Highlights—Asymmetric Orogenic Sands

Although critical wedge theory predicts asymmetrical exhumation, peak metamorphism and erosion of the pro- and retro- sides of an orogen, the implications for sandstone attributes are not well understood. Here, Nagel et al. use sandstone petrography, clay mineralogy, and heavy-mineral assemblages in Plio-Pleistocene sandstone from the Western Foothills of Taiwan to unravel the record of a rapidly subsiding foreland basin that records the collision between a volcanic arc and the Asian passive margin. Comparison of the provenance record from the western and eastern basins illustrates the opposing signature of unroofing and recycling, variability interpreted to be characteristic of an asymmetric orogenic wedge. The results illustrate how sandstone petrography could be used in ancient sedimentary basins to complement other indications of the polarity of subduction.

Provenance evolution duringarc–continent collision: sedimentary petrography of Miocene to Pleistocenesediments in the western foreland basin of Taiwan by Stefan Nagel, Sébastien Castelltort, Eduardo Garzanti, Andrew T. Lin, Sean D. Willett, Frédéric Mouthereau, Mara Limonta, and Thierry Adatte