Naslov
Foraminiferal assemblage of Pliocene sediments from Kristina-1 well (north Adriatic)

Autori
Miletić, Danica

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

Izvornik
22nd IAS Meeting of Sedimentology, Abstracts Book / Vlahović, Igor - Zagreb : Institut za geološka istraživanja, Zagreb, 2003, 131-131

Skup
22nd IAS Meeting of Sedimentology

Mjesto i datum
Opatija, Hrvatska, 17.09.2003. - 19.09.2003

Vrsta sudjelovanja
Poster

Vrsta recenzije
Nije recenziran

Ključne riječi
foraminiferal assemblage; Pliocene sediments; Kristina-1 well

Sažetak
Exploration off-shore Kristina-1 well is located at the north part of Adriatic Sea, in the depression of Dugi Otok island. Only one cored interval (808-814 m) was available, so the drill cuttings were collected at the intervals of 5 m, through the entire profile of the well. The paleontologic analyses have been examined on washed samples. The stratification of deposits has been determined on the basis of vertical distribution of the microfossil assemblages and characteristic species of the planktonic foraminifera. The Pliocene clastic sediments, consisting of clayey marl, silt and sand intercalations, trasgressively overlie Miocene sediments. The thickness of the sediments depends of local tectonics and paleorelief. The succession of foraminiferal assemblages started by small monothalamic shallow water lagenid forams (Sgarrella & Moncharmont Zei, 1993): Lagena costata (Williamson), Lagena striata (d&#8217 ; ; Orbigny), Oolina squamosa (Montagu), Oolina hexagona (Williamson), Fissurina bradyana (Fornasini), Globulina gibba (d&#8217 ; ; Orbigny), and shallow water species Elphidium crispum (Linne), Elphidum complanatum (d&#8217 ; ; Orbigny), Ammonia beccarii (Linne), Cibicides lobatulus (Walker & Jacob), and Asterigerinata planorbis (d&#8217 ; ; Orbigny). Through the widening of the marine environment, ecological conditions became stable, both the number of individuums and number of species increase: Amphistegina lessonii d&#8217 ; ; Orbigny, Trifarina angulosa (Williamson), Trifarina fornasinii (Selli), Rosalina globularis d&#8217 ; ; Orbigny, Flo-rilus boueanus (d&#8217 ; ; Orbigny), Lenticulina div. sp., Melonis padanum Perconig, Siphonina planoconvexa (Silvestri), Anomalinoides helicinus (Costa), Anomalinoides ornatus (Costa), Planulina ariminensis d&#8217 ; ; Orbigny, Hetereolepa floridana (Cushman), Bulimina aculeata d&#8217 ; ; Orbigny, Bolivina div. sp., Brizalina italica (Cushman), Uvigerina rutila Cushman & Todd, Cassidulina crassa d&#8217 ; ; Orbigny, Cibicidoides ungerianus (d&#8217 ; ; Orbigny), Cancris auriculus (Fichtel & Moll), Pullenia bulloides (d&#8217 ; ; Orbigny), Spaeroidina bulloides d&#8217 ; ; Orbigny and deepwater forms Oridorsalis umbonatus (Reuss) and Gyroidina soldanii (d&#8217 ; ; Orbigny). During the Middle and Upper Pliocene, in the similar lithological succession, foraminiferal assemblage increase in number of deeper water species. A sequence of Pliocene index planktonic foraminifera Globorotalia margaritae - Globorotalia puncticulata - Globorotalia bononiensis - Globorotalia aemiliana - Globorotalia crassaformis - Globorotalia inflata suggest continuous sedimentation through biozone MPl-1 to MPl-6 (Sprovieri, 1992). It has been proven through biostratigraphical research of the sediments from Kristina-1 well, that the Pliocene is characterized by a general transgressive trend. The reestablishment of marine regime after Miocene regression, started in the Lower Pliocene by shallow water sedimentation. The stable ecological conditions were established during the upper part of Lower Pliocene. The widening of the marine environment through Pliocene, on tested well, has been evidenced by benthic foraminiferal assemblages. The planktonic assemblages showed strong similarities with those of tropical regions because open connection existed between the Mediterranean and the Atlantic (Bolli et al., 1985). The established stratigraphic relations, based on the composition and diversity of the foraminiferal assemblages and the lithological characteristics of sediments, indicate a continuous marine conditions through Middle and Upper Pliocene to the Pleistocene age. The abundance of benthic foraminifera (70 different species were recorded) suggests the final sedimentation in the outer shelf environment. The communication with open sea is documented by mentioned index planktonic foraminifera and Globigerina bulloides d&#8217 ; ; Orbigny, Globigerina falconensis Blow, Orbulina universa d&#8217 ; ; Orbigny, Globigerinoides obliquus extremus Bolli & Bermudez, Globigerinoides trilobus (Reuss), Globigerinoides ruber d&#8217 ; ; Orbigny, Globigerinoides conglobatus (d&#8217 ; ; Orbigny). Recent explorations have shown that the micropaleontological studies and biofacies analyses of the rock material from the drilled wells may yield reliable results in biostratigraphical classification and paleoenvironmental reconstruction of the investigated sediments. These results have a direct application to the structural and tectonical interpretation of the sediments from drilled wells.

Izvorni jezik
Engleski

Znanstvena područja
Geologija

POVEZANOST RADA