Late Precambrian to Paleozoic evolution of the Carnic Alps: new constraints on paleogeography and terrane transfer along the northern margin of Gondwana

We present new U Pb detrital zircon ages and major-element, trace-element, and isotopic compositions of the Ediacaran to Permian sedimentary successions of the Carnic Alps, Italy-Austria, to constrain the depositional history, provenance, and paleogeographic and paleotectonic setting of this world-class area of Paleozoic stratigraphy. Our data show that the lowermost Val Visdende Formation has an Ediacaran maximum depositional age (586 ± 6 Ma) and thus represents one of the oldest basement units in the Alps. The formation was deposited at the northern margin of Gondwana in a back-arc basin adjacent to the Trans-Saharan Belt and Saharan Metacraton. The overlying Ordovician successions record the initial breakup of the Paleocarnic chain from the northern Gondwana margin, followed by Silurian and Lower Devonian predominantly carbonate deposition either under reef or deep-shelf to anoxic deep-shelf conditions, near the same sources as the underlying Ordovician strata. The Early Devonian evolution reflects continued northward drift of the Paleocarnic chain with limestone deposition in an extensional regime, characterized by progressive basin deepening and pelagic sedimentation that persisted until the lowermost Viséan. The subsequent Carboniferous evolution is marked by extensive siliciclastic turbidite (flysch) deposition, reflecting the onset of the Variscan orogeny when the Paleocarnic chain approached an active arc and Laurussia during the closure of the Rheic Ocean. Following the Variscan orogeny and erosion of paleorelief, deposition of Guadalupian continental red beds reflects post-orogenic extensional/strike-slip tectonics within the Pangaea supercontinent accompanied by widespread intra-plate magmatism. • Zircon ages and geochemistry constrain Paleozoic evolution of the Carnic Alps. • Ediacaran sedimentation sourced from the Trans-Saharan Belt and Saharan Metacraton. • Ordovician strata records the initial breakup of the Paleocarnic chain. • Paleocarnic chain drifted northward from Gondwana through the Devonian. • Carboniferous evolution marks the onset of the Variscan orogeny.