The Colle Curti mammal site in the Colfiorito area (Umbria-Marchean Apennine, Italy): Geomorphology, stratigraphy, paleomagnetism and palynology

An approximately 90 m thick sequence has been studied in the Colle Curti basin (Colfiorito area, Umbria-Marchean Apennine).It was deposited in a drainage system characterized by a 'mature' landscape without a clear watershed separating the Adriatic and Tyrrhenian sides. Close to the end of the Early Pleistocene this landscape was dismembered by the activation of extensional faults, linked to an uplifting of the chain that reached its greatest magnitude at the beginning of the Middle Pleistocene. From a sedimentological point of view the sequence can be roughly divided into three parts, with gravel deposition in a braidplain environment dominating the lower and upper parts, and a phase of clay deposition in a lacustrine environment separating these. An Ar/Ar analysis on the sanidine contained in a vertisol in the upper part of the sequence gave an age not older than 427 ka. An early Galerian fauna was collected in clay layers where the Jaramillo palaeomagnetic event was recognized. Cold periods are documented in the lower and upper part of the sequence, although in the latter the intense weathering caused by the development of a soil with tropical features precludes further investigations. The palynological data supported by sedimentological and palaeomagnetic evidence indicate that the sequence can be related to a large part of the Bavelian and part of the Menapian. In the middle part, where clay layers outcrop, two cool and humid phases are followed by colder and drier periods. Biological and geological evidence suggests that around 1 My the basin of Colle Curti was probably located at an elevation of about 600 m. (C) 1998 INQUA/Elsevier Science Ltd. All rights reserved.