We met at Butser Ancient Farm near Petersfield, Hampshire. Although I had been past it many times this was the first time I had visited. What a surprise! If one ignored the cars, one could be back in ancient times, standing outside a ditch and bank earthwork containing a large roundhouse fully 15m in diameter, plus three other smaller huts. Soon we were seated on logs around a blazing fire in the hut, whilst Jonathan Edwards, the Education Officer for Buster Ancient Farm explained some of the aims and objectives of the site and the details of the construction the roundhouse.

Butser Ancient Farm is an open-air laboratory devoted to the exploration by direct experimentation of the problems and theories which emerge from archaeological excavations. The focus of the site is the Iron Age (1000BC - 43AD) and the Roman period (43AD - 400AD), plus an interest in the development of archaeological technology. The central feature of the site is the enclosure round the Great Roundhouse has been re-constructed. The Great Roundhouse is most impressive and is based on excavations at Longbridge Deverel Cowdown in Wiltshire. It is built on the double ring principle. The inner circle of posts with a horizontal ring of timber mortised and tenoned into place sustains the weight of the roof of over 25 tonnes! Undoubtedly, the house was the dwelling of a rich and powerful person, but there was little evidence of how the interior was laid out, apart from post holes and the hearth. As we sat around the fire, there was little to remind one of the 21st Century and it was easy to project one’s self backwards and to speculate what it could have been like to be an Iron Age farmer listening to an elder of the group explain the passing of the seasons and the working of the land.

Outside, our guide (and lurcher dog) walked us around the site through the Welsh roundhouse from Moel y Gerrdi and the two smallest from Glastonbury Lake Village, then to the ditch and bank that forms the boundary of the enclosure. This ditch and bank itself is one of the experiments taking place on the site. Normally ditches start in a "V" section with the bank on one side, formed of the spoil. The archaeologist normally only finds the ditch, the bank material having been back-filled. The silting and erosion layers found in the ditch can be used to deduce the location of the bank, since they are often asymmetrical. The Butser ditch and bank is been used to test this deduction. Since the plants which colonise the ditch and bank have an influence on the erosion, these are also being studied.

After the Iron Age, it was fast-forward to the invasion of Britain and the Romans. A major experiment is underway to reconstruct a specific Roman building of the late 3^rd/4^th centuries, paying particular attention to the operation of an aisled hypocaust. The original building was excavated at Sparsholt, north of Winchester in the 1960/70's. Although the walls have been laid out on the original pattern and the walls built to just below first floor level, the experiment is concentrating on the north end of the building to explore the hypocaust.

After a brief return to the Iron Age and a look at the crops being grown to examine the potential yields of ancient farms and farming methods, and hence may give insights to the numbers of people that could be supported, we were brought back firmly to the 21st Century and the Geophysical Research Area. Any fan of Channel 4's Time Team will know the importance of "Geophys" to modern archaeology. At Butser, a testing ground has been built to provide a known range of archaeological features - ditches, gullies, wall foundations, post holes, pits, hearths and kilns, floors and burials. These have been meticulously constructed and recorded, so that new developments in geophysical prospection machines can be tested. We were lucky enough to talk to two of the scientists involved and to see the features that they were working on - we are now sworn to secrecy!

All too soon it was time to leave Butser in our chariots - sorry - cars, and make our way across Hampshire to the Weald and Downland Open Air Museum.

Set in 50 acres of beautiful Sussex countryside, the Weald and Downland Open Air Museum is a fascinating collection of nearly 50 historic buildings dating from the 13th to the 19th century, many with period gardens, together with farm animals, woodland walks and a lake. Rescued from destruction, the buildings have been carefully dismantled, conserved and rebuilt to their original form and bring to life the homes, farmsteads and rural industries of the last 500 years.

We started our visit firmly in our own time, at the Gridshell. The upper part of the building, the Jerwood Gridshell Space provides a workshop where historic timber-framed buildings can be laid out for conservation and repair. The size of the space allows for large frames to be assembled and it will also be used for the museum's growing programme of training workshops and the conservation of large objects. It is also used for exhibitions and other events. The basement store is secure and environmentally controlled and houses the Museum's collections of tools and artefacts from rural life in the region numbering about ten thousand items. Agriculture, domestic life, trades and industries and transport are all represented, and there is a special emphasis on building construction and the building trade.

