Hi, I work at the University of St Andrews and am using this blog to show some of the work around the world that I am lucky enough to be involved with. I will be dumping a series of blogs shortly to catchup with what has been going on over the last couple of years. I hope you enjoy the site.
Over the last 10yrs or so I have made a number of visits to
the Outer Hebrides for both work and holidays. Most of the research trips have
focused on marine biological habitat mapping and assessment of the impacts of
storm activity on the coast lines. However, as with most of the Scottish landscape,
the archaeology of the islands tells a compelling story, especially in comparison
to the work we are currently doing up in Orkney. So when Donald Herd, a colleague and native
of Lewis, mentioned the possibility of a trip to visit his ancestral stomping
grounds with the possibility of building collaborations for some future work on
the islands I readily agreed to go even if it is sometimes dodgy weather in
March!
Donald hails from the village of Suainebost in the far north
of Lewis where there is a fantastic community historical society – Comunn Eachdraidh
Nis. This group is working to
preserve island history, language and culture for both local community now and
in the future as well as providing a resource for visitors to the area. This
north part of the island has a diverse range of heritage on offer from some of
our most ancient rocks in the Lewisian Gneiss to the heritage of the people. A
great example of this is the recently completed investigations published in two
books by Chris and Rachel Barrowman on the archaeology and heritage of Ness and
an investigation on the unusual 16C-17C remains on the sea stack of Dun Eistean. Hopefully we will be able to find funding to
work on some of this in the future.
The island of Lewis is justifiably famous for its
archaeology, the centre piece of which are the iconic standing stones of
Calanais (Callanish). The best estimate
of when the stones at Calanais were raised is about 3000BC, nearly at the time
that farming began during the Neolithic here. However it is incredibly difficult
to date the actual erection of stone circles, especially when almost no other structures,
either houses or burial chambers have been discovered in the surrounding
environment. We visited this site in order to check out the wider landscape as
a potential place to conduct palaeo-landscape studies. Since it was a quiet time of year with no
visitors, Donald also took the opportunity to fly the site for aerial
photography. The results were quite
stunning and fit nicely into the quick 360 image that we took at the centre.
We experimented with photographing a number of the stones as
the structure displayed in the Lewisian Gneiss that the Neolithic people used
is quite stunning!
As the day was such a good one we visited a much later broch
on our way back to the north of the island.
Dun Carloway is a remarkably well preserved Iron Age broch (a type of
fortification found throughout Scotland) likely constructed between 100BC to
100AD. It is of typical double wall construction which can be seen in the east
side. The remains were in use, laterally as a kiln until at least 1000AD. Folklaw has it that the clan Morrisons of
Ness (Donald’s ancestors) used to hide in it while they went on cattle raids of
their rival clan, the MacAulays!
Now looking forward to a trip back, if for no other reason than to try some of the island's famous product - Black Pudding! trouble is there are so many to try .......
Hunting the drowned “Red Snake” – The Sasanian Persian Empire’s
Great Walls
One more field site for the year - at least I think so! A couple of years ago Prof. Eberhard Sauer (Edinburgh
University) got in touch as he has had a 10yr project investigating the “Red
Snake” of Persia. This is better known
as the Gorgan Wall that once ran near the border of Iran and Turkmenistan from
the Caspian Sea in the west and the Elburz Mountains in the east.
At a known length of over 195km it was pretty significant as
an ancient line of defense. However, not
so today as the westernmost part not visible even to archaeologist in the present landscape. The problem with the wall is that it was constructed of mud
bricks and so the ravages of time and the deconstruction (robbing) of bricks
for use means that it is often difficult to see today. However there is a silver lining, or at least
a geophysical signature silver lining, that results from the use of
bricks. That is that the firing process of
making bricks can give a strong magnetic signature to the bricks. To make them requires a few key ingredients,
namely a good clay with some larger silt or sand grains and water. Lucking the clay is in abundance all along
the wall’s path but water in this semi-arid area can be a problem. So a solution was found by diverting local
rivers to run feeder canals to a ditch that ran along the length of the wall
thus providing not only the vital water but at the same time a quarry for the
clay and when the wall was completed an extra defense line!
