Slickensides are highly polished and/or striated surfaces that form as a result of tectonic movement or differential compaction of sediment. Common to coal-bearing strata, slickensides can occur on practically any plane of weakness subjected to elevated stress. They can be found along joints, cleats, faults, and other structural and sedimentary features and occur in practically all rock types. However, slickensides occur most frequently in finer-grained rock types such as mudstone and shale. Slickensided fractures are often analogous to slips.
Laird et al. (1985) distinguished two types of slickensides in coal deposits of the Western U.S. The first type, referred to as compaction slickensides, form contemporaneously in fine-grained strata near sandstone units. The second variety, referred to as structural slickensides, exhibit higher deformation caused by more intense pressure. Structural slickensides form adjacent to and beneath paleochannels, at depths exceeding 450 m and under the influence of high horizontal stress. The same classification terms are adopted here. However, structural slickensides incorporate a much broader spectrum of genesis.
Figures & Tables
This volume of the “Atlas of Coal Geology” provides 393 images on various subject matters related to coal deposits and coal resource utilization. The supporting text provides an introductory overview of coal exploration, mining, and coalbed methane (CBM) development, followed by discussions on various megascopic aspects of coal geology (microscopic aspects are covered in Volume 2). Because of the vast subject matter, many generalities had to be made in the text. References are included to guide those interested to more detailed discussions. All citations within the document are linked to the detailed reference list for this volume. The overriding theme for this publication is that a picture is worth a thousand words.