Gauri Dole

Slabby pahoehoe from the western Deccan Volcanic Province: evidence for incipient pahoehoe–aa transitions

Abstract The pahoehoe–aa transition for a flow exposed near Bodshil village from the western part of the Deccan Volcanic Province (DVP) is reported for the first time. The ∼1-km-long Bodshil flow issued as a small sheet from a pre-existing lobe. Near the source, the crust is characterised by numerous squeeze-ups. A number of gaping fractures, parallel to sub-parallel to the flow direction, are exposed on the surface in the medial portion of the flow. About 800 m away, the flow completely transforms to slabby pahoehoe. The terminal portion of the flow is characterised by concentrations of slabs, blocks and lava balls. The size and concentrations of the slabs and lava balls appear to increase along the length of the flow. Petrographic studies reveal a dominant hypohyaline texture. The flow core is coarse and is characterised by plagioclase set in a glassy matrix. The presence of clinopyroxene in addition to plagioclase and glass distinguishes the crust and interslab crust from the core. On the basis of mineralogy, a temperature range of 1146±15°C to 1169±15°C is inferred for the Bodshil flow. Increased vesicle deformation across the transition is discernible and an average D -value of

A brief comparison of lava flows from the Deccan Volcanic Province and the Columbia-Oregon Plateau Flood Basalts: Implications for models of flood basalt emplacement

The nature and style of emplacement of Continental Flood Basalt (CFB) lava flows has been a matter of great interest as well as considerable controversy in the recent past. However, even a cursory review of published literature reveals that the Columbia River Basalt Group (CRBG) and Hawaiian volcanoes provide most of the data relevant to this topic. It is interesting to note, however, that the CRBG lava flows and their palaeotopographic control is atypical of other CFB provinces in the world. In this paper, we first present a short overview of important studies pertaining to the emplacement of flood basalt flows. We then briefly review the morphology of lava flows from the Deccan Volcanic Province (DVP) and the Columbia-Oregon Plateau flood basalts. The review underscores the existence of significant variations in lava flow morphology between different provinces, and even within the same province. It is quite likely that there were more than one way of emplacing the voluminous and extensive CFB lava flows. We argue that the establishment of general models of emplacement must be based on a comprehensive documentation of lava flow morphology from all CFB provinces.

Possible lava tube system in a hummocky lava flow at Daund, western Deccan Volcanic Province, India

A hummocky flow characterised by the presence of toes, lobes, tumuli and possible lava tube system is exposed near Daund, western Deccan Volcanic Province, India. The lava tube system is exposed as several exhumed outcrops and is composed of complex branching and discontinuous segments. The roof of the lava tube has collapsed but original lava tube walls and fragments of the tube roof are seen at numerous places along the tube. At some places the tube walls exhibit a single layer of lava lining, whereas, at other places it shows an additional layer characterised by smooth surface and polygonal cracks. The presence of a branching and meandering lava tube system in the Daund flow, which represents the terminal parts of Thakurwadi Formation, shows that the hummocky flow developed at a low local volumetric flow rate. This tube system developed in the thinner parts of the flow sequence; and tumuli developed in areas where the tube clogged temporarily in the sluggish flow.

Deccan Plateau uplift: insights from parts of Western Uplands, Maharashtra, India

Abstract The western edge of the Deccan Plateau (=Western Uplands) has been depicted in its evolutionary models to be a contiguous crustal block exposing structurally undisturbed subhorizontal stacks of Deccan Trap basalts. The geomorphological and morphometric characteristics of this terrain, Quaternary fluvial sediments capping the Deccan Traps in some river basins, compounded with deformation features in the basalts, and in the overlying sediments, are compiled here. They demonstrate that the Western Upland region of the Deccan Plateau may be constituted of no less than three blocks with differential Quaternary uplift histories, rather than the entire region experiencing a unified uplift.

Triggering of the largest Deccan eruptions by the Chicxulub impact: Comment

The environmental crisis responsible for the terminal Cretaceous extinctions has been linked with either episodes of Deccan volcanism or the Chicxulub impact (see Bhandari et al., 1996; Keller et al., 2009; Schulte et al., 2010; Schoene et al., 2015). Richards et al. (2015) proposed a connection between the two events and suggested that there was a change in the Deccan magmatic system as a result of the impact that occurred on the other side of Earth (more than 13,000 km away). They suggested that the seismic waves resulting from the Chicxulub impact could have affected the magmatic system responsible for Deccan volcanism.

Faulting in Deccan Traps in the vicinity of Koyna-Warna Seismic Zone

Studies of sustained activity in the Koyna — Warna Seismic Zone have yielded several models of faults in the basement of the Deccan Traps inferred from geophysical and seismic signatures. There is however, a dearth of unambiguous surface manifestations of such faults, apart from the surface ruptures from the epicentral zone of the December, 1967 earthquake. We report for the first time, an exposed NW-SE trending reverse fault in the Deccan Trap basalts from this region.