Crustal Transect across the Lofoten Volcanic Passive Continental Margin, N. Norway, Obtained by Use of Ocean Bottom Seismographs, and Implications for Its Evolution
1995
This study presents a 500-km-long crustal transect across the Lofoten volcanic passive continental margin, N. Norway, by compiling the results of two successive Ocean Bottom Seismographic (OBS) experiments performed in 1988. The OBS profiles were acquired from the Norwegian mainland, across the continental shelf, over an area covered with landward flood basalts, to the Lofoten basin. The land side end of the crustal model represents a thinned continental structure. The crust in this part has strong structural complexity, mainly due to faulting during pre-Tertiary continental thinning phases. Between the continental shelf and the seaward dipping reflectors (SDR), the model represents an extremely thinned continental crust and ocean/continent transition zone. This region is interpreted to be dominated by an early Tertiary continental rifting phase that progressed until early Eocene. The observed lower crustal reflectors, which are interpreted as intrusions in the lower crust, as well as the landward flood basalts indicates an extensive magmatic activity during the continental rifting phase. Between the SDR and magnetic anomaly 21, an oceanic crust with thick lower crust and a high velocity layer at the bottom of the crust (7.3km/s) are obtained. This high velocity layer is believed to be created by anomalously hot asthenospheric material rising around a hot spot. The comparison of the crustal structure across the Lofoten margin with the structure of the Voring-More margin shows significant differences in the volume of the lower crustal high velocity layer, which can be interpreted in terms of a NE-ward decrease of the influence of the hot spot.
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