* Astronomy

Title: Giant irregular pockmark craters in the Palaeogene of the Outer Moray Firth Basin, UK North Sea
Authors: D. Colea, S. A. Stewartb and J. A. Cartwright

A cluster of irregular pockmark craters of Palaeogene age in block 15/18 in the Outer Moray Firth, UK North Sea have been mapped on 3D seismic data with well control. The craters range from 0.5 to 4 km in diameter, between 50 and 200 m in depth, and have been buried by Tertiary subsidence and sedimentation to present-day depths of between 1000 and 1400 m sub-sea. They are circular to elliptical in plan view, and are located in a delta front and upper pro-deltaic slope position on the Dornoch delta. The structures are confined to the top of the Lower Eocene Balder Formation, and regional mapping across the Moray Firth Basin shows they are restricted to an area of ca. 15 × 15 km². Well data show that the craters are sand-filled, and have excavated an argillaceous and tuffaceous unit. The crater-filling sands are sealed by overlying mudstone units. Planar wing-like features emanate from the margins of the craters. Well control indicates that these seismically identified 'wings' consist of sandstone, suggesting that the craters have been modified by an episode of sand remobilisation and injection. The proposed mechanism for the formation of these structures is large-scale fluid eruption (probably shallow gas) at the Early Eocene seafloor.

Read more