Peat accumulates in areas of low relief and gradient, but through geological time, the peat is buried in sedimentary basins and forms coal seams that can be folded by tectonic events. Many coal fields are affected by folds that impact or influence mining methods or CBM development.
Fold styles are numerous and vary from broad, open folds with gentle dips to narrow, closed structures characterized by steeply dipping or overturned beds (Picture 1). Fold wavelengths can vary from many miles to the microscopic scale.
Folding is a primary result of the effects of differential stress and many fold types originate from the effect of horizontal stress (Williamson, 1967). Folds may be classified either genetically or descriptively. The standard types of folds include anticlines, synclines, domes, and monoclines (Pictures 2 and 3). Drag folds may develop in the vicinity of faults. Folds may form also by soft sediment deformation and slumping. Folds are usually derived tectonically or through differential compaction.
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.