The main aspects related with the geological mapping of the Cenozoic units of the “Lisbon Metropolitan Area” (AML) are presented. The mapped area makes part of the “Lower Tagus Basin” which extends from the littoral western part of the Setúbal Peninsula and crosses the Portugal/Spain border in the Castelo Branco region. The basin was differentiated during the Eocene and evolved up to the present. The mapped unities are integrated in the evolution of the basin and reflect the different infill stages under different sedimentary contexts. Taking into account the relations between the sediments infill and their genetic environments, the basin can be subdivided in 3 sectors: the distal one, with alternating marine and continental deposits in the Lisboa area and always marine in most of the Setúbal Peninsula; the middle sector with continental environments and some brackish episodes during high sea levels; and the proximal sector with exclusively continental sedimentation. In the distal sector, high-resolution stratigraphy could be achieved for the Neogene deposits; fifteen lithostratigraphic units have been characterized for the Lisboa region, twelve for the Almada area and eight for the remaining Setúbal Peninsula region. In the middle sector, that occupies great part of Ribatejo and Alto Alentejo provinces, it was possible to characterize just five units for the same time interval. In some areas, a number of units were merged due to their lithological similarity. The AML project allowed to normalize and homogenize the mapped lithostratigraphic units and to establish some correlations between them. These facts are reflected in the presentation of general maps from which the 1/100 000 scale map is an example. The lithostratigraphic units and symbols are also presented as well as the old units used in the geological maps at the 1/50 000 scale.
Palavras-chave: Geological mapping; Cenozoic; Lower Tagus Basin; Área Metropolitana de Lisboa; Portugal.
|Publication status||Published - 1 Jan 2009|