engleski

Changes during the Late Quaternary to Holocene period recorded in planktonic assemblages from the Mid-Adriatic Deep (Adriatic Sea)

The piston core AMICI 99-02, in 259.2 m of water in the Mid-Adriatic deep (MAD, Central Adriatic Sea), has been investigated for planktonic distributional patterns. Excellent core recovery provides a Late Quaternary - Holocene ecord dominated by clays, silty clays, sand muds and thinner packages of tephra layers. The age model applied is based on AMs 14 c dating with tephrochronological studies from ajacent cores. The modern assocition of the MAD, deduced from the coretops, mainl comprises shallow-dwelling tropical-subtropical Globigerinoides ruber white forms. The most numerous planktonic foraminiferal species, from studied 1 cm thick deposit slices, were grouped according to their temperture preferences. Group I contain species preferring warm water surface temperatures and a well stratified water column and include G. ruber (White and pink varieties), Globigerinoides sacculifer, Globigerinella calida and Neogloboquadrina dutertrei. Neogloboquadrina pachyderma, Globigerina bulloides, Globorotlia inflata and Globigerina quinqueloba, conidered as transitional to polar upwelling form, constitute Group II. Forminiferal assemblages of Holocene records (to 500 cm below sea floor) demostrate that relatively warm conditions prevailed, and were interrupted by cooling of the sea surface at around 8 Ka BP. A marked increase in sea surface temperture is indicated by an increasing percentage of representatives of Group I at around 3.2 Ka BP. Late Quaternary history i characterized by dominance of polar to subpolar eutrophic to mesotrophic planktonic foraminifera (repreentatives of Group II). A pronounced variation in planktonic assemblage composition (60% warm vs. 38% cold specimens) characterizes the Tephra event (about 12.6 Ka BP).

Holocene; Late Quaternary; planktonic; foraminifera

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