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首页> 外文期刊>Neues Jahrbuch fur Geologie und Palaontologie. Abhandlungen >Basin evolution of the margin of Gondwana at the Neoproterozoic/Cambrian transition: the Puncoviscana Formation of Northwest Argentina
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Basin evolution of the margin of Gondwana at the Neoproterozoic/Cambrian transition: the Puncoviscana Formation of Northwest Argentina

机译：新元古代/寒武纪过渡时期冈瓦纳边缘的盆地演化：阿根廷西北部的蓬科维斯卡纳组

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摘要

The Puncoviscana Formation is an important stratigraphic sequence of sandstones and shales, with intercalated conglomerates, limestones and volcanic rocks. It was deposited at the Neoproterozoic-Cambrian boundary in a shallow basin on the western margin of Gondwana. Trace fossils of the Puncoviscana Formation s.l. are represented by the Oldhamia and Nereites ichnoassociations and the geographical distribution of assemblages are aligned as parallel belts, with a shallower eastern Nereites association and a deeper western Oldhamia association. They represent different temporal levels on the evolution of the basin. Detrital zircon spectra display a wide range of ages, which indicate their provenance from Neoproterozoic to Cambrian source areas as well as Meso- to Paleoproterozoic basement units, exhibiting typical Gondwanan ages. Thick limestone banks are interbedded in the Puncoviscana Formation s.l. that included the siliciclastic sequences, with very low- to medium-metamorphic grade. δ~(13)C values for the limestones vary from -1.57 to +3.4‰ VPDB, while in the Sierras Pampeanas, δ~(13)C values vary from +2.6 to +8‰ VPDB. Also, reported ~(87)Sr/~(86)Sr values allow a clear differentiation of two rock sets. The limestones interbedded with the Puncoviscana Formation yielded values typical for the Neoproterozoic-Cambrian transition, between 0.70868 and 0.70896; while the limestones of the Sierras Pampeanas display values between 0.70748 and 0.70756, common in the Middle to Late Ediacaran. Deformation and uplift of the Puncoviscana Formation is clearly represented in northern Argentina by the Tilcarian unconformity, which is overlain by the Mesoón Group.
机译：蓬科维斯卡纳组是砂岩和页岩的重要地层层序，其中夹有砾岩，石灰岩和火山岩。它沉积在冈瓦纳西部边缘一个浅盆地的新元古代-寒武纪边界。 Puncoviscana组s.l.的痕迹化石。由Oldhamia和Nereites的ichnoassociations代表，集合体的地理分布排列成平行带，东部的Nereites协会较浅，西部的Oldhamia协会较深。它们代表了盆地演化的不同时空水平。碎屑锆石光谱显示了很宽的年龄范围，表明它们从新元古代到寒武纪源区以及从中元古到古元古代地下室的出处，都具有典型的冈瓦南年龄。厚厚的石灰岩堤层夹在Puncoviscana地层中。包括硅质碎屑序列，具有非常低到中等的变质等级。石灰岩的δ〜（13）C值在-1.57到+ 3.4‰VPDB之间变化，而在塞拉山脉的潘普拉亚纳斯山脉，δ〜（13）C值在VPDB上从+2.6到+ 8‰变化。同样，据报道的〜（87）Sr /〜（86）Sr值可以清楚地区分两个岩石组。与蓬斯科维斯卡纳层夹层的石灰岩的新元古代-寒武纪转变的典型值在0.70868至0.70896之间。而山脉山脉的石灰岩显示出的值介于0.70748和0.70756之间，在爱迪卡拉山脉的中晚期很常见。在阿根廷北部，Pilcoviscana地层的变形和隆升明显表现为Tilcarian不整合面，而Mesoón集团则将其覆盖。

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