Palynological analysis of a Lower Cretaceous subsurface succession from the south flank of the Golfo San Jorge Basin, Argentina

Abstract

Abundant and well-preserved palynological assemblages recovered from the Las Heras Group and Pozo D-129 Formation in the YPF.SC.PL x-2 (Puesto Ludden) are analyzed. This well includes the most complete Lower Cretaceous succession along the south flank of the Golfo San Gorge Basin. The palynofloras comprise fifty spore species, twenty-eight pollen taxa (including two angiosperm pollen taxa) and four algae. A late Valanginian–Hauterivian age is suggested for the Las Heras Group based mainly on the presence of Cyclusphaera psilata, Foraminisporis variornatus and Celyphus rallus and the absence of angiosperm pollen. These assemblages can be correlated with the Interulobites-Foraminisporis Zone (upper Valanginian–Hauterivian) of the Austral Basin. On the other hand, a Barremian-early Aptian age for the palynofloras from the Pozo D-129 Formation is suggested based on the sparse angiosperm pollen grains identified (Clavatipollenites sp. and Afropollis sp.) and it is correlated with the Antulsporites-Clavatipollenites Zone (Aptian) of the Austral Basin. These palynofloras from the Pozo D-129 Formation are representative of the initial late Barremian-Aptian phase of the early angiosperm diversification in central and southern Argentinean basins.