Latrobe Valley, Victoria, Australia: A world class brown coal deposit

• Published in: International journal of coal geology 1993-09, Vol.23 (1), p.193-213
• Main Authors: Barton, C.M., Gloe, C.S., Holdgate, G.R.
• Format: Article
• Language: English
• Subjects: Coal; Earth sciences; Earth, ocean, space; Exact sciences and technology; Sedimentary rocks
• ISSN: 0166-5162; 1872-7840
• DOI: 10.1016/0166-5162(93)90048-F

The Latrobe Valley brown coalfields are situated some 150 km east of Melbourne in the State of Victoria, Australia. The brown coals of the Latrobe Valley were deposited within the Gippsland Basin of Victoria, Australia, during the Eocene to Late Miocene. The coal forms part of a sequence of essentially non-marine sands, clays and coals, comprising the Latrobe Valley Group. Three stratigraphic units; namely the Traralgon, Morwell and Yallourn Formations in ascending sequence, contain the three main coal seam groups. The seams, which form some of the thickest continuous coal successions in the world, generally accumulated in place, within distinct coal depocentres. The major coal depocentres largely occur to the south of the Latrobe River and west of a marine interface with the Gippsland Limestone. Only the Traralgon seam occurs both below the marine sediments and extends partly into the Latrobe Valley. The depocentres are not generally spatially coincident but have shifted with time, probably due to differential compaction. Facies equivalents to the major coal seams comprise kaolinitic clays with sands predominating towards the marine interface. The clay sequences are interpreted as being thick lacustrine sequences which effectively surrounded the peat swamps and protected them from the more destructive fluvial inputs coming from higher ground beyond the Latrobe Valley edges. As a result, the peat swamps became stabilised for long periods of time and have produced thick brown coal seams. Nutrients were brought into the coal swamps via lateral diffusion from the lakes and by rising groundwater from the underlying aquifer systems of the Traralgon Formation. Towards the central parts of the Latrobe Valley, thin brackish-marine silts are recognized within the terrestrial sequence of the Morwell and Yallourn Formations and these grade laterally eastward into the marine deposits of the Seaspray Group. The marine equivalents of the Traralgon Formation lie further east beyond the Latrobe Valley limits, beneath Bass Strait. In the late Tertiary, the brown coal-bearing strata in the Latrobe Valley were folded, eroded and covered by a “sheet” of Pliocene-Pleistocene fluvial gravels, sands and clays. The major folds are monoclines. The Latrobe Valley coals can be classified as soft brown coal. Their high moisture content (range 48–70%) and therefore low specific energy (net wet specific energy range 5.8–11.5 MJ/kg) makes the coal a low-grade fuel. A wide relative chang