Evidence for seafloor spreading in the Laxmi Basin, northeastern Arabian Sea

doi:10.1016/0012-821X(94)90216-X

Earth and Planetary Science Letters

Volume 125, Issues 1–4, July 1994, Pages 211-220

https://doi.org/10.1016/0012-821X(94)90216-X Get rights and content

Abstract

Marine magnetic anomaly data from the Laxmi Basin for the first time reveal the presence of fairly correlatable NNW-trending magnetic lineations. These magnetic lineations are symmetric about a central negative magnetic anomaly and the axis of symmetry coincides with a characteristic short-wavelength free-air gravity low. The anomalies are interpreted as representing a two-limbed seafloor spreading sequence which can be equated to the A28–A33 interval of the geomagnetic polarity reversal timescale. These results suggest that the Laxmi Basin is underlain by an oceanic crust. Evidence of seafloor spreading in this basin possibly implies a pre-A27 spreading episode in the evolutionary history of the Arabian Sea.

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Morphotectonics of the Raman-Panikkar-Wadia seamount chain in the Laxmi Basin, Eastern Arabian Sea
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The Laxmi Basin, which is a deep ocean basin situating adjoining to the northwestern continental margin of India, contains a linear seamount chain consisting of the Raman Seamount, Panikkar Seamount and the Wadia Guyot, located over the axial basement high in the Laxmi Basin representing the Panikkar Ridge. The geomorphology of this seamount chain was studied by earlier researchers; however, its characteristic geophysical signatures, possible genesis and age of formation remains to be clearly established. We attempted for a detailed understanding of the morphological characteristics and the geophysical signatures over the spatial extent of these seamounts using a fresh set of multibeam bathymetry data and sea-surface gravity and magnetic anomalies, complemented by the existing seismic reflection sections. Based on the seafloor and basement topography signatures observed together from the multibeam bathymetry data and the seismic reflection sections, we infer that all the three seamounts are associated with the presence of surface/subsurface secondary peaks on their central parts. The free-air gravity anomaly maps show that the seamounts are associated with a very short wavelength gravity high, superimposed on the short wavelength gravity low representing the Panikkar Ridge. The magnetic anomaly maps suggest that all these seamounts are associated with complex magnetic signatures. Based on the presence of morphological features that are generally associated with the volcanic activity and by considering the above complex geophysical signatures and the updated magnetic isochron map of the Laxmi Basin, we support multiphased volcanic origin for the Raman-Panikkar-Wadia seamount chain, emplaced at an age younger to 63.28 Ma.
Réunion plume associated flood basalt volcanism on the northwestern continental margin of India and related tectonics
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Late Cretaceous Deccan flood basalt province in central-western India was formed by the Réunion plume and continues to attract global attention due to its enormous volume and volcanic eruption straddling the K-T boundary. Furthermore, despite having a profound impact on crustal architecture of the Northwestern Continental Margin of India (NWCMI), very little information about the flood basalt extension in the NWCMI is reported. Therefore, it is necessary to document areal extent and volume of the flood basalt on the NWCMI. In this study, bathymetry, gravity, magnetic and seismic data are integrated to delineate the spatial extent and volume of offshore flood basalt. Crustal architecture, and the role of Réunion plume in evolution of the NWCMI are also discussed. According to the findings of this study, Réunion plume associated flood basalt has carpeted the entire NWCMI up to the Laxmi Ridge. It is also found in the Laxmi Basin, regardless of its crustal nature (continental/oceanic), which is still debated. The results revealed that the flood basalt occurs at depth of 500-7500 m and its thickness varies from few meters to 3900 m. The study also discovered several magmatic intrusions into the crust, which altered initial crustal configuration of the NWCMI. The study revealed an extrusive area of ∼5.37 × 10⁵ km² and a volume of ∼6.59 × 10⁵ km³ of lava flow in the NWCMI. The estimated offshore surface area covered with the Réunion plume associated flood basalt is 7% larger than the Deccan trap-covered surface area on the adjacent onshore region.
