AND HOGS BACK GEOWALK,

(embellished from a Geowalk established by Brian Harvey in April 2002)

This circular walk is about 7 miles (11 kilometres) and looks at the relationship between geology, topography, land use, building stones, industry etc. This is a particularly beautiful and interesting area, and the geology will be suitable for any level of expertise from beginner to expert. There is a pub, the Harrow, about half way round at Compton.

The walk starts and finishes at Mill Mead in Guildford town centre, located beside the and opposite the Yvonne Arnaud Theatre. Cars can be parked in the Mill Mead car park, map ref. SU 9950 4918 (44 spaces; free on Sundays only – 2011), or the nearby Portsmouth Road car park north of St Nicolas church (98 spaces; charges in 2011: Saturday £1.10/hour, Sunday £2.50 all day). Alternative parking is available in the Millbrook car park (from there walk down to the Yvonne Arnaud Theatre and cross the river by the footbridge). Mill Mead is within easy walking distance south of Guildford railway station. The route follows footpaths and tracks, some of which may be muddy, and there are a few hills to climb. Boots or walking shoes and a reasonable level of fitness are advisable.

Starting in the Mill Mead car park, cross the (white) footbridge and then turn right to take the gravelled footpath that runs between the River Wey on the right and the Wey Navigation canal on the left.

Stop 1 The canal lock on the Wey Navigation

This canal was one of the earliest in the country, having joined to the Thames in 1653. It was later extended southwards to join the River Wey here to the River Arun, thus creating a canal link to the south coast at Portsmouth. As with all canals, it was used mainly for bulk cargoes over long distances. Amongst other things, it carried from in the Godalming area (3½ miles south-west of here). Bargate stone has been used extensively in the local area, as we shall see, but it can also be found in at places like the Tower of London. This Guildford section of the canal was closed in 1871 – killed by the development of the railway network, although more recently there has been a revival of interest and work is underway to reinstate the canal link.

Continue walking south. After crossing a small weir, take the right-hand path immediately opposite Guildford Boathouse and continue along this path with the Wey Navigation on your left. Cross another weir and continue with the canal on your left.

1 Stop 2 Garden wall of Bargate stone (250 metres beyond the second weir)

The stone used in this wall came from quarries near Godalming. Bargate stone is part of the Lower Greensand, and it is more-or-less restricted to Surrey (small areas do spill over into Hampshire and Sussex). It is a calcareous sandstone that was deposited as a marine delta in shallow water, because the 'south coast' of at that time (120 million years ago) was slightly north of Guildford ! The stone in the wall here does show ooliths (they look like small ball bearings) and shells in places. Although the rock is relatively hard for this part of England, it weathers poorly because of the carbonate component, so the stone has to be replaced from time to time.

Then after 75 metres (noticing the blocks of slag used in the footpath), you come to a steep narrow path on your right, alongside a small stream and bridge. The path is Ferry Lane.

About 25 metres beyond the stream, and 25 metres before the footbridge that crosses the Wey Navigation, you can see a light brown outcrop in the wood up the slope to your right. Walk further south along the path and under the footbridge to a second, much larger outcrop 20 metres beyond the bridge, on your right.

2 Stop 3 Sand

This is our first view of the Folkestone Sand Formation. It is named after Folkestone, , where the beds were described in detail. Compare this sand with the stone we saw earlier in the garden wall: this is definitely not rock (although the face can stand vertically !). It is friable and easily 'carved', as you can see. It has remained as a sand rather than become a rock because it lacks any cement between the grains, and so water can move through it much more easily (to produce springs). We can look at the Folkestone Sand more closely at the next stop.

Here, we have a possible origin for the name 'Guildford', as the sand forms a 'golden ford' of lower ground at the river (or the canal, at this point).

Walk back north under the footbridge and take the narrow steep path (Ferry Lane) off to the left just beyond stop 3. Walk up the hill and onto the railway bridge, then another 60 metres (beware occasional traffic).

Stop 4 Grey stone wall on the left

Compare these building stones to those that you have seen beside the Wey Navigation. They form a retaining wall for the slope, and are definitely not local materials. They are mainly

3 granite, and probably from Cornwall. Looking closely you can see the different crystals that make up this rock – they are black (known as mica), white (feldspar) and grey (quartz).

