Smectite composition as a tracer of deep circulation: the case of the Northern North Atlantic

Fagel, Nathalie; Robert, Christian; Préda, Michel; Thorez, Jacques

doi:10.1016/s0025-3227(00)00123-7

Cited by 44 publications

(23 citation statements)

References 47 publications

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“…Dioctahedral members of the smectite group (montmorillonite, Al‐rich beidellite) typically form through pedogenesis of diverse protoliths under a wide range of environmental conditions (e.g. Fagel et al . 2001), although pure bentonite layers also form through submarine alteration of silicic volcanic ash (Hodder et al .…”

Section: Resultsmentioning

confidence: 99%

Character of sediments entering the Costa Rica subduction zone: Implications for partitioning of water along the plate interface

Spinelli

Underwood

2004

Island Arc

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Sediments deposited off the Nicoya Peninsula advect large volumes of water as they enter the Costa Rica subduction zone. Seismic reflection data, together with results from Ocean Drilling Program Leg 170, show that hemipelagic mud comprises the upper ~ 135 m of the sediment column (ranging from 0 to 210 m). The lower ~ 215 m of the sediment column (ranging from 0 to 470 m) is pelagic carbonate ooze. We analyzed samples from 60 shallow ( < 7 m) cores to characterize the spatial variability of sediment composition on the incoming Cocos Plate. The bulk hemipelagic sediment is 10 wt% opal and 60 wt% smectite on average, with no significant variations along strike; the pelagic chalk contains approximately 2 wt% opal and < 1 wt% smectite. Initially, most of the water (96%) in the subducting sediment is stored in pore spaces, but the pore water is expelled during the early stages of subduction by compaction and tectonic consolidation. Approximately 3.6% of the sediment's total water volume enters the subduction zone as interlayer water in smectite; only 0.4% of the water is bound in opal. Once subducting strata reach depths greater than 6 km (more than 30 km inboard of the subduction front), porosity drops to less than 15%, and temperature rises to greater than 60 ∞ C. Under those conditions, discrete pulses of opal and smectite dehydration should create local compartments of fluid overpressure, which probably influence fluid flow patterns and reduce effective stress along the plate boundary fault.

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Section: Resultsmentioning

confidence: 99%

Character of sediments entering the Costa Rica subduction zone: Implications for partitioning of water along the plate interface

Spinelli

Underwood

2004

Island Arc

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“…Then it increased rapidly in strength shortly after the isotopic stage 2/1 transition (Bilodeau, 1994;Fagel et al, 1997Fagel et al, , 1999, as was also the case for the northeastern North Atlantic (McCave et al, 1995). According to Fagel et al (2001), an increased influence of the DSOW is documented 4.5 kyr ago, on the basis of detailed mineralogical studies on smectites. Conversely, Veiga-Pires and Hillaire-Marcel (1998), on the basis of U-Th data, indicate a slightly older age of emplacement of a present-day sedimentary dynamics, between the end of the Younger Dryas (YD) and 6 to 8 kyr ago.…”

Section: Deep Currents: Previous Studiesmentioning

confidence: 87%

Sources of Labrador Sea sediments since the last glacial maximum inferred from Nd-Pb isotopes

Fagel

Innocent

Gariépy

et al. 2002

Geochimica et Cosmochimica Acta

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“…Mechanical weathering of polymictic rocks, which are typical of subduction complexes and collisional orogenic belts, produces clay-mineral assemblages (at mid-latitudes) that are enriched in detrital illite and chlorite, with modest amounts of smectite and kaolinite (Griggs & Hein 1980;Karlin 1980;Naidu & Mowatt 1983;Hathon & Underwood 1991). Minerals of the smectite group are widely regarded as the key tracers for volcanic sources (Parra et al 1986;Petschick et al 1996;Fagel et al 2001). Although some varieties of smectite form through hydrothermal and/or submarine alteration of basalt and volcanic ash, the most widespread origins for expandable clay in Holocene sediments are meteoric weathering and pedogenesis of volcanic-rich substrates (Karlin 1980;Parra et al 1985;Chamley 1989).…”

Section: Generic Clay Provenancementioning

confidence: 99%

Late Cenozoic evolution of the Nankai trench-slope system: evidence from sand petrography and clay mineralogy

Underwood

Fergusson

2005

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Submarine slope systems in subduction zones evolve in response to a combination of tectonic and sedimentary forcing. It can be difficult to determine how and when tectonic forcing affects sedimentation, especially when investigating ancient rock successions, but one of the more reliable indicators is a change in sediment composition. During Leg 190 of the Ocean Drilling Program, sandy turbidites were recovered from a Quaternary trench wedge (Nankai Trough), a Pliocene-Pleistocene slope basin, the underlying Pliocene-Miocene accretionary prism, and a Miocene turbidite facies in the Shikoku Basin. Differences in detrital provenance between the sand and clay-sized fractions indicate that turbidity currents did not follow pathways of suspended-sediment transport during the past 10 Ma. During the middle and late Miocene, the sand probably was eroded from a newly exposed accretionary complex (Shimanto Belt). In contrast, high contents of detrital smectite in Miocene mudstones (> 50 wt% of the <2 fxm size fraction, relative to illite, chlorite + kaolinite, and quartz) point to a strong volcanic component of suspended-sediment input (Izu-Bonin island arc). The sand in accreted Pliocene turbidites was also eroded from the Shimanto Belt and transported by transverse flow down the insular slope. The trench-wedge facies then switched to axial flow during the Quaternary, when the sand supply tapped a mixed volcanicmetasedimentary provenance in the rapidly uplifted Izu-Honshu collision zone. Progressive depletion of smectite during the Pliocene and Pleistocene (<20 wt%) points to increased movement of illite-and chlorite-rich clay toward the east and NE from sources on Kyushu and Shikoku. That shift in mud composition coincides with intensification of the North Pacific western boundary current (Kuroshio Current) at approximately 3 Ma. Overall, the depositional system in the Nankai Trough and Shikoku Basin shifted its sand sources because of regional tectonics, whereas the suspendedsediment budget was modulated by hemispheric changes in ocean-water circulation.

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Smectite composition as a tracer of deep circulation: the case of the Northern North Atlantic

Cited by 44 publications

References 47 publications

Character of sediments entering the Costa Rica subduction zone: Implications for partitioning of water along the plate interface

Character of sediments entering the Costa Rica subduction zone: Implications for partitioning of water along the plate interface

Sources of Labrador Sea sediments since the last glacial maximum inferred from Nd-Pb isotopes

Late Cenozoic evolution of the Nankai trench-slope system: evidence from sand petrography and clay mineralogy

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