Matsuhisa, Y. Bhattacharya, K. Gopalan, J. Mahoney and J. Macdougall Oxygen isotope evidence for crustal contamination in Deccan basalts. McDougall, I. McElhinny McLean, D. Mantle degassing induced dead ocean in the Cretaceous-Tertiary transition.
AGU Geophys. Monograph 32, — Mishra, D. Mishra, K. Petrology of the picrite-basalt flows in the Igatpuri area, Nasik district, Maharashtra.
Misra, K. The tectonic setting of Deccan volcanics in southern Saurashtra and northern Gujarat. Morgan, W. Hotspot tracks and the opening of the Atlantic and Indian oceans. In: The Sea 7, — Emiliani, C. Wiley, New York. Muir, I. Scoon and A. Clark Differentiation and pyroxene relation in the Deccan Trap. Murty, T. New Delhi. Murali, A. Sankar Das and U. Aswathanarayana Mount Girnar complex, western India, as a possible continental analog of Iceland.
Murty, M. Mishra Najafi, S. Cox and R. Sukheswala Naqvi, S. Divakara Rao and Hari Narain The protocontinental growth of the Indian Shield and the antiquity of its rift valleys. Ness, G. Levi and R. Couch Marine magnetic anomaly timescales for the Cenozoic and Late Cretaceous: a precis, critique, and synthesis. Space Phys. Norton, I. Sclater A model for the evolution of the Indian Ocean and the breakup of Gondwanaland.
Officer, C. Drake Terminal Cretaceous environmental events. Science , — Drake and J. Devine Volcanism and Cretaceous-Tertiary extinctions. Thermal history of magmas: the low pressure reference point.
Mathews Geochemical evolution in an advancing, periodically replenished, periodically tapped, continuously fractionated magma chamber. Pal, P. Palaeomagnetic reversals in the Deccan Traps. Bindu Madhav and V. Bhimasankaram Early Tertiary geomagnetic polarity reversals in India.
Pande, K. Macdougall, P. Krishnamurthy, K. Gopalan, A. Murali and D. Blanchard Deccan Province alkali basalts and xenoliths: isotope systematics abstract. Terra Cognita 6, — Pascoe, E. Paul, D. Potts, D. Rex and R. Beckinsale Geochemical and petrological study of the Girnar igneous complex, Deccan volcanic province, India. Kresten, T. Ray Barman, R. McNutt and A. Brunfeld Geochemical and petrographic relations in some Deccan basalts, W.
Maharashtra, India. Patriat, P. Achache India-Eurasia collision chronology has implications for crustal shortening and driving mechanism of plates. Peirce, J. The northward motion of India since the Late Cretaceous. Phadke, A. Sukhtankar Topographic studies of Deccan Trap hills around Poona, India. Poornachandra Rao, G. Bhalla Palaeomagnetism of Dhar traps and drift of the subcontinent during the Deccan volcanism. Powar, K.
Linearnent fabric and dyke pattern in the western part of the Deccan volcanic province. The Cambay triple-junction. Powell, C. A speculative tectonic history of Pakistan and surroundings: some constraints from the Indian Ocean.
In: Geodynamics of Pakistan , 5— Price, R. Kennedy, M. Sneeringer and F. Frey Geochemistry of basalts from the West Indian Ocean triple junction: implications for the generation and evolution of Indian Ocean ridge basalts. Qureshy, M. Gravity anomalies, isostasy and crust mantle relations in the Deccan Trap and contiguous regions, India.
Raghavendra Rao, V. Data on subsurface distribution of Deccan Trap. Raja Rao, C. Sahasrabudhe, S. Deshrnukh and R. Raman Distribution, structure and petrography of the Deccan Trap, India. Survey Ind. Raju, A. Chaube and L.
Chowdhary Deccan Trap and the geologic framework of the Cambay Basin. Rarna, S. Potassium-argon dates of some samples from Deccan Traps. Ramanathan, S. Catastrophic eruption rates? Thordarson, pers. A large proportion of the Deccan basalts comprise pahoehoe compound lava flows e. My own fieldwork at scores of places in the Deccan, and on the Kilauea volcano, Hawaii Sheth , , shows that the size and scale of individual flow units of many large Deccan compound flows are the same as those of modern Kilauea lava flows Figure 5.
The large volumes of the individual Deccan lava flows compared to the Hawaiian flows may reflect in part the great amount of decompression during India-Seychelles continental breakup Figure 2 inset , considerable lengths 40 — 50 km of the fissure systems Figure 6; see also Self et al.
Figure 5. The front is about 1 m from the camera and 0. Ropes are forming in the frontal part and satellite breakouts emerge at right and left bright yellow portions. Kilauea, Hawaii, May This is how I believe the compound pahoehoe flows of the Deccan were emplaced. Note how numerous lobes are juxtaposed laterally and vertically. Kilauea, May Photo by Jyotiranjan Ray. This is how many compound pahoehoe flows of the Deccan look. Compare with c. Some 17 flow units are seen.
Modified from Walker Compare with a and b. Figure 6. Map of the Dediapada dyke swarm in the Narmada-Satpura region of the Deccan after Krishnamacharlu, This is one of the large, spectacular oriented dyke swarms of the Deccan Traps. Geochemical studies of these dykes are currently underway. Elevations are in metres. Internal age progression? None exists within the Deccan Figure 3. However, a this activity is not minor; large volumes of lava are emplaced in the subsurface along the west coast, and there is a scarcity of geochronological data.
In comparison, the Western Ghats section has been heavily sampled and dated. It is not. For example, according to prevalent views the plume head was all consumed in a quick phase around 66 — 65 Ma, and the predicted 60 Ma volcanic basement to the south of India, on top of the Maldives Ridge, should have formed from the narrow — km wide plume tail.
