On Geology Around Ingham

Page 1

NOTES ON THE GEOLOGY OF THE COUNTRY AROUND INGHAM, NEAR BURY ST. EDMUNDS b y B. M .

FUNNELL.

T h i s account is primarily intended for the use of local naturalists and schools. T h e area is one of considerable complexity and uncertainty even for glacial deposits. Individual formations are both variable in character and patchy in distribution. Consequently some errors were made when the area was originally surveyed by H M Geological Survey. With this in mind, these notes have been prepared to illustrate particular present-day exposures rather than to give general accounts of the nature of each formation. Following this factual portion of the paper is a discussion ot the geological history and its relation to a current Pleistocene chronology.* T h e TOPOGRAPHY of the area is subdued, and the total ränge of relief is little more than 100 feet. T h e r e are two easily appreciated features to which attention may be drawn. lhe first is the high-level plateau of Boulder Clay which stands at about 170 175 feet O D. T h i s may be clearly seen on the road irom Elveden to Culford, where it crosses Weatherhill Heath The second is the main terrace in the Valley Gravel, which declines f r o m about 90 feet O . D . to 60 feet O.D., alongside the nver Lark (within the limits of our area). T h i s terrace is; well seen between Fornham All Saints and Hengrave, between West Stow and Icklingham, and at Cavenham Heath. T h e r e are other lesswell-marked features in the Valley Gravel, and the modern alluvium forms a lowest level abutting against older deposits, almost ubiquitously with a small step. A subsidiary point of interest (see Watt, 1955) is an exposure of stone stripes (evidence of one-time periglacial conditions), on the surface of the chalk at T h e t f o r d Heath, beside the road on the north side (N.G. 850795). (All grid references in this account refer to O.S., 1 : 63360, Sheet 136.) * T h e c u r r e n t c h r o n o l o g y a d o p t e d h e r e is t h a t b a s e d o n t h e s u c c e s s i o n o u t l i n e d b y B a d e n - P o w e l l (1948). T h e c o r r e l a t . o n vvith h e N o r t h E u r o p e a n c h r o n o l o g y s e t o u t b e l o w !S b a s e d o n W e s t (1954). The g e n e r a l l y a c c e p t e d A l p i n e e q u i v a l e n t s a r e p l a c e d in b r a c k e t s . Gipping Till H o x n e interglacial Lowestoft Till Corton Beds

^ , . , T = Great Interglacial Elster-Saale (Mindel-Riss)

baale

(K1SS

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p r o b a b l y

Elster

<Mindel)


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