Arid continental basins typically contain a spectrum of coeval environments that coexist and interact from proximal to distal. Within the distal portion, aeolian ergs often border playa, or perennial, desert lakes, fed by fluvial incursions or elevated groundwaters. Evaporites are common features in these dryland, siliciclastic dominant settings. However, sedimentary controls upon evaporite deposition are not widely understood, especially within transitional zones between coeval clastic environments that are dominantly controlled by larger scale allocyclic processes, such as climate. The sulphur (δ³⁴S) and oxygen (δ¹⁸O, Δ¹⁷O) isotope systematics of evaporites can reveal cryptic aspects of sedimentary cycling and sulphate sources in dryland settings. However, due to the lack of sedimentological understanding of evaporitic systems, isotopic data can be easily misinterpreted. This work presents detailed sedimentological and petrographic observations, coupled with δ³⁴S, δ¹⁸O and Δ¹⁷O data, for the early Permian Cedar Mesa Sandstone Formation (western USA). Depositional models for mixed evaporitic/clastic sedimentation, which occurs either in erg‐marginal or lacustrine‐marginal settings, are presented to detail the sedimentary interactions present in terms of climate variations that control them. Sedimentological and petrographical analysis of the evaporites within the Cedar Mesa Sandstone Formation reveal a continental depositional environment and two end member depositional models have been developed: erg‐margin and lake‐margin. The δ³⁴S values of gypsum deposits within the Cedar Mesa Sandstone Formation are consistent with late Carboniferous to early Permian marine settings. However, a marine interpretation is inconsistent with sedimentological and petrographic evidence. Consequently, δ³⁴S, δ¹⁸O and Δ¹⁷O values are probably recycled and do not reflect ocean‐atmosphere values at the time of evaporite precipitation. They are most likely derived from the weathering of older marine evaporites in the hinterland. Thus, the results demonstrate the need for a combination of both sedimentological and geochemical analysis of evaporitic systems to better understand their depositional setting and conditions.

中文翻译：

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干旱大陆环境下过渡蒸发环境的沉积学和同位素地球化学：从erg湖到盐湖

干旱的大陆盆地通常包含一系列近代环境，从近端到远端共存并相互作用。在远侧部分，风成虫常与滩涂或多年生荒漠湖接壤，由河流入侵或升高的地下水喂养。在这些干旱的硅质碎屑占主导地位的地区，蒸发物是常见的特征。然而，对蒸发岩沉积的沉积控制尚未广为人知，尤其是在同时代碎屑环境之间的过渡带内，而这些过渡碎屑环境主要是由较大规模的异环过程（例如气候）控制的。硫（δ ³⁴ S）和氧（δ ¹⁸ O，Δ ¹⁷O）蒸发物的同位素系统可以揭示旱地环境中沉积循环和硫酸盐来源的隐秘方面。但是，由于缺乏对蒸发系统的沉积学认识，同位素数据很容易被误解。这项工作提出详细的沉积学和岩相学观察，加上δ ³⁴ S，δ ¹⁸ O和Δ ¹⁷O数据，为早二叠世Cedar Mesa砂岩地层（美国西部）。提出了在erg-margin或lacustrine-margin设置中发生的混合蒸发/碎屑沉积的沉积模型，以控制它们的气候变化来详细说明沉积相互作用。对Cedar Mesa砂岩组内蒸发物的沉积学和岩石学分析揭示了一个大陆性沉积环境，并且已经开发了两个端部成员沉积模型：erg-margin和lake-margin。的δ ³⁴Cedar Mesa砂岩组内的石膏沉积物的S值与石炭纪晚期至二叠纪早期海洋环境一致。但是，海洋解释与沉积学和岩石学证据不一致。因此，δ ³⁴ S，δ ¹⁸ O和Δ ¹⁷ O值很可能再循环并在蒸发盐析出时不反映海洋大气值。它们很可能是由腹地较旧的海洋蒸发物的风化引起的。因此，结果表明需要结合蒸发系统的沉积学和地球化学分析来更好地了解其沉积环境和条件。