Structural lineaments from the magnetic anomaly maps of the eastern continental margin of India (ECMI) and NW Bengal Fan

Murthy, K. S. R.; Rao, T.C.S.; Subrahmanyam, Avanidhar; Rao, M.M.M.; Lakshminarayana, S.

doi:10.1016/0025-3227(93)90046-x

Cited by 34 publications

(21 citation statements)

References 9 publications

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“…Murthy et al (1993Murthy et al ( , 1995 reported the presence of neotectonic activity in the study area. The long-wavelength low-relief subsurface swell/anticline in the vicinity of the inferred WNW-ESE-trending sedimentary ridge is due to the effect of shale diapirism (Sahu 2005).…”

Section: Discussionmentioning

confidence: 99%

Multidisciplinary investigations exploring indicators of gas hydrate occurrence in the Krishna–Godavari Basin offshore, east coast of India

et al. 2008

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We report some main results of multidisciplinary investigations carried out within the framework of the Indian National Gas Hydrate Program in [2002][2003] in the Krishna-Godavari Basin offshore sector, east coast of India, to explore indicators of likely gas hydrate occurrence suggested by preliminary multi-channel seismic reflection data and estimates of gas hydrate stability zone thickness. Swath bathymetry data reveal new evidence of three distinct geomorphic units representing (1) a delta front incised by several narrow valleys and mass flows, (2) a deep fan in the east and (3) a WNW-ESE-trending sedimentary ridge in the south.Deep-tow digital side-scan sonar, multi-frequency chirp sonar, and sub-bottom profiler records indicate several surface and subsurface gas-escape features with a highly resolved stratification within the upper 50 m sedimentary strata. Multi-channel seismic reflection data show the presence of bottom simulating reflections of continuous to discrete character. Textural analyses of 76 gravity cores indicate that the sediments are mostly silty clay. Geochemical analyses reveal decreasing downcore pore water sulphate (SO 4 2− ) concentrations (28.7 to <4 mM), increasing downcore methane (CH 4 ) concentrations (0-20 nM) and relatively high total organic carbon contents (1-2.5%), and microbial analyses a high abundance of microbes in top core sediments and a low abundance of sulphate-reducing bacteria in bottom core sediments.Methane-derived authigenic carbonates were identified in some cores. Combined with evidence of gasescape features in association with bottom simulating reflections, the findings strongly suggest that the physicochemical conditions prevailing in the study area are highly conducive to methane generation and gas hydrate occurrence. Deep drilling from aboard the JOIDES Resolution during 2006 has indeed confirmed the presence of gas hydrate in the KrishnaGodavari Basin offshore.

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Section: Discussionmentioning

confidence: 99%

Multidisciplinary investigations exploring indicators of gas hydrate occurrence in the Krishna–Godavari Basin offshore, east coast of India

et al. 2008

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“…The reduction in the width of this quiet zone in the northern part may be attributed to the influence of the magnetic anomaly due to the 85°E ridge abutting the continental shelf of Chilka Lake in ECMI. Studies by Mukhopadhyay and Krishna (1992) and Murthy et al (1993) indicate that the landward limit of this quite zone is bounded by the COB at the foot of the continental slope. Following Kent and Gradstein (1986), the COB coincides with the M0 (118 Ma) anomaly in the Bengal Fan.…”

Section: Cretaceous Magnetic Quiet Zone In the Bengal Fanmentioning

confidence: 96%

“…5c) respectiely. Curray and Munasinghe (1991) and Murthy et al (1993) were of the opinion that the 85°E ridge extends to the Indian continental margins. Present data indicate that the 85°E ridge abuts Chilka Lake in the Eastern Continental Margin of India.…”

Section: °E Lineamentmentioning

confidence: 99%

Magnetic expression of some major lineaments and Cretaceous quiet zone in the Bay of Bengal

et al. 1997

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Magnetic data over the eastern continental margin of India and adjacent Bengal fan demarcate two major lineaments. A high amplitude N-S-trending lineation of the Cauvery offshore Basin corresponds to the offshore fragment of the 80°E lineament recorded onland. A N-S lineation of very high amplitude anomaly off Chilka lake considered as the possible northward extension of the 85°E ridge delineated, hitherto in Bengal Fan. A subdued magnetic anomaly zone is demarcated seaward of the continent-ocean boundary (COB) in the Bengal Fan. Over the northern Bengal Fan this zone is delineated east of 85°E lineation. This quiet zone might have evolved during the Early Cretaceous period of normal magnetic polarity between M0 and 34 (120-84 Ma) anomalies.

