Our pilot archaeological project is now coming to end, on the fieldwork side. Dating specialist Professor Geoff Duller arrived on Tuesday night and for four days the team has been busy helping with the collection of sand samples for luminescence dating. I’ll explain this dating method shortly, but first let’s look at the process of extracting the samples from the ground.

Geoff and I discuss where to collect the samples to ensure we’re targeting key archaeological horizons – like the Sangoan – and the sediments above and below to help bracket the age of the artefacts. A tube of plastic or steel with a bevelled edge is hammered into the section face. The plastic tubes are used on the soft sands that occur at the top of the Asokrochona sequence and in much of the coastal cliff sequence at the former Nautical College. The steel tubes are reserved for the hard older deposits at Asokrochona and the base of the Nautical College.

Geoff brought a dense rubber mallet but it wasn’t up to the job of driving the steel into the key Sangoan deposits at either site. We needed something heavy-duty like a sledge-hammer.

Geoff using the cheap hammer on a steel tube in the Asokrochona formation

Geoff using the cheap hammer on a steel tube in the Asokrochona formation

Siaw and Seth (our driver) sped off to find a sledge hammer in the local shops. They returned with a foot-long iron-tipped miniature sledge-hammer that cost less than £5 ($7.50). If a bargain is too good to be true then it probably is and this tool was no exception. Within minutes the head had come off. We had a good laugh – followed by a few choice words about the poor quality of manufacture. But, the head was tapped back on and eventually, with careful pounding, the tube was well into the Asokrochona Formation – our key deposit at the site because of its concentration of large tools.

Geoff’s first day on site was a shock to his system. The baking heat was joined with odorous wafts of excrement and food waste drifting over from the village across the tracks. I recall lasting about two hours on my first day at Asokrochona before feeling dizzy from the heat. Geoff was right on schedule with a wobble mid-morning followed by a recuperative spell of shade in the car.

We were on a tight schedule this final week and prolonged wobbling from any team member would not be good. Part of the time pressure came from a planned site visit by postgraduate students at the University of Ghana led by the well-respected archaeologist Professor James Anquandah. The Professor had last been here in 1964 and was keen to see that new work was underway at the site to address the vexing issue of its age. The visit would take place Thursday, our last field day at both sites.

Sections still needed drawing and Geoff and I had offered to give a joint presentation on Friday to the Archaeology Department and invited guests from the University and the Museum and Monuments Board. We worked on the presentation long into the night on Wednesday and Thursday. In addition, I had to finish the analysis of the artefacts we’ve collected because that had to be handed over to the Museum on Friday, and Geoff would need an export permit for the dating samples.

The final twist of the screw came from the dating sampling process – it’s slow.5 1 Geoff with the portable gamma ray dosimeter at Asokrochona

After a sampling tube has been extracted and carefully packaged, then the background radiation has to be measured using a portable gamma ray dosimeter. Geoff will calculate when the sands grains were last exposed to sunlight before being buried. Exposure to modern sunlight just for a few seconds could spoil the results by resetting the electron traps in the individual grains of quartz sand. That would be VERY BAD, especially after the months of effort it’s taken to get to this final stage of the fieldwork.

As Geoff explained to the student visitors, the electron traps act like a battery that’s being charged in your phone or laptop. The length of time it took to fill the electron traps can be calculated to give an age since the last exposure and that calculation involves the dosimetry readings from the sample site. If your phone battery is fully charged you just can’t add any more power however long you leave it being charged. The same happens to quartz grains and with this technique (called Optically Stimulated Luminescence) ‘saturation’ is often reached after 150,000 years or so.

That time span will be fine for dating the recent upper part of the Asokrochona sequence, and I suspect for most of the Nautical College deposits, but not for the lower deposits with Sangoan artefacts. If that’s the case, then Geoff will switch to a newer more experimental version of the technique called Thermally-Transferred Optically Stimulated Luminescence (TT-OSL). I won’t explain how this works, other than to say it measures a more slowly growing signal in the quartz, which means the age range can be extended greatly. Geoff has applied it with some success to another site we worked on together – Kalambo Falls, Zambia. There it extended the age range back to 500,000 years ago and so it should help us get a fix on the earliest part of the Asokrochona record.

