CONICET | Buscador de Institutos y Recursos Humanos

The sediments of the Neuquén Basin are characterized by alternating transgressive marine and regressive non-marine phases. In consequence, the stratigraphical record of dinoflagellates is discontinuous. However, the information they provide is sufficient for this tentative paleobiogeographical evaluation. An Australian connection is inferred for the Late Pliensbachian-?Aalenian from boreholes information (unpublished) due to the presence of taxa corresponding to the Dapcodinium priscum Oppel Zone Helby et al. In the Early Middle Bajocian an Australian connection could be inferred due to the prominence of rhaetogonyaulacoid cysts together with Nannoceratopsis species and the restricted occurrence of gonyaulacoid taxa. During Middle - Upper Callovian the dinocyst assemblage is characterized by the appearance of chorate cysts and a relative endemic content with species which occur in Arctic and Boreal Realms. The Tethyan Realm is characterized by Endoscrinium galeritum and Lithodinia jurassica. The presence of Scrinodinium crystallinum indicated an European and Australasian connections in the Late Callovian. During the Lower to Middle Tithonian, Acantahulax spp. and Escharisphaeridia pocockii are registered. They occur in Arctic and Boreal assemblages, while Apteodinium reticulatum and Jansonia spp. are characteristics of the transitional (Canadian) province. There is a marked increase in dinocysts diversity during the upper Middle to Upper Tithonian with species that occur in the Boreal (northwest Europe) and/or transitional Canadian provinces. As pointed Damborenea (1993) for bivalve species the occurrence of typically Tethyan bivalves in the same area as high-latitude bivalve species is a consequence of a mid-latitude position of this region without significant barriers. Her evaluation could be extended for the dinocysts assemblages here considered.

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