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“…The anomaly on this map seems to be incomplete in the SE. However, in the southeastern region, there are several marine magnetic profiles, which are published by Murthy et al (1993) and Subrahmanyam et al (1994). These marine magnetic profiles are spaced at about 10 km intervals.…”

Section: Aeromagnetic and Marine Magnetic Datamentioning

confidence: 98%

“…Earlier, several geophysical studies (Babu Rao et al 1982;Jagannathan et al 1983;Mishra 1984;Mukhopadhyay and Krishna M 1992;Murthy et al 1993;Subrahmanyam et al 1994, Gopal Rao et al 1997, Chand et al 2001, Nayak and Rama Rao 2002) based on magnetic, gravity and seismic data over the ECMI were made. Babu Rao et al (1982) mentioned about the conspicuous shelf magnetic anomaly on the aeromagnetic map of the offshore Mahanadi basin.…”

Section: Previous Geophysical Studiesmentioning

confidence: 98%

Magnetic Evidence for Volcanism at Eastern Continental Margin of India: Juxtaposition with Elan Bank (Southern Indian Ocean)

Sarma

2008

Surv Geophys

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The rifted Eastern Continental Margin of India (ECMI) has evolved as a result of breakup of East Gondwanaland. Previous geophysical studies of the continental margin have not elucidated upon its volcanic nature. Magnetics plays a useful role in the study of continental margins, particularly in identifying the volcanic units. The aeromagnetic map of the offshore Mahanadi basin of ECMI displays a conspicuous linear anomaly along the continental shelf. A comprehensive study of the published aeromagnetic, marine magnetic and gravity data of the offshore Mahanadi basin reveals the existence of a seaward dipping volcanic unit in the offshore Mahanadi basin bordering the Hinge zone. This inference suggests that the ECMI is a volcanic rifted margin. The study further indicates the deepening of the basement towards the sea. In addition, the existing geological studies on the ECMI demarcated the probable limit of the continental crust by studying the basement detached tectonic style of the sedimentation in sub-surface configuration of the East coast basins of India. The probable continental crustal limit, the Hinge zone, and the inner edge of the presently inferred volcanic unit conform to one another spatially in the offshore Mahanadi region. These features characterize the inferred volcanic body as seaward dipping reflectors (SDRs) that usually occur at the rifted continental margins. The deepening of the basement towards the sea and the presence of the volcanic body on the continental margin are indicative of the transitional nature of the crust. It is generally accepted that Antarctica and India were juxtaposed before the breakup of Gondwanaland. But the microcontinents in the southern Indian Ocean are neglected in the reconstruction of Gondwanaland continents. The recent studies of the discovery of continental crust within the Elan Bank (EB) microcontinent show that the EB was contiguous with the East coast of India before the breakup of Gondwanaland. Moreover, it is reported that the upper igneous crust of the EB consists of a 2-3 km thick layer of accumulated lava flows originating from the Kerguelen hotspot. An estimate shows that the total volume of volcanic and plutonic component of the Elan Bank is about 0.3 million cubic kilometers. The present inference of a volcanic body from the offshore Mahanadi basin is in agreement with the above observations of the juxtaposition of EB with ECMI.

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Structural lineaments from the magnetic anomaly maps of the eastern continental margin of India (ECMI) and NW Bengal Fan

Cited by 34 publications

References 9 publications

Multidisciplinary investigations exploring indicators of gas hydrate occurrence in the Krishna–Godavari Basin offshore, east coast of India

Multidisciplinary investigations exploring indicators of gas hydrate occurrence in the Krishna–Godavari Basin offshore, east coast of India

Magnetic expression of some major lineaments and Cretaceous quiet zone in the Bay of Bengal

Magnetic Evidence for Volcanism at Eastern Continental Margin of India: Juxtaposition with Elan Bank (Southern Indian Ocean)

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