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the
Ashdown Beds and also to the effects of wave action at the base of the cliffs. At high tide, waves cut into the lowermost, argillaceous part of the cliffs and undercut the overlying sandstones and siltstones resulting in toppling and rock falls. Where sandstones are interbedded with silts and clays, this may result in single and multiple rotational type landslides as well as block slides and mud flows. In theory, the remains of previous landslips should then protect the toe of the cliff from further weathering. However, these blocks and sediments are transported East with shingle and other beach deposits by long-shore drift, leaving the cliffs vulnerable to wave action and susceptible to further landslides.
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The
Hastings to Pett Level section of the coast has suffered a number of significant recent and historic landslips, dating back to the 18th century. These can be seen in and around Covehurst Wood and the Fairlight, Ecclesbourne and Warren Glens. This has been attributed to lithological variations of
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The
Ashdown Formation typically comprises sandstones, siltstones and mudstones. In the east of the county, the formation tends to be more argillaceous in its lowermost part and fines up to a sandier division in the uppermost 30 to 50m. The clays are identified by their characteristic purple and
384:. The top of the Ashdown Formation is marked as the top of a massive sandstone bed known as the Top Ashdown Sandstone. This is overlain by an easily identified very coarse grained sandstone known as the Top Ashdown Pebble Bed, which is considered to be part of the overlying
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brick-red mottled nature. In early references, these variations give rise to the division of the formation into the ‘Fairlight Clays’ and the ‘Ashdown Sands’. However, it is now considered as one due to the impersistence of the clays across the
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strata throughout the region. It comprises a fine to medium grained sandstone ranging in thickness from 1.2m to 8m. Other marker beds can be found throughout the formation including the Cliff End
Sandstone and the Lee Ness Sandstone.
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to the west and Cliff End to the east. The mottled heavily degraded silty clays of the former ‘Fairlight Clays’ can be easily distinguished against the well bedded sandstones and interbedded siltstones of the ‘Ashdown Sands’.
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At this location the formation can be followed from the axis of the
Wealden Anticline at Lee Ness Ledge through the well distinguished marker beds and horizons to its juncture with the
591:
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Ruffell, A., Ross, A. & Taylor (1996) Early
Cretaceous Environments of the Weald. Geologists’s Association Guide No. 55, Geologists’s Association, London.
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Allen, P. (1948) Wealden
Petrology: The Top Ashdown Pebble Bed and the Top Ashdown Sandstone. Quarterly Journal of the Geological Society, 104, 257-321.
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The Lee Ness Ledge is known for the prominent Lee Ness
Sandstone and its many well preserved fossilised dinosaur footprints, particularly
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365:. Despite this the variations of clays and sands in the formation are usually marked separately on the maps and records of the
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Period, which lasted for approximately 40 million years from 140 to 100 million years ago. The
Ashdown Formation is of Late
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Robinson, D.A. & Williams, R.B.G. (1984) Classic
Landforms of the Weald. The Geographical Association, Sheffield.
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Geology of the country around Hastings and Dungeness: Memoir for 1:50,000 geological sheets 320 and 321
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Analysis of the distribution and characteristics of landslips in the Weald of East Sussex
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and the Ashdown Formation is taken at the top of the Greys Limestones Member of the
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369:. In its entirety the formation is usually found to be between 180 and 215m thick
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The Ashdown Beds are best exposed in the 8 km cliff section between
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Level are difficult to get to safely because of the tidal range of the
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531:. Research Report RR/08/03. British Geological Survey, Keyworth.
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A stratigraphical framework for the Lower Cretaceous of England
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because of its geological importance. The cliffs between
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and the lowermost and oldest part of the now unofficial
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Hopson, P.M., Wilkinson, I.P. and Woods, M.A. (2010)
424:Level. Part of this section has been designated a
281:. These geological units make up the core of the
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340:to age. The formation takes its name from the
273:is a geological unit, which forms part of the
619:"Jamies monster find sheds light on history"
552:Lake, R.D. & Shepard-Thorn, E.R. (1987)
121:An exposure of the Ashdown Formation on the
581:. MSc dissertation, University of Brighton.
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296:The other component formations of the
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617:Fitch, Rachel (26 September 2006).
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426:Site of Special Scientific Interest
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676:Lower Cretaceous Series of Europe
656:British Geological Survey lexicon
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594:. Natural England. Archived from
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182:typically in the range 200-230 m
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504:Tunbridge Wells Sand Formation
306:Tunbridge Wells Sand Formation
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671:Lithostratigraphy of England
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285:in the English counties of
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312:in turn forms part of the
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409:dinosaur footprint near
316:which underlies much of
509:Wadhurst Clay Formation
386:Wadhurst Clay Formation
320:. The sediments of the
302:Wadhurst Clay Formation
163:Wadhurst Clay Formation
494:Geology of East Sussex
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397:Hastings to Cliff End
135:Geological formation
592:"Pett Level (SSSI)"
475:A landslide on the
467:Engineering geology
27:Stratigraphic range
598:on 3 November 2012
577:Codd, J.W. (2007)
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479:coast at Fairlight
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318:South East England
314:Wealden Supergroup
300:are the overlying
173:Durlston Formation
681:Valanginian Stage
271:Ashdown Formation
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21:Ashdown Formation
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686:Berriasian Stage
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253:Type section
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477:East Sussex
428:, cited by
338:Valanginian
326:East Sussex
287:East Sussex
247:Weald Basin
123:East Sussex
38:Valanginian
665:Categories
515:References
346:High Weald
334:Berriasian
34:Berriasian
623:The Argus
461:Iguanodon
407:Iguanodon
356:Lithology
336:to Early
258:Named for
200:Sandstone
196:Siltstone
187:Lithology
179:Thickness
159:Underlies
151:Sub-units
488:See also
434:Hastings
418:Hastings
411:Hastings
304:and the
220:Location
210:Mudstone
169:Overlies
628:2 March
602:2 March
344:in the
225:Country
192:Primary
141:Unit of
105:↓
350:Sussex
308:. The
243:Extent
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125:coast.
382:Weald
363:Weald
322:Weald
283:Weald
206:Other
32:Late
630:2012
604:2012
438:Pett
436:and
422:Pett
420:and
291:Kent
289:and
269:The
214:Clay
131:Type
44:PreꞒ
451:at
348:of
324:of
36:to
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293:.
237:UK
212:,
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94:Pg
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632:.
606:.
99:N
89:K
84:J
79:T
74:P
69:C
64:D
59:S
54:O
49:Ꞓ
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
