macla nº 16. junio /12 12 revista de la sociedad española de mineralogía Marine Minerals as Tracers of Detrital Provenance and Transport Agent / #ATHAL(E *A+EL ,-. Universit de Lige Dpartement de ologie U.. AEs D Argiles; +7ochimie et Environnement s7dimentaires; B1I; All7e du 6 AoLt; SartDTilman BDN000 Li9ge TODUCTO In marine sediments mineral assemblages may be used to determine the provenance of detrital inputs. In particular clay minerals have been used as a tracer of provenance and transport mechanisms (e.g., Biscaye, 1965; see Fagel, 2007 for a review – Fig. 1). Detrital clay minerals are formed in soils by physical or chemical weathering. Eroded by river, wind or ice they are carried into shallow and deep water masses of the adjacent seas. Their modern distribution pattern on the sea floor provides information on their dispersion by atmospheric or oceanic currents (Gingele et al. 2001a, b). A prerequisite for the reconstruction of transport pathways is the identification of specific source areas on the adjacent continent (Hillenbrand and Ehrmann 2005). Once the relationship between a specific clay mineral assemblage, a given source and a transport agent is established, variations of this assemblage in down-core profiles may be used to detect paleocurrent changes (Diekmann et al. 1996, Gingele et al. 1999, Gingele et al. 2004). However the interpretation of down-core changes in mineral assemblages depends on available information on the modern distribution and sources. The use of clay proxies to reconstruct transport pathways is most efficient in areas characterised by distinct mineralogical provinces (e.g., Gingele et fig. 1. The clay tool RoX ,modified from *agel 200Z. al. 2001a; Moriarty 1977; Fagel et al., 1992; Liu et al. 2003; Venkatarathnan Likely Petschick et al. (1996) has used mineral assemblage since several and Ryan 1971). For instance the the clay mineral assemblages in surface sources and transport processes may be alternation of two distinct clay mineral ocean sediments to outline the extent involved. In that case the distribution assemblages as expressed by their clay and propagation of North Atlantic Deep pattern of clay minerals is not sufficient mineral ratios has been used to trace water into the South Atlantic. to define their provenance (Carson and seasonal monsoon circulation in the Arcaro 1983). The radiogenic isotopic South China Sea (Liu et al. 2003) and However it may be difficult to assign one signature of the detrital sedimentary the Arabian Sea (Fagel et al. 1992). main source area to a specific clay fraction may provide additional palaRras clave: Minerales de la arcilla, Mineralogía, Isótopos Tey words: Clay minerals, Mineralogy, Radiogenic isotope, Marine radiogénicos, Sedimentos marinos; Agentes de transporte sediment, Transport agent. resumen SEM/SEA 2012 * corresponding author: [email protected] macla nº 16. junio /12 revista de la sociedad española de mineralogía 13 constraints to identify the sources and bottom sediment evidences a Central Arctic Ocean trace sediment provenance (e.g., relationship between the clay Grousset et al. 1988, Fagel et al. 1999, assemblage and the current pathway. For Central Arctic Ocean, we focus our Walter et al. 2000, Rutberg et al. 2005, provenance discussion on the relative Fagel and Mattielli, 2011). An enrichment in smectite was contribution of surface currents since in systematicaly observed along the path deep Arctic sea-ice is probably the most In this study we will combine mineral of the Western Boundary Undercurrent important sediment carrier, especially and geochemical proxies to trace (WBUC); i.e. the main current that for clays and silts (e.g., Eicken et al., detrital source and to identify the main carries the NADW masses in the North 2005). For this study we identify the transport agent in two oceanic settings, Atlantic basins. mineralogical and geochemical (trace the North Atlantic and the Central Arctic. and Nd and Pb isotope) signature of a The variation in down-core assemblage Based on this calibration down-core sediment core collected on the and composition will be further used to changes in clay composition and their Mendeleev Ridge, in Central Arctic estimate the temporal changes in isotope signature have been therefore Ocean (Fig. 3). detrital particle supplies. We will use to monitor deep current variability emphasize how this multiproxy through the Holocene. Evolution of approach is powerful to provide smectite/illite ratios and clay fluxes paleoceanographical implications, evidence enhanced supplies by WBUC especially in complex environments. into the Labrador Sea. Changes in the Nd and Pb signatures of clay-size CASE STUD(ES fraction of Holocene sediments provide constraints on the different sources LaRrador