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10th April 2018 – Geology of Beachy Head

On a rather cool and misty day, twelve members of SNHS met at the kiosk next to St. Bedes, Eastbourne. Led by Ken Brooks of the Hastings & District Geological Society, an expert on the chalk, we took the cliff top path towards our destination, Cow Gap.

En route we stopped at Whitbread Hollow, a U-shaped valley (or coombe) created by solifluxion, a process whereby ice-age permafrost had fractured the chalk through freeze-thaw action, eventually causing the unconsolidated, saturated rock to slowly slip down towards the sea, creating the valley. We also noted the contorted trees, wind-pruned in the direction of the prevailing wind, and Jenny Wistreich pointed out that this is where the game of Quidditch was filmed for the Harry Potter films, although the mist prevented us from seeing the blue plaque hovering above the pitch!

Further along we stopped at a point overlooking the beach, and, using a diagrammatic model, Ken explained that the repeated bands of gault clay, greensand and chalk visible on the beach were caused by rotational slipping, where the underlying Gault Clay, when saturated, facilitates the rotational slipping of the overlying rocks into a near vertical position. Subsequent erosion by the sea planes off the overlying slumped material, leaving a wave-cut platform showing a gault/greensand/chalk sequence. Further slippages lead to repeated sequences of gault/greensand/chalk. This repeated sequence puzzled early geologists and was not resolved until the first half of the 20th century, when it was finally realized it was a planed-off surface of a series of repeated rotational slips. Further evidence of this slipping could be observed looking up at the cliff, where stepped ledges could be seen at various stages of slippage, as well as the backward sloping angle of some of the lower ledges.

On reaching Cow Gap we descended to the beach where both the Lower Chalk and blocks of the underlying Upper Greensand could be observed. Ken explained the nature of the chalk and some of the fossils it contains. The chalk itself was laid down during the Upper Cretaceous period between 98 and 65 million years ago. At the time of deposition temperatures were in the range of 20–30⁰C, considerably warmer than today. There were no polar ice-caps, and warm temperate vegetation extended up to latitude 85⁰ North. At their maximum, sea levels were around 300 m higher than today, and the chalk sea covered most of the UK, apart from the Scottish Highlands, and extended right across northern Europe into Central Asia. Over the last 65 million years much of the chalk has been eroded away, although deposits remain around the globe, including those that form our iconic cliffs along the south-east coast of England. Historically the chalk has been divided into three groups – the Lower Chalk, Middle Chalk and the Upper Chalk – but work by Professor Rory Mortimore of the University of Brighton has shown that there are nine distinct groups in the chalk, the differences between these groups attributed to tectonics (the movement of the Earth’s tectonic plates), temperature, and a process known as Milankovitch Cycles, where the Earth’s distance from the Sun and tilt of its axis varies over time, altering the amount of solar radiation reaching the Earth and leading either to a die-off of marine organisms or an increase in algal blooms. These changes are visible in the sequences of the chalk. The same fossils found in the chalk cliffs of Sussex have also been found in the chalk deposits of Europe and Asia, allowing geologists to confirm the existence of the same beds over thousands of kilometres. Ken also showed us SEM images of coccolithophores, tiny single-celled phytoplankton (algae), made up of minute calcium carbonate plates called coccoliths. It is these plates, only a few microns across, that are normally found in the fossil record, and the chalk is composed of countless billions of these tiny skeletons. Ken also explained that the flint in chalk was formed by the chemical precipitation of silica from the breakdown of skeletons of dead organisms such as sponges and diatoms.

The chalk marl (Lower Chalk) found at Cow Gap is packed with fossils, mainly the remains of sponges, standing proud of the softer chalk, and black phosphatic coprolites (fossilized poo!). There is also extensive fossil evidence of burrowing by bivalves and other marine creatures, a process known as bioturbation. As we walked east towards Beachy Head we observed more fossils embedded in the chalk, including fine examples of the bivalves Spondylus and Inoceramus. Some good examples of pyrite (fool’s gold) were also found where they had been selectively sorted around a rock by tidal action – when broken open these showed their characteristic radiating structure. Ken also demonstrated the scratch test whereby we could tell the difference between calcite (scratch leaves white mark) and the much harder silica (scratch leaves grey mark). We continued to the headland from where we could see the Beachy Head lighthouse and the chalk deposits higher in the sequence – the much whiter Middle Chalk, overlain by the Lewes Chalk and Seaford Chalk.

