Rejuvenated marsh and bay-bottom accretion on the rapidly subsiding coastal plain of U.S. Gulf coast: a second-order effect of the emerging Atchafalaya delta |
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| Institution: | 1. Université du Maine, Laboratoire Mer Molécules Santé (MMS), FR CNRS 3473 IUML, Faculté des Sciences et Techniques, 72085 Le Mans, France;2. Fisheries and Oceans Canada, Gulf Fisheries Centre, Science Branch, 343 Université Av., Moncton, New Brunswick E1C 9B6, Canada;3. Université de Nantes, Laboratoire Mer Molécules Santé, FR CNRS 3473 IUML, Faculté des Sciences et Techniques, 44322 Nantes, France;4. Institut des sciences de la mer de Rimouski, Université du Québec à Rimouski, 310 des Ursulines, Rimouski, Québec G5L 3A1, Canada;5. Universitas Padjadjaran, Faculty of Fisheries and Marine Sciences, Jl. Raya Bandung Sumedang KM 21, Jatinangor 40600, Indonesia;1. Stantec, Burnaby, BC, Canada;2. Department of Geography, University of British Columbia, Vancouver, BC, Canada;1. Université de Lyon, CNRS, UMR 5600 - Environnement-Ville-Société, Site ENS de Lyon, Lyon, France;2. IRSTEA – UR MALY, Villeurbanne, France |
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| Abstract: | Sedimentation processes in marshes and bays under the influence of the emerging Atchafalaya delta are described. The Atchafalaya delta is a major geological event in the Holocene history of the Mississippi River delta system because it represents the initial stages of a new delta cycle. The delta has resulted from the capture of the Mississippi River flow by the hydraulically more efficient Atchafalaya River. Using 137Cs and 210Pb dating techniques, maximum sedimentation of delta-flanking environments was found to occur in the bay bottoms and marshes closest to the emerging delta. Marshes directly under the influence of the emerging delta were accreting at rates as great as 1·4 cm y−1 with appreciable mineral sediment inputs. In addition to increasing shoreline progradation, the added sediment is providing nutrients for increased net plant productivity which provides the organic source needed for vertical marsh accretion. Results show that the major area of coastal progradation will be in the immediate vicinity of the delta and along down-drift coasts. Updrift marshes (East Terrebonne marshes) away from the delta are accreting at a slower rate with smaller mineral sediment input and a larger percentage of organic material. These marshes are likely to continue experiencing rapid rates of deterioration. |
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