--> Abstract: Cleat and Joint Patterns in Some Cretaceous Coal Sequences in Utah and Their Regional Implications, by B. Hucka; #90993 (1993).

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HUCKA, BRIGITTE, Utah Geological Survey, Salt Lake City, UT

ABSTRACT: Cleat and Joint Patterns in Some Cretaceous Coal Sequences in Utah and Their Regional Implications

Cleat and joint characteristics were investigated in 22 active mines in the Book Cliffs, Wasatch Plateau, Coalville, and Emery coal fields. The orientations, variations, spacing, and mineralization of cleats and joints were determined in coal beds and in adjacent clastic rocks. A knowledge of the cleat and joint characteristics can help in mine planning and design, evaluation of mine roof stability, and methane degasification. The cleats in coal beds and

joints in the outcrop rocks in the four coal fields were formed by tectonic forces. Cleat and joint characteristics, such as smooth, planar, or slickensided surfaces; regularity of spacing; continuity of orientation over a large areal extent; plumose structures; and the presence of gouge zones suggest a regional stress field. A relationship also exists between cleats and joints and the regional structure. This relationship is especially evident in the Book Cliffs coal field where butt cleats and minor joints are roughly parallel to the axial trend of a monoclinal fold structure, whereas face cleats and main joints are perpendicular to it. The study also shows that cleats and joints are influenced by the presence of faults. In eleven mines located close to faults in the Wasatch Plateau coal field, the orientation of the fractures are rotated so that the face cleats and major joints more or less parallel the strike of the faults.

AAPG Search and Discovery Article #90993©1993 AAPG Rocky Mountain Section Meeting, Salt Lake City, Utah, September 12-15, 1993.