HERTFORDSHIRE GEOLOGICAL SOCIETY NEWSLETTER WINTER 2019

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Working Party Annual Field Trip to Little Heath SSSI, Potten End Saturday 24th February 2018

We were lucky again with the weather, with a dry, fairly warm, sunny day, so the bottom of the pit was dry. Everyone came suitably dressed in hi-viz with stout gloves [Fig. 1] and carrying various gardening tools and receptacles. With increased numbers, we were not only able to remove the invasive saplings, brambles and other vegetation from the area cleared last year and clean the exposure, but also to clear an area to the left of the exposure that was not touched last year.

After three hours work the site was transformed - see below [Figs. 1(after) & 2 (before)]. All the vegetation was moved off site and deposited in another pit nearby with the agreement of the National Trust. The face of the exposure was cleaned by the removal of no more than one centimetre of material so that the features of the stratified sand could be clearly seen, as well as contact with the gravels above and below. Most of the group then retired to a local pub for a well earned lunch. We will be doing the same again on Saturday 23rd February 2019 so please come along and help.

Fig. 1: Working party in front of cleaned face [Photo: Nick Pierpoint]

1 Fig. 2: 10:00 - Before the start [Photo: Lesley Exton]

Field trip to the Lapworth Museum, Birmingham Saturday 3rd March 2018

Adapted from Nick Pierpoint’s write-up for the GA magazine by Lesley Exton

This trip had a good sign-up, with some choosing to travel by car and others allowing the train to take the strain, as the University has its own train station from where it is just a short walk to the museum. However, this time the weather was not on our side, with both the ‘Beast from the East’ and the ‘Pest from the West’ hitting the Britain the beginning of the month. So the expected party of eighteen was reduced to seven, as those who had opted to travel by road dropped out one by one, due to road journeys becoming unpredictable and risky in the snow and freezing conditions. Travelling by train was not without its stresses either, with the trains either side the one I (Lesley) was booked on cancelled. My train got to position one on the display board with no platform number, then disappeared. The information desk was then swamped, as all those passengers from the earlier cancelled train were expecting to travel on it as well! Turned out the train had sustained damage on its inward journey and was being repaired, so we were allowed to board after half an hour, once they’d put tape crosses on the two cracked windows. One of these was opposite my allocated seat, so I decided to move further down the carriage. This train then made an unscheduled stop at Watford Gap where Adrian, Helen, Nick and his wife joined, the laters seats being directly in-front of the seat I occupied. It turned out all seven ended up travelling up on the same train and we met up on the platform at Birmingham New Street waiting for the train to the University, only running a little late. The Museum Director Jonathan Clatworthy was then updated on our new estimated time of arrival.

The Lapworth Museum of Geology dates from 1880 being one of the oldest specialist geological museums in the UK. It is named in honour of Charles Lapworth, the first Professor of Geology at Mason College, a precursor to the University of Birmingham. The Grade II* listed building, retains its original Edwardian setting and interior, revealing it was initially home to the engineering

2 department, with the structural steel girders visible in the roof. The capacity to support engineering activities made it ideal for an ambulance station/workshop during WW 1 as this part of the University complex became a hospital.

We were given a warm welcome (including coffee, tea, biscuits) and introduction to the museum by Jon, during which he detailed the heritage of the museum, refurbishment project and the 2017 journey towards the ‘Museum of the Year 2017’ finals. This provided some insight into the extensive £2.7 million redevelopment which is reflected by the contemporary galleries and state of the art interactive exhibits; allowing the visitor to explore and be captivated by the wonder of evolution.

This was followed by a tour of the exhibits. As you entered each themed gallery there was a ‘star’ exhibit to catch your eye. One such was an interactive globe with some smart graphic technology which illustrated amongst other things how tectonic plates had moved through time. As anticipated the mineral gallery sparkled, it was neatly laid out – uncluttered and well lit. The museum has endeavoured to captivate both adults and children with some innovative child friendly glass fronted display cabinets.

There was a great rock wall from floor to ceiling, measuring 5m in height and with approximately 125 different rock samples from across the globe. Illustrating a huge diversity of colour, texture and fabric, included sedimentary, metamorphic and igneous rocks [Fig. 3].

