DRY VALLEYS of the SOUTHERN PENNINES, ENGLAND with 2 Figures Gordon T

Erdkunde Band XVIII 116_ 2: and of ? Fig. Dry deep canyon Bregava River (Hercegovina) Contour intervall 100 m. Although this is an old about 1000 its sides are in canyon (relative depth m) very steep spite of younger evolution of the slope. In the a when the river flowed at means higher parts, during period surface, by of differential erosion in the impermeable rocks Bregava River formed Dabarsko polje. The eroded detritus must, therefore, have been To conclude: Allogen rivers have only cut ca evacuated It a underground. is, consequently, fea nyons in pure limestone, and this kind of valley ture in in a created karst, i.e., region where during is typical for them. More regular features of river its water creation, deeper fissure-circulation of erosion and slope washing appear in regions of took Its flat limestone bottom place. ideally and mixed lithological composition and do not belong are the sudden transition into steep sides further into typical karst scenery. Unusual features of elements that specific disagree with the laws of surface levelling and differently moulded lime river erosion. stone slopes are remnants of a period when the as well as level Valley-like depressions ground climat favoured plane corrosion (Flachenkorro in pure limestone cannot be explained with river sion).We suggest to discontinue the use of the term which can cut into rock. erosion, only canyons this "karst valley" because it was adopted at a time The other must valley-like features be accounted of insufficient knowledge and of a mistaken con for in the corrosion by changes process in different ception of land form development in limestone. climats and under corresponding ecologic condi Moreover, the term is also illogical. tions. DRY VALLEYS OF THE SOUTHERN PENNINES, ENGLAND With 2 figures Gordon T. Warwick Introduction similar features are to be found on many porous sandstones and as In the British Isles most attention has been paid conglomerates such Cannock even on to the dry valleys of the chalk of S.E.England, but Chase, Staffordshire and quartzites they are equally important in areas underlain by (Lickey Hills, Worcestershire) and Keuper Marl, limestones of Cambrian, Silurian, Devonian, Car though the latter are usually confined to valley boniferous, Permian and Jurassic age. In addition heads and minor gulleys. In this paper the author Gordon X. Warwick: Dry valleys of the Southern Pennines, England 117 wishes to discuss the nature of the dry valleys cut ing stages in their progressive incision. These into the Carboniferous Limestone of the Southern valleys are flanked by a series of dry tributary Pennines, an area usually referred to as the Peak valleys. Flanking all but the southern side is an District, mainly inDerbyshire but partly in Staf almost continuous rim of escarpments, interupted fordshire. The general account is illustrated by partially on the eastern side by the Derwent examples chosen mainly from the Dove-Mainfold valley. and Lathkill systems. The central plateau is composed of Carbonife Various have been forward to hypotheses put rous limestones of Visean age, for the most part the of One of explain dry valleys S.E.England. well-bedded, pure limestones interbedded locally themost has been that of Reid and popular (1887) with contemporaneous lavas and tuffs and inparts Bull that were (1936, 1940), considering they of the south-east converted in places to dolomite. the colder of the Pleisto produced during periods Nowhere is the base exposed and the limestones cene when this area was to con subject periglacial rest upon an old basement, presumed to consist of of the and the ditions, involving freezing ground Pre-Cambrian rocks, which has been proved to lie of considerable amounts of snow. Chand melting 270 m below the middle of theWye valley floor ler and Fagg stressed the (1909) (1923, 1954) (Cope, 1949). A further 450 m. of limestone lie of retreat in the water importance scarp lowering above the stratigraphic level of the bore-hole table of whilst Sparks and dip-slope valleys, (Wray, 1954). On the western edge of the block Lewis (1957) advocated spring-head sapping as discrete masses of reef limestone are found which the formative for the which bite agent dry valleys have weathered out into upstanding hills and into the chalk of the Chilterns near escarpment westwards the limestones change to a basin facies Hertfordshire. of Pegsdon, Subsequent lowering with thinner limestones and a greater water proportion the table having lowered the outlet of the of shale. Similar reef limestones flank the northern new saps are now into the spring, proceeding dry edge but basin facies are not exposed there. The floors. A similar has been valley origin suggested old bioherms are traversed by major joints which for Rake