At this point we turned and retraced our steps to Cow Gap and back along the cliff path to our start point, and as we did so the mist finally cleared and the sun came out – Oh well!

Peter and Joyce Austen

SEM

SEM of coccolithophore; a tiny single-celled algae, the plates of which make up the chalk. Image: Dr. Jeremy Young (NHM, London), 2009.

















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17th April 2018 – Coach outing to Wisley

A full coachload of us set off at 9am and enjoyed a pleasant drive to Wisley, arriving a little after 11 am. There we divided into two groups for a guided tour of the garden. Our leader was knowledgeable and so enthusiastic that the tour lasted longer than expected at just over two hours.

He began by briefly explaining the origins of the garden. In 1804 John Wedgewood, the son of Josiah Wedgewood, and six other keen gardeners founded the London Horticultural Society. One of the members was Prince Albert who occasionally provided financial support because the Society was hopeless at accounts. In the mid-1850s the name was changed to Royal Horticultural Society, and in 1903 the RHS moved to its present location – it was said at the time that because of its remote position not many people would come! Nowadays it is the second most visited paid garden after Kew.

At the start we admired the oak tree which is 235 years old and unusual in that the branches cross into each other. On the way round some of the facts imparted were that there are over 110,000 crocus, over 4,000 roses, 140 different types of pear and 400 types of apple, and one of the longest mixed borders in the country. Also of interest was the Wollemi tree, thought to have become extinct in Australia but rediscovered in 1994. Also seen were date, banana and olive trees. Our guide also mentioned that trials of plants are conducted at Wisley with the successful ones being given an Award of Garden Merit (AGM). He also pointed out grass art where a tulip pattern had been created in the grass using a Victorian lawn mower. On one particular day when a survey was carried out this proved to be the most popular out of all the attractions at Wisley! Later on we were able to see for ourselves grass art being carried out in another part of the garden. We saw the alpines in the glasshouse, the vegetable garden, the rock garden, and the greenhouse opened in 2007 by the Queen. What was striking is that the garden is very labour-intensive, although extremely well kept by a staff of 90 plus volunteers.

Looking ahead to the future, Wisley is in the middle of an extensive refurbishment. There will be a new welcome centre and many of the old buildings, including a purpose built laboratory built during the 1st World War, will be replaced. It is hoped that the new science laboratory currently being built will provide facilities for secondary as well as primary children who are currently catered for.

We ended the tour by looking at a larch, the oldest tree in the garden, which is over 235 years old. Afterwards we were free to wander round at leisure until 4 pm when we set off for Seaford, arriving shortly before 6pm. Certainly a most enjoyable and interesting day, made even better by the kind weather.

Susan Painter

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1st May 2018 - SNHS bird walk around Seaford Head

Following our now well-established pattern, Derek Barber and I met the first group of rather more enthusiastic birders at 07:00 and then the second larger group of 20 assembled in the South Barn carpark at 10:00. Overall, both walks were conducted in glorious weather, which made it a pleasure to be out and about, but in all honesty one would have to concede that bird numbers were relatively low and rarities (or even scarce species) were conspicuous by their absence. Both walks began well, however, with the appearance of several very handsome wheatears around the dung heap just west of the South Barn. By the end we all had good views of three magnificent male wheatears resplendent in their blue and buff summer plumage accompanied by three almost equally attractive females and all performed well at relatively close quarters.

By the time we got to Hope Gap the first common whitethroats had also made their presence felt with repeated song flights from the top of the low bushes and a fair number were recorded along the path, as were several chiffchaff and up to 20 willow warblers. Indeed, despite the general paucity of birds, it was clear that there had been a minor fall of willow warblers overnight. By the time we reached the middle of the track down Hope Gap we had also scored with a superb lesser whitethroat and although this was seen by only a few members of the group, at Hope Bottom we all watched another from close quarters. As this was a much more confiding bird we were each able to see the subtle silver-grey and white plumage that makes this such an enchanting species - and incidentally one of my favourite British.

