Selected Articles from Issue Number 7/5 October 2000

Building Stones Walk around Canary Wharf

Led by Eric Robinson 20th July 2000

Photographs of this field trip are in the Photo Gallery.

We gathered on the East platform of the Canary Wharf Docklands Railway station where Eric Robinson greeted us with his usual infectious enthusiasm. Eric set the scene by telling us that Canary Wharf was conceived in the late 1980's and the first phase of building was constructed mainly by the pre-fabricated method for quick construction. The first phase 1993-1997, has an American feel with some buildings having showy stone facings at ground level and artificial "rubbish" stone there on up.

The stones used in the first phase show what was fashionable and economic at the time with predominantly granites from Finland and other Scandinavian countries as well as from Spain and Portugal. As the years went on more Brazilian and Indian granites were used, as they were able to undercut the European price, sadly in the case of India by using cheap child labour.

LOCATION 1

The recurring theme for the walk was to be set here in the station where we saw several rocks from far and wide which we would later see in different forms and juxtapositions. The first location was the platform itself. The seats were of red Finnish granite with large feldspar crystals. The strong foliation and slightly violet quartz crystals indicated that the rock had been metamorphosed. The same Precambrian rock was used for the backs of the seats and for paving but here the rock had been flame textured and looked very different. The finish endowed non-slip properties.

Above the Finnish granite there was a pale Limestone featuring belemnites, ammonites, nautiloids and sponges. The sponges were made obvious by iron staining. This French limestone of late Jurassic/early Cretaceous age cropped up many times during the walk, sometimes more highly polished than here. Looking across the platform darkish brown sandstone with structure could be seen above the limestone. This German sandstone from the Wurtenburg area was better seen at the third location in the South Colonnade.

LOCATION 2

We descended the stairs from the platform observing the French Limestone in the stairwell walls and arrived at the star on the floor of the South Colonnade. It looked very similar to those expensive Italian tables inlaid with different marbles but using granite and on a grander scale. The varieties of granites included Larvikite from Norway, dark red Indian granite, grey Spanish granite and brown Dakota Mahogany metamorphosed granite.

LOCATION 3

Towards Cabot Square we were able to get closer to the German sandstone and marvel not only at the bedding and cross bedding but most of all at the iron-stained ridges. As the sandstone "drinks" the iron is mobilised and migrates producing the figured effect. Other rocks seen in this area were Lake District grey/green slates of the Borrowdale volcanics. These slates were hot ash flows and show graded bedding, plastic flow and sedimentary structures.

LOCATION 4

Across the road at 10 Cabot Place the bottom course of the building was faced by brown orbicular granite called Baltic Brown. This ancient Finnish rock (1200 Ma old) from the Katla quarry near the Finnish-Russian border had large rounded feldspars with inclusions in layers. Some feldspars had been corroded and grey-green crystals deposited round the orbs. This rock is one of the group of Rapakivi granites. Occasional xenoliths, or heathens, could be seen within the granite giving evidence that this rock was molten and ate isolated pieces of the country rock that it was being intruded into. Above the Baltic Brown an artificial stone was used, an example of the American style of building. What a sad characterless effect compared to a real stone finish!

LOCATION 5

We walked towards the West India Quay and Eric pointed out some red orbicular granite. Some of the Jessops' warehouses across the dock have been turned into apartments; others are in the process of being renovated. John mentioned that he visited these warehouses when they were still being used for their original function. The floors are of fireproof iron to cope with the heavy merchandise from the West Indies e.g. sugar. The name Canary Wharf refers to the banana trade with the Canaries. We examined the round structure here the upper part of which is faced with a limey sandstone with the bedding nature of Mediterranean Tertiary limestone. The light pink granite below is from northern Spain. It is a two-mica granite whose feldspars have fuzzy boundaries because this rock has been affected by the Alpine orogeny.

