I depositi di versante del Monte dell’Ascensione (Marche meridionali, Italia)

The slope deposits of the Ascensione Mount (Southern Marche, Italy)

Abstract

The present paper reports about the first results of detailed geomorphological study, carried out with the contribution of sedimentary analyses and radiocarbon dating, of the Ascensione Mount (1100 m a.s.l., the highest relief of the southern Marche highland) slope deposits and its related morphological factors. These are very noticeable both for extension (about 10 km2) and thickness (about 30 m as average), and for their rarity on outer Apennines ridge areas. The investigated mountain is formed by a mainly conglomeratic body, interposed in pelitic sediments (middle-upper Pliocene), trasgressive on the underlying Messinian turbidites (Laga Formation). The settlement of pre-trasgressive bedrock took place from Tortonian to Lower Pliocene, caused by a compressive tectonics associated to the arch-foredeep system migration from the Tyrrhenian to Adriatic sea; while the rising- out and the regular monoclinalic disposition of post-transgressive sediments is associated to the generalized Pleistocene uplift. The study allowed us to reconstruct the original extension of detritic deposits, to determinate their sedimentological features and to recognise two generations of them at different heights (between 750 and 850 m the first and between 550 and 800 m the second one). The sedimentation of the latter belong to Upper Pleistocene (between 41640 yr ± 1260 B.P. and 22680 yr ± 170 B.P., Beta Inc.), while the older one, basing on geomorphological features, has been attributed to Middle Pleistocene. Besides, with correlation between relict limbs, three main pediments, located on different altitudes (950-1000 m, 750-850 m, 400-600 m), are individualised on the relief sides; their chronological attribution is still to be carried out.