CLAY MINERAL D ISTR IBUT ION AND PROVENANCE IN MESOZOIC AND TERT IARY MUDROCKS OF THE

northern North Sea have been determined in <0.2 ~m fractions of cuttings amples. The clay assemblages of more deeply-buried samples cannot be unambiguously related to sedimentary input because of the diagenetic overprint which may account for much c)f the chlorite and related interstratified minerals. Other sediments, discussed on a regional basis and related to the geological history of the basins, are interpreted in terms of clay mineral provenance and control by climate, tectonic and volcanic activity. The distribution of illite-smectite can often be related to volcanic activity both in the Forties area during tbe M. Jurassic, and on the NE Atlantic ontinental margin during the U. Cretaceous-Early Tertiary which affected the North Sea more widely and left a prominent record in the Viking Graben and East Shetland Basin. Kaolinite associated with lignite-bearing sediments in the Outer Moray Firth Basin was probably derived by alteration ofvolcanic material in lagoonal or deltaic environments. Some U. Jurassic and L. Cretaceous sediments of the Inner Moray Basin are rich in illite-smectite, he origin of which is not clear. Petroleum exploration in the North Sea has provided access in the offshore basins to sedimentary ocks ranging in age from Carboniferous to Recent. Although the geology and structural development of the North Sea are now well established (Glennie, 1986b) an