Petrography, geomagnetism, and rare-earth element abundances of the Rajahmundry lavas, eastern India

Banerjee, P. K.; Ghose, Naresh Chandra; Ravikumar, V.; Chacko, Soman

doi:10.1016/0743-9547(96)00015-3

Cited by 6 publications

(8 citation statements)

References 13 publications

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“…This has been confi rmed by magnetostratigraphy and geochemical similarities with the main Deccan volcanic province to the west (Lightfoot et al 1990;Subbarao and Pathak 1993;Banerjee et al 1996;Baksi 2001;Jay and Widdowson 2008;Jay et al 2009). The Rajahmundry traps, which reach 1000 km across India, are thus the longest lava fl ows known in Earth history (Self et al 2008a) and may represent the volcanic acme of phase 2 ending at or near the KT mass extinction (Keller et al 2008a).…”

Section: Palaeomagnetic and Radiometric Agesmentioning

confidence: 85%

Deccan volcanism, the KT mass extinction and dinosaurs

2009

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Recent advances in Deccan volcanic studies indicate three volcanic phases with the phase-1 at 67.5 Ma followed by a 2 m.y. period of quiescence. Phase-2 marks the main Deccan volcanic eruptions in Chron 29r near the end of the Maastrichtian and accounts for approximately 80% of the entire 3500 m thick Deccan lava pile. At least four of the world's longest lava flows spanning 1000 km across India and out into the Gulf of Bengal mark phase-2. The final phase-3 was smaller, coincided with the early Danian Chron 29n and also witnessed several of the longest lava flows. The KT boundary and mass extinction was first discovered based on planktic foraminifera from shallow marine intertrappean sediments exposed in Rajahmundry quarries between the longest lava flows of the main volcanic phase-2 and smaller phase-3. At this locality early Danian (zone P1a) planktic foraminiferal assemblages directly overlie the top of phase-2 eruptions and indicate that the masse extinction coincided with the end of this volcanic phase. Planktic foraminiferal assemblages also mark the KT boundary in intertrappean sediments at Jhilmili, Chhindwara, where freshwater to estuarine conditions prevailed during the early Danian and indicate the presence of a marine seaway across India at KT time. Dinosaur bones, nesting sites with complete eggs and abundant eggshells are known from central India surrounding the hypothesized seaway through the Narmada-Tapti rift zone. A Maastrichtian age is generally assigned to these dinosaur remains. Age control may now be improved based on marine microfossils from sequences deposited in the seaway and correlating these strata to nearby terrestrial sequences with dinosaur remains.

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Section: Palaeomagnetic and Radiometric Agesmentioning

confidence: 85%

Deccan volcanism, the KT mass extinction and dinosaurs

2009

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“…Quartzose sedimentary rocks and sediments show REE patterns similar to G3 (figure 8, inset). Banerjee et al's (1996) type 2 rocks (G1, 2, 4 -6), show REE patterns more normal for basalts. Individual patterns intersect ( figure 9), suggesting the rocks may not CaO 9.9 10.0 10.0 10.0 9.9 9.8 9.9 9.9 10.2 10.3 11.5 13.3…”

Section: Lava(s) On the Western Bank Below The Intertrappean Layermentioning

confidence: 99%

“…be genetically related. The RT rocks display no Eu anomaly, whereas three samples from Banerjee et al (1996) show a negative Eu anomaly and one (G4) a slight positive anomaly (figure 9). Assuming ±10% error in determination of REE, ∼ 60% fractionation of plagioclase from a basaltic liquid yields a discernible Eu anomaly (cf.…”

Section: Lava(s) On the Western Bank Below The Intertrappean Layermentioning

confidence: 99%

“…Samples 2/2A, thought to belong to the flow below the intertrappean layer on the west bank, show normal magnetic polarity; clearly they belong to the flow above the intertrappean layer. Banerjee et al (1996) reported normal magnetic polarity for rocks on the east bank and mixed polarities for rocks from the base of the lavas on the west bank. The normal polarity reported for the latter are spurious, and resulted from analysis of rocks without magnetic cleaning.…”

Section: Introductionmentioning

confidence: 99%

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The Rajahmundry Traps, Andhra Pradesh: Evaluation of their petrogenesis relative to the Deccan Traps

Baksi

2001

J Earth Syst Sci

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Geochemical and geochronological data for rocks from the Rajahmundry Traps, are evaluated for possible correlation with the main Deccan province. Lava flows are found on both banks of the Godavari River and contain an intertrappean sedimentary layer. Based on 40 Ar/ 39 Ar age data, rocks on the east bank are post K-T boundary, show normal magnetic polarity, and belong to chron 29N. Their chemistry is identical to lavas in the Mahabaleshwar Formation in the Western Ghats, ∼1000 km away. It was suggested earlier that the genetic link between these geographically widely separated rocks resulted from lava flowing down freshly incised river canyons at ∼64 Ma. For the west bank rocks, recent paleomagnetic work indicates lava flows below and above the intertrappean (sedimentary) layer show reversed and normal magnetic polarity, respectively. The chemical composition of the west bank flow above the intertrappean layer is identical to rocks on the east bank. The west bank lava lying below the sedimentary layer, shows chemistry similar to Ambenali Formation lava flows in the western Deccan. 40 Ar/ 39 Ar dating and complete chemical characterization of this flow is required to elucidate its petrogenesis with respect to the main Deccan Province.

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“…The modal abundance of clinopyroxene is about 20%. Many clinopyroxene crystals are altered along their margins to a dark brown mineral, possibly nantronite (see also Banerjee et al, 1996). Opaque minerals with a dendritic subhedral habit constitute about 7% modally.…”

Section: Petrography and Mineralogymentioning

confidence: 98%

Petrology and geochemistry of the Salma dike, Raniganj coalfield (Lower Gondwana), eastern India: linkage with Rajmahal or Deccan volcanic activity?

Paul

2005

Journal of Asian Earth Sciences

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Petrography, geomagnetism, and rare-earth element abundances of the Rajahmundry lavas, eastern India

Cited by 6 publications

References 13 publications

Deccan volcanism, the KT mass extinction and dinosaurs

Deccan volcanism, the KT mass extinction and dinosaurs

The Rajahmundry Traps, Andhra Pradesh: Evaluation of their petrogenesis relative to the Deccan Traps

Petrology and geochemistry of the Salma dike, Raniganj coalfield (Lower Gondwana), eastern India: linkage with Rajmahal or Deccan volcanic activity?

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