Detrital Zircon Provenance of Triassic Sandstone of the Algarve Basin (SW

Geological Magazine Detrital zircon provenance of Triassic sandstone www.cambridge.org/geo of the Algarve Basin (SW Iberia): evidence of Gondwanan- and Laurussian-type sources of sediment Original Article 1 1 2 3 Cite this article: Gama C, Pereira MF, Cristina Gama , M Francisco Pereira , Quentin G Crowley , Ícaro Dias da Silva Crowley QG, Dias da Silva Í, and Silva JB (2021) and J Brandão Silva4 Detrital zircon provenance of Triassic sandstone of the Algarve Basin (SW Iberia): 1 evidence of Gondwanan- and Laurussian-type Instituto de Ciências da Terra, Departamento de Geociências, Escola de Ciências e Tecnologia, Universidade de 2 sources of sediment. Geological Magazine 158: Évora, Portugal; Department of Geology, School of Natural Sciences, Trinity College, Dublin 2, Ireland; 311–329. https://doi.org/10.1017/ 3Instituto D. Luiz, Departamento de Geologia, Faculdade de Ciências da Universidade de Lisboa, Portugal and S0016756820000370 4Instituto D. Luiz, Departamento de Geologia, Faculdade de Ciências da Universidade de Lisboa, Portugal Received: 2 October 2019 Revised: 6 February 2020 Abstract Accepted: 8 April 2020 Detrital zircon populations from six samples of upper Triassic sandstone (Algarve Basin) were First published online: 19 May 2020 analysed, yielding mostly Precambrian ages. zircon age populations of the Triassic sandstone Keywords: sampled from the western and central sectors of the basin are distinct, suggesting local recycling U–Pb geochronology; detrital zircon; Triassic and/or lateral changes in their sources. Our findings and the available detrital zircon ages from sandstone; Algarve Basin; Palaeozoic terrane; the Palaeozoic terranes of SW Iberia, Nova Scotia and NW Morocco were jointly examined sediment source; Pangaea palaeogeographic using the Kolmogorov–Smirnov test and multidimensional scaling diagrams. The obtained reconstruction results enable direct discrimination of competing Laurussian-type and Gondwanan-type Author for correspondence: sediment sources, involving recycling and mixing relationships. The detrital zircon populations M Francisco Pereira, of the Algarve Triassic sandstone are very different from those of the lower–upper Email: [email protected] Carboniferous Mértola and Mira formations (South Portuguese Zone), upper Devonian – lower Carboniferous Horta da Torre, Represa and Santa Iria formations (Pulo do Lobo Zone), and the late Carboniferous Santa Susana and early Permian Viar basins, which are ruled out as potential sources. The detrital zircon populations of Triassic sandstone from the central sector and those from the Ossa–Morena Zone Ediacaran–Cambrian siliciclastic rocks, upper Devonian – Carboniferous Ronquillo, Tercenas, Phyllite-Quartzite and Brejeira formations (South Portuguese Zone), and Frasnian siliciclastic rocks of the Pulo do Lobo Zone are not statistically distinguishable. Thus, sedimentation in the central sector was influenced by Gondwanan- and Laurussian-type putative sources exposed in SW Iberia, in contrast to the western sector, where Meguma Terrane and Sehoul Block Cambrian siliciclastic rocks allegedly constituted the main (Laurussian-type) sources. These findings provide insights into the denudation of distinctive source terranes distributed along the late Palaeozoic suture zone that juxtaposed the Laurussian and Gondwanan margins. 1. Introduction The petrography and geochemistry of siliciclastic rocks has widely been used to identify different sources, providing reliable information about provenance. In regions where information on the source of sediments and the occurrence of sediment recycling is difficult to evaluate using petrography and geochemistry, detrital zircon U–Pb geochronology may provide a useful means for testing potential sources (Andersen, 2005; Gehrels et al. 2011). Zircon grains found in siliciclastic rocks may derive directly from primary sources and/or represent recycled material from intermediate sediment repositories (Pereira et al. 2016a,b) associated with multiple sedimentary cycles (Morton et al. 2008; Thomas, 2011). Detrital zircon U–Pb ages are hence critically important to the process of creating a geological historical profile of sedimentary basins and their surrounding (local) and remote (external) source regions (Fedo et al. 2003). Often such a relationship is not readily recognizable because sources may have been displaced or separated, with a distance of hundreds of kilometres between them, as a result of the movement of the lithospheric plates. Following the complex process of the formation of Pangaea as a result of the collision © The Author(s), 2020. Published by Cambridge between Laurussia and Gondwana that led to the juxtaposition of distinct Palaeozoic