--> Papua New Guinea: Mesozoic Rift Basin Evolution and Its Control on Basin Fill

International Conference & Exhibition

Datapages, Inc.Print this page

Papua New Guinea: Mesozoic Rift Basin Evolution and Its Control on Basin Fill

Abstract

Much of the recent exploration in the Cenozoic fold-thrust belt (FTB) and associated foreland in Papua New Guinea (PNG) has focused on Jurassic to Lower Cretaceous strata that comprise the reservoir, source and seal for a significant hydrocarbon system. These strata were deposited in a Mesozoic rift basin that formed along the northern margin of the Australian plate, and stratal architectures reflect basin evolution. Seismic data is typically of limited use, however extensive drilling results constrain basin evolution and fill. There is a relative abundance of well data for late syn-rift to post-rift strata, whereas depth to basement and earliest syn-rift strata are not well constrained. Subsidence histories from wells in the FTB demonstrate that rifting likely began in the early Jurassic, and propagated from southeast to northwest. The evolution of the rift basin controlled spatial variability of accommodation generation rates, as well as the total amount of accommodation which, in turn, strongly influenced depositional patterns. Syn-rift Callovian to lower Tithonian strata are generally thicker to the southeast, however units within these strata (e.g., the “Koi Iange sandstone”) display locally rapid changes in thickness, vertical stacking and facies. Latest syn-rift strata, including deltaic deposits of the Iagifu and Hedinia units, are generally restricted to an area of higher accommodation in the southeastern FTB. Upper Tithonian to Valanginian post-rift strata are more laterally continuous and include the wave-dominated shoreline and estuarine deposits of the Toro and Digimu Sandstone units. These strata contain several aggradationally stacked shallow marine sequences in the southeast FTB, whereas the equivalent strata to the northwest show strong progradation during the latest Barriasian, probably reflecting lower amounts of available accommodation in that area. Importantly, Mesozoic rift basin architecture in PNG, expressed as the thickness of its sedimentary fill, is coincident with changes in morphology of the Cenozoic FTB and could have served as an important control on deformational style.