At the bottom of Hope Gap we watched the resident rock pipits and stonechats, while over the cliffs there was the usual mix of fulmars and kittiwakes among the gulls and jackdaws. Scanning close inshore, however, we picked up three whimbrels, several noisy oystercatchers and three passing bar-tailed godwits while further out there were five distant gannets flying in line, easily distinguishable by their large size and shape, their striking white plumage and prominent black wing tips. Best of all, however, while watching these we also discerned the menacing shape of a dark phase Arctic skua flying in a typically determined manner low over the sea. This was the first skua ever recorded on these walks but alas it was seen by only a few of the more experienced birders.

As we made our way across the meadow towards Harry’s Bush a common buzzard suddenly exploded from the trees and spent some time circling overhead before drifting off towards Friston Forest. Finally, Derek spotted the bird of the day in the shape of a truly lovely male whinchat, which was happily viewed through the telescope by virtually all of those present. From Harry’s Bush it was also possible to see several of the now extremely familiar little egrets on the lagoon on the other side of the river - and there was time to reflect on the fact that this now common bird in Sussex was only 30 years ago regarded as an extreme mega-rarity in the UK. All in all, then, while admittedly not a particularly memorable birdwatching experience, in such superb weather it was an enjoyable enough way to spend a few hours and the discovery on the clifftop of a small patch of flowering early purple orchids still in pristine condition only added to the general sense of well-being.

Bob Self

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15th May 2018 – Lewes Railway Lands

About 12 of us met the Ranger, Thyone Outram and Education Officer, Milly Hawkins at the entrance to the Reserve, on a warm and sunny day. We started with a quick tour to the Linklater Pavilion with Helen Meade (the Programme Co-ordinator). The Pavilion is a purpose-built information and education centre for the Reserve, with a range of sustainability features (including a grass roof!). A series of aerial photos showed how the Reserve had developed since its inception in 1995. More information about the Reserve can be found at www.railwaylandproject.org.

Heading out into the Reserve, we started at the Mound – an artificial feature designed to give a good all-round view of the Reserve. We observed the stand of Black Poplar (Populus nigra), which is the most endangered native tree species in the UK; an intensive replanting programme is underway under the supervision of Kew.

We then proceeded to the artistically-designed reed beds, where we could hear (but not see) reed warblers (Acrocephalus scirpaceus). Plants in the area included Jack-by-the-Hedge, or garlick mustard (Alliaria petiolata). This species is the food plant for the orange-tip butterfly (Anthocharis cardamines), which always lays a single egg near the flower – and we found one! Nearby, there were numerous mating pairs of the dock bug (Coreus marginatus).

Moving on to the grazing meadows (not part of the Reserve), our attention was drawn to the extensive drainage ditches. These had been found to contain a number of rather rare water beetle species, and management had been designed to encourage them (eg by dredging the ditches a few at a time, so there would always be suitable habitat). We didn’t note any beetles, but there were a number of other species. The most obvious inhabitants of the ditches were marsh frogs (Pelophylax (formerly Rana) ridibunda), which were croaking vociferously during our visit and were easily seen. This is an introduced species and is the largest European frog. It has become widespread throughout Kent and East Sussex and is a voracious predator (this may explain the absence of beetles!).

A number of dragonfly and damselfly species were patrolling the ditches. We identified both males and females of the broad-bodies chaser (Libellula depressa) and the azure damselfly (Coenagrion puella). We were also fairly certain of the hairy dragonfly (Brachytron pratense).

Amongst the plants in the ditches, we found frogbit (Hydrocharis musus-ranae), celery-leaved buttercup (Ranunculus scleratus), a water-crowfoot, probably the thread-leaved water-crowfoot (Ranunculus trichophyllus) and fool's watercress (Apium nodiflorum).

Returning via the former allotments, we made one last discovery – horseradish plants (Amoracia rusticana), growing by the side of the path.

