Lithostratigraphy of the “Schist-Greywacke Domain” in Portugal: a reappraisal

Abstract

A synthesis of the knowledge of the Schist-Greywacke Domain (SGD) in Portugal is here presented. Until recently, this sequence assumed the designation of Dúrico-Beirão Supergroup composed by the Douro Group (DG) and the Beiras Group (BG). The DG is considered of Neoproterozoic – Cambrian age and the BG is of Neoproterozoic age. The identification and mapping in the BG of an unconformity as the Cadomian unconformity identified in Spain, which splits the Neoproterozoic in “lower Alcudian” and “upper Alcudian”, is a turning point for the understanding and establishment of consistent stratigraphic sequences that now compose the Fróia and the Lousã groups assembled in the Beiras Supergroup. These new groups are correlated with the Neoproterozoic sequences currently recognized in Spain: the Lousã group is equivalent to the Ibor Group (upper Alcudian) and the Fróia Group is equivalent pro parte, to the Domo Extremeño Supergroup.

The Lusinde late-post-tectonic Variscan granite (Central Iberian Zone): pluton emplacement at the termination of the Juzbado-Penalva shear zone

“…In the Portuguese sector of the Central Iberian Zone, the crystalline basement comprises a thick Ediacaran-Lower Cambrian turbidite-like sequence, traditionally referred to as the Schist-Greywacke Complex (SGC) and more recently known as the Douro-Beiras Supergroup (DBSG) (e.g., Sousa, 1982;1984;Meireles et al, 2022). The DBSG megasequence is overlain by shallower marine siliciclastic deposits and volcanics of Lower Palaeozoic age preserved in the core of narrow NW-SE trending synclines.…”

Selected Geoheritage Resources of “Atlantic Geopark” Project (Central Portugal)

“…This consists of a metasedimentary sequence that extends from the Neoproterozoic to the Middle Cambrian (? ), commonly referenced as the "Schist-Greywacke Complex", and currently differentiated into the Douro Group and the Beiras Supergroup [17]. The latter, characterized by non-carbonate turbiditic facies, outcrops in the territory and is assigned to the Neoproterozoic.…”

“…They support a geo-itinerary that make it possible to reconstruct the geological history of two oceans-Rheic and Atlantic: the Oceans Route (Figure 4). The geological history of this territory starts east of the territory with the record of the Beiras Supergroup (635 Ma) [17] that represents the oldest record in the territory, and outcrops in Penacova area. This unit was deposited in the context of a back-arc sedimentary basin, associated with the evolution of a volcanic arc (Cadomian Orogeny; 650-550 Ma) which occurred on the margin of the Gondwana continent [26].…”

Zircon U–Pb Dating and Lu–Hf Isotopic Composition of Some Granite Intrusions in Northern and Central Portugal: Constraints on the Emplacement Age and Nature of the Source Rocks

“…The Vila Nova de Foz Côa-Freixo de Numão region is located in the CIZ, northern Portugal [43] (Figure 1b) and is characterized by the occurrence of the Douro Group (northern CIZ of [62]) metasedimentary sequence, composed of flysch-like alternations of metagreywackes, slates and metaconglomerates, with carbonates levels at the base, belonging to the upper Ediacaran-middle Cambrian [63][64][65][66][67]. In this area, two regional Variscan deformation phases are recognized (D 1 and D 3 ; [46,47]).…”

“…The Fundão-Capinha region lies within the CIZ, central Portugal, and is dominated by the Beiras Supergroup Neoproterozoic metasedimentary sequence (southern CIZ metasediments of [62]), consisting of a monotonous flysch-like succession of metagreywackes, slates and metaconglomerates, without carbonate intercalations [67,70]. In the studied area, this metasedimentary sequence displays a dominant NW-SE trending foliation (S 1 ) with vertical or subvertical dips (80 • -85 • SW) and voluminous intrusive granite batholiths.…”