It’s now time for patience on my part as the analytical work will take some months to complete, back in the lab at Aberystwyth University.

We had planned to collect a total of six dating samples from each site, which was feasible if all went smoothly. It didn’t. Too many artefacts in the sediment prevented the collection of second sample from the Sangoan at Asokrochona – which was a disappointment. A steel tube couldn’t be hammered in because of the density of artefacts (which I added to my collection of pieces to analyse by Friday).

Site visit - Professor Anquandah is to the left of Geoff with students

Site visit – Professor Anquandah is to the left of Geoff with students

In addition, the Departmental site visit ended up taking much longer than planned because of the sheer interest of the students and Professor Anquandah in the project. One student helpfully suggested that we work at night to reduce the risk of light contamination. It turned out to be a prophetic suggestion …

Collecting a luminescence sample from near the top of the coastal section

Collecting a luminescence sample from near the top of the coastal section

It was midday when we finally arrived at the Nautical College with all the sampling still to do. We would in fact finish in the dark with the lights of Tema port glowing to the east.

George using dosimeter near base of coastal cliff section

George using dosimeter near base of coastal cliff section

As so often happens on archaeological digs the best finds came in the final hours of the project. While waiting for a dosimetry session to end, I went for a stroll with George Anorchie, our officer from the Museum.  We headed towards the very last remnants of the Nungua Formation (Middle Stone Age) that survive on this stretch. Here we saw a large white quartz artefact emerging from the deposit. It turned out to be the longest flake from the site and joined a collection of other large pieces from cobbles overlying bedrock. Is this more Sangoan?

Last find of the project - large flake from base of coastal cliff sequence

Last find of the project – large flake from base of coastal cliff sequence

Passing visitors share our big-flake excitement!

Passing visitors share our big-flake excitement!

Then Geoff and I walked in the other direction and, as the light faded, he noticed a deposit of clayey sand beneath the cobbles – something we hadn’t seen in the main section of the cliff. Out came the last of the steel tubes and by the time we left after the dosimetry readings were made it was definitely dark. I don’t think nocturnal archaeology will catch on, but when pushed by deadlines, needs must.

The Port of Tema glows in the distance, lights of ships shine in the dark as our nocturnal archaeoology draws to a close

The Port of Tema glows in the distance, lights of ships shine in the dark as our nocturnal archaeoology draws to a close

I’ll miss that beach. Despite all the flotsam washed ashore from the shipping trade – and the excrement deposited daily by visitors (yes, here too) – the cooling breeze made it a comfortable place to work. And of course the artefacts were intriguing for being dispersed rather than concentrated as at Asokrochona.

I’ll be back with more posts once we have some results on the dates. It may be a while, so if you don’t want to keep checking back you might want to ‘Follow’ so you’ll receive a notification when a new post is published.

Thank you for reading.

Advertisements
4 1 After the rains, Lake Bosumptwi

Lake Bosumptwi after the rains

Hard labour over for a few days, I decided to leave Accra for the weekend to visit a beauty spot five or so hours to the northwest. Lake Bosumptwi is on the tourist trail, but for me it commands a special reverence. Here in the hills of the Ashanti heartland a meteor struck the earth roughly one million years ago. The crater, which is 35 km in circumference, is today a deep lake. It’s the lake in its craggy setting that tourists come to see and it is a sacred place for the local people. Fishermen are not allowed by local custom to use canoes and instead ply their trade on flat log platforms. I’m told that there’s an annual sacrifice of cattle that turns the water red, but I’m here to celebrate what lies on the bottom of the lake.

Fisherman diving for fish in Lake Bosumptwi

Fisherman diving for fish in Lake Bosumptwi

Over millennia, sediment has been deposited gradually in the still waters forming a muddy archive of climate change that spans the past 520,000 years. The pollen preserved in the sediments reflects changes in the local vegetation, which in turn tells us about wider changes in rainfall linked to global glacial cycles. The importance of the Bosumptwi record is that it shows that West Africa was, for most of this time, a land of savannah woodlands and grasslands and not the forests we see today. There were six relatively short wet phases with forest cover and the rest of the time was very different from the habitats we see now. If we can date the coastal sites of Asokrochona and the (former) Naval College sediments with some precision, then maybe we can link them to the Bosumptwi climatic record. I’d like to know what kind of surroundings those folks lived in, what might have been the opportunities in terms of plant and animal resources as well as stresses posed by the particular habitats. Archaeologists working on the Stone Age in West Africa are lucky to have at their disposal what is the longest pollen record on the African continent.

