000			02066nab a2200205 4500
005			20260520000254.0
008			260224s2011 xxu
245	0	0	_aDeformation structures in organic-rich shales
260			_a _b _cmayo 2011
270			_a27/05/2011 ; 27/05/2011
300			_a20 p. ; 729-748
520			_aTranscripción del resumen del autor. Seismic images of Upper Jurassic organic-rich siliciclastic rocks are studied along the 2000-km (1243-mi) Norwegian margin. These rocks are considered the main source rock for most of the large oil and gas fields in the North Sea and Norwegian Sea. We report characteristic seismic expressions of thin-skinned gravitational gliding structures that are strata bound to the organic-rich formations. The most characteristic structures are listric faults that offset and rotate the upper part and sole out near the base of the organic-rich zone. These may be present in large areas (10,000 km2 [3861 mi2]), but are usually restricted to tilted areas. The strike of the faults was perpendicular to the downdip direction of the movement of mass, and fault directions can therefore be used as paleodip indicators. Several types of contraction structures are observed, and all are formed at a maximum of a few hundred meters of burial. Although they are not limited to organic-rich shales, such strata-bound structures may help identify organic-rich intervals in basins where their presence is unknown. We suggest that adding organic material to clay leads to reduced permeability. Compaction-related vertical fluid flow may cause fluid overpressure to build up at the base of a less permeable organic-rich layer during early burial. This high fluid pressure zone becomes a low-friction decollement surface on which overlying sediments slide to form characteristic thin-skinned deformation structures.
581			_a5
773	0		_tAAPG Bulletin _g95
942			_cARTICULO
100	1		_aLoseth, Helge _950030
100	1		_aQiu, Nansheng _950031
100	1		_aZhang, Yuan _950032
999			_c182055 _d182055