We are very grateful to Thyone and the Railway Lands Trust for a very enjoyable and informative visit.

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29th May 2018 – Abbots Wood

On an overcast day with the threat of a thunderstorm 18 of us met up with Stuart Sutton, a Wildlife Ranger for the Forestry Commission. He told us that this had been an ancient woodland site for about 600 years. Between the wars many of the native trees were cut down and after the 2nd World War under the Duke of Devonshire’s ownership conifers were planted so that when the Forestry Commission took over ownership in 1954 the wood was very dark. As it is no longer permitted to plant conifers in an ancient woodland, this has created the challenge of how to get revenue from the trees now being planted. Most of them like oak, cherry, hornbeam and small leafed lime take many years to grow before there is any monetary return and although hornbeam is very slow growing it will nevertheless have to be coppiced to get some revenue from it. In future it may be possible to introduce wild service trees since they provide good quality veneer after a relatively short time.

Stuart has been working in Abbots Wood for 24 years and has seen many changes in that time. To begin with there had been no deer; now there are such large numbers of roe (native), fallow and muntjac deer that they need to be culled. Before we set off he warned us to watch out for timber lorries although we were likely to hear them before we were seen!

We began by walking along the east/west ride where we soon saw a speckled yellow moth, and a longhorn moth. Once trees have been coppiced fences are put round them for protection from deer. Roe deer eat bramble, fallow deer graze grass areas, and muntjac deer eat anything. However, nothing attacks bracken which is now a problem although its presence may lead to the reintroduction of the high brown fritillary which died out in the seventies. Another problem is squirrels which strip cherry and oak trees, and eat birds’ nests. The Forestry Commission control rabbits and deer but not squirrels. A mulcher is now hired which reduces trees into woodchips, a quick fix in winter but it cannot be used when birds are nesting. They also try to avoid killing any dormice but the mulcher is being used for the benefit of all wildlife. Because the ground is turned over they get solitary bees and wasps. Stuart mentioned that nightjar numbers have declined and there was a solitary pair of turtle doves last year.

We then went through an area which was cleared 3 or 4 years ago. It is beginning to develop as a wildlife meadow, although the bracken is growing too much despite being cut in February. We saw soft rush and lesser spearwort, and heard a blackcap. Numbers of garden warblers are good. Stuart pointed out a squirrel’s drey and a survey will be conducted this year to establish whether there is a buzzard’s nest among a group of larch trees. If so the trees cannot be felled because there will be an exclusion area.

He pointed out the track of a young roe deer saying that they will go round wet areas wherever possible because they do not like wet ground. We then passed by a Douglas fir plantation planted pre 1954, where brooklime (Veronica beccabunga) and elder were seen. Crows used to roost here and there used to be firecrests. Now the firs which will eventually probably blow over, are just being retained for birds like goldcrest and siskin.

Continuing on we saw ash trees with die back. This is a windblown fungus which can’t be stopped although Stuart has the hope that some may win the battle. Nearby we saw a dark bush cricket nymph and a common spotted orchid.

Next, we stopped to look at an area where spiked rampion had been growing, one of only half a dozen sites in East Sussex. Six years ago 50 plants were planted protected by fencing from deer and rabbits. Despite deliberate management the numbers had dwindled down to none last year but the reasons remain unclear.

Later Stuart showed us a trick with a wood ants nest. He irritated them with a bluebell and they sprayed formic acid which turned the bluebell pink.

By the lake, dug by hand, we heard a reed warbler over a noisy song thrush. In order to protect the fish it has been decided to clear some of the water lilies and a sluice may be installed to create two types of water habitat. Nearby we looked at an area where a mulcher will be used this coming winter to remove tree stumps in order to encourage heather, mainly ling, to grow. Then before doing a detour through rough ground to see dragonflies in one of the 5 dragonfly scrapes, albeit without success, a great spotted woodpecker was seen.

On the fritillary ride we hunted for the pearl-bordered fritillary and the small pearl-bordered fritillary, spotting one pearl-bordered fritillary. Pearl-bordered fritillary prefers woodland clearings and bracken habitat while the small pearl-bordered fritillary favours the edges of rides. Both nectar on bugle. Abbots Wood and Park Corner Heath are the only places in Sussex for fritillaries.