At the junction with the main road (Portsmouth Road), turn right. After 50 metres, cross Portsmouth Road into Sandy Lane (i.e. 1st left),

Continue along Sandy Lane, with Bradhoeuf Manor on your left. After 175 metres, take the driveway off to the right, way-marked Way. Follow this track for 800 metres, to (and beyond) Piccards Farm.

Chalk

FAULT U. Greensand

Gault Clay

Folkestone Sand

Extract from Ordnance Survey map Licence number AL 100005035

= location

(Ignore the track joining from the left, 140 metres before the farm).

Pass through Piccard’s Farm and continue along the gently rising road for a further 400 metres. Then turn left (south) with the metalled road (at the notice marked ‘Private Please keep to footpath’).

Continue straight on over the brow of the hill (the Folkestone Sand ridge), ignoring both the driveway on the right way-marked North Downs Way and then the public bridleway, until you reach the grassy triangle and hairpin road of Sandy Lane.

Take the road straight on, now called Littleton Lane, down the hill past the toad sign (yes, toad) on the right. Walk on the right and beware traffic.

Notice how the lane is sunken into the landscape, with high banks on each side. The ground is still Folkestone Sand, and over many centuries wheeled traffic on this route has worn it away (until the erosion was halted by laying a tarmac surface).

4 Stop 5 beside the sign for Littleton village (stand off the road).

Here is a second small on the right (you may also have seen the first on your way down Littleton Lane). Directly across the lane (east) is the boundary between the Folkestone Sand to the left, and the hard Bargate Stone forming a solid vertical face (admittedly concealed behind a covering of ivy) to the right. Unfortunately it doesn't photograph well.

Continue downhill, and take the first turn to the right (west) just after Pillar Box Cottage, signed as a public footpath. Littleton Youth House will now be on your left. Continue straight on, through the kissing gate and follow the footpath across the grass.

Cross the field boundary (no gate), and start across open ground (the field on the left was ploughed in 2011, showing a sandy as would be expected on the Hythe Formation, as well as ?chert).

Continue on through another kissing gate next to the lake (crossing onto a strip of mown grass with a few seats). Continue west beside the lake and through the kissing gate at the far end, then keep the fence on your left.

Far to the left is Loseley Hall, famous for ice cream, outdoor events and animal breeding.

5 Building work on the Hall started in the 1500s, and apart from a new wing added in the 1600s (but later removed), the Hall is outwardly unchanged. Much of the cream-coloured stone used for construction was re-used from an earlier building: the ruined Cistercian Abbey at which was ten miles away from the Hall. That makes sense because of the local lack of thick rock strata that can be quarried for stone, and for the cost saving on the shaping of the blocks. Another geological aspect of the Hall is that the towering white fireplace in the Drawing Room is made of ''. Clunch is a harder type of chalk that is obtained from specific levels within the Chalk mass; it is harder because it has a natural cement between the grains. Clunch was also used to build . Once you reach the fenced track, turn left and after 280 metres cross the drive.

Where the fence very soon turns sharply left (south) follow it round and up a very gentle rise to the driveway of Loseley Hall. Then immediately turn right (west) along this long straight drive/avenue (of trees), away from the Hall and car park.

At a point 200 m beyond Polsted Lodge, the track bends right and drops, as Polsted Manor comes into view.

Turn left at the junction, with the buildings of Little Polsted directly opposite (and where “Polsted Manor” is marked on the 1:25,000 map), and follow the metalled road downslope and right.

At the T-junction keep ‘straight on’, following the road (i.e. keep right).

After 300 m, pass the housing estate on the right and then in another 100 m turn right (west) along the main road (the B3000) towards Compton. Then it’s just another 300 m to the Harrow Inn (on the opposite side of the road) which provides a welcome refreshment stop! (If it's open.)

Continue along the main road to St. Nicholas Church which stands back from the road on the left, 65 metres after the 16th century white, timber-framed ‘White Hart Cottage’, also on the left.

Stop 6 St. Nicholas Church.

brick and tile

Bargate stone

carstone

6

Spot the rock types used! (They include Bargate stone, Chalk, , carstone from the Folkestone Sand, and slate, as well as bricks and tiles that have been made from clay).

Continue for 350 metres along the main road …….

As you walk, note the 'galletting' (or 'garnetting') in many of the house walls, just as at Polsted Lodge. Here the walls are presumably newly reinstated, given their fresh appearance, using this traditional method to maintain the local character of the village rather than using just plain pointing.

...... then turn right, down Down Lane (just before roundabout at the end of the village) and after 180 metres you reach Watts Cemetery on the right. Enter the churchyard and look around.

