14>> MIDDLE ALBIAN STRATIGRAPHY 



The main factor governing sedimentation appears to have been the pattern of 

 parallel ridges and troughs produced initially in late tardefurcata Zone times by a 

 comparatively mild folding phase. Casey from the field evidence afforded by largely 

 remanie mammillatum Zone deposits interpreted these troughs as ' dimples ' (1961a), 

 but the Middle Albian sediments have provided far more definite information on the 

 trend of these structures (text-fig. 52). 



Although the ridges were not obviously active structures the sediments thin across 

 them due to water-current activity, and probably to some gravitational movement 

 of clay particles down-slope. During minor periods of current erosion the degree of 

 condensation is greater in the area of the ridges as one would expect. 



(a) The Margins of the depositional basin 

 in England and Northern France (text-fig. 51) 



To what extent the Brabant massif and the London Platform acted as positive 

 areas in Middle Albian times is far from certain. Nothing is yet known of the Gault 

 sequence in the area of the North Sea adjacent to the shores of Kent, Essex, Suffolk 

 and Norfolk. There certainly is no evidence made available at this time of the land 

 area suggested in this region by Jukes-Browne's frontispiece map (1900). It is also 

 apparent from the borings in the Cliff e area of Kent (Owen in press), that renewed 

 movements along late Jurassic or early Cretaceous faults in the area of what is now 

 the Thames estuary, caused strong current action which removed Middle Albian 

 sediments over the southern part of Essex. This disturbance contributed to, and 

 was associated with other movements which planed-off the upper surface of the Lower 

 Gault throughout the Anglo-Paris Basin. How much sediment and the areal extent 

 that has been removed is at present unknown, but in Kent, and in Cambridgeshire 

 and Norfolk, where Middle Albian sediments are preserved, there is no evidence in 

 the sequence of an area of Palaeozoic rocks actively undergoing erosion to the east. 



A shoal area existed in north-west Norfolk and in the area of the Lincolnshire and 

 Yorkshire Wolds and to an unknown extent in the adjacent area of the North Sea. 

 Its position is indicated by the pebbly development of Bed C of the Hunstanton Red 

 Rock (Wiltshire 1869 ; 185-188) of Middle Albian age, and its lateral equivalents 

 in the Red Chalk with its shallow-water fauna. To the south and east in Norfolk, 

 Bed C is replaced by clays of the contiguous Lower Gault. This shoal area probably 

 flanked the Palaeozoic massif of the Pennines and its southerly extension of the Peak 

 District and a possible positive area in the adjacent North Sea (Collette 1968 ; 20). 

 Gault clay probably existed south of the Pennine massif because derived Albian 

 fossils are known from the glacial boulder clay as far north as Chellaston, Derbyshire, 

 as well as elsewhere in the Midlands. 



On the balance of evidence the writer is inclined to doubt that the Middle Albian 

 sea extended into the Cheshire lowlands but this could prove to be incorrect. The 

 clays of the lyelli and spathi Subzones at Swindon (Badbury Wick) and at Devizes are 

 very silty. Those of the intermedins Subzone at Devizes and Didcot are even coarser 

 in grade. These examples do not necessarily indicate the proximity of a marginal 

 area but equally they do not suggest an extensive basin area to the north west. 



