II. 



The Geolog'y of Ipswich and its 

 Neighbourhood. 



IT is many years since the British Association met in the Eastern 

 Counties, and a good deal has recently been learnt about East 

 Anglian geology. In fact, since i858 many of the principal memoirs 

 have appeared, including the classical ones of Messrs. Wood and 

 Harmer (6), and of Professor Prestwich (2) ; the officers of the 

 Geological Survey also have since that date commenced and 

 completed an examination of the whole district (3, 4, 5). It may be 

 useful under these circumstances to devote a few pages to a sketch of 

 the geology of the region around Ipswich ; for the British Associa- 

 tion's excursions form an important part of the scientific work of the 

 geological section, and in this country there are few other oppor- 

 tunities for British and foreign geologists to meet and compare notes 

 in the field. 



The first thing that will strike a visitor traversing East Anglia is 

 that it is essentially a region of low plateaus, cut into by wide, shallow 

 river valleys. This flatness of the country and absence of any 

 dominant elevations may not be conspicuous from the rail, which 

 nearly everywhere keeps to the valleys, but, nevertheless, it is a 

 characteristic feature. The geology of these table-lands is usually 

 very monotonous, most of the interest being concentrated in the 

 valleys and cliffs, which cut through the glacial deposits to the 

 fossiliferous Tertiary beds below. Thus it will be found that 

 geologists describing this country tend to follow the valleys, though 

 the deposits described may be totally unconnected with the river- 

 systems. 



The most ancient rock visible at the surface within twenty miles 

 of Ipswich is no older than the Upper Chalk, but it maybe interesting 

 to mention that a boring at Harwich penetrated to the Palaeozoic 

 rocks, and further information on the Palaeozoic floor will probably be 

 communicated to the meeting. In the boring at Harwich the Chalk 

 was S90 ft. thick, then followed 61 ft. of Greensand and Gault, which 

 rested on a hard slaty rock, apparently of Carboniferous age. Thus 

 the Upper Cretaceous lies directly on Palaeozoic rocks, the whole 

 of the other Secondary strata being absent. 



