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Geology and palaeontology of the Codos anticline, eastern Iberian Chains, NE Spain: age constraints for the Ediacaran–Cambrian boundary in the Iberian Chains
Geological Magazine ( IF 2.3 ) Pub Date : 2021-07-23 , DOI: 10.1017/s0016756821000595
Michael Streng 1
Affiliation  

The two major structural elements of the Iberian Chains, the Datos and Jarque thrust faults, have been described as occurring in proximity in the area around the village of Codos. The purported Jarque fault corresponds to the axial plane of an anticline known as the Codos anticline, which exposes the oldest stratigraphic unit in this area, i.e. the Codos Bed, a limestone bed bearing skeletal fossils of putative Ediacaran or earliest Cambrian age. Details of the geology of the area and the age of the known fossils are poorly understood or not universally agreed upon. New investigations in the anticline revealed the presence of a normal fault, introduced as the Codos fault, which cross-cuts the course of the alleged Jarque fault. The vertical displacement along the axial plane of the anticline appears to be insignificant, challenging the traditional interpretation of the plane as an equivalent of the Jarque thrust fault. Reinvestigation of the Codos Bed revealed previously unknown skeletal fossils of early Cambrian age, confirming notions that the bed is younger than traditionally assumed. In particular, two helcionelloid molluscs, Anabarella cf. plana and Igorella? sp., allow correlations with Terreneuvian strata of central Spain (Pusa and Fuentepizzara formations) and support previously suggested connections with the Heraultia Limestone of southern France. Former identification of the terminal Ediacaran index-fossil Cloudina in the bed is erroneous. Consequently, the Ediacaran–Cambrian boundary in the Iberian Chains, which has been placed at the top of the formation overlying the Codos Bed, is stratigraphically distinctly lower.



中文翻译:

西班牙东北部伊比利亚链东部科多斯背斜的地质和古生物学:伊比利亚链中埃迪卡拉纪-寒武纪边界的年龄限制

伊比利亚链的两个主要结构元素,Datos 和 Jarque 逆冲断层,被描述为发生在 Codos 村周围的附近地区。据称的 Jarque 断层对应于称为 Codos 背斜的背斜的轴向平面,它暴露了该地区最古老的地层单元,即 Codos Bed,这是一个石灰岩床,上面有假定的埃迪卡拉纪或最早寒武纪时代的骨骼化石。该地区的地质细节和已知化石的年龄知之甚少或没有得到普遍认同。对背斜的新调查揭示了一个正断层的存在,作为 Codos 断层引入,它横切了所谓的 Jarque 断层的走向。沿背斜轴向平面的垂直位移似乎微不足道,挑战了将平面视为等同于雅克逆冲断层的传统解释。对科多斯床的重新调查揭示了以前未知的寒武纪早期骨骼化石,证实了该床比传统假设要年轻的概念。特别是,两种螺旋体软体动物,Anabarella cf。普拉纳伊戈雷拉?sp.,允许与西班牙中部的 Terreneuvian 地层(Pusa 和 Fuentepizzara 地层)相关,并支持之前提出的与法国南部Heraultia石灰岩的联系。以前在床上对埃迪卡拉纪末期指数化石Cloudina的鉴定是错误的。因此,位于科多斯床上方地层顶部的伊比利亚链中的埃迪卡拉纪-寒武纪边界在地层上明显较低。

更新日期:2021-07-23
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