Naslov
The biostratigraphy and stable isotope paleoecology of the late Middle Eocene planktonic foraminifera

Autori
Premec-Fuček, Vlasta ; Pearson, Paul N. ; Hernitz Kučenjak, Morana

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

Izvornik
Forams 2010 - International Symposium on Foraminifera, Abstract Volume with program / Organizing Committee in Bonn - Bon : Rheinische Friedrich-Wilhelms-Universität Bonn, 2010, 165-166

Skup
Forams 2010 - International Symposium on Foraminifera

Mjesto i datum
Bonn, Njemačka, 2010

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
biostratigraphy; planktonic foraminifera; stable isotope paleoecology

Sažetak
The Middle and Late Eocene sediments in the North Adriatic Sea consist of hemipelagic deposits of marls and clayey marls with rich, moderately diversified and exceptionally well preserved planktonic foraminiferal assemblages. The succession studied was deposited on the eastern edge of the Venetian Basin in a slope to basinal environment. Significant biotic turnover occurs in planktonic foraminifera at the E13/ E14 Zones boundary. Highresolution biostratigraphic and multi-species isotopes analyses have been conducted on a 6 m cored interval from Istra more-5 well (1170-1176m). Two extinction horizons of the muricate species have been recorded. The first extinction level is at 1172.6 m, where large acarininids (Acarinina mcgowrani) abruptly disappeared. Only small acarininids persisted into the Late Eocene. Morozovelloides crassatus occurs in the fine fraction up to the depth of 1171.80 m. The 80 cm interval between two extinction horizons corresponds to approximately 10 kyr, according to the long-term average sedimentation rate of 8 cm per 1 kyr. Multi-species oxygen and carbon stable isotope analyses are used to define their relative depth habitats in the water column. Acarinina mcgowrani is species with the lightest δ18O and heaviest δ13C, suggesting calcification in the warmest surface water and temperatures of about 24-25°C. Slightly lighter δ13C signals show spinose species Globigerinatheka index and G. barri which most probably occupied mixed layer with temperatures of about 20-22°C. Numerous oxygen and carbon isotopic analyses of the Turborotalia pomeroli and T. cerroazulensis suggest upper thermocline habitat and temperatures in range of about 19-22°C. Subbotina eocaena., S. corpulenta, S. gortanii, Dentoglobigerina pseudovenezuelana and D. galavisi constantly show the heavier δ13C values and indicate thermocline habitat with temperatures of about 19-21°C. Lower thermocline waters inhabited only Subbotina linaperta and Catapsydrax unicavus. Fluctuation in both δ18O and δ13C values at all mentioned species, except Subbotina linaperta, near and between two extinction levels could imply changes of ocean circulation and instability of the water column, possibly indicating a period of increased ecological stress for surface dwelling planktonic foraminifera. After both extinction events the δ13C values show less variability suggesting a period of stability in ocean circulation. All biostratigraphical and isotopic data indicate well stratified water column and changeable warm to temperate climate conditions in the late Middle Eocene.

Izvorni jezik
Engleski

Znanstvena područja
Geologija

POVEZANOST RADA