C5-6th Kiln
195km of wall requires quite a few bricks – it has been
estimated that over 200 million in total were used! Making these bricks was achieved using
temporary field kilns set up all along the path of the wall at approximately
50m intervals. The wall was garrisoned
by an arm of over 20,000 soldiers barracked in at least 30 forts. The project team have spent the last few years excavating some of these kilns together with
some of the forts and sections of the wall itself. They have also investigated a sister wall,
the Tammisheh Wall that ran from the southeast corner of the Caspian south to
the Elburz Mountains. Through C14 and
OSL (Optically Simulated Luminesance) dating their work puts a construction
date on both walls to the Sasanian Persian Empire between the 5th
and 6th Century AD.
So what am I doing here?
The western extent of both walls is unknown. Historical writing describes how the walls
enter the Caspian Sea and certainly the Tammisheh Wall can be traced almost to
the modern shoreline but where it goes after that is unknown. Some descriptions even suggest that both
walls were joined up. So we are back again to our old problem of changing sea
levels and with it the usual battering that this can give to the landscape and
our human endeavours.
So I am here to help out with the searching for the walls,
both on the sea floor and beneath it if they have been covered by more recent
sediments. We were looking for
upstanding bricks or a scattering of bricks on the seafloor with the hope they
would not have disintegrated. Beneath
the seafloor the hope was again to find lines of bricks or mounds. Perhaps we would also see the cross –section
of the trench that ran along the wall.
With the magnetic signature associated with the kilns on land this might
stand out too but for this first preliminary survey I chose to use the Tritech Seaking
Parametric Sub-bottom Sonar that we have found so effective in the shallow
waters of Orkney together with an ultrahigh resolution Tritech Starfish 990kHz
Sidescan Sonar. A great advantage of both these systems is that they can be
taken as hand luggage on flights!
small boat work with Tritech Sub-bottom sonar and Starfish Sidescan
We started with the Tammisheh Wall as the projection into
the Caspian is better known. The parametric sonar proved worthwhile once again
despite the occasional gas blanking by picking out a strong reflection from the
brick scatter on the sea floor. The
signature of this continued as it became buried further offshore with up to 2m
of sediment. After approximately 3km it
abruptly disappeared or terminated. The
scatter on the sea floor was also mapped with the sidescan sonars from which the
surface brick scatter was readily identified together with a number of linear
features.
Given the time available for this trip and the relatively
less knowledge on where the Gorgan Wall might be crossing the shore line we had
a much larger potential target area to cover.
With a few days of poor weather (yes the Caspian does get rough with
over a 1m wave and swell heights) we covered a large area but without finding
any definitive wall signatures. So more
and better targeted data acquisition is needed for the marine side here. What I now propose is to return and try with
a magnetometer and an electromagnetic ground conductivity meter to survey from
the last known western point of the wall across the land and shallow lagoons to
the shore. If we can trace this then we
stand a much better chance of mapping it offshore, if that is where it goes. Video summary of the trip:
I had a fantastic crew out with me on the water (I cannot
thank Hamid, Bardia and Hassan enough) and also back in the base as the joint project leaders, Dr Jebrael Nokandeh of the National Museum
of Iran and Eberhard have assembled a talented team of archaeologists for the project.
So, another privileged trip to work with some great people,
such friendly banter, engaging conversation, fantastic archaeological
potential, some great food and wonderful scenery – the bird life on the Caspian
is stunning! I can’t wait to return next
summer equipped with magnetometers and electromagnetic gear to continue the
hunt.