Fires on the crater hills, Lake Bosumptwi

Fires on the crater hills, Lake Bosumptwi

Last evening, as the day glow faded, I saw the first of the stars emerge and a shooting star pass. I wondered briefly if meteors might strike the same place twice? Very unlikely, but it reminded me that we are on a planet in a vast universe (I can’t cope with the concept of multiple universes). I felt small and transitory. That’s a danger of archaeology, it can make you think well beyond yourself. A Club beer helped settle the mind. The stars were obscured by clouds by the time I went to bed. They were a harbinger of a storm that would pass through in the early hours. The zinc roof was pelted with what sounded like nails and the sky lit-up with sheet lightning. I couldn’t sleep and so made some notes. This great body of fresh water must have attracted early humans; what material did they use for making stone tools? The rocks I had seen on arrival didn’t look right for flaking – in capitals letter I wrote BREAK ROCKS! This morning the fisherman were out early and I went down to the beach to break rocks, of course. Just as I thought, the stuff just shattered. Among the grey cobbles there are, however, white glittering pieces of quartz, like those at Asokrochona and the Naval College. The first piece I picked up showed the tell-tale signs of having been smashed on a stone anvil with a stone hammer (bipolar flaking, it’s called). Stone Age folks were here then, but the next step is to find a place that preserves these tools in sediment that can be dated.

Spot the quartz core

Spot the quartz core

I’ll add Lake Bosumptwi to the already too long ‘to do’ list. There’s rarely a holiday for an archaeologist, even at the beach.

Local fishermen opposite the site yesterday morning

Local fishermen opposite the site yesterday morning

Every job has its routines and over the past few days ours has involved intensive use of spades, trowels, handpicks and dustpans. An air of determined concentration descended at the expense of small talk.

We have been working through heavy, wet, clayey sand to get to the base of the section. My hands and back are saying ‘enough, stop, go back to the desk job’. [Why hasn’t someone set up a gym where paying customers shovel sand? It’s a great full body workout!]

The cliff face on which we've been working - we covered pretty much the whole area

The cliff face on which we’ve been working – we covered pretty much the whole area

To be honest, I wasn’t prepared (or fit) for this level of exertion in such heat and humidity. By the third day of digging it was getting a little easier and then we hit a layer of densely packed cobbles held together by a particularly sticky and sulphurous clay.

Cobbles were good news as it meant we were nearing the bottom of the sequence, according to our predecessors who discovered this site. But they were bad news for the already complaining hands and back.

Basal cobble layer being exposed

Basal cobble layer being exposed

The hands took the brunt of it, with twisting and turning of the tip of the trowel to work around and under a cobble. The blade of the hand-pick was useless against the wall of cobbles, but the secret weapon was the blunt point on the pack of the pick. It nudged apart the defences of the massed stones.

Slowly we worked our way through, stopping for a slug of water or to answer questions from passers-by. Everyone assumes we’re looking for gold or diamonds, so it’s worth the effort to set them straight.

A studious-looking young man with black plastic glasses stopped and watched. I glimpsed the dog-eared bundle of ‘The Watchtower’ under his arm and assumed that what followed wasn’t going to be an easy conversation. I was wrong. It was enjoyable.

The young man was searching for direction in his life and wanted to discuss the apparent incompatibility of science with belief. He was open to understanding through questioning, rather than accepting dogma (‘The Watchtower’ belonged to his mother). Before leaving, witnessing the self-imposed hard labour of cobbles in wet clay, he asked, ‘why do you do this?’.

‘I need to know,’ I said, ‘I need answers to why the world is the way it is – and that includes our past.’

He may be reading this blog post now, I hope so.