LOCATION 6

The Credit Suisse building, 15 Cabot Square has a blue dense gabbro/diorite facing with swirls of white feldspar, which was probably a mixed melt. As we walked round the building Eric pointed out a pegmatitic vein within the granite paving. Further round the building we saw more gabbro. The highly polished surface showed swirls and metamorphic banding and elongated grey/green feldspars. New coppery coloured minerals could be seen. Brazil is the possible origin for this rock.

LOCATION 7

The grandeur of the arch guarding the entrance to the West India Dock was spoilt by the artificial material used. The inscription proudly declared that the Dock was opened by William Pitt the Younger on July 12th 1802. Round the corner the plinth of the statue of Robert Milligan, a merchant who invested in the West Indian trade was of the even-grained Peterhead granite from the Aberdeen coast. The cobbles here are a mixture of granite, basalt and some slag. The Barclays building was briefly mentioned as being in ghastly bad taste but some of the other buildings were quite interesting e.g. the Egyptian style building and the old Customs Office with its wooden Ionic columns. As we crossed the quay we saw some of the original York Stone paving and the newer granite kerbing. We crossed over the bridge and could see two ships in the quay, one being the Robin a coaster from the First World War era.

LOCATION 8

The walls of the building housing the Canary Wharf Health Club, 1-5 Cabot Square, exhibited more of the French limestone with belemnites that we first saw in the station. Below the limestone the basic rock with swirls was used.

LOCATION 9

The French limestone was used again in the building opposite, 25 Cabot Square. Here a deep red very large-grained Finnish Gneiss was used with it. This beautiful rock showed the stress it had been through by its foliated texture and the way the cleavage planes of the feldspars stood out. The same gneiss was used in the paving but there it had a roughened texture to give a non-slip finish.

LOCATION 10

We admired the water cascades as we went to the centre of the square. The circular surround of the central fountain was faced with the even-grained Blaubrun Norwegian granodiorite that showed some inclusions of dark slatey rock. The surrounding ledges were of a spectacular Brazilian metamorphic granitic rock showing off some magnificent contorted banding. This mostly salmon pink rock comes from the Pre-Cambrian shield of Brazil.

LOCATION 11

We crossed over to 10 south Colonnade and examined the pale "marble" stone facing. This was Vermont "marble" from the U.S.A. an impure sandy limestone deformed by pressure and heat. Below the "marble" was a layer of a Brazilian rock. The paving here was of charcoal-grey south Lake District slate showing the radiating stresses in the split slabs.

LOCATION 12

The Canary Wharf Tower, One Canada Square was our next target. Although the outside of the building is mostly of glass the reception area has some spectacular rocks. The reception desk itself was of a polished black marble from Spain showing remains of brachiopods. The high walls were clad with a deep clove-red Spanish marble with tension gashes filled with calcite. It reminded Eric of a microscope slide showing Cirrhosis of the liver! Another marble, green this time, covered the sidewalls. The floor was of grey Italian marble.

Before we dispersed Eric told us of the new generation of rocks being used in the newer phases e.g. in Heron Quay which indicates many more building stones walks are needed to see the full variety of rocks here. I was delighted to see such a variety of rocks many of which I had never seen before.

Field Trip to Northern Spain 29th July—5th August 2000 Part 1

Led by Professor Andy Gale

Photographs of this field trip are in the Photo Gallery.

As our GO plane plunged through the clouds we thought that Bilbao was about to live up to its reputation of the rainy city. However, about three hours later, off we set to the coast in blazing sunshine, along with the rest of Bilbao. It was now post-siesta time on a bank holiday weekend and the beach of Sopelana, with restricted parking, was groaning under the weight. In the event this was the only traffic jam we were to encounter the whole week. But it was worth the wait: the rocks at the back of the beach were stunning. They were almost vertical, alternating limestones and marls of Late Maastrichtian age. Our leader, Andy Gale has had a PhD student working at this location. The idea is to photograph the cliff section and to digitise the image. From this it should be possible to work out the length of time taken for the deposition of the sequence. Andy believes that the rhythmic alteration of limestone and marl is related to planetary motion as described by Milutin Milankovitch in the 1930s. These cycles have become known as Milankovitch cycles, the predominant one being the wobble of the earth’s axis, each cycle lasting for approximately 20,000 years.

