The Flysch Carpathians originate from the last phase of the Alpine orogeny and were formed ca. 16 mln years ago in an epoch named Miocene. The Alpine orogeny resulted from the collision of two continents, Africa and Europe.

The Flysch Carpathians, also referred to as the Outer Carpathians, have a different geological history than the older Inner Carpathians, developed at the end of Cretaceous and the beginning of Paleogene (65 mln years ago). The Inner Carpathians include the Tatras and Pieniny Mountains.

The Flysch Carpathians are formed mainly of sandstones and shales, in contrast to the Inner Carpathians, composed mainly of limestones. These specific sandstones and shales, named flysch, originated in the Carpathian Sea, part of the ancient Tethys Ocean.

Paleogeography

Paleogeography is the study of the ancient geographical distribution of seas and lands and its reconstruction.

The Carpathian Sea developed at the end of Jurassic and the beginning of Cretaceous, ca. 150 mln years ago, and functioned up to the Miocene, ca. 17 mln years ago. The Carpathian Sea was divided into parts called basins, often separated by island arcs named cordilleras. Eroded lands provided sand and mud, transported into marine depths by turbidity currents. With time, these loose sediments were transformed into solid sandstones and shales called flysch.…

Sedimentation

Sedimentation includes all processes of transport and deposition of mineral grains resulting in the formation of sediment. Diagenesis includes all processes transforming sediments into solid rock. An open marine sedimentation environment with slow settling of mineral particles in marine depths is called pelagic.

The flysch sedimentation environment is dominated by submarine gravity transport of mineral grains, mainly in suspension.

Flysch is a seqence of sandstones and shales, that were deposited from turbidity currents.

Turbidity currents are a mixture of sand, mud, clay and water that flow down the inclined bottom into marine depths. Turbidity currents may have attained a velocity of even 100 km/hr. Sediments may have been transported at distances of up to even 1000 kmby turbidity currents. Rocks formed within the activity of turbidity currents are referred to as turbidites. Thick-bedded (1-100 m) sandstones and conglomerates develop from sediments of high-density gravity flows. High-density flows are a mixture of sand, gravel, mud and often also entrained rock beds. Rocks formed in high-density and turbidity flows are referred to as fluxoturbidites.

In the Carpathians, a single rock bed was formed once for 10000 years on average.

Other gravity movements in the Carpathian Sea included slumps and debris flows.

Slumps and debris flows shifted packages of rocks or sediments, even several hundred meters in thickness, into marine depths.

Flysch sandstones are marked by various sedimentary structures. They include stratification within beds, e.g. horizontal, cross (ripple marks), and convolute (load casts) bedding. Bottom sandstone beds are often marked by hieroglyphs. They comprise traces of whirlpools (flute marks), roll marks of various objects (rolled on the bottom by the currents) and traces of movement of benthic organisms.

Palaeontology

Palaeontology is the study of fossil organisms.

Rocks of the Flysch Carpathians are poor in large fossils. Fossils are preserved mainly in shales. The microscopic, unicellular and planktonic algae and protozoans are the most frequent fossils. The rock profile includes specific rocks, important for science as comprising nearly only microfossils. These rocks are represented by the Cretaceous radiolarian shales with radiolarians (protozoans), Eocene-Oligocene Globigerina Marls with globigerins (foraminifers) and Oligocene Jasło Limestones with coccoliths (covers of calcareous algae).

Fossils of larger organisms are found occasionally.

Black shales of Lower Cretaceous age include infrequent ammonites and bivalves. Upper Cretaceous rocks may comprise bivalves (inocerams), however very rarely.

The Oligocene Menilite Shales are most abundant in macrofossils. They may include fish skeletons and occasional remains of seaweeds, herbaceous plants, woods, insects, amphipods, crabs or even turtles and birds. Such an accumulation of remains, often of fragile organisms, was possible in the noxious, anaerobic layer covering the sea bottom. These adverse life conditions prevented the decay of remains and their eating by scavengers. Similar conditions are presently found in the Black Sea. Trace fossils are traces of occurrence of organisms at the sea bottom and in sediment. They include various burrows and traces of movement.

Tectonics

Tectonics is the study of natural deformations in the Earth's crust. Continuous and discontinuous tectonics, involving bending and fissuring of rocks, respectively, may be distinguished. Carpathians were formed by great forces that detached, thrust and folded all rocks located in the Carpathian Sea. Initially, the Carpathian Sea showed horizontal bedding, with bed thicknesses exceeding 2 km, and a width of 200-300 km from north to south, i.e. 2-3 times larger than of the present Carpathians. Ca. 16 mln years ago, rocks of the Carpathian Sea were thrust northwards, folded and uplifted. Presently, the Flysch Carpathians locally attain a thickness of over 10 km. Huge rock units shifted in thrusts are named nappes. Nappes may have been thrust northwards for even over 50 km.