Biostratigraphy and biogeography of charophytes from the Cerro Barcino Formation (upper Aptian–lower Albian), Cañadón Asfalto Basin, central Patagonia, Argentina

Abstract

Charophytes from the lower Cerro Barcino Formation, Chubut Group, at Paso de Indios, Cañadón Asfalto Basin, include Sphaerochara verticillata, Mesochara symmetrica, Lamprothamnium? barcinencis sp. nov., Clavator harrisii harrisii, C. harrisii zavialensis and Clavatoraxis sp. The charophytes recovered from the basal members of the unit indicate deposition within the upper Aptian–lower Albian stratigraphic interval, as compared with the European charophyte biozonation. This attribution is based on the biostratigraphic significance of the evolutionary species Clavator harrisii that shows the dominance of C. harrisii harrisii in all levels studied and the appearance of C. harrisii zavialensis in the Cerro Castaño Member of the Cerro Barcino Formation. The known distribution of Clavator harrisii in other floras from North and South America, Europe, Asia and Northern Africa provides evidence that it was still a cosmopolitan species in the early Albian and did not show any population fragmentation, in contrast to other coeval cosmopolitan clavatoraceans.