Annual report on Sarawak.

Date:
[1950]
Catalogue details

Licence: Public Domain Mark

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

    203/230 (page 127)
    The few islands off the coast are small and of little importance. Roads are few, and travel is mainly by sea and river. The climate is warm and humid, day temperatures averaging 85°F. Annual rainfall varies from 100 to 200 inches. Geology. Sarawak occupies an important position in the make-up of the island chains of South-East Asia, its mountain arc of ancient rocks being essentially a prolongation of the Philippine ranges, which continue southwards into northern Borneo, swing gradually south-westwards after entering Sarawak, and then trend west before gradually curving north-west. In the extreme west of Sarawak there is a sudden change in this trend and structures strike north or north-north-east in common with the Malavan regional strike. Sarawak can be subdivided provisionally into three geological areas, reflecting the broad geographical divisions into interior mountains, bordering undulating country con¬ taining isolated mountain groups and low-lying coastal tracts. The mountainous area is formed largely of mesozoic and upper palaeozoic rocks. It appears to consist mainly of hard, crystalline rocks, comprising shale, schist, pliyllite, hornstone, chert, marble, limestone, quartzite and igneous intrusions. Tertiary sediments are best exposed in the undulating country, which rises occasionally to over 2,000 feet. These comprise sandstone, shale, grit, conglomerate and limestone; seams of coal occur and some of the beds are petroliferous. The tertiary sediments are economically the country’s most important deposits, being the source of both the oil and most of the coal. Pleistocene and recent deposits form the low-lying coastal tracts; these are mostly occupied by alluvium and many of the areas are swampy. The sediments vary from soft mud and peat to unconsolidated sands and rare shell banks. Raised beaches are found in some areas, even at a distance from the coast, and there are isolated patches of recent sediments inland representing river and lake accumulations. Igneous rocks occur, and the formation of mineral deposits such as gold, antimony and mercury appears to be genetically related to the igneous activity. However, neither the igneous