Stop 7 Watts Cemetery Chapel.

This is terracotta work, with the raw material derived from Gault Clay. The chapel was designed and built by Mary Watts (with the aid of 73 local volunteers) as a memorial for her husband, the artist George Watts. It shows typical turn-of-the-century Art Nouveau, with influences from all over the place.

Behind the chapel at the top of the cemetery hill, take the straight footpath to the left that runs parallel to the northern boundary fence and so back down the hill towards Down Lane. After 25 metres, at the first two trees, walk to the fence on the right and then view the quarry on the right.

Walk back onto Down Lane and continue north for 70 metres to where the road bends to the left, just before Coneycroft Farm. There, turn off to the right through a wooden gate and along the fenced grass path beside the southern edge of the farmyard. The route is way-marked “public footpath”.

Turn left (north) at the far end of the hay shed, and then follow the arrow waymarkers, soon leading onto a concrete farm road leading east.

At the end of the concrete road, turn right through the gate and then immediately left/east (as way-marked) and effectively continue on eastwards for 260 metres

7 along a meandering and unfenced footpath through rough ground. (This is still following the alignment of the east-west fault mentioned above).

After walking that 260 metres east, by-pass a stile, bringing you directly alongside the fenced farm road on the left). The house ahead is Polsted Manor, again.

140 metres after the farm road turns north, at the bottom of a short steep flight of steps down, turn left up the narrow sunken footpath, away from Polsted Manor on the right. (However if you want to cut the walk short at this point, you could turn right here, and then left, to re-trace your steps along the outward route, back to Guildford.) Continue north, up the gentle rise and onto a non-sunken stretch of the path.

As you approach the tree-line (trees being a common indicator of Folkestone Sand) note the presence of carstone fragments underfoot already. However these would have travelled down- slope off the outcrop within Head/hillwash deposits (or perhaps by being kicked along the path?), so they rarely mark the exact junction. The footpath now becomes very narrow and sunken, with trees each side.

Stop 8 at this junction in the wood.

Within the slopes of exposed Folkestone Sand on each side there are obvious solid ribs of carstone, which form hard ledges and constrict the footpath. They also slow the rate of erosion of the surrounding sand. There is an exposure of the Sand itself at the top of the slope to the left (west) – see photograph above – showing the in situ bedding orientation, just above each of the red arrows superimposed on the photograph. The more obvious curves in the opposite direction are thin ledges of the carstone, which formed within the Sand millions of years afterwards. These sand faces also show light green algae / lichen on their surfaces, which is one explanation for the term 'Greensand' (the other being the inclusion within the sands of dark green mineral grains of glauconite).

At this junction turn right (east) onto the North Downs Way (between the signs on either side declaring ‘Loseley Estate Nature Reserve, Strictly No Admittance’ high up on the tree trunks).

8 Stop 9 where the wood gives way to open fields on left/north.

Upper Chalk Lower Chalk fault

Gault Clay

Folkestone Sand

Look north across the fields, towards the Chalk ridge.

According to the large-scale geology map, virtually all of the field directly in front of us (north), and thus the valley bottom as well, is underlain by Folkestone Sand, i.e. not Gault Clay as was the case earlier in the walk in Guildford. This is indicated by the lighter brown soil. The Gault then forms a narrow strip starting some 30 metres in front (south of) the first east-west hedge, i.e. just after the ground begins to rise, and it is also present in the ground directly behind the hedge. The approximate boundary between the strata can be picked out by the colours of the exposed soil in winter and spring, the more distant soil on the Gault band being much darker due to the grey colour of the Gault mudstone. Beyond the Gault, again in an open field, is a narrow band of Upper Greensand which forms a slight step in the topography (noticeable even from here in good light, and it can be seen later on), and then slightly higher up is an obvious old quarry (in the upper right of the photo above).

This quarry is probably wholly in Lower Chalk (so there's no Middle Chalk yet at this height on the slope). The quarry is supposedly the source of the stone for Compton Church, but that seems doubtful, as Lower Chalk weathers badly. With binoculars it’s possible to see that the chalk in the quarry is all green-grey (i.e. no white chalk), which is indeed indicative of Lower Chalk. Also, brown pyrite staining has previously been seen at two places to within about ½ metre of the top of the face. This quarry was known as the ‘Cherry Pit’ by the geologist G. W. Young in 1908: “a small exposure which yielded [the fossil] Glyphocyphus radiatus. Chalk hard and marly. ?Terebratulina gracilis”; this latter would suggest upper Middle Chalk. However, in 1927 Dines and Edmonds, in the Survey Memoir, wrote: “The quarry, one-sixth of a mile north-west of Conduit Farm, is entirely in the Subglobosus Zone of the Lower Chalk”.

