Timescales of magma transport in the Columbia River flood basalts, determined by paleomagnetic data

Joseph Biasi,Leif Karlstrom

doi:10.1016/j.epsl.2021.117169

Abstract

Flood basalts represent major events in Earth History, in part because they are linked to large climate perturbations and mass extinctions. However, the durations of individual flood basalt eruptions, which directly impact potential environmental crises, are poorly constrained. Here we use a combination of paleomagnetic data and thermal modeling to create a magnetic geothermometer (MGT) that can constrain the active transport lifetime of magmatic conduits and intrusions. We apply the MGT technique to eight feeder dike segments of the Columbia River basalts (CRB), demonstrating that some dike segments were actively heating host rocks for less than one month, while other segments may have been active for several years. Results suggest that eruption rates, localized spatially along-strike of dike segments, were as high as 1–8 km3day−1. These results help contextualize field evidence for contrasting CRB eruption durations and suggest a pathway for constraining the tempo of global flood basalt magmatism that is beyond the resolution of geochronology.

Highlights

Throughout Earth History, emplacement of flood basalts often coincided with mass extinctions or major climate disturbances (Clapham and Renne, 2019)
Current geochronological techniques can determine the amount of time that has passed between two discrete eruptions if they are not within error of each other (>10 kyr for the Columbia River Basalts or Columbia River basalts (CRB); Kasbohm and Schoene, 2018) but cannot measure
We note that four out of eight dike segments studied here are not found in the extensive Chief Joseph dike swarm maps generated by William H

Summary

Introduction

Throughout Earth History, emplacement of flood basalts often coincided with mass extinctions or major climate disturbances (Clapham and Renne, 2019). Individual flood basalt eruptions can release large amounts of carbon, sulfur, chlorine, fluorine, and mercury directly into the atmosphere (Thordarson and Self, 1996). If these volatiles are released over thousands of years, their effects may be significantly muted through biogeochemical sequestration. If most of these volatiles are released in shortduration high-intensity pulses, they can have a major impact on the climate (Schmidt et al, 2016). Uncertainty in individual eruption durations is a major barrier to understanding these events. Paleoclimate proxies in the sedimentary record commonly preserve the climatic or biological impact of these eruptions Paleoclimate proxies in the sedimentary record commonly preserve the climatic or biological impact of these eruptions (e.g. Fendley et al, 2019), not the eruptions themselves, and sedimentation rates are too slow to capture such events in detail

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