J. Kim Welford

Comparison of lithosphere structure across the Orphan Basin–Flemish Cap and Irish Atlantic conjugate continental margins from constrained 3D gravity inversions

Regionally constrained 3D gravity inversion results on the Orphan Basin–Flemish Cap and the Irish Atlantic conjugate continental margins are compared to investigate crustal structure, early rifting history and geological evolution of this part of the North Atlantic. The full-crustal density anomaly distributions provide some of the first depth images of how rifted structures compare along and across these conjugate margins. Broad similarities in crustal structure are identified with some noticeable differences, linked to rifting and crustal stretching processes. Extreme crustal thinning (stretching factors >3.5) is indicated beneath much of the southern Porcupine Basin, the western half of West Orphan Basin, the eastern half of Jeanne d’Arc Basin, the southeastern half of East Orphan Basin and in pockets beneath Rockall Basin. This appears to have resulted in the serpentinization (and possible exhumation) of mantle lithosphere on the Irish Atlantic and Flemish Cap margins but not beneath Orphan Basin. A simple evolution model is proposed for the early stages of rifting between the margins. It is suggested that ancient orogenic sutures played an important role in controlling the northward migration of rifting and the rotation and displacement of Flemish Cap out of Orphan Basin. Supplementary material: Enlarged maps from this paper are available at www.geolsoc.org.uk/SUP18527.

Ground-roll suppression from deep crustal seismic reflection data using a wavelet-based approach: A case study from western Canada

Seismic reflection data sets recorded on land are often contaminated by coherent ground-roll noise generated by the propagation of dispersive waves along the free surface. For crustal-scale investigations, this ground-roll contamination can be particularly harmful as the higher amplitude, low-frequency noise overwhelms low-frequency signals coming from deep reflectors. Consequently, conventional ground-roll suppression techniques which rely on frequency separation of ground roll from signal become ineffective for crustal studies. This paper presents the successful use of a new 2D wavelet method based on frame theory (physical wavelet frame denoising) in removing ground roll from a deep 3D reflection data set intended for the study of upper crustal Precambrian mafic sills in southwestern Alberta, Canada.

Structural geology data and 3-D subsurface models of the Budgell Harbour Stock and associated dykes, Newfoundland, Canada

The data presented in this article are primarily related to the Tectonophysics research article “Rift-related magmatism on magma-poor margins: Structural and potential field analyses of the Mesozoic Notre Dame Bay intrusions, Newfoundland, Canada and their link to North Atlantic Opening” Peace et al. (2018). The present data article contains structural geology data from lamprophyre dykes and surrounding country rock in proximity to the Mesozoic gabbroic Budgell Harbour Stock (BHS), Newfoundland, Canada, in addition to sub-surface density and susceptibility models of the main igneous body. The structural geology data include: dyke locations, orientations, thickness and marginal lineations, in addition to country rock bedding and kinematic data from nearby faults. The 3-D sub-surface density and susceptibility models were derived from the inversion of magnetic and full tensor gradiometry (FTG) data, respectively, using a probabilistic approach to inversion described in the Society of Exploration Geophysicists (SEG) 2018 Technical Program Expanded Abstract “3-D inversion of airborne gravity gradiometry data for the Budgell Harbour Stock: A case history of using a probabilistic approach” Geng et al. (2018).

Ground roll removal from a deep 3‐D reflection dataset using Physical Wavelet Frame Denoising

Deep crustal seismic reflection datasets contaminated with ground roll challenge processors to try and remove the high amplitude, low frequency dispersive waves while leaving low frequency deep reflections intact. Through the use of Physical Wavelet Frame Denoising (PWFD), a frame theory 2-D-wavelet-based method designed to extract hyperbolae from shot gathers, the ground roll is suppressed significantly from a deep 3-D reflection dataset collected in the Pincher Creek region of southwestern Alberta, Canada. This dataset, which represents the first attempt in Canada to image deep Precambrian reflectors using 3-D reflection techniques, contains significant ground roll which obscures key reflections. While conventional ground roll removal techniques are unable to remove the coherent noise without also altering the deep reflections, PWFD retains deep reflections and so facilitates velocity analyses and improves the stacked results. In this paper, we demonstrate the successful use of PWFD in the removal of ground roll from deep seismic reflection data.