Rovearinids (stemless crinoids) in the Albian carbonates of the offshore Santos Basin, southeastern Brazil: stratigraphic, palaeobiogeographic and palaeoceanographic significance

Microfacies analysis of marine carbonates cored by Petrobras well 1-SPS-6 i n the offshore Santos Basin (southeastern Brazil) has revealed a remarkable fossil assemblage of calpionellids (colomiellids), favusellids, hedbergell ids, globigerinelloidids, buliminids, radiolarians, inoceramid prisms, rove acrinids, and saccocomids(?) preserved in lower Albian calcimudstones-wacke stones of the lower part of the Guaruja Formation. This assemblage represen ts an allochtonous accumulation in a deep neritic to shallow bathyal hypoxi c environment. Besides 'saccocomid-like' sections, the only determinable se ctions of roveacrinids are thecal plates of Poecilocrinus dispandus elongat us Peck, 1943. This species was previously only known from the Weno Formati on of Texas. The Brazilian material extends its records farther south from at least the lower Albian, which then represents the earliest occurrence of this peculiar family in the South Atlantic region. Taking into account the ir Albian global distribution and the location of their oldest representati ve (Hauterivian near Alicante, Spain), the Roveacrinidae dispersed westward throughout all of Cretaceous Tethys. The Tethyan origin of Roveacrinidae i s further evidence that, during late Aptian-Albian times, the northern Sout h Atlantic (north of the Walvis-SBo Paulo Ridge) was supplied by a Tethyan water mass. (C) 2001 Elsevier Science Ltd. All rights reserved.