Diatom analysis of a core from La Grande Mare, Guernsey

Diatom analysis was carried out on a sediment sequence from La Grande Mare, Guernsey ( 49° 27' 58" N 2° 36'20"W). The technique was used to determine the conditions under which the sediments accumulated and, in particular, the salinity regime of the water. A diatom assemblage examined in an earlier study of a Phragmites peat sampled at La Grande Mare had a brackish water flora (Churchill 1964). This was believed to indicate a rise in sea level and the contact of the peat with overlying grey silty clay, at +6 ft OD, was dated to 3180± 110 BP. In the present study the suggestion that the sediments contain evidence for a marine transgression is examined