Karst depressions as geoarchaeological archives: The palaeoenvironmental reconstruction of Zominthos (Central Crete), based on geophysical prospection, sedimentological investigations and GIS

Abstract

Sediment-filled karst depressions (e.g. dolines) have rarely been used as geoarchives in Greece due to an uncertainty about the thickness of accumulations and their vague suitability for palaeoenvironmental research. However, such terrestrial proxy-data sources can yield important records for the analysis of the Holocene landscape history. A multi-method approach was applied in order to evaluate the potential of colluvial fillings for reconstructing the geoarchaeological landscape in Mount Ida, Central Crete. Subsequent to an area-wide survey of appropriate karst hollows through remote sensing and GIS analyses, geophysical prospection (refraction seismics, earth resistivity tomography) was conducted at the most promising archive locations. Selective percussion drilling within the sinkholes provided vibra-cores for mineralogical and sedimentological investigations (grain size distribution, heavy- and light minerals, X-ray diffraction, thin sections) as well as AMS 14C dates. As demonstrated by the results, the dolines are partially filled by loose material up to 20 m b.s. and, thus, offer valuable information about the environmental history. The diversified sediment constitution indicates several geomorphodynamic oscillations and a polygenetic nature of the colluvial fills. XRD-spectra of clay minerals and quartz-grain morphology both indicate a significant aeolian dust contribution to soil formation and pedo-sediments. Glass shards and substantially heterogeneous heavy mineral compositions point to supra-regional origin and external volcanogenic deposits (Minoan eruption of Santorini, 3.6 ka). Regarding the hitherto discussed distribution of Z2 tephra in the Mediterranean, the spatial fallout must be revised as great amounts have also been deposited in the high mountains of Crete. Moreover, the redeposition of the sedimentary fills proves to be comparatively young since most materials were accumulated within the dolines post-eruptively. Huge and previously unknown subsurface archaeological remains strongly suggest that year-around settlement in the mid-Holocene might have been possible under better climatic conditions. The results imply that karst depressions serve as suitable geoarchives, particularly when investigated within a multi-method approach.