Iran-British Gorgan Wall Project Team
Dr Jebrael Nokandeh (National Museum of Iran);
Mr Hamid Omrani Rekavandi (Iranian Cultural Heritage, Handcraft and Tourism
Organisation of Golestan Province); Bardia Shabani, Hassan Taji, Mohammad
Ershadi, Maryam Hosseinzadeh, Mohadeseh Mansouri, Meghdad Mirmousavi, Mohammad
Bagher Bayati Mehdi Jahed, Alireza Salari, Esmaeil Safari Tamak, Majid Mahmudi,
Return to Chew Bahir – the Seismic Reflection Story
Two years ago we (St Andrews, Dei Huws at Bangor and Tigistu Haile at Addis Ababa University) visited the Chew Bahir basin in order to acquire
geophysical data in advance of the HSPDP (Hominin Sites and Paleolakes Drilling
Project)
drilling a hole to investigate the palaeo-climate of the last 500 thousand
years. The overall aim of this programme
is to investigate palaeo-climate at key African Hominin sites. During the first
geophysical survey we used electrical resistivity tomography near to where
previous shallow (20m) boreholes had been drilled by the HSPDP group on the
lake bed at Chew Bahir. In addition to
our shallow geophysical surveys Tullow Oil had also completed a programme of
deeper hydrocarbon seismic reflection investigation. The results of both these were used together
with the shallow drilling to pick the location of the deeper borehole. In 2014 this hole was drilled with much
success and is now undergoing extensive investigation at a number of research institutes.
So what were we doing back in the basin? An important part
of trying to understand the core sequence and determine the environmental
change that it represents requires that we have confidence in how the core fits
with the larger geological story. This
means a better knowledge of how to extrapolate the data away from the
core. This requires geophysical data and
the best type for this is high resolution seismic reflection. So this was what we went to do.
Our data was acquired with a 96 channel Geometrics GeodeSystem with a 40kg Propelled Energy Generator impact seismic source. After a walkaway
survey we decided to shoot the data with a 32m source offset and 4m geophone
interval. We shot the data with 72 fold
coverage along two crossing reflection lines over the borehole site and an
additional 3 refraction lines to evaluate near surface velocities. The seismic crew consisted of the previous
team joined by Dr Erica Galetti from Edinburgh University and Yemane Kelmework from
Addis Ababa. Tim Raub (St Andrews) also
came along to add his geological savvy to the project and to look at a number
of other geologically-relevant sites (see later blog on this for some stunning
new sites!). The initial data looks very encouraging with numerous reflectors
identified. Processing will tell how
good the final data will be and that will happen over the next few weeks.
Despite the relatively dry year with almost drought
conditions we managed to grab the data just in advance of the little rains
starting. Downpours on the last morning flooding
the local roads and turning the dried lake bed into a gloopy mass that was
impossible to drive on.
During the field work we camped at the village of Arbore and
employed a fantastic cook from a nearby town.
The field work would not have gone so smoothly without her keeping us fantastically
fed on traditional Ethiopian foods (injera, shiro, and of course some local
goat) and also without the help of our two drivers, Yared and
Solomon.
So we have
returned for another season in Jersey as part of a three year project to explore the deep prehistoric past, from
exploration of the island caves, through the archaeological excavation of
hunter gather camps preserved in the island’s interior, to the iconic sites at
La Cotte de St Brelade. In all of these
locations we aim to discover why this remarkable landmass attracted Neanderthal
and modern humans at different time periods. Over the past 3 years we
have been acquiring geophysical data both onshore and offshore in order to
re-create the landscapes of the past. We
have also had a number of investigation sites such as the one at Les Varines
shown below.
Earlier
in the spring we acquired 2D electrical resistivity tomography (ERT) data at
the site, which together with boreholes drilled through the sequences allowed
for the targeted expansion in the excavation.
At the
other side of the island we are trying to survey cliff sections that will give
us further insight to the history of climate change in Jersey over the last
200,000 years as recorded in the sediment sequences, and hence palaeogeography
of the La Cotte site. In Portelet Bay to
the south east of St Brelades there is a particularly well exposed Pleistocene deposits. The only problem is that its 15m high and
loose – a job for extreme geophysics! By
abseiling off the top of the cliff we were able to clean a sufficient amount to
achieve mapping, photography, sampling (for OSL dating, palaeo-climate and
palaeogeographic setting) and a geophysical profile. The geophysics consisted of both magnetic
susceptibility and DC resistivity. The
mag did not produce much differentiation however the DC resistivity mapped
distinct boundary changes within the various units. The preliminary results are
shown below and you can visit here for some live action!