Fig. 3: In front of the rock wall. [Photo: Jonathan Clatworthy with Lesley Exton’s camera]

Who is Charles Lapworth? Perhaps one of the most important and influential geologists in the late 19th and early 20th C; born in rural Berkshire where he trained as a teacher of English and Art. He was a self-taught geologist and in his early work in the Southern Uplands of Scotland he recognised the importance of the graptolite fossils for correlation purposes. The detailed field work and his re-interpretation of structures in the Southern Uplands prompted the Geological Survey to remap the area. Later his work on the Lower Palaeozoic fossil assemblages allowed him to demonstrate three

3 distinct faunas; thus, enabling clear distinction between the Cambrian (Sedgwick) and the Silurian (Murchison), and resulting in the Ordovician System to be introduced into our geological nomenclature by Lapworth. By the late 1870s his academic reputation grew and in 1881 he was appointed as first professor of geology at Mason College. Following his re-examination of the geological structure of the Northwest Highlands he realised that the superposition of metamorphosed gneiss and quartzite on top of limestone was due to thrusting.

After a break for lunch, making use of the meal deals at the shop in the refectory building as there was nothing else open. It was behind the scenes that our group enjoyed its greatest treat of the day – although just an hors d'oeuvre given our time constraints, we had the opportunity to examine some of Lapworths’ original documents, handle the Dudley Bug Holotype (Calymene blumenbachii) (Fig. 4), and also examine a wonderful set of Thomas Sopwith’s 3D wooden Geological Models which date from 1840’s (Fig. 5). Sopwith who became a mining engineer, built and used 3-dimensional wooden models of structural and sedimentary configurations for illustrative and educational purposes using different coloured wood to represent different strata.

Figs. 4 & 5: Dudley Bug Holotype (Calymene blumenbachii) (left) [Photo: Lesley Exton] and Thomas Sopwith 3D Wooden Models (right) [Photo: Courtesy Lapworth Museum Website]

Moving on to a different area, we read through a lecture note book from one of Lapworth’s students, Beryl Leslie 1887–, Nick later checked the GA records, but sadly did not find her name in the membership records. The GA was open to all from 1857 - the GSL opened its doors to female membership in 1919. On this theme, there was some fascinating correspondence between Sir Jethro Teall and Charles Lapworth bemoaning the opposition, by an elderly clergyman, to females attending GSL lectures. The clergyman was concerned about the potential flirtatious interruptions. Teall, who became head of the Geological Survey observed that most of the members of the GSL were too ugly to promote flirtatious behaviour and describe one of the elderly members as looking like a ‘gorilla’!

We examined cross-sections and notes from Lapworth’s field work in Scotland – and also a wonderful set of prints – an early version of ‘PowerPoint’. There were a series of graphics on fabric about 1.75m by 1.5m which would have been attached to a line hung across the front of the lecture theatre and could be conveyed across the field of view by a pulley system as Lapworth lectured. In all more than 30 illustrations survive, varying from cross-sections to images of Labyrinthodonts (fossil amphibia) (Fig. 6).

We are grateful to Jon for his time and enthusiasm as he enthralled the group with his knowledge, the museum displays and treasures in the collections and archives. Coats zipped and hoods up most of the party then departed through the snow back to the University station. I stayed for a while as I was

4 booked on a later train, however when I made my way down to the station every single train on the display board back into Birmingham was cancelled! So I had a long wait to get back to New Street, thankfully I’d given myself plenty of time so made my connection back to Euston.

Fig. 6: Banner of a Labyrinthodont (fossil amphibia) [Photo: Nick Pierpoint]

Field trip to Walton on the Naze Sunday 8th July 2018

By Mike Lambert

One scorching-hot day during this summer's heatwave, 20 of us from Essex and Hertfordshire geological societies gathered on the Naze to find out more about its cliffs and shoreline. As we were to discover, this headland, which is the most easterly point in Essex, has yielded fossils of national and international importance. And with this summer's news of wild fires inside the Arctic Circle and giraffes pictured in the snow, the day provided a stark reminder of how, even within a few million years, very different climatic regimes can impact a single location.

Our meeting point was Essex Wildlife Trust's new Naze Visitor Centre. Built with lottery funding, it is gradually being fitted out with exhibits and information-boards about the area's natural history - particularly its bird-life and geology. The foyer contains a display of local fossils, put together by members of Essex Rock and Mineral Society. Prominent in this collection is a massive tooth of the Miocene shark, Carcharodon Megalodon (Fig. 7). This warm water species is thought to have reached 18m and weighed 65 tons: making it three times longer than a modern great white shark and, almost certainly, the largest shark that has ever lived.

5 Our day began in the Centre's meeting room, with an introductory talk from Gerald Lucy about what awaited us in the cliffs. Considered in cross-section, the Naze headland comprises three main elements: a bottom layer of Eocene London Clay; a middle band of Pliocene Red Crag; and, at the top, a sequence of Pleistocene Gravel and Brickearth.

