- 3 days field trip -
Co-organised with IAS
Seismic-scale fluid migration features in a passive margin setting,
Outcrop analogues from the Mesozoic SE France Basin
12-14 June 2018, Sisteron (Provence), France
Jean-Philippe Blouet1*, Patrice Imbert2, Sutieng Ho3*, Andreas Wetzel4
1 Geology Department, University of Fribourg, Switzerland; 2Total-CSTJF, France; 3Department of Geosciences, National Taiwan University, Taiwan; 4 University of Basel, Department of environmental sciences, Bernoullistrasse 32, 4056 Basel
IAS Student members travel funding available by IAS
This field trip will take place in the SE France Basin, which is filled by up to 10 km-thick pile of Mesozoic sediments. These accumulated in a deep embayment that opened onto the divergent, then drifting northern margin of the Tethys Ocean. Several organic-rich intervals were deposited during that period and have locally reached maturity as biogenic or thermogenic (for both oil and gas) source rocks as evidenced by hydrocarbon shows at the outcrop and in boreholes. Although fluid migration study is usually based on petrographic and geochemistry methods, we will develop during this field trip the innovative concept of outcrop scale fluid migration features, namely: sand injectites and seep carbonates and to some extent mass-transport deposits. We will discuss for each of these the related fluid pressure regime, its links to the petroleum systems and inferred seismic analogues of such bodies based on examples from various sedimentary basins.
The aim of the field trip is to extend the significance of these diverse and local features as key markers of the fluid history of basins. The targeted public includes people interested in fluid (petroleum) systems, basin modeling, seismic interpretation, microbial carbonates, chemosynthetic environment etc.
We propose a journey across the basin, starting from the NW margin (Vercors) and ending at the foot of the SE margin (Sisteron), visiting Jurassic and Cretaceous outcrops on the way (see attached poster). The first set of novel outcrops is located in the Diois area. Late Cretaceous seep carbonates are nicely exposed on a ca. 200 m long, 150 m height bluff, which allows the description of mappable clustering pattern. The stacked clusters point down to underlying turbidite channels as possible migration pathways (the related source rock will be observed later in the center of the basin). A second outcrop in that area exposes one of the famous Pseudobioherms of the Terres Noires Formation. This spectacular carbonate mound (20 m thick) differs in several ways from the classic outcrop of Beauvoisin (and other seep carbonates worldwide); the origin of such particularities will be discussed based on facies and petrographic analysis, and linked to hydrocarbon migration mechanisms.
A stop in the center of the basin will allow the participants to examine an 80-m-thick mass-transport deposit (MTD); MTDs are known from geotechnical modeling to detach on intervals of high fluid pressure, making them fluid indicators in a wide sense. In addition, the outcrop will raise the issue of the significance of kinematic indicators and highlight some aspects of the mechanical behavior of sediments shortly after deposition.
Aptian-Albian sand injectites connected with thick sandbodies and cross-cutting the marly Marnes Bleues Fm. will be observed near Sisteron; their association with dispersed columnar and tubular carbonate concretions will be examined based on geometric relationships from a couple of hundred meters to a few kilometers scales.
All along the trip, outcrop examples will be discussed along with seismic sections from various sedimentary basins, in relation with their respective fluid/pressure/petroleum systems.
The trip area is away from it all in many respects, accommodation will be provided in traditional, family-run hotels and restaurants. The highlights include an aperitif in a museum of regional fossils showing world-class specimens.