Análisis palinológico de niveles ricos en materia orgánica del Jurásico Superior de Almansa (Albacete, España)

Résumé

[Palynological analysis of three Upper Jurassic organic matter levels from Almansa (Albacete, Spain)]. In a limestone quarry exploited for construction materials in the region of Almansa (Albacete), three levels of black marls were found. A palynological analysis has provided rich spore-pollen assemblages along with some macroflora remains. The age of the limestones was determined according to their benthic foraminifera and Dasycladaceae contents, corresponding to the Alveosepta jaccardi biozone, an age that spans the upper Kimmeridgian and may reach the base of the Tithonian. Geologically the quarry occurs at the border between the Prebetic and Iberian Domains and palaeogeographically it lies within the sedimentary Domain of Albacete. The three levels examined palynologically reveal 91 taxa, of which 56 correspond to spores, mostly from pteridophytes, 27 to gymnosperm pollen grains with predominance of conifer and the rest to aquatic organisms. The two lower levels (N-1 and N-2) provide similar assemblages, although level N-1 shows greater palynological diversity. In both levels, ferns and conifers predominate although N-2 lacks aquatic palynomorphs and pollen grains are more abundant than spores. Level N-3 exhibits poor diversity and is characteri- zed by the almost exclusive presence of gymnosperms along with dinophytes and prasinophytes. Our analysis of palynological data reveals the ecological and environmental features of the sequential evolution of the area. Sedimentation took place on the inner part of a carbonate ramp very close to the coast that sustained conifer woods on the nearby continent in a prograding succession. An abrupt increase in the marine content of the last sequence coincides with the arrival of terrigenous deposits.