The Naze exposes the oldest part of the London Clay, known as the Harwich Formation, which was deposited close to the start of the Eocene (55 mya). This section of cliff has SSSI status on account of its fossil bird bones, which are often articulated. It is also internationally important for its seeds and fruits: with over 350 named species identified, making it one of the most diverse fossil floras in the world.

The London Clay was deposited under climatic conditions similar to modern-day Malaysia or Indonesia. At that time, the proto-British Isles were covered in rain forest and fringed with mangrove swamps. Very high rainfall meant that vast quantities of mud, containing wood and other organic remains, were washed out to sea. Thus, other fossils discovered at the Naze include: sharks' teeth, turtle carapaces and the bones of snakes, crocodiles and some important early mammals. The early horse, Hyracotherium (Eohippus), was first identified from a skull found at nearby Harwich in 1856 (prior to the better known Eohippus discoveries in North America). This dog-sized "dawn horse" was adapted to forest conditions, with padded toes rather than hooves: and several of its less important bones have been found at the Naze.

Above a lacuna spanning around 50 million years (which includes the Oligocene and Miocene epochs), the London Clay is overlain by Red Crag. This Pliocene rock is predominantly found in southeast Suffolk, and this is one of three outliers in Essex. It's somewhat older than the more northerly exposures and, for this reason, has sometimes been considered, separately, as "Waltonian Crag". It was deposited approximately 2.4 mya: at a time when much of East Anglia was covered by a shallow sea, and temperatures resembled those in the modern Mediterranean. This exposure of Red Crag has a separate SSSI status on account of its profusion of molluscs. Estimates as to the number of species vary between 100 and 300: depending on whether the taxonomist concerned is a "lumper" or a "splitter". Either way, it's a level of molluscan diversity that vastly exceeds anything in today's North Sea.

Figs. 7 & 9: A tooth of the Miocene shark, Carcharodon Megalodon, found at the Naze. Its high polish is entirely natural, and a feature of many of the fossils from the basement beds of the Red Crag (left) and shell of Neptunia Contraria (middle) and a modern whelk (right). [Photos: Gerald Lucy]

6 Above the Crag, the cliff is topped with two bands of Pleistocene deposits. The lower of these is a layer of Gravel, deposited by the Thames and Medway river systems, before they were shunted south during the Anglian glaciation, around 450 kya. The upper is a layer of Brickearth or Loess: a windborne sediment that accumulated in a periglacial environment during the most recent, Devensian glacial advance (115-11.7 kya).

Descending some stairs onto the beach, we had our first sight of the cliffs (Fig. 8). They are around 70 feet high, with the lower two-thirds composed of blue-grey London Clay. Above this, the Red Crag and Pleistocene sediments were clearly visible. Gerald pointed out some contorted patterning within the Brickearth, thought to derive from a prolonged period of freezing and thawing in a periglacial environment.

We then scrambled a short distance up the cliff, to where some fallen crag had come to rest on a platform of clay. From close up, the Crag revealed its loose, sandy and shelly texture. Its rust-red colour is thought to derive from iron pyrites that washed in from the London Clay, and then oxidised at a later stage. It was full of shell fragments and occasional complete shells, which were easily exposed by gently brushing away the surrounding sediments. In just a few minutes, we'd identified several species of bivalve, a miniature cowry, Trivia Coccinelloides, and two examples of the unusual, left-handed whelk, Neptunea Contraria. This Pliocene species spirals in the opposite direction to almost all other gastropods (Fig. 9).

Fig. 8: Naze cliffs, showing (bottom to top): dark London Clay; Red Crag; Thames/Medway Gravels; and Brickearth. [Photo: Nick Pierpoint]

Back on the beach, we turned our attention to the London Clay. Gerald pointed out how the blue-grey clay was occasionally streaked by paler bands of volcanic ash. Thirty six such bands have been

7 identified within the Harwich Formation: each corresponding to an explosive volcanic episode in Western Scotland. Thus, these ash bands are evidence of Atlantic rifting during the early Eocene; and they're roughly contemporaneous with the basalt flows that formed Fingal's Cave and the Giant's Causeway. Gerald speculated about a possible connection between such catastrophic events and the articulated bones of birds that might have been rapidly overwhelmed and buried by falling ash. It was also noted how this part of the London Clay is coarser and more silty than that found at Sheppey, presumably because the Naze deposits were closer to shore or a river estuary.

