A westerly wind dominated Puna Plateau during deposition of upper Pleistocene loessic sediments in the subtropical Andes, South America

Abstract

The Tafí del Valle depression (~27° S) in the eastern Andes of Argentina provides a record of late Pleistocene dust deposition in the subtropics of South America. We present large-n U-Pb geochronology data for detrital zircons from upper Pleistocene loess-paleosol deposits. When compared to regional data, the age spectra from the Tafí del Valle samples are most like the southern Puna Plateau, supporting derivation largely from the west and northwest. This runs counter to hypotheses suggesting these loessic sediments were derived from the low elevation plains to the east or extra-Andean Patagonia. Mapping of linear wind erosion features on the Puna Plateau yield a mean orientation of 125.7° (1 s.d. = 12.4°). These new data and existing records are consistent with a westerly-northwesterly dominated (upper- and lower-level) wind system over the southern Puna Plateau (to at least ~27° S) during periods of high dust accumulation in Tafí del Valle.

Loss of loess in the geological record due to poor preservation

“…Furthermore, these topographies affect atmospheric circulation and may cause aridity due to the rain shadow effect thereby further promoting loess genesis. For example, the Andes block westerly moisture resulting in dry, dust‐transporting winds in Argentina (Pullen et al, 2022) and the Tien Shan causes aridity and subsequent loess deposition in western China (Sun, 2002). We thus conclude that the proximity to mountains makes foreland settings more suitable to preserving loess deposits than other basin types.…”

An exploratory study of “large‐n” detrital zircon geochronology of the Book Cliffs, UT via rapid (3 s/analysis) U–Pb dating

“…Second, increased sample size usually bolsters the calculation of MDA with identification of more young grains, although debate persists on which part an age distribution best approximates maximum depositional age and how best to calculate it (Copeland, 2020; Coutts et al., 2019; Dickinson & Gehrels, 2009; Herriott et al., 2019; Johnstone et al., 2019; Vermeesch, 2020). Despite the potential benefits of “large‐ n ” ( n = 300–1000) compared to “low‐ n ” ( n ≈ 100) DZ geochronology, only a few studies have implemented large‐ n techniques for interpretations of sediment provenance (e.g., Bartschi et al., 2018; Pettit et al., 2019; Pullen et al., 2014), although the practice is becoming more common (e.g., Garber et al., 2020; Gardner et al., 2022; Gehrels et al., 2020; Pullen et al., 2022; Rosenblume et al., 2021, 2022). To date, even fewer studies have implemented “very large‐ n ” DZ geochronology ( n > 1000) for applied sedimentology (e.g., Ibañez‐Mejia et al., 2018; Pullen et al., 2014).…”

High‐frequency temporal variability of provenance signal in the submarine fan with the narrow shelf: Insights from sediment delivery and formation of late Triassic Zhuoni fan in the northeastern Paleo‐Tethys Ocean

“…High‐frequency provenance changes could be directly related to discharge, currents, waves and differential settling at a more local scale, contributing to different magnitudes of sediment mixing (Anders, Tyrrell, Chew, Mark, et al., 2022; Anders, Tyrrell, Chew, O'Sullivan, et al., 2022). Previous source‐to‐sink studies have recently concentrated on relatively shorter timescale temporal variations mostly late Cenozoic to Quaternary loess (Pullen et al., 2022; Zhang et al., 2022), fluvial deposits (Clift & Giosan, 2014; Clift & Jonell, 2021; Gutiérrez & Stockli, 2023; Neubeck et al., 2023) and river mouth to deep‐water deposits (Blum et al., 2018; Fildani et al., 2018; Mason et al., 2019; Wang et al., 2023; Zhou et al., 2022), but further understanding of high‐frequency provenance variations in deep‐time depositional records remains relatively poor.…”