Wyniki wyszukiwania - BazTech

1

On imperfectly known Hauterivian representatives of the families Holcodiscidae Spath, 1923 and Barremitidae Breskovski, 1977 in Butkov Quarry (Central Western Carpathians, Slovakia)

Vašíček Zdeněk, Klein Jaap

Acta Geologica Polonica

|

2021

|

Vol. 71, no. 4

433--451

EN

In Butkov Quarry, ammonites of the families Holcodiscidae Spath, 1923 and Barremitidae Breskovski, 1977 occur in the pelagic Lower Cretaceous pelagic deposits of the Manín Unit. This contribution discusses the taxonomy of both families and presents their distribution in the layered sequences of the quarry. The genus Spitidiscus Kilian, 1910 classified as a member of the Superfamily Perisphinctoidea Steinmann in Steinmann and Döderlein, 1890 is an important representative of the Holcodiscidae from a stratigraphic point of view. In areas where the zonal index Acanthodiscus radiatus (Bruguière, 1789) does not occur, as in Butkov Quarry, the first representatives of Spitidiscus indicate the base of the Hauterivian. The genus Plesiospitidiscus Breistroffer, 1947 was long regarded as a member of the Superfamily Desmoceratoidea Zittel, 1895. This superfamily was based on its type species, Eodesmoceras celestini (Pictet and Campiche, 1860), which is not Valanginian in age, as now clearly proven. As a consequence, this superfamily is considered invalid. Vermeulen and Lahondère (2011) proposed an alternative by selecting a suitable initial genus, namely Plesiospitidiscus, for the Family Barremitidae, Superfamily Barremitoidea Breskovski, 1977 (nom. transl. Vermeulen and Lahondère, 2011).

2

Tescheniceras gen. nov. (Ammonoidea) and the definition of the Valanginian/Hauterivian boundary in Butkov Quarry (Central Western Carpathians, Slovakia)

Vašíček Zdeněk

Acta Geologica Polonica

|

2020

|

Vol. 70, no. 4

569--584

EN

Jurassic and Lower Cretaceous successions of the Manín Unit of the Central Western Carpathians are exposed in Butkov Quarry in the Middle Váh Region, Slovakia. A significant part of the macrofauna belonging to neocomitid ammonites, formerly classified under the genus Teschenites Thieuloy, 1971, occurs in deposits spanning the Valanginian/Hauterivian boundary. The original definition of Teschenites was accompanied by uncertainties in the taxonomic and stratigraphic position of its original type species, i.e., Hoplites neocomiensiformis Uhlig, 1902. The present contribution focuses on and provides a possible taxonomic solution by establishing the new genus Tescheniceras. In Butkov Quarry, the new genus includes five species. Tescheniceras flucticulum (Thieuloy, 1977), the type species, is the most abundant. Tescheniceras callidiscum (Thieuloy, 1971), the subzonal species for the uppermost Valanginian (Thieuloy 1971b), occurs only sporadically. Because Acanthodiscus radiatus (Bruguiére, 1789), the index species for the basal Hauterivian (radiatus Zone) in the international ammonite zonation, does not occur in the locality, the basal Hauterivian is indicated by the first appearance of the genus Spitidiscus Kilian, 1910.

3

Stepwise clockwise rotation of the Cenozoic stress field in the Western Carpathians as revealed by kinematic analysis of minor faults in the Manín Unit (western Slovakia)

Šimonová V., Plašienka D.

Geological Quarterly

|

2017

|

Vol. 61, No. 1

251--264

EN

This study aims at quantitative kinematic analysis of fault-slip data and palaeostress reconstruction of polyphase brittle structures developed in the Manín Unit cropping out in the Middle Váh River Valley of western Slovakia. The Manín Unit neighbours the Pieniny Klippen Belt that follows the boundary between the Paleogene accretionary wedge of the Outer Carpathians and the Cretaceous nappe system of the Central Western Carpathians. After the nappe emplacement during mid-Cretaceous times, the Manín Unit was incorporated into the Pieniny Klippen Belt and attained its complex tectonic style. Based on kinematic analysis of meso-scale faults with slickensides, six (D1–D6) brittle deformation stages have been discerned. The relative succession of individual palaeostress states was derived from field structural relationships; their stratigraphic age was estimated primarily by comparison with other published data. Palaeostress analysis in the Manín Unit revealed the existence of six different palaeostress fields acting from the Middle Eocene to the Quaternary. The first three generations of meso-scale brittle structures were formed under a transpressional tectonic regime during the pre-Late Eocene–Early Miocene D1–D3 deformation. Generally, the maximum horizontal stress axis rotated clockwise from a W–E to an approximately N–S direction. Thereafter, a transtensional tectonic regime was characterized by a WNW–ESE to NNW–SSE oriented minimum horizontal stress axis during Middle and Late Miocene D4–D5 deformation. A general extensional tectonic regime influenced the structural evolution of the area in the Pliocene to Quaternary, when a gradual reorientation of the palaeostress field resulted in the development of variable, often reactivated, fault structures.