Jaime S. Curry¹, Juan M. Lorenzo¹, Geoff W. O'Brien²
(1) Louisiana State University, Baton Rouge, LA
(2) Australian Geological Survey Organisation, Australia

Abstract: Polarity of continent-island arc collision since late Miocene: Timor Sea, N.W. Shelf, Australia

Late Miocene-to-Recent collision of the NW Australian shelf with the Outer Banda Island Arc results in downward flexing of Australian lithosphere toward the arc. Normal faulting on the Australian Shelf occurs as flexural stresses exceed the plate strength. The vertical extent of normal faulting on the shelf from SW of Timor Island to south of Tanimbar Island (123.5°E to 133°E longitude) indicates that collision began in the west in late Miocene. Data includes ~5000 km of 2-D, 6-s seismic reflection profiles and 35 well log suites from the Australian Geological Survey Organisation.

Collision apparently began west of Timor Island in the late Miocene, progressed eastward during the Pliocene, and continues eastward. Normal faults west of 124.5°E terminate vertically in the Miocene section. Normal faults from 124.5°E to 125.5°E terminate at the Miocene-Pliocene boundary. From 125.5°E to ~128°E, faults terminate in the early Pliocene section. Normal faults from ~128°E to 131°E terminate at or near the sea floor. East of 131°E, motion of Australian lithosphere is subparallel to the plate boundary and no faulting is evident. Rates of fault movement and offset on faults also decrease eastward. Anomalous faulting occurs on the shelf (Cartier Trough) and is probably due to Permian salt withdrawal beginning at the onset of collision.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana