POLLEN AND SPORES OF THE GLEN ROSE FORMATION (EARLY ALBIAN, TEXAS) AND THEIR IMPLICATIONS FOR CORRELATION OF OTHER SEQUENCES

Although the palynoflora of the middle Albian part of the Fredericksburg Group in southern Oklahoma has been described in detail, the pollen and spores of the underlying Glen Rose Formation are poorly known. Because this unit is well dated by ammonites, it has potential as an important reference point for correlation of continental sequences such as the Potomac Group and for dating events in the radiation and dispersal of angiosperms. Samples from Barker Branch and Cedar Brake Camp on the Paluxy River in Somervell County, which can be assigned to the late early Albian mammillatum zone, are dominated by Classopollis and Exesipollenites, but angiosperm pollen is the next most common terrestrial element, and there are several index spore species for Zone II in the Potomac Group. Among the angiosperms, monosulcates of the Clavatipollenites and Retimonocolpites types are most common and diverse, but several tricolpate species are also present. Stratigraphically important angiosperms include the Clavatipollenites rotundus group (Retimonocolpites dividuus of many authors) and reticulate tricolpates, which are similar or identical to types that appear in upper Zone I of the Potomac Group and in the marine earliest Albian of England and Portugal. However, there are also tricolpates with striate-reticulate sculpture, a pollen type that is not known from upper Zone I but appears in the later early Albian of Portugal. This assemblage contrasts with floras from Potomac Zone II and the lower Fredericksburg Group of Oklahoma, where tricolpates had become much more diverse than monosulcate angiosperms. These results confirm arguments based on the well-dated Portuguese section that there is a significant hiatus between Zones I and II in the Potomac, and that this gap includes the later part of the early Albian. The dominance of Classopollis and Exesipollenites and the occurrence of isolated Gondwanan elements such as Sergipea and Tucanopollis may mean that Texas lay in a transition zone between Southern Laurasia and the hotter and drier Northern Gondwana province, but it is difficult to disentangle geographic and climatic effects from effects of the lagoonal local environment.