A new palynoflora from upper Barremian-lower Aptian rocks at Casal do Borracho, Torres Vedras, western Portugal, and its palaeoecological significance

Palynofloras provide many clues about the composition of past terrestrial vegetation and the conditions in which the plants lived. Here we describe a new Early Cretaceous palynoflora from the western Portuguese Basin in the Estremadura region. A palynomorph assemblage of 34 genera and 55 species was extracted from samples collected from the site of Casal do Borracho in the municipality of Torres Vedras. The rocks concerned belong to the Almargem Formation, which is considered to be of late Barremian to early Aptian age. The beds sampled are dominated by kaolinite, illite or smectite. Of the 22 samples processed for palynological analysis, only five from beds of varying clay mineral composition proved to be productive. The assemblages recovered are dominated by representatives of the fern family Anemiaceae, mainly the spore genera Appendicisporites, Cicatricosisporites, Costatoperforosporites and Klukisporites. Zygospores of Zygnemataceae occur in association. There are also numerous bisaccate and cheirolepidiaceous conifer pollen. Angiosperm pollen grains are scarce and represented by the genera Clavatipollenites, Mayoa and Pennipollis. Overall, the palynoflora of Casal do Borracho suggests a locally wet environment in a tropical/subtropical climate, with much of the gymnospermous component indicating more arid conditions not far away at the time of deposition, an interpretation that is supported by data on the clay mineral assemblages recovered from the succession.