Review of the Upper Ediacaran-Lower Cambrian detrital series in Central and North Iberia: NE Africa as possible source area

Abstract

This work offers a review of the Upper Ediacaran and Lower Cambrian succession in the Central and North Iberian Massif. The aim is to simplify the terminology and stratigraphic descriptions to ensure that the treatment of all available geochemical data is more easily understood. In general terms, the stratigraphic succession comprises of three depositional sequences. Depositional sequence 1, of Ediacaran age, is incomplete and only appears in the Cantabrian and West Asturian Leonese zones. Depositional sequence 2, of Late Ediacaran age, is found in the Central Iberian zone and corresponds to a sedimentary wedge having the Cantabrian and West Asturian Leonese zones as a secondary area of origin. Depositional sequence 3, of Early Cambrian age, appears in the three zones of study. Samples from all the three sequences have been selected for analytical purposes. The samples were collected within stratigraphic series previously studied but also randomly. In total 240 analyses of major and trace elements and 36 analyses of Nd-isotopes have been considered in the current work. Geochemical data for the Upper Ediacaran detrital rocks of the Central and North Iberia provides evidence of a remarkable geochemical uniformity (trace elements, Nd-isotopes) despite the distances separating the sampling areas. The geochemical uniformity shown by the Upper Ediacaran siliciclastic sediments from the three zones is probably the most important result. So, it is proposed that the extensive volumes of first cycle detrital materials in the Arabian-Nubian Shield mixed with older crustal materials from the Saharan Metacraton and that these mixtures evolved and homogenized in a continental setting across NE Africa prior to final sedimentation in a marine basin. The Lower Cambrian succession corresponds to decreased relative proportions of detritus derived from the Arabian-Nubian Shield.