|
Non-marine, intertidal and inshore-marine deposits have been recognized in 43 gravity cores collected from the sea-bed off south-east Devon; at least eight of these cores end in bedrock (New Red Sandstone). Foraminiferal assemblages were used as criteria to distinguish several depositional environments. Pollen analyses of intertidal muds, which were apparently deposited along the margins of a now-submerged extension of the Exe river channel, have dated the Flandrian transgression in the region between —140 ft and —55 ft O.D. (zones IV-V to VIc). The rate of sea-level rise was about 5 ft/century during zone VI. An extensive deposit of muddy sand covers the intertidal deposits and the old land surface, and was probably laid down in the sublittoral zone, seawards of the transgressive Flandrian shoreline. Authigenic pyrite and glauconite are found in several sedimentary types; their distribution in the muddy sand indicates that the glauconite is syngenetic, while the pyrite has formed during the early stages of diagenesis.
