The bent prolongation of the 85°E Ridge south of 5°N – Fact or fiction?

Altenbernd, Tabea; Jokat, Wilfried; Geissler, Wolfram

doi:10.1016/j.tecto.2020.228457

Cited by 18 publications

(9 citation statements)

References 33 publications

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“…(e) Comparison of velocity-depth profiles taken between km 50 and 450 with profiles on >7.5 Ma old oceanic crust generated at slow to intermediate and fast to superfast spreading rates (Christeson et al 2019). (f) Comparison of velocity-depth profiles taken between km 50 and 350 with profiles on Indian Ocean oceanic crust (Altenbernd et al 2020) and on line 7 (Charvis & Operto 1999) in the Enderby Basin. (g) Comparison of velocity-depth profiles taken between km 50 and 350 with profiles on the lines 1, P1-87 and P2-87 (Charvis et al 1995), and profiles located on line 4 and line 5 at the SKP .…”

Section: Oceanic Crust (Km 0-470)mentioning

confidence: 99%

Distribution of oceanic crust in the Enderby Basin offshore East Antarctica

Altenbernd-Lang

Jokat

Leitchenkov

2022

Geophysical Journal International

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Summary Seismic reflection and refraction data were collected in 2007 and 2012 to reveal the crustal fabric on a single long composite profile offshore Prydz Bay, East Antarctica. A P-wave velocity model provides insights on the crustal fabric, and a gravity-constrained density model is used to describe the crustal and mantle structure. The models show that a 230 km wide continent-ocean transition separates stretched continental from oceanic crust along our profile. While the oceanic crust close to the continent-ocean boundary is just 3.5–5 km thick, its thickness increases northwards towards the Southern Kerguelen Plateau to 12 km. This change is accompanied by thickening of a lower crustal layer with high P-wave velocities of up to 7.5 km/s, marking intrusive rocks emplaced beneath the mid-ocean ridge under increasing influence of the Kerguelen plume. Joint interpretations of our crustal model, seismic reflection data, and magnetic datasets constrain the age and extent of oceanic crust in the research area. Oceanic crust is shown to continue to around 160 km farther south than has been interpreted in previous data, with profound implications for plate kinematic models of the region. Finally, by combining our findings with a regional magnetic data compilation and regional seismic reflection data we propose a larger extent of oceanic crust in the Enderby Basin than previously known.

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Section: Oceanic Crust (Km 0-470)mentioning

confidence: 99%

Distribution of oceanic crust in the Enderby Basin offshore East Antarctica

Altenbernd-Lang

Jokat

Leitchenkov

2022

Geophysical Journal International

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“…Notable geomorphological features around the Ninety East Ridge include the Osborne Plateau and the Eighty Five East Ridge (85°E Ridge). The latter presents a near-parallel ridge extending along 85°E from the Afanasy Nikitin Seamounts northward to the Mahanadi basin (Krishna, 2003;Krishna et al, 2014;Altenbernd et al, 2020;Bastia et al, 2010). It is formed as a result of the sagging of the Earth's crust (Anand et al, 2010).…”

Section: Seafloor Morphologymentioning

confidence: 99%

Exploring structured scripting cartographic technique of GMT for ocean seafloor modeling: A case of the East Indian Ocean

Lemenkova

2021

Marit. Technol. Res.

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This paper examines spatial variations in the geomorphology of the Ninety East Ridge (NER), located in the Indian Ocean. The NER is an extraordinary long linear bathymetric feature with topography reflecting complex geophysical setting and geologic evolution. The research is based on a compilation of high-resolution bathymetric, geological, and gravity datasets clipped for the study area extent (65° - 107°E, 35°S - 21°N): General Bathymetric Chart of the Oceans (GEBCO), Earth Gravitational Model (EGM2008, EGM96). The submarine geomorphology of the NER was modeled by digitized cross-sectional profiles using Generic Mapping Tools (GMT). The availability of the method is explained by 1) the free datasets; 2) the open source GMT toolset; 3) the available tutorials of the GMT and the codes explained in this work. Three segments of the NER were selected, digitized, and modeled: 1) northern 89°E, 7°S to 90°E, 7°N; 2) central 88.4°E, 14.7°S to 88.8°E, 8.2°S; 3) southern 87.9°E, 17°S to 87.5°E, 27°S. Measured depths were visualized in graphs, compared, and statistically analyzed by the histograms. The northern segment has a steepness of 21.3° at the western slopes, and 14.5° at the eastern slope. The slopes on the eastern flank have dominant SE orientation. The central segment has a bell-shaped form, with the highest steepness comparing to the northern and southern segments. The eastern flank has a steepness of 49.5°. A local depression at a distance of 50 km off from the axis (90°E) continues parallel to the NER, with the shape of the narrow minor trench. The western slope has a steepness of 57.6°, decreasing to 15.6°. The southern segment has a dome-like shape form. Compared to the northern and central segments, it has a less pronounced ridge crest, with a steepness of 24.9° on the west. The eastern flank has a steepness of 36.8° until 70 km, gradually becoming steeper at 44.23°. A local minor trench structure can be seen on its eastern flank (100 km off the axis). This corresponds to the very narrow long topographic depressions stretching parallel to this segment of the NER at 90.5°E. The study contributes to regional geographic studies of Indian Ocean geomorphology and cartographic presentation of GMT functionality for marine research and oceanographic studies.

