Sedimentation in a closed trough north of the Iberia Abyssal Plain in the northeast Atlantic†

Abstract

Mirrol Trough of the northeast Atlantic contains five NNE‐SSW trending, en echelon, turbidite‐filled basins deeper than 5500 m, each ranging from 4 to 10 km in width and 19 to 65 km in length. Trough deposition has consisted mainly of turbidites from adjacent hills and ridges as indicated by the physiography of the region, sediment isopach map, the nature of the sediments in the trough, and benthic foraminiferal depth indicator species. The sedimentation rate on abyssal hills and ridges, as deduced from palaeomagnetic evidence, is 1.36 cm/103 years. Using this sedimentation rate, it is estimated that Mirrol Trough subsided relative to the surrounding area and began receiving sediments between 8.3 and 11.5 m.y. ago; and the deposition of the most recent turbidite has occurred sometime between 29,000 and 44,000 years b.p. Tilting of the base of the most recent turbidite with respect to the basin floor is observed, and this is attributed to relative sinking of the eastern margin of the trough after the deposition of the most recent turbidite.

The structure and origin of the Azores--Biscay Rise, North-east Atlantic Ocean

“…2). The tilted sediments, about 11.5 Myr old, reported by Addy & Kagami (1979) in Mirrol Trough therefore appear to be an isolated occurrence. Relatively simple gravity models can be used to fit the observations without introducing subduction (Fig.…”

“…Mirrol Trough, which lies at the foot of the south-east flank of the Rise between 43'30" and 44'30" (Fig. 4a), has been described by Addy & Kagami (1979). It consists of five en-echelon sediment-filled basins up to 5700 m deep striking NE to NNE and containing up to 600m of sediment, excepting one small area with over 900m.…”