Various authors have recently postulated a thick cover (up to 2 km) over the presently exposed rocks of the Sydney Basin. This paper examines the evidence for such a cover, the various ways in which it might have been emplaced and removed without trace, and the time and space constraints that must be considered. The evidence for a thick cover is poor. Maximum cover was considerably less than 1 km, and heat flow and near‐surface diagenetic processes can account for the variations in coal reflectance and the character of the Hawkesbury Sandstone, both of which are used as evidence of thick cover by some writers.