The application of mineral magnetic and extractable iron (Fe d) analysis for differentiating and relatively dating fan surfaces in central Greece

Abstract

Mineral magnetic and extractable iron analyses of Bt-horizons of fan surface soils were undertaken in order to differentiate and rank by order of formation discrete fan surfaces within a debris-flow/fluvial fan in the Tithorea Basin, central Greece. Detailed topographic surveying initially suggested a simple fan surface morphology which consists of a steep proximal surface and a gently sloping but extensive distal surface. In contrast, mineral magnetic and extractable iron data suggest a more complex fan surface morphology which comprises a steep proximal surface, less steep upper and lower medial surfaces, and a gently sloping distal surface. The mineral magnetic and extractable iron data indicate that soils of the upper fan surface contain the highest concentration of ferrimagnetic and anti-ferromagnetic minerals while soils developed on successively lower surfaces are characterised by a progressively lower concentration of both types of magnetic mineral. The trend in magnetic mineral concentration suggests that the upper surface formed first, followed by the upper and lower medial surfaces, and finally the distal surface. Therefore, fan surfaces become progressively younger the greater the distance from the fan apex. Translating this trend in terms of the likely pattern of fan development, during the late(?) Pleistocene, deposition initially occurred at the range front to form the upper fan surface. Subsequent depositional events throughout the Holocene coincided with incision of the fan-head and a progressive shift of the locus of deposition towards the interior of the Tithorea basin, forming the medial and distal fan surfaces in the process.