A GIS-assisted reconstruction of the Holocene transgressive paleosurface of Pederneira lowland (W Portugal)

The Last Glacial Maximum low stand and coeval re-incision of the Portuguese hydrographic network created the space and defined the shape of the main morphological features available to accommodate the inundation resulting from the Holocene transgression and the marine sediments deposited in tune with changing base levels. The reconstruction of the transgressive paleosurface is relevant in paleoenvironmental studies, namely to establish the paleobasin morphology and evaluate accommodation volume. In the case of the study area, the geological data set available to reconstruct that surface consists of borehole logs carried out for geotechnics and groundwater and three cores performed for paleoenvironmental reconstruction. The borehole data scatter non-uniformly across the lowland providing spatially biased information. The surveying of several Transient Electromagnetic Method profiles yielded inconclusive results in separating sediment units below and above the transgressive surface, due to poor contrast in sediment resistivity and high conductivity of groundwater. This study addresses a method for estimating that paleosurface using the combination of a standard geostatistical interpolation procedure with a conceptual geomorphological model.