1 New advances in geological and geophysical research on the Appalachian orogen.

We invite contributions that discuss new research on the Appalachian orogen. Submissions should include, but are not limited to, geological or geophysical studies or works comprising a combination of both methods.

Sunday, 22 March 2026
8:00 AM - 12:00 PM
CCC, Room 22/23

Detrital Organic Stable Isotope and Molecular Paleohypsometry of the Taiwan Central Range: Implications for Paleotopographic Development

Paper number: 1-3
Program: Technical Sessions
Time: 8:45 AM – 9:05 AM

Authors

Abstract

The oblique arc-continent collision in Taiwan is characterized by rapid rock exhumation, surface uplift, and erosion. This active orogenic process, together with the region’s warm, wet tropical climate, makes Taiwan an ideal natural laboratory to explore feedbacks among tectonics, erosion, and climate. However, the absence of direct and quantitative constraints on paleotopographic evolution poses challenges in evaluating and improving available tectonic models of Taiwan orogeny. Hydrogen isotopic compositions (δ2H) of terrestrial leaf-wax n-alkanes record the isotopic signature of ambient water, providing a molecular archive of past hydrological changes associated with evolving topography. Here, we analyze δ2H of detrital leaf-wax n-alkanes (i.e., δ2Hn-C29) derived from river catchments of the ancient orogenic belt and preserved in the organic-rich mudstones of the Paliwan Formation in the Plio-Pleistocene retro-foredeep basin of the northern Coastal Range in eastern Taiwan. Between ~3.2 and 1.7 Ma, detrital leaf-wax δ2Hn-C29 values were relatively high, consistent with organic matter exported from predominantly low-elevation sources (mean source elevation of ~0.32 km). Thereafter, δ2Hn-C29 gradually decreased from 1.7 Ma to recent, with the largest negative shift occurring after ~0.8 Ma. This isotopic shift is best explained by a progressive increase in the mean source elevation. We estimate a continuous increase in mean source elevation from ~0.32 km before 1.7 Ma, to ~0.7 km between 1.7 and ~1.0 Ma, reaching ~1 km between 1.0 and 0.78 Ma. Between 0.78 and ~0.3 Ma, leaf-wax δ2Hn-C29 further decreased, indicating an increase in mean source elevation to nearly 1.7 km, notably coinciding with the onset of conglomerate deposition in the Coastal Range during the late Pleistocene. By applying relationships between catchment mean and maximum elevation in modern settings, our mean source elevation records imply that maximum catchment elevation in eastern Taiwan was ~1.6 km before 1.7 Ma, growing to ~2.2 km at ~1.0 Ma, quickly rising to ~2.6 km at ~0.78 Ma, and then exceeding ~3.5 km in the last ~0.3 Ma. These observations demonstrate that the northern Central Range began its major topographic growth phase since ~1.7 Ma, and accelerated the rise after ~0.78 Ma until reaching modern elevations.

Geological Society of America Abstracts with Programs. Vol. 58, No. 2

doi: 10.1130/abs/2026NE-411153

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