“…In the light of recent investigations on the sedimentary compositions and facies of these strata (Breitfeld & Hall, ; Hennig et al, ; van Hattum, Hall, Pickard, & Nichols, ), we favour the viewpoint that deep marine sediments of the Rajang Group outcropping in the Sibu Zone (Haile, ) formed as a submarine fan along the southern passive margin of the Proto‐South China Sea, and separated by the Lupar Line, the lateral terrestrial equivalent of the Rajang Group can be traced westward to the Kuching Supergroup in the Kuching Zone (Haile, ). By contrast, the Crocker Formation outcropping northeast of the West Baram Line is interpreted to be deposited in a volcanic forearc setting related to the Proto‐South China Sea subduction, although a Palaeogene deep‐water continental margin setting without subduction is also feasible (van Hattum et al, ). However, the spatial configuration of the Proto‐South China Sea and the Eocene spreading centre revealed by the Palawan ophiolites is still unknown, and they may be externally juxtaposed (Keenan et al, ) or the latter being generated within the former (Ilao, Morley, & Aurelio, ).…”