Geochemical, sedimentary and micropaleontological evidence for a Late Maastrichtian oceanic seamount within the Pindos ocean (Arvi Unit, S Crete, Greece)

摘要

We test the model of Bonneau (1984) who hypothesised that the Arvi Unit in southern Crete represents Upper Cretaceous oceanic crust of a Pindos oceanic basin. The Arvi Unit is dominated by basaltic lava flows, pelagic carbonates and terrigenous sandstone turbidites. The "enriched" within-plate-type geochemistry of the basaltic lavas is consistent with a seamount setting. The subaqueous lava structures and associated pelagic carbonates further justify a seamount origin. Peperites composed of lava-pelagic carbonate mixtures date the Arvi Unit as Late Maastrichtian using diagnostic planktic foraminifera. The lavas are overlain by pelagic carbonates, also of Late Maastrichtian age, that then pass gradationally upwards into sand to pebble-grade gravity flows. The clastic sediments contain grains derived from several sources, namely continental (metamorphic and plutonic), ophiolite-related (e.g. serpentinite, gabbro, diabase), deep-sea (e.g. chert, pelagic carbonate) and shallow-marine (e.g. shell fragments). The terrigenous detritus is inferred to have come from the Pelagonian microcontinent unit (~. Asteroussia nappe) then to the northeast where ophiolites and deep-sea sediments were obducted during Late Jurassic time. The inferred Arvi seamount was accreted at the southeasterly-subducting active margin of the Pelagonian microcontinent after Maastrichtian time, related to closure of the Pindos ocean. The new evidence from the Arvi Unit provides additional evidence for the existence of the Pindos ocean between the Apulian and Pelagonian continental units in the Greece-Albania region.