SHALLOW-DIPPING FAULTS IN OWEN STANLEY RANGE METAMORPHIC COMPLEX

The range comprises two suites of metamorphic rocks: the predominantly felsic Kagi Metamorphics in the core, and the metabasite Emo Metamorphics along the northeastern and eastern front. It is bounded by the Owen Stanley Fault and associated faults to northeast and east; the bounding faults dip away from the range and separate the metamorphic rocks below from the Papuan Ultramafic Belt (PUB) ophiolite above. We studied a relatively inaccessible and poorly mapped part of the range at 148^oE to 148^o30 E and found evidence of a third metamorphic suite, marked by sub-horizontal extensional faulting. This led us to re-interpret the structure of the range as a stack of shallow-dipping duplexes, formed by thrust faulting but modified by later extension. The protoliths of the Kagi and Emo Metamorphics are Cretaceous sediments and volcanics; these were metamorphosed in the Paleocene. The third metamorphic suite (Amora Conglomerate) is partly derived from Kagi and Emo rocks, and so suggests a post-Paleocene metamorphic event.