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“…The area is bounded by the Eastern Ghats mobile belt on the south and the Himalayan foothills on the north. The Gangetic alluvium and the FIGURE 1 | Regional map (reconstructed after Khan et al, 2017b;Valdiya and Sanwal, 2017;Altenbernd et al, 2020) showing the location of the study area (rectangular block demarcated by red dashed line). Abbreviations: AC, Aravalli Craton; BKC, Bundelkhand Craton; CITZ, Central India Tectonic Zone; EGB, Eastern Ghats Belt; CP, Chhotanagpur Plateau; SC, Singhbhum Craton, BC, Bastar Craton; DC, Dharwar Craton; SGT, Southern Granulite Terrain; MG, Mahanadi Graben; GG, Godavari Graben; SM, Shillong Massif; IMR, Indo-Myanmar Range; GR, Ganga River; UGB, Upper Gangetic Basin; LGB, Lower Gangetic Basin; BR, Brahmaputra River.…”

Section: Tectonic Set-upmentioning

confidence: 99%

Crustal Configuration and Seismic Stability of the Eastern Indian Shield and Adjoining Regions: Insights for Incidents of Great Earthquakes in the Nepal-Bihar-Sikkim Himalaya

Singh

Khan

2021

Front. Earth Sci.

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The Eastern Indian Shield (EIS) is comprised of the intracratonic (coal-bearing) Damodar Gondwana basin, rift-controlled extensional Lower Gangetic basin (LGB), and the downward flexed Indo-Gangetic basin (IGB). The present study involves the computations and mapping of the basement configuration, sediment thickness, Moho depth, and the residual isostatic gravity anomaly, based on 2-D gravity modeling. The sediment thickness in the area ranges between 0.0 and 6.5 km, and the Conrad discontinuity occurs at ∼17.0–20 km depth. The depth of the Moho varies between 36.0 and 41.5 km, with the maximum value beneath the Upper Gangetic basin (UGB), and the minimum of ∼36 km (uplifted Moho) in the southeastern part beneath the LGB. The maximum residual isostatic anomaly of +44 mGal in the southern part indicates the Singhbhum shear zone, LGB, and Rajmahal trap to be under-compensated, whereas the northern part recording the minimum residual isostatic anomaly of –87.0 mGal is over-compensated. Although the region experienced a few moderate-magnitude earthquakes in the past, small-magnitude earthquakes are sparsely distributed. The basement reactivation was possibly associated with a few events of magnitudes more than 4.0. Toward the south, in the Bay of Bengal (BOB), seismic activities of moderate size and shallow origin are confined between the aseismic 85 and 90°E ridges. The regions on the extreme north and south [along the Himalaya and the equatorial Indian Ocean (EIO)] are experienced moderate-to-great earthquakes over different times in the historical past, but the intervening EIS and the BOB have seismic stability. We propose that the two aseismic ridges are guiding the lithospheric stress fields, which are being further focused by the basement of the EIS, the BOB, and the N-S extended regional fault systems into the bending zone of the penetrating Indian lithosphere beneath the Himalaya. The minimum obliquity of the Indian plate and the transecting fault systems in the Foothills of the Himalaya channelize and enhance the stress field into the bending zone. The enhanced stress generates great earthquakes in the Nepal-Bihar-Sikkim Himalaya, and on being reflected back through the apparently stable EIS and BOB, the stress field creates deformation and great earthquakes in the EIO.

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The bent prolongation of the 85°E Ridge south of 5°N – Fact or fiction?

Cited by 18 publications

References 33 publications

Distribution of oceanic crust in the Enderby Basin offshore East Antarctica

Distribution of oceanic crust in the Enderby Basin offshore East Antarctica

Exploring structured scripting cartographic technique of GMT for ocean seafloor modeling: A case of the East Indian Ocean

Crustal Configuration and Seismic Stability of the Eastern Indian Shield and Adjoining Regions: Insights for Incidents of Great Earthquakes in the Nepal-Bihar-Sikkim Himalaya

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