Publication Date:
2019
Description:
Abstract
Our 2‐D layered velocity model along‐strike northeastern Nova Scotian margin, constrained by wide‐angle seismic Profile OCTOPUS and coincident 9‐km streamer Profile GXT‐5100, displays highly variable basement structures interpreted to define four distinct zones within the continent‐ocean transition (COT). Zone I, with thin (1–2 km) and laterally uniform upper crust (5.2–5.5 km/s) and high velocity lower crust (6.5–7.7 km/s). Zone II, with velocities of 5.5–7.5 km/s and a high vertical velocity gradient (∼1.1 /s) characteristic of exhumed serpentinized (up to 90%) mantle (ESM) above ∼3.5 km thick slightly (〈30%) serpentinized mantle layer of reduced mantle velocities (7.5–8.0 km/s). Zone III, with 1–2 km thick upper crust and velocity of ∼5.2 km/s above a ∼6 km thick, moderately (〈60%) serpentinized mantle layer (velocity ∼6.4–7.9 km/s). Zone IV, with lower crust (∼0.7–3.0 km thick and with velocity of 6.1–6.6 km/s) between upper crust (velocity ∼5.0–5.4 km/s) and a slightly serpentinized mantle layer (〈40%; velocity ∼7.3–8.0 km/s). These COT structures represent embryonic oceanic or rifted continental crust, and ESM. By combining our results with those from two dip‐oriented crossing profiles, we map a regional track of non‐ESM landward of the OCTOPUS profile with mostly uniform along‐dip width, but a limited extent and variable width section of ESM seaward. Our results indicate that there can be a remarkable amount of short‐wavelength (e.g., 50 km) lateral structural variability within individual rifted margin segments, but that mapping it requires a grid of modern wide‐angle profiles.
Print ISSN:
2169-9313
Electronic ISSN:
2169-9356
Topics:
Geosciences
,
Physics
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