Naslov
Clay mineral assemblages in pelitc material associated with subaerial unconformities in Early Cretaceous shallow-water carbonate sediments in Istria, Croatia

Autori
Durn, Goran ; Ottner, Franz ; Tišljar, Josip ; Schwaighofer, Bernd ; Müller, Harold

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

Izvornik
Clays for our Future / Griffin, D. L. - Ottawa : Carleton University Otawa, Ontario Canada, 1997

Skup
The 11th International Clay Conference, Clays for our Future

Mjesto i datum
Ottawa, Kanada, 15.06.1997. - 21.06.1997

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
Emersion layers in Early Cretaceous shallow-water carbonates; Paleosols; Smectitic and illitic clay; Aluminium-rich montmorillonites; Aeolian derived material; Istria (Croatia)

Sažetak
Paleosols which blanket local and regional subaerial unconformities related to hiatuses in shallow-water carbonate sedimentation bear important information on (1) material supply, (2) climate, (3) relief, and (4) duration of subaerial exposure phases. The intent of the present study is to define clay minerals in pelitic materiaks which occur as emersion layers in Early Cretaceous shallow-water carbonate sediments in Istria. They are particularly well expressed in West Istria where, from Hauterivian to the upper part of Late Albian at least 8 subaerial exposure phases of different duration occur. These unconformities are accompanied by greenish grey pelitic layers with high clay content whose thickness is paleorelief related and laterally changes from several centimetres up to 1 meter. They occur as either emersion breccias with clayey matrices or, more often, as clays. They have a very high clay content up to 95%. Most samples are composed only of clay minerals with small amounts of quartz and pyrite. The clay fraction (<2mm) consists mainly of smectitic and illitic material, in some samples small amounts of kaolinite and chlorite were detected. According to infrared studies the smectites are aluminium-rich montmorillonites without iron substitution in the octaeder position; the amount of magnesium is also very low. The 10Ĺ peak of the illitic material is very broad which indicates a very small particle size. REE patterns in clays from the Late Aptian regional emersion may indicate that their main source rocks are not the underlying limestones (e. i. insoluble residue) but some aeolian derived material.

Izvorni jezik
Engleski

Znanstvena područja
Geologija

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