Among these sequences, the Early Cretaceous parts (Urutawan–Motuan) contain spilites and keratophyres within greywacke-type detritus and conglomerates (Battey 1950; Ash 1970; Hay 1975), whilst the Late Cretaceous lithologies are predominantly basalts, dolerites, and microgabbros, with minor amounts of sediment (Le Couteur 1967; Hay 1975).
Source: wiktionary