Geology, petrochemistry, and genesis of the bimodal lavas of Osham Hill, Saurashtra, northwestern Deccan Traps

Sheth, Hetu; Choudhary, Amol; Cucciniello, Ciro; Bhattacharyya, S.; Laishram, Ramesh; Gurav, Trupti

doi:10.1016/j.jseaes.2011.09.008

Cited by 40 publications

(19 citation statements)

References 62 publications

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“…3. (a-h 2004; Maithani et al, 1996;Sheth et al, 2011a), as well as rhyolites in the Mumbai, Rajpipla, and Pavagadh areas (Fig. 1a) (Lightfoot et al, 1987;Mahoney et al, 1985;Sheth and Melluso, 2008).…”

Section: The Chogat-chamardi Complex: Field Geology and Samplesmentioning

confidence: 91%

The Chogat-Chamardi subvolcanic complex, Saurashtra, northwestern Deccan Traps: Geology, petrochemistry, and petrogenetic evolution

Sheth

Choudhary

Bhattacharyya

et al. 2011

Journal of Asian Earth Sciences

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Section: The Chogat-chamardi Complex: Field Geology and Samplesmentioning

confidence: 91%

The Chogat-Chamardi subvolcanic complex, Saurashtra, northwestern Deccan Traps: Geology, petrochemistry, and petrogenetic evolution

Sheth

Choudhary

Bhattacharyya

et al. 2011

Journal of Asian Earth Sciences

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“…The Osham pitchstones also contain perlitic cracks which we ascribe to secondary hydration (e.g., Ross and Smith 1955). Additional photomicrographs and field and geochemical data on the Osham Hill lava sequence can be found in Sheth et al (2011b). The Kagvadar spherulites also display a distinct radial structure in thin section (Fig.…”

Section: Petrographymentioning

confidence: 93%

“…1) in western Saurashtra, northwest of Mount Girnar, shows a flow sequence of rhyolite, pitchstone, and basaltic andesite (Sheth et al 2011b). The summit rhyolite flow is very fine-grained and contains patches of devitrified glass besides quartz and alkali feldspars.…”

Section: Field Geology Of the Deccan Spherulites And Thundereggsmentioning

confidence: 98%

“…Subvolcanic intrusions of trachyte outcrop along the Mumbai coast, only a few kilometers west of this pitchstone (Lightfoot et al 1987;Zellmer et al 2011). On the other hand, the Osham Hill pitchstones are lavas (Sheth et al 2011b). The Deccan pitchstones are good analogs of the subvolcanic pitchstone intrusions (dikes and cone sheets), as well as pitchstone lavas, mapped in the Scottish Hebrides, a part of the Palaeogene North Atlantic igneous province (Tyrrell 1926;Drysdale 1979;Hatch et al 1983;Emeleus and Bell 2001).…”

Section: Emplacement Environment and Stylementioning

confidence: 99%

“…CB01 Chatterjee and Bhattacharji(2001),L87 Lightfoot et al (1987),M85 Mahoney et al. (1985),SM08 Sheth and Melluso (2008), S11aSheth et al (2011a), S11bSheth et al (2011b),M96 Maithani et al (1996), andM95 Melluso et al (1995). Boundary lines between the subalkalic and alkalic fields proposed byMacdonald and Katsura (1964, short heavy line) andIrvine and Baragar (1971, curved dashed line) are also shown…”

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confidence: 99%

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Spherulites and thundereggs from pitchstones of the Deccan Traps: geology, petrochemistry, and emplacement environments

et al. 2011

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Spherulites and thundereggs are rounded, typically spherical, polycrystalline objects found in glassy silicic rocks. Spherulites are dominantly made up of radiating microscopic fibers of alkali feldspar and a silica mineral (commonly quartz). They form due to heterogeneous nucleation in highly supercooled rhyolitic melts or by devitrification of glass. Associated features are lithophysae ("stone bubbles"), which have an exterior (sometimes concentric shells) of fine quartz and feldspar, and internal cavities left by escaping gas; when filled by secondary silica, these are termed thundereggs. Here, we describe four distinct occurrences of spherulites and thundereggs, in pitchstones (mostly rhyolitic, some trachytic) of the Deccan Traps, India. The thundereggs at one locality were previously misidentified as rhyolitic lava bombs and products of pyroclastic extrusive activity. We have characterized the thundereggs petrographically and geochemically and have determined low contents of magmatic water (0.21-0.38 wt.%) in them using Fourier transform infrared spectroscopy. We consider that the spherulite-bearing outcrops at one of the localities are of lava flows, but the other three represent subvolcanic intrusions. Based on the structural disposition of the Deccan sheet intrusions studied here and considerations of regional geology, we suggest that they are cone sheets emplaced from a plutonic center now submerged beneath the Arabian Sea.

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Hydroclimate variability during the last two millennia from the mudflats of Diu Island, Western India

et al. 2021

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The climate variability over western India has been significantly influenced by the perturbations in the Indian summer monsoon (ISM) and thus, provides a crucial platform to investigate the paleomonsoon variations, weathering intensity, and sediment source. The mudflats of southern Saurashtra, western India are deprived of perennial rivers, but the region receives terrestrial contribution exclusively due to activation of seasonal rivers during the monsoon. In the present study, an attempt has been made to investigate the paleomonsoon and palaeoweathering using various geochemical proxies (detrital, productivity, redox, and weathering) on the mudflat sediment core of southern Saurashtra, western Gujarat. The core is chronologically constrained by 14 C, 210 Pb, and 137 Cs dating techniques. The study suggests ISM strengthening during 2000-1800 cal yr BP with intermittent marginal ISM weakening during 1950-1970 cal yr BP and 1930-1890 cal yr BP associated with the reduced solar irradiance. Further, ISM weakening has been invoked during Dark Age Cold period (1800-1300 cal yr BP) and Little Ice Age (800-200 cal yr BP) interrupted by a marginal ISM strengthening during Medieval Warm period and the last two centuries witness climate warming. Based on historical rainfall data and Al 2 O 3, an intermittent strengthening of ISM during 90-30 cal yr BP has been suggested while a gradual increase in the weathering intensity synchronous to the rise in sea surface temperature (SST) during the last 200 cal yr BP revealed the role of temperature on the intensity of chemical weathering in the study area. In spite of changes in the geochemical proxies as a function of ISM fluctuations, the palaeoweathering intensities has remained nearly consistent wherein the chemical weathering was less operative and accompanied by the deposition of texturally immature sediments. The sediments of Diu mudflat indicate mafic signatures thereby underscoring a major contribution of the Deccan basalts along with other variable sources.

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Geology, petrochemistry, and genesis of the bimodal lavas of Osham Hill, Saurashtra, northwestern Deccan Traps

Cited by 40 publications

References 62 publications

The Chogat-Chamardi subvolcanic complex, Saurashtra, northwestern Deccan Traps: Geology, petrochemistry, and petrogenetic evolution

The Chogat-Chamardi subvolcanic complex, Saurashtra, northwestern Deccan Traps: Geology, petrochemistry, and petrogenetic evolution

Spherulites and thundereggs from pitchstones of the Deccan Traps: geology, petrochemistry, and emplacement environments

Hydroclimate variability during the last two millennia from the mudflats of Diu Island, Western India

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