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Development of coral–sponge–microbialite reefs in a coated grain-dominated carbonate ramp (Upper Jurassic, eastern Sardinia, Italy)
Facies ( IF 1.8 ) Pub Date : 2020-12-24 , DOI: 10.1007/s10347-020-00616-7
Mattia Nembrini , Giovanna Della Porta , Fabrizio Berra

The Late Jurassic is a peak time of diversification of reefs with corals, stromatoporoids, calcareous and siliceous sponges, and microbialites during the Phanerozoic. This study focuses on the Callovian–Kimmeridgian carbonate succession of eastern Sardinia, deposited at tropical latitudes on the European passive margin that recorded from the late Oxfordian the evolution from a coated grain-dominated to a reef-bearing carbonate ramp. The coated grain-dominated carbonate ramp (phase 1; Callovian–middle Oxfordian) includes inner ramp ooidal shoals and peloidal packstone in the middle-to-outer ramp. The overlying reef-bearing ramp (phase 2; late Oxfordian–late Kimmeridgian) is characterized by three types (1–3) of bioconstructions. The distribution of these build-ups along the middle-to-outer ramp depositional profile reflects bathymetric parameters, related to the interplay of water energy and light penetration. Type 1 build-ups developed in the proximal middle ramp and consist of 45 m thick, 100 m wide, coral-stromatoporoid boundstone associated with coral–stromatoporoid rudstone–grainstone. Type 2 build-ups, colonizing deeper environments in the middle ramp, are lens-shaped coral–calcareous sponge–diceratid boundstone including stromatoporoids and chaetetid sponges, 1–2 m thick and 3–4 m wide, associated with bioclastic packstone–grainstone. Type 3 lens-shaped calcareous and siliceous sponge–coral–microbialite boundstone build-ups (1 m thick and a few metres wide) formed in lower energy, distal middle-to-outer ramp settings. The evolution of the eastern Sardinian carbonate ramp reflects the Oxfordian–Kimmeridgian spread of the coral–sponge-microbialite reefs along the Tethyan European passive margin.

中文翻译:

在以涂层颗粒为主的碳酸盐斜坡(上侏罗纪,东撒丁岛,意大利)中珊瑚-海绵-微生物岩礁的发育

晚侏罗世是显生宙期间珊瑚礁、层孔虫、钙质和硅质海绵以及微生物岩多样化的高峰时期。这项研究的重点是撒丁岛东部卡洛夫阶 - 基默里阶碳酸盐岩系列,沉积在欧洲被动边缘的热带纬度上,记录了从牛津阶晚期开始,从以涂层颗粒为主的碳酸盐岩斜坡演变为含礁的碳酸盐斜坡。以涂层颗粒为主的碳酸盐岩斜坡(第 1 阶段;卡洛夫-中牛津阶)包括内斜坡卵形浅滩和中外斜坡中的球状颗粒灰岩。上覆的含礁斜坡(第 2 阶段;晚牛津阶 - 晚 Kimmeridgian)以三种类型(1-3)的生物构造为特征。这些堆积物沿中到外斜坡沉积剖面的分布反映了测深参数,与水能和光穿透的相互作用有关。1 型堆积物在近端中间斜坡发育,由 45 m 厚、100 m 宽的珊瑚-层孔状边界岩与珊瑚-层孔状砂岩-粒状岩相关。类型 2 堆积物,在中间斜坡的更深环境中定居,是透镜状珊瑚 - 钙质海绵 - 双角节动物界石,包括层孔体和毛虫海绵,1-2 m 厚,3-4 m 宽,与生物碎屑颗粒石 - 颗粒石有关。3 型透镜状钙质和硅质海绵-珊瑚-微生物岩边界岩堆积物(1 m 厚,几米宽)形成于较低能量的远端中外斜坡设置。
更新日期:2020-12-24
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