Peacock : The Fenland Soils. 



*79 



within its boundary called Grunty Fen. The Fenland deposits 

 lie on this Boulder Clay floor, which has undoubtedly been*much 

 denuded by marine wave action in a shallow sea, after the 

 retiring - of the g"reat ice-sheet. 



The Beds, or partial accumulations, lying on the Boulder 

 Clay, from the lowest upwards, are as follows : — 



1. — Old Gravels of Palaeolithic Ag-e. 



2. — Fen Beach and Floor Gravels. 



3. — Forest Period. 



4. — Peat. 



5. — Shell Marl. 



6. — Silt. 



7. — Upper or Modern Peat. 



You must understand this record is only roughly approximate. 

 During Pleistocene times, since man's advent in Great Britain, 

 there seem to have been many changes of level in restricted 

 areas, with mingled forest, peat, and silt formation. 



Two periods can be clearly distinguished in the deposits 

 immediately above the Boulder Clay. The Palaeolithic Period 

 was a time of prevalent on-shore winds, and the deposit is truly 

 estuarine, and has a marine and shore facies. This period is 

 almost equally rich in specimens from land and marine sources 

 of supply. The lists of shells are too long to give here, but 

 may be found in full in the Survey Memoir. The Fen Beach and 

 Floor Gravels and Sand show a different state of circumstances, 

 a shallowing sea, which was not silt- and warp-producing, and 

 an off-shore wind. These gravels are wholly unfossiliferous. 

 They look like the production of rough wave action on a very 

 flat shore, or shallow sea. 



As this period passed, the sea seems to have retired as the 

 land gradually rose. Trees began to grow and a Forest Period 

 was soon developed. But trees have an allotted span, and 

 frequently die from accident — storm, lightning, and insect 

 ravages. The trees of the forest fell, and stopped the natural 

 surface drainage, and peat was formed, and the destruction of 

 wide areas of woodland followed. Our forelder, Mesolithic 

 man, may have given some aid in helping forward this work of 

 destruction, but there is not a particle of evidence that he did, 

 I believe. Again a slight downward movement of the land 

 commenced. Salt water came in contact with the peat flora and 

 killed it. Estuarine conditions again prevailed, and modern silt 

 and warp were deposited as fast as the Fenland rivers supplied 

 it. Still later in time, where the silt dipped into deep hollows 

 from the unequal shrinkage of the lower peat — which was some- 



1902 June 1. 



