- GeoRef, Copyright 2004, American Geological Institute. Reference includes data from Bibliography and Index of Geology Exclusive of North America, Geological Society of America, Boulder, CO, United States
The Madai-Baturong limestone member of the Chert-Spilite formation of the Semporna peninsula, on the southeast coast of North Borneo, forms an important marker horizon for more than 20 miles, and contains algae and foraminifera, the latter characteristic of the upper Cretaceous. Species of Globotruncana, Heterohelix, and Praeglobotruncana have been identified. Revision of the age from Miocene to upper Cretaceous clarifies the regional structure, and it seems that the Chert-Spilite formation has been uplifted against upper Tertiary sediments along a thrust fault zone.