[2][1] The Stac Fada Member is exposed at a series of localities on or near the coast of Wester Ross, extending for about 50 km (30 mi) from the western side of Loch Ewe in the south to the Stoer peninsula in the north.

Later interpretations invoked a volcanic origin for the unit, based on the presence of pieces of green devitrified glass, with pyroclastic flow, peperite, tuff and lahar all being proposed.

When shocked quartz, a higher-than-expected concentration of platinum-group metals and the presence of a non-terrestrial chromium isotope were all identified in the unit, it was reinterpreted as part of an impact ejecta blanket.

[7] The crater, preserved under sedimentary layers of sandstone, is currently presumed to either lie to the west under the Minch, the waterway that separates the Isle of Lewis in the Outer Hebrides from the north-west Highlands of Scotland, or to be the cause of the Lairg Gravity Low, beneath the Moine Thrust Belt to the east.

The orientation of small-scale thrust faults and folds and striae found locally at the base of the unit have been combined with measurements of the fabric in the rocks using anisotropy of magnetic susceptibility.