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<p>In view of their porosity, coquinas are excellent hydrocarbon reservoirs worldwide. This work presents a taphonomic and stratigraphic study of Pleistocene shell accumulations from Moreno Bay (Mejillones Peninsula, Chile) and Pleistocene-Holocene deposits from San Antonio Bay (Villarino Peninsula, Argentina). The Mejillones Formation records a transgressive to falling stage systems tract, and is the topmost sedimentary unit deposited in a half-graben preserved in the Mejillones Peninsula (northern Chile). The Villarino Peninsula deposits record a series of prograding beach ridges, mostly composed of shells and gravelly sediments. Taphofacies and lithofacies interpretation of stratigraphic profiles from both sites indicate high-energy subaqueous depositional environments, allowing their use as analogues for coquina reservoirs. The comparative analysis of taphofacies also revealed different levels of similarity between the fossil assemblages, based on characteristics such as packing, orientation and the degree of shell fragmentation. Although morphologically similar, the deposits resulted from distinct geological controls and processes: active tectonic uplift on the Mejillones Peninsula and tectonic stability episodes on the Villarino Peninsula. The main difference lies in the sediment composition: the Pleistocene profiles of San Antonio Bay (Argentina) are predominantly siliciclastic (clasts), whereas Moreno Bay (Chile) is dominated by bioclastic material (shells). The different tectonic and climatic contexts, hyperarid in Chile versus glacial fluvial input in Argentina, explain the compositional differences. The presented data demonstrate that similar coastal features can be generated by unique combinations of tectonic, eustatic and climatic controls, reinforcing the need for an integrated approach for the correct interpretation of palaeoenvironments.</p>

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Taphonomic and stratigraphic relationships among Quaternary coastal shell accumulations in Northern Patagonia and the Chilean desert

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年5月21日

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  • Iasmin Raíssa Beatrici,
  • Fernando Erthal,
  • Cristiano Fick,
  • Hugo Schmidt-Neto

摘要

In view of their porosity, coquinas are excellent hydrocarbon reservoirs worldwide. This work presents a taphonomic and stratigraphic study of Pleistocene shell accumulations from Moreno Bay (Mejillones Peninsula, Chile) and Pleistocene-Holocene deposits from San Antonio Bay (Villarino Peninsula, Argentina). The Mejillones Formation records a transgressive to falling stage systems tract, and is the topmost sedimentary unit deposited in a half-graben preserved in the Mejillones Peninsula (northern Chile). The Villarino Peninsula deposits record a series of prograding beach ridges, mostly composed of shells and gravelly sediments. Taphofacies and lithofacies interpretation of stratigraphic profiles from both sites indicate high-energy subaqueous depositional environments, allowing their use as analogues for coquina reservoirs. The comparative analysis of taphofacies also revealed different levels of similarity between the fossil assemblages, based on characteristics such as packing, orientation and the degree of shell fragmentation. Although morphologically similar, the deposits resulted from distinct geological controls and processes: active tectonic uplift on the Mejillones Peninsula and tectonic stability episodes on the Villarino Peninsula. The main difference lies in the sediment composition: the Pleistocene profiles of San Antonio Bay (Argentina) are predominantly siliciclastic (clasts), whereas Moreno Bay (Chile) is dominated by bioclastic material (shells). The different tectonic and climatic contexts, hyperarid in Chile versus glacial fluvial input in Argentina, explain the compositional differences. The presented data demonstrate that similar coastal features can be generated by unique combinations of tectonic, eustatic and climatic controls, reinforcing the need for an integrated approach for the correct interpretation of palaeoenvironments.