Published online by Cambridge University Press: 01 May 2009
Pelagic Foraminifera found in the marginal parts of the limestone at Mount Madai in south-eastern North Borneo indicate that it is of Upper Cretaceous age. Much of the limestone at Mount Madai and Mount Baturong does, however, contain algae and other microfossils characteristic of Lower Cretaceous rocks in other parts of the world.
The limestone is provisionally classified as the Madai–Baturong Limestone Member of the Chert-Spilite Formation. Revision of the stratigraphy has clarified the regional structure, and it is postulated that the Chert-Spilite Formation has been uplifted against Neogene sediments along a major zone of thrust faulting.