ABSTRACT

Volcanism in large igneous provinces (LIPs) is understood to have had the potential to affect global environments and ecosystems, triggering mass extinctions, climate change, and ocean acidification. However, basin-scale studies sediment distribution and sedimentary-system development in LIP lava fields are sparse and often limited to localized exposure. To gain a better understanding of the controls on inter-lava sedimentology across a continental LIP, a new sedimentological data set is presented from the Miocene Columbia River Flood Basalt Province (CRBP), situated in the Columbia Basin in south-central Washington State, northeast Oregon and eastern Idaho. Based on the qualification and quantification of sedimentary facies, petrography, paleoflow, channel dimensions, and catchment size from 96 sites across the Columbia Basin, a refined model of regional and local environmental change, integrating local volcanic and tectonic evolution, is presented. Here, CRBP stratigraphy is divided into six distinctive sedimentation intervals, which allows correlation of sedimentary interbeds formed in the western part and in the eastern part of the basin. The model describes and reviews drainage-system development and discusses the control of volcanic and tectonic activity on sediment distribution in the CRBP lava field at local to basin scale. The data presented here largely support findings of previous works suggesting a highly complex interplay between sedimentary, volcanic, and tectonic evolution of the area. In addition, it elaborates on the aspects of sediment–lava interaction and indicates that individual sub-basins in the CRBP formed separated depositional settings, emphasizing the lateral complexity of inter-lava sedimentation. Importantly, this work improves our understanding of sediment–lava relationships in continental LIPs and helps in building more generic models for sediment distribution in volcanic terranes where exposure is limited or absent.

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