Krempachy Marl Formation

The Pieniny Klippen Belt represents an axial tectonic zone on the West Carpathians, with a narrow structure, that extends a several hundred kilometers long structural zone belonging to the Carpathian sector of the Alpide belt, and separates the Southern Carpathian and the Central Carpathian.^[2][4] While the Pliensbachian-Toarcian boundary is nearly unknown on the Belt, the Toarcian to Bajocian succession is present on various points.^[2] The belt is a Laramian Front inside the Central Carpathian Orogenic Wedge, that had a re-folded along with a strong compressed process during the Alpine thrusting of the Outer Carpathians in the Neogene.^[4] The belt has a series of lithofacies patterns that recover from the Middle Jurassic to the Lower Cretaceous paleogeographical changes on the east Bohemian Massif margin, and reflects a paleobathymetric gradient change, that was developed around the Czorsztyn Swell de to a crustal block of Oravicum,^[5] correlated to the contemporaneous Briançonnais.^[6] The Toarcian basin was located to the north of Oravicum, being on the NE of the North European Shelf.^[4] It was an area that suffered from Middle Jurassic that would have ended forming the Magura Basin.^[4] After that, sedimentary infill was translated northward to the nearshore platforms, and then formed nappe structures and flysch mélange.^[7] The view and reconstruction of the sedimentary basins on the Toarcian realm is very complicated, since they lost their original geometry due to tectonic works and deformations on the Noegene, abundant allochthonous material and several hiatus on the strata.^[4]

The strata of the formation is composed by grey-blue marl & limestones. The formation overlies Sinemurian to Pliensbachian deposits of the Orava Unit, where there is disposed a southwest bedding dipping. The lowermost part of the strata recovers spotted limestone beds & alternations of dark Marls that are equivalent to the uppermost Allgäu Formation.^[8] Over the marls there is a series of dark shales that had intercalated siltstones, that mark the start of the main Krempachy Marl Formation. The marls of the main formation strata are covered on Ammonite fragments, intercalated with Dinoflagellates.^[9] There is a condensation of the Lower-Middle Toarcian deposits throughout the Western Carpathians. As that, in the Pieniny Klippen Belt, sections like the Tenuicostatum and Serpentinum zones of the early Toarcian are or completely missing or strongly condensed.^[10] Altroght sections such as Zázrivá A provide the first record of the T-OAE from all Western Carpathians.^[9] Zázrivá A has an expressure of 36 m, oriented to the Southwest.^[4]

The Krempachy Marl is rich in black shales in its lowermost parts, which are locally rich in macrofauna, including ammonites, soft-bodied cephalopods,^[9] bivalves, crustaceans and fish remains.^[4] Manganese mineralization is also common in the oldest part, something shared with most of the coeval Alpine Tethys successions.^[11] Due to that, there is a high concentration of Mn contents (6 to 10 wt%).^[12] Typical Toarcian sections of the Orava Succession are represented by condensed red marls, marly limestones, and/or red nodular limestones, being locally rich in ammonites.^[4]