Tectonic regionalization of the Carpathians

The criteria of a tectonis regionalization of the Carpathian Arc refer to historical geological development and to temporal differences in the consolidation, controlled by the main, or final, phases of folding.

According to distinct historical geological differences the whole Arc is divided into the Internal, or Central, Carpathians and the External, or Flysch, Carpathians. The Internal Carpathians is a province where not only the Miocene, but also the pre-Miocene folding took place. Some of its regions experienced several foldings only during the Alpine time. The External Carpathians is a province of solely Miocene folding. The latter took place here, at first, in more interior units, and then migrated towards the platform framing. The frontier between the two provinces is the Pieniny Klippen Zone which developed until Palaegene according to the Internal Carpathian type and after – according to the External one.

The differences between the two provinces are not only in the number and age of experienced foldings but also in their formational compositions. The External Carpathians appear to be a region of exclusively Flysch formation that has a considerable thickness (Cretaceous-Lower Miocene) and practically lacks igneous rocks. On the contrary, the Internal Carpathians are characterised by a variety of formations. The Marmarosch Crystalline Massif and the Marmorosch Klippen Zone located within the north-western continuation of the latter have a special position.

The above mentioned principles of the tectonic regionalization envisage delimitation of five main structural formational zones: the Internal Carpathians with the superimposed Miocene-Pliocene depressions playing the role of an interior molasse basins; the Pieniny Klippen Zone; the Marmorosch Belt; the Flysch Carpathians; and the Precarpathian Foredeep.

What are metamorphic rocks?

Rocks inside Earth’s crust are exposed to high temperature, pressures and solutions. These things can change rocks physically or chemically. Rocks changed by these forces are called metamorphic rocks. Metamorphic rocks can form from sedimentary, igneous, or even other metamorphic rocks. The term metamorphic comes from the Greek words meta and morphe which mean “to transform shape”.

Some metamorphic rocks are formed when sedimentary, igneous, or preexisting metamorphic rocks are subjected to extreme temperatures and pressures by a process called regional metamorphism. In other cases the rocks are transformed by contact from hot magma within Earth’s crust by a process called contact metamorphism.

Like igneous and sedimentary rocks metamorphic rocks may be coarse- or fine-grained. Metamorphic rocks are classified according to their lack or presence of banding. Foliated rocks have a wavy structure caused by the alignment of the minerals that make up the rock. Foliated rocks have a banded appearance and include schist, slate and gneiss. They are generally formed as a result of regional metamorphism. In nonfoliated rocks such as marble and quartzite there is no alignment of minerals. These rocks are generally formed via contact metamorphism.

Дата добавления: 2015-07-19