Bandanna Formation

As with the Colinlea Sandstone, the Bandanna Formation is well known from the Denison Trough in the Bowen Basin where it is mined at several locations. It also extends across the Nebine Ridge into the Galilee Basin where it is considered an equivalent of the upper part of the Betts Creek beds (Wells, 1989; Scott et al., 1995). The Bandanna Formation is stratigraphically separated from the Colinlea Sandstone by the coal-poor Peawaddy Formation and the Black Alley Shale (Figure 4). The Bandanna Formation has a wider areal distribution in the subsurface of the Galilee Basin than the underlying Colinlea Sandstone (Figure 3). For example, it is the only Permian coal-bearing formation known to occur in the Powell Depression (in south-west of the Galilee Basin), where it occurs at depths of over 1500 m and contains poorly developed coal seams (Scott et al., 1995).

Coals of the Bandanna Formation range from sub-bituminous to high volatile bituminous, and have vitrinite reflectance (Rv max) from 0.45 to 0.90% (I’Anson, 2013). This is similar to the rank of coals from the equivalent Betts Creek beds.

As for the other Late Permian coal-bearing formations, the extent of coal development in the Bandanna Formation is related to the overall thickness of the unit. The thickest coal seams occur in areas where the host formation is also relatively thick (Scott et al., 1995). In the central-eastern part of the Galilee Basin the Bandanna Formation contains two significant seams of Group IV coals, known as seams A and B. These are planned to be mined at several of the projects currently under development, including Alpha, Kevin’s Corner, South Galilee and China First. Exploration and appraisal around the China First Coal Project has provided useful information on the coal seams of the Bandanna Formation (Waratah Coal, 2011). The A seam is typically one metre thick, with a maximum thickness of about two metres in the west of the project area. It is usually poorly developed and contains many carbonaceous shale and mudstone partings (Waratah Coal, 2011). In contrast, the B seam is the thickest coal seam recognised at this site and is commonly up to five metres thick. Banding is common throughout, especially in the upper three metres, and typically comprises tuffaceous carbonaceous mudstone (Waratah Coal, 2011).

In the South Galilee Coal Project the main coal resource is interpreted to occur within the D1 and D2 seams of the Bandanna Formation. The coal is high volatile, sub-bituminous and mostly dull, with abundant bright bands throughout (AMCI, 2012). There are three main coal plies in these seams which vary in thickness from 0.5 to 4.5 m. Ash content is variable but is commonly high (up to about 40% on air dried basis) (AMCI, 2012).

The Bandanna Formation is the uppermost Late Permian unit in the central-eastern and southern (e.g. Springsure Shelf) parts of the Galilee Basin. It is commonly sub-divided into two units, these being a lower shale-dominated unit and an overlying heterogeneous unit consisting of interbedded calcareous sandstone, sandy limestone, carbonaceous shale and coal (Wells, 1989). The Bandanna Formation is unconformably overlain by the Triassic Rewan Formation in much of the basin, and elsewhere by the Triassic Dunda beds and Clematis Sandstone (Figure 4). The coal seams have a relatively consistent thickness and disposition throughout most of the basin. The Late Permian Bandanna Formation coal measures dip about 3 to 5° west and no major fault offsets are known.

Last updated:
5 January 2018
Thumbnail of the Galilee subregion

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