Depositional systems affect the thickness, geometry, extent, quality of coal seams, and the integrity of the associated roof and floor rocks. Moreover, post-depositional compaction may add complexities to coal seam geometry and impact economic recovery of coal and/or coalbed methane (CBM). Therefore, the evaluations of depositional systems and compactional features are important aspects of coal and CBM exploration and development. The following discussion is a cursory overview that introduces some key issues concerning depositional systems.
Depositional systems are laterally adjacent assemblages of sedimentary facies which are related by depositional processes (Scott and Fisher, 1969). Most coal originated from peat that was deposited as low-energy, coastal plain facies within fluvial (Pictures 1 and 2), strandplain/barrier (Pictures 3, 4, 5, 6, 7, 8, 9), and marine and lacustrine (Pictures 10 and 11) deltaic systems (Fisher and McGowen, 1967; McGowen, 1968; Fisher, 1969a, 1969b; Frazier and Osanik, 1969; Kaiser, 1974, 1978; Kaiser et al., 1978; Frazier et al., 1978; Horne et al., 1978; Ferm and Horne, 1979; Ayers, 1986; Donaldson and Eble, 1991; and Ayers et al., 1994).