We set off along the beach in our boots amongst the bare-footed, bikini-clad crowds and immediately we came to magnificent examples of the trace fossil Zoophycos. This trace was made by a very thorough burrower who systematically searched an area before going to a second level and beginning again. Such an intensive search is thought to be diagnostic of deep-water animals (S260/S263) although Andy seemed to think Zoophycos was not necessarily restricted to deep water. It is, however, likely to relate to areas where food within the sediment is scarce.

Next we headed for a patch of red rocks further along the beach. These were full of gypsum and are of Triassic age. Further inland salt has been mined from diapirs of Triassic salt that have punched up through the overlying sediments. Right beside the red rocks was a small patch of black igneous rock . Andy and Paul reckoned it was probably a dyke of altered dolerite which had been pushed up along with the Triassic rocks and may even be older than them.

The highlight of the afternoon for me came from a rather scrappy exposure away from this spectacular bay, behind the swimming pool, above the restaurant. This was the famous KT boundary dated at 65 million years old. I have seen the junction between the Cretaceous and Tertiary rocks in several places in the SE of England, including our trip last October down the Pinner Chalk Mines. In the south of England, though, we are missing the top Cretaceous and the lowest Tertiary. Here, in northern Spain, as in Umbria in Italy, the section is thought to be continuous. So Andy scrambled up the wall and sat on the contact, his finger pointing to the hole where numerous geologists had removed clay for sampling. They were looking for the famous iridium layer, thought to be deposited by the fall of debris after the massive meteorite hit the Gulf of Mexico at the end of the Cretaceous. This, then, was the point where a high proportion of species was thought to have died out. Andy demonstrated that no ammonites have been found in the final meter of clay: they died out by his right foot. The debate continues.

This was not an afternoon I would have wanted to miss. But I almost did. My handbag had been spirited off me by a couple of con men at the airport and I was all set to spend the rest of the afternoon in the police station. First I thought I’d better cancel the credit cards so a hot line to England was set up from my bedroom. I was just clinching the deal on the Visa card when the receptionist came in: Europacar had found the handbag in their parking lot where it had gone missing. I was so overjoyed that the passports and the Visa card were still there, I didn’t even ask about the cash. I only found out about that after our trip to the seaside. Well, it’s only money and there’s always the insurance….

On Sunday, we left Bilbao travelling SW over the Lower Cretaceous sediments of the river valley, through Balmaseda towards Puentedey. Our aim
was to try to date the sediments of the Upper Cretaceous of Cenomanian and Turonian age with identified fossils.

The vista opened out to resemble a wide amphitheatre surrounded by a series of dipping escarpments extending into the distance. Andy explained that the Lower Cretaceous limestone sediments had been infiltrated with Triassic salt domes rising from below, and salt had been mined in the area since early times. The thick sediments we could clearly see capping the escarpments were the Upper Cretaceous limestones.

Our first stop was above Cueva where we had a wonderful panoramic view of the area we planned to investigate. We noted the thick marl sequence in the valley before going on to the actual “Cueva” situated within the scarp of the Cueva Formation of the Upper Turonian limestones. Here we saw pictures of the caves and could hear the rushing water but were unable to enter the caves due to their active erosion.

Our next locality was at a site further down in the sequence, but still within the Turonian, below the thick scarp limestones capping the hill. The sediments displayed here in a road cutting revealed well-preserved echinoids, a mussel (Modiolus) and one ammonite, although sadly this was probably not preserved well enough for identification.

