Sharks (Neoselachii) and palynomorphs from Mendoza (Argentina): new evidence of the Late Cretaceous Atlantic marine transgression

摘要

Neoselachian (modern shark) teeth and palynomorphs have been recovered from the Late Cretaceous Jagüel Formation in the Province of Mendoza, Argentina. The fossiliferous beds were deposited during the Atlantic transgression that covered northern Patagonia and other parts of South America from the Maastrichtian to the Danian. Teeth of several lamniform sharks are attributed to the anacoracid Squalicorax pristodontus and cf. Serratolamna serrata of indeterminate familial affinity. These taxa became extinct at the end of the Cretaceous and confirm the late Maastrichtian age previously assigned to the Jagüel Formation in this northwestern part of the Neuquén Basin. For the first time, the selachian faunas are described together with algae and dispersed organic matter assemblages (palynofacies), revealing new elements of the neritic biota leading up to the Cretaceous–Paleogene (K–Pg) mass extinction in South America. The palynoflora consists exclusively of the prasinophyte algae Tasmanites, Cymatiosphaera and Pterospermella, indicative of stratified saline waters. Dispersed organic components in the profile (mainly opaque equidimensional phytoclasts and prasinophytes) are consistent with an inner neritic environment, with evidence (a great variety of particle sizes, lath-shaped phytoclasts increasing slightly in number and decreasing number of marine components) of slightly more nearshore conditions towards the upper part of the profile. These marine biotas confirm the presence of an epeiric sea over northern Patagonia, which extended westwards to the volcanic arc on the western flank of the Andean Cordillera in Mendoza.