigraphic profile of the region based on cores and cutting samples. In general, the studied carbonate successions evolved during three depositional stages: 1) In the Oligocene a warm period prevailed where temperature-sensitive organisms, such as larger benthic foraminifera, corals, algae and arthropods thrived in a reefal setting. Four different benthic foraminiferal biozones (BF1 - BF4) were defined based upon the occurrence of the following foraminiferal assemblages which were dominated by (BF1) lepidocyclinids, (BF2) miogypsinids, (BF3) Miogypsina-Amphistegina, and (BF4) Miogypsina and Heterostegina. These biozones, are equivalent to the P18-P22 planktonic foraminiferal biozones, and reflect temporal changes of environmental and ecological conditions associated with minor sea level fluctuation. 2) The warm period continued through the early Miocene, where corals, bryozoans, rare planktonic foraminifera and larger benthic foraminifera thrived in clear agitated waters of a forereefal setting. This period was represented by two benthic foraminiferal zones, BF5 - BF6, equivalent to the N4-N7 planktonic foraminiferal biozones. Miogypsinids, Lepidocyclina and Heterostegina dominate BF5, while attached forms growing in a massive branching structure, such as Sporadotrema are prominent in BF6. 3) The third depositional stage is reflected by a rapid deepening of the carbonate facies at the onset of the middle Miocene, coeval with a global warming event, the so-called mid-Miocene Climatic Maximum. This resulted in the replacement of the reefal organisms by pelagic sediments containing planktonic foraminifera. The planktonic foraminiferal biozones PF1 and PF2 are equivalent to N8-N12 planktonic foraminiferal biozones, and were present in all wells. This rapid sea level change is inferred to be related to a global warming event and related oceanographic changes. The high resolution depositional and biostratigraphic scheme put forward here for the Campos Basin will enable a more detailed understanding of the general regional evolution of the economically important Cenozoic carbonate facies that are found off the Atlantic margins of South America, the Caribbean and West Africa.
机译：目前对巴西东南部沿海地区坎波斯盆地新生代碳酸盐岩层序的研究，根据岩芯和切屑样品得出了该地区的高分辨率生物地层剖面。一般而言，所研究的碳酸盐演替是在三个沉积阶段演化的：1）渐新世处于温暖时期，温度敏感生物（例如较大的底栖有孔虫，珊瑚，藻类和节肢动物）在暗礁环境中繁衍生息。根据以下有孔虫组合的发生情况，定义了四个不同的底栖有孔虫生物区（BF1-BF4），这些组合主要由（BF1）鳞状细胞环素，（BF2）og虫，（BF3）Mi虫-斜纹虫和（BF4）og虫和Heteryterina组成。这些生物区等同于P18-P22浮游有孔虫生物区，反映了与微小海平面波动有关的环境和生态条件的时空变化。 2）暖期一直持续到中新世早期，珊瑚，苔藓虫，稀有浮游有孔虫和较大的底栖有孔虫在前足环境的清澈搅动的水中繁盛。这个时期由两个底栖有孔虫带BF5-BF6代表，相当于N4-N7浮游有孔虫生物带。 BF5占主导地位的是Miogypsinids，Lepidocyclina和Heterostegina，而在BF6中则突出了以大量分支结构生长的附着形式，例如孢子囊。 3）第三个沉积阶段是中新世中期碳酸盐相迅速加深反映的，这与全球变暖事件（所谓的中新世中期气候最大值）同时出现。这导致珊瑚礁生物被含有浮游有孔虫的浮游沉积物所取代。浮游有孔虫生物区PF1和PF2相当于N8-N12浮游有孔虫生物区，并存在于所有孔中。据推测，这种快速的海平面变化与全球变暖事件和相关的海洋学变化有关。这里为坎波斯盆地提出的高分辨率沉积和生物地层学方案将使人们更加详细地了解在南美，加勒比海和西非的大西洋边缘发现的具有经济意义的新生代碳酸盐岩相的总体区域演化。

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