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  • 1
    Publication Date: 2022-05-01
    Description: We present results derived from a seismic refraction experiment and gravity measurements about the upper mantle and crustal structure of southern Sri Lanka and the adjacent Indian Ocean. A P-wave velocity model was derived using forward modelling of the observed travel times along a 509 km long, N-S trending profile at 81°E longitude. Our results show that the continental crust below southern Sri Lanka is up to 38 km thick. A ~65 km wide transition zone, which thins seaward to ~7 km thickness, divides stretched continental from oceanic crust. The adjacent, 4.7 to 7 km thick normal oceanic crust is covered by up to 4 km thick sediments. The oceanic crust is characterized by intra-crustal reflections and displays P-wave velocity variations, especially in oceanic layer 2, along our profile. In the central part of the profile, the uppermost mantle layer is characterized by normal P-wave mantle velocities of 8.0 -8.1 km/s. At the southern end of the profile, unusual low upper mantle seismic velocities, ranging from 7.5 to 7.6 km/s only, characterize the uppermost mantle layer. These low upper mantle velocities are probably caused by serpentinized upper mantle. At even greater depths the upper mantle layer is characterized by velocities of 8.3 km/s on average. The type of margin along our profile is difficult to identify, since it is characterized by features typical for different types of margins.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 2
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    Oxford University Press
    In:  EPIC3Geophysical Journal International, Oxford University Press, 231, pp. 1959-1981
    Publication Date: 2022-09-16
    Description: 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–1, 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 data sets 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.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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