The Cape Vogel basin extends for 400 km along the northeast side of eastern Papua New Guinea where it is 80 percent overlain by water, with most of the remaining part covered by alluvium and recent volcanic deposits.

Aeromagnetic data indicate three subbasinal areas within the Cape Vogel basin and another separate basin between the Trobriand and D'Entrecasteaux Islands. These basins are on an overriding plate of oceanic mantle and crust that was thrust southwestward onto the Mesozoic Owen Stanley metamorphic rocks during an earlier period of plate-tectonic adjustment.

Tertiary sedimentary rocks crop out in only two places within the Cape Vogel basin: in the Robinson Bay-loma region, and on Cape Vogel Peninsula. In the Robinson Bay area, the base of the section is the late Oligocene lauga Formation which consists predominantly of volcanic rocks subordinated in the upper part by deep-marine deposits. The lauga Formation is overlain unconformably by the Robinson Bay Limestone of early middle Miocene age. On Cape Vogel Peninsula, limestone 120 m thick forms Castle Hill and overlaps (?)lower Miocene siltstones to rest unconformably on late Oligocene marine volcanic rocks. Correlation between the Robinson Bay and the Castle Hill limestones is confirmed by diagnostic larger foraminifers.

Overlying and locally lapping on to the Robinson Bay Limestone and the uplifted marine volcanic rocks on Cape Vogel Peninsula is a thick (over 4,000 m) section of upper Miocene-Pliocene clastic strata deposited under alternating nonmarine, marginal, and deltaic-marine to open-marine conditions. Pliocene-Pleistocene marginal marine and nonmarine clastic strata and recently uplifted coralline reefs are present locally around the basin margin.

A study of lithologic rock types and microfauna of the Cape Vogel basin indicates a high diversity in depositional environments during the Tertiary. These conditions strongly favor the generation and later entrapment of hydrocarbons in a tectonically active region.