The Role of Microbial Activity In the Generation of Lower Cretaceous Mixed FE-Oxide-phosphate Ooids from the Provencal Domain, French Maritime Alps

Abstract

Conversely, Fe-oxide-rich ooid cortical layers consist of aggregates of micrometer-size, platelike crystals of hematite that point to an inorganic precipitation. We suggest that the ooidal condensed interval records a long sedimentary history in an open shelf environment subject to a background accumulation of organic-rich, fine-grained sediments. It was periodically interrupted

The Meso–Cenozoic stratigraphic succession of the Col de Braus area (Maritime Alps, SE France)

“…the stratigraphy and sedimentology of Lower Cretaceous condensed deposits, which have been the focus of various recent publications (e.g. Barale et al, 2013;Decarlis & Lualdi, 2008;Pasquini et al, 2004); . the distribution of laterally discontinuous continental deposits at the base of the Alpine Foreland Basin succession (Microcodium Formation), as well as the position of the outcrops with newly reported colonial cold-water corals at the top of the Nummulitic Limestone; and .…”

“…Boussac, 1912;Caméré, 1877;Demay, 1984;Fallot, 1885;Gignoux & Moret, 1937;Hébert, 1877;Kilian & Reboul, 1908;Lanteaume, 1968;Potier, 1877). Over the past decade, detailed stratigraphic and sedimentological analyses have focused on glaucony-and phosphate-rich Lower Cretaceous condensed deposits (Barale, d'Atri, and Martire, 2013;Decarlis & Lualdi, 2008;Pasquini et al, 2004, and discussion by Parize al., 2005;Pasquini and Vercesi, 1999). Different paleontological studies have been dedicated to the fossil-rich Barremian deposits cropping out near Saint Laurent (Bert and Delanoy, 2000;Bert, Delanoy, & Bersac, 2006;Delanoy, 1990Delanoy, , 1992Delanoy, Magnin, Selebran, & Selebran, 1991).…”

“…The hard ground, locally encrusted by serpulids and ferruginous microstromatolites (Figure 2(e)), is covered by a centimetre-thick lag deposit made up of mineralized intraclasts and bioclasts (Hypophylloceras ponticuli, Cymatoceras sp., belemnites). Above, a thin stratigraphic interval (0-1 m), rich in mixed Fe-oxidephosphate ooids is locally present (Barale et al, 2013). This interval is made up of bioturbated ooidal wackestones/packstones (Figure 2(f)), with reworked cephalopods (Acanthodiscus sp., Lytoceras sp., Phylloceratidae, Cymatoceras sp., Duvalia sp.…”

The Col de Braus (Maritime Alps, SE France): an Historical Geological Locality with High Geoheritage Value

“…On the Saint Laurent outcrop, some of the external moulds of these large ammonites are still visible, whereas the internal moulds have been removed by erosion. The deposition of this thin interval corresponds to the drowning of the Provençal shelf in the early Cenomanian, due to a concurrence of eustatic and tectonic factors (Pasquini et al 2004;Barale et al 2013). The overlying Saint Laurent Marl consists of light-gray marls with thin marly limestone interbeds, containing ammonite moulds, belemnites, echinoids, and brachiopods, resulting from hemipelagic sedimentation in slope environment.…”

“…Since then, the Col de Braus has become a "classic" locality for the geology of the Maritime Alps, and has been cited by numerous authors throughout late XIX and XX centuries (e.g., Bellardi 1852; Caméré 1877; de la Harpe 1877; Hébert 1877; Potier 1877; Fallot 1885; Kilian and Reboul 1908;Boussac 1912;Lanteaume 1968;Campredon 1972;Demay 1984). In recent years, stratigraphic and sedimentological studies have been particularly focused on Lower Cretaceous condensed deposits (Pasquini et al 2004;Decarlis and Lualdi 2008;Barale et al 2013). Moreover, the abundant fossil content of the Lower Cretaceous succession has largely attracted the interest of paleontologists.…”