The north-western continental margin of the Barents Sea represents the only gateway for deep-water masses moving between the North Atlantic and the Arctic Oceans. The transfer of heat and salt to the Arctic Ocean is mainly attributable to the relatively warm and saline water masses inflow of the West Spitsbergen Current (WSC), which strength varied considerably over time in association with climate changes. On this respect, the western Svalbard margin, located on the western side of the Fram straight, represents a key area to study the paleoceanographic variation of the North Atlantic/West Spitsbergen currents. Contour currents along the south-western continental margin of the Svalbard area, generated expanded sedimentary sequences suitable for high-resolution paleoceanographic and paleoenvironmental reconstructions. The Storfjorden-Kveithola glacial sedimentary system (south of Svalbard) was investigated during the EGLACOM and CORIBAR projects (Fig. 1) with the aim of reconstructing the deep-water paleoceanographic evolution after Last Glacial Maximum. Here we present the preliminary results concerning the benthic foraminifera of a multidisciplinary study carried out on a 9 m long core collected from the middle slope of the Kveithola Trough Mouth Fan and two cores collected from the middle slope off Storfjorden glacial system. Sediment samples were analysed for textural, compositional and micropaleontological aspects (using benthic and planktonic foraminifera, diatoms and calcareous nannofossils). A preliminary age model has been built on the basis of magnetic susceptibility correlations with previously studied cores for which the age model was based on the palaeomagnetic record and radiocarbon dating. The benthic foraminifers are scarce in the lithological units that represent the deglaciation after LGM, and became abundant in the Holocene sequences, as generally observed for other microfossils taxa. The preservation state of the benthic foraminifera, indicated as percentage of fragmentation, is generally low in the glaciomarine sediments and decreases upcore towards the recent sediments, where open marine conditions prevail. Here the benthic foraminifera assemblage contains Cassidulina reniforme, Cassisulina teretis, Islandiella helenae/norcrossi, Melonis barleeanum and Cibicidoides wuellerstorfi. The assemblage is indicative of non-permanently ice-covered conditions since about 16 ka. The significant occurrence of small taxa, such as Stetsonia horvati, during the medium-late Holocene suggests a condition of low productivity and consequently low content of organic matter to the sea floor. Some peaks of agglutinated species, corresponding to high percentage of fragmentation/dissolution, along the core CORIBAR GeoB17603-3 core, could suggest the influence of cold, salty and dense waters (brines) coming from the shelf area, that are very aggressive to the calcareous tests.
Benthic foraminifera for the study of the deglaciation post LGM in the southwestern Svalbard slope (Arctic Ocean)
Morigi C.;
2016-01-01
Abstract
The north-western continental margin of the Barents Sea represents the only gateway for deep-water masses moving between the North Atlantic and the Arctic Oceans. The transfer of heat and salt to the Arctic Ocean is mainly attributable to the relatively warm and saline water masses inflow of the West Spitsbergen Current (WSC), which strength varied considerably over time in association with climate changes. On this respect, the western Svalbard margin, located on the western side of the Fram straight, represents a key area to study the paleoceanographic variation of the North Atlantic/West Spitsbergen currents. Contour currents along the south-western continental margin of the Svalbard area, generated expanded sedimentary sequences suitable for high-resolution paleoceanographic and paleoenvironmental reconstructions. The Storfjorden-Kveithola glacial sedimentary system (south of Svalbard) was investigated during the EGLACOM and CORIBAR projects (Fig. 1) with the aim of reconstructing the deep-water paleoceanographic evolution after Last Glacial Maximum. Here we present the preliminary results concerning the benthic foraminifera of a multidisciplinary study carried out on a 9 m long core collected from the middle slope of the Kveithola Trough Mouth Fan and two cores collected from the middle slope off Storfjorden glacial system. Sediment samples were analysed for textural, compositional and micropaleontological aspects (using benthic and planktonic foraminifera, diatoms and calcareous nannofossils). A preliminary age model has been built on the basis of magnetic susceptibility correlations with previously studied cores for which the age model was based on the palaeomagnetic record and radiocarbon dating. The benthic foraminifers are scarce in the lithological units that represent the deglaciation after LGM, and became abundant in the Holocene sequences, as generally observed for other microfossils taxa. The preservation state of the benthic foraminifera, indicated as percentage of fragmentation, is generally low in the glaciomarine sediments and decreases upcore towards the recent sediments, where open marine conditions prevail. Here the benthic foraminifera assemblage contains Cassidulina reniforme, Cassisulina teretis, Islandiella helenae/norcrossi, Melonis barleeanum and Cibicidoides wuellerstorfi. The assemblage is indicative of non-permanently ice-covered conditions since about 16 ka. The significant occurrence of small taxa, such as Stetsonia horvati, during the medium-late Holocene suggests a condition of low productivity and consequently low content of organic matter to the sea floor. Some peaks of agglutinated species, corresponding to high percentage of fragmentation/dissolution, along the core CORIBAR GeoB17603-3 core, could suggest the influence of cold, salty and dense waters (brines) coming from the shelf area, that are very aggressive to the calcareous tests.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