While exposing shells in the Crag is easy, extracting fossils intact from the London Clay is extremely difficult. For best results, blocks of the clay must first be soaked until they disintegrate, then sieved to reveal the often delicate fossils. In general, it's easier to let the action of the sea expose these items. And that’s why we next relocated to the water's edge.

While some of us sat on the beach - eating our sandwiches and enjoying the sea breeze - others scoured the bands of fine shingle left by the tide, in search of fossils. And, occasionally, a whoop of excitement went up as someone discovered a fossil seed-capsule, piece of pyritised wood or delicately-curved tooth of an Eocene shark.

But, what about that other, gigantic, Miocene shark's tooth that everyone had admired in the Visitor's Centre? How could such a Miocene fossil possibly have come from a cliff where Pliocene Crag lies unconformably on Eocene Clay? Gerald's explanation added another fascinating dimension to the story of the Naze.

During the Miocene, when the North Sea extended further inland than today, a tough sandstone, known as the Trimley Sands, was deposited. Then, in just a few million years, this rock was uplifted and entirely eroded back into the North Sea. None of this sandstone survives in situ. And, today, the only evidence of its existence are so-called boxstones: typically fist-sized, sea-worn cobbles of sandstone that were reworked into the basement beds of the Red Crag.

Gerald pointed out a few of these boxstones lying amongst the Crag debris. Occasionally, these boxstones contain the fossils of Miocene molluscs; and the Ipswich Museum has a Megalodon tooth in a matrix of boxstone-type sandstone. However, most often, these larger, more durable fossils - such as sharks' teeth and pieces of whale bone - are found matrix-free and much abraded by their time on an ancient sea-floor.

What an extraordinary journey these Miocene fossils have been on, since their formation, a mere 7-5.4 mya. First fossilised and uplifted within the Trimley Sands, they were soon eroded back out to sea. Then, after a period of abrasion on the Pliocene sea-floor, they were reworked into the basement beds of the Red Crag. And now, that Red Crag is releasing them for their third spell beneath the waves. (For a fuller account of these remarkable fossils from the basement beds of the Red Crag, see Tim Holt-Wilson's recent article: Boxstones - in search of Miocene Suffolk. Deposits Magazine, No. 54, 2018, pp. 9-16.)

For anyone planning a trip to this fascinating and unique location, please note that Essex Wildlife Trust have just published a full-colour, fold-out guide called the "Naze Geowalk". Written by local geologist, Mike Sandison, it describes a circular walk, over the cliffs and back along the beach, detailing points of geological interest en route.

8 The HGS Summer Event: Geo-ramble around Tring Park Saturday 9th September 2018

By Lesley Exton

Twenty members met at 10.00 in the car park for a gentle 3 km informal walk. Tring Park is one of Hertfordshire’s most important ecological sites covering an area of 264 acres. It contains a mosaic of habitats such as chalk grassland, scrub, mixed woodland and parkland landscaped by Charles Bridgeman in the late 17th and early 18th C. The chalk grassland is the second largest in the county, of exceptional quality, and an extremely rare habitat and one of our SSSI’s. Tring Park was once part of a larger estate which included Tring House and Gardens, but these were cut off from the rest of the site in the 1970s when the A41 was built.

We made our way first to look at the dendritic pattern of five shallow dry valleys cut in extensive bench at the base of the main chalk scarp on the southern site of Trip Gap. This represents a fossilised drainage pattern created during permafrost conditions. Bench is formed of the Middle Chalk with no hard band to explain its origin. It is thought to have originated by glacial erosion in the Anglian Stage. If this is the case then the Anglian limit lies further south in the vale of Aylsebury than previously though.

The dry valley pattern results from stream erosion in the post-Anglian periglacial environment with the streams draining into the Tring Gap.

We then continued up to King Charles Ride and walked along this path from which there were good views of the Chilton Scarp (Fig. 10). Before cutting down to see one of the two ancient monuments that can still be found in the grounds, an obelisk known locally as Nell Gwynn’s monument. We didn’t have time for the second, which could be seen in the distance, the remains of a summer house

Fig. 10: View from King Charles Drive. [Photo: Lesley Exton]

9 which Dame Peggy Ashcroft lived in during WWII. We then made our way back, via the bridge over the A41 back to the car park.

Those of us who had booked for lunch then walked over to the Kings Arms, down the middle of the road as the way the cars were parked over the pavement made it impossible to walk on. After an excellent meal there, those of us that wanted to, made our way to the Natural History Museum in Tring and had a look round the galleries there.

