. Bulletin of the Geological Society of America. Geology. SLACK-VEINS OR SOOT-VEINS. 47 to be foreign to the Coal Measures; in most cases the vein stuff comes by descent from the walls. " Slack-veins " or " Soot-veins " in the Coal Measures of western Pennsylvania Of somewhat frequent occurrences in the southwestern part of the Pennsylvania (and perhaps in other seams as well), and brought to light by the mining of the Pittsburg coal seam, are reverse or overlap faults. These faults, while of comparatively small vertical throw, often extend for distances of several thousand
. Bulletin of the Geological Society of America. Geology. SLACK-VEINS OR SOOT-VEINS. 47 to be foreign to the Coal Measures; in most cases the vein stuff comes by descent from the walls. " Slack-veins " or " Soot-veins " in the Coal Measures of western Pennsylvania Of somewhat frequent occurrences in the southwestern part of the Pennsylvania (and perhaps in other seams as well), and brought to light by the mining of the Pittsburg coal seam, are reverse or overlap faults. These faults, while of comparatively small vertical throw, often extend for distances of several thousand feet across the mines. Figure 17 is a. Figure 17.— Vertical Section in Mine at Buena Vista. One-sixtieth natural size. vertical section showing the appearance of one of those overlaps in a mine at Buena Vista, Pennsylvania. This particular fault—a compara- tively simple instance—has been repeatedly driven through and the coal removed from both sides of it for a mile and a half in the southerly direc- tion in which it runs nearly straight from Buena Vista. These over- laps are called slack-veins or soot-veins, because the fault planes where they pass through the coal contain rather compact veins or seams of crushed and ground up coal sometimes several inches in thickness. The veins of soot in this instance occupy the lines or planes between X X' and A B in figure 17. The walls of these slack-veins are often highly slickensided. These slides or overlaps extend above as well as below the coal bed and in many cases they seem to spread or branch out laterally in the overlying rocks, especially in the roof coal and shales, over considerable areas. Where they pass through the latter strata very complex contortions and inversions may generally be seen in association with them. In some instances a slack-vein consists of a number of short and irregular fractures in the coal, accompanied by a complex system of small overlaps crumpling and twisting the coal. That the coal and its ac
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