Back to picking away at the cobbles, I was thinking how unlikely it was we would find anything in this deposit. The high energy environment in which these rocks were deposited wasn’t going to attract humans or preserve tools in a decent state.

At that moment, George called me over to look under a slab he was cleaning – and there was a flint-like flake that had then been flaked – a ‘flake as core’ in the terminology. And it was still sharp-ish. It was a welcome find, not because of the unusual raw material but because of its setting.

George in section 2 basal cobble lay,r with flake beneath to far left

George in section 2 basal cobble layer with flake beneath to far left

Flake beneath the cobble layer (section 2)

Flake beneath the cobble layer (section 2)

Close up of flake

Close up of flake

We had found flakes and cores in the overlying sediment and found them eroding out of the cobble lines just above bedrock along the cliff base, but this was the first we came down onto by excavation.

 

I was relieved. Our previous finds were not just flukes of nature, they do occur in this cobble deposit. Nygaard and Talbot (1984) had said this was so, but I needed to see it for myself.

We’ve nearly finished exposing the sections now, with just some recording and descriptions left to write. Then, when Professor Geoff Duller arrives next Tuesday, he’ll be able, we hope, to work his physics-based magic and start the all-important process of finding us some dates.

View from our parking spot - my colleague George says the plants in the foreground can cure malaria

View from our parking spot – my colleague George says the plants in the foreground can cure malaria

Tide coming in around the bedrock Naval College

Tide coming in around the bedrock

Today we returned to the Regional Maritime University (former Naval College) to look for the best places to expose sediments for dating. By ‘best’ I mean those parts of the coastal cliff face which preserved the deepest sediment pile and which contained artefacts.

Laterite and sand scarp behind Naval College

Laterite and sand scarp behind Naval College

We started at the top and while were discussing the finer points of the laterite cap on the Nungua Formation (see Nygaard & Talbot 1984) a bearded man approached dressed all in white, barefoot, wearing a blue and white ankle bracelet which looked as if it was made of the characteristic local glass beads, like trade beads, with necklace to match. He asked what we were doing and my colleague George Anochie said simply ‘history’. I stepped in and began to explain, but George gave me a look that said, ‘stop’.

The man walked off quietly.

Overview of the spit of sediment with artefacts 1,2,4-6

Overview of spit where some of the artefacts were found today

George explained that the man was the wulomo, the spiritual leader for the area – including the sea – who had come to collect a special water from the cliff. I jokingly asked if he had given us his blessing – and George said yes.

I should know better than to be surprised by such things – and it felt almost reassuring.

Back at the cliff face, we finished looking at the laterite and went down to the beach to scout for artefacts at the base of the sequence, where the sand meets bedrock and bedrock meets the Atlantic Ocean.

Core close up

Core close up

Prepared core

Prepared core

Within minutes we found what turned out to be the most significant find of the day, a core, shaped by the structured removal of flakes from both surfaces to produce an oddly asymmetrical object which, when struck with a stone hammer, would have released a thin, sharp flake.

This a technology of the African Middle Stone Age (and the Middle Palaeolithic of Eurasia) and one that Nygaard and Talbot said occurred locally, but rarely. Finding it here, just above bedrock, meant we are in the right place to try and date the Middle Stone Age on the coastal plain of West Africa. That’s the aim of this little project and it moved a bit closer to success today.

I hope the wulomo makes another appearance tomorrow – and continues to give us his blessing.

Tide coming in at Naval College site

Tide coming in

In with the tide

Carried on the tide …

Plastic bottles on the beach, Naval College

Turner prize installation? Or just plastic bottles?

 

 

‘Tomorrow’ is now several days later and while things are going well here as far as the work goes, there have been some minor challenges – such as being without electricity and wi-fi.

We are all so dependent nowadays on email that the latter is almost as bad as the former. But not quite, because it’s very warm and very humid here – especially for someone who was, only a few days ago, in a land of frost and wintry winds.

The electricity blackouts are apparently becoming more frequent. Ghana’s population has increased from 5 to 25 million over 50 years or so and the primary source of energy has remained the hydroelectric dam on the Volta. Meanwhile, living standards have risen for much of the population (though by no means all) and those who can are installing air conditioning, washing machines, big screens – and so on. Something has got to give – and it’s the power supply.

