Wildfires and Monsoons: Cryptic Drivers for Highly Variable Provenance Signals within a Carboniferous Fluvial System

Abstract

Sediment delivery and supply are explicitly controlled by variations in broad-scale processes such as climate, tectonics and eustasy. These in turn influence fluvial processes and hinterland evolution. A bespoke multi-proxy approach (integrating apatite and zircon U-Pb geochronology, trace elements in apatite, and Pb-in-K-feldspar provenance tools) coupled with outcrop investigation is used to constrain the temporal trends in sediment delivery to channel sandstones of the fluvio-estuarine mid-Viséan Mullaghmore Sandstone Formation, Ireland. Provenance data indicate unique detrital signatures for all sampled horizons, indicating the fluctuating nature of sediment supply to this medium-sized basin. Tectonism and/or abrupt relative sea-level fall likely caused fluvial rejuvenation, resulting in local basement sourcing of the initial fill. Older and more distal sources, such as the Nagssugtoqidian Belt of East Greenland, become more prominent in stratigraphically younger channel sandstones suggesting catchment expansion. Paleoproterozoic to Mesoproterozoic sources are most dominant, yet the detrital grain cargo varies in each channel sandstone. Proximal sources such as the Donegal Batholith and Dalradian Supergroup are variable and appear to switch on and off. These signal shifts are likely the result of channel migration and paleoclimatic fluctuation. A monsoonal climate and large-scale wildfire events (evidenced by fusain) likely contributed to modify plant cover, intensify erosion, and increase run-off and sediment delivery rates from specific areas of the hinterland.

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

“…The relatively higher contribution of the adjacent Permian covers indicated the enhanced erosion of the downstream sector of the onshore catchment (Figure 16b). The increased sediment supply could be linked with high precipitation and seasonal floods due to the spatial climate variability of the entire drainage system, while fluvial rejuvenation could also intensify the denudation of the downstream sector during the lowstand period (Anders, Tyrrell, Chew, Mark, et al., 2022; Anders, Tyrrell, Chew, O'Sullivan, et al., 2022). In addition, it could be alternatively attributed to partial sediment buffering in the downstream sector of the onshore catchment, which may have strongly shredded the upstream provenance signals (Figure 16b).…”

“…Alternatively, the provenance signal could be significantly perturbated by high‐frequency climate change (Caracciolo, 2020, 2021; Clift & Jonell, 2021). 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.…”