A gridshell is a structure with the shape and strength of a double- curvature shell, but made of a grid instead of a solid surface. The grid can be made of any kind of material, but the Downland Gridshell is made of slender oak laths bent into shape. To prepare the oak laths for use all defects were removed and the resulting pieces finger-jointed together into standard lengths of 20 feet (6m). Six of these pieces were then joined to form 120 foot (36m) laths. The diagonal grid of laths was initially formed flat on top of a supporting scaffold. The edges of the grid were then lowered gradually, and the grid bent into shape, until the full shell was formed and secured to the edges of the timber platform above the basement. The grid is actually a double layer, with two laths in each direction. This is necessary in order to combine the required degree of flexibility with sufficient cross section for strength. A fifth layer triangulates the grid to increase its stiffness. The laths are connected at the nodes of the grid with a patented system of steel plates and bolts.

From the ultra-modern of the Gridshell, we plummeted back into the Medieval past so that Diana Smith could take us on a guided tour through the history of Wealden vernacular buildings. Diana firmly anchored her explanations of the architecture and the materials used in the buildings, in the geology of the Weald. I have been to the museum many times, but I was able to see it through new eyes due to Diana’s skill and knowledge. One of the highlights for me was the Watermill from Lurgashall, a 17th century working mill. We were lucky enough to have guided tour from the miller himself and I took the opportunity to buy a sack of flour for home bread making – delicious!

All in all a very good day out – many thanks to Diana for making it so interesting.

I volunteered to write up the first day of our trip to the Catalonian part of the Pyrenees because I knew that it was going to be interesting and so it was, and complex, and mixed and very enjoyable.

First the weather, when we woke the weather in El Pont de Suert was sunny – it augured well for the day I thought! My gloves scarf and woolly hat stayed in the case. Waterproof trousers went into the rucksack along with suntan cream and my lunch. We left the hotel in sunshine looking towards the white tops of the mountains in the distance. They began to become shrouded in mist, O.K. it was still quite high – no problem! We travelled on and the mist got thicker and lower. We reached the first stop, close to the tunnel, and got out of the vans. The weather closed in. Bitterly cold and blowing a gale – then the snow came down. It was freezing – out came the waterproof trousers and I wished that I had taken the hat, gloves and scarf too. Undaunted we went to look at the rocks. It was a relief to go back to the vans. The snow did stop and the sun did come out but it did not get a lot warmer. By the time we had our lunch high on the side of a mountain we were able to sit outside, admire the view and what could be better than lunch surrounded by mountain peaks with snow in the background.

So what of the rocks? In a word - complex. To set the scene. The Pyrenees were formed as a result of the Iberian lands being pushed up towards and skewed against Europe, initially during the Hercynian orogeny between the Carboniferous and Permian, and latterly during the later Alpine orogeny. The central table land of the main craton has been around since the Precambrian and it has been moved around and much altered during its long existence. The oldest rocks we were to see would be the latest Precambrian, sandstones and shales deformed at the end of the Precambrian. The conditions would have been dry and hot with little input. There would have been an abundance of algal mats and dolomitic limestones typical of low input, high energy areas. During the early Ordovician there was uplift with many delta formations. There was a hiatus between the Ordovician and the Silurian with very little sediment until the mid Silurian when there may have been a sea level rise bringing in fresh layers of mud. In this area there is also evidence of later periods of arid conditions with red beds and also limestones from clear seas.

Our first stop, near the tunnel, was to look at the Maladeta granites intruded in an elongate oval trending East West 275 – 300Ma ago into the Pyrenees at the time of the Hercynian Orogeny. We looked at granite boulders with slickensides (much sensuous stroking), later intrusions showing flow banding, veins with quartz and feldspars and xenoliths – these were very easy to see and gave a real sense of the country rock having fallen in and being gradually absorbed – they showed up as darker areas with extra ferro-magnesium minerals.

