The carbonates of the post-Variscan basins of Sardinia: the evolution from Carboniferous–Permian humid-persistent to Permian arid-ephemeral lakes in a morphotectonic framework

Abstract

Late to post-Variscan sedimentary basins of Sardinia were influenced during Pennsylvanian to Permian times by two main tectono-sedimentary cycles: a Pennsylvanian to Cisuralian cycle represented mainly by dark limnic deposits, overlain by a Guadalupian to a possibly Lopingian cycle, mostly characterized by red-bed deposits. Lacustrine waterbodies developed in some sedimentary basins that were filled with siliciclastic to frequently early silicified carbonate deposits, depending on the climate and environmental conditions, landscape morphology and tectonic regime. The limnic successions of the lower tectono-sedimentary cycle were deposited in permanent, tens of metres deep lakes in deep, narrow tectonic strike-slip basins under a temperate to warm-humid climate. They started as lakes with terrigenous sedimentary input and developed minor carbonate deposits mainly at the end of their story. Conversely, the red-bed successions of the upper cycle were deposited in ephemeral, shallow playa lakes related to wider basins in an extensive alluvial plain under a hot and arid climate. Here, the siliciclastic sediments are intercalated with thin carbonate beds that are typical of a high evaporation rate. The evolution of the lake type could be related not only to a major climatic shift, but also to the changing morphotectonic conditions of the Variscan chain influencing the local microclimate. Comparisons with coeval successions in the Provence Basin, the Massif Central Aumance basin (France) and the Saar–Nahe Basin (Germany) show both similarities and differences between the basins.

The Atlas-East Variscan -Elbe shear system and its role in the formation of the pull-apart Late Palaeozoic basins

“…Many Late Palaeozoic basins can be recognised along the intracontinental EVSZ: the Western, Central and Eastern Alps, Sardinia, Corsica, Maures and Northern Apennines Basins are all considered to be half-graben/pull-apart basins (e.g., Rau 1993;Eichhorn et al 2000;Valente and Borghi 2000;Capuzzo and Bussy 2001;Pandeli 2002;Cassinis et al 2003bCassinis et al , 2008Cassinis et al , 2012Corsini et al 2004;McCann et al 2008;Mugnier et al 2008;Ballèvre et al 2018;Costamagna 2019). Notably, the Late Carboniferous, N-MORB/T-MORB tholeiites were emplaced during the opening of the Versoyen Basin of the Western Alps (Mugnier et al 2008), which is consistent with EVSZ activity.…”

Heavy metal and metalloid accumulation in wild brown trout (Salmo trutta L., 1758 complex, Osteichthyes: Salmonidae) from a mountain stream in Sardinia by ICP-OES

“…Cyclic siliciclastic depositions characterize the Montarbu area in the water basin. Stratigraphy showed episodic deposition of carbonate beds and volcanic products (Costamagna, 2019). Mica from the phyllosilicate family formed by parallel sheets of silicate that characterize the Ermolinus River shows residues of Al, K, Mn, Fe, Zn and Ca (Charette & Sholkovitz, 2006).…”

Clay mineral diagenesis and red bed colouration: A SEM study of the Gercus Formation (Middle Eocene), northern Iraq

“…The Middle Eocene‐aged Gercus Formation was deposited in a fluvial‐aeolian setting (Hussain & Aghwan, 2015) with a range of sedimentary environments (alluvial fans, wadis, dunes, interdunes, and playas) occurring (cf. Costamagna, 2019). Deposition took place under arid to wet conditions.…”