Downloaded from http://sp.lyellcollection.org/ by guest on September 29, 2021 Deep-water sedimentation in the Alpine Foreland Basin of SE France: New perspectives on the Gr~s d'Annot and related systems- an introduction PHILIPPE JOSEPH 1 & SIMON A. LOMAS 2 I lFP School/Geology-Geochemistry Division, Institut Franfais du P~trole, 228-232, avenue Napoleon Bonaparte, 92852 Rueil Malmaison Cedex, France (e-mail. [email protected]) 2Baker Atlas GeoScience, Stoneywood Park North, Aberdeen AB21 7EA, UK (e-mail: simon.lomas@bakeratlas, com) The Gr~s d'Annot and geologists, a long-term in the Gr6s d'Annot occurred in the late 1990s love affair! with the development of detailed studies of the architecture of the turbidite sandstone bodies, For over 150 years, the fascinating outcrops of in order to improve the characterization of the Gr+s d'Annot Formation of SE France analogous deep-water subsurface hydrocarbon have attracted the interest of many geologists, reservoirs. During that period and up to the from different countries and from academic as present day, many international teams have well as industrial spheres. As Stanley relates in worked intensively on the Gr6s d'Annot with this volume, the initial interest was stratigraphic complementary approaches, and the purpose of (identification of contemporaneous formations the 2001 'Confined Turbidite Systems' research corresponding to continental to marine settings) conference, jointly organized in Nice by the and structural: the recognition of large displace- IFP and the University of Aberdeen, was to pro- ments of Alpine nappes led to new concepts of mote exchanges between these teams, to establish mountain formation. Concerning the sedimen- the state-of-the-art and to identify new avenues tology of deep marine deposits, major advances for future research. were made in the late 1950s and early 1960s From these studies, and following the classifi- with the progressive emergence of the turbidite cation of Reading & Richards (1994) based on concept and its recognition in the field (Faure- grain size and nature of the feeder system, the Muret et al. 1956; Kuenen et al. 1957; Bouma GrOs d'Annot is now considered as a benchmark 1962; Lanteaume et al. 1967), and the develop- example of a sand-rich delta-fed turbidite system. ment of the first submarine canyon/fan valley Its depositional character was strongly influ- model (Stanley 1961). From that time onwards enced by a predominance of large magnitude the Gr6s d'Annot outcrops were used as a train- flows carrying relatively coarse-grained sand, ing area in the field, with the organization of interacting with significant basin-floor relief numerous meetings and field courses (for induced by alpine tectonics. Its characteristics example Beaudoin et al. 1975; Stanley 1975). are very different from those of canyon-fed sys- Renewal of this research activity was stimulated tems, as in the classic sand-rich 'suprafan' in the 1980s by the upsurge of intensive explora- model (e.g. the present Avon and Calabar sub- tion on continental margins and the emergence marine fans offshore Nigeria), or mud-rich of seismic stratigraphy; the Gr6s d'Annot were channel-levee systems (e.g. Amazon and ZaYre studied in order to help seismic interpretation deep-sea fans). A recent analogue could be the and, at the same time, complementary flume Eastern Corsica fan system recently described experiments of submarine avalanches were by Gervais et al. (in press). The GrOs d'Annot developed for better understanding of turbidity has frequently been used as an analogue for current processes (Laval et al. 1988). The critical sand-rich turbidite hydrocarbon fields where field studies in the 1980s led to the first com- topographic control has played a key role in prehensive palaeogeographic scheme for the defining the reservoir bodies, like in the North Gr6s d'Annot basin sensu lato, based on palaeo- Sea (e.g. Gannet fields and Gryphon field; current directions, onlap orientation and correla- Newman et al. 1993) or on the Brazilian margin tion of key marker levels (Ravenne et al. 1987), (Campos basin; Moraes et al. 2000). which is still largely used at present. In parallel The global study area is located in the French studies, the influence of folding on basin floor departments of Alpes Maritimes, Alpes de Haute topography was recognized (Apps 1985, 1987; Provence and Hautes Alpes. From a structural Elliott et al. 1985). A second renewal of interest point of view it belongs to the Southern Subalpine From: JOSEPH, P. & LOMAS, S. A. (eds) 2004. Deep-Water Sedimentation in the Alpine Basin of SE France: New perspectives on the Grks d'Annot and related systems. Geological Society, London, Special Publications, 221, 1-16. 0305-8719/03/$15.00 © The Geological Society of London. Downloaded from http://sp.lyellcollection.org/ by guest on September 29, 2021 2 P. JOSEPH & S. A. LOMAS +{£~ t f%+ . + + +'--.,+~,)!'E! VO UX+ + + + + +~ .d\, + 6/< C + + < )t t ,,.