OPTICAL DATING OF AEOLIAN SEDIMENTS FROM THE SEFTON COAST, NORTHWEST ENGLAND

Coastal dunes of Holocene age fringe the coast between Southport and L iverpool in northwest England, forming a natural barrier which prevent s marine flooding of low-lying agricultural land in West Lancashire an d north Merseyside. Although organic deposits associated with the back -barrier sediments have been dated by radiocarbon methods, the aeolian sands have not previously been dated directly. This paper presents th e results of a pilot investigation carried our to assess the potential of optical dating of quartz in providing a chronostratigraphic framew ork for the coastal aeolian sand deposits. The initial results obtaine d from three sites are consistent with independent stratigraphic and r adiocarbon dating evidence, and indicate that the method has potential , even where the sands have been affected by postdepositional weatheri ng and leaching. Age estimates obtained using a total dose normalizati on method were found to give less scatter than estimates obtained usin g the natural normalization method. The optical dating results support radiocarbon evidence for a dune-forming episode at Formby Point aroun d 3000 years ago, and are consistent with historical evidence that tra nsgressive sand sheets invaded the western margin of Downholland Moss during the Middle Ages. Results from a third site, inland of Hightown, suggest that aeolian deposits previously mapped as part of the Shirdl ey Hill Sand were formed during the early to mid-Flandrian. These aeol ian sediments, which were partially buried by estuarine silts during t he later Flandrian transgression, may have been derived from marine or estuarine