Lengguru, Irian Jaya: prospect selection using field mapping, balanced cross-sections, and gravity modelling

Moffat, D. T.; Henage, Lyle F.; Brash, R. A.; Tauer, R. W.; Harahap, Bhakti H.

doi:10.29118/ipa.603.85.106

Cited by 2 publications

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“…The local sea‐level curve shows a change from deeper water conditions (50–100 m) to shallower water conditions (0–10 m) between the Early to Late Pliocene (Gold, Burgess, et al, ; Gold, White, et al, ; Figure d), the removal of early Pliocene to Mesozoic sequences due to erosion—as recorded in various hydrocarbon exploration wells (cf. Figure 18 in Gold, White, et al, ) as well as in regional offshore seismic imagery (e.g., Bailly et al, ; Pairault et al, ). Our structural and geochronological data combined with these other data sources confirms the suggestion that the Lengguru Fold Belt must have developed due to a young (5–3 Ma) episode of crustal shortening (e.g., Decker et al, ; Dow et al, ; Moffat et al, ; Pieters et al, ; Visser & Hermes, ), rather than an earlier episode at ca. 11 Ma (e.g., Bailly et al, ; Francois et al, ).…”

Section: Discussionsupporting

confidence: 83%

“…The folded units are overlain by the various facies of the Plio‐Pleistocene Steenkool Formation, some of which contain clasts of Eocene and Miocene carbonates. These rocks are age equivalent to the Klasaman Formation found in the Bird's Head and the Buru Formation found in the Central Range (Brash et al, ; Moffat et al, ).…”

Section: Geologic Settingmentioning

confidence: 89%

“…This mountain belt is known as the Central Range in the Bird's Body and the Lengguru Fold Belt in the Bird's Neck (Figure ). The work that is presented here focusses on the Wandamen Peninsula, considered here to be a component of the Lengguru Fold Belt (Moffat et al, ; Pieters et al, ; Visser & Hermes, ; Figure ). The peninsula is essentially located between the Bird's Head Peninsula, the Bird's Neck, and the Bird's Body (Figure ).…”

Section: Geologic Settingmentioning

confidence: 99%

“…11 Ma (e.g., Bailly et al, ; Francois et al, ) while others propose folding occurred much later at ca. 5 Ma (Decker et al, ; Dow et al, ; Moffat et al, ; Pieters et al, ; Visser & Hermes, ).…”

Section: Geologic Settingmentioning

confidence: 99%

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Tectonic Mode Switches Recorded at the Northern Edge of the Australian Plate During the Pliocene and Pleistocene

et al. 2019

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We report new data from medium-high grade metamorphic rocks found at the northern margin of the Lengguru Fold Belt in West Papua. The study involved a systematic analysis of cross-cutting structures to establish the relative timing of deformation, together with isotopic dating to define when these tectono-thermal events occurred. These data show that the region underwent multiple episodes of deformation within the last six million years. Metamorphic mineral growth was associated with the development of ductile shear zones. This episode occurred during a phase of crustal stretching associated with the formation of a metamorphic core complex. Metamorphic zircon growth at 4.9 to 5.3 Ma was documented in two of the dated samples. These data are interpreted to postdate the peak pressure and temperature conditions of the phase of regional crustal stretching. The shear fabrics associated with the metamorphic core complex were later overprinted by at least two generations of folds. The change in mode from crustal extension to shortening reflects a tectonic mode switch. A subsequent mode switch is documented by numerous brittle extensional faults that cross-cut the earlier formed ductile fabrics. We interpret ca. 0.75-1.51 Ma (U-Th)/He age data to reflect cooling associated with the later stages of crustal shortening (marked by folds) or the later extensional unroofing of the peninsula. This work demonstrates that an orogen can record multiple tectonic mode switches within several million years. These outcomes should be considered in studies of ancient orogens where analytical uncertainties associated with isotopic dating may mask short-lived mode switches.Plain Language Summary How much time is required for a mountain belt to develop? Our knowledge of mountain building is somewhat limited because many of the best-studied mountain belts are quite old and our ability to date tectonic events is less precise the farther back we look through time. The work presented here investigates a mountainous peninsula that developed at the northern margin of the Australian Plate within the last six million years. This region records multiple episodes of deformation-we show that the relatively young rocks have been stretched, then pushed together and then stretched again (much like an accordion). These cycles must occur over a period of one to two million years, which is very fast compared to numerous studies of ancient mountain belts that consider the same processes occur over tens of millions of years.

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Section: Discussionsupporting

confidence: 83%

Section: Geologic Settingmentioning

confidence: 89%

Section: Geologic Settingmentioning

confidence: 99%

Section: Geologic Settingmentioning

confidence: 99%

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Tectonic Mode Switches Recorded at the Northern Edge of the Australian Plate During the Pliocene and Pleistocene

et al. 2019

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Cenozoic SE Asia: reconstructing its aggregation and reorganization

Packham

1996

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Reconstructing SE Asia in the Cenozoic is dependent on being able to model three major tectonic events and their consequences. They are the collision of India with Eurasia, the rotational history of the Philippine Sea plate and the ongoing collision of Australia with eastern Indonesia. Models of the Eocene India-Eurasia collision imply extrusion along major strike-slip faults or crustal thickening and block rotation. Kinematic modelling of the present day tectonics of central Asia indicates rotations and strike-slip faulting and an eastward displacement of crust. Prior to middle Miocene time tectonic activity was closely associated with the collision zone and extrusion of Indochina was supposed to have occurred. Analysis of the volume of the topography formed by the collision indicates eastward displacement and the loss of some crust by expulsion or into the mantle. Palaeomagnetic measurements have found northward displacement of Tibet and strong clockwise rotation east of the eastern syntaxis but unequivocal evidence of southward displacement is rare. Large Palaeogene to early Neogene displacements on strike-slip faults have been documented and related with confidence to the rotations that formed at least the Oligocene South China Sea floor. Early Oligocene docking of the Indoburman Flysch belt south of the eastern syntaxis is difficult to explain in extrusion models. Whether the rotations that have been documented are a response by internal deformation or block rotation is unresolved, as is the amount of extrusion of SE Asia to the south. In the eastern region, rotation and associated northward motion of the Philippine SEa plate as it developed puts constraints on possible models because of a maintained close proximity of its southern margin to the northern edge of the Australian craton. Assembling of continental fragments now in the Banda Sea and derived from eastern New Guinea appears to have occurred by Late Cretaceous time. Formation of the Banda arc may have isolated the Banda Sea from the Australia plate then collision of the Australian margin possibly rotated the Banda Sea counter-clockwise. Although westward movement of the Philippine Sea plate relative to Australia commenced in the early Miocene, convergent left-lateral shear was not possible until the late Miocene thus limiting westward tectonic transport of terranes and the transmission of the shear into the region west of the Banda Sea.

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Lengguru, Irian Jaya: prospect selection using field mapping, balanced cross-sections, and gravity modelling

Cited by 2 publications

References 0 publications

Tectonic Mode Switches Recorded at the Northern Edge of the Australian Plate During the Pliocene and Pleistocene

Tectonic Mode Switches Recorded at the Northern Edge of the Australian Plate During the Pliocene and Pleistocene

Cenozoic SE Asia: reconstructing its aggregation and reorganization

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