The problematic origin of the Pancherot-Cime Bianche-Bettaforca unit (PCB) in the Piemonte zone (Western Alps)

IF 1 4区地球科学 Q4 GEOSCIENCES, MULTIDISCIPLINARY

Italian Journal of Geosciences Pub Date : 2018-10-01 DOI:10.3301/IJG.2018.21

L. Passeri, G. Ciarapica, G. D. Dal Piaz

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引用次数: 3

Abstract

The Pancherot-Cime Bianche-Bettaforca (PCB) is an ophiolite-free decollement cover unit with a greenschist facies imprint, continental affinity and problematic provenance. It is located in the ophiolitic Piemonte zone which marks the suture in the north-western Alps of the Mesozoic Liguria-Piemonte ocean (western Tethys). A new stratigraphic reconstruction of this unit is presented. It includes the following main lithofacies: Quartzitic Schists and metaconglomerates (Permian), Yellowish Quartzite (Early Triassic), Bedded Dolostone and Marbles (Middle Triassic), Tabular White Quartzite (Carnian), Massive Dolostone (Norian), Carnieules and Brown Marble (Rhaetian-Jurassic). Ages are hypothetical because no fossil has been found.Comparison with the Prepiemontese and Austroalpine sedimentary successions shows major affinity with the Austroalpine cover units.The continental basement of this exotic unit is unknown. Suitable candidates can be considered the Mt Emilius and other Lower Austroalpine eclogitic outliers, as these continental slices are missing of a sedimentary cover and are located inside the ophiolitic Piemonte zone, near the structural level of the PCB unit. In this view, thesebasement and cover units were decoupled during subduction due to their contrasting metamorphic features.

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西阿尔卑斯皮埃蒙特地区Pancherot-Cime Bianche-Bettaforca单元(PCB)的起源问题

Pancherot Cime Bianche Bettaforca（PCB）是一个无蛇绿岩的脱集合盖层单元，具有绿片岩相印记、大陆亲和性和有问题的物源。它位于蛇绿质皮埃蒙特带，标志着中生代利古里亚-皮埃蒙特洋（特提斯西部）西北阿尔卑斯山脉的缝合线。对该单元进行了新的地层改造。它包括以下主要岩相：石英质片岩和变砾岩（二叠纪）、黄石英岩（三叠纪早期）、层状白云岩和大理石（三叠纪中期）、片状白石英岩（卡尼阶）、块状白云岩（诺里阶）、卡尼厄勒斯和棕色大理石（雷蒂阶-侏罗纪）。年代是假设的，因为还没有发现化石。与Prepiemontese和Austroalpine沉积序列的比较显示出与Austroalpine-盖层单元的主要亲和力。这个奇特单元的大陆基底是未知的。合适的候选者可以被认为是埃米利厄斯山和其他下奥高山榴辉岩异常值，因为这些大陆片缺少沉积盖层，并且位于蛇绿质皮埃蒙特带内，靠近PCB单元的结构水平。在这种观点中，这些基底和盖层单元在俯冲过程中由于其对比鲜明的变质特征而解耦。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Italian Journal of Geosciences GEOSCIENCES, MULTIDISCIPLINARY-

CiteScore

2.90

自引率

11.10%

发文量

审稿时长

>12 weeks

期刊介绍： The Italian Journal of Geosciences (born from the merging of the Bollettino della Società Geologica Italiana and the Bollettino del Servizio Geologico d''Italia) provides an international outlet for the publication of high-quality original research contributions in the broad field of the geosciences. It publishes research papers, special short papers, review papers, discussion-and-replies for their rapid distribution to the international geosciences community. The journal is firstly intended to call attention to the Italian territory and the adjacent areas for the exceptional role they play in the understanding of geological processes, in the development of modern geology and the Earth sciences in general. The main focus of the journal is on the geology of Italy and the surrounding sedimentary basins and landmasses, and on their relationships with the Mediterranean geology and geodynamics. Nevertheless, manuscripts on process-oriented and regional studies concerning any other area of the World are also considered for publication. Papers on structural geology, stratigraphy, sedimentology, basin analysis, paleontology, ecosystems, paleoceanography, paleoclimatology, planetary sciences, geomorphology, volcanology, mineralogy, geochemistry, petrology, geophysics, geodynamics, hydrogeology, geohazards, marine and engineering geology, modelling of geological process, history of geology, the conservation of the geological heritage, and all related applied sciences are welcome.