Miocene to recent extension in NW Sulawesi, Indonesia. (1st October 2017)

• Record Type: Journal Article
• Authors: Advokaat, Eldert L.; Hall, Robert; White, Lloyd T.; Watkinson, Ian M.; Rudyawan, Alfend; BouDagher-Fadel, Marcelle K.
• Is Part Of: Journal of Asian earth sciences. Volume 147(2017)
• Page Start: 378
• Page End: 401
• Publication Date: 2017-10-01
• Subjects: SE Asia -- Sulawesi -- Extension -- Exhumation -- Tectonics; Earth sciences -- Asia -- Periodicals; Sciences de la terre -- Asie -- Périodiques; Earth sciences; Asia; Periodicals; 555.05
• DOI: 10.1016/j.jseaes.2017.07.023
• Languages: English
• ISSNs: 1367-9120

Abstract

Graphical abstract: Highlights: New microstructural, field observations, and a revised stratigraphy are presented. The Malino Metamorphic Complex (MMC) is metamorphic core complex. Lithospheric extension in NW Sulawesi occurred during the Early – Middle Miocene. The MMC was exhumed by a second phase of extensional uplift during the Pliocene to present-day. This widespread extension is linked to subduction rollback of the Celebes Sea. Abstract: The Malino Metamorphic Complex (MMC) in the western part of the North Arm of Sulawesi (Indonesia) has previously been suggested to be a metamorphic complex exhumed in the Early – Middle Miocene. This idea was based on limited K–Ar and 40 Ar/ 39 Ar age data, but no structural data were presented to provide evidence for the mechanism of exhumation. Here we present new field observations, micro-structural analyses and a revised stratigraphy of NW Sulawesi based on new age data, to provide better constraints on the timing and mechanism of exhumation. The data presented here suggest that the MMC is a metamorphic core complex which underwent lithospheric extension during the Early – Middle Miocene. Although the MMC experienced significant extension, there is no evidence that it was exhumed during this time. There is no contact between the MMC and the Pliocene Ongka Volcanics, contradicting a previously inferred unconformable contact. Pliocene undeformed granitoids intruding the MMC indicate the complex was still at depth during their emplacement. Furthermore, Pliocene and Pleistocene cover sequences do not contain metamorphic detritus. A second phase of extensional uplift was accommodated by brittle faulting from the Late Miocene-Pliocene onwards, during which the MMC was exhumed. This extension is widespread, as indicated by synchronous exhumation of the adjacent Palu Metamorphic Complex in West Sulawesi, and rapid subsidence offshore in Gorontalo Bay. It is linked to northward slab rollback of the southward-subducting Celebes Sea since the Pliocene. GPS data show rapid northward motion of the North Arm of Sulawesi with respect to the Celebes Sea, indicating that this process is ongoing at present day.