Extremely rapid up-and-down motions of island arc crust during arc-continent collision

Abstract

Mountain building and the rock cycle often involve large vertical crustal motions, but their rates and timescales in unmetamorphosed rocks remain poorly understood. We utilize high-resolution magneto-biostratigraphy and backstripping analysis of marine deposits in an active arc-continent suture zone of eastern Taiwan to document short cycles of vertical crustal oscillations. A basal unconformity formed on Miocene volcanic arc crust in an uplifting forebulge starting ~6 Ma, followed by rapid foredeep subsidence at 2.3–3.2 mm yr−1 (~3.4–0.5 Ma) in response to oceanward-migrating flexural wave. Since ~0.8–0.5 Ma, arc crust has undergone extremely rapid (~9.0–14.4 mm yr−1) uplift to form the modern Coastal Range during transpressional strain. The northern sector may have recently entered another phase of subsidence related to a subduction polarity reversal. These transient vertical crustal motions are under-detected by thermochronologic methods, but are likely characteristic of continental growth by arc accretion over geologic timescales.

Foraminifera as a tool for the reconstruction of paleobathymetry and geohazard: A case study from Taiwan

“…The application of this modern analog-based calibration might help to generate at least semiquantitative bathymetry estimates, which can be used to reveal the depositional setting of the many outcrops in Taiwan and to shed more light on processes such as the rapid uplift of the central range of Taiwan since the Plio-Pleistocene (i.e., Lai et al, 2022). Further effort should be directed to refine the calibration model by increasing the sample size, including diversity indices and stressor species of benthic foraminifera in the %P calculation, and/or including the census counts of smaller size fractions (i.e., 63-125 µm).…”

Retro‐Foredeep Basin Evolution in Taiwan: Zircon U‐Pb and Hf Isotope Constraints From the Coastal Range

“…Lai et al. (2022) also used updated magneto‐biostratigraphic data to estimate the sediment accumulation rate, which also suggested an accelerated accumulation rate at ∼2 Ma in the southern Coastal Range. Their estimated rate in the first stage is higher than the result in this study.…”

“…The rates of both stages are considerably higher than the accumulation rates of the pro-foreland basin on the passive margin, that is, the Tsaohu River and Tsengwen River sections, which are 0.35-0.39 and 1.80-2.15 km/myr in the early and late stages, respectively (Figure 9). Recently, L. S.-H. Lai et al (2022) also used updated magneto-biostratigraphic data to estimate the sediment accumulation rate, which also suggested an accelerated accumulation rate at ∼2 Ma in the southern Coastal Range. Their estimated rate in the first stage is higher than the result in this study.…”

Extensional mountain building along convergent plate boundary: Insights from the active Taiwan mountain belt

“…Recent acceleration of the subsequent development of the orogenic edifice starting at ca. 2-3 Ma, including surface uplift and exhumation, has been speculated (e.g., Hsu et al, 2016;Chen et al, 2018a;Lai et al, 2022). The entire range is dominated by reverse shearing structures, which were overprinted by extensional (mostly) brittle structures in the ridge and eastern side (Crespi et al, 1996); current deformation is similarly characterized by range-front shortening (including the 1999 CE Chi-Chi earthquake) as well as contractional…”

“…Such a deformation pattern reflects strain partitioning with substantial tectonic underplating at the wedge base, which sustains wedge growth and surface uplift (Beyssac et al, 2007;Malavieille et al, 2021). Unroofing from the surface of the growing wedge has only been recorded well behind the foreland flexure (6.5 Ma; Lin et al, 2003) at <3 Ma both in the foreland basin (Teng, 1990) and in the retrowedge forearc basin (Teng, 1987;Dorsey, 1988;Lai et al, 2022).…”