Annual report on Sarawak.

Date:
[1959]
Catalogue details

Licence: Public Domain Mark

Credit: Annual report on Sarawak. Source: Wellcome Collection.

    192/282 (page 164)
    GEOLOGY SARAWAK is composed mainly of recently formed rocks. The oldest formations are only about 300 million years old, and so barely one-sixth of the world’s recorded geological history is represented. The most ancient rocks in Borneo are in the west where ‘Sundaland’, a partly submerged extension of continental Asia, builds part of the island. Sarawak includes some of this area, and most of the main rock formations which build Borneo are represented, so Sarawak geological history is a miniature history of the whole island. Some Palaeozoic rocks occur, but Mesozoic and Tertiary deposits predominate; the most extensive and complete formation is the Tertiary, one of the fullest successions of these deposits in the world. A description of the main rock groups appeared in the 1935 Report in this series. The approximate areas of the geological formations that make up Sarawak’s 47,000 square miles are given below: Formation Area (square miles) QUATERNARY 7,100 TERTIARY j Neogene 13,000 1 Palaeogene 18,600 CRETACOUS 5,000 CRETACEOUS and JURASSIC 860 TRIASSIC 4 55 PERMIAN 9 PRE-PERMIAN (?) 28 5 IGNEOUS i,7°o GEOLOGICAL MAPPING A compilation map and a report incorporating the results of all geological work done in Sarawak were prepared in 1939 and will be published in i960. This work was done in co-operation with the geologists of Sarawak Shell Oilfields Limited. Geological information was plotted on maps on a scale of 11250,000 (about 1 inch to 4 miles) and reassessed. The data for Sarawak were