Field trip to the west of Ireland 20th- 23rd September 2018

By Lesley Exton

When Liam suggested a visit to the land of his ancestors for our 2018 long weekend trip, Haydon knew just the man to lead it. He’d met John Graham as a postgraduate student and knew of his interest in the geology of Ireland so put the two in touch, this field trip was the result. Participants had to make their own arrangements to get to Ireland West Airport (Knock) where they would be picked up and transferred to Westport, our centre for the field trip. Most arrived on Thursday either late morning or early afternoon and spent the rest of the day exploring the town and quay, before meeting up with our leader at the hotel in the early evening. A few, however, had decided to come a day early in order to attempt the climb of Croagh Patrick, Ireland’s holy mountain, and Liam and Cath had a far more eventful journey than the rest of us due to Ali, the first named storm of the season.

The geology of western Ireland preserves the Laurentian cover (Dalradian) in North Mayo, ophiolite remnants, an accretionary complex in the Clew Bay area, and arc volcanic rocks and their associated forearc basin in South Mayo. In the Caledonides the region is unusual in preserving, in Connemara, a Laurentian cover sequence (Dalradian) to the south of scarcely deformed arc rocks. The overlapping of the timing of events in Connemara and South Mayo has led to various suggestions as to when their current juxataposition occurred.

On a very changeable Friday (due to the tail-end of Ali) we focused on the arc volcanics, largely early Ordovician in age, their coarse gained mid-Ordovician sedimentary cover and the unconformably overlying Silurian succession. The Lough Nafooey Group is divided into 3 or 4 units, the lowest being a series of altered basaltic pillow lavas (spilites), succeeded by a series of more evolved volcanic rocks, then another unit of more basic eruptive rocks. This was where we started with the Knock Kilbride Formation which did show some good pillow structures but was dominated with more massive lavas. The only age control for the area comes from a thin graptolitic mudrock horizon just north of where we were. We then moved down the succession to the more silica rich volcaniclastic deposits of the Finny Formation (Fig. 11).

The Ordovician rocks that crop out over much of South Mayo are preserved in the South Mayo Syncline. While the two uppermost formations are common to both limbs, there are significant differences in the lower formations. The south limb succession, the Rosroe Formation, and our next stop was dominated by conglomerates with abundant arc debris. This formation is important in terms of its provenance and in assessing potential linkages to Connemara whose geographical position in the Ordovician remains the subject of speculation.

The Silurian dips steeply south and rests unconformably on the Lough Nafooey Group that dips very steeply northwards. It starts with the Lough Mask Formation, non-marine strata, these are then succeeded by the Kilbride Formation, a shallow marine quartzose clastic unit in which were seen Skolithos burrows and corals. Red and green mudrocks, the Tonalee Formation indicative of an outer shelf environment follows, which in turn is succeeded by coarse grained volcaniclastic turbidites, the

10 Fig. 11: Silica rich volcaniciastic depostis of the Finny Formation [Photo: Lesley Exton]

Fig. 12: Derryveeny Formation a unit of conglomerates and sandstones [Photo: Lesley Exton]

11 Lettergesh Formation. It is likely this succession represents a rapid deepening due to localised subsidence produced during strike slip adjustment during orogenic stabilisation.

After a welcome lunch of soup and sandwiches with a view at Marie Lukes (prearranged as they only usually serve food on a Sunday) we made our way to Derry Bay through a bogwood landscape to the Derryveeny Formation, a spectacular unit of conglomerates and sandstones (Fig. 12). The conglomerates are dominated by metamorphic debris and are unconformably overlain by the Killary Harbour succession. They have been accepted to provide a sedimentary linkage with Connemara.

Our next stop an old quarry cut into one of the Tertiary dolerite sills, on Drumcoggy Mountain also provided excellent views. Eastwards we could see the lowlands of the mainly Visean Carboniferous limestone, westwards the basal Carboniferous conglomerates of the Maumtrasna Plateau. When the faulting took place to produce this geometry remains unresolved. Southwards we could see the next storm rapidly approaching.

Our final stop for the day was in a zone of strong deformation trending north-east south-west, the Bohaun Shear Zone. Pillow lavas are still evident in these basic volcanic rocks of the Bohaun Volcanic Group but are very strongly elongated (Fig. 13) .

That evening we made our own arrangements for our meal. We also ordered packed lunches at reception for the following day, if required as there was a cafe at our lunch stop. However, unfortunately the second set of orders never made it to the kitchen and as their was no identification on the orders, there we no packed lunches left for those who were last to pick them up. The next morning, reception had written room numbers on all the sandwiches, however, we almost ended up with two extra as they said they were all for us. It wasn’t until we pointed out the room numbers didn’t belong to any of our party that reception remembered they were for some fishermen.

