Crustal underplating and effective elastic plate thickness of the Laxmi Ridge, northern Arabian Sea

Mishra, Amiyakanta; Chaubey, A.K.; Sreejith, K. M.; Kumar, Shravan

doi:10.1016/j.tecto.2018.06.013

Cited by 9 publications

(3 citation statements)

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“…This feature, which is characterized by a gravity low signature, consists of a ~NW-SE and an E-W trending segment bordering the seaward side of the Laxmi and Gop basins, respectively. There is a broad agreement among the researchers that the Laxmi Ridge is underlain by continental crust (Naini and Talwani, 1982;Bhattacharya et al, 1994a;Talwani and Reif, 1998;Collier et al, 2004;Krishna et al, 2006;Yatheesh, 2007;Collier et al, 2008;Minshull et al, 2008;Collier et al, 2009;Bhattacharya and Yatheesh, 2015;Nair et al, 2015;Mishra et al, 2018). This inference is primarily based on the crustal velocity-depth structure (Naini and Talwani, 1982;Collier et al, 2004;Collier et al, 2009), crustal configuration based on seismicconstrained gravity modeling (Krishna et al, 2006;Yatheesh, 2007;Yatheesh et al, 2009;Nair et al, 2015), admittance analysis (Mishra et al, 2018) and the presence of seaward dipping reflectors (SDRs) on both the landward and seaward sides of the Ridge (Corfield et al, 2010;Calvès et al, 2011;Siawal et al, 2014).…”

Section: Laxmi Ridgementioning

confidence: 99%

Structure and tectonics of the continental margins of India and the adjacent deep ocean basins: current status of knowledge and some unresolved problems

Yatheesh

2020

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March 2020 586 The Indian Ocean and the bordering continental margins are characterized by a number of tectonic features consisting of deep ocean basins, aseismic ridges/ submarine plateaus and seamounts. Marine geophysical studies carried out over these regions for the past four decades have led to an increased understanding of the formation and evolution of these features. The present paper synthesizes an up-to-date compilation of the results of the salient inferences of those studies to describe the structure and tectonic evolution of these features as well as the Indian Ocean in general. A review of the existing knowledge on the structure and tectonics of the continental margins of India and the adjacent ocean basins reveal the existence of several unresolved problems, primarily due to the inherent tectonic complexities or the paucity of adequate data. Some of the major problems that need to be addressed/examined are: the existence and extent of the Prathap and Kori-Comorin ridges; the locations of the continent-ocean boundaries around the continental margins of India; the timing of formation of the deep offshore regions adjacent to the Indian continental margins; the deeper crustal structure and trend of the 85°E Ridge; the crustal configuration as well as the extent of the postulated micro-continental slivers; and the cause of intense seismicity over the Chagos Bank segment of the Laccadive-Chagos Ridge. In addition to addressing these questions, the present paper suggests ways to go forward by acquiring high-resolution and deep penetration multichannel seismic reflection data, seismic refraction data using Ocean Bottom Seismometers (OBS) and closely spaced sea-surface and deep-tow magnetic profiles along with high-resolution seafloor mapping.

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Section: Laxmi Ridgementioning

confidence: 99%

Structure and tectonics of the continental margins of India and the adjacent deep ocean basins: current status of knowledge and some unresolved problems

Yatheesh

2020

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“…Reverse post-rift modelling was performed along this profile to reconstruct subsidence since the end of extension (∼66 Ma). Earlier extension (India-Madagascar break-up) at 130-120 Ma may have affected the WCMI, but the degree of extension is expected to be low in the Laxmi Basin area (Agrawal & Rogers, 1992;Pandey et al 2017;Mishra et al 2018) so that any residual thermal subsidence had largely decayed by the time of the Laxmi Basin opening. A series of restored cross-sections from the present day to ∼66 Ma for line IODP-04 is shown in Figure 8.…”

Section: A Reverse Post-rift Modelling Of Iodp-04mentioning

confidence: 99%

Flexural subsidence analysis of the Laxmi Basin, Arabian Sea and its tectonic implications

Pandey

Clift

et al. 2018

Geol. Mag.