The second stop was back along the road to look at large zoned garnets. A Big Wow factor – garnets about 30 mm across with zones clearly visible. As the granites were intruded they formed fluids in hydrothermal zones which then caused reactivation of various minerals. As the conditions changed slightly so the garnets were crystallised with slightly different zones of mineralisation which still exist today millions of years later.

For our next stop we changed our focus from the small to the large – 2024m above sea level (as tracked by two GPS sets) we were looking at what had been a glaciated dome of ice between two glaciers. It had been uplifted and incised by rivers and streams, some of which are still active. A truly impressive sight giving a real feel for some of the forces involved in shaping the landscape.

Back to the smaller scale for our next three stops. Glacial moraine for the first and evidence for multiphase deformation in the next two. The lower Palaeozoic rocks were highly deformed by the Hercynian orogeny and display in the field a variety of complex deformation features caused by relatively uncompetent deflection of slaty cleavage against the more competent carbonate rocks. Paul was excited by a piece of rock which showed 3 phases of compression. The rock had a slaty cleavage with a set of crinkles which makes it into a phyllite and another set of crinkles in another direction which indicates yet another phase of deformation. By looking carefully at the small scale structure of the rocks the detail of the larger canvas is painted in. We were also able to put pictures to the words that we read in the text books with excellent examples of carbonate and ptygmatic folds. In a road cutting further down the valley we saw different varieties of tension and extension features including boudinage and evidence of flow banding. This area has been affected by two main phases of orogeny and the rocks reflect many phases of deformation.

We finished the day by thinking in the large scale about the Noguera zone ready for the geology for the rest of the trip. At this point, at the end of a long and exciting day, I got confused. Reading my notes all this time later makes no sense to me now but I am sure that all will be made clear about thrust zones, duplex beds and decollment zones in the write ups from other people. It was a wonderful day because it was so different to anything I had seen before and set the scene for the rest of the week.

Today was to be our Triassic day, and it dawned characteristically sunny and hot.

Our first exposure was just a short walk from the hotel and consisted of the Keuper (Upper Triassic) Pont De Suert Formation. The beds here are near vertical and are composed of re-crystallized and deformed gypsum intercalated with red shales. Paul interpreted the depositional environment as one of sea water refluxing into shallow lagoons of high salinity and with flourishing algal mats. It could be seen that the beds had high porosity, and Paul demonstrated that hydrocarbons could be smelt on broken samples. Considerable deformation of the gypsum could be seen, with flow structures and boudinage present. The deformation has been attributed to the Alpine Orogeny.

Our next stop was a roadside exposure of Triassic Red Beds, which here consisted of current bedded very fine sand with mica and quartz pebbles. The fact that these beds are inverted could be demonstrated with bottom structures, graded bedding and truncated current bedding. Again secondary porosity could be seen due to the weathering out of calcretes and mud clasts.

After a view stop to look at the phyllite basement overlying Permian conglomerates we moved on to look at some intermediate ophite volcanics. In these the pyroxene and feldspars had crystallized at the same time forming interesting crystal structures with pyroxene centres and radiating plagioclase.

Paul had promised that our final stop at Erill Castell would be exciting. Little did he know!

After a precipitous climb in the minibuses up a rocky mountain track we had a problem turning the vans round. One of our drivers (who will be nameless) decided to achieve it by driving flat out in reverse and throwing the van onto full lock. The manoeuvre was completed about a foot in front of Paul’s van, and the look on his face had to be seen to be believed!

It was well worth the effort though. At our first exposure in near vertical beds an unconformity between the Lower Palaeozoic basement and Middle Carboniferous could be seen with a coarse breccia at the base of the Carboniferous. Moving along the section we passed into pale pyroclastic deposits with large angular clasts. There was some discussion regarding these, ash falls? Pyroclastic flows? Falling into water? Next in line were river channel deposits with carbonaceous sand and shale overbank sediments, coals, log jams and well preserved Carboniferous plant remains. Exciting stuff! Just to finish off those who braved the climb up to the castle could examine basalts of doubtful age.