Figs.13 &14: Pillows are still evident in these basic volcanic rocks but are very strongly elongated (left) and tabular limestones with Syringopora corals (right). [Photos: Lesley Exton]

Saturday was far calmer and brighter and we focused on the Carboniferous geology of North Mayo which rests unconformably on the Dalradian succession.

Starting the day at Bunatrahir Bay near the base of the Downpatrick Formation, a marginal marine and non-marine mixed unit with clear tidal influence and abundant evidence of desiccation, paleosols, ostracod rich limestones of restricted environments and more tabular limestones with Syringopora corals (Fig 4). It also introduced us to gilgae structures (Fig. 15), which most of us hadn’t heard of

12 before and are produced by repeated swelling and desiccation under strongly seasonal conditions.

A drive down a narrow road brought us to Downpatrick Head and after a short walk we reached the cliff edge from where we could see Dun Briste Stack, the lower parts of which are the Downpatrick Formation. It is capped by the tabular limestone from the base of the Moyny Limestone Formation. After looking at Dun Briste Stack from both sides, keeping well away from the edge of the cliff (Fig. 16), we then moved over to the west side of Downpatrick Head. Here we were able to examine the gently inclined typical mixed nature of the lower part of the Moyny Limestone Formation. We returned to the coach via the blowhole, now safely fenced off, complete with viewing platform and explanation boards.

Fig. 15: Gilgae structures [Photo: Lesley Exton]

After lunch at the Céide Fields Visitor Centre, Ballycastle we had a guided tour around an excavated stone wall of one of the fields of the archaeological site. It is the most extensive Neolithic site in Ireland with the oldest known field systems in the world, 12km2 have so far been mapped . Most of the remains of the stone field walls, houses and megalithic tombs are preserved beneath a blanket of peat. Looking back 6000 years this area would have been pasture, however a drop in temperature and an increase in rainfall created ideal conditions for a blanket bog to form. Climate change in action. Before we left we nipped across the road to the Céide cliff section viewpoint, whose base is the top beds of the Minnaun Formation, middle beds the Downpatrick Formation, and top beds the base of the Moyny Limestone Formation.

Our final stop of the day was Kilcummin Head where we looked at the upper part of the Mullaghmore Sandstone Formation, which was deposited following a sea level drop in Arundian times. Examples of tidally influenced fluvial deposits, shallow shelf deposits with hummocky cross-stratification and inner shelf deposits with evidence of wave action and bioturbation could be seen (Fig. 17).

13 Fig. 16: Dun Briste Stack [Photo: Lesley Exton]

Fig. 17: Inner shelf deposits with evidence of wave action and bioturbation [Photo: Lesley Exton]

14 That evening we were picked up by the coach and taken for a very enjoyable meal down on the quay, after watching a very colourful sunset.

Sunday morning focused on the geology of Clew Bay. Scattered outcrops along the south side preserve elements of an accretionary complex, a dismembered ophiolite and an unconformity. We started the day by ascending the first part of the Croagh Patricks pilgrims path. The first exposures on the west side were low grade metasediments of the Killadangan Formation, part of the Clew Bay Complex that is currently thought to be part of the Dalradian succession. A little further up we encountered serpentinites with strong S-C fabrics, part of the dismembered ophiolite. We hadn’t time to go further up but the Clew Bay Complex is unconformably overlain by the strongly deformed Silurian Croagh Patrick Succession. Quartzone sandstones in the lower part of the succession form the crags of Croagh Patrick above us which a couple of the party had climbed on Thursday.

Before we descended we first turned round and looked across the bay. Clare Island to our left lies within a major Variscan fault zone that downthrows Carboniferous rocks to the north. Erosion of these softer younger rocks produced a topographic low in this area that was exploited during the Quaternary glaciations. As a result the bay contains a myriads of islands which is actually a drowned drumlin field (Fig. 19).

Fig. 19: Drowned drumlin field of Clew Bay. [Photo: Lesley Exton]

Our second stop was the eastern end of Falduff Strand. The fine grained rocks here belong to the Knockmore Sandstone Formation whose bedding dips moderately steeply east, but is actually overturned. Most of it is grey, but some thin red mudrock horizons help define the bedding and small scale folding, whilst internal laminations can be seen on some of the wave polished sections. Evidence for desiccation in some of the red mudrock layers supports the idea of a fluvial origin for these rocks but their exact age is unknown. As we approached the major Emlagh Fault the number of calcite veins and minor folding increased. On the other side of the Emlagh Fault low grade

15 metasediments are identical to the uppermost Dalradian seen on the north side of Clew Bay.