Geodynamic events leading to formation of passive western continental margin of India
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Citation Excerpt :
These Tp estimates are significantly higher than the widely accepted Tp of MORB (1350 °C; Hole and Natland, 2020) and such high Tps are common in continental rift tectonic regimes (Rooney et al., 2012). The sea floor anomalies reported in the LB (Bhattacharya et al., 1994) were believed to be obtained without considering a critical factor of basement topography (Collier et al., 2008). Furthermore, a recent study (Mishra et al., 2018) demonstrated that the magnetic anomalies over the LB cannot be correlated with any seafloor spreading type magnetic signature and its P-wave velocity structure is totally different from the nearby oceanic crust.
The geodynamic events of continental breakup and origin of northwest Indian Ocean led to the development of passive continental margin, off western India. However, causal mechanisms and relative chronology of these geodynamic events are not clearly known because of complex regional-scale ridges-basin physiography, multi-stage rifting in a short-time span and thick sediment cover. The Laxmi and adjacent Gop basins constitute key tectonic elements and geophysical investigations on them have come up with sharply divergent explanations of continental rifting and ocean spreading. We present geochemical results of the Laxmi Basin (LB) basement, recovered by the International Ocean Discovery Program Expedition-355 and interpreted in light of existing geophysical results. The basement is identified as continental rift basalt, different from the Deccan/Madagascan basalts. We suggest the basement eruption at ~75 Ma causing igneous underplating which triggered the extension/rifting in Laxmi and Gop basins. The rifting translated into ocean spreading only in the Gop Basin and not in the Laxmi Basin. The geodynamic events echoed soon with similar relative chronology in western India with Reunion plume impact and the Deccan eruption followed by second extension/rifting that culminated in India-Seychelles breakup.
Seismic stratigraphy and the sedimentation history in the Laxmi Basin of the eastern Arabian Sea: Constraints from IODP Expedition 355
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Detailed interpretation of seismic stratigraphic sequences in the Laxmi Basin of the eastern Arabian Sea are presented in this study using closely spaced high resolution multi-channel seismic (MCS) data. Our stratigraphic interpretation is further corroborated using recent drilling results in the Laxmi Basin, derived from the long sediment cores collected during International Ocean Discovery Program (IODP) Expedition 355. Integrated core-log interpretation discussed in the present study, offer important insights about the lithostratigraphic variations in this region. Analyses of multi-channel seismic reflection data reveal five depositional sequences (ranging from Paleocene to Recent) that led to the development of this marginal basin since the Cenozoic period. Regional igneous basement is successfully imaged, which was also validated by deep sea coring during the IODP Expedition 355. In the present study, we primarily focus on the post-rift sedimentation in the Laxmi Basin and its possible mechanisms. Our detailed interpretation in the prevailing tectonic framework of the basin suggests that near-shelf oldest volcaniclastic sedimentation immediately overlying the acoustic basement is linked to the onset of India–Madagascar and India–Seychelles rifting activities during the Late Cretaceous period. Eventually, during the Early-Mid to Late Miocene, the basin received maximum sedimentation dominantly through an extensive mass transport mechanism implying possible large-scale deformation on the Indian shelf. Subsequent sediment input to the basin appears to have been fed variably via the Indus Fan as well as coastal discharge from the Indian mainland. The total sediment thickness in the Laxmi Basin ranges from 1.1 to 3.5 km. New stratigraphic information and sediment isopach maps presented here provide vital information about syn- and post-rift sedimentation pattern in the region and their long term tectonic implications.
Does the Laxmi Ridge continue towards the Laccadive Ridge? New insights from an integrated geophysical study
2020, Journal of Asian Earth Sciences
