The clay mineral distribution in sediments between Indonesia and NW Australia has been assessed on the basis of 166 core-top samples. Clay mineral assemblages are closely related to the geology and weathering regime of the adjacent hinterland and allow the distinction of four clay mineral provinces. Three provinces, Western, Central and Eastern Province are situated along the Indonesian Islands Arc, from Sumatra in the west to Timor in the east. Illite is the major clay mineral of the Western and eastern Province, whereas the Central Province abounds with smectite. The fourth province comprises the NW and West-Australian shelf and slope, as well as offshore plateaus and is dominated by kaolinite. Transport of clays by surface and subsurface ocean currents can be observed within the provinces, e.g. with the Leeuwin and West Australian Current in the NW Australian Province and with the outflow of low-salinity water through the Sunda and Lombok straits in the Central Province. Transport of clays across province boundaries is inhibited by strong salinity fronts, with the exception of the boundary between the Central and Eastern Province.