+ ~ i~f < GAP Embrun t Les Troi., Ev~chi~s Chaluf enton Crystalline and Palaeozoic massifs Upper Eocene - Lower Oligocene + + + + [ +z~+'~"~-~ par-autochthonous formations Upper Eocene - Lower Oligocene >./+ IltlAURES-~ + allochthonous formations 20 km s +ESTEREL +( Thrust fault r'f?-~" + + + + + S' Normal fault and strike slip fault Les Trois Ev6ch6s (~)@ Grand CoyerC)(~)(~) D6me de Barrot (&) Gialorgues (~)(~@ @~) Chalufy (~(~)@@(~ An not (~ (~) (~) (~) @ (~ (~(~ Quatre Cantons(~ Col de la Cayolle Q@ Barreme (~) St. Antonin (Z)® Peira CavaO (~) Col de la MoutiCre(~)(~)@(~) Fig. 1. Structural map of SE France (redrawn from the BRGM 1:1 000000 geological map 1996) and location of outcrops of Gr6s d'Annot and related systems studied in this volume (1 Amy et al., 2 Apps et al., 3 Bourgeois et al., 4 Bouroullec et al., 5 Broucke et al., 6 Callec, 7 Du Fornel et al., 8 Euzen et al., 9 Evans et al., 10 Ford & Lickorish, 11 Garcia et al., 12 Guillocheau et al., 13 Lansigu & Bouroullec, 14 Lee et al., 15 McCaffrey & Kneller, 16 Moraes et al., 17 Puigdeffibregas et al., 18 Smith & Joseph, 19 Stanbrook & Clark, 20 Tomasso & Sinclair). Chains, part of the Alpine Foreland Basin. the geodynamical paper of Ford & Lickorish, Figure 1 displays the structural and stratigraphic deal with the whole system. framework of the Gr6s d'Annot, with the location The remnants of the Upper Eocene-Lower Oli- of the different research areas: a code number has gocene Gr6s d'Annot and related systems (Fig. l) been given to each paper of this volume, and is are located on the para-autochthonous Digne attributed to each research area in the legend of Thrust verging southward in the Castellane Arc, this figure. The two introductory historical and overlain by the allochtonous Embrunais- papers of Stanley and Bouma & Ravenne, and Ubaye Nappes (Autapie and Parpaillon) located Downloaded from http://sp.lyellcollection.org/ by guest on September 29, 2021 NEW PERSPECTIVES ON THE GRI~S D'ANNOT 3 around Barcelonnette. The whole system is (Gulf of Lion), and therefore the shut-off of sedi- delimited by two crystalline and Palaeozoic mas- ment supply from the Corsica-Sardinia massif sifs: Pelvoux to the north and Maures-Esterel to (S6ranne 1999). the south. Two regional structural cross-sections In agreement with the subsidence modelling have already been published (Graham in Elliott of Vially (1994), Apps et al. consider that the et al. 1985, fig. 2.1, and Ford et al. 1999, fig. 2): deformation of the Gr6s d'Annot basin was they differ in the degree of involvement of base- dominated by the SW-directed Alpine thrusting, ment in the alpine thrusts, but both are still local thin-skinned extension (Gialorgues) and largely speculative at depth as no seismic profiles strike-slip faulting (Rouaine) being minor com- or boreholes are available for the area. ponents in an overall compressive setting. They This volume is organized in different sub- consider with Ford & Lickorish that the Meso- themes to reflect the varying approaches of the zoic and Palaeozoic basement (Barrot, Argen- researchers. Here we present an overview of tera) must be involved in this thrusting, even if those themes and try to emphasize where consen- there are a number of structural repetitions of sus has been reached, the new perspectives the Mesozoic cover. In contradiction to previous recently proposed, and key potential areas for interpretations that consider a late exhumation future research. (Late Miocene) of the Argentera area, Apps et aL propose an early uplift of the Barrot Massif, emergent and eroded to its Permian Geodynamic and structural evolution core by the Mid Eocene (Lutetian), and provid- ing an input of clastic material to the basin. Using a global reconstruction of the peri-alpine In this framework, Evans et al. examine the foreland basin from Eocene to Pliocene times, relationship between the westernmost Barr~me Ford & Liekorish highlight the complex trajec- Basin and the other Gr6s d'Annot sub-basins. tory of the Alpine orogenic prism and the varia- The shallow-marine turbidite formation of Gr+s bility of shortening rates through time. During de Ville is time-equivalent to (or slightly younger early collision between Italy (Apulia) and than) the last Gr6s d'Annot deposits (Mid Rupe- Europe in Eocene times, an increasingly arcuate, lian). Evans et ai. show that the Gr6s de Ville is peripheral flexural basin migrated rapidly NW not a feather-edge to the Gr6s d'Annot, but across the European plate. The Early Oligocene accumulated in a narrow thrust-sheet-top basin, was characterized by a decoupling of the oro- separated from the Gr6s d'Annot system by a genic prism from its south-western border synsedimentary anticline. These two distinct (Southern Subalpine Chains) by means of several sub-basins were fed by different sediment trans- transpressive strike-slip faults: for these authors port paths, linked only to the Maures-Esterel the evolution of the Gr6s d'Annot basin is subse- massif (and not to Corsica-Sardinia) in the case quently governed mainly by the gravitational of the Barr~me Basin.