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首页> 外文期刊>Facies >Environmental significance of gypsum-bearing layers at the ‘‘Lo Hueco'' paleontological site (Upper Cretaceous, Cuenca, Spain): petrography, fluid inclusions, and isotopic relations
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Environmental significance of gypsum-bearing layers at the ‘‘Lo Hueco'' paleontological site (Upper Cretaceous, Cuenca, Spain): petrography, fluid inclusions, and isotopic relations

机译：“ Lo Hueco”古生物学遗址（白垩纪上部，昆卡，西班牙）上含石膏层的环境意义：岩相学，流体包裹体和同位素关系

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‘‘Lo Hueco'' (Cuenca, Spain) is an upper Campanian–lower Maastrichtian Fossil-Lagerst?tte that has provided more than 8,500 well-preserved macrofossils, including titanosaur sauropod dinosaurs. Although the facies and fossil record point to both fresh and brackish or marine water influences, a detailed study of the sulphatebearing layers of the site through petrography, fluid inclusions, and isotopes has been undertaken to evaluate the possible marine influence. The two main sulphate units of the ‘‘Lo Hueco'' site consist chiefly of bimodal micro- to meso- lenticular gypsum crystals that grew displacively in a clayey-carbonate sediment. The well-preserved lenticular gypsum crystals are primary, as demonstrated by the presence of the original twinning and the absence of hydration textures or anhydrite relicts. Primary fluid inclusions of the lenticular gypsum crystals indicate a vadose environment of formation, with salinities between 1,800 and 14,000 ppm, pointing to a brackish but non-marine environment. Furthermore, gypsum exhibits ~(87)Sr/~(86)Sr values between 0.708034 and 0.708120, which are higher than those from marine evaporites of Campanian–Maastrichtian age, indicating a clear influence of fresh water. Gypsum δ~(34)S VCDT values (18.1 to 19.0 ± 0.5 ‰) and δ~(18)OVSMOW values (11.0 to 15.2 ± 0.5 ‰), on the other hand, are typical isotopic values recorded in marine evaporites of this age. This apparent contradiction between fluid inclusion and Sr isotopic data is probably the result of some recycling from Upper Cretaceous evaporites. Based on all these observations, the sulphate-bearing layers are interpreted as probably formed in a near-coastal saline mudflat of a playa lake. As a whole, this study highlights the importance of combining different proxies when dealing with evaporites formed in brackish-water environments.
机译：“ Lo Hueco”（西班牙昆卡）是上坎帕尼阶-马斯特里赫特-化石-拉格斯特下部的化石，已经提供了8,500多个保存完好的大型化石，包括泰坦龙，蜥脚类恐龙。尽管相和化石记录都表明淡水，微咸水或海水的影响，但已经通过岩相学，流体包裹体和同位素对现场硫酸盐层进行了详细研究，以评估可能的海洋影响。 “ Lo Hueco”矿场的两个主要硫酸盐单元主要由双峰微晶至中晶双晶石膏晶体组成，它们在粘土碳酸盐沉积物中位移生长。保存完好的柱状石膏晶体是主要的，如原始孪晶的存在以及水合质地或硬石膏残渣的存在所证明。柱状石膏晶体的主要流体包裹体表明形成了渗流环境，盐度在1,800至14,000 ppm之间，表明微咸但非海洋环境。此外，石膏的〜（87）Sr /〜（86）Sr值在0.708034和0.708120之间，高于Campanian-Maastrichtian年龄的海洋蒸发岩的值，表明淡水的影响明显。另一方面，石膏的δ〜（34）S VCDT值（18.1至19.0±0.5‰）和δ〜（18）OVSMOW值（11.0至15.2±0.5‰）是该年龄海洋蒸发物中记录的典型同位素值。 。流体包裹体和Sr同位素数据之间的这种明显矛盾可能是上白垩统蒸发岩再循环的结果。基于所有这些观察结果，含硫酸盐的层可能被解释为可能形成于普拉亚湖近海岸的盐滩中。总体而言，这项研究强调了在处理咸水环境中形成的蒸发物时，结合不同代理的重要性。

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