During the late Oligocene to early Miocene the residual Magura Basin was located along the front of the Pieniny Klippen Belt (PKB). This basin was supplied with clastic material derived from a south-eastern direction. In the Małe (Little) Pieniny Mts. in Poland, the late Oligocene/ early Miocene Kremna Fm. of the Magura Nappe (Krynica subunit) occurs both in front of the PKB as well as in the tectonic windows within the PKB. Lenses of exotic conglomerates in the Kremna Fm. contain frequent clasts of Mesozoic limestones (e.g. limestones with “filaments” microfacies and Urgonian limestones) and Eocene shallow-water limestones. Fragments of crystalline and volcanic rocks occur subordinately. The provenance of these exotic rocks could be probably connected with Eocene exhumation and erosion of the SE part of the Dacia and Tisza Mega-Units.

In the Polish sector of the Magura Nappe have long been known and exploited carbonate mineral waters, saturated

with carbon dioxide, known as the “shchava (szczawa)”. These waters occur mainly in the Krynica Subunit

of the Magura Nappe, between the Dunajec and Poprad rivers, close to the Pieniny Klippen Belt (PKB). The

origin of these waters is still not clear, this applies to both “volcanic” and “metamorphic” hypotheses. Bearing

in mind the case found in the Szczawa tectonic window and our geological and geochemical studies we suggest

that the origin of the carbon dioxide may be linked with the thermal/pressure alteration of organic matter of the

Oligocene deposits from the Grybów Unit. These deposits, exposed in several tectonic windows of the Magura

Nappe, are characterized by the presence of highly matured organic matter – the origin of the hydrocarbon accumulations.

This is supported by the present-day state of organic geochemistry studies of the Carpathian oil and

gas bed rocks. In our opinion origin of the carbon-dioxide was related to the southern, deep buried periphery of

the Carpathian Oil and Gas Province. The present day distribution of the carbonated mineral water springs has

been related to the post-orogenic uplift and erosion of the Outer (flysch) Carpathians.