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Large scale sedimentary structures present in the Upper Turonian to Santonian chalks of Haute Normandie (northern France) represent the remains of a carbonate bank complex which formerly extended over an area of at least 1500 km2. Cliff exposures along the Channel coast from St Valéry‐en‐Caux to Cauville and along the Seine from Sandouville to Lillebonne show sections of banks up to 50 m high and 1500 m across, their internal structures picked out by hardgrounds, nodular chalks and horizons of burrow flint. Associated with banks are slump sheets up to 20 m thick, slump scars, sedimentary breccias, injection phenomena and faults contemporaneous with sedimentation. Later diagenetic features include extensive dolomitization and silicification. These structures compare closely with the Waulsortian banks of the Palaeozoic, and bryozoan bioherms known from the Upper Cretaceous and Palaeocene of Denmark. Frame‐building, sediment trapping and stabilizing organisms are absent, and bank development and stabilization was probably due to a plant covering, either algal or of marine angiosperms. Banks generated much of their own sediment, whilst a pelagic constituent (calcareous nannofossils and Foraminiferida) is also present. The distribution of the bank complex is related to a basement controlled swell area, whilst the life of the complex was limited to a relatively shallow water, regressive episode in the predominantly transgressive Upper Cretaceous history of the region. Les falaises littorales du Pays de Caux comprises entre Antifer et St Valèry‐enCaux, et les affleurements de la basse vallée de la Seine permettent d'observer des formations du Turonien supérieur‐Sénonien inférieur qui présentent des stratifications irrégulières soulignées par de nombreux hardgrounds, des horizons de craie noduleuse et des cordons de silex. Ces structures sont identifiées à des accumulations de calcilutite et calcarénite sous forme de bancs sous‐marins dont la hauteur peut atteindre 50 m et qui couvrent une surface supérieure à 1500 km2; ils apparaissent au‐dessus de hardgrounds subhorizontaux qui indiquent un haut‐fond régional stable. Des glissements sous‐marins sont associés à ces bancs et engendrent des niveaux avec des déformations souples atteignant 20 m d'épaisseur. Des brèches apparaissent localement et contiennent des blocs basculés de hardgrounds fragmentés lors du glissement; on y observe aussi de petites failles intrasédimentaires et des phénomènes d'injection. Aucun organisme constructeur ou capable de piéger et retenir le sédiment n'a été observé. La stabilisation de ces bancs serait due à une couverture végétale (algues ou angiospermes marines) dont on sait qu'elle peut disparâitre sans laisser de trace lors de la fossilisation. La croissance de ces bancs serait réalisée par un apport de sédiment comprenant une part de nourrissage autochtone comme cela existe pour les bancs récents en eau peu profonde, associée au dépôt d'une fraction pélagique.

This paper documents normal fault sets observed in chalks exposed in widely separated localities in the UK and France. These faults are characterized by having a wide range of strikes at any one locality, are developed entirely within the chalk succession and do not seem to interconnect to deeper or shallower structures. These structures may result from two different mechanisms: (1) complex polyphase deformational histories involving contrasting stress states; or (2) a single deformational phase in which the faults develop to accommodate compactional strains. Evidence is presented from microstructural and petrographic data to support the latter interpretation. In particular, the association of calcite and marcasite mineralizations with fracture surfaces and fault zones and textural observations relating flint occurrence to early fault formation point towards fault propagation at a very early stage of burial and compaction of the chalky sediments. An analogy is drawn between these outcrop-scale structures and polygonal fault systems at a larger scale recognised from seismic observations of chalk sequences deposited at passive continental margins. The origin of these structures may be related to syneresis at an early stage of deformation followed by pressure solution phenomena that may reactivate this early-inherited polygonal fault pattern until the present day.

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