The geology of the Camerano area through the reconstruction of sedimentary sequences of the urban caves

Abstract

The historical Camerano town (Ancona, Central Italy), built on the top of a hill at the rear of the Conero Mt. promontory, holds a broad underground system of remarkable man-drilled caves. Contrary to the roughly total lack of subaerial accessible outcrops, the caves allow to reconstruct the geological evolution and to describe a composite sedimentological and stratigraphic section into Early Pleistocene (Calabrian) marine deposits. The present study is aimed to a better definition of the sedimentological and palaeoenvironmental context for the Camerano area, and also improves the knowledge of the Camerano caves. Sediments are mainly regarded as massive to laminated yellow-brown bioclastic sand and massive grey-green clay couplets, variable in thickness, each couplet showing erosive basal surface and normal gradation, from sand to clay. Plane-parallel lamination, marked by recurring variations in grain size, is referred to “traction carpets”, and the sand horizons are described as carbonatic turbidites with eastern supply (Conero Mt.). Conversely, clay reflects both western river deltas distal supply and local contribution from marine productivity. Along the section, matrix-supported gravel beds also occur made of heterometric clay fragments dispersed into a bioclastic sandy matrix. Described facies only partially insert in the former geological schemes, and offer new insights to the palaeoenvironmental restoration for the Camerano area, which involves a tectonically active Early Pleistocene basin, mainly dominated by clay sedimentation, periodically reached by storm- to seismic-induced carbonatic turbidites. The large clay fragments, matrix-supported gravels probably derive from remobilization of partially lithified deposits along the basin’s flank and represent the distal evolution of west- coming slumps.