Master of Science (Hons.)
Department of Geology
Clark, B. R., Depositional environment of the Bulli Coal and its effects on quality characteristics, Master of Science (Hons.) thesis, Department of Geology, University of Wollongong, 1992. https://ro.uow.edu.au/theses/2829
The Bulli Coal, the uppermost coal in the lllawarra Coal Measures of the Southern Coalfield of the Sydney Basin, is examined in relation to depositional environment, structure and quality.
Deposited in an upper delta plain/fluvial environment the Bulli Coal was strongly influenced by basement structure. Block faulting in the basement east of the cratonic Lachlan Fold Belt produced structural effects and rapid subsidence of the northern part of the Southern Coalfield allowing sediment incursion into the Bulli Coal peat swamp.
Structurally controlled, the Bulli Coal formed as a large, lobate peat swamp influenced by river systems to the north and south/ southeast. Interbanding of coal and stone in conjunction with dull, high ash coal plies about the southern and western margins of the Bulli Coal indicate frequent periods of sediment influx. A palaeodrainage channel delineated in the Bulli Coal is indicative of flooding episodes throughout the life of the Bulli Coal peat swamp.
Established on a floodplain topography peat accumulation progressed under a lowering water-table until the later stage of the peat swamp when the water-table rose, eventually drowning the swamp and halting peat accumulation.
Water movement in and around the peat swamp and the control on the water-table level by subsidence are reflected in the Bulli Coal properties thickness, ash content, vitrinite (and maceral) composition, phosphorus content and silica/alumina ratio. Sulphur was derived entirely from the organic matter and not influenced significantly by water movement or water-table level.