Rapid Exhumation of the Eastern Central Range of Taiwan: Constraints from Brittle Deformation Patterns.
Abstract
Taiwan marks the collision between the Luzon volcanic arc and the passive margin of Eurasia. Recent geochronology work suggests that starting 1-0.5 Ma, Taiwan experienced an acceleration in uplift rates to as much as 8mm/yr. To understand how such rapid exhumation is accommodated, we focus on brittle structures in stream exposures spanning >100 km of the eastern Central Range along strike. Outcrop-scale faults and well-developed joint sets suggest that the stretching direction during the late stage of exhumation was sub-horizontal and NE-SW trending. The dominant joints observed in seven rivers from the Dalun in the south to the Mugua in the north occur with dm-scale spacing and appear to play a role in the erosional expression of the outcrops regardless of the orientation of the local stream channel. The joint sets are consistently oriented with NW-SE strike and near vertical dip. One notable exception is along the Chingshui river where moderate to steep NE dips are dominant. We observe that mm-scale veins in exposures along three rivers occur with similar orientations, and that locally these veins are cut by a spaced foliation interpreted to be the youngest metamorphic fabric in these rocks (S3). These observations suggest the NE-SW stretching was underway at depths where pressure solution was active. A small population of outcrop-scale faults provides additional constraints on the geometry of stress/strain during brittle deformation. The faults occur along the Dalun, Chingshui and Hongyeh rivers and accommodate both normal and strike-slip motion. Preliminary fault plane solutions suggest that the faults record sub-horizontal NE-SW stretching, similar that indicated by the veins and joints. The stretching direction is approximately normal to the motion of the Philippine Sea plate relative to Eurasia, and if it is characteristic of late stage exhumation, provides an important input to mechanical models of the Taiwan orogeny.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.T31A..06A
- Keywords:
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- 7230 Seismicity and tectonics;
- SEISMOLOGYDE: 8107 Continental neotectonics;
- TECTONOPHYSICSDE: 8175 Tectonics and landscape evolution;
- TECTONOPHYSICSDE: 8177 Tectonics and climatic interactions;
- TECTONOPHYSICS