A great day!

Today, we were to up temporary roots and move from Pont de Suert to Tremp. In fine weather and having achieved the packing in of (too much?) luggage, we set off. Firstly, to the north to view some rocks in a quarry which were supposed to show ophitic texture. This is where feldspars have recrystallised as radial laths within a pyroxene crystal. Some thought they found the state, others weren’t convinced. No matter, it served to spend time usefully until the shops opened so we could assemble, without a great deal of dither, the necessary for lunch!

On leaving Pont de Suert for the second time, it was some relief to our drivers not to have to negotiate mountain tracks, the road being good. We moved across country to a spot near Perves and examined from across the valley an outcrop of Oligocene Collegiate conglomerates, these being overlain by some more massive material with some folding. The exposure was about 650 m over about 150m sandy units lying on basement. Sheets of conglomerate showed low angle cross bedding and appeared to come out as alluvial flows. There was coarsening up from quite fine material to some large blocks. This area is thought to have been the infilling of an old valley by a braided system.

We then proceeded to and through Tremp, with a fleeting glimpse of the next hotel. We followed the valley of the Noguera Pallaresa, another river of mountain origin, destined to join the Ebro. As such it had moments of rushing, some braiding and gentle and broadening flow. There was plenty of geology to be seen in passing, including a dramatic gorge. We were able to see the extent and relative flatness of the Tremp basin as we went.

Near to Fontilonga we came to some rising ground and stopped for lunch on a small promontory which gave us a splendid all round view of the landscape. To the south, over a field blushed with poppies, were hills more rounded than in the high Pyrenees, beyond these Paul told us lies the Sierra Marginales, the foothills of the Pyrenees, after which lies the Ebro basin. To the west at some distance across the river we could see the Monsec Thrust against the skyline.

After a leisurely lunch, we tracked back a hundred metres or so along the road to study a splendid roadside section. There was at the top a layer of very well weathered sandy material thought possibly to be an oxidised thrust. Under this were gently dipping massive competent sandstones. Below this and obscuring the face were heaps of loose sand layers. Marks and evidence of road surface repair suggested frequent falls of the harder stuff. Farther down the road more muddy material appeared as well as obvious channel fill. These are thought to be meandering river channel fills with one particular one, according to Paul, could be an oxbow infill.

A short ride further down the road where there was a bend the rocks were more broken with muddy infills in which some fossils were found. We then came across a stunning example of ripple marks, well exposed. These were still sandstones and with some trace fossils and forams being found suggested a terrestrial offshore marine deposit either tidal or as the ripple marks showed oscillation perhaps a long shore drift deposition.

The last thing looked at was a rocky block in which were found plenty of bivalves

Thence, the longish ride back to Tremp to take up residence for a few days of further geowonders!

John Wade.

We left Tremp on a beautiful, sunny morning and headed east. The road we wanted to take was closed for road repairs, so we drove up to the pretty village of Abella de la Concha. Here we had magnificent views. We were on the north-east side of the Tremp Basin. To the south was the Monsec Thrust sheet that we had driven through the day before. This thrust sheet had been carried forward south and upward, and we were standing in the village with the thrust sheet somewhere at depth below us. We were standing right up against the Boixels Thrust sheet. Below us we could see the Upper Cretaceous beds, and Tertiary beds of the Tremp Formation banked up against the thrust and overturned.

As we walked along under the vertical rocks, we could see and touch the thrust fault. The evidence for this is the flat, smooth surface with striations, and deformation of the beds underneath. The breccia was very thin on the thrust fault at this point, but further along we saw three metres of deformed shales, vertical and dipping to the south. Above the fault, the vertical Santonia limestone forms a hanging wall anticline. This is known as the San Cornelli Anticline. We looked across to the beds dipping to the north at the north end of the basin.

The Monsec Thrust is pushing south, and the Boixels Thrust is riding over it, the lubricant being the shales. The Tremp Basin is a “piggy-back” basin riding between the two thrusts. It was awe-inspiring to think of the great forces at work as Spain pushed into the rest of Europe.

