SOIL-LANDFORM RELATIONSHIPS OF COASTAL ESTREMADURA, PORTUGAL

Soils in surface and buried contexts in Estremadura, Portugal, provide evidence of landscape stability and instability, relative age relationships between landforms and general paleoenvironmental conditions during the late Quaternary. These factors provide insight into the likely distribution and condition of Paleolithic sites and therefore guide ongoing archaeological survey. Late Pleistocene and Holocene dunes extend inland approximately 10 km from coastal source regions. Surface soils in Holocene dunes under maritime pine forest exhibit A, E, C/Bh and A, C horizon sequences and classify as Quartzipsamments. Surface soils in late Pleistocene dunes exhibit A, E, Bh, Bhs, Bs horizon sequences and classify as Haplorthods. Both Pleistocene and Holocene dunes commonly bury a heavily weathered soil formed in calcareous sandstone. The boundary between underlying buried soils and overlying surface soils is characterized by a lag deposit of medium to coarse, moderately-rounded gravels, underlain immediately by subsurface Bt and Bss horizons. The lag deposit and absence of buried A horizons both indicate intense and/or prolonged surface erosion prior to burial by late Quaternary dunes. Soil-geomorphic relationships therefore suggest at least two distinct episodes of dune emplacement and subsequent landscape stability following an extensive episode late Pleistocene landscape instability and soil erosion. Other archaeologically important soil-geomorphic settings in the study region include a late Pleistocene fluvial complex with Xeralfs and Orthods, and an uplifted coastal complex with Psamments and Orthents. Each of these soil-geomorphic contexts is associated with unique preservation potential issues. We have identified archaeological sites in each of these settings but the likelihood of identifying future sites is related to taphonomic factors that depend in part on geomorphic processes. The research demonstrates that coastal middle- and upper-Paleolithic archaeological localities exist along western Iberia and that their geographic distribution and likelihood of future identification are geomorphically stratified.