Geological sheet Fossombrone

Update: 11/03/2011

Sheet 280 "Fossombrone" at 1:50,000 scale

 

The sheet 280 Fossombrone of the Geological Map of Italy at 1:50,000 scale is being realized for printing by the Geological Survey of Italy - Department of Soil Protection.
The researches are divided into the field survey and the analysis, interpretation and processing of the collected geological data and samples. The geological sheet is comprehensive of the database digitized at 1:25,000 scale starting from the 1:10,000 scale geological data set.
The explanatory notes, in addition to the traditional topics related to the geological characteristic of the area, contain the items most closely related to practical and environmental aspects.

The sheet is divided into geologically distinct areas:

• a south-western area, mainly with carbonate sediments belonging to the Umbria-Marche succession, structured into the Monte Paganuccio-Monte Pietralata and Monti della Cesana anticlinals; these are locally bordered by thrust faults NE verging and by backthrusting systems. The oldest lithostratigraphic term, cropping out at the core of the Monte Paganuccio-Monte Pietralata anticline, is the Calcare Massiccio Formation;
• a north-eastern sector, at the edge of the carbonate structures, characterized by turbidite and evaporite Cenozoic sequences belonging to the Marchean foredeep;
• an eastern sector composed by Plio-Pleistocene marine successions.

Moreover, alluvial deposits are also widely distributed, arranged in various orders of terraces, with outcrops trending SW-NE along the Metauro and Cesano rivers’ valleys.

The sheet 280 Fossombrone area is located in the external sector of the Northern Apennines and is characterized by a chronostratigraphic interval (from Triassic to Recent) recorded in its sedimentary lithotypes and by a tectonic evolution of its basins that constitute a complete orogenic cycle.

The area lies entirely in the Marche region, in the Pesaro-Urbino and Ancona provinces. It affects the middle valley of the Metauro River and includes the Monte Pietralata-Monte Paganuccio and Monti delle Cesane ridges, the Montecalvo in Foglia-Isola del Piano basin, the Colbordolo-Fontecorniale ridge and the Cartoceto-Serrungarina basin. The oldest outcropping lithostratigraphic unit is the Calcare Massiccio Formation (Lower Jurassic) that is detached from the underlying Anidriti di Burano formation deposited during the Triassic on the Hercynian basement.

The deposition environment of carbonate platform and the Permian-Triassic extensional structures indicate that the area was affected by an extensional tectonic related to the structuring of the Tethys ocean.

The subsequent identification and evolution of the passive margin is recorded in the carbonatic Mesozoic-Eocene multilayer. In the Upper Cretaceous-Oligocene interval, represented on the field by the Scaglia Bianca, Scaglia Rossa, scaglia variegata and Scaglia Cinerea formations, becomes significant the contribution of the terrigenous component as an index of a compressive system that will lead to the detect of the Apennine Neogene foredeep. The advance of the deformation from the inner to the outer zone causes the development of a complex system of foredeep migrant to north east with associated lower basins (thrust-top basins).

The syntectonic deposition gives rise to a characteristic lithostratigraphic succession with development of differentiated facies in the Neogene basins, where pelagic and emipelagic foreland sediments (Bisciaro and Schlier Formations) are followed by the foredeep turbiditic sediments of Alpine provenance (Marnoso-Arenacea Formation). Then follow the deposits of the regressive phase of the Middle-Upper Messinian represented by evaporitic and lago-mare deposits (Gessoso-Solfifera and Colombacci Formation). The succession ends with the Plio-Pleistocene transgressive sediments before the final emersion of the area. The Quaternary continental sedimentation is represented by fluvial and slope deposits, and the altimetrically high position of the deposits and terraced morphologies suggest uplifts and a recent tectonic.

In addition, some structural evidences suggest that different sectors are currently involved by stretching. The field geological survey performed at 1:10,000 scale, along with data from deep wells and seismic reflection, allowed to define the structural style of the area. In particular, in the outer surfaces where the succession of Neogene foredeep outcrop, this style is characterized by the development of pairs of anticlines and synclines folds cutted by thrust faults and backthrust (pop-up structures). Moreover, the presence of many levels of detachment within the whole succession gives rise to a differentiation between structural styles among basement, carbonate multilayer and foredeep sequences.