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Two-dimensional flexural backstripping and thermal modelling (assuming laterally variable stretching) is applied along regional depth-converted interpreted seismic profiles from the Laxmi Basin in the Arabian Sea. Results from reverse post-rift flexural modelling reveal considerable basin-wide subsidence in response to the crustal geodynamics during and after the last extensional phase. Unloading of the stratigraphy allows us to estimate the degree of laterally varying extension, assuming thermal subsidence and pure shear. High degrees of extension in the basin centre predict considerable water depths at the time of rift cessation, consistent with deep drilling data. We suggest that regional extension prior to Paleocene time could have fuelled variable subsidence in the Laxmi Basin but that extension is less than seen in typical oceanic lithosphere. Volcanic loading by the seamounts shortly after extension has flexed the basin and implies an effective elastic thickness (Te) at that time of ∼6 km. Reconstruction of the seamount top near sea level at the end of emplacement indicates no major transient uplift potentially linked to the Deccan mantle plume activity. Backstripping of post-rift sediments from interpreted seismic profiles supports the presence of a hyper-thinned crust underneath the Laxmi Basin, with β factors reaching >7 in the basin centre and ∼3 across much of the basin width. Computations of decompacted sediment accumulation rates in light of new results from IODP Expedition 355 show that basin sedimentation peaked during early–middle Miocene time, possibly coeval with uplift and erosion of the Himalayan–Tibetan Plateau driven by strong summer monsoon rains.

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“…We conclude that the lithospheric stretching during the rifting stage followed by Réunion hotspot volcanism must have caused both weakening of lithospheric strength and sub-crustal magmatic underplating beneath the Laccadive Ridge. It is noteworthy that the seismic velocity structure of the Laccadive Ridge closely matches with that of the Laxmi Ridge, which is considered as a continental sliver (Naini and Talwani 1983;Bhattacharya et al 1994;Talwani and Reif 1998;Todal and Eldholm 1998;Radha Krishna et al 2002;Krishna et al 2006;Minshull et al 2008;Mishra et al 2018). The continental nature of the Laccadive Ridge is further supported by the identification of seaward dipping reflectors on seismic reflection profiles from the western flank of the Laccadive Ridge (Ajay et al 2010).…”

Section: Geodynamic Implicationsmentioning

confidence: 56%

Isostasy and crustal structure of the Chagos–Laccadive Ridge, Western Indian Ocean: Geodynamic implications

2019

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The Chagos-Laccadive Ridge (CLR), a prominent linear aseismic ridge in the Western Indian Ocean is believed to be a trace of the Réunion hotspot. In order to understand the mode of emplacement of this ridge and the nature of the underlying crust, we carried out three-dimensional (3D) flexural modelling and coherence analysis of satellite-derived gravity and bathymetry data along the ridge. The analysis revealed variations in Effective Elastic Thickness (T e) along the CLR. While the northernmost part of CLR is associated with low T e of 3 km with a subsurface to surface loading ratio (f) of 1, towards the south, the Maldive Ridge and the Chagos Bank have a fairly uniform T e of 8-10 km with a very low loading ratio f of 0.1-0.2. We consider the Laccadive Ridge as a continental sliver possessing underplated magmatic rocks caused by the Réunion hotspot volcanism. The Maldive Ridge and the Chagos Bank appear to have emplaced on a lithosphere of intermediate strength possibly on the flanks of the Central Indian Ridge.

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Crustal underplating and effective elastic plate thickness of the Laxmi Ridge, northern Arabian Sea

Cited by 9 publications

References 60 publications

Structure and tectonics of the continental margins of India and the adjacent deep ocean basins: current status of knowledge and some unresolved problems

Structure and tectonics of the continental margins of India and the adjacent deep ocean basins: current status of knowledge and some unresolved problems

Flexural subsidence analysis of the Laxmi Basin, Arabian Sea and its tectonic implications

Isostasy and crustal structure of the Chagos–Laccadive Ridge, Western Indian Ocean: Geodynamic implications

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