Bottom on the Hants-Sussex border by are roughly parallel to the surface of themass, and R. J. Small, (1958). Other writers suggest that the these are the commonest locations for caves. The dry systems an valley originated upon imperme limestones are overlain by Namurian shales and able cover which has now been eroded away and sandstones in an unconformable relationship, in the down of the streams lowered cutting major the south-west they can be seen to be banked up the water table in the chalk and led to the regional against old features with at least 150 m. a landscape progressive dessication of the valleys, view sup of relief. Indications that the limestone surface ported Pinchemel Linton over by (1954). (1956) the plateau area was also irregular are given adopted a similar idea to the explain dry valleys by the two outliers of shale shown on figure 1 of the Southern Pennines, and thismode of origin which lie at the bottom of topographic depressions, is favoured the writer. For certain by dry gorges surrounded by higher limestone hills. The cuestas such as the Cheddar Somerset, Gorge, hypotheses surrounding the plateau are formed of coarse sand of cavern collapse have often been put forward, but stones or grits, but in the south only shales seal with little detailed examination of the and ground off the limestone, succeeded in turn by Triassic of typical cave Trueman marshalled plans. (1938) deposits which only make direct contact with the some of the counter an arguments for entirely sub limestone in the south-west. aerial origin for Cheddar F. Bennet Gorge. J. The dominant structure of the limestone is a (1908) put forward the notion that some of the broad dome with an axis running NW-SE, but this dry valleys in the calcareous sandstones of the is complicated on the east a series of anticlines Hythe Beds of Kent were due to solution and sub by and which eastwards and sidence. synclines pitch produce the sinuous eastern outcrop of the limestone. In The Peak District the south-west the structure istmore complicated The heart of the area a a is limestone plateau and series of folds and parallel faults swing from which rises abruptly in the south to a general a NW-SE direction to the east of Dovedale into a of 280?340 metres A a height above sea-level. long N-S direction long the Manifold Valley (Par low rises to m. swelling ridge up 50 above the gene kinson, 1950, Prentice, 1951). Some of these ral level forming the divide between theWye and folds were initiated in Lower Carboniferous times Dove drainage systems. The northern part has but the major earth movements occured in the rather relief and a greater somewhat greater alti main Variscan folding in Permo-Carboniferous tude. The shown on 1 have no major rivers, figure times. There has been further folding though cut into the deep valleys plateau surface, though some upwarping is presumed in connexion with traces are of wider valley floors to be found mark the Alpine disturbances. 118 Erdkunde Band XVIII LEGEND v?^ limestoneboundary ) s^^^^^^^^îl { T" ) LsC" ~^-A l ^ permanentstreams "^^^^1^^^ '"'''^^^/^^-^Tx r~~^ r" temporarystreams ') j^VÎ ^ X ' active effluent \ ....}y" '^<- ^n^.... ÂT^^ ^âT^C . /^ :\ .^?3 active influent iv-J/ <^^,. ? 1. ? ? 1 ? miles C/^^^^, /C^r^^ 01 234 5678km j ^ I ^'^T^'^CVji l) ^\\^^_x / Fig. 1: Drainage system and dry valley network of the Peak District Gordon T. Warwick: Dry valleys of the Southern Pennines, England 119 The Dry Valley Systems ses through a flooded section to come into day below the main cave mouth. Here some roof The relationship between the dry valleys and light fall may have assisted the formation of Cave the limestone is clearly shown on figure 1, though Dale, but the action of the outflow must a few small dry valleys do occur on the shales. sapping present two con have been as The stream They fall into main categories, the first ? just important. rising here Peakshole Water, flows in a wide sisting of larger tributary valleys, usually on NW valley cut in the shales but bordered on the southern side SE lines which usually grade into the major val a side of limestone seamed with short leys with little altitudenal discordance. The other by valley dales. group is formed of smaller tributaries with few dry branches which often above themain streams. hang The River Lathkill The upper parts of both types of valleys are usual System ly gently graded and in the case of the first group Only half of the main valley is ever occupied often consist of a wide "bowle", oval or circular by a flowing stream and the upper dry part con a or in shape leading to dry valley gorge with sists of an elongated bowl centred upon the village steep, rocky walls and steeper gradient which may of Monyash and leading into a dry gorge with or more exhibit one dry knickpoints of varying steep rocky sides.

Load more