Mapping the formation

Mapping the formation

Today’s been another day of extreme heat at the site – which is at a railway cutting through a hill at Asokrochona. I can cope for about two hours then need to seek what little shade there is at the site. That shade is cast by a breeze block wall built at the top of the railway section as part of a planned house which has now been abandoned. The wall casts a shadow 18 inches wide on the ground and I squeeze up to it and adopt a half squat being careful not to make contact with the ground.

Our audience at Asokrochona - the little girl who wants the laptop  second from left

Our audience at Asokrochona – the little girl who wants the laptop second from left

This old archaeological site has been overtaken by the inhabitants of a poor shanty town – and in the absence of plumbing – well, you can see where this is going. The people here live on the margins. The usual attentive children we attract are more than usually polite – in exchange for a Fox’s Glacier mint I get a ‘God bless you’. I have with me a small ruler with a hologram of a panda on it climbing up a branch which is a real crowd pleaser. One little girl asked if I was Chinese – and later, inevitably, followed up with‘bring me a laptop’. I wish I could.

Standing on top of the railway cutting and looking past the scenes of poverty I see a beautiful sea, waves breaking on the beach and always at least two dozen ships queuing for the port. Our next location will be at the former Naval College and the people there have been very helpful and interested in the project. We’ll be excavating in the cliff face overlooking the beach and – all being well – we start Monday.

On the beach below the Maritime University with the team and University staff

On the beach below the Maritime University with the team and University staff

The Regional Maritime University is quite a place. They have a variety of ships’ lifeboats on cranes to practice evacuation and they drop them into deep tanks. There’s also a helicopter-shaped simulator that is dropped from a crane to practice evacuation. A separate large swimming pool (which in this heat looks luscious) is used to ensure that every seaman can swim. There’s a further set-up to practice evacuating a ship on fire – and a large ship’s command deck filled with navigation training equipment. Amazing. In fact, I found it all so interesting I’ve realise I’ve written more about that than the work in hand…

Here we go, just a little to whet your appetite.

Looking down the line towards the station

Looking down the line towards the station

The site of Asokrochona is an impressive railway cutting through a low hill that exposed two two high banks. The cutting was made in 1953 and recorded soon afterwards by Oliver Davies. The first excavations were undertaken in the 1970s by Bassey Andah and Signe Nygaard with the critical help of geologist Michael Talbot. Talbot’s description of the sediments and Nygaard’s interpretation of the artefacts as belonging to the Sangoan Industry have brought me here.

George Anochie (National Musuems and Monuments Board) and Siaw Appiah-Adu (University of Ghana) with large quartz flake from the Sangoan level

George Anochie (National Musuems and Monuments Board) and Siaw Appiah-Adu (University of Ghana) with large quartz flake from the Sangoan level

Quartrzite core and flake from the Sangoan level

Quartrzite core and flake from the Sangoan level

The Sangoan is hard to describe, it’s certainly not visually appealing – there very few carefully crafted tools – and we know very little about what the tools were used for, or even how old is this ugly part of the archaeological world. It may be part of the transition from the Early to Middle Stone Age which is why I’m interested. This transition isn’t well dated anywhere in Africa and West Africa is a particularly large blank in the puzzle. We’re here in Ghana with funding from the Leverhulme Trust to try and date the sediments at Asokrochona and at the nearby Maritime University.

Cleaning the surface carefully to expose the intact sediments

Cleaning the surface carefully to expose the intact sediments

Close up of pottery found near the top of the section

Close up of pottery found near the top of the section

We’re not allowed to excavate at the railway cutting because of the risk of undermining the embankment, but we’ve been able to clean the surface from top to near bottom in preparation for sampling for dating. In the process we’ve found pottery at the very top and large quartz artefacts just where they should be according to the work of our predecessors. The project also takes us to a nearby coastal cliff at the Regional Maritime College where there are fewer artefacts but they are in plenty of sand – which is just what’s needed for the luminescence dating to be done by Prof Geoff Duller, who arrives later. There’s sand at the railway cutting but not so deep – and it looks old and weathered. I hope it will prove workable, though.

