ABSTRACT: Sedimentary Basin Evolution During Propagating Arc-Continent Collision, PNG

LIU, KEYU, and KEITH A. W. CROOK, Department of Geology, Australian National University, Canberra, Australian Capital Territory, Australia

The oblique collision between the Finisterre arc and the Australian continent at the NE margin of Papua New Guinuinea (PNG) has created a number of isolated basins along the Markham Suture since late Miocene. The basins, were initially formed by the progressive convergence of the irregular plate margins proceeding from projection points (promotories) of initial impingement along the suture. The evolution of the basins is closely related to the various stages of

the arc-continent collision.

In the southeast end of the onshore part of the Markham Suture (146 degrees 30 minutes, 6 degrees 30 minutes) the evolution of a sedimentary basin has been well recorded in the Pliocene-Pleistocene Erap Complex and Leron Formation of the accretionary prism. Initially, a remnant basin which received over 1000 m of deep sea turbidites was enclosed by two plate promotories on the Australian plate around 5 Ma ago. About 3 Ma ago, as the arc-continent collision proceeded, the turbidites were incorporated into the approaching forearc, beneath trench slope basins in which thick submarine fan and slope deposits were accumulated. As collision further progressed, the area was uplifted to form an intramountane basin with the development of over 1,000 m coarse-grained fan-delta sequences.

The lateral migration and transition of sedimentary basins from remnant basins through trench slope basins to intramountane basins along the suture is disrupted by the plate promotories. Therefore, ideal systematic flysch to molasse sediment transition may not be valid during oblique propagating arc-continent collision with concomitant sequential suturing, provided the convergent plates are not aligned perfectly for simultaneously contact along its full length.

AAPG Search and Discovery Article #91015©1992 AAPG International Conference, Sydney, N.S.W., Australia, August 2-5, 1992 (2009)