Immediately to the north of Cherry Pit the BGS map marks an east-west fault, succeeded by a very narrow strip of Middle Chalk (i.e. cutting most of it out), before the Upper Chalk comes in to underlie the remainder of the slope up to (and just beyond) the ridge crest.

After walking 250 metres east from Stop 18, ignore the wide track joining from the right. Continue straight east, and after another 70 metres, at the base of the slight rise, turn left/north across the valley bottom (photo below), following the “public footpath” arrow (not the “bridleway” going east) and start the ascent of the Hogs Back ridge towards Conduit Farm buildings and the large pylons on the skyline.

9 Keep to the right of the farm buildings, and just beyond (north of) the farm, keep to the very narrow fenced footpath on the left side of the farm track.

Walking up the path, the soil lightens in tone (probably indicating chalky hill-wash from higher up), and when about 100 metres north of the northern-most farm building, you might discern a slight dip in ground level and then the slope flattens out, with nettles growing. Nettles show the presence of disturbed ground. This is the site of a former quarry in the Upper Greensand. In 1929 “4 feet of blocky, very hard, grey-white calcareous sandstone are exposed. Fossils here are common”. Two years earlier, in 1927, “a well-marked fault plane, filled with greyish blue clay in a band about 2 inches thick, was examined. The dip of this plane is about 60° north”.

Stop 10 Evidence for Middle and Upper Chalk

Look for closer evidence on and beside the path on your way up the hillside, in the form of temporary exposures and fragments of these Chalks. The two key features are firstly the change in the Chalk colour from green-grey to white, marking the change from Lower Chalk to Middle Chalk (together with the harder Melbourn Rock at this level), and then secondly the presence of flints in/on the ground, roughly marking the boundary between Middle Chalk and Upper Chalk (although there are some flints in the top of the Middle Chalk too).

Immediately the ground steepens there's white Chalk gravel underfoot, but flints are absent, so it is likely to be Middle Chalk. (However the geology map shows that there is actually little Middle Chalk present, due to the fault running across the hillside, and so we may already be on the Upper Chalk but between flint bands).

Locally on the path there is at least one small area of outcrop, initially seen as Chalk fragments (see the photograph below).

This fragmentation is probably the effect of frost-shattering on the near-surface Chalk, although it just might be a fault breccia (breccia = a rock composed of a mass of angular fragments created when the faulting occurred); it is difficult to tell when such a small surface area is exposed. Compare those random fragments with the photograph below.

10

Immediately beyond the fragmented Chalk in the first photo it may be possible to see the Chalk in place, as in the second photo, where the main fissures are aligned directly across the path, i.e. east-west, and the northerly dip of the strata can be seen here to be at around 45°.

Continue uphill. 15 metres after crossing the stile at the top, turn right/east onto the track of the now-quiet old turnpike road from Guildford to Farnham: the obvious traffic noise is the 'new' A31 and A3 on the northern flank of this Hogs Back ridge. After 250 metres there are pylons (communications masts) and a Thames Water reservoir on the right (south). Then after another 600 metres (and 260 metres before the entrance to Henley Camp on the left):

Continue past the gate across the track and past Henley Fort – an outdoor education centre – and about 60 metres beyond the Fort take the short public footpath to the left (note the loose grey ?Carboniferous Limestone gravel underfoot). Go through the lychgate onto the open ground (and then at least 20 metres to the right) for a view over Guildford.

Stop 11 View north with on a hill of London Clay (Stag Hill)

11 Interestingly, an old landslip is present directly behind the Cathedral, beneath the University buildings. The landslip is described in a textbook by Clayton, Simons and Matthews (second edition, 1995), and an extract from the book is reproduced here: “The north face of Stag Hill near Guildford, Surrey, was the site chosen for the . The reason why a site so close to the town centre of Guildford had not been previously developed was because of a large landslip which occupies the north face of Stag Hill. This landslip occurred on a 9° slope in brown London clay and its extent is clearly visible on vertical aerial photographs taken before construction of the university began in 1967.”

