A HISTORY OF KENT 



the northern slope of the dome is the cause of the general northward dip 

 of its strata. Let us now consider the composition and origin of these 

 strata. 



HASTINGS BEDS 



The deep borings have proved that for a long period preceding the 

 deposition of the oldest rocks exposed at the surface within the Wealden 

 area, this district was submerged beneath the sea and gradually covered 

 by a great thickness of marine sediments of Jurassic age. But this ancient 

 sea was at length displaced, either by an elevation of the land or by the 

 infilling of its basin, or by a combination of both causes, and the area 

 began to receive the detritus brought down by a large river into a lake 

 or estuary. The freshwater or estuarine deposits of this period constitute 

 the oldest strata visible at the surface in Kent. They occur only in a 

 limited tract in the south-western part of the county, but have a much 

 more extended outcrop south of the county boundary, in Sussex. They 

 consist of a somewhat variable group of sands, soft sandstones, silts and 

 clays, known collectively as the Hastings Beds, which form the lower 

 part of the great freshwater Wealden Series. These beds underlie the 

 pleasant hilly ground to the southward of the flat along which the rail- 

 way is carried in a nearly straight line from Edenbridge to Ashford ; and 

 although their area in Kent is so limited, nearly the whole of the group 

 is represented, owing to the relatively sharp uplift and to the presence of 

 ' faults ' or dislocations in this quarter, whereby blocks of strata are shifted 

 to higher levels than they would otherwise occupy. 



Ashdown Sand. — The lowest subdivision is the Ashdown Sand, 

 consisting mainly of fine quartzose sand and soft sandstone, with occa- 

 sional layers of loam and clay and of small well-rounded pebbles. It 

 is well exposed in quarries and road cuttings on the hill immediately 

 south of Tonbridge, being here uplifted by a ' reversed fault ' which is 

 visible in the principal quarry. Fossils are rare in this deposit, obscure 

 fragments of plants, washed down from the ancient land, being usually 

 its only relics. 



Wadhurst Clay. — Separating the underlying Ashdown Sand from 

 the overlying Tunbridge Wells Sand is the Wadhurst Clay, the most 

 fossiliferous subdivision of the Hastings Beds, and also formerly of con- 

 siderable economic importance as the chief source of the ironstone which 

 was mined and smelted in the Weald. It consists of alternations of clay, 

 shale and sand-rock, with thin impersistent bands and lenticular nodules 

 of shelly limestone, calcareous sandstone or grit, and clay-ironstone. Its 

 chief outcrops in Kent occur as narrow irregular strips along the valleys 

 of the Medway, Teise, Rother and their tributaries. Its fossils include 

 numerous freshwater shells of the genera Paludina, Cyrena and Uriio, with 

 the minute oval valves of Cypris, a small crustacean, in vast abundance ; 

 and the teeth and bones of extinct fish and reptiles ; and the remains of 

 plants. The best collections of these fossils have however been obtained 

 from Sussex, where the gritty layers are sometimes extraordinarily rich 



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