Chew Bahir, ERT 2013

I am just about to leave for Tanzania to do some offshore archaeological surveying with Ted Pollard from BIEA (I will be blogging on this on my return) but I thought before I went I would post a short video that was compiled during a field campaign late last year to the Rift Valley in southern Ethiopia. 

I made this trip together with Dei Huws (Bangor Uni) and Tigistu Haile (Addis Ababa Uni) as part of a much larger, international project that is drilling a number of locations throughout East Africa that are linked to key Hominid sites.  The overall aim of this is to be able to provide dated information about environment and climate at key stages of hominin development and migration.

The Chew Bahir site is located in SW Ethiopia close to the boarder with Kenya.  The large valley generally drains to the south into Lake Stephanie but the northern part where we hope to drill our core is only flooded on an infrequent basis.  As with many of arid areas, when it rains it does so often causing drastic and violent floods from the surrounding uplands that wash coarse river gravels far out into the generally flat valley floor.  Since our drilling objective is to obtain as simple a geologic sequence as possible the first task is to locate an appropriate site that has not been affected by the alluvial fans on the valley side or any of the ancestral rivers that migrate across the valley bottom. 

So, in November we made a preliminary field visit to the site armed with magnetic and electrical resistivity tomography/imaging (ERT) equipment in order to find appropriate sites.  Our choice of locations for the geophysics was based on some regional background work on geophysical signatures and also on some local knowledge kindly shared by Tullow Oil Plc.

The site is quite special and like nowhere I have worked before as you can see from the video.  We managed a couple of sites during our survey, one in the centre of the basin, the preferred core location, and one over an alluvial fan sequence at the edge of the basin.  The ERT gave some great results despite the arid conditions mainly I think because of the relatively high conductivity of the lake sediments – likely a result of the periodic wetting and drying. The alluvial fan was readily recognised in the ERT sections at the basin edge but no signatures of this were recorded at the centre of the basin where a fairly uniform sequence was modelled.

The next stage from us it to return to do a seismic reflection survey in order to image the top 400m (the core depth) in much greater detail. 

Happisburgh ERT Geophysical Survey, Jan 2014

Happy Days are here again!

Why happy? Well we are back in Happisburgh on the north Norfolk coast staying in the Hill House pub (of Sherlock fame – the Dancing Men, and also with a cracking set of handpump real ale) and running electrical sections across the country side. 

The site has previously yielded evidence of the UK’s oldest ancestors.  It was here in the early 2000s that artefacts and associated plant and animal remains were discovered that is the earliest evidence outside southern Europe for human activity, older than 780,000 years before present. Not only that but the biological remains suggested these people were living in an environment similar to that of present day southern Scandinavia.  These remains were found in a river channel close to the sea that was subsequently buried by thick sequences of deposits when East Anglia was covered in ice around half a million years ago.



ERT line at the big manor, Happisburgh

Over the last couple of years we have been visiting the site and using different geophysical methods to try to reconstruct the palaeo-landscapes at the key time periods in relation to the artefacts.  We have used both electric and electromagnetic surveys on the foreshore across the semi-buried channels and inland from these trying to chase the channels as they are buried beneath other sediments.  Specifically we have used a Geonics EM31 to map the lateral extent of the channels on the beach and then an Abem Terrameter to acquire 2D geo-electric sections (ERT) in a grid pattern across the fields surrounding the village in order to understand the landscape structure.  The data is processed using RES2DINV and then visualised in Fledermaus.  Ultimately, these landscape reconstructions will enable better targeting of the archaeological investigations and also allow us to try and understand where the early people were possibly living and how they were using the landscape.  

Many may know this part of the coast for its rapid and drastic erosion and retreat.  Since we have been coming here the cliffs have shot back well over 40m! Devastating for many locals, some of whom have lost their entire houses to the North Sea, but for us it comes as a mixed blessing as we get new geologic sections to investigate each time we visit with the possibility of new artefacts. Watch the press and this blog for announcements on this next month!




ERT survey line over newly exposed basal member of the Happisburgh Till

For more on this work then if any of you are down in London over the next 6 months then make sure to get to the Natural History Museum for a new exhibit on Palaeolithic Britain “Britain: One Million Years of the Human Story” with a special part on Happisburgh.  Much of this work came from the Ancient Human Occupation of Britain (AHOB) project. So finally, a blog will shortly be written on our other site in Jersey – La Cotte de St Brelade.

The Bates Brothers discuss the latest results (photo Erin Kavanagh)



Some of Last year’s projects - The Beginning of Time?

The Begging of Time 

Last summer, just about the time that the midges come out in full force a team of archaeologists and geophysicists from the Universities of Birmingham, St Andrews and Bradford got together in a field in Aberdeenshire near Crathes Castle.  The outing was prompted by the keen-eyed and insightful thinking of Prof Vince Gaffney who had spotted a curious arrangement of Mesolithic pits form air photos and a previous archaeological site report.  

Air photo and site investigation of sinuous pit alignment

The alignment was unlike most other early monuments in the UK where obvious orientations align with solar and lunar events.  This new site showed a sinuous arrangement to the pits.  While most of us would see no significance in this, Vince’s curiosity was piqued and his brain went into overdrive.  The end result, a geophysical survey, a new interpretation and the theory presented that at 10,000yrs old the feature could be the world’s oldest calendar!

The geophysics: This included electromagnetics, (Geonics EM31 and EM38), magnetics (Foerster Mag) electrical (Geoscan) and ground penetrating radar (PulseEkko).

The end result was modeled to examine what the exact solar and lunar tracts would have looked like 10,000yrs ago.  This showed the site mimics the phases of the moon in order to track lunar months over the course of the year. But that is not all, it also contains elements for alignment with the midwinter sunrise thus providing an annual astronomic correction in order to maintain the link between the passage of time indicated by the moon, the asynchronous solar year and the associated seasons.  Pretty smart of those old Scots running around the glens hunting the deer and fishing for the salmon!

For more information see Time and a Place: A luni-solar ‘time reckoner’ from 8^th millennium BC Scotland. Internet Archaeology, July 15 2013 (http://dx.doi.org/10.11141/ia.34.1)

 

Inphase results using EM31 (high resolution over site, lower for rest of field)