Actually the Rising Tides team are back up in Orkney, Sanday
to be precise, trying to chase environmental signatures of the past while also
trying to dodge a weather bomb! So what
is it we are actually doing and what is a weather bomb? As those of you who have read any of our
previous work will know we are particularly interested in understanding
palaeo-environments, landscapes and geography in relation to past
societies. Our work on the mainland,
that is the mainland of the Orkney Isles, has reconstructed drowned landscapes
through geophysical, coring and diving work.
On Sanday, we have come chasing the records of a drowned forest. Sounds familiar? Well yes, in some ways it is
similar to those sites on the west coast of Wales, and from a much older time
frame the sites at Happisburgh where we
found the oldest footprints outside Africa last year. Here in Sanday however we are trying to link
back to that critical period in the development of human behaviour, the change
from hunter-gatherer in the Mesolithic to the farmers of the Neolithic.
So why Sanday? Well, for one reason that a “drowned” forest
has been written about in the past. In 1867, in the History or Orkney the Rev
George Barry reported a “strong
tradition that the harbour of Otterswick in Sanday was once a forest, which was
destroyed by inundation. “and further, a sample of the trees was obtained by Traill-Dennison
in March 1890. We walked the beaches
here and ran some speculative geophysics last summer with encouraging results
that led us to a bay on the west coast of Sanday where with great luck on a
particularly low tide we spotted a small raft of peat. Coring and measurement of its elevation confirmed
that it was equivalent to the Otterswick Bay samples and so here we are, back
again on a series of very low spring tides to get further samples.
So what’s the problem?
It’s December, there is limited daylight here and we have the “storm of the
century” approaching (think The Perfect Storm)!
The task therefore is to get some samples and undertake some more
geophysics before it hits. The tactics –
geophysics (always geophysics) but most importantly some serious extreme
geoscience sampling – a JCB! (for those of you who are not familiar with this
great vehicle, and actually its not a JCB that we are using, then it’s a
backhoe).
The results – instant
sections, great samples and all done before today with its horizontal sleet and
snow. We have now dug four test pits
(typically in fading light at low tide, actually it was dark!) and found the
peat. Significantly the peat we have dug
appears to be full of freshwater molluscs at the base but towards the top there
are articulated marine bivalves as well as whelks and other marine
molluscs. This is what we are after – it
documents the onset of marine conditions and allows us to begin to understand
how marine waters flooded across these Mesolithic landscapes. Elsewhere we have been augering in probable
infilled bays where we discovered more than 2.5m of peats and sands alternating
throughout the core. This documents the
interaction between the land and the sea and excitingly these cores are very
close to a multi-period archaeological site that started in the Neolithic and
continued intermittently until the Viking period. So mission accomplished so far….watch this
space
Scot2K – a dendrochronological project the Scottish Highlands (NERC (NE/K003097/1)) that aims to push back the
high resolution climate record of the Scottish Highlands back 2000 years. It has both local (UK) importance
and will also contribute to the wider climate record of Northern Europe and
Northern Hemisphere.Growth of Scots Pine
trees in the Scottish Highlands is predominantly controlled by growing season
temperatures. Using parameters measured from tree-rings (i.e. ring-width and
density) it is possible to derive estimates of past summer temperatures.
However, the mean age of most pine trees in the Cairngorms is around ~225
years. Therefore, to derive climate estimates prior to ~1750, information must
be gleaned from older preserved woody material.
Where to find this
material? Well thankfully, Scotland is
not without its lochs and it is into these that many of the older trees have
either fallen or have been felled.
Finding these trees and then sampling them was the goal of a recent trip
to Glen Affric. The team, under its climate warrior leader, Dr Rob Wilson, had
previously scouted out (swimming with snorkels) some of the small lochs. Others were known
from the Trees for Life project (http://www.treesforlife.org.uk/).
