Large fault fabric of the Ninetyeast Ridge implies near‐spreading ridge formation

Sager, William W.; Paul, C. F.; Krishna, K. S.; Pringle, Malcolm S.; Eisin, A. E.; Frey, Frederick A.; Rao, D. Gopala; Левченко, О. В.

doi:10.1029/2010gl044347

Cited by 30 publications

(31 citation statements)

References 23 publications

(35 reference statements)

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“…Earlier derived crustal models show the presence of thicker crust with and without underplating below these ridges (Detrick and Watts, 1979;Mukhopadhyay and Krishna, 1995;Subrahmanyam et al, 1999;Grevemeyer et al, 2001;Krishna et al, 2001b;Krishna, 2003;Subrahmanyam et al, 2008;Radhakrishna et al, 2010). The present analysis revealed that both ridges, in general, are earlier investigators for the ridge south of 2ºN revealed that this part of the ridge had evolved due to frequent ridge jumps in the vicinity of the Kerguelen hot spot during the rapid northward migration of the Wharton spreading ridge (Royer et al, 1991;Krishna et al, 1999;Sager et al, 2010;Krishna et al, 2012). The modeled lithosphere structure across these ridges suggests a lack of plume impact at the LAB, although there is minor eastward thinning beneath the Ninetyeast Ridge.…”

Section: Geodynamic Implicationssupporting

confidence: 64%

Lithosphere structure and upper mantle characteristics below the Bay of Bengal

et al. 2016

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SUMMARY:The oceanic lithosphere in the Bay of Bengal (BOB) formed 80 -120 Ma following the breakup of eastern Gondwanaland. Since its formation, it has been affected by the emplacement of two long N-S trending linear aseismic ridges (85 o E and Ninetyeast) and by the loading of ca.20-km of sediments of the Bengal Fan. Here, we present the results of a combined spatial and spectral domain analysis of residual geoid, bathymetry and gravity data constrained by seismic reflection and refraction data. Self-consistent geoid and gravity modeling defined by temperature-dependent mantle densities along a N-S transect in the BOB region revealed that the depth to the Lithosphere-Asthenosphere boundary (LAB) deepens steeply from 77 km in the south to 127 km in north, with the greater thickness being anomalously thick compared to the lithosphere of similar-age beneath the Pacific Ocean. The Geoid-Topography Ratio (GTR) analysis of the 85°E and Ninetyeast ridges indicate that they are compensated at shallow depths.

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Section: Geodynamic Implicationssupporting

confidence: 64%

Lithosphere structure and upper mantle characteristics below the Bay of Bengal

et al. 2016

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“…E‐W bathymetric lineations also occur at this site; however, they are not as distinct as at Sites 216 and 758. The most prominent lineation is the trough at the south flank of the seamount, which is a large graben that was probably formed during the construction of the NER [ Sager et al ., ]. Other lineations have similar trends crossing the top of the seamount, with several being traced across the entire summit (Figure ).…”

Section: Ner Fault Observationsmentioning

confidence: 99%

“…Many different authors have explained the formation of the NER as a result of various tectonic anomalies [see review by Royer et al ., ], but the modern consensus is that it was created by hot spot volcanism that emplaced a ridge on the northward drifting Indian plate from Late Cretaceous to early Cenozoic time [ Royer et al ., ; Krishna et al ., ]. The hot spot was often located near the spreading ridge [ Sager et al ., ; Krishna et al ., ] and changes in NER morphology may be related to the proximity of the hot spot to the spreading ridge [ Royer et al ., ]. Because of its near‐ridge location, the hot spot emplaced material on both the Indian and Antarctic plates, with most of the volcanic product ending up on the India plate owing to repeated southward ridge jumps [ Krishna et al ., ].…”

Section: Introductionmentioning

confidence: 99%

Active faulting on the Ninetyeast Ridge and its relation to deformation of the Indo‐Australian plate