Also when looking north and east beyond Guildford, London can be seen if visibility is good and the sun picks out the various landmarks. Some of the features (from left/west to right/east) are Heathrow airport, the Wembley Stadium arch, the Post Office Tower, the Gherkin, the Shard, the Millennium Wheel (“London Eye”) on the Thames and the office towers at Canary Wharf.

Note the granite slab commemorating the Cornish March of 1497, seen in the photograph above. This was a march of some 15,000 men from Cornwall to London in protest against taxation by Henry VII to fund his military campaign in Scotland. They arrived at Guildford by 13th June 1497, and clashed here with cavalry the following day. Soon moving on to Blackheath in London, the marchers were there defeated and dispersed, with their leaders executed at Tyburn on 27th June. There is also a commemorative slate plaque at Blackheath.

The granite slab is from Trenoweth Quarry, near Falmouth in south Cornwall. The three main minerals making up the granite are the same as those you've already seen at Stop 7 (the wall of granite blocks in Ferry Lane, Guildford). They are mainly crystals of white opaque feldspar, together with black (actually dark brown) platy/flaky mica and light grey glassy quartz. There are also two dark xenoliths on the top edge (xenolith = fragment of country rock broken off and incorporated as the molten granite intruded it).

Turn back onto the turnpike and continue down the hill, along the road called 'The Mount', back into Guildford.

Note this is an exception to the rule that walking east or west keeps us on fairly level ground. The only reason for this slope is the presence of the River Wey, which has cut a deep south to

12 north valley through the Chalk ridge (and the Lower Greensand strata), and around which point 'Golden Ford' has grown up.

During the descent note the 85 metres of flint wall with brick coping of Guildford cemetery on the right (as in the photo below). This is additional evidence that Upper Chalk is very close by and provided the flints, and more specifically that local quarrying of the Chalk provided the large numbers of unweathered flints (those scattered in the surrounding fields are often of variable quality). The entrance to the cemetery is paved with carstone blocks brought here from exposures of Folkestone Sand, subsequently repaired with granite setts from much further afield. The author and mathematician Lewis Carroll (Rev. Charles Dodgson), 1832 – 1898, is buried here in the cemetery grounds (he died at his sisters' home in Guildford, of pneumonia).

At the bottom of The Mount (road) cross the Portsmouth Road at the pedestrian lights, then walk left and turn right, continuing down the short High Street, to St Nicolas Church and the car park.

13 SUMMARY OF STRATA

This information is taken from the British Geological Survey (BGS) map for the Guildford area, 1:50,000 scale, sheet number E285, and the accompanying Sheet Explanation. They are in time order, from the youngest deposits at the top to the oldest at the bottom. All except the Head are of Cretaceous age (145 to 65 million years ago).

HEAD (lithology determined largely by the parent materials upslope). (0 to >2 metres)

UPPER CHALK White chalk with nodular seams in lower part and courses of flint. [It (120 to 164 metres) forms the crest of the Hog's Back ridge].

MIDDLE CHALK White chalk with few flints [in upper part] and hard nodular Melbourn Rock (41 to 75 metres) at base.

LOWER CHALK Grey Chalk, in upper part interbedded with marl, passing down into grey (43 to 84 metres) or blue-grey thinly bedded marly chalk.

UPPER GREENSAND Pale grey siltstone with hard, grey to white, siliceous sandstone near top. (12 to 30 metres)

GAULT CLAY Blue-grey mudstone, yellow-brown when weathered. (80 to 109 metres)

FOLKESTONE SAND Fine to coarse cross-bedded sand, locally iron-cemented sandstone, (30 to 80 metres) locally pebbly at base. [Often forms higher ground, and wooded].

SANDGATE FMN Fine to medium poorly sorted glauconitic and ferruginous sand, with some (0 to 45 metres) clay beds.

BARGATE FMN Fine to coarse poorly sorted glauconitic sand with hard calcareous (0 to 20 metres) sandstone doggers (BARGATE STONE) at top and some cherty sandstone and chert beds. Quartz and chert pebbles locally common.

HYTHE SAND Fine to medium well sorted glauconitic sand, yellow when weathered, with (0 to 85 metres) some hard cherty beds near top [which are locally eroded].

ATHERFIELD CLAY Blue to blue-grey or red-brown or yellow silty mudstone, locally sandy, (7 to 20 metres) with seams of nodular clay ironstone.

WEALD CLAY Pale to dark grey mudstone, yellow-brown or locally red when weathered, (up to 454 metres) with interbedded thin fine to medium grained sandstone and shelly limestone.