The UK team, including individuals from Sweden
and Switzerland (Dr Richard Bates, Dr Cheryl Wood , Stacey-Anne Averill, Dr
Mark Neal, Dr Björn Gunnarson, Dr Neil Loader, Dr Daniel Nievergelt, Dr Coralie Mills) arrived in
Glen Affric armed with dry suits, saws, corers and a new remote-control survey
boat. The boat, built by students at Aberystwyth University Computer Science Department contained a
900kHz sidescan sonar and GPS logging to small laptop in a hull that was
sufficiently small to be back-packed
into some of the more remote lochs. This
was considerably easier than trying to get either of our previous survey
vessels, the Zego Boat or Minty (see previous blogs for both) onto the water. Why use sonar? Well if you have ever swam in
an upland loch you would know how murky the peat-ladened waters are that
restrict visibility to a few centimetres.
Processing of the
sidescan sonar data was using Chesapeake SonarWiz and ultimately data display
within GIS. Targets were identified and
the dive team went to work. Many of the
sites contain vast numbers of trees but many are in too deep water or are too
far from the shore for recovery (usually an operation using wire cables and
winches attached to living trees on the loch shore). Many of both living and dead tree root
structures were visible on the sidescan records as were very curious sinuous
features that we have so far been unable to identify due to the murky water. These are likely branches.
At the end of the
week the team had found and sampled over 150 trees – a highly successful
hunting trip. Now for all the analysis
though and a hope that the material will contain sufficiently old records to
push back the dendro record.To date, 661 sub-fossil pine
samples have been collected from lakes in the NW Cairngorms: Loch Gamnha (215),
Loch an Eilein (293), Green Loch, Ryvoan (67) and multiple lakes in Abernethy
(86) - about a third of which have been dated using radiocarbon dating or
tree-ring (dendrochronology) methods. However, dendrochronological dating of
the samples has been a challenge. It has become clear that the impact of human
disturbance (related to tree felling) has had a profound influence on the
growth of the trees which decouples tree-growth from climate. Although these
human based disturbances impact on the potential climatic information that can
be gleaned from these samples, an unplanned outcome of this work will be the
detailing of the human timber extraction/land-use history (likely a part of the
Highland Clearances story) of the regions sampled through the Scottish Pine
Project (i.e. the native pine woodlands). A network of over 50 pine woodland
sites have now been sampled across Scotland
(http://www.st-andrews.ac.uk/~rjsw/ScottishPine/). This is an exciting outcome
as it will allow a new appreciation of the impact of logging on pine woodlands
and their resultant recovery over multiple centuries.
Tree-ring based reconstructions
of past summer temperatures are still in development. Through Milos Rydval's
Carnegie Trust funded PhD project, Rob’s team have spent a substantial amount
of time developing the new Blue Intensity (BI – a proxy of lignin content and
cell wall thickness of the latewood) parameter (Rydval et al. 2014; Wilson et
al. 2014). Utilising both RW and BI data from Abernethy, Green Loch, Loch an
Eilein and Loch Gamnha we can already produce a well calibrated (55% of the
July/August temperature variance explained) temperature reconstruction back to
AD 1460 (see Figure).
Tuesday, 26 August 2014
Christchurch - Priory and Mill
While down at Stonehenge (more on this to follow shortly with a press release on Sept. 11th) I managed to spend a morning with an old friend, Peter Fenning, helping out with some local archaeological sites in Christchurch. In particular, we ran a frequency domain electromagnetic survey over the grounds around Christchurch Priory. For this we were using the CMD Explorer with gps positioning. Initial results were very promising with what looks like a signature for the main site well showing up as a very strong anomaly.
The figure above is for the deep conductivity (down to 6m). We still have to process the data and integrate it with the rest of the site information so more to follow later. In the mean time follow the Christchurch group at: http://christchurchantiquarians.wordpress.com/blog/