terranes, University Press. both basements experienced uplift and erosion. As debris derives from different sources it is very likely that contrasting zircon age populations are recognizable in the Triassic basins formed during the first stages of the fragmentation of this supercontinent, where they were deposited. Mixed provenance may also be a significant phenomenon depending on the complexity of the dispersal paths connecting sources to the basins. According to palaeogeographic maps showing Downloaded from https://www.cambridge.org/core. University of Athens, on 02 Oct 2021 at 21:11:18, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0016756820000370 312 C Gama et al. the plate configuration, palaeoenvironment and lithofacies during and presents distinct features in terms of sedimentation and mag- late Triassic time, Iberia is located at the core of Pangaea and is matism (Fig. 2). A singular aspect of this area of the Variscan belt is bounded in the east by the Neotethys Ocean (Golonka, 2007). the absence of Silurian and Devonian plutonic rocks, whereas In the fragmentation stages of Pangaea, the separation of North Carboniferous plutons are found on both sides of the Rheic suture: America and Gondwana (Europe and NW Africa), initiated in the Sierra Norte batholith (c. 359–335 Ma; de la Rosa et al. 2002; early Triassic time, continued during late Triassic time with the Gladney et al. 2014), the Beja igneous complex (c. 353–350 Ma; Pin development of terrestrial clastic depositional systems in the region et al. 2008), the Valencia del Ventoso plutonic complex (c. 337–330 where the Central Atlantic spreading axis (Golonka & Ford, 2000) Ma; Cambeses et al. 2015) and the great variety of plutons from the later emerged during late Sinemurian time (c. 195 Ma; Sahabi et al. Évora massif (c. 341–324 Ma; Lima et al. 2012; Moita et al. 2015; 2004). In order to identify the potential sources of the late Triassic Pereira et al. 2015a; Dias da Silva et al. 2018). basins from the Central Atlantic Ocean realm, the configuration of The OMZ metasedimentary sequence extends from the the late Palaeozoic orogen, showing the probable spatial distribu- Ediacaran (Serie Negra Group) to the lower Devonian (Terena tion of the distinct provenances of the Palaeozoic terranes, before Formation), presenting large volumes of magmatic rocks ranging Pangaea fragmentation, must be reconstructed. Terrestrial from Ediacaran to early Ordovician in age (Sánchez-García et al. deposition was diachronous in Iberia (López-Gómez et al. 2003; Robardet & Gutiérrez Marco, 2004; Chichorro et al. 2008; 2019), presenting Late Permian – Middle Triassic ages in eastern Pereira et al. 2011, 2012b; Cambeses et al. 2017) (Fig. 3). and southeastern basins (Pyrenees, Iberian Ranges and Betics; Cambrian to lower Devonian metasedimentary sequences (Ossa, López-Gómez et al. 2005; Sánchez Martínez et al. 2012) and Fatuquedo, Barrancos, Colorada, ‘Xistos com Nódulos’, ‘Xistos Late–Middle Triassic ages in western and southwestern ones Raiados’, Russianas and Terena formations; Oliveira et al. 1991) (Lusitanian, Alentejo and Algarve basins: Palain, 1976; Azerêdo and Cambrian (Early-Rift and Main-Rift volcanism; Sánchez- et al. 2003; Alves et al. 2006; Soares et al. 2012; Pereira et al. García et al. 2010, 2013) to Ordovician (Sánchez-García et al. 2016b, 2017c; Dinis et al. 2018). 2003; Díez Fernández et al. 2015) magmatism are related to the The aim of this paper is to present findings for detrital zircon geodynamic evolution of the outermost Gondwanan passive mar- ages obtained from six samples of Triassic siliciclastic rocks of the gin of the Rheic Ocean (Sánchez-García et al. 2003; Linnemann Algarve Basin that complement information already published et al. 2008; Pereira et al. 2012b; Díez Fernández et al. 2016) (Fig. 3). (Pereira et al. 2017c; Dinis et al. 2018) and test for the existence Overlying sequences are represented by lower Carboniferous syn- of more than one potential source or mixed provenance. The orogenic marine sedimentary and volcanic rocks (Cabrela U–Pb data for the Algarve Triassic sandstone obtained in the Formation and Toca da Moura volcanic–sedimentary complex; present study are compared with a compilation of detrital zircon Pereira et al. 2012a and references therein), early to late ages from siliciclastic rocks of SW Iberia (upper Neoproterozoic Carboniferous Baleizão porphyries and upper Carboniferous ter- to Permian; Pereira et al. 2008, 2012a,b, 2017b; Linnemann restrial siliciclastic rocks of the Santa Susana Basin (Oliveira et al. et al. 2008; Braid et al. 2011; Rodrigues et al. 2015; Pérez- 1991; Machado et al. 2012) (Fig. 3). In SW Iberia, the Rheic suture Cáceres et al. 2017; Dinis et al. 2018), Nova Scotia

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