Upper Valanginian – Hauterivian calcareous dinoflagellate cyst and calpionellid zones from the Agrio Formation (Neuquén Basin), Argentina

Abstract

In this paper we describe for the first time the calcareous dinoflagellate cysts and calpionellid associations from upper Valanginian-Hauterivian orbital-driven rhythmic distal ramp deposits (Agrio Formation) in the Neuquén Basin, Argentina. Three stratigraphic sections from the northern Neuquén province (Loma La Torre and El Portón) and southern Mendoza province (Arroyo Loncoche) were studied. The Agrio Formation contains a low diverse association of these microfossils, among which ten calcareous dinoflagellate cyst species and five calpionellid species were recognized, all of them known from the Lower Cretaceous pelagic sediments of the Tethyan region. Two calcareous dinoflagellate cyst zones (Carpistomiosphaera valanginiana, and Stomiosphaera echinata), as well one calpionellid zone (Tintinnopsella), previously proposed for the Tethyan realm, are confirmed for the Agrio Formation. These zones are consistent to late Valanginian - Hauterivian age assignments previously established based on ammonites, nannofossils, and organic-walled dinoflagellate cysts.