Sprecher
Beschreibung
The Lusitanian Basin, Portugal has long been an area of focus for studying the diversification of angiosperms in the Early Cretaceous. Coastal outcrop sections from Ericeira have been stratigraphically well-constrained using updated strontium isotope stratigraphy and are thus useful for examining the very early incursions of angiosperms into a gymnosperm dominated habitat. This study examines palynofloral assemblages sampled from nearshore limestones and clastic sediments with the aim of reconstructing the floras, climate and environment in which the early angiosperms began to proliferate.
Palynofloral evidence is indicative of a warm, potentially dry climate dominated by xerophytic gymnosperms. High abundances of Classopollis pollen derived from cheirolepidiacian conifers are observed throughout the section. High abundances of Exesipollenites are observed in the lower half of the section (uppermost Valangian to mid-Hauterivian) but decrease to near absence in the upper half (upper Hauterivian to upper Barremian) as bisaccate pollen derived from pinaceans (Pinuspollenites) becomes more abundant. Isolated finds of monosulcate angiosperm pollen grains (Clavatipollenites, Asteropollis) are observed in the upper part of the section (Barremian). Spores derived from ferns (Cyathidites, Deltoidospora, Cicatricosisporites) and lycopsids (Patellasporites) are indicative of coastal marshes and locally wet conditions, and are found in higher abundances in the more proximal, sand-dominated facies at the base and top of the section. Changes in the spore abundances appear driven mainly by sea-level and transport, whereas shifts in the pollen assemblage appear partially climate-driven.