Geology of Romania

The Carpathian Mountains are part of the Alpine-Himalayan chain, formed only about 35 million years ago in the Tertiary alpine orogeny, but there is as yet no explanation for the S-shape of the Carpathian-Balkan system. The Carpathian Mountains system is as long as the Alps (1.300 Km, but with its ends on the Danube, at Bratislava and the Iron Gates, only 500 Km apart) but only half their height, making it easier to cross. The system underwent Quaternary glaciation only in the Karkonosze, Tatras, Rodnas and the southern Carpathians. The far older and lower remnants of the Hercynian mountains lie parallel to the north, running from the Vosges via the Ardennes, the Black Forest and southern Poland to northern Dobrogea on Romania’s Black Sea coast. For the most part the Carpathians are 35-40 Km wide (double that in the Parâng area and three times that in the Rodnas) and generally consists of three distinct bands with Flysch (or tubidite) sediments on the outside, young crystalline massifs in the center in some volcanic intrusions on the inner side.

The chain is divided into four sections, of which the third and fourth (starting from the West) are in Romania.
So the northern limit of the Romanian Carpathians is the Tisa river. From here almost to Braşov the mountains consist of parallel ridges of sedimentary rocks (sandstone and conglomerates) to the east, a central crystalline schist zone with some resistant limestones, and to the west an inner zone of volcanic material. Between the crystalline and volcanic zones are eight major basins filled with fertile loess and alluvium, such as those around Miercurea Ciuc and Târgu Secuiesc.

The southern Carpathians go from Braşov all the way to the Iron Gates. Like the Alps, this section underwent intense folding, followed by three phases, including glaciation, that left platforms of meadow mostly to the west of the Olt Valley. The Fagaras and Retezat massifs are mainly hard crystalline rocks, and there are various areas of karstic limestone. Here are reached the highest peaks in Moldoveanu (2.544 m) and Negoiu (2.535 m). To the west, the Banat mountains are largely sedimentary, with beds of coal around Anina.

In addition the Apuseni (Western) mountains (including the Bihor massif) block off the Transylvanian basin to the west, forming a rather awkward spur to the north of the main Carpathian chain. They consist of ancient crystalline rocks, Paleozoic and Mesozoic sediments and recent volcanic material, and are a very complex area of irregular depressions and stranded massifs with meadow platforms or suspended plains. There was erosion but no glaciation in the Quaternary, producing peri-glacial forms. Above all, this is the main karst zone of Romania, producing many gorges, caves and potholes, while tertiary eruptive forms give a haystack form to the Munţii Metaliferi (Metal-bearing Mountains), where gold, silver and mercury have been mined for nearly 2000 years.

Also in Romania, although not part of the Carpathian system, you’ll come across references to the following areas:

1. The Transylvanian basin – undulating hills of highly fertile Tertiary sediments such as clays, sandstone and loess. The lowest areas such as the Barsa country around Brasov and the Fagaras deperssion did not drain until the Quaternary era, and there are still some peat marshes as a result.
2. The Sub-Carpathians or outer foothills of the Carpathians – mostly folded Tertiary sediments, with oil in Pliocene formations to the north of Bucharest.
3. The Romanian lowlands – formed of loess east of the Olt River, and of sand to the west. This is covered with cernoziom (chernozem) or black-earth soils forming very fertile agricultural land.
4. The northern Dobrudja forms the end of the worn-down Hercynian chain, with granite, limestone and schists dating from the Primary era, some of the oldest rocks in Europe, while immediately to the north the youngest land in Europe is still being formed in the Danube Delta

If  you’re interested in Geology, you might find this tour interesting:

Geology Tour in Făgăraş Mountains

Caving in Apuseni Mountains, Romania