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 Li ge D partement de ologie U. . A Es Argiles ochimie et Environnement s dimentaires B1 All e du 6 Ao t Sart Tilman B 000 Li ge
T ODUCT O
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 o modified from agel 200 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
pala ras clave: Minerales de la arcilla, Mineralogía, Isótopos ey words: Clay minerals, Mineralogy, Radiogenic isotope, Marine radiogénicos, Sedimentos marinos; Agentes de transporte sediment, Transport agent. resumen SEM/SEA 2012 * corresponding author: [email protected]
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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 La rador 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 distri ution of main surface currents Dar y 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 asins and modern pathway of deep water variability by changes in their relative masses. Map modified from agel et al. 200 . contribution to particle supplies on the
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M endeleeiv Ridge. During interglacials Springer erlag 621 6 . marine sediments and aerosols: orth the site receives material from erosion Eic en H. radinger . aylord A. Atlantic Earth Planetary Science Mahoney A. igor . and Melling H. Letters 6 . from the Canadian and American margins whereas during glacials the 200 : Sediment transport y sea ice in Hillen rand C.D. Ehrmann W. 200 ): the Chu chi and Beaufort Seas: p articles are mainly derived from the Late eogene to uaternary ncreasing importance due to changing environmental changes in the Antarctic Eurasian margin. We attribute the ice conditions? Deep Sea esearch Part contrasted sedimentary supplies to Peninsula region: evidence from drift : Topical Studies in Oceanography 2 sediments. lo al Planetary Change changes in the position between the 2 1 02. 16 1 1. 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 Ceno oic 200 ): Clay mineral assem lages in data confirm that the sediment ol 1: Methods C. Hillaire Marcel 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 . Hillaire Marcel C. Hum let M. Marine eology 201 1 1 6. 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 P isotope signatures of southeast ndian Ocean sediments Transpolar Drift may be different during the clay si e fraction of La rador Sea transport mechanisms and glacial. sediments during the Holocene: depositional environments. Marine mplications for the inception of the eology 2 1 1 . CO CLUS O modern deep circulation pattern. Petschic . Kuhn . ingele . . Paleoceanography 1 PA 002 1 6 : Clay mineral distri ution in doi:10.102 /200 PA000 . surface sediments of the South In marine sediments clay minerals are agel . De ra ant P. De Menocal P. mainly detrital. They usually derive from Atlantic sources transport and Demoulin B. 1 2): Utilisation des relation to oceanography. Marine several source areas and may be min rau s dimentaires argileu pour la eology 1 0 20 22 . supplied by different transport agents. reconstitution des variations ut erg .L. oldstein S.L. Hemming We propose to combine mineralogical pal oclimati ues court terme en Mer S. . Anderson . . 200 ): Sr isotope and geochemical proxies to trace d Ara ie Oceanologica Acta 1 12 evidence for sources of terrigenous detrital provenance and provide valuable 1 . sediment in the southeast Atlantic agel . nnocent C. Stevenson .K. and information on paleocurrents. Ocean: s there increased availa le e Hillaire Marcel C. 1 : d isotopes as for enhanced glacial productivity? tracers of paleocurrents: a high resolution ACK OWLED EME TS Paleoceanography 20 PA101 study of Late uaternary sediments from doi:10.102 /200 PA000 . the La rador Sea. Paleoceanography 1 en atarathnam K. yan W.B. . 1 1): The author warmly aknowledges SEA . Dispersal patterns of clay minerals in (Sociedad Española de Arcillas) for their agel . Mattielli . 2011 : Holocene the sediments of the eastern invitation to attend the Bilbao SEM-SEA evolution of deep circulation in the Mediterranean Sea. Marine eology meeting in June 2012. northern orth Atlantic traced y Sm d 11 261 2 2. and P isotopes and ul sediment Walter H. . Hegner E. Die mann B. mineralogy. Paleoceanography 26 Kuhn . utgers an Der Loeff M.M. PA 220 . doi:10.102 /2011PA00216 E E E CES 2000): Provenance and transport of ingele . . Schmieder . Petschic . terrigenous sediment in the South von Do enec T. hlemann C. 1 ): Atlantic Ocean and their relations to Biscaye P. E. 1 6 : Mineralogy and Terrigenous flu in the io rande ise glacial and interglacial cycles: d and sedimentation of recent deep sea clay in area during the past 1 00 a: evidence Sr isotopic evidence eochimica the Atlantic Ocean and adjacent seas and of deepwater advection or rapid response Cosmochimica Acta 6 1 2 . oceans eological Society American to continental rainfall patterns. Bulletin 6 0 2. Paleoceanography 1 . Carson B. Arcaro .P. 1 : Control of ingele . . De Dec er P. Hillen rand clay mineral stratigraphy y selective C.D. 2001a : Late uaternary transport in late Pleistocene Holocene fluctuations of the Leeuwin Current and sediments of orthern Cascadia Basin palaeoclimates on the adjacent land uan de uca A yssal Plain: mplications masses: clay mineral evidence. for studies of clay mineral provenance. Australian ournal Earth Science 6 ournal Sedimentary Petrology . 06. ingele . . De Dec er P. Hillen rand Dar y D.A. a o sson M. Polya L. C.D. 2001 : Clay mineral distri ution 200 ): ce rea er e pedition collects in surface sediments etween ey Arctic seafloor and ice data. EOS ndonesia and W Australia source Transactions American eophysical and transport y ocean currents. Union 6 2. Marine eology 1 1 1 6. Die mann B. Petschic . ingele . . ingele . . De Dec er P. irault A. tterer D.K. A elmann A. Brathauer and uichard . 200 : History of the U. ersonde . and Mac ensen A. South ava Current over the past 0 1 6): Clay mineral fluctuations in Late a. Palaeogeography uaternary sediments of the Palaeoclimatology Palaeoecology southeastern South Atlantic: mplications 1 2 260. for past changes of deep water rousset .E. Biscaye P.E. indler A. advection. in: The South Atlantic: Present Prospero . Chester . 1 : and Past Circulation. Wefer et al . eds eodymium isotopes as tracers in