Prospecting for clay in the jungles of Borneo: the Belaga Formation, Nanga Sumpa, Batang Ai, Sarawak

This article is a light-hearted account of a geological experience in the jungles of Sarawak, highlighting some of the difficulties encountered during one of my expeditions. The area under investigation was near the Nanga Sumpa Longhouse, located on the Batang Ai River, situated in the Lupar Valley, southwest Sarawak, East Malaysia, on the Island of Borneo. The Layer Member, part of the Belaga Formation, is of Upper Cretaceous age (65-95 million years old) and is composed mainly of metamorphic muds and sands. The sedimentary origins of these slates/phyllites and metagreywackes have been interpreted as distal turbidites. The clay in question was deposited through suspension fall-out during the final stages of turbidite flows. The mission was to locate sites, yielding clay suitable for potting in order to replace the already diminishing supplies, used up by the local Iban people.