After no rain since Friday, a heavy shower coincided with our arrival at Thornhill so not everyone made it to the beach. Here a major post-Carboniferous fault sub-parallels the coast so the low tidal, mostly dolomitised, rocks east of Lecanvy pier are Carboniferous, and in the cliffs we could see a cross-section through a drumlin. There are two lithofacies associations, the upper is composed mainly of massive diamictons with some concordant sandy interbeds, the lower lithofacies is dominated by limestone rich diamicton with sandy and gravelly interbeds.

Fig. 20: The group sitting on the Ballina Limestone Formation [Photo: Kath Gallagher]

After dropping John and those that were staying on for a few more days back in Westport, it was time for most of us to head back to the airport and our flights home. Many thanks to John for a very enjoyable trip and an excellent field guide which has been heavily used for this write-up, and to Liam & Cath Gallagher for organising the logistics of the trip which meant it ran very smoothly.

Hertfordshire RIGS Group update

By Haydon Bailey

There have been a few changes in the Hertfordshire RIGS group over the last year or so following the retirement as Group correspondent of John Facer and the untimely death of John Catt in December. The role of Group correspondent has now been taken on by Haydon Bailey, with Margaret Selby acting as Treasurer and the rest of the HGS Society undertaking site monitoring.

We’ve been pretty active over the year with the annual clear up of the Little Heath site, just outside Berkhamsted in February this year (see Fig. 1). A write up of the geology of this site is currently in

16 hand, with work being carried out by Clive Maton and Tim Atkinson.

In addition to this we have recently assisted North Herts District Council and Hertfordshire County Council Countryside Management Service in drawing up Management plans for two chalk pit sites, at Hitch Wood and at Barkway. Both these sites have been somewhat neglected over recent years and the change of ownership to the district council has introduced new vigour and possible finance into their management.

The Hitch Wood site is an important palaeontological location with numerous ammonites, sponges and inoceramid bivalves originally recorded from the Hitch Wood Hardground (part of the Chalk Rock complex) during the 1920’s. It was originally designated as a SSSI in 1957, but downgraded to a RIGS site during the 1980’s (Fig 21).

Fig 21: Current state of the chalk pit. [Photo: Haydon Bailey]

In contrast, the Barkway site comprises two imbricate glaciotectonic blocks of “Middle” Chalk, including the Chalk Rock, stacked at approximately 30 degrees and separated by a thin periglacial clay layer (Fig. 22).

Both sites are very important in the geological interpretation of the region and the Hertfordshire RIGS Group is pleased to have been closely involved in the development of the management plans for both. Plans are now afoot to clear vegetation, and to clean up the faces in order to bring both sites back to workable geological use.

17 Fig 22: Barkway site – as it used to be and what we’re trying to restore it to. [Photo Plate 6: John Catt Hertfordshire geology and landscape]

John Catt (1938-2017) HGS President (1977-80 & 2013-5), HGS Chairman (1980-99) & HGS Field Secretary (1999-2013)

By Haydon Bailey

John Catt was upright, modest and a gentleman, in every sense of the word and he is deeply missed by all his wife Diana, his family, colleagues and friends. John was born in Kent on April 10th, 1939 the son of a gardener who worked at the local Church of England vicarage. The Anglican Church was an institution he was soon introduced to and one with which he remained closely associated for the rest of his life.

John was educated at Ashford Grammar School and, in November, 1956 he made the arduous train journey northwards to be interviewed by Lewis Penny, then Head of the Geology Department at the University of Hull. He was immediately offered a place to read for a joint degree in geology and chemistry at this flourishing department. However, to quote John, “after the first breathless year of 22 hours lectures plus 12 hours practical classes per week I pleaded with Lewis and John Neale to join the special (single) Honours Class in Geology.” John never looked back; he gained a 2.1 degree which gave him access to a doctoral scholarship to study the Quaternary of East Yorkshire.

The next three years were, according to John, “the happiest and most stimulating of my life.” He completed his thesis within the requisite three years of his grant in 1963 and immediately took up the position of Scientific Officer, in the Pedology Department at Rothamsted Experimental Station, Harpenden, Hertfordshire. He stayed at Rothamsted effectively for the rest of his professional career, rapidly progressing to Principal Scientific Officer in the Soils and Plant Nutrition Department by 1977 and becoming Deputy Head of Rothamsted (Acting Head of Soils and Agronomy Department) in 1988. He continued his research into soil erosion and the leaching of nitrates, phosphorus and

18 pesticides in clay soils at Rothamsted from 1990 – 1998 and after this, until 2016, as Honorary Professor of Geography at University College London.

