Naslov
Permian–Triassic Boundary: many possible locations, but can you really see it? Croatian example

Autori
Fio, Karmen ; Vlahović, Igor ; Sremac, Jasenka ; Spangenberg, Jorge E. ; Velić, Ivo ; Velić, Josipa

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
World Summit on P-Tr mass extinction & Extreme climate change - Abstracts / Chen, Zhong-Qiang ; Yang, Hao ; Luo, Genming - Wuhan : China University of Geosciences, 2013, 22-23

Skup
World Summit on P-Tr mass extinction & Extreme climate change

Mjesto i datum
Wuhan, Kina, 13.06.2013. - 15.06.2013

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Nije recenziran

Ključne riječi
Permian-Triassic Boundary; chemostratigraphy; lithostratigraphy; Croatia

Sažetak
The Late Palaeozoic deposits in Croatia were derived from the Palaeotethyan shelf areas along the northern Gondwana passive continental margin. They consist of carbonate, clastic and evaporite deposits which outcrop in 11 tectonically limited areas within the Inner and Outer (Karst) Dinarides, as well as occurring as clasts in younger sediments, or in drilling-core samples (Sremac, 2005 ; Fio et al., 2013). Many sheets of the geological map of Croatia offer potential locations of Permian–Triassic boundary, but the reality is quite different: the contact is mostly covered, tectonized or marked by emergence, offering only several locations suitable for detailed studies. This can be best seen in the Velebit Mt. area: although continuous transition from Permian to Triassic is proposed in a more than 15 km long zone (Salopek, 1948 ; Sokač et al., 1974), the continuous transition from Permian to Triassic was up to now confirmed at only two locations, Rizvanuša and Brezimenjača sections (Fio et al., 2010). In the Velebit Mt. area the uppermost Permian deposits are represented by the Transitional Dolomite (TD). These are followed by the Sandy Dolomite (SD), which are relatively rich in terrigenous material and were generally attributed to the Lower Triassic. The lithologic TD–SD boundary is sharp, in places clearly erosional, and was previously considered as the Permian– Triassic boundary (PTB). Findings of the relatively rich assemblage of Permian fossils in the lowermost part of the SD, similar to the uppermost fossiliferous layer in the underlying TD, with no sign of redeposition, indicated that the PTB should be positioned at or above that level. Combination of palaeontological and sedimentological data, together with stable isotopes of carbonates (δ13Ccarb, δ18Ocarb), organic matter (δ13Corg, δ15Norg) and major, trace and rare earth elements, helped to determine the chemostratigraphic PTB in this area. The chemostratigraphic PTB is not visible in the field, but it is positioned within the SD, 11 m above the lithologic TD–SD boundary in the Rizvanuša section, and 0.2 m above it in the Brezimenjača section (Fio et al., 2010). Uppermost Permian and Lower Triassic fossils were also found in a recently open profile in the Samoborska Gora Mt. (NW Croatia) composed of dolomites and dolomitic breccia. Lower and upper parts of the sequence represent shallow marine, possibly lagoonal facies, and comprise stratigraphically indicative Permian and Triassic biota, respectively. Middle part of the sequence is dominantly composed of intrabasinal breccia, with dessication features, and contains only disaster taxa (PTB survivors). This horizon is referred to as ‘Transitional beds’, with expectations to determine chemostratigraphical PTB in the future within this part of the sequence (work in progress). Further planned investigations of the PTB in Croatia include locations in the Gorski Kotar with proposed continuous clastic shallow-marine deposition and/or stratigraphic break at the PTB, and Central Dinarides (central and northern Dalmatia, SE Lika and western Bosnia) with Upper Permian and Lower Triassic evaporites, volcanic and clastic rocks.

Izvorni jezik
Engleski

Znanstvena područja
Geologija

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