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首页> 外文期刊>Journal of South American earth sciences >The Chachil Limestone (Pliensbachian-earliest Toarcian) Neuquen Basin, Argentina: U-Pb age calibration and its significance on the Early Jurassic evolution of southwestern Gondwana
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The Chachil Limestone (Pliensbachian-earliest Toarcian) Neuquen Basin, Argentina: U-Pb age calibration and its significance on the Early Jurassic evolution of southwestern Gondwana

机译：阿根廷Chachil石灰石（普林斯巴赫最早的Toarcian）内乌肯盆地：U-Pb年龄定标及其对冈瓦纳西南部侏罗纪早期演化的意义

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摘要

New radiometric U-Pb ages obtained on zircon crystals from Early Jurassic ash layers found within beds of the Chachil Limestone at its type locality in the Chachil depocentre (southern Neuquen Basin) confirm a Pliensbachian age (186.0 ± 0.4 Ma). Additionally, two ash layers found in limestone beds in Chacay Melehue at the Cordillera del Viento depocentre (central Neuquen Basin) gave Early Pliensbachian (185.7 ± 0.4 Ma) and earliest Toarcian (182.3 ± 0.4 Ma) U-Pb zircon ages. Based on these new datings and regional geological observations, we propose that the limestones cropping out at Chacay Melehue are correlatable with the Chachil Limestone. Recent data by other authors from limestones at Serrucho creek in the upper Puesto Araya Formation (Valenciana depocentre, southern Mendoza) reveal ages of 182.16 ± 0.6 Ma. Based on these new evidences, we consider the Chachil Limestone an important Early Jurassic stratigraphic marker, representing an almost instantaneous widespread flooding episode in western Gondwana. The unit marks the initiation in the Neuquen Basin of the Cuyo Group, followed by widespread black shale deposition. Accordingly, these limestones can be regarded as the natural seal of the Late Triassic -earliest Jurassic Precuyano Cycle, which represents the infill of halfgrabens and/or grabens related to a strong extensional regime. Paleontological evidence supports that during Pliensbachian-earliest Toarcian times these limestones were deposited in western Gondwana in marine warm water environments.
机译：在Chachil沉积中心（南部内乌肯盆地）的Chachil石灰岩床中发现的侏罗纪早期灰烬层的锆石晶体上获得的新的放射性U-Pb年龄证实了Pliensbachian年龄（186.0±0.4 Ma）。此外，在科尔迪勒拉－德尔维恩托中心（中部内乌肯盆地）Chacay Melehue的石灰岩层中发现的两层灰烬层，形成了早普利恩斯巴赫（185.7±0.4 Ma）和最早的Toarcian（182.3±0.4 Ma）U-Pb锆石年龄。基于这些新的测年和区域地质观测，我们建议在Chacay Melehue种植的石灰岩与Chachil石灰岩相关。其他作者的最新数据来自Puesto Araya上部地层（Valdociana depocentre，Mendoza南部）Serrucho小河的石灰岩，其年龄为182.16±0.6 Ma。基于这些新证据，我们认为Chachil石灰岩是重要的早侏罗世地层标记，代表了冈瓦纳西部几乎几乎是一次广泛的洪水事件。该单元标志着库约群在内乌肯盆地的开始，随后是广泛的黑色页岩沉积。因此，这些石灰岩可以被认为是晚三叠世-最早的侏罗纪Precuyano循环的天然印记，它代表了与强扩张机制有关的半粒状和/或grab陷的充填。古生物学证据支持，在Pliensbachian最早的Toarcian时期，这些石灰石沉积在海洋温水环境下的Gondwana西部。

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  • 来源
    《Journal of South American earth sciences》 |2013年第3期|171-185|共15页
  • 作者

    H.A. Leanza; A. Mazzini; F. Corfu; E.J. Llambias; H. Svensen; S. Planke; O. Galland;

  • 作者单位

    Serviao Geologico Minero Argentino and CONICET, Av. Julio A. Roca 651, 1322 Buenos Aires, Argentina;

    Physics of Geological Processes, University of Oslo, Sem Saelandsvei # 24, Box 1048, 0316 Oslo, Norway;

    Department of Geosciences, University of Oslo, PO Box 1047 Blindern, 0316 Oslo, Norway;

    Centra de Investigaciones Geologicas, Universidad National de la Plata, Calle 1 - # 644, 1900 La Plata, Argentina;

    Physics of Geological Processes, University of Oslo, Sem Saelandsvei # 24, Box 1048, 0316 Oslo, Norway;

    Physics of Geological Processes, University of Oslo, Sem Saelandsvei # 24, Box 1048, 0316 Oslo, Norway,Volcanic Basin Petroleum Research (VBPR), Oslo Research Park, 0349 Oslo, Norway;

    Centra de Investigaciones Geologicas, Universidad National de la Plata, Calle 1 - # 644, 1900 La Plata, Argentina;

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  • 关键词

    radiometric ages; pliensbachian/toarcian boundary; early jurassic; chachil limestone; precuyano cycle; neuquen basin;

    机译：辐射年龄普林斯巴赫/陶氏边界;侏罗纪早期;Chachil石灰石前cuyano周期;内乌肯盆地;

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