Sand injectites network as a marker of the palaeo–stress field, the structural framework and the distance to the sand source: Example in the Vocontian Basin, SE France

Abstract

Sand injectites network as a marker of the palaeoestress field, the structural framework and the distance to the sand source: Example in the Vocontian Basin, SE France a b s t r a c t A large sand injectite network is very well exposed in the area of Bevons, Southeast France. The associated sandstone turbiditic channelefill and the host marls are the AptianeAlbian rocks of the Vocontian Basin. The sand injection network is composed of dykes, sills and sedimentary laccoliths ranging in thickness from mm to pluriem. The dykes and sills have vertical and horizontal lengths of up to and over 100 m and 1 km, respectively. Outcrop observations show that the architecture and morphology of the sand injectites in the marls is governed by the local stress field during injection, preeexisting faults, the hosterock lithology, compaction, and distance to the potential sand source(s). The main set of dykes is oriented N50e60 perpendicular to the minimum compressive stress s 3 during sand injection. Two other sets of dykes are intruded along preeexisting synesedimentary faults oriented N140e150 (set 2) and N90 (set 3) during the AptoeCenomanian interval. Sills and dykes thin laterally away from their potential sand sources and thin laterally away from them. The vertical thickness variations of the dykes and wings are more complex, as thinning away from the sand sources is often compensated by thickening toward the palaeoesurface. Based on field observations and measurements, we characterized the 3D architecture of the sand injectites and showed that the injectites probably formed due to a forceful injection from an overpressured sand body sealed by lowepermeability lithologies.

Basement influences on dolomite-hosted vertical sedimentary intrusions in marine erg-margin deposits from the Pennsylvanian of Northern Wyoming (USA)

“…It is worth noting that one set of intrusion orientations could potentially have been created by hydrofracturing of low-permeability intervals while sand was contemporaneously injected through preexisting fractures (c.f. Monnier et al, 2015). Although it is not necessary to explain all orientations of sandstone intrusions by a structural inheritance, the similarity between the pair of dominant orientations documented here and the Midcontinent fault-and-fold zones suggest that most dikes were formed by injection through pre-existing planes.…”

“…As our understanding of the controlling factors on the formation of intrusions and other softsediment deformation improves, it becomes possible to extract key information from their morphology, orientations, geographic distribution, and stratigraphic location (e.g. Obermeier, 1996;Boehm and Moore, 2002;Loope et al, 2013;Monnier et al, 2015). When coupled with detailed sedimentological and stratigraphic analyses, these features can considerably improve models for the structural setting during deposition and burial.…”

Novo Hamburgo Complex formed by hydrothermal, explosive injection of Botucatu erg sand into extensive tracts of Paraná Volcanic Province (S Brazil)

“…Novo Hamburgo Complex sandstones occur throughout the volcanic province and in every examined lava, sediments either silicified or carbonated. Varied geometries of the sandstone bodies include dike, sill, laccolith, lopolith, wing, vertical pipe, breccia (volcanic clast, sandstone matrix), irregular bodies, extrudite and sand volcano (terminology of Hurst et al 2011;Monnier et al 2015;Chan et al 2019). Sandstones and siltites erupted at the surface are included in the injectite complex.…”

Clastic injectites, internal structures and flow regime during injection: The Sea Lion Injectite System, North Falkland Basin

“…In this example, a suite of structures was observed developed at the margins of injectites, including plumose ridges and ridged margins. Furthermore, excellent examples of clastic dyke and sill systems are also documented from the Aptian to Albian sedimentary fill of the Vocontian Basin, France (<0·5 m wide dykes and up to 6 m thick sills; Monnier et al ., ; Ravier et al ., ), the Hind Sandstone Member of the Carboniferous Craven Basin (<1 m wide dykes and up to 2 m thick sills; Kane, ), the upper Tortonian Marnoso‐arenacea Formation, northern Italy (10 to 30 cm wide dykes; Gamberi, ) and the Cretaceous–Palaeocene Moreno Formation of the Panoche and Tumney Hills, California, USA (up to 18 m wide dykes; Vigorito et al ., ; Hurst et al ., , and references therein; Scott et al ., ; Hurst & Vigorito, ).…”