Mount Thorley Warkworth

Geology

Australia's oldest deposits of black coal, found in New South Wales and Queensland, are of Permian Age and were formed 285 to 245 million years ago. However, younger black coals mined in Queensland, South Australia and Tasmania are between 140 and 180 million years old. Victoria's brown coal deposits are young by comparison, formed less than 45 million years ago.

MTW's mining operations are centred in the Upper Hunter Coalfield and form part of the larger coalfield known as the Sydney Basin.

The Sydney Basin comprises sedimentary rocks such as conglomerate, sandstone and shale interbedded with many coal seams. Several claystones of volcanic origin occur within the sequence and, due to their consistency, are used as major stratigraphic (distinct layers of rock) horizons. The basin is structurally stable with relatively few geological faults and volcanic intrusions and is one of the world's most significant coal bearing basins.

Coal seams currently mined at MTW are from the Wittingham Coal Measures of Blakefield, Glen Munro, Woodlands Hill, Arrowfield, Bowfield , Warkworth and Mt Arthur.  These seams vary in thickness from 0.3 metres to more than 6.0 metres.