Evidence for thin oceanic crust on the extinct Aegir Ridge, Norwegian Basin, NE Atlantic derived from satellite gravity inversion

Abstract

Satellite gravity inversion incorporating a lithosphere thermal gravity correction has been used to map crustal thickness and lithosphere thinning factor for the NE Atlantic. Predicted oceanic crustal thicknesses in the Norwegian Basin are between 4 and 7 km on the extinct Aegir Ridge, increasing to 9 – 14 km at the margins, consistent with volcanic margin continental breakup at the end of the Paleocene. The observation (from gravity inversion and seismic refraction studies) of thin oceanic crust produced by the Aegir Ridge in the Oligocene may have implications for the temporal evolution of asthenosphere temperature under the NE Atlantic during the Tertiary. Thin Oligocene oceanic crust may imply cool (normal) asthenosphere temperatures during the Oligocene in contrast to elevated asthenosphere temperatures in the Paleocene and Miocene‐Recent as indicated by the formation of volcanic margins and Iceland respectively.

Potential mechanisms for the genesis of Cenozoic domal structures on the NE Atlantic margin: pros, cons and some new ideas

“…We have examined the driving force generating these northern orogenies, because it appears that they occurred in the absence of traditional 'passive' plate-driving mechanisms such as slab pull, suggesting in turn generation of compression by an 'active' drive from the spreading (Breivik et al 2006). Simplified after Greenhalgh & Kusznir 2007. ridges. We have not yet, however, settled on a convincing explanation for this apparent anomaly.…”

The Norway Basin revisited: From continental breakup to spreading ridge extinction

“…1). Based on newly acquired geophysical data (seismic refraction, shiptrack magnetic anomalies and satellite-derived gravity) several authors addressed new questions about the timing, variability, seismic expression and origin of atypical magmatic events affecting the NB and contiguous COT (Breivik et al, 2006;Greenhalgh and Kusznir, 2007;Mjelde et al, 2009;White et al, 2008).…”

Continental crust beneath southeast Iceland

“…The current plume axis (25), plume flow pattern, and inferred Moho (Fig. 2B readily detected by examining outcrops (e.g., Seychelles) or from geophysical data, e.g., JMM (26)(27)(28)(29)31) and the Laxmi Ridge (41) in the northeast Indian Ocean, or from analyses of mantle xenoliths (42). Others, such as the postulated Mauritia Microcontinent (43), may be obscured by thick successions of younger volcanic material.…”