generally the highest Jurassic rocks are only exposed near the eastern end of the Vale , as the Aptian and Albian transgress westwards on to older Jurassic strata . thus at Dinton , basal Wealden is preserved beneath the local Aptian , but by Tisbury Gault rests on Portland beds , on Kimmeridge clay around Shaftesbury and East Knoyle and by Penselwood Hill , five miles west of Mere , Albian rests on Oxford clay . ( b ) . brief history of previous work . the great variety of formations exposed within the Vale of Wardour has attracted geologists since early in the nineteenth century and there are many descriptions by many writers . Lady Bennett provided Sowerby ( 1818 ) with some of the earliest ammonites described from the Portland beds of Chicksgrove ( south ) quarry , and also referred to the Tisbury star coral ( Isastraea oblonga ) . the first comprehensive account was that of Fitton ( 1836 ) . he noted the sandy nature of the Chilmark building stones , found Purbeck dirt beds and discovered a cycad trunk near Tisbury . he observed the Hastings Sands ( Wealden ) above the Purbeck beds near Dinton and separated a sandy bed below the Gault which was later assigned to the lower Greensand . Fitton also realised that the Wardour fold was asymmetric , with steeper northern dips , and included a section diagram with his account . in 1856 there appeared the first one-inch geological survey maps of the area which had been surveyed by Bristow . in 1877 Blake &amp; Hudleston gave the first comprehensive account of the Corallian outcrop in north Dorset and were able to link up the north Dorset succession with that of the type locality at Weymouth . they described the apparent northward thinning of the upper Corallian . they also noted the increasing number of rolled corals in the upper beds in the same direction , and commented on the false-bedded Todber Freestones . three years later this was followed by a study of the Portland beds within the Vale of Wardour . in this paper they established , among other facts , that the upper Freestone building stones fifteen feet thick in the Chilmark Ravine are reduced to a two-foot band , crammed with Camptochlamys lamellosus at Chicksgrove and Oakley , within only one and a half miles . the nature of the junction with the overlying Purbeck has been much discussed since then , and is still not settled . in 1881 W H Hudleston led the first geologists &apos; association excursion to the Vale of Wardour and in the same year the Reverend W R Andrews ( 1881 ) , then resident at Teffont , published the first account of the presence of the middle Purbeck marine cinder bed in the Vale of Wardour . in 1894 this was followed up by a comprehensive description of the whole Purbeck sequence ( Andrews &amp; Jukes-Browne , 1894 ) , based on the Dorset ostracod divisions , but this was disregarded by Woodward ( 1895 ) when writing his survey memoir . by 1900 the geological survey completed the six-inch mapping for the new series one-inch map , sheet 298 , which includes that portion of the Vale of Wardour east of Tisbury . in the accompanying memoir ( Reid , 1903 ) he firmly established the presence of both Wealden and lower Greensand between the Gault and Jurassic beds . he also records seeing the Tisbury star coral Isastraea oblonga , already recorded by earlier writers , but in position of growth . this was observed in what must have been a temporary section , where a lane forks off the road from Tisbury to Fonthill , three-quarters of a mile north-west of Tisbury Square . on the other hand , Reid adhered to Woodward &apos;s interpretation of the Purbeck succession and discounted the unconformable Wealden boundary suggested by Andrews &amp; Jukes-Browne . the latter writer ( Jukes-Browne , 1903 ) added further material on the Purbeck-Wealden boundary and it appears that Reid &apos;s mapping followed Woodward &apos;s Purbeck divisions , and needs some revision to fit in with the palaeontological divisions now used . in the same year ( 1903 ) as the memoir appeared , there was a second geologists &apos; association excursion to the Vale of Wardour ( Blackmore &amp; Andrews , 1903 ) , and by 1904 Jukes-Browne had completed his survey of the cretaceous rocks ( 1900-4 ) , which includes descriptions of sections west of the area dealt with in the sheet memoir , some of which do not appear to have received any attention since . Jukes-Browne included a quarter-inch map , in his cretaceous rocks , part 1 ( 1900 ) , showing the Mere Fault , but no detailed mapping had been done . in the fifty years since 1904 there have been only a few further references to this interesting area . in 1933 Dr Arkell gave an admirable summary of the Jurassic rocks ; he followed up the earlier observations on the dissimilarities between the Chilmark-Tisbury building stones and the Dorset counterparts , and attempted to disentangle the confused ammonite nomenclature of the Portland beds . he placed , tentatively , but almost certainly rightly , the main Tisbury and Lower Chilmark building stones in the upper part of the Portland sands of the Dorset coast , only retaining the oolitic upper Chilmark building stones within the Dorset Portland stone . this will entail the remapping of the Wardour Portlandian to fit into the new classification . ( see also Arkell , 1935 , for correlation table . ) ( House , 1958 . ) in 1938 F H Edmunds added a contribution to the physiographical evolution of this area which accompanied the fourth geologists &apos; association &apos;s field meeting to the area . the next year , J F Kirkaldy ( 1939 ) refers to the thin lower Greensand below the Gault that crops out round the Vale , and also south of Shaftesbury , but he was unable to determine the zonal position of either outcrop . outside the Vale of Wardour proper , the Warminster Greensand beds at the base of the Chalk Marl have received attention from Jukes-Browne in 1896 , 1900-4 and 1901 , and from Scanes , jointly with Jukes-Browne , in 1901 , and with Pope-Bartlett in 1916 when , in the latter year , both authors led the third geologists &apos; association excursion . all the earlier Warminster Greensand accounts have been fully summarised by Edmunds ( 1938 ) for the fourth field meeting in the area of the geologists &apos; association in 1937 . it now seems clear that the fossils from the Warminster Greensand are Cenomanian in age and the majority did not come from Warminster itself