A Bouma sequence is

Answer 1

The Bouma Sequence (after Arnold H. Bouma, 1962) describes a classic set of sedimentary beds (turbidites) deposited by a sediment-water turbidity current. The Bouma Sequence specifically describes the medium grained variety, which are usually found in the continental slope or rise setting. The Bouma Sequence is divided into 5 distinct beds labelled a through to e, with a being at the bottom and e being at the top and each bed is described by Bouma as having a specific lithology (see below). In a real Bouma Sequence, some beds may be missing - Bouma describes the ideal sequence. The beds are: * e: Muds, ungraded, often bioturbated. * d: Parallel laminated silts. * c: Cross laminated sands. * b: Parallel laminated sands. * a: Sands and any larger grains the turbidity current was carrying at the time of deposition.