THE UPPER CAENOZOIC SEQUENCES THE LONG ROW,
AROUND
COVEHITHE
H . B . MOTTRAM
T h e Norwich C r a g at Covehithe is regarded as extending down to about - 5 0 m O D which is well below the levels observable in cliff sections or excavations. T h e g r e a t e r part of it is t h e r e f o r e concealed and i n f o r m a t i o n is limited to that inferred f r o m a few wells and b o r e h o l e s in the a r e a . This i n f o r m a t i o n indicates that the concealed strata are mainly c o m p o s e d of sands which w e r e generally deposited u n d e r shallow o f f s h o r e conditions, though not necessarily as a Single s e q u e n c e . T h e exposed Norwich C r a g is largely c o m p o s e d of n e a r s h o r e sands which occur as two sequences. T h e lower s e q u e n c e indicates that in this area the d e v e l o p m e n t of tidal flats was d o m i n a n t , while t h e higher s e q u e n c e indicates that the d e v e l o p m e n t of beach faces was d o m i n a n t . T h e youngest sediments exposed in t h e cliff line reflect a c h a n g e f r o m m a r i n e to fluvial conditions and progressive onset of glacial conditions. It should be n o t e d that the cliffs have been e r o d e d at a fairly rapid rate and so t h e cliff line at the Long R o w in 1987, illustrated by Fig. 1, was about 430m f u r t h e r west than when observed by W h i t a k e r b e t w e e n 1877 and 1880 ( W h i t a k e r , 1887) and s o m e 50m f u r t h e r west than when m e a s u r e d by W e s t in 1974 ( W e s t , 1980). T h e bases of the cliffs along this Stretch of coast are exposed to best a d v a n t a g e during t h e winter and spring m o n t h s . A t E a s t o n B a v e n t s this has e n a b l e d t h e recording of sands which contain s o m e very shelly b e d s (Larw o o d & M a r t i n , 1953; Funneil & W e s t , 1962). D u e to coastal protection such e x p o s u r e s n o longer occur at this classical location but they can still b e f o u n d against E a s t o n W o o d . M a n y shells a r e w o r n , and although this is not sufficient evidence to prove accumulation u n d e r storm conditions it clearly shows t h e likelihood of significant reworking and mixing of shells f r o m different environments. A t C o v e h i t h e the present day f o r e s h o r e exposures are d o m i n a t e d by m u d s . G e n e r a l l y , t h e lowest visible m u d s have the richest clay c o n t e n t , the silt and fine sand c o n t e n t increasing towards the t o p of the f o r e s h o r e e x p o s u r e s . A Single black b a n d , smelling of anaerobic products, m a y also be n o t e d . Shells, largely a t t r i b u t e d to subtidal dwellers, sometimes occur in the m u d s but they are prevalent in occasional b a n d s of m e d i u m to coarse sand. M o r e c o m m o n l y f o u n d in the fine sediments are small cylindrical b u r r o w s , a b o u t 10mm long by 4 m m d i a m e t e r and of variable attitude. Initial examination suggested that the b u r r o w s w e r e f o r m e d by w o r m s or small crust a c e a n s , b u t on two occasions it was f o u n d that they can contain in-situ the bivalve mollusc Macoma calcarea. A s would be expected f r o m the size of the b u r r o w s , t h e in-situ individuals were smaller than 'loose' united or Single valved s p e c i m e n s normally f o u n d at these or other levels. T h e impact of the cold climate of this time (West etal., 1980) may have been responsible for an i m p o v e r i s h e d f a u n a and p o o r d e v e l o p m e n t of individuals in the shallowest e n v i r o n m e n t s . This should suggest that the b u r r o w e d m u d s were deposited
Trans. Suffolk
Nat. Soc. 25