THE ANNALS 



AND 



MAGAZINE OF NATURAL HISTORY. 



[THIRD SERIES.] 

 No. 75. MARCH 1864. 



XX. — On the Red Crag and its Relation to the Fluvio-marine 



Crag, and on the Drift of the Eastern Counties. By S. V. 



Wood, Jun. 



[With a Map, Plate XVIL] 

 Some observations made during a visit to the Red-Crag beds 

 disclosed such peculiar conditions of structure that I was induced 

 to enter upon a careful and minute survey of the whole Red-Crag 

 area. The result of that survey, with the observations that I 

 have been enabled to make upon the Drift-beds of the counties 

 of Essex and Suffolk, form the subject of this paper; and they 

 have led me to the conclusion that in the Red Crag (once re- 

 garded as of Miocene age) we have the initiatory stage, in Eng- 

 land at least, of that series of events which, chiefly studied under 

 the term drift, began by the encroachment upon the land of 

 England of a bay of the Northern Ocean, progressed by the ex- 

 tension of that bay into what now forms the Eastern Counties, 

 and eventually involved a far more extensive area in a submer- 

 gence beneath the sea that furnished the ice-borne sediment and 

 detritus known as the northern Clay-Drift. 



I have thought it more convenient to embody in an appendix 

 a list of the various sections of Red Cx'ag examined by me. 

 They are taken from every part of the Red-Crag area, and 

 comprise, with the exception only of Felixstowe, almost every 

 Red-Crag exposure between the Aide and the Orwell, as well as 

 several south of that river. 



It will be perceived, from the diverse shading upon the map 

 (Pl.XVII.)accompanyingthis paper*, that the Red Crag isdivided 



* This map, in so far as concerns the division between the fifth-stage 

 Crag and the beach stages, must be taken as a very imperfect approxima- 

 tion, the chief part of the Crag area being hidden under the great heaths 

 formed of the lower-Drift beds ; the object is to show the features presented 

 by the two Crags in their mode of deposit. The district on the east of the 

 Deben, between Woodbridge and Ramsholt, may be taken as a tolerable 

 approximation to exactness. 



Ann. S^ Mag. N. Hist. Ser. 3. Vol.xm. 13 



