Naslov
Krk impact structure ejecta breccia and melt rocks on the island of Rab, Croatian Adriatic: a clue on the impact target lithology

Autori
Marjanac, Tihomir ; Tomša, Ana Marija ; Marjanac, Ljerka ; Čalogović, Marina ; Fazinić, Stjepko

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

Izvornik
Bridging The Gap III: Impact cratering in nature, experiment and modelling / - Freiburg, 2015, 1-1

Skup
Bridging The Gap III: Impact cratering in nature, experiment and modelling

Mjesto i datum
Freiburg, Njemačka, 21.09.2015. - 26.09.2015

Vrsta sudjelovanja
Poster

Vrsta recenzije
Nije recenziran

Ključne riječi
Krk island ; impact structure ; impact breccia ; melt-rocks ; impact glesses ; provenance

Sažetak
The study of the proposed Krk impact structure ejecta was conducted on the surrounding northern Adriatic islands of Cres, St. Grgur, Goli and Rab, as well as along the mainland coast. At all of these localities, limestone breccia veneer was found disconformably overlying geological structures, and attributed to the informal unit of Krk-breccia (though on the Rab island it is usually referred to as Rab-breccia). Unlike Jelar-breccia which occurs along the Velebit Mt. front, the Krk-breccia comprises boulder-size clasts of Eocene sandstones and marls with the Krk island provenance. The impact melts are found on eastern coasts of the Krk and Rab islands, but only in secondary position. At one Rab island locality, contact thermal metamorphosis of sandstone base-rock was found, indicating its progressive melting from the surface downwards. Two types of melts can be differentiated ; i) incomplete melts with remnants of unmelted sandstones, usually with melted rims, and ii) massive crystalline glass, sometimes with flow structures. The massive glass is found on the Rab island and occurs in form of small boulder chunks, 10-30 kg in weight. These were found to lay above Eocene siliceous sandstones, and some glass blocks were embedded in an old Roman wall. The glass is dark bluish in colour, crystalline with olivines predominating, massive and only locally vesicular. The chemical composition of glass shows predominance of iron (73 % in average), whereas vesicles are sometimes filled with secondary carbonate.

Izvorni jezik
Engleski

Znanstvena područja
Geologija

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