Lateglacial to Holocene palaeoenvironmental change in the Muck Deep, offshore western Scotland

Shelf basins ('glacial incisions') can preserve a detailed record of palaeoclimatic changes due to their low-energy environment. The 'Muck Deep', a complex of glacially-overdeepened troughs on the Inner Hebrides shelf constitutes an example of such an environment. Five sediment cores from the Muck Deep have been analysed and related to geomorphological evidence and sub-surface seismic facies. The cores show an integrated sequence of sedimentary and faunal variations from the retreat of ice (c. 17 ka) to the present day. Glacimarine sandy muds with ice rafted debris are dated to about 11.9 cal ka BP, supporting glacial occupancy in western Scotland until the latest stages of GS-1. The transition from a paraglacial to a more stable landscape is indicated by an erosional boundary in one of the cores dated between 11.3 and 11.6 cal ka BP. Sandy sediments in a core from 200 m water depth show two upward-fining cycles and a mid-core erosional unconformity, interpreted as bottom-current deposits. Such structures do not occur in the western Muck Deep, indicating different bottom current velocities through time. A regional signal of increasing current energy at the end of the Holocene marine transgression is interpreted as the onset of modern oceanographic conditions.