CONICET | Buscador de Institutos y Recursos Humanos

The Patia-2 (308,8-1467,6 ft), Patía-25 (444-758,4 ft), and Patia-28 (713,5-1217,5 ft) wells drilled in the Cauca Patia Basin (SW Colombia), South America, were sampled for palynological and micropaleontological analysis to outline its age and sedimentary environments and hence, to contribute to oil and/or gas exploration. Black shales core samples (56 productive) yielded abundant, moderately preserved and diverse terrestrial angiosperms (59 species) and spores (52 species), over gymnosperms (4 species), fungal spores (17 species), and algae (7 species). Rare dinoflagellate cysts (4 species), and foraminifera test linings (some pyritized) and calcareous nannofossils were recorded as well. The palynostratigraphic subdivisions of the 1.977 feet thick succession based on the vertical distribution of diagnostic palynomorphs and foraminifers observed consist of three informal zones. Zone 1 at the base with Fenestrites spinosus of latest Middle Miocene to Late Miocene, Zone 2 directly above, dominated by Malvacipollis (Echitriporites) maristellae and Nijssenosporites fossulatus, Late Miocene in age, and Zone 3 at the top dominated by Retipollenites crotonicolumellatus of Late Miocene to early Pliocene age. These zones are correlated to formal miospore zonations from Colombia and Venezuela, Fenestrites spinosus (12.7-7.1 AM) and partially Cyatheacidites annulatus and Fenestrites longispinousus Zones. The palynoflora assemblages were quantitatively dominated by forest to fresh water swamp species with moderate counts of brackish species. The paleoenvironment varied from fresh water and terrestrial to brackish and finally terrestrial. (*) This contribution is based on results obtained for the ?Agencia Nacional de Hidrocarburos? (ANH), Colombia in the context from 153 de 2012 ANH-Antek contract.