Colinlea Sandstone

The Late Permian Colinlea Sandstone is stratigraphically equivalent to the lower to middle part of the Betts Creek beds (Figure 4), but only occurs in the eastern and south-eastern parts of the Galilee Basin (Figure 3). The formation is continuous across the Nebine Ridge into the Bowen Basin (Figure 5), where the unit is more widely recognised (Scott et al., 1995).

The Colinlea Sandstone is predominantly a fine- to medium-grained quartz-rich sandstone, with thick to medium bedding in most of the sequence, apart from near the top where thinly bedded (laminated) sandstone and minor siltstone occurs (Wells, 1989). Near the base, the formation also contains pebbly quartz sandstone that, in places, grades to conglomerate. Distinct coal layers (mostly from about 0.5 to 6.0 m thick) occur in the Colinlea Sandstone of the Galilee Basin, particularly in the central-eastern part of the basin where much of the major coal mine development is expected in coming decades. For example, at the Alpha Coal Project coal seams C, D, E and F are all interpreted to belong to the Colinlea Sandstone, whereas the A and B seams are assigned to the overlying Bandanna Formation (Hancock Prospecting, 2010). Similar nomenclature for the A to F coal seams of the Colinlea Sandstone and Bandanna Formation is also followed at several other coal deposits in the Galilee Basin; for example, Kevin’s Corner and China First (see Section 1.2.3 for further details).

The C seam in the Colinlea Sandstone is one of the main coal seams planned to be mined at Alpha, and it has an average cumulative thickness of 3 m. There are three distinct plies in the C seam (C1, C2, C3) consisting of dull to dull banded coal with claystone partings (Hancock Prospecting, 2010). Ash content ranges from less than 10% in some plies, but is more commonly greater than 20%.

The D coal seam in the Colinlea Sandstone at Alpha, which consists of three main plies, is mostly 6 to 7.5 m thick (including stone bands). This equates to about 4.5 m of clean coal (Hancock Prospecting, 2010). Stone bands in the D seam are usually thicker in western parts of the Alpha deposit, and thin towards the east.

In contrast to the central-eastern basin, in the south there is only minor coal seam development within the Colinlea Sandstone. The Colinlea Sandstone thins progressively westwards across the Springsure Shelf, and does not occur in the southern, western or northern parts of the basin (Figure 3).

Last updated:
5 January 2018
Thumbnail of the Galilee subregion

Product Finalisation date