Towards the end of the walk two nightingales were heard using a contact call; and ragged robin, wood euphorbia (both native) and orpine, (native ancient woodland plant) were seen. Also hornets and a possible sighting of a malachite beetle.

All in all Stuart proved to be a very knowledgeable and interesting leader and everyone came away having learnt something new.

Susan Painter

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12th June 2018 - Riverside Park, Newhaven

On a cloudy morning, 25 of us met up with Virginia Pullen of East Sussex County Council to walk round Riverside Park, Newhaven. Virginia gave us a very interesting talk about the site at an indoor meeting in January 2017 and this walk was by way of being a follow up.

Riverside Park is predominantly located on a brownfield site, the area having been used for landfill in the decades between 1960 and 1980. Behind the football pitch and play-area is a wide range of habitats spread over about 2 hectares. The low lying areas next to the river have a role in the flood defences for Newhaven and in this area there are reed beds, drainage ditches, salt marsh and ponds. Unfortunately some of the ditches have been affected by seepage from the landfill site though there is no information as to whether this has significantly affected the ecology. However, there is not a lot of methane on the site. As the ground rises there is old meadowland, banks covered with scrub and then a central area where the landfill site has been capped off with a thin layer of soil brought from out of the locality. The site is an SNCI (Site of Nature Conservation Interest). Its mixed soil types mean that there are many plant species to be found there and it is good for birds and grass snakes but, so far, not for amphibians.

The first thing you see on the way in is a children’s playground – the site is well used by locals – and the second some metal sculptures with cut out shapes of birds etc. We followed a largely metalled track around the site in an anti-clockwise direction. Initially, the path is lined with trees planted about eight years ago and there was a wide variety of flora, including red campion, teasels, elder in flower, poppies, fodder vetch and weld. Perhaps the most striking thing on the first part of the walk was the profusion of hemlock, looking a lot like cow parsley but over 6 feet tall and very poisonous. Virginia explained it may have come in with the soil used to cover the tip and rather than try to eliminate it, they were aiming to help people understand which plants to be wary of.

There were a lot of nettles by the path some of which had been cleared (by contractors) to reveal comfrey. In other places, rabbit grazing had made space for white campion and tormentil and we also found bee orchids and cinnabar moths. By this time, we were just to the west of the incinerator.

Mike Kerry had done a couple of reconnoitres of the site and commented that he saw more on the reconnoitres than on the day. However, he did see two bees - Bombus pratorum and Bombus lapidaius - on bramble; plus Volucella bombylans (a bumble bee mimic hover fly) and a snipe fly. A number of birds were seen or heard including Cetti’s Warbler, green finch, whitethroat, green woodpecker and a kestrel.

At the north end of the site, there are wet lands and, following scrub clearance, ponds will be created, hopefully encouraging toads and other amphibians. This is the only part of the site where there is no risk of leaching from the old tip and therefore the only place it is possible to put in ponds. There is also an owl box nearby.

Further on we saw viper’s bugloss and there was considerable speculation on its name. Accounts vary but one suggestion is that the name refers to a time when the plant was used to treat snake bites. We also saw yellow-wort, fleabane and patches of sedge. (Chris Brewer later identified the sedge as the club- rush Bolboschoenus maritimus (Sea Club-rush) which has a triangular (triquetrous) stem. Club-rushes are apparently not members of the Rush (Junceae) family but members of the Sedge (Cyperaceae) family and not all members of the sedge family have 3-angled stems. Common Club-rush has a round stem.)

Crossing the site towards the west we saw scrapes created to see what grows there, large patches of bird’s foot trefoil and a bird hide. And on the way back we spotted figwort, honeysuckle, horseradish, mullein and mullein moth caterpillars.

Altogether a fascinating tour of an area over half of us had never visited before, but one many people thought they would return to for its interesting variety of habitats and flora.

Anne Fletcher (with thanks to Marion Trew for the second paragraph).

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page updated 5th July 2018