Landscapes and Landforms of Italy by Mauro Soldati & Mauro Marchetti

Author:Mauro Soldati & Mauro Marchetti
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

21.3 Landforms and Landscapes

Coastal Pliocene sediments are locally preserved on top of the mountain ridges and within sedimentary basins. At depth, inside the basins, sediments testify to a slightly deeper depositional environment. On top of the ridges, these sediments have locally a very limited thickness and most probably in the past they covered a larger area. Marine conditions characterized the area until the Middle Pliocene. No faults displace the planation surface along the margins of the basins, clearly indicating that the depressions are the result of selective erosion (Coltorti et al. 2012). After the emersion of the area, the hydrographic network easily deepened through the basins due to the presence of the erodible Mio-Plio-Pleistocene sediments (Fig. 21.3). Only the Florence—Upper Valdarno—Valdichiana basins are fault-angle valleys and the river flows parallel to the normal fault system located to the west of the Tosco-Emilian Apennine ridge. In the Florence basin, the Arno River abruptly changes direction to the WSW cutting the Mt. Albano ridge and flowing straight to the sea. The Chiana River runs for a short distance parallel to the same fault system, but it mostly crosses slantwise the Valdichiana basin before joining the Tiber River. Also the upper valley of the Ombrone River deepens in correspondence with the softer terrains of the Siena-Radicofani basin before turning abruptly to SW to cut the Inner Tuscany Ridges down to the coast. All the major rivers deepen within the Mio-Pliocene sediments. However, some anomalies in the river pathways are recognizable across the area. In fact, in the inner western reaches many rivers (i.e. Merse River) flow to the east and make a long turn before going west towards the Tyrrhenian Sea.

Fig. 21.3Topographic cross sections across central-southern Tuscany showing the main basins and ridges. Location of profiles in Fig. 21.1. In Sections 1–3 the master, west dipping normal fault bounding to the west the Tosco-Emilian Apennines, is shown

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