Sedimentology and micromorphology of the Lower Palaeolithic lakeshore site Marathousa 1, Megalopolis basin, Greece

The present study describes the sedimentology and formation processes of the archaeological site Marathousa 1, part of a Pleistocene lignite-bearing succession at the Megalopolis basin (Southern Greece). The sedimentary sequence of the site comprises about 4–5 m lacustrine and fluviolacustrine clastic deposits found between Lignite Seam II and III. The lower part of this sequence is characterized by relatively high rate subaqueous sedimentation of bedded sands and silts with local evidence of slumping and liquefaction attributed to a seismic event. This part of the sequence contains fluctuating but generally low organic and carbonate content probably associated with cold and arid conditions of a glacial period. The upper part of the sequence follows a major hiatus attributed to exposure and erosion. A series of erosional bounded depositional units are observed in this sequence suggesting important water-level fluctuations. The subaqueous emplacement of the deposits is attributed to subaerial flood-generated, organic- and carbonate-rich dilute mudflows and hyperconcentrated flows. Organic-rich sedimentation culminates with the formation of the overlying lignite seam. This change is interpreted as a gradual return to warmer and humid conditions of an interglacial period.