Changes

==Shale smear factor==

==Shale smear factor==

Lindsay et al. (1993) described outcrop studies of shale smears in a Carboniferous fluvio-deltaic sequence. In contrast to the sequence described by Weber et al. (1978), these rocks were lithified at the time of faulting (burial depth about 2 km). Lindsay et al. (1993) recognized three types of shale smear: shear, abrasion, and injection.

Lindsay et al.<ref name=Lindsay>Lindsay, N. G., F. C. Murphy, J. J. Walsh, and J. Watterson, 1993, Outcrop studies of shale smear on fault surfaces: International Association of Sedimentologists Special Publication 15,  p. 113-123.</ref> described outcrop studies of shale smears in a Carboniferous fluvio-deltaic sequence. In contrast to the sequence described by Weber et al. (1978), these rocks were lithified at the time of faulting (burial depth about 2 km). Lindsay et al. (1993) recognized three types of shale smear: shear, abrasion, and injection.

(1) Shear smears are analogous to those described by Weber et al. (1978; Figure 1). The thicknesses of the smears generally decrease with distance from the source bed, reaching a minimum in the region midway between the hanging-wall and footwall bed terminations.

 

(1) Shear smears are analogous to those described by Weber et al.<ref name=Weber>Weber, K. J., G. Mandl, W. F. Pilaar, F. Lehner, and R. G. Precious, 1978, The role of faults in hydrocarbon migration and trapping in Nigerian growth fault structures: Offshore Technology Conference 10, paper OTC 3356, p. 2643-2653.</ref>([[:File:Shale Smear Factor Fig1.png|Figure 1]]). The thicknesses of the smears generally decrease with distance from the source bed, reaching a minimum in the region midway between the hanging-wall and footwall bed terminations.

(2) Abrasion smears, which are the commonest type in this lithified sequence, comprise a wafer-thin veneer that is abraded by a sandstone wall-rock as it slips past a shale bed. These smears tend to be thickest when derived from thicker source layers and when the fault throw is small. Larger throws tend to erode the shale veneer.

(2) Abrasion smears, which are the commonest type in this lithified sequence, comprise a wafer-thin veneer that is abraded by a sandstone wall-rock as it slips past a shale bed. These smears tend to be thickest when derived from thicker source layers and when the fault throw is small. Larger throws tend to erode the shale veneer.

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http://archives.datapages.com/data/bulletns/1997/06jun/0897/Images/Fig02.GIF

Figure 2-Smear factor algorithms for estimating likelihood of clay smear on a fault plane. (a) Clay smear potential (CSP) (Bouvier et al., 1989; Fulljames et al., 1996) given by the square of source-bed thickness divided by smear distance; (b) generalized smear factor, given by source-bed thickness divided by smear distance, with variable exponents; (c) shale smear factor (SSF) (Lindsay et al., 1993) given by fault throw divided by source-bed thickness. Methods (a) and (b) model the distance-tapering of shear-type smears, whereas method (c) models the form of abrasion smears.

Figure 2-Smear factor algorithms for estimating likelihood of clay smear on a fault plane. (a) Clay smear potential (CSP) (Bouvier et al., 1989; Fulljames et al., 1996) given by the square of source-bed thickness divided by smear distance; (b) generalized smear factor, given by source-bed thickness divided by smear distance, with variable exponents; (c) shale smear factor (SSF) (Lindsay et al., 1993) given by fault throw divided by source-bed thickness. Methods (a) and (b) model the distance-tapering of shear-type smears, whereas method (c) models the form of abrasion smears.

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