Geometry, distribution and fill of erosional scours in a heterolithic, distal lower shoreface sandstone reservoir analogue: Grassy Member, Blackhawk Formation, Book Cliffs, Utah, USA - Onyenanu, GI; Jacquemyn, CEMM; Graham, GH; Hampson, GJ; Fitch, PJR; Jackson, MD (Sedimentology, 2018)