Fig 23: John Catt

John’s academic career speaks for itself, as author and co-author of almost 200 peer reviewed papers plus a series of books, including “Soils and Quaternary Geology”, “Soil Management: Problems and Solutions” (with M. A. Fullen) and, last but by no means least, “Hertfordshire Geology and Landscape”. This major publication (published 2010) was a labour of love which John had taken on as co-author and editor from the late Percy Evans in 1975. It is a hugely respected publication which sets the standard for books on local and regional geology. In addition, he supervised 14 PhD students during his career and provided supervision for a further ten visiting scientists during their time at Rothamsted.

John was awarded a DSc in 1981 by the University of Hull for his research into Quaternary Geology and Soil Science and he was awarded the prestigious John Phillips Medal by the Yorkshire Geological Society in 2004 recognising his contribution to Pleistocene and Quaternary Geology in the region. He served as both Secretary and Vice President of the Quaternary Research Association and was President of the Palaeopedology Working Group of the International Soil Science Society. He became a founding Fellow of the Institution of Geologists in 1985 and a Chartered Geologist in 1991; he served on numerous scientific advisory committees and was elected as Vice President of the Geological Society of London in 1996. The Society recognised his services to science in 2015 when they awarded him the Distinguished Service Award. His research into palaeopedology, stratigraphy and the palaeoclimatic interpretation of Quaternary palaeosols led to him being appointed as Visiting Professor of Geography at Birkbeck College London (1988 – 1998), Visiting Professor of Soil Science at the Agricultural University of Prague (1993 – 1999) and Visiting Professor at the Centre

19 for Earth and Atmosphere Sciences, University of Reading (1995 – 1999). John was the most modest of men, and colleagues and family were often unaware of his distinguished academic career, frequently remarking that “he kept his light hidden under a bushel”.

Throughout his life in Hertfordshire John was dedicated to the geology of the county, being at times Chairman and Honorary President of the HGS and a stalwart member of the Hertfordshire Natural History Society who gave him their highest award in 2013. He was made the first Honorary Member of Hertfordshire Geological Society in March, 2017.

His death, in December 2017, followed a persistent lung complaint, which resulted from an infection acquired during an International Quaternary (INQUA) Conference in China in 1991. Appropriately, John is buried in the Anglian gravels which rest on top of the Chalk at St. Stephens Church, St. Albans.

Chairman’s concluding remarks

By Haydon Bailey

Firstly, a big Thank You to all of you for your continuing support for Hertfordshire Geology and the HGS. It’s been an interesting year in our new venue which seems to be working reasonably well. Nowhere is perfect, but Oaklands does seem to tick most of the boxes. The HGS committee has decided to give this venue another twelve months to make sure that we’re all happy with it. If we’re not, then we can always start the search elsewhere. Speaking to members of other groups, finding a cost-effective suitable base seems to be an ongoing problem in several different locations. Nice to know we’re not alone!

There have been a number of notable HGS events during the year, including our annual spring clean at Little Heath on a “fresh” day in February. This was given greater impetus as Clive Maton was able to bring us (literally) up to date with a potential age for the sediments of approximately 2.7ma +. This is critical to our understanding of the uplift of the location from sea-level to 165m above OD.

The trip to the Lapworth Museum was somewhat reduced in attendees due to adverse weather conditions, but the really keen members managed to get there despite the snow and ice. Other field trips during the year to Walton on the Naze, Essex with Gerald Lucy, and our Geo-ramble around Tring Park were both excellent days out.

The highlight of the year has to be the trip to County Mayo, Ireland in September, organised by Liam and Cath Gallagher and ably led by Prof. John Graham from Trinity College Dublin. They organised the weather – admittedly quite badly for their own travel, but ideal for everyone else. The hotel was well located and very comfortable and a whole list of transport arrangements worked perfectly. It really did work very well and we saw some amazing, if slightly mind bending, geology over the weekend.

It’s been said to me over the year that “we punch above our weight” when it comes to attracting high quality speakers and looking back over this year’s programme we really have listened to a first rate range of topics. Long may this continue and I‘m looking forward to 2019 already.

Finally, I couldn’t finish this note without paying tribute to the leadership we received for so long from John Catt, who has been sadly missed this year. Being able to help Diana sort out John’s library has been a fascinating element through the year and I’m so pleased that we’ve been able to keep a large part of it together by donating the Soil Science section to the RHS at Wisley. See you at the John Catt Symposium in July 2019.

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