Paleoenvironments, paleoclimates and sequences of Westphalian deposits of Lorraine coal basin (Upper Carboniferous, NE France)

Abstract

Facies and sequences of the Westphalian C are identified in cores and well logs of three boreholes and three seismic lines supplied by Conoco-Phillips from the Lorraine coal Basin. The lithofacies associations suggest various paleoenvironments and sequences during the Westphalian C. Decameter-thick sedimentary bodies display alluvial fan deposits in the northwestern border of the basin (Chaumont borehole). Decametric sedimentary bodies constituted either of conglomeratic and sandy facies with cylindrical shape in well logs represent braided river deposits, or alternations of fining and coarsening upward sequences with sandy, silty and clayey facies with bell and funnel shapes in well log correspond to meander river and lacustrine deltaic deposits in the Saulcy and Lorettes boreholes. Three fining upward third order sequences in the center of the basin in the Lorettes and Saulcy boreholes represent a period 1 with braided river deposits, a period 2 with flood plain, lake and meandering river deposits and a period 3 with anastomosed or meandering river deposits.Period 1 is correlated with a subsidence period in the basin and uplift of the borders, period 2 with the maximum fresh water flooding period with flood plain or lake deposits and period 3 with the filling period.The seismic profiles of Conoco-Phillips confirm the tectonic structures described by previous authors in Lorraine Basin. We agree that this basin was a strike-slip basin as demonstrated by previous authors with depocenters near the South Hunsrück and Metz faults from the Westphalian to the Permian. Biomarkers show that paleoclimate changes (wet/dry) of weak amplitude in the equatorial climate could also modify the sedimentation of this basin and act on sequences of second order. Paléoenvironnements, paléoclimats et séquences des dépôts westphaliens duBassin houiller lorrain (Carbonifère supérieur, NE France) Mots clés. -Bassin houiller lorrain, Carbonifère, Sédimentologie, Diagraphies, Sismique réflexion Résumé. -Des faciès et des séquences du Westphalien C ont été identifiés à partir de carottes et diagraphies de trois forages (fig. 3 à 6) et de trois profils sismiques (fig. 7) réalisés par Conoco-Phillips dans le Bassin houiller lorrain (fig. 1). Les associations de lithofaciès suggèrent divers paléoenvironnements et séquences (fig. 9) pendant le Westphalien C. Des corps sédimentaires décamétriques correspondent à des dépôts de cône alluvial sur la bordure NW du bassin (forage de Chaumont). Des corps sédimentaires décamétriques sont constitués soit de faciès conglomératiques et gréseux de forme cylindrique en diagraphie correspondant à des dépôts de rivière en tresse, soit d'alternances de séquence positive et négative à faciès gréseux, silteux et argileux à forme en cloche et en entonnoir en diagraphie correspondant à des dé-pôts de rivière à méandres et de delta lacustre dans les forages de Saulcy et Lorettes. Trois séquences hectométriques positives du troisième ordre (fig. 11) dans le centre du bassin dans les forages de Lorettes et Saulcy pré...

Modelling of the thermal history of the Carboniferous Lorraine Coal Basin: Consequences for coal bed methane

“…In the part of the Lorraine coal Basin that was operated by HBL (Lorraine coal Basin company) close to the Saar, the stratigraphy was established with paleoflora sampled in coal mines and boreholes by HBL geologists and Laveine (1974). In the part of Lorraine without coal mines, the stratigraphy of seismic lines in Lorraine was done in using the logs of boreholes (Izart et al, 2005) and our interpretation. The paleoenvironments were determined from cores and logs of borehole by Izart et al (2005).…”

3D geomodelling combining implicit surfaces and Voronoi-based remeshing: A case study in the Lorraine Coal Basin (France)

“…The LCB is an intra-mountain coal depression formed during the Hercynian Orogeny between Carboniferous and Permian (Donsimoni, 1981) and interpreted as a strike-slip basin (Korsch and Schäfer, 1995;Izart et al, 2005). This context has favoured organic matter-rich clastic deposits.…”

“…The anaerobic decomposition of organic matter in water has produced the coal bearing deposits of the Westphalian and Stephanian age (Carboniferous -equivalent of the Pennsylvanian age in ICS-stage) (e.g. Izart et al, 2005). They consist of intercalated beds in a complex sequence of claystones, sandstones, and conglomerates that show lateral variations both in terms of nature and thickness.…”

A New Tectonic Model for the Late Paleozoic Evolution of the Lorraine-Saar Coal-Bearing Basin (France/Germany)

“…In the Westphalian, sediment supply was mainly from the Hunsrück and the Taunus provenance provinces or broadly speaking from the Rhenish Massif, which has been served as an uplifted shoulder of the rift. Izart et al [14] showed that continental deposits and third to second order sequences of the Lorraine Basin during this stage were mainly controlled by tectonics that generated the accommodation space in the basin during the subsidence and the maximum flooding periods. [14] as clear unconformity.…”