It is not clear how this plume tail could produce basalt in Bombay, 1, km to the north, at Suggestions such as northward dragging of the plume tail by the plate are ad hoc , and such drag and tilting would make impossible any systematic age progression in the first place.
Enriched mantle: plume or continent? Smith proposed that ocean-island volcanism is derived from enriched continental mantle delaminated from a continent rifted along an ancient suture see also Lithospheric delamination page. However such compositions may instead mark involvement of shallow-level, enriched continental mantle. However, if continental mantle is introduced into the oceanic mantle, e.
Mahoney et al. They opined that some of these may represent pre-Deccan oceanic seamounts. The associated intrusions were emplaced in continental shelf-and-slope-type marine sediments along the northern margin of India.
Nevertheless, the analyzed intrusions are located within the boundary of the Indian continental mantle, and the true oceanic seamounts may not have been far from the northern margin of India. Continental mantle delaminated during the early stages of India-Seychelles breakup could have migrated northward ahead of India and fed the seamounts built on oceanic lithosphere.
The continent followed behind, and when it converged upon Asia it simply overrode these seamounts. This is a better explanation for the observations than the plume model. The rocks analyzed by Mahoney et al. It may be explained by southward crack propagation through the oceanic lithosphere see below.
The Cambay triple junction and other fiction. This geophysical feature may even be a recent post-Deccan development Sheth , a. Pre-volcanic lithospheric uplift, or lack thereof? Pre-volcanic lithospheric uplift of up to a few kilometres is an essential prerequisite for all thermal models such as the plume model. This is yet another issue on which specialists of different flood basalt provinces have come to diametrically opposed conclusions e.
Pachmarhi is on the Satpura horst between the Tapi and Narmada rifts. The very youthful landscape e. The same is true of the Deccan plateau region, where the Deccan-basement contact is in the subsurface over vast areas. Major rivers draining the Deccan plateau are of the antecedent type, i. The uplift of the Western Ghats is post-volcanic and recent possibly Miocene and younger , and not pre-volcanic uplift produced by a plume Sheth , a.
There are two possible interpretations: 1 Pre-volcanic lithospheric uplift occurred and then completely decayed and was overprinted by post-volcanic uplift.
This is what plume proponents advocate. Option 2 is more plausible, and there is in fact actual support for it in the form of an uplifted, extensive planation surface below the Deccan lavas in central India Dixey , ; see Sheth , a. Note that the Western Ghats rise much higher in southern India the region little or not affected by Deccan volcanism than they do in the Deccan plateau region Figure 7.
Figure 7. The main elements of the physiography of the Indian peninsula. The Western Ghats escarpment is shown by the heavy broken line. Note the pronounced easterly drainage. Palaeolatitudes: true polar wander or crack propagation? To explain this significant discrepancy in the framework of the plume model, some workers have proposed true polar wander TPW of the Earth's mantle e. Such speculation indicates well the extent of special pleading permitted within the plume model.
Within a year two other teams independently discovered planktic foraminifera in intertrappean sediments in central India Jhilmili, Madhya Pradesh. These new discoveries and improved age dating have now brought Deccan volcanism to front and center in the mass extinction debate.
Increasingly, scientists are recognizing the importance of Deccan volcanism and their global effects are being investigated. Deccan Volcanism is no longer the unspoken elephant in the room, but rapidly emerging as the critical and even most likely cause for the KTB mass extinction.
Here we highlight the scientific discoveries by our multi-disciplinary international team of investigators that have revitalized the mass extinction debate and opened the way for new studies across disciplines to evaluate the role of Deccan volcanism in the KTB mass extinction. This hotspot is still active today and last erupted on April 7, The DVP is one of the largest volcanic eruptions in Earth history and today covers an area of , km2, or about the size of France, or Texas.
The original size prior to erosion is estimated to have been at least twice as large. The thickness however rapidly become less further east and varies much at different places.
Towards the southern limit it is between to meter at Amarkantak, the eastern limit, the thickness is meter while in Sind. In Kutch the traps are about meter in thickness. The individual lava flows varies from few feet to 36m.
The bore hole at Bhusawal, m deep revealed 29 flows. Although the flows enter generally horizontal in their deposition, some are slightly inclined of around In Kutch they overlies Jurassic rocks.
In Narmada valley they overlie the Bagh bed and near Jabalpur they overlie lameta bed. All these rocks are called infratrappeans that is the rock live below the traps.
But this is more applicable to youngest among them namely Bagh beds and lameta beds. Upper trap m -bombay and Kathiawar Middle trap m -Central India and Malwa Lower trap m -central province and eastern areas. The lower beds measuring of about m consist of number of fossiliferous intertrappean layers of volcanic ash occur rarely in association with lower flows.
The lower flows rests over lameta beds in M. P, bagh beds in Narmada. The upper flows are well developed characteristically in Bombay, Kathaiwar and kutch. They are about m and contain numerous ash beds and intertrappean beds 9.
In amygdalular flows the top is usually highly vesicular, the middle fairely compact and bottom showing cylindrical pipes filled with secondary minerals. Ash beds are seen in many parts of upper traps they are brecciated structure, fragments of trap being found in a matrix of fine grained material. Columnar joints in the traps are seen in some places.
The common rock type is basalt. Black or greenish black in colour, compact. Sometimes exihibit vesicular or amygdaloidal structure. The specific gravity varies from 2,9 to 3. It is generally composed of Labrodorite Plagioclase Enstatite. Olivine and titaniferous magnetite occur as accessory mineral.
It generally exihibit sub Ophilitic texture inter granular texture is also noticed. So the age of Deccan traps cannot be accurately determined we have to determined intertrappeans that is on the stratigraphic position.
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