Pre- and post-erosional estimates of Deccan lava volumes

Loyc Vanderkluysen; Nicholas Barber; Anne E. Jay; Emily Carey; Anonymous

The Deccan Traps are a continental flood basalt province that covers large swaths of the Indian Peninsula. Composed of hundreds of individual lava flows and flow fields, the province was largely emplaced over the course of <1 Myr just before and after the approximately 66 Ma Cretaceous-Paleogene boundary (KPB). This temporal coincidence has long raised the possibility of a causal link between the Deccan event and the KPB mass extinction. However, an in-depth assessment of volcanic-induced environmental impacts requires an understanding of the magma volumes involved, of the concentration of dissolved volatile species, and of the eruptive timing and tempo; up until the last few years, none of these factors were adequately constrained. The aim of this project was to compile and digitize existing geographic data on the thickness and extent of the Deccan Traps and its constitutive units, and use a geographic information systems (GIS) and geostatistical tools to determine the pre- and post-erosional areas and volumes of lava packages. Modern-day, post-erosional lava volumes are straightforward to measure in GIS by integrating the volume sandwiched between a unit's lower and upper raster boundaries in a Digital Elevation Model (DEM) of the province. In these estimates, root mean square volume errors (<1%) largely stem from the kriging method used to interpolate the unit contact surfaces from mapped boundaries. In our case, we achieved the best results by Empirical Bayesian Kriging. By contrast, original pre-erosional volumes are highly dependent on assumptions of original lava extent, aspect ratio of lava flow packages, depth of basement contact where it is not observed, and potential post-emplacement uplift or other forms of crustal deformation. Here, we present upper- and lower-bound estimates of erupted lava volumes as well as volumes of individual Deccan formations, and implications for the emplacement and environmental impact of this large igneous province.