Cretaceous and lower Tertiary of Seine-Maritime, France: a guide to key localities

Abstract

Representative sections in the Cretaceous and lower Tertiary sediments of Seine-Maritime, northern France, are described and a comparison made with the English south coast outcrops. In the Bec de Caux Aptian to lower Albian sandy and pebbly deposits, somewhat comparable to the Isle of Wight succession, rest non-sequentially upon Kimeridge Clay. The middle Albian marginal pebbly loams and local phosphatic nodule beds represent a less complete sequence than the Gault Clay of the Isle of Wight. The Gault farther east at Bully, Pays de Bray, shows lower Albian Douvilleiceras mammillatum Zone and basal middle Albian in clay facies. The upper Albian is represented within the Gault and Gaize of the Bec de Caux, corresponding with the highest Gault Clay and Upper Greensand of the Isle of Wight. Unlike the Cenomanian Lower Chalk of the Isle of Wight, the Craie Glauconieuse and Craie de Rouen contain conspicuous flint courses, reminiscent of higher horizons in south-west England. Palaeogene sediments rest unconformably on a locally irregular surface of mainly Santonian-Campanian Chalk. Surviving outcrops occur as scattered outliers standing above the level of the Chalk downland and as extensive sheets preserved in synclinal downwarps, especially north and east of Yvetot. Inland exposures are few but the large Varengeville outlier, west of Dieppe, shows fine cliff-sections. A marine transgressive sequence of early Sparnacian (lower Eocene) age, comparable to the Woolwich Bottom Bed of south-east England, passes up into regressive brackish and partly non-marine beds similar to the Woolwich Shell Beds of the Newhaven outlier but with greater lateral variation. Higher deposits, collectively termed Formation de Varengeville, include thick late Sparnacian marine sands strikingly akin to the Oldhaven Beds of Kent and a sandy Ypresian clay similar to the London Clay facies of Bognor Regis. Younger Tertiary beds are represented by small local outliers of marine sands and clays of (?) Helvetian date in the south and west of the Bec de Caux.