An Example of Coal Wash-Out

Abstract

Coal wash-out of typical fish-tail type has been discovered in Karatsu Coal Mine, Saga Prefecture. This wash-out occurred in the coal seams of the Karatsu Goshaku group of the Yoshinotani formation, which is the main coal-bearing formation of Karatsu Coal Field.
From consideration of this wash-out and other geologic data, the following conclusions are made:
1) This wash-out occurred by contemporaneous erosion during deposition.
2) The qualitative differences between the upper Sasaishi coal group and the Karatsu Goshaku coal group could be attributed to different depositional circumstances.
3) A few cores, from bore holes in the wash-out areas where the Goshaku coal group is absent, consist of thick disturbed deposits with crumpled laminae and intraformational conglomerates in place of the Goshaku coal.
4) These intraformational disturbances are caused by tilting of the bottom of the depositional basin as the result of crustal movements.