but from Maiden Bradley and Mere . nevertheless , the Warminster name has been adopted for these beds , whereas today the best available section is at Dead Maid Quarry , Mere . also included in Edmunds &apos; account ( 1938 ) is the first contribution on the Mere Fault which was the present author &apos;s starting point for detailed mapping . Edmunds estimated the Mere Fault to have a northerly downthrow of about 600 feet near Charnage Quarry . he shows the fault to be reversed , passing just to the south of Mere , and downthrowing lower and middle chalk against Kimmeridge clay . Wooldridge &amp; Linton ( 1955 ) have given the whole area prominent attention in their comprehensive survey of the structure , surface and drainage of south-east England . they regard the three east-west lines of downland ridges comprising ( a ) the great Ridge-Mere White Sheet Hill ridge , and ( b ) the Barford Down-Berwick St John White sheet Hill ridge , and ( c ) the Melbury Beacon , Win Green-Coombe Bissett Down ridge as type examples of the remnants of the mid-late tertiary peneplains . also they regard the Wardour drainage as now adjusted to structure through two cycles of erosion and that the bulk of this area lay outside the furthest advances of the Pliocene Sea . at Whitsun in 1954 this writer led the fifth geologists &apos; association field meeting over the Vale of Wardour and the Mere Fault country from Shaftesbury . the field meeting report ( Mottram et al , 1957 ) included some of the more interesting localities visited from which the palaeontological records were obtained by various people , as well as brief references to the Mere Fault at West Knoyle , Charnage , Mere , Wolverton and Penselwood Hill , visited by the association during the excursion . ( c ) . tectonic summary of the Wardour anticline . the tectonics of the Wardour fold have not been described in detail previously , but much is self-evident from the new series one-inch map , sheet 298 , which shows the Vale of Wardour as far west as Tisbury and Ridge . the Wardour anticline has an amplitude of about 1200 feet so that around Tisbury the Cenomanian base must have risen to about 1000 feet above present O.D . the fold has steeper northerly dips than those on the southern limb , which are everywhere from 3-5 &amp;deg; south ( see fig 3 , section 1 ) . the northerly dips gradually steepen westwards and west of the Fonthills a 10-15 &amp;deg; NNW dip can be seen in planus zone chalk on the roadside from Tisbury to Hindon . the accompanying map to this paper ( fig 3 ) shows how the northern limb continues to steepen westwards past East Knoyle to where the Mere Fault begins at West Knoyle . north-west of East Knoyle , around Windmill Hill , the Green and Upton , there is quite clearly a local roll displayed by the upper Greensand outcrops . these double back eastwards from Windmill Hill to Milton before resuming their north-west trend along Haddon Hill . also the Gault base rises above the 600-foot contour west of Upton , so in this small and interesting upland area north-west of Clouds House there is a periclinal fold , pitching east , riding on the main northern limb of the Wardour fold ( see fig 3 , section 2 ) . in general the Jurassic rocks are nearly conformable to the overlying cretaceous , but these are local variations in addition to the steady westward cretaceous overstep . the Jurassic rocks within the Vale of Wardour are affected by a series of gentle rolls , trending north-west to south-east , which disappear under the transgressive lower Greensand and Gault without affecting them . the Portland beds , exposed in the Chilmark Ravine , are brought up by a shallow anticline and this is flanked to the south-west by a shallow syncline which brings the Wealden down to river level again near Sutton Mandeville . the next undoubted flexure affects the Portland beds south-east of Knoyle Corner , but is only partly preserved beneath the transgressive Gault above , and appears on the map ( fig 2 ) . around Tisbury itself the numerous Portlandian quarries show a variety of dips . some apparently can be ascribed to false bedding . this was seen in 1940 and 1941 in the temporary opening of a shallow quarry between road and railway 500 yards north-east of Hazeldon Farm ( 936381 ) . false bedding was also seen in 1949 in a new track section south of Court Street . however , in other pits , the dips appear to point towards the valleys . some of these exposures show considerable gulling , like those that can be seen in Tisbury west Quarry on the Newtown Road , and still being worked . this gulling recalls the cambered structures described in the midland Ironstone field and in the Oxford region by Hollingworth , Taylor &amp; Kellaway ( 1944 ) and Arkell ( 1947a ) respectively . it appears from notes on Reid &apos;s 1900 six-inch maps in the geological survey library , that much , presumably lower , Greensand debris still remains on the Purbeck outcrop around Lady Down and on the Portland outcrop north-west of Tisbury . this writer was able to map two definite outliers of lower Greensand on Lady Down and around Vicarage Barn , as shown on fig 1 . the lower Greensand , forming these two outliers , is thin , as the silage pit , four feet deep , reached the base of ferruginous sands , which also contained occasional small quartz pebbles . lumps of a very dark and hard ferruginous sandstone , recalling a tropical laterite , can also be found with ironstained Purbeck slabs in the surrounding arable fields . this thin veneer-like lower Greensand outcrop north-east of Tisbury suggests that the present Wardour Jurassic surface round Tisbury may be , in part , an exhumed pre-lower Greensand erosion surface . this is supported by finding further quartz pebbles and chert debris in arable fields on the Portland outcrop north-east of the cross-roads ( at 924293 ) on the Tisbury to Newtown road . this is south of where Reid mapped the lower Greensand being overstepped westwards by Gault near the Beckford arms . it is possible therefore that the existing post-Jurassic material on the Portland beds is the ultimate remains of the combined residue of lower Greensand and basal Gault hereabouts . across the Nadder Valley over the ground north-east of Wardour Castle the Portland dip slope disappears under rounded swells of lower Greensand and Gault above , before the land rises up towards the upper Greensand escarpment behind . 