11-14 Constraining emplacement and eruption timescales of flood basalt lavas using volcanological data

Session: Using Volcanic Deposits to Help Us Understand Volcanic and Magmatic Processes

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Abstract:

Continental flood basalts represent the largest volcanic events in Earth’s history and are directly linked to major climate perturbations and mass extinctions. Because these eruptions lack modern analogues, key parameters, such as eruption and emplacement timescales, volumes of individual flow events, and inter-eruptive time gaps, remain poorly constrained. Additionally, their eruption styles are not well understood. Constraining these factors is essential to evaluate the climatic and geologic impacts of Large Igneous Province emplacement. Lava morphology preserves critical evidence of these parameters: flow geometry varies systematically with eruptive rate, eruption temperature, pre-eruptive topography, and other emplacement conditions. Interactions between lobes - their margins and brittle/ ductile deformation features preserve information on the time gap between the emplacement of lobes. In this study, we analyze the morphology of lavas from the lower stratigraphic formations of the Deccan Traps using field photographs, hand sketches, and LIDAR scans. This multi-mode data collection approach enables us to record detailed information at different scales, allowing for a robust comparison across different locations. We use these morphological observations to reconstruct eruption timescales and estimate the rates of volatile release during emplacement. Morphology also provides a test of whether these flows originated from a single geographic source, as has been proposed in previous work on the Deccan. The examined flow fields consist primarily of small (centimeter- to meter-scale) pāhoehoe lobes displaying variable interactions, from brittle and ductile deformation to glassy margins to complete lobe fusion. These features indicate rapid emplacement with minimal breaks in activity and overall low effusion rates. The data further show that the flow fields were emplaced over extended durations of months to years, comparable to the timescales inferred for the Roza Member of the Columbia River Basalt Group. The limited lobe dimensions make long-distance flow (hundreds of kilometers) improbable, strongly suggesting that these lavas did not erupt from a single centralized source. This multi-modal approach for collecting information on lava morphology provides a useful framework for deriving inferences on the evolution of LIPs.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-8374

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