2013

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The ~4500 km long Ninetyeast Ridge (NER) in the northeastern Indian Ocean crosses a broad zone of deformation where the Indo‐Australian plate is fracturing into three smaller plates (India, Capricorn, Australia) separated by diffuse boundaries whose extents are poorly defined. New multichannel seismic reflection profiles image active faults along the entire length of the NER and show spatial changes in the style of deformation along the ridge. The northern NER (0°N–5°N) displays transpressional motion along WNW‐ESE faults. Observed fault patterns confirm strike‐slip motion at the western extent of the April 2012 Wharton Basin earthquake swarm. In the central NER (5°S–8°S), deformation on WNW‐ESE‐trending thrust faults implies nearly N‐S compression. An abrupt change in fault style occurs between 8° and 11°S, with modest, extension characterizing the southern NER (11°S–27°S). Although extension is dominant, narrow zones of faults with strike‐slip or compressional character also occur in the southern NER, suggesting a complex combination of fault motions. At all sites, active faulting is controlled by the reactivation of original, spreading‐center formed, normal faults, implying that deformation is opportunistic and focused along existing zones of weakness, even when original fault trend is oblique to the direction of relative plate motion. Observed faulting can be interpreted as India‐Australia deformation in the northern NER and Capricorn‐Australia deformation in the southern NER. The India‐Capricorn boundary is directly adjacent to the northern NER and this juxtaposition combined with a different style of faulting to the east of the NER imply that the ridge is a tectonic boundary.

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“…The seafloor morphology of the NER all along its length (Figures and ) is quite variable. As noticed previously [ Sclater and Fisher , ; Krishna et al ., , ; Sager et al ., , ], south of 10°S, the ridge feature is prominent and continuous with an average width and relief of 200 and 3 km, respectively. The NER segment between 10°S and equator has distinct morphology of isolated rises with a narrow width of ~100 km.…”

Section: Analyses Of Bathymetry Gravity Geoid and Sediment Thicknementioning

confidence: 99%

Spatial variations in isostatic compensation mechanisms of the Ninetyeast Ridge and their tectonic significance

Sreejith

Krishna

2013

JGR Solid Earth

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[1] The Ninetyeast Ridge (NER), one of the longest linear volcanic features on the Earth, offers an excellent opportunity of understanding the isostatic response to the interactions of mantle plume with the migrating mid-ocean ridge. Bathymetry, geoid, and gravity (shipborne and satellite) data along 72 closely spaced transects and 17 overlapping grids on the NER are analyzed and modeled to determine the effective elastic thickness (Te) beneath the entire ridge. The results of 2-D and 3-D flexural modeling of the NER show large spatial variations in Te values ranging from 4 to 35 km, suggesting that the ridge was compensated along its length by different isostatic mechanisms. The southern (south of 22°S latitude) and northern (north of 2°N latitude) parts of the NER have Te values of >10 and >23 km, respectively, revealing that the southern part was emplaced on a lithosphere of intermediate strength possibly on flank of the Indian plate, whereas the northern part was emplaced in an intraplate setting. In contrast, in the central part of the NER (between latitudes 22°S and 2°N), highly variable Te values (4-22 km) are estimated. The scattered Te values in the central NER suggest that this part may have evolved due to the occurrence of frequent ridge jumps caused by the interaction of Kerguelen hot spot with rapid northward migration of the Wharton spreading ridge. Residual Mantle Bouguer Anomaly (RMBA) map of the NER and adjacent basins reveals that the entire length of the NER is associated with a significant negative anomaly up to 200 mGal, indicating the presence of thickened crust or less dense mantle beneath the ridge. 3-D crustal thickness map of the NER, generated by inversion of the RMBA data, shows a thick crust ranging from 15 to 19 km. The present study clearly shows that NER possesses a highly segmented isostatic pattern with the occurrence of subcrustal underplating or subsurface loading.

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Large fault fabric of the Ninetyeast Ridge implies near‐spreading ridge formation

Cited by 30 publications

References 23 publications

Lithosphere structure and upper mantle characteristics below the Bay of Bengal

Lithosphere structure and upper mantle characteristics below the Bay of Bengal

Active faulting on the Ninetyeast Ridge and its relation to deformation of the Indo‐Australian plate

Spatial variations in isostatic compensation mechanisms of the Ninetyeast Ridge and their tectonic significance

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