We then drove to Puenteday, near the base of the sequence, where Andy's previous research had revealed a large area of rudist bivalves. These are known to have become extinct at the end of the Cretaceous and also thought to have been diagnostic of shallow water, forming large reefal colonies. Moving on up the sequence, along the road cutting, still in the Cenomanian, we found well-preserved orbitoline foraminifera, the modern equivalents of which live in shallow water. Further on still we were able to discover oysters (Rastellum and Rhynchostrea) and a regular echinoid that Andy was interested to keep, but although we looked hard, none of the ammonites required for dating the sediments.

We followed the sequence up along a disused railway cutting on the other side of the road where we found Inoceramus bivalve fossils, and finished at another new road cutting on a bend which oozed echinoids of a different species. According to the handout, we were now in the Puentedey Formation of Turonian age although, on this occasion, we failed to find the ammonites to prove it.

On the third day we travelled to the coast near Barrika, which is about 20 km north of Bilbao. From the top of the cliff we could see the sandy bay with lines of rock going out to sea from the base of the cliff, although on closer inspection it was evident that there had been considerable folding.

On the way down the path there was considerable evidence of relatively new tension cracks on the steep slopes, indicating future rock falls.

This was an area of Cretaceous turbidites that are created by turbulent and fast currents, which gradually drop their load as the current slackens. These displayed some of the fascinating formations of turbidites with sorted and graded beds. There were truncated folds with turbidite flows on the base.

One remarkable formation was the view of a syncline dipping out to sea, which was filled with sand. The pointed rocks coming out of the sand showing the angle of dip.

In the cliff face it was possible to make out an olisthostrome, a fault-controlled slope that is probably formed by a submarine gravity-slide. There were a huge variety of materials in this melange of local and exotic materials. A simple description is that unstable sediment suddenly goes "whoosh" below the sea.

At this point we had a demonstration of how to measure the height of the slump. Andy reminded us of the calculation:

1. Pace out the distance (36 paces)

2. Convert to metres (0.7m per pace) to give the distance (25.2m)

3. With a slope of 45⁰, sine theta (45) = 0.707

4. 0.707 x 25.2m = 17.8m - the height.

The cliffs exhibited many other features such as ashfalls or pyroclastic flow and isoclinal folding formed by the Iberian plate crashing into Europe.

At one point along the cliffs there were fine examples of sole marks - casts at the bottom of a bed, formed as a result of infilling of depressions by coarser sediments.

After a very hot morning we retired to lunch at Solaetxe café near the university, where we met one of Andy's colleagues and had welcome refreshments.

After lunch we travelled along the coast to bays below a lighthouse near Sopelana. We descended into Playa de Gorrondatxe where there was a very good example of a raised beach formed of beach-rock. The beach-rock can be formed very quickly as relative sea level falls, and can be dated by its contents, held together in cement of calcium carbonate or silica. [Andy described an example where a recent beach has been dated using coca cola bottles that had been trapped in the cement.]

There was evidence of numulites, which were abundant in Eocene times in southern Europe. They were deposited by the flushing down into sea basins.

There were examples of Lower Eocene turbidites which had soles (mud sediments - turbidity current deposits). The sand makes a perfect replica, then hardens to produce natural positive casts - soles - depending on the nature of the current. Some of the turbidites are regular indicating that they are distal.

As along other places this day, there were many examples of flysh - deep water interbedded muddy and sandy sediments deposited by turbidity currents. These are derived from the erosion of rising Pyrenees mountains.

For those interested in the local flora, there were some interesting examples of sea holly and rock samphyre in this bay, which were protected.

At the furthest point reached along this bay there were many excellent examples of forums within sandstone, e.g. an irregular echinoid trace with sanitary drain, numulites size of 50p piece and calcareous algae.

After climbing out of the bay, some the steep way and some the easier way, we walked back along the cliff top to the lighthouse where the cars were parked. Andy was the only one with enough energy to go down into another bay, and could be seen as a distant figure a long way below us. We all appreciated another excellent day looking at the geological formations along the coast of northern Spain.

-oOo-

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Last modified: January 27, 2002