Mid Jurassic (Late Callovian) dinoflagellate cysts from the Lotena Formation of the Neuquén Basin, Argentina and their palaeogeographical significance

The Lotena Formation from two localities, Picún Leufú and Portada Covunco, in the Neuquén Basin of westcentral
Argentina was studied palynologically. The material examined produced moderately diverse Late
Callovian dinoflagellate cyst assemblages. This age assignment is consistent with ammonite evidence. The
dinoflagellate cyst floras are reminiscent of the Middle Jurassic associations of northwest Europe and
surrounding areas. Marine palynomorphs typical of Australasia and the Arctic are absent. The similarity with
Europe is strongly suggestive of an open marine connection between western Tethys and the Neuquén Basin
during the Late Callovian. This is interpreted as being via the Hispanic Corridor, with the palynofloras being
passively dispersed to the southwest by the circum-Tropical Marine Current. Earlier studies indicate that this
trans-Pangean equatorial seaway first began to allow biotic interchange during the Mid Jurassic and this study
proves that this open marine connection was established by the Late Callovian. The similarities between the
dinoflagellate cyst assemblages of Europe and the Neuquén Basin are consistent with the distribution of other
marine fossils and the existence of geographically continuous marine facies belts.