Cretaceous mélange in West Kalimantan and its tectonic implications

Williams, Paul R.; Geophysics, Canberra; Supriatna, S.; Harahap, Bhakti H.

doi:10.7186/bgsm19198606

Cited by 22 publications

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“…In NW Kalimantan, close to the Sarawak border, a second melange belt is exposed and named the Boyan Melange (Williams et al, 1986). Williams et al (1989) considered the Boyan Melange as Late…”

Section: Accepted Manuscriptmentioning

confidence: 99%

A Triassic to Cretaceous Sundaland–Pacific subduction margin in West Sarawak, Borneo

et al. 2017

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Metamorphic rocks in West Sarawak are poorly exposed and studied. They were previously assumed to be pre-Carboniferous basement but had never been dated. New 40 Ar/ 39 Ar ages from white mica in quartz-mica schists reveal metamorphism between c. 216 to 220 Ma. The metamorphic rocks are associated with Triassic acid and basic igneous rocks, which indicate widespread magmatism. New U-Pb dating of zircons from the Jagoi Granodiorite indicate Triassic magmatism at c. 208 Ma and c. 240 Ma. U-Pb dating of zircons from volcaniclastic sediments of the Sadong and Kuching Formations confirm contemporaneous volcanism. The magmatic activity is interpreted to represent a Triassic subduction margin in westernmost West Sarawak with sediments deposited in a forearc basin derived from the magmatic arc at the Sundaland-Pacific margin. West Sarawak and NW Kalimantan are underlain by continental crust that was already part of Sundaland or accreted to Sundaland in the Triassic. One metabasite sample, also previously assumed to be pre-Carboniferous basement, yielded Early Cretaceous 40 Ar/ 39 Ar ages. They are interpreted to indicate resumption of subduction which led to deposition of volcaniclastic sediments and widespread magmatism. U-Pb ages from detrital zircons in the Cretaceous Pedawan Formation are similar to those from the Schwaner granites of NW Kalimantan, and the Pedawan Formation is interpreted as part of a Cretaceous forearc basin containing material eroded from a magmatic arc that extended from Vietnam to west Borneo. The youngest U-Pb ages from zircons in a tuff layer from the uppermost part of the Pedawan Formation indicate volcanic activity continued until c. 86 to 88 Ma when subduction terminated.

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Section: Accepted Manuscriptmentioning

confidence: 99%

A Triassic to Cretaceous Sundaland–Pacific subduction margin in West Sarawak, Borneo

et al. 2017

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“…The Kuching Zone (Haile, ) has an ESE‐WNW trending structural grain (Figure b). It comprises an amalgamation of Paleozoic‐Mesozoic basement rocks and sediments and the Upper Cretaceous Boyan Mélange Complex (Breitfeld et al, ; Metcalfe, ; Williams et al, ). Upper Cretaceous‐Upper Eocene basins and younger basins unconformably cover the Paleozoic‐Mesozoic rocks of the Kuching Zone (Williams et al, , ).…”

Section: Geologic Settingmentioning

confidence: 99%

“…It comprises an amalgamation of Paleozoic‐Mesozoic basement rocks and sediments and the Upper Cretaceous Boyan Mélange Complex (Breitfeld et al, ; Metcalfe, ; Williams et al, ). Upper Cretaceous‐Upper Eocene basins and younger basins unconformably cover the Paleozoic‐Mesozoic rocks of the Kuching Zone (Williams et al, , ). Locally, these are intruded by small‐scale Oligocene‐Miocene stocks (Fuller et al, ; Williams & Harahap, ).…”

Section: Geologic Settingmentioning

confidence: 99%

Cenozoic Rotation History of Borneo and Sundaland, SE Asia Revealed by Paleomagnetism, Seismic Tomography, and Kinematic Reconstruction

