Upper Pleistocene-Holocene vegetation changes in Navalmaillo Rockshelter (Pinilla del Valle, Madrid, Spain)

Abstract

Navalmaillo Rockshelter pollen data are presented, in order to know de vegetation and climate changes during Upper Pleistocene (levels: NVP-fluvial, NVP-H, NVP-F and levels ß, α), dated in 71.685±5.082 - 77.230±6.016), and Holocene (NVH), formed previously 3690±60 BP (4.170- 3.860 cal BP) (Fig.1). The site is located at 1.114 mns, in the center of the high Lozoya valley; was formed by fluvial action (Lontanares and Navalmaillo, tributarios of Lozoya river) that eroded Late Cretaceous dolomite outcrops. Vegetation point of view (Peinado Lorca y Rivas Martínez, 1987), the area is located in Guadarramense section, Supramediterraneo bioclimatic level, in Luzulo forsteri-Querceto pyrenaicae range (Fernández, 1988) with deciduous forest (Quercus pyrenaica) development under supramediterraneae climate, subhumid continental. The pollen extraction followed the standard established protocols (acids and alkalis). The residuals were pollenenriched through flotation in the Thoulet’s dense liquor being later preserved in glycerin in eppendorf tubes. The of pollen grains in the samples oscillates between 300 pollen grain number; when de number was low (10-20) that they are figured in the pollen diagram as “presences”. The statistics was made using TILIA® and TILIA GRAPH®. In the samples with statistically significant number of pollen grains the AP/NAP logs were built as well as the rarefaction analysis, to determine the vegetation diversity. In order to make easier the data reading a synthetic pollinic diagram has been built including the most significant taxa (Fig.2). Pollen data show a vegetation, from Pleistocene formed under climate conditions dry Mediterranean (NVP-river), which pass through a phase with a more moderate climate, with variations in the rate of moisture (NVP-H); progressively are installed more dry conditions (NVP-F) ending in other more severe and with lower temperatures (ß levels and α). During the Holocene, the trend observed, within a Mediterranean climate, is toward the installation of conditions with increasing water scarcity, which define the progressive increase of excellence in the study area. The development of nitrophilous taxa and of the NPM coprofila affinity, show the existence of fauna in the territory, which alter the conditions food webs of the east. The relationship between AP and the NPM type 207 (cf. Glomus fasciculatum) curves, show the processes of deforestation of the territory, wicht favoring the reactivation of the erosive processes (Concentricistes or Pseudoeschizaea circula), especially on the basis of the 860 BP (910-690 cal BP). Six-phase have been detected as a response to climate change, which, in general, express the transit towards the installation of cooler conditions during the upper Pleistocene. During the Holocene, the vegetation is defining the Mediterranean increased in the study area (Fig.2).