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The AAPG/Datapages Combined Publications Database

CSPG Bulletin

Abstract


Bulletin of Canadian Petroleum Geology
Triangle Zones and Tectonic Wedges: A Special Issue
Vol. 44 (1996), No. 2. (June), Pages 400-409

Recent Triangle Zone Deformation in Papua New Guinea

Daniel Mark Medd

ABSTRACT

The Puri Anticline of Papua New Guinea was first recognized in 1937 and later drilled during 1957-59 with limited success. New seismic data has been interpreted to suggest that the structure is located within a triangle zone which extends for 45 kilometres along the leading edge of the Papuan fold belt. The stratigraphy and structure of the Puri triangle zone is now better understood due to the recent acquisition of seismic, radar and aerial photography data combined with detailed surface geologic mapping.

The leading-edge structure in the Puri region undergoes a transformation from a relatively simple duplexed wedge to a more highly deformed structure with interpreted out-of-sequence thrusting within its core. This represents a transition from blind, triangle-zone type deformation to emergent thrusting along the leading edge of the Papuan fold belt.

The stratigraphy involved in the triangle zone structure both predates and is synchronous with the formation and encroachment of the Papuan fold belt. The Eocene to Miocene carbonate section, which forms the competent core to the structure, represents a period of relative tectonic quiescence, prior to any significant uplift of the fold belt. With Late Miocene initiation of tectonism, material is shed from the uplifted mountain belt into the developing foreland basin resulting in the deposition of marine flysch claystones. As the deformation front approached a transition to nonmarine, predominantly arenaceous deposition occurred.

RESUME

L'anticlinal Puri, Papouasie-Nouvelle-Guinee, a ete decouvert en 1937 et fore plus tard entre 1957 et 1959 avec succes limite. De nouvelles donnees sismiques ont ete interpretees pour suggerer que la structure est situee dans la zone triangulaire qui s'etend pendant 45 km le long de la marge frontale de la zone orogenique papoue. La stratigraphie et la structure de la zone triangulaire Puri est maintenant mieux comprise a cause l'acquisition recente de donnees sismiques, de radar et de leves aeriens ainsi que des cartes detaillees de la geologie des formations superficielles et des horizons superieurs des couches sous-jacentes.

La structure de la marge frontale dans la region Puri subit une transformation allant d'un prisme en duplex relativement simple a une structure avec une deformation bien plus importante contenant un chevauchement qui ne suit pas la sequence dans son noyau selon l'interpretation. Ceci represente une transition passant d'un type de transformation d'une deformation de zone triangulaire couverte jusqu'au chevauchement surgissant le long de la marge frontale de la zone orogenique papoue.

La stratigraphie de la structure de la zone triangulaire en question est d'un age qui precede et qui est synchrone a la formation et a l'empietement de la zone orogenique paopue. La section de carbonate s'echelonnant d'Eocene a Miocene, qui forme le noyau competent a la structure, represente une periode tectonique relativement de repos, qui precede tout soulevement significatif de la zone orogenique. Avec l'initiation des mouvements tectoniques dans le Miocene tardif, le materiel est depouille de la zone montagneuse soulevee jusqu'au bassin de l'avant-pays en developpement ce qui donne des depots de flysch marin en argilite. A measure que le front de la deformation se rapprocha, une transition des depots non marins surtout d'arenite se produisa.

Traduit par Marie-Louise Tomas


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