Source: Leet, L. Don. 1982.
Physical Geology, 6th Edition. Englewood Cliffs, NJ: Prentice-Hall
- a. A natural depression of strata containing a coalbed or other stratified
deposit. CF: depression
b. The lowest part of a mine or area of coal lands. Hudson
c. A general region with an overall history of subsidence and thick
sedimentary section. Wheeler, R.R.
Dictionary of Mining, Mineral, and Related Terms