We looked at the views, watched Griffon vultures circling overhead, and then drove to Isona to have a refreshment stop. We visited the museum to see a geological exhibition including dinosaurs.

While the road works were suspended for lunch, we were able to squeeze past the machinery (only just!) and drive to a viewpoint where we had a very good overview of the San Cornelli Anticline. This made the complicated geology a lot clearer.

We spent the rest of the day looking at some of the Tremp Basin deposits. Further along the road, at Faidella Pass, we examined the gently dipping Santonian Limestone. In one direction these deep-water marine limestones became more marly, and in the other direction, were overlain by sandstones containing plant debris, and cemented with calcareous cement indicating shallowing conditions. At our next stop, back along the road, we found tidal channels with big open folds, which have been interpreted as dune structures, 50-60 metres deep, similar to those seen in the Folkestone Beds in the North Sea. Here we could see large-scale cross bedding, poorly sorted gravels and sands.

We had a picnic lunch in the sunshine and listened to nightingales singing from every tree. Then, to the delight of some of our party, we went to look at some fossiliferous rocks. We found calcareous algae, and rudists. These are large conical bivalves, where one valve acts as a lid, looking rather like an ice cream cone with a lid. We saw some with lids. These specialised bivalves did not survive the Cretaceous, and were confined to warm limestone seas.

The final visit of the day was a visit to Orca Castle, where energetic members of the party climbed to the top, while others took a more gentle stroll, to see the steeply dipping Aren Sandstone interbedded with finer grained rocks. This represents a marine slope with small submarine erosive channels. There was some discussion about sequence stratigraphy, and whether this represents time or sediment lines. This brought us to the end of a very exciting day’s geology.

This was the day I’d been waiting for. Up until now we had seen the most amazing structures form the Pyreneneen Thrust belt but now we had a chance to examine some of the rocks from the piggy-back Tremp Basin between the Montisec and Boixols thrusts. So we climbed up the road running to the west of Tremp and immersed ourselves in the Lower Tertiary.

Oysters were definitely the ‘dish of the day’ at the next stop, a road-cutting further up the hill. No-one could fail to find them. Big ones, little ones, some in blocks and at least 2 different varieties. Here we stopped at a viewpoint where we could see clearly beds of alternating clays and sandstones in the neighbouring hillside. Paul described these as ‘para sequences’ of rising and falling sea-level, possibly related to basin subsidence. As we walked up the section others examined the structures in the sandstones, finding lags at the base and dewatering structures. I had my nose to the ground and found occasional patches with gastropods amongst the oyster-rich clays and came upon the horizon where Paul found the Alveolina forams. I also found another of Eddie’s Orbitolites. Paul S. gave me an oyster encrusted with a serpulid tubeworm which turned out to have a most interesting bryozoan encrusting it as well. A quick glance by Paul Taylor, a specialist at the Natural History Museum, got him very excited, as it appears to be the earliest known record of the genus Electra. This will need more investigating and is definitely one for the NHM collections. Thank-you Paul S! Some of the oysters may prove interesting enough for the collections as well.

As we approached the top of the Montllobar Pass the lithology changed to purply red: we were now out of the marine Palaeocene and into the terrestrial Eocene Montañana Group. With eye-of-faith Paul made us agree we were seeing long root horizons where the red had become de-oxidised. Rose pulled off another coup by finding an excellent piece of horse-tail ‘wood’ to prove Paul’s point.

Our next stop, on the other side of the pass, was a view point where we could look north to the snowy peaks of the central Pyrenees. In the baking heat it was hard to believe we were standing amongst falling snow only 4 days before.

Finally we viewed a channel sequence in the middle of the Montañana Group, much loved by the oilmen, as, with its high porosity, it made a good reservoir. Paul told us that one of his students described the trough cross-bedding as smiley beds – a very good description!

Back to Tremp for lunch and siesta to conserve our energies for the massive dinner at Casa Lola in the next village. And what a feast! Course after course of wonderful fresh food including local wild mushrooms. Thanks to Gill we could wash it down with good Spanish bubbly. Thanks Paul for another excellent day and excellent dinner choice. Thanks Wilf for organising the bubbly and thanks Gill for providing the excuse!

