The geology of Monte Cetona

The Montagna di Cetona is located south of the province of Siena, on the borders with Umbria and Lazio. 1,148 m above sea level, it separates the Siena – Radicofani basin from that of the Val di Chiana. It is the most extreme outcrop of the Mesozoic lands of the northern Apennines, which belong to the Tuscan Series. On its eastern side (Camporsevoli area, Podere Cancelli…), the Tuscan stratigraphic series emerges in an inverted sequence: the most recent lands are beneath the most ancient ones. Monte Cetona is the inverted side of a lying fold, whose straight side has been removed by erosion. Composed mainly of calcareous rocks, it is surrounded by sandy Pliocene deposits and conglomerates of marine origin.

Its history began 225 million years ago, in the Mesozoic Era, when deposits of dark grey cavernous limestone began. The environment was coastal, with lagoons with shallow waters and high evaporation (hot humid climate).

215 million years ago saw deposits of a limestone rich in Avicula Contorta, a small bivalve mollusc, found in shallow sea with little movement.

210 million years ago, platforms similar to the current coral formations of the Bahamas, with massive limestone deposits, started to develop.

Subsequently, in a deeper and more open sea, selciferous limestone was deposited, characterised by grey flint rich in ammonites (molluscs with spiral shells, interesting as guide fossils) and marl with Posydomia Alpina.

Around 160 million years ago the sea reached its maximum depth of over 3,000 m. Here only the siliceous shells of the Radiolari are preserved, which give rise to red or green jasper.

The formation of majolica dates back 145 million years, consisting of whitish limestone with light flint followed by polychrome schists (greenish and red-wine-coloured stratified clays).

Starting 30 million years ago, the great accumulation of material deriving from the erosion of granite from the Alps caused an abrupt change of sedimentation in the sea, leading to the formation of macigno, a coarse sandstone with an ochre brown colour.

The rising of the Apennines 10 million years ago caused tectonic movements that interrupted sedimentation.

In the Pliocene, 3 million years ago, Monte Cetona was one of the islands of the Tuscan archipelago. The shallow coastal area, due to the large accumulation of earth sediments, was transformed into many brackish lakes. This is shown by the Belverde clays rich in molluscs of fresh and brackish water.

In the Quaternary, 2 million years ago, the water surrounding Mount Cetona gradually receded. Continental sediments accumulated on marine sediments. In the same period when a large swamp formed in the valley, extensive plates of travertine, a stratified and porous whitish rock, appeared on the eastern side. Its formation was due to the precipitation of calcium carbonate in waters rich in it, in the presence of hot thermal springs, waterfalls or drips. Analysis of impressions left in the travertine have shown the presence of holm oak, laurel and boxwood, which point to a warmer and wetter climate than the current one.The Montagna di Cetona is located south of the province of Siena, on the borders with Umbria and Lazio. 1,148 m above sea level, it separates the Siena – Radicofani basin from that of the Val di Chiana. It is the most extreme outcrop of the Mesozoic lands of the northern Apennines, which belong to the Tuscan Series. On its eastern side (Camporsevoli area, Podere Cancelli…), the Tuscan stratigraphic series emerges in an inverted sequence: the most recent lands are beneath the most ancient ones. Monte Cetona is the inverted side of a lying fold, whose straight side has been removed by erosion. Composed mainly of calcareous rocks, it is surrounded by sandy Pliocene deposits and conglomerates of marine origin.

Its history began 225 million years ago, in the Mesozoic Era, when deposits of dark grey cavernous limestone began. The environment was coastal, with lagoons with shallow waters and high evaporation (hot humid climate).

215 million years ago saw deposits of a limestone rich in Avicula Contorta, a small bivalve mollusc, found in shallow sea with little movement.

210 million years ago, platforms similar to the current coral formations of the Bahamas, with massive limestone deposits, started to develop.

Subsequently, in a deeper and more open sea, selciferous limestone was deposited, characterised by grey flint rich in ammonites (molluscs with spiral shells, interesting as guide fossils) and marl with Posydomia Alpina.

Around 160 million years ago the sea reached its maximum depth of over 3,000 m. Here only the siliceous shells of the Radiolari are preserved, which give rise to red or green jasper.

The formation of majolica dates back 145 million years, consisting of whitish limestone with light flint followed by polychrome schists (greenish and red-wine-coloured stratified clays).

Starting 30 million years ago, the great accumulation of material deriving from the erosion of granite from the Alps caused an abrupt change of sedimentation in the sea, leading to the formation of macigno, a coarse sandstone with an ochre brown colour.

The rising of the Apennines 10 million years ago caused tectonic movements that interrupted sedimentation.

In the Pliocene, 3 million years ago, Monte Cetona was one of the islands of the Tuscan archipelago. The shallow coastal area, due to the large accumulation of earth sediments, was transformed into many brackish lakes. This is shown by the Belverde clays rich in molluscs of fresh and brackish water.

