Origin of an enigmatic regional Mio-Pliocene unconformity on the Demerara plateau

Type Article
Date 2015-07
Language English
Author(s) Pattier France1, 2, Loncke L.1, Imbert Patrice3, Gaullier V.4, Basile C.5, Maillard Alexandre6, Roest WalterORCID2, Patriat MartinORCID2, Vendeville B. C.4, Marsset TaniaORCID2, Bayon Germain2, Cathalot CecileORCID2, Caprais Jean-Claude2, Bermell Sylvain2, Sotin Christine7, Hebert Bertil7, Mercier De Lepinay Marion7, 8, Lebrun J. F.9, Marcaillou B.9, Heuret A.9, Droz Laurence10, Graindorge David10, Poetisi E.11, Berrenstein H.11
Affiliation(s) 1 : Univ Perpignan Via Domitia, Ctr Format & Rech Environnements Mediterraneens, UMR 5110, F-66860 Perpignan, France.
2 : UR Geosci Marines, Inst Carnoilfremer EDROME, Ctr Brest, IFREMER, F-29280 Plouzane, France.
3 : Total CSTJF, F-64000 Pau, France.
4 : Univ Lille 1, CNRS, Lab Oceanol & Geosci, UMR 8187, F-59655 Villeneuve Dascq, France.
5 : Univ Grenoble 1, Observ Sci Univ Grenoble, ISTerre, UMR CNRS 5275, F-38400 St Martin Dheres, France.
6 : Univ Toulouse 3, GET OMP, F-31400 Toulouse, France.
7 : CEFREM, Perpignan, France.
8 : TOTAL SA, Paris, France.
9 : Univ Antilles Guyane, St Claude, France.
10 : Univ UBO Brest, Brest, France.
11 : Univ Paramaribo, Paramaribo, Surinam.
Source Marine Geology (0025-3227) (Elsevier Science Bv), 2015-07 , Vol. 365 , P. 21-35
DOI 10.1016/j.margeo.2015.04.001
WOS© Times Cited 5
Keyword(s) Unconformity, Hydrate pockmark, Slide, Contourite, Valley, Canyon, Demerara plateau
Abstract The Demerara plateau, located offshore French Guiana and Suriname, is part of a passive transform continental margin particularly prone to develop slope instabilities, probably in relation to the presence of a free distal border along its steep continental slope. Slope failure occurred at different periods (Cretaceous to Neogene) and shows an overall retrogressive evolution through time. Upslope these failure headscarp, an enigmatic regional MioPliocene unconformity has been discovered through the interpretation of new academic and industrial datasets. The aim of this work is to describe and understand the origin of this surface. Our analysis shows that this unconformity is made of a series of valleys that cross-cut sedimentary strata. Each one of these valleys has a short lateral extent and is closed along two perpendicular directions, which suggests that it could correspond to a highly meandering system, or to some sub-circular depressions. The infill of these features is equivalent to the regional stratigraphic strata found outside the structures, but in a subdued position. This seems to imply that the structures have originated by a local loss of sediments at their base or by sliding processes. Furthermore, these depressions intersect each other through time, while migrating progressively downslope. We discuss a series of hypotheses that try to explain the onset and evolution of these depressions forming the Mio-Pliocene unconformity (Canyons? Slope failures? Contourite moats? Hydrate pockmarks?). Having established that these structures are depressions formed by collapse, and have many similarities with structures recently described in the literature as pockmarks associated with gas hydrate dissolution, we favor this hypothesis. We propose that these hydrate pockmarks form with a mass failure that was triggered by fluid-overpressure development at the base of the hydrate stability zone.
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Pattier France, Loncke L., Imbert Patrice, Gaullier V., Basile C., Maillard Alexandre, Roest Walter, Patriat Martin, Vendeville B. C., Marsset Tania, Bayon Germain, Cathalot Cecile, Caprais Jean-Claude, Bermell Sylvain, Sotin Christine, Hebert Bertil, Mercier De Lepinay Marion, Lebrun J. F., Marcaillou B., Heuret A., Droz Laurence, Graindorge David, Poetisi E., Berrenstein H. (2015). Origin of an enigmatic regional Mio-Pliocene unconformity on the Demerara plateau. Marine Geology, 365, 21-35. Publisher's official version : https://doi.org/10.1016/j.margeo.2015.04.001 , Open Access version : https://archimer.ifremer.fr/doc/00271/38193/