The Day of the Turbidites - a traverse from Tremp to Boltaña via - Puente de Montañana - Benabarre - Laguarres - La Puebla de Roda - Torre la Ribera - Egéa - Campo - Foradada del Toscar - Ainsa

We all emerged after the previous night's festivities at Casa Lola and packed our bags ready for the long drive to Boltaña. From Tremp, we retraced the previous day's trip over the Coll de Montlabasto to Puente de Montañana on the Naguera Ribagorçana where we left Cataluña and entered Aragón.

After a long drive across the Sierra del Castillo de Laguarres with magnificent views of the mountains and up the valley of the Rio Isábena we arrived at our first stop, just outside La Puebla de Roda. We turned off the main road to a good vantage point looking out over the valley. On the west side of the valley we could see massive turbidite fans created in the Eocene by flows from the east into deep waters in the west. Oil companies have shown a great interest in this area; they have examined many of the channels as type example for the North Sea sands.

After leaving, we travelled a short distance where we stopped to fill up the minibuses with fuel and us with ice cream, etc.

The next stop was at Villacarli in the Laval valley, where we looked back south eastwards to observe a landscape that had seen continuous sedimentation through an unconformity. The hills showed the Eocene lying on top of the Palaeocene - a sequence boundary between terrestrial Montañana (top) and Agur (beneath).

Nearby, there was a fine example of a hanging wall anticline, where the Cretaceous limestone had been brought over the Tertiary turbidites. The rills and crests gave this the typical badlands weathering.

The journey and exploring the sites had taken all morning, so we found a small road off the main road near Foradada del Toscar, where we could park the buses and sit down to lunch in the shade of some trees.

After we had rested, we continued our drive westward, passing new road cuttings that had exposed turbidites of mass movement downwards in water. This road was in the process of being rebuilt with new cuttings and tunnels to smooth out the old bends. Just before one of the new tunnels we turned off on the old road where we saw a major section through the massive flow. There were examples where the sediment on the slope had collapsed to form a high-speed, turbid, current. There was also convolute bedding, ripple marks and many more features.

After leaving this exposure by the old road, we drove onto Ainsa Quarry, which was billed as the best quarry in the world. The quarry displayed a large number of features that were difficult to explain and had us all putting up different hypotheses as to how they had formed. There were examples of folding, surrounded by no folding; mud volcanoes; slumping of semi-consolidated material. There were fossils, rock types and sediments that seemed to be contradictory; beds with huge boulders of flint, diorite, mudstones, granites, and limestone and shale of Mesozoic origin but microfossils that date it as Tertiary.

Rivers and storm beaches give a significant amount of sorting. Many of the fossils ware non-marine, with 90% oyster (estuarine). There are banks of benthomic forms and offshore muds with bivalve and gastropod traces.

Whatever the trigger, we were observing a whole area where the terrestrial side margin had collapsed. As you can see there was much to ponder in such a short visit. We met a PhD student and her research assistant who were surveying the quarry and area around and planned to be there for six months.

As a final remark to the field trip, Paul Grant encouraged us on the purpose of fieldwork, which I paraphrase: - look at anything you can see - your investigation is as good as anyone else's but be self-critical about your conclusions. Think about facts that may destroy your arguments - but not so much as never to make a decision.

After leaving the quarry we travelled beyond Boltaña where we were to stay the night, to one final stop to look at the Boltaña fold. This is an asymmetric anti-form pushed from east to west. The thrust had not quite penetrated the surface as we were standing at the easternmost extent of a thrust and nappe structure. Technically, material has been "squished" to the south and west as Spain subducted below Europe.

Finally, all our thanks to the drivers for taking us all safely though some very demanding roads and not so roads. The next day was to be the drive to Pau Airport across the Pyrenees via the Tunnel de Bielsa in what promised to be very good weather - a bit different from the first day from Pau to el Pont de Suert.

The big thank you for our leaders was to come the following day.

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