P–PINI: A cosmogenic nuclide burial dating method for landscapes undergoing non-steady erosion

• Published in: Quaternary Geochronology
• Main Authors: Nørgaard, Jesper, Jansen, John D., Neuhuber, Stephanie, Ruszkiczay-Rüdiger, Zsófia, Knudsen, Mads Faurschou
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2023
• Subjects: Burial dating; Cosmogenic nuclides; Erosion; Inverse Monte Carlo modelling; Sediments; alaska range; glaciers; Alaska
• Online Access: https://pure.au.dk/portal/da/publications/ppini-a-cosmogenic-nuclide-burial-dating-method-for-landscapes-undergoing-nonsteady-erosion(e0aff802-1145-4cfc-9814-bece73e1aaea).html; https://doi.org/10.1016/j.quageo.2022.101420

Existing methods of cosmogenic nuclide burial dating perform well provided that sediment sources undergo steady rates of erosion and the samples experience continuous exposure to cosmic rays. These premises exert important limitations on the applicability of the methods. And yet, high mountain sediment sources are rife with transient processes, such as non-steady erosion by glacial quarrying and/or landsliding, or temporary cosmic-ray shielding beneath glaciers and/or sediment. As well as breaching the premises of existing burial dating methods, such processes yield samples with low nuclide abundances and variable 26 Al/ 10 Be ratios that may foil both isochron and simple burial-age solutions. P–PINI (Particle-Pathway Inversion of Nuclide Inventories) is a new dating tool designed for dating the burial of sediments sourced from landscapes characterized by abrupt, non-steady erosion, discontinuous exposure, and catchments with elevation-dependent 26 Al/ 10 Be production ratios. P–PINI merges a Monte Carlo simulator with established cosmogenic nuclide production equations to simulate millions of samples ( 10 Be– 26 Al inventories). The simulated samples are compared statistically with 10 Be– 26 Al measured in field samples to define the most probable burial age. Here, we target three published 10 Be– 26 Al datasets to demonstrate the versatility of the P–PINI model for dating fluvial and glacial sediments. (1) The first case serves as a robust validation of P–PINI. For the Pulu fluvial gravels (China), we obtain a burial age of 1.27 ± 0.10 Ma (1σ), which accords with the isochron burial age and two independent chronometers reported in Zhao et al. (2016) Quaternary Geochronology 34, 75–80. The second and third cases, however, reveal marked divergence between P–PINI and isochron-derived ages. (2) For the fluvial Nenana Gravel (USA), we obtain a minimum-limiting burial age of 4.5 ± 0.7 Ma (1σ), which is compatible with unroofing of the Alaska Range starting ∼ 6 Ma, while calling into question the Early Pleistocene ...