SUSPENDED SEDIMENT TRANSPORT NORTHWESTERN MEDITERRANEAN SEA Ciències de la terra Marges continentals Environmental sciences UPPER MONTEREY CANYON Continental margins Earth sciences Ciències ambientals SUBMARINE CANYONS 2010-01-01 AMER GEOPHYSICAL UNION, 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA Global Biogeochemical Cycles Outcrops of old strata at the shelf edge resulting from erosive gravity-driven flows have been globally described on continental margins. The reexposure of old strata allows for the reintroduction of aged organic carbon (OC), sequestered in marine sediments for thousands of years, into the modern carbon cycle. This pool of reworked material represents an additional source of C-14-depleted organic carbon supplied to the ocean, in parallel with the weathering of fossil organic carbon delivered by rivers from land. To understand the dynamics and implications of this reexposure at the shelf edge, a biogeochemical study was carried out in the Gulf of Lions (Mediterranean Sea) where erosive processes, driven by shelf dense water cascading, are currently shaping the seafloor at the canyon heads. Mooring lines equipped with sediment traps and current meters were deployed during the cascading season in the southwestern canyon heads, whereas sediment cores were collected along the sediment dispersal system from the prodelta regions down to the canyon heads. Evidence from grain-size, X-radiographs and Pb-210 activity indicate the presence in the upper slope of a shelly-coarse surface stratum overlying a consolidated deposit. This erosive discontinuity was interpreted as being a result of dense water cascading that is able to generate sufficient shear stress at the canyon heads to mobilize the coarse surface layer, eroding the basal strata. As a result, a pool of aged organic carbon (Delta C-14 = -944.5 +/- 24.7%; mean age 23,650 +/- 3,321 ybp) outcrops at the modern seafloor and is reexposed to the contemporary carbon cycle. This basal deposit was found to have relatively high terrigenous organic carbon (lignin = 1.48 +/- 0.14 mg/100 mg OC), suggesting that this material was deposited during the last low sea-level stand. A few sediment trap samples showed anomalously depleted radiocarbon concentrations (Delta C-14 = -704.4 +/- 62.5%) relative to inner shelf (Delta C-14 = -293.4 +/- 134.0%), mid-shelf (Delta C-14 = -366.6 +/- 51.1%), and outer shelf (Delta C-14 = -384 +/- 47.8%) surface sediments. Therefore, although the major source of particulate material during the cascading season is resuspended shelf deposits, there is evidence that this aged pool of organic carbon can be eroded and laterally advected downslope. In: Global Biogeochemical Cycles, vol. 24 article n. GB4002. AMER GEOPHYSICAL UNION, 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA, 2010. Global Biogeochemical Cycles oai:pumaoai.isti.cnr.it:cnr.ismar/cnr.ismar.bo/2010-A0-031 oai:digital.csic.es:10261/80101 oai:digital.csic.es:84317 oai:diposit.ub.edu:2445/15162 10.1029/2009gb003745 oai:pumaoai.isti.cnr.it:cnr.ismar/cnr.ismar.bo/2010-A0-031 oai:digital.csic.es:10261/80101 oai:digital.csic.es:84317 oai:diposit.ub.edu:2445/15162 10.1029/2009GB003745 10.1029/2009gb003745 true false 0.9 dedup-similarity-result dedup_wf_001::ea69fceeffbe6487f72a05ca0dda23c9 1 Tesi, Tommaso dedup_wf_001::ec4c158a80d98a75f45ca144ec44595b 3 Langone, Leonardo dedup_wf_001::537adef73d1df41a1cb46254a51e4695 10 Heussner, Serge dedup_wf_001::06f0897f42af4bec8fce0dae5239e576 7 Durrieu de Madron, Xavier dedup_wf_001::27a552ebc100abc1e6746cfa6ce9e30b 4 Puig, Pere dedup_wf_001::9c1549390cfa77df47fe57bd7eae2865 6 Nittrouer, Charles A. dedup_wf_001::9722db8312f766ea6f524713190a3352 13 Fabres, Joan dedup_wf_001::6bdc557d3c8e0f030b0ea9bc4457a519 5 Canals, Miquel dedup_wf_001::4440eba7cef121576e456892f594aa9a 12 Drexler, Tina M. dedup_wf_001::49b333a1099b14f9a22af30e54671011 9 Palanques, Albert dedup_wf_001::28b6725a56f913e04b2109e7849d18b8 14 Miserocchi, Stefano dedup_wf_001::0cd66f3fd03fc14ae8a3ea92de3a1f14 8 Calafat, Antoni dedup_wf_001::d1527932f491054ef2bc0ba08a58a96b 11 Davies, Maureen H. corda_______::5917ccec52c3c8e4b329e72e30d84cd6 226354 HERMIONE ec__________::EC::FP7 ec__________::EC::FP7::SP1 ec__________::EC::FP7::SP1::ENV dedup_wf_001::c0412d17f9c1a32682c45cae58dd840d 2 Goñi, Miguel A. 2010-01-01 2010-01-01 AMER GEOPHYSICAL UNION, 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA 2010-01-01 American Geophysical Union 2010-01-01 American Geophysical Union 2010-10-13 American Geophysical Union http://hdl.handle.net/10261/80101 http://hdl.handle.net/2445/15162 http://dx.doi.org/10.1029/2009GB003745 http://hdl.handle.net/10261/80101 http://dx.doi.org/10.1029/2009GB003745 http://puma.isti.cnr.it/dfdownloadnew.php?ident=cnr.ismar/cnr.ismar.bo/2010-A0-031