New biochronological and igneous geochemical evidence of Middle Jurassic to Early Cretaceous basaltic volcanism related to rifting and spreading of the S Neotethys (Antalya Complex northern outcrop), SW Türkiye

The objective of this research is to better understand the timing and processes of continental rifting and passive margin development of the Southern Neotethys in the Eastern Mediterranean region, mainly by using a combination of biochronology and igneous chemistry of basaltic rocks. The study area, the northern outcrop of the Antalya Complex (Antalya nappes) in the Isparta Angle exemplified multi-stage continental rifting during Permian-Triassic. New evidence is presented here from the relatively little-known northern outcrop, near the apex of the Isparta Angle. In this area, three related tectono-stratigraphical units and ophiolitic rocks were emplaced onto adjacent Mesozoic carbonate platforms during latest Cretaceous-Palaeocene. One of these, the Middle Antalya Unit, includes important evidence of rift and passive margin-related deep-sea sediments and basaltic volcanics. These lithologies occur within 1: Upper Permian-uppermost Cretaceous successions of relatively distal deep-sea sediments (e.g., radiolarites, pelagic carbonates) that in places are depositionally associated with (i.e., underlain, interbedded or overlain by) basaltic lavas; 2. Local successions of deep-sea sediments preserved as blocks and dismembered thrust sheets within uppermost Cretaceous (Campanian-Maastrichtian) sedimentary melange (olistostromes). The depositional ages reported here are mainly based on new radiolarian biochronology, in relation to associated basaltic rocks. On this basis, two main phases of volcanism are recognised: first, Late Triassic OIB to locally MORB, and secondly Mid-Jurassic-Early Cretaceous OIB, E-MORB and N-NMORB. Taking account of the local to regional geology, and rare occurrences of related Upper Permian alkaline volcanics, the Upper Triassic volcanics are interpreted to represent late-stage continental break-up and initial seafloor spreading. In contrast, the Middle Jurassic-Early Cretaceous volcanics represent renewed rifting/sea floor spreading that opened the S Neotethys to it maximum width. Subsequent regional crustal contraction triggered the formation and eventual emplacement of Upper Cretaceous supra-subduction zone ophiolites and the deep-sea sedimentary and volcanic rocks discussed here.