Advokaat

Marshall

et al. 2018

Tectonics

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SE Asia comprises a heterogeneous assemblage of fragments derived from Cathaysia (Eurasia) in the north and Gondwana in the south, separated by suture zones representing closed former ocean basins. The western part of the region comprises Sundaland, which was formed by Late Permian‐Triassic amalgamation of continental and arc fragments now found in Indochina, the Thai Penisula, Peninsular Malaysia, and Sumatra. On Borneo, the Kuching Zone formed the eastern margin of Sundaland since the Triassic. To the SE of the Kuching Zone, the Gondwana‐derived continental fragments of SW Borneo and East Kalimantan accreted in the Cretaceous. South China‐derived fragments accreted to north of the Kuching Zone in the Miocene. Deciphering this complex geodynamic history of SE Asia requires restoration of its deformation history, but quantitative constraints are often sparse. Paleomagnetism may provide such constraints. Previous paleomagnetic studies demonstrated that Sundaland and fragments in Borneo underwent vertical axis rotations since the Cretaceous. We provide new paleomagnetic data from Eocene‐Miocene sedimentary rocks in the Kutai Basin, east Borneo, and critically reevaluate the published database, omitting sites that do not pass widely used, up‐to‐date reliability criteria. We use the resulting database to develop an updated kinematic restoration. We test the regional or local nature of paleomagnetic rotations against fits between the restored orientation of the Sunda Trench and seismic tomography images of the associated slabs. Paleomagnetic data and mantle tomography of the Sunda slab indicate that Sundaland did not experience significant vertical axis rotations since the Late Jurassic. Paleomagnetic data show that Borneo underwent a ~35° counterclockwise rotation constrained to the Late Eocene and an additional ~10° counterclockwise rotation since the Early Miocene. How this rotation was accommodated relative to Sundaland is enigmatic but likely involved distributed extension in the West Java Sea between Borneo and Sumatra. This Late Eocene‐Early Oligocene rotation is contemporaneous with and may have been driven by a marked change in motion of Australia relative to Eurasia, from eastward to northward, which also has led to the initiation of subduction along the eastern Sunda trench and the proto‐South China Sea to the south and north of Borneo, respectively.

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“…It comprises five subparallel geologically and geophysically distinct belts. Williams et al [1986,1988] and Tan [1979Tan [ , 1982 The melange and accretionary deposits are unconformably overlain by, or faulted against, two thick, gently deformed Upper Cretaceous and Tertiary sedimentary sequences interpreted as forearc basin fill (Figures 2, 3 and 4) [Hamilton, 1979;Tan, 1979Tan, , 1982Williams et al, 1986Williams et al, , 1988 Figures 2, 3 and 4). Although the stratigraphic succession has been established, the sparsity of diagnostic fossils results in poor age control within the formation [Haile, 1957;Tan, 1979Tan, , 1982.…”

Section: The Melange and Associated Accretionary Deposits Domain Liesmentioning

confidence: 99%

Paleomagnetic data from Sarawak, Malaysian Borneo, and the Late Mesozoic and Cenozoic tectonics of Sundaland

Schmidtke¹,

Fuller²,

Haston³

1990

Tectonics

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Paleomagnetic data from 231 samples from 31 sites in rocks of Upper Jurassic to Miocene age in Sarawak (Malaysian Borneo) reveal a trend of increasing counterclockwise (CCW) declination deflection with age. Six sites in Tertiary hypabyssal intrusions show 8° to 52° of CCW deflection. The intrusion deflected 52° CCW was K‐Ar dated at 26 m.y. (Upper Oligocene), while one deflected 22° CCW gives a 17 m. y. age (Lower Miocene). Three sites in the Upper Eocene to Miocene(?) Silantek Formation show an average 40° of CCW deflection. Prefolding directions, showing 90° of CCW deflection, are isolated in 4 sites (including two positive fold tests) in Upper Jurassic and Cretaceous rocks of the Bau Limestone and Pedawan Formations. A postfolding, Cenozoic remagnetization with an average of 60° of CCW deflection is found in five Bau Limestone sites. Three sites in the Upper Jurassic Kedadom Formation show an average of 50° of CCW deflection. CCW declination deflections found in Mesozoic and Cenozoic rocks as far as 400 km east and 150 km south of Sarawak, in Kalimantan (Indonesian Borneo), also fit the trend of deflection versus age. On the basis of the regional consistency of declination deflection versus age, along with geologic evidence the data are considered to be evidence of a regional (rather than a local block or distributed shear) rotation. The domain of CCW rotation extends into West Malaysia, suggesting that West Borneo and the Malay Peninsula may have been a stable block during the latest Cretaceous and Cenozoic. West Malaysia and Borneo may have had different histories in the rest of the Mesozoic. The data imply up to 108° CCW rotation of Borneo with respect to stable Eurasia, sometime during the Cretaceous and Cenozoic. Cenozoic rotation may also have occurred between Indochina and Borneo. The sense of rotation shown by the data does not support the “propagating extrusion tectonics” model for Cenozoic Southeast Asia.

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Cretaceous mélange in West Kalimantan and its tectonic implications

Cited by 22 publications

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A Triassic to Cretaceous Sundaland–Pacific subduction margin in West Sarawak, Borneo

A Triassic to Cretaceous Sundaland–Pacific subduction margin in West Sarawak, Borneo

Cenozoic Rotation History of Borneo and Sundaland, SE Asia Revealed by Paleomagnetism, Seismic Tomography, and Kinematic Reconstruction

Paleomagnetic data from Sarawak, Malaysian Borneo, and the Late Mesozoic and Cenozoic tectonics of Sundaland

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