Morphological types in the Deccan Volcanic Province, India: implications for emplacement dynamics of continental flood basalts

Abstract

We review and compare morphologies from continental basaltic lavas, using examples from the Deccan Volcanic Province to compile their internal configurations, mutual associations and compare them. The mechanism of endogenous transfer of lava within an insulating (rapidly developed) crust provides an efficient mode of dispersal of the molten lava in flood basalts. The growth of the lava flow can be achieved by a single extrusion or by multiple pulses of endogenous emplacement that enable the lava to efficiently spread over large areas and thicken.We show that the morphology of a lobe manifests the response of the molten lava to several parameters (including volumetric rate of emplacement, substrate topography, viscosity, vapour loss, etc) that govern the dynamics and cooling history of basaltic lava after it starts to spread on the surface. The lateral transition from one morphology to another within lobes of a lava flow is a testimony to the interactive response of the lava dynamics and rheology to variation in the local systems in which they were emplaced. The morphologies do not evolve as rigid partitioned categories from ‘áā and pāhoehoe lava types’ but as parametric progression of interactive variations in the spreading and cooling lava.A hierarchical recognition of lobes, flows and flow fields and mapping of the morphology (and their lateral transition or continuity) combined with the stacking patterns provides the volcanological framework for a sound stratigraphic mapping of flood basalts. Such an architectural documentation of flood basalt provinces will lead to robust models of their eruptive histories.

Syn‐rift volcanism in the Barmer Basin: An intra‐basin extrusive complex at the northern limit of the Deccan volcanic province in India

“…Highly rubbly bases and tops are interpreted to be indicative of a'a‐type flows, whilst stacked vesicular, rubble‐poor flows are interpreted to be indicative of pahoehoe‐type flows. These contrasts in textures are used to estimate individual flow thickness vary between around to 5–10 m, consistent with Misra (2006) Duraiswami et al (2014) and Kale et al, 2022. Most of the flows are of pahoehoe type with a subordinate component of a'a flows.…”

Flood basalt structures and textures as guides to cooling histories and palaeoclimates: the Deccan Traps of Saurashtra, western India

“…Columnar-jointed sheet lobes of tabular geometry are common in various CFB provinces, including the Deccan Traps (e.g. Long & Wood, 1986;Puffer & Student, 1992;Williamson & Bell, 1994;Lyle, 2000;Jerram, 2002;Sengupta & Ray, 2006;Passey & Bell, 2007;Duraiswami et al 2008;Reidel et al 2013;Schöbel et al 2014;Sheth, 2018;Kale et al 2022). The sheet lobes studied here, besides showing several morphotypes, also show varied jointing patterns which provide clues to their cooling and solidification histories under particular palaeoclimatic conditions.…”

“…Bondre et al 2004;Jay et al 2009), though in Saurashtra and Kachchh in the northwest, maximum preserved thicknesses are a few hundred metres (Sheth et al 2013). Both compound and simple flows are found in abundance (Walker, 1971;Deshmukh, 1988;Bondre et al 2004;Sheth, 2018;Kale et al 2022). The small-scale compound pāhoehoe flows are usually pervasively altered, contain basal pipe vesicles and are frequently hummocky, i.e.…”