The Ediacaran-Cambrian transition in the Cantabrian Zone 1 (North Spain): sub-Cambrian weathering, K-metasomatism and provenance of detrital series

Ugidos, J.M., Barba, P., Valladares, M.I., Suarez, M. and Ellam, R.M. (2016) The Ediacaran-Cambrian transition in the Cantabrian Zone 1 (North Spain): sub-Cambrian weathering, K-metasomatism and provenance of detrital series. Journal of the Geological Society, 173(4), pp. 603-615. (doi: 10.1144/jgs2016-004)

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Abstract

The Upper Ediacaran detrital succession in the Cantabrian Zone shows geochemical and mineralogical changes resulting from sub-Cambrian weathering during the Late Ediacaran worldwide sea-level fall. Relative to the unaltered rocks the altered ones show crosscutting rubefaction of varying thickness and remarkable increase in illite, K2O, Rb and Cs indicating K-metasomatism, and also depletion in MgO, CaO, Na2O, Be and Sr, but not in Zr, Nb, Y or Sc. The basal Cambrian siliciclastic rocks mostly consist of detritus derived from the Ediacaran materials, as demonstrated by the geochemical and Nd-isotope data (εNd(t) ranges are −3.4 to −2.1 and −3.6 to −1.8, respectively). However, these geochemical features of the basal Cambrian change upwards to more evolved compositions with lower εNd(t) values (−4.9 to −5.8). This change coincides with the Ediacaran–Cambrian unconformity in the Central Iberian Zone, and the Ediacaran siliclastic rocks of this zone and their unaltered equivalents of the Cantabrian Zone share the same geochemical features. This geochemical homogeneity rules out a significant coeval juvenile contribution to the Upper Ediacaran series. Thus, the juvenile supply was from a geological setting different from that in which the Ediacaran series were finally deposited.

Item Type:Articles
Additional Information:Financial support for this work was provided by the CGL2007-60035BTE and CGL2010-18905BTE projects of the MICINN (Spain).
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Ellam, Professor Rob
Authors: Ugidos, J.M., Barba, P., Valladares, M.I., Suarez, M., and Ellam, R.M.
College/School:College of Science and Engineering > Scottish Universities Environmental Research Centre
Journal Name:Journal of the Geological Society
Publisher:Geological Society of London
ISSN:0016-7649
ISSN (Online):2041-479X
Published Online:08 April 2016
Copyright Holders:Copyright © 2016 The Authors
First Published:First published in Journal of the Geological Society 173(4): 603-615
Publisher Policy:Reproduced in accordance with the publisher copyright policy

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