In the Quaternary, 2 million years ago, the water surrounding Mount Cetona gradually receded. Continental sediments accumulated on marine sediments. In the same period when a large swamp formed in the valley, extensive plates of travertine, a stratified and porous whitish rock, appeared on the eastern side. Its formation was due to the precipitation of calcium carbonate in waters rich in it, in the presence of hot thermal springs, waterfalls or drips. Analysis of impressions left in the travertine have shown the presence of holm oak, laurel and boxwood, which point to a warmer and wetter climate than the current one.The Montagna di Cetona is located south of the province of Siena, on the borders with Umbria and Lazio. 1,148 m above sea level, it separates the Siena – Radicofani basin from that of the Val di Chiana. It is the most extreme outcrop of the Mesozoic lands of the northern Apennines, which belong to the Tuscan Series. On its eastern side (Camporsevoli area, Podere Cancelli…), the Tuscan stratigraphic series emerges in an inverted sequence: the most recent lands are beneath the most ancient ones. Monte Cetona is the inverted side of a lying fold, whose straight side has been removed by erosion. Composed mainly of calcareous rocks, it is surrounded by sandy Pliocene deposits and conglomerates of marine origin.

Its history began 225 million years ago, in the Mesozoic Era, when deposits of dark grey cavernous limestone began. The environment was coastal, with lagoons with shallow waters and high evaporation (hot humid climate).

215 million years ago saw deposits of a limestone rich in Avicula Contorta, a small bivalve mollusc, found in shallow sea with little movement.

210 million years ago, platforms similar to the current coral formations of the Bahamas, with massive limestone deposits, started to develop.

Subsequently, in a deeper and more open sea, selciferous limestone was deposited, characterised by grey flint rich in ammonites (molluscs with spiral shells, interesting as guide fossils) and marl with Posydomia Alpina.

Around 160 million years ago the sea reached its maximum depth of over 3,000 m. Here only the siliceous shells of the Radiolari are preserved, which give rise to red or green jasper.

The formation of majolica dates back 145 million years, consisting of whitish limestone with light flint followed by polychrome schists (greenish and red-wine-coloured stratified clays).

Starting 30 million years ago, the great accumulation of material deriving from the erosion of granite from the Alps caused an abrupt change of sedimentation in the sea, leading to the formation of macigno, a coarse sandstone with an ochre brown colour.

The rising of the Apennines 10 million years ago caused tectonic movements that interrupted sedimentation.

In the Pliocene, 3 million years ago, Monte Cetona was one of the islands of the Tuscan archipelago. The shallow coastal area, due to the large accumulation of earth sediments, was transformed into many brackish lakes. This is shown by the Belverde clays rich in molluscs of fresh and brackish water.

In the Quaternary, 2 million years ago, the water surrounding Mount Cetona gradually receded. Continental sediments accumulated on marine sediments. In the same period when a large swamp formed in the valley, extensive plates of travertine, a stratified and porous whitish rock, appeared on the eastern side. Its formation was due to the precipitation of calcium carbonate in waters rich in it, in the presence of hot thermal springs, waterfalls or drips. Analysis of impressions left in the travertine have shown the presence of holm oak, laurel and boxwood, which point to a warmer and wetter climate than the current one.The Montagna di Cetona is located south of the province of Siena, on the borders with Umbria and Lazio. 1,148 m above sea level, it separates the Siena – Radicofani basin from that of the Val di Chiana. It is the most extreme outcrop of the Mesozoic lands of the northern Apennines, which belong to the Tuscan Series. On its eastern side (Camporsevoli area, Podere Cancelli…), the Tuscan stratigraphic series emerges in an inverted sequence: the most recent lands are beneath the most ancient ones. Monte Cetona is the inverted side of a lying fold, whose straight side has been removed by erosion. Composed mainly of calcareous rocks, it is surrounded by sandy Pliocene deposits and conglomerates of marine origin.

Its history began 225 million years ago, in the Mesozoic Era, when deposits of dark grey cavernous limestone began. The environment was coastal, with lagoons with shallow waters and high evaporation (hot humid climate).

215 million years ago saw deposits of a limestone rich in Avicula Contorta, a small bivalve mollusc, found in shallow sea with little movement.

210 million years ago, platforms similar to the current coral formations of the Bahamas, with massive limestone deposits, started to develop.

Subsequently, in a deeper and more open sea, selciferous limestone was deposited, characterised by grey flint rich in ammonites (molluscs with spiral shells, interesting as guide fossils) and marl with Posydomia Alpina.

Around 160 million years ago the sea reached its maximum depth of over 3,000 m. Here only the siliceous shells of the Radiolari are preserved, which give rise to red or green jasper.

The formation of majolica dates back 145 million years, consisting of whitish limestone with light flint followed by polychrome schists (greenish and red-wine-coloured stratified clays).

Starting 30 million years ago, the great accumulation of material deriving from the erosion of granite from the Alps caused an abrupt change of sedimentation in the sea, leading to the formation of macigno, a coarse sandstone with an ochre brown colour.

The rising of the Apennines 10 million years ago caused tectonic movements that interrupted sedimentation.

In the Pliocene, 3 million years ago, Monte Cetona was one of the islands of the Tuscan archipelago. The shallow coastal area, due to the large accumulation of earth sediments, was transformed into many brackish lakes. This is shown by the Belverde clays rich in molluscs of fresh and brackish water.

In the Quaternary, 2 million years ago, the water surrounding Mount Cetona gradually receded. Continental sediments accumulated on marine sediments. In the same period when a large swamp formed in the valley, extensive plates of travertine, a stratified and porous whitish rock, appeared on the eastern side. Its formation was due to the precipitation of calcium carbonate in waters rich in it, in the presence of hot thermal springs, waterfalls or drips. Analysis of impressions left in the travertine have shown the presence of holm oak, laurel and boxwood, which point to a warmer and wetter climate than the current one.