The Laxmi and Laccadive ridges are two major aseismic ridges in the NW Indian Ocean. Bathymetry, gravity and magnetic data and their derivatives are analyzed and modelled to assess interrelationship between both the ridges as well as to establish their crustal structure, nature and isostatic compensation. Boundaries of the Laxmi and Laccadive ridges are delineated by tilt derivative with constraints from available seismic-sections. Integrated gravity and magnetic models reveal that both the ridges have almost similar crustal layers and are underplated all along its length. Crustal models also depict that both the ridges are carpeted with flood basalt and heavily intruded. 3D coherence between mantle Bouguer anomaly and residual bathymetry reveals that the elastic plate thickness and subsurface to surface load ratio for both the ridges vary from 3 to 4 km and 0.7 to 0.8, respectively. Several characteristic similarities viz. crustal structure and nature, elastic plate thickness, magmatism have been observed for both the ridges. Seismic sections near the junction of the ridges suggest that the basement high corresponding to the Laxmi Ridge is further continued towards the Laccadive Ridge. In addition, the northwestern part of the Laccadive Ridge has NW-SE structural lineaments similar to that of the NW-SE segment of the Laxmi Ridge. Based on results of the present and previous studies, we infer that (i) the Laxmi Ridge is extended southeastward towards the Laccadive Ridge, (ii) both the ridges are continental slivers which are underplated as well as intruded and carpeted by volcanics, and (iii) both the ridges are locally compensated.
Buried channels provide keys to infer Quaternary stratigraphic and paleo-environmental changes: A case study from the west coast of India
2019, Geoscience Frontiers
Citation Excerpt :
Whereas, the northern continental shelf was evolved during short span of rifting between Seychelles-Laxmi Ridge and India in the Late Cretaceous. The resulting structural features of the shelf and adjacent continental margin were modified by the Réunion hotspot activity (Bhattacharya et al., 1994; Chaubey et al., 2002; Minshull et al., 2008; Yatheesh et al., 2009; Bhattacharya and Yatheesh, 2015). The geomorphology of the marginal part of western India is mostly controlled by the three principal structural trends: Dharwar NNW–SSE, Aravalli NE–SW, and Narmada graben E–W.
High resolution shallow seismic data was acquired from inner continental shelf of Goa, west coast of India to map underlying stratigraphic and buried geomorphic features of shelf strata. Seismic data revealed characteristic channel incisions beneath 4–15 m thick sediment layer and corresponds to multi cycle incisions. Stratigraphic analysis of these incision signatures reveals three prominent subaerial unconformities S6, S7 and S9. These unconformities were exposed during the last glacial, penultimate glacial (MIS-6) and prior to penultimate glacial (MIS-8) periods. On the basis of interpreted age of subaerial unconformities and differences in their morphological features, observed channel incisions have been divided grossly into three phases of incision. Phase-1 incisions are older than ∼330 kyr BP, whereas, incisions of Phase-2 and Phase-3 correspond to ∼320–125 kyr BP and ∼115–10 kyr BP respectively. Plan form of these incisions varied from a straight channel type to ingrown meander and then to anastomosing channel types. These channels meet at the confluence of present-day Mandovi and Zuari rivers. The confluence point has varied in due course of time because of cyclic incision and burial with repeated sea level fluctuations. The preserved main channel width varies from ∼100 m to 1000 m, and maximum channel depth reaches up to ∼35 m. Comparison of quantitative and qualitative morphologic results of different phases of incisions suggest that Phase-2 channels had ∼33% more mean bank full discharge than that of the Phase-3 channels. Phase-2 incisions had been carved in higher hydraulic energy condition as compared to Phase-3 incisions implying that the Indian summer monsoon was better during formative stages of Phase-2 incisions.

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Evidence for seafloor spreading in the Laxmi Basin, northeastern Arabian Sea

Abstract

Mar. Pet. Geol.

Mar. Geol.

Tectonophysics

Earth Planet. Sci. Lett.

Earth Planet. Sci. Lett.

A geological and geophysical study of the continental margin of western India, and the adjoining Arabian Sea including the Indus Cone

Structural framework and the evolutionary history of the continental margin of western India

Western continental margin of India and hydrocarbon potential of deep-sea basins

Tectonic evolution of the Coral Sea basin

J. Geophys. Res.

Echosounding correction tables (formerly Matthew's tables)