Sea and #orth Atlantic Basins areas that supplied the fine clayey particles into the Labrador Sea. We have analysed the mineralogy and Nd and Pb isotope signatures of the clay- Based on sedimentary mixings, our size fraction of several deep sediment isotopic dataset emphasizes significant cores collected in Labrador Sea and shifts in the radiogenic composition of adjacent basins (fig. 2). the sedimentary fractions are evidenced during the last 6 kyr, suggesting a main The cores are located along gyres of the change in the relative contribution of the fig. Location of sediment core in Central Arctic North Atlantic Deep Water (NADW) two major components of NADW, i.e. the and distriRution of main surface currents ,DarRy et components. North East Atlantic Deep water (NEADW) al.; 200\.. and the Danmark Strait Overflow Water According to 230Th and 210Pb Modern distribution of minerals in (DSOW) during the Holocene. stratigraphy, the study interval covers the last 300 kyr. The mineralogy of the silt and sand fractions display pronounced changes in the relative contribution of carbonates (calcite and dolomite) in regard with silicates (mainly quartz and feldspars). Carbonate-rich layers match with interglacial stages. The clay mineralogy of the fine fraction (< 20 µm) is dominated by illite (60- 70%) with no major down-core variation, except some enrichment in kaolinite. The clay mineral distribution alone does not bring any pertinent information on provenance. However our Nd and Pb isotope data measured on the fine detrital fraction display significant changes over glacial/interglacial periods. Based on literature review the various geological terranes outcropping along the Arctic margins were characterised by their radiogenic fingerprints. Since the main sources were identified we interpret the glacial/interglacial fig 2. Location of sedimentary cores in #orth Atlantic Rasins and modern pathway of deep water variability by changes in their relative masses. Map modified from *agel et al.; 200N. contribution to particle supplies on the macla nº 16. junio /12 14 revista de la sociedad española de mineralogía M endeleeiv Ridge. During interglacials Springer^_erlag; 621^6NN. marine sediments and aerosols: orth the site receives material from erosion Eicen H. radinger . +aylord A.; Atlantic Earth Planetary Science Mahoney A. igor . and Melling H. Letters IZ 6. from the Canadian and American margins whereas during glacials the 200: Sediment transport y sea ice in Hillenrand C.D. Ehrmann W. 200): the Chuchi and Beaufort Seas: p articles are mainly derived from the Late #eogene to luaternary (ncreasing importance due to changing environmental changes in the Antarctic Eurasian margin. We attribute the ice conditions? Deep Sea Cesearch Part contrasted sedimentary supplies to Peninsula region: evidence from drift : Topical Studies in Oceanography 2 sediments. +loRal Planetary Change changes in the position between the 2102. N\ 1611. Beaufort Gyre and the Transpolar Drift, agel . ,200: Marine clay minerals; deep Liu . Trentesau A. Clemens; S.C.; Colin; i.e. the two main Arctic surface currents. circulation and climate. n: C. Wang P. Huang B. Boulay S. Our bulk mineralogical and geochemical Paleoceanography of the Late Cenooic 200): Clay mineral assemRlages in data confirm that the sediment ol 1: Methodsd C. HillaireMarcel A. de the northern South China Sea: ernal. Eds Elservier Amsterdam 1 provenances in Central Arctic remain implications for East Asian monsoon 1. evolution over the past 2 million years. close to the Present conditions during agel #.; HillaireDMarcel C.; HumRlet M. Marine +eology 201 116. the earlier interglacials. In contrast the Brasseur . Weis D. and . Stevenson Moriarty K.C. ,1): Clay minerals in limit between the Beaufort Gyre and the 200: #d and PR isotope signatures of southeast (ndian Ocean sediments; Transpolar Drift may be different during the clayDsice fraction of LaRrador Sea transport mechanisms and glacial. sediments during the Holocene: depositional environments. Marine mplications for the inception of the +eology 2\ 11. CO#CLUS(O# modern deep circulation pattern. Petschic . Kuhn +. ingele *.. Paleoceanography 1 PA002 16: Clay mineral distriution in doi:10.102/200PA000. surface sediments of the South In marine sediments clay minerals are *agel; #.; DeRraRant; P.; De Menocal; P.; mainly detrital. They usually derive from Atlantic sources transport and Demoulin; B.; ,1ff2): Utilisation des relation to oceanography. Marine several source areas and may be min7rauX s7dimentaires argileuX pour la +eology 1[0 2022. supplied by different transport agents. reconstitution des variations uterg .L. +oldstein S.L. Hemming We propose to combine mineralogical pal7oclimatihues i court terme en Mer S.. Anderson