Extensive carbonate cementation of fluvial sandstones: an integrated outcrop and petrographic analysis from the Upper Cretaceous, Book Cliffs, Utah
Extensive carbonate cementation of fluvial sandstones: an integrated outcrop and petrographic analysis from the Upper Cretaceous, Book Cliffs, Utah
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DOI：
10.1016/j.marpetgeo.2011.06.003
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发表时间：
2011-08
影响因子：
4.2
通讯作者：
K. Taylor;Philip G. Machent
中科院分区：
文献类型：
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作者：
K. Taylor;Philip G. Machent
尽管河流相地层通常是重要的碳氢化合物储集层和地下水含水层，但河流相地层中以胶结体形式存在的广泛、大规模的胶结作用很少被记录在案。在这里，我们提供了犹他州Book Cliff上白垩统沙漠段和城堡砂岩河流地层中普遍存在的250米大小的铁质白云岩水泥体的露头、岩石学和地球化学数据。这些胶结体赋存于沙漠和城堡低位砂岩中的沿海平原河流地层中，并在较薄的远端河流相地层中最为丰富。在上倾角、较厚的河流相地层中几乎完全没有水泥体。岩石学观察表明，温和铁质白云岩的成岩作用主要是早期，并有较晚埋藏的成分。胶结物的δ13C值(+4.8~+−5.7‰V-PDB)表明，最早的相为海相来源，后期胶结物为埋藏有机质来源。δ18O数据(−6.3至−11.8‰V-PDB)表明，降水来自以淡水为主的流体。认为白云岩是由低水位煤下的碎屑白云岩淋滤而成，由于基准面的起伏，沿海含水层经历了大气-海洋混合流体的胶结作用。这里提供的数据表明，大型水泥体可能是河流相砂岩中的一个重要组成部分，对储集层质量和储集层内的流体流动都有潜在的重大影响，特别是在海-海界面。
Extensive, large-scale pervasive cementation in the form of cement bodies within fluvial strata has rarely been documented although fluvial strata commonly act as important hydrocarbon reservoirs, as well as groundwater aquifers. Here, we present outcrop, petrographic and geochemical data for pervasive ferroan dolomite cement bodies up to 250 m in size from Upper Cretaceous Desert Member and Castlegate Sandstone fluvial strata exposed in the Book Cliffs in Utah. These cement bodies are present with coastal plain fluvial strata within both the Desert and Castlegate lowstand sandstones and are most abundant in the thin, distal fluvial strata. Cement bodies are almost entirely absent in updip, thicker, fluvial strata. Petrographic observations suggest a predominantly early diagenetic timing to the mildly ferroan dolomite, with a component of later burial origin. δ13C values for the cement (+4.8 to −5.7‰ V-PDB) suggest a marine-derived source for the earliest phase with a burial organic matter source for later cement. δ18O data (−6.3 to −11.8‰ V-PDB) suggest precipitation from freshwater dominated fluids. It is proposed here that dolomite was derived from leaching of detrital dolomite under lowstand coals and cementation took place in coastal aquifers experiencing mixed meteoric-marine fluids as a result of base-level fluctuations. This data presented here shows that large cement bodies can be an important component within fluvial sandstones with a potentially significant impact upon both reservoir quality and fluid flow within reservoirs, especially at the marine-non-marine interface.