Plant taphonomy and palaeoecology in the lacustrine Uña delta (Late Barremian, Iberian Ranges, Spain)

Abstract

Plant cuticle compressions and sporomorphs were studied in coaly clays belonging to the Upper Barremian La Huérguina Formation in Uña (South-western Iberian Ranges, Cuenca, Spain). Cuticle assemblages are extremely monotonous and formed by the genera Frenelopsis Schenk emend.Watson, Classostrobus Alvin et al. and Glenrosa Watson and Fisher. Sporomorphs are dominated by Classopollis Pflug emend. Srivastava. The genus Glenrosa is described for the first time in Europe. Sedimentological and taphonomical analyses show that these assemblages originated by fragmentation and size-selection during residence in the leaf-litter and by fluvial transport. Final deposition occurred in crevasse-splay, deltaic front and pro-deltaic environments. Our results indicate that the Uña delta was fed almost exclusively by remains of cheirolepidiaceous conifers living in the upper deltaic plain of a lacustrine delta. A comparison with the flora found in the open lacustrine facies of Las Hoyas, which is laterally equivalent of the beds studied, shows that land–plant assemblages of Las Hoyas are more diverse. The parautochthonous matoniaceous tree-fern Weichselia reticulata dominated the lakeshore vegetation of Las Hoyas in contrast to the vegetation of the upper delta plain of Uña, which was dominated by Frenelopsis. The habitats of Frenelopsis and Glenrosa from the Upper Barremian oligohaline basin of Uña–Las Hoyas contrast with the habitats commonly hypothesized for both taxa in coastal marine environments or on saline edaphic profiles. In conclusion Frenelopsis appears to have a wider tolerance to salinities than previously thought and their adaptations to saline edaphic conditions should be considered species-specific rather than genus-specific.