Pragian-Emsian palynomorphs from the Cordobes Formation, Norte Basin, Uruguay: stratigraphically restricted and regionally correlative palynological events in the cool-water Malvinokaffric Realm

Palynological analyses of core samples from Achar E1 well (Norte Basin, Uruguay), yield abundant well-preserved Lower Devonian assemblages. Four new acritarch species (Bimerga acharii, Bimerga nuda, Polyplanifer turbatum and Veryachium woodii) are described. Two of them belong to the Devonian bipolar genus Bimerga Wood 1995, being the oldest representatives of this lineage. Generic diagnosis of Bimerga is emended to fully document species variation. The Devonian recurrence of bipolar symmetry among acritarchs is discussed. New Bimerga species were recorded in the Cordobes Formation, the principal potential hydrocarbon source rock in the basin. These species have biostratigraphic value, confirmed by studies from Argentina, Brazil and Bolivia. All stratigraphic records are from the Gondwanan Malvinokaffric Realm. Associated to Bimerga appear other acritarchs, prasinophycean algae, chitinozoans, and miospores. Miospore assemblage is comparable to those previously described in part of the Ponta Grossa Formation (Parana Basin, Brazil), confirming a late Pragian-early Emsian age span.