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Millennial oceanographic changes during the last glacial cycle recorded in the NE Atlantic core KTA-GC-05

AuthorsFrancés, G.; Mena, Anxo; Caínzos, V.; Pérez-Arlucea, Marta; Nombela, Miguel Ángel; Alejo, I.; Estrada, Ferran ; Diz, P.
Issue Date13-Jun-2014
CitationBook of Abstracts submitted to the IV Congress of Marine Sciences. Las Palmas de Gran Canaria, June 11th to 13th: 196-197 (2014)
AbstractA high-resolution multiproxy study of core KTA-GC-05 (46.18595 N, 18.31385 W; 3939 m below sea level; 337 cm long) has been carried out in order to investigate the effects of millennial and submillennial climatic changes on the Northeast Atlantic oceanography during the last climate cycle. This approach includes physical properties (Multi-sensor Core Logger, MSCL, and Computerized Tomography, CT), lithological, sedimentological and geochemical characterization, and oxygen and carbon stable isotope analyses in monospecific samples of planktonic foraminifera G. bulloides. Integrated information from independent proxies that show common trends along the core enables distinguishing three units. The basal unit (at around 120 cm thick) is mainly composed by nannoplankton and foraminifera oozes with three intercalated intervals characterized by higher amounts of coarse and very coarse terrigenous silt. Oxygen stable isotopes (18O) values and micropaleontological features, as well as other proxies suggest this basal unit was deposited during the Last Interglacial (Marine Isotope Stage 5, MIS 5). Many other proxies, as terrigenous markers (Fe/Ti, K/Ti) but also biogenic input (Ca/Ti, TIC) and grain-size parameters fluctuate according the same pattern. Higher values of these markers and lighter 18O could correspond with warmer substages of MIS 5. These data from warmer subestages suggest higher contribution of terrigenous particles due to enhanced Atlantic Meridional Overturning Circulation (AMOC), although the pelagic contribution was dominant. On the contrary, intervals characterized by low values of terrigenous proxies and finer grain sizes in the non-carbonate fractions could corresponds with relatively colder substages and weaker bottom currents. The second unit (at around 190 cm thick) presents darker colors and a broader variety of facies. CaCO3 content is lower than that of previous unit and conversely the terrigenous component is much higher. Lithology consists of mud and sandy mud being the sand fractions dominated either by terrigenous or bioclastic grains or a mixed of both types. No doubt exists about this unit was deposited during the Last Glaciation (MIS 2-4). The record of glaciation shows strong signals of high-frequency climatic oscillations, as it occurs in other North Atlantic cores. In particular, the stronger recorded events coincide with the more intense stadials (Heinrich Events, HE). HE are clearly identified in the studied core by numerous proxies: high amounts of ice rafted debris (IRD) and the polar planktonic foraminifera N. pachyderma (sin), higher values of density, magnetic susceptibility and terrigenous markers, as well as peaks of Zr/Sr and Ca/Sr ratios. Higher values of planktonic 18O occurred at times of H1, H5 and H6, when also very low percentages of TIC are recorded. A reduced productivity as a consequence of the arrival at this latitude of polar and/or melt surface waters, dilution by increased terrigenous input and calcium carbonate dissolution at deep-sea can explain lower carbonate accumulation. Stopped AMOC during extreme cold events favored the influence of corrosive bottom waters and thus carbonate dissolution. As the previous HE, H3 is characterized also by very low calcium carbonate content, but in this case, other proxies suggest it is due to dilution by enhanced terrigenous input. [...]
DescriptionIV Congress of Marine Sciences, 11-13 June 2014, Las Palmas de Gran Canaria.-- 2 pages
Publisher version (URL)http://ivcongresoccm.ulpgc.es/siquimar14/programa
Identifiersisbn: 978-84-697-0471-4
Appears in Collections:(ICM) Libros y partes de libros
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