The stratigraphy, structure and tectonics of the Kukukuku Lobe : Permit 22, Papua

The Kukukuku Lobe is a complex uplift of Miocene sediments. This uplift basically represents the inversion of a deep, marine trough - the Aure Trough - in which volcanic sandstones, mudstones and conglomerates - the Aure Group - accumulated to a thickness at least of the order of 10,000 meters during the Lower Miocene and early Middle Miocene. The argillaceous Toa Group (late Middle Miocene-Upper Miocene; 3,000 m.) overlies the Aure Group and is overlain in turn by the Era Group (Pliocene; 2,200 m.). These units were deposited marginally to an uplifted area of the Aure Group and were in large part derived from the Aure Group. The tectonic history of the Kukukuku Lobe is traced by means of detailed stratigraphic and structural analyses, which reveal a sequential pattern of westward migrating depositional troughs (subsidence), followed a phase behind by westward migrating uplift and folding. The uplift and folding are oldest along the eastern side of the Kukukuku Lobe (Lower Miocene) and youngest along the western side (post-Pliocene), indicating a long-lived and essentially continuous deformational history. The Kukukuku Lobe forms the eastern leg of the Purari Orocline, and the tectonic development of the Lobe - from the earliest-formed sedimentary trough to the latest deformation - records the manner and mechanisms by which the Purari Orocline has formed. The Purari Orocline is placed in a regional geological context by reviewing the gross tectonic framework of New Guinea, and the stress system which gave rise to both the Purari Orocline and the Kukukuku Lobe is identified. This stress system is then related to the regional tectonic pattern of New Guinea and the southwest Pacific.