The provenance and diagenesis of Palaeogene sandstones of southeast England as indicated by heavy mineral analysis

Abstract

Two distinct heavy mineral assemblages occur in the Palaeogene sands, one derived from the Scottish Highlands, characterising the Thanet Formation, the upper part of the Woolwich and Reading Fm., the Oldhaven Fm., the London Clay Fm., the Claygate Beds and the Bagshot Beds, the other being largely confined to the bottom bed of the Woolwich and Reading Fm., and being derived from the south, either the Armorican or Ardennes-Rhenish massifs. In addition, heavy minerals indicative of contemporary volcanism occur, both in the basal London Clay, and more abundantly, in the Thanet Fm., where euhedral grains of aegirine, arfvedsonite and apatite have been recorded. Post-depositional alteration is particularly marked in the Thanet Fm., where epidote, garnet, apatite, sphene and hornblende are progressively lost towards the top of the sequence as a response to acidic groundwater circulation associated with pre-Woolwich and Reading Fm. weathering.