The site, scraped clean and ready for drawing and sampling

The site, scraped clean and ready for drawing and sampling

Tonight’s been my first chance to write anything up of my experiences so far – and though there’s plenty more to say, right now the priority is getting to dinner and eating fried plantain, beans and chicken (one of the tasty and sometimes blistering offerings). The project’s just started and I’m already frazzled by the heat, lack of electricity and the nightly chorus of evangelical students whipped into the fervour needed to speak in tongues. Last night the tongues were busy until 3am (they normally stop at 10pm during the week). To top it off there was no electricity to move or cool the humid night air. I lay there radiating the day’s heat and trying to get to sleep by imagining the human chorus as the voices of exotic birds or frogs.

Wouldn’t it be great if the electricity made a nocturnal comeback after dinner – so I could have the fan on – or the aircon tonight? Not only would it keep me cooler – it would help subdue the night sounds – the human ones!
Yes, ever the optimist …

At the University of Ghana (Legon), the main library building

At the University of Ghana (Legon), the main library building

 

 

 

 

 

 

 

 

 

I arrived safe and well yesterday and settled into my bedsit on the university campus. It was a slightly fitful night, full of unfamiliar noises, but no worse than the fitful night I had before I left, which was just full of familiar travelling worries.

The guesthouse setting is lush and tropical, with butterflies and unusual birds for entertainment plus the requisite scent of rubbish being burned somewhere. There’s a heap of building waste behind my room with egrets clambering all over it – looking for lizards, maybe. A caretaker has, I see this evening, already begun transforming it into a garden.

Today was spent organising things. Preparations are now all in place to start work tomorrow – the permit is signed, the driver* will be here with our assistant from the Museum at 8 am and a colleague from the University, Siaw Appiah-Adu, will join us tomorrow and on days when he’s not teaching.

Roadside stall in Accra selling colourful array of soft drinks

Roadside stall in Accra selling colourful array of soft drinks

We’ve bought a crate of bottled water and rolls of shortbread and ginger nut biscuits for energy boosts when digging. Sandwiches are promised and should be ready for me to pick up by 8am – the timing something of a test for the kitchen!

Renowned archaeologist Professor James Anquanda has, he tells me, been mentioning my name in class here at the University of Ghana (Legon), telling students I’m going to sort out the Pleistocene record of Ghana. No pressure … But of course I’ll do my best in the slightly-less-than three weeks at my disposal.

Professor Anquanda will be bringing a class out to the sites for a tour once we’ve got going. After Professor Geoff Duller from Aberystwyth has arrived and we’ve done some of the sampling for dating (his highly specialised expertise) we’ve been asked to give a seminar (on the evening of Friday 27th) to present our interim results.

Tonight Siaw is coming by to take me to the ‘Senior Common Room’ where I’ll be treated to a Black Star beer. This is not a Senior Common Room as we know it, I suspect!

I hope to post again tomorrow with somewhat more academic news of dashed hopes or interesting discoveries – ever the optimist.

*  You think a driver’s a luxury? Well, I’ve been here before – and the taxi rides left me gasping both from the fumes and the driving. Today’s traffic was stunning in its reckless ingenuity when faced with obstacles – in one notable incident we all switched over to a lane of oncoming traffic to avoid waiting for the ‘trotros’ (small buses) to disgorge and collect passengers. By force of numbers our illegal convoy pushed the oncoming traffic aside into one lane and no one batted en eyelid though I did let out a small involuntary shriek.

Driving in Lusaka, Zambia’s capital city is stressful and I dread it, but Accra’s much worse than Lusaka. If I drove and followed the law I’d be stuck in one place for days at a time – and a trembling wreck. That’s why we have a driver!

Welcome!

I’m an archaeologist from the University of Liverpool and I’m getting ready to leave for a pilot study, excavating in Ghana, with the help of colleagues from the University of Ghana (Legon) in Accra and the Ghana Museums and Monuments Board. We’ll be looking at Stone Age sites along the coast and I’m hoping to post regular updates and images here.

That’s all for now – back to my packing!

Larry

Professor Larry Barham, University of Liverpool, England

IMG_1485

Ghana’s beautiful coast in 2013

February 2015