Geologia di Manarola (Cinque Terre)

Sun, sea, exquisite food, and beautiful panorama are likely the first things that come to mind when visiting Manarola, in the scenic Cinque Terre National Park, in Italy, but… did you know that this seaside paradise owes its fame to the geologic forces that shaped these places and continue to shape them today?

The Ligurian coast is famous for its rocky cliffs hiding coves and bays towered by small fishing towns, surrounded by vineyards, olive trees, and scented Mediterranean scrub. The Cinque Terre, and many other places in the area like Portovenere e Levanto attract every year (well, maybe not the last one) thousands of travellers, food lovers, hikers, and bathers. The area owes its unique beauty to the Ligurian Apennines, with their steep mountains and cliffs right next to the sea. The reason why panoramas like this are common here is that these places are geologically very young: the Apennine mountains, formed by the collision between Europe and Africa, largely uplifted only in the past 4 – 6 million years. As soon as the mountains rose above the sea, erosion started to carve valleys, coves, and cliffs. The resulting landscape has high peaks, many reaching elevations over 1500 – 1800 meters, overlooking the sea.

The rocks constituting the rocky cliffs, where many villages in the Cinque Terre sit upon, are in large part flysch deposits. Flysches are deep sea fan sedimentary deposits left by submarine landslides e turbidity currents – very fast flows of water and sediments that may travel for hundreds of kilometers on the seafloor. In the Mediterranean region, flysch deposition was very common during the Cenozoic, as large mountain chains like the Alps started to rose above the sea and were started to be eroded. Rivers transported the huge sediment load to the sea, where it finally deposited as km-thick sequences in abyssal plains, submarine trenches, and deep sea fans. The region of Liguria is dominated by many Cretaceous – Oligocene flysch deposits, made predominantly of sandstone, claystone, marlse limestone layers.

Our tour in the incredible geology of the area starts with the picturesque village of Manarola, seen from the north in the panorama above. The village sits upon a small cove exposing layers of the Cretaceous – Oligocene Canetolo Unit, containing the turbidite sequences of the Canetolo limestones and claystones (Argille e Calcari di Canetolo) and the Ponte Bratica sandstones (Arenarie di Ponte Bratica). The contact between the two is visible in the cliff supporting Manarola: the Ponte Bratica sandstones form thick layers that, to the left/east, pass to fine-grained, thin layers of claystones and marls of Canetolo. Immediately behind, a refolded and verticalized tectonic contact hidden by the village thrusts the Canetolo Unit over the Oligocene – Lower Miocene turbiditic sequences of the Macigno sandstone, belonging to the Tuscan Nappe.

The path to the north passes through rocky cliffs with chaotic sequences of folded sandstone and claystone layers of the Ponte Bratica sandstone, crosscut by fractures, joints, and faults. It is not very easy to see structures here, because the cliffs are too steep and the elevated path is too crowded with tourists. Let’s avoid the crowd and move further to the south!

A nice vantage point allow us to see the beautiful geology (and not only that) of the Cinque Terre, just north of Manarola. Here you can enjoy a natural W-E cross section through the more internal part of the Northern Apennines. What happens when oceans close and rocks get squeezed together? You get thrust faults that shorten the crust piling units (or nappes) on top of each other. In the farthest point, around Monterosso, you can see from left to right the Cretaceous – Paleocene Gottero sandstone, the val Lavagna Schist, and the Jurassic Ligurian ophiolite. These are all ‘pieces’ of the ancient Ligurian (or Alpine Tethys) Ocean that was completely destroyed during the formation of the Alps and the Apennines (see my previous post on Castiglioncello). To the east, the Ligurian ophiolites are thrust over a chaotic complex – the Colli Tavarone mèlange – consisting of Paleocene slide blocks and submarine landslide deposits. These units are thrust over the Canetolo Unit and the Macigno sandstone, to the far right/east. The folded contact between the Canetolo Unit and the Macigno sandstone draws a syncline of nappes, cored by the Canetolo Unit.

The small village of Corniglia, well visible on the cliffs to the north, sits on another scenic outcrop. If you look closely and zoom, you can see a very complicated fold in the Macigno sandstone. The annotated image above is my personal interpretation of this magnificently exposed structure, which shows multiple open to tight folds crosscut by many reverse faults.

I have checked the geologic map of the area (both the earlier by Ernesto Abbate and the most recent Foglio 248 – La Spezia) and I am happy to agree with the interpretation of former geologists! This is an extract from the 1966 map of the area by E. Abbate, showing the vantage point for the panorama above.

In the cross section (where I have just highlighted some structures), we can see both the complex folding in the Macigno sandstone along the coast, right beneath Vernazza e Corniglia, and the large syncline of Canetolo Unit within the Macigno sandstone. This complex structures formed due to thrusting, folding, and re-folding during the earliest stage of Oligocene-Miocene mountain building in the Apennines. What to say? These mountains are really born to give geologists headaches!

BONUS: We deserved a nice lunch with a view!

References and further reading
Abbate E. (1966) – Carta geologica delle Cinque Terre.
Foglio 248 – La Spezia by ISPRA.
Geology, geomorphology, and wines in the Cinque Terre National Park.