Orkney 2017

Orkney 2017

This summer we (the Rising Tides team – Caroline Wickham-Jones, Martin Bates and Sue Dawson) undertook a number of field trips in Orkney to cover a growing number of projects with partners at the University of Highlands and Islands.

Bay of Ireland

Moving south from our work in the loch of Stenness we have begun a collaboration with Scott Timpany at UHI, Jane Bunting at Hull University and Michelle Farrell at Coventry University. This project aims to contextualise the findings that UHI have published on around the peat deposits where a large oak timber was discovered by Ted Pollard during a campaign of coastal walking (Timpany et al., 2017).  The Bay of Ireland opens into Scapa Flow, the infamous site of the scuttled German battle fleet from WWII. Our investigations however focus not on this rather on the very much older landscape during the early Neolithic when sealevel was still rising to that of today. This now submerged area is typical in that it has an infilling of both ancient and modern sediments.  Our first task was to map these and determine the depth to basement (rock and glacial till).  As with previous geophysical investigations it was also hoped that we might be able to see different layering within the sediments to discriminate packages that could be associated with different environmental conditions. We used the UHI Geoacoustic pinger for the initial survey.  Results gave us the required depth to basement but the quality of data was not sufficient to image sediment packages.  As can be seen by the map of basement depth the bay takes the form of a buried basin that deepens to the south.  

Map of depth to basement and example of sub-bottom profile, Bay of Ireland, Orkney 

The southern limit of the basin is marked by a submerged bank or barrier that stretches roughly east-west across the bay and separates it from the main part of Scapa Flow. Armed with this data we attempted to core through a thicker part of the sequence in the centre of the bay. The core penetrated over 2m of sediment that we now need to analyse.

At the same time as the marine work Scott also attempted to follow the peat layers offshore from the landside.  A rather gloomy, wet day saw him joined by Martin and Sue with hand augers. 

Diving

Following the geophysics and coring we were fortunate to be joined by Nat Hirst and Kerry Santander from SeasearchScotland.  Seasearch divers usually scour the bottom looking at biology but they were game for trying their hand at underwater archaeology in the form of hunt the peat!  Before diving Scott primed them on what sort of features we were after and we armed them with core tubes that could be inserted (bashed with a lump hammer!) into the seafloor.  Over the course of two days they dropped on a number of sites both here and in the Bay of Firth adding greatly to our understanding of the conditions.  Tough work but with the good weather a rewarding trip.  Hopefully they can be encouraged to return when we have more sites for diving.

hand coring on seafloor

Skaill and Skara Brae

In September we returned to the loch of Skaill as our previous attempts to core this site had been thwarted by strong winds. The objectives of this investigation are aimed at further understanding the role of coastal barriers in protecting heritage sites.  In particular we are trying to not only reconstruct the past environments around iconic settlements like Skara Brae but also to understand how the environment changed, and over what time periods it changed.  Once again, the changes are not only linked to climate fluctuations but also to sealevel rise.  It is likely that Skara Brae was first located some distance from the coast with a wetland between it and the sea. As the sea rose the coastal barrier was breeched and the land was flooded. Over the ensuing millennia the sea gradually eroded evidence for this land surface however the environmental conditions are still preserved beneath the site and in the surrounding landscape.  For example, during coastal protection work at the site in 2009 a significant peat layer was noted at the base of the revetment scheme.  Unfortunately, the works did not record this or sample for further environmental signatures.  Published work by de la Vega et al in 2000 does provide a broad environmental setting for the site however our investigation aims to put far more detail into the story. 

A series of cores both on the wetlands to the south of the site and in the loch of Skaill were taken and show a complex sequence of sand, peat and loch sediments. There will certainly be enough in here for environmental analysis over this winter.  Based on these results it is intended to return to the site with a range of environmental geophysical techniques in 2018.

Orkney International Science Festival

September also features Orkney International Science Festival, an event that we try to participate in on an annual basis.  This year we managed a great afternoon out with the P6 class at Dounby Primary School at loch of Skaill, a coring of the Peedie Sea with Scott Timpany at UHI as part of their project on Medieval Kirkwall, a joint exhibit of our palaeo-environmental reconstruction at the family day and a talk on the Borth fossil forest by Bates, Bates and Bates!! (my father, Denis and brother Martin giving the low down on joint work in mid-Wales). 

AUV hits Orkney

In the week of large scale remembrances of the Battle of Jutland that will include amassing parts of the British Naval Fleet, the German Fleet and possibly parts of the Danish fleet we made our own bit of history by testing for the first time one of the new generation of survey vehicles the Gavia AUV in the waters of Orkney.  The Gavia (Teledyn, Iceland) Autonomous Underwater Vehicle is a type of propelled platform designed to deploy geophysical instruments for survey beneath sea.  The vehicle looks like a small torpedo and in our configuration has onboard a complex navigation system, sidescan-bathymetric sonar and a high resolution camera.  The sonar is used to map the seafloor and to obtain backscatter images of the features on the seafloor.  The camera can likewise be used to identify seafloor features and to mosaic complete maps of what is there. There are two big advantages of using AUVs over conventional surface-based survey methods.  The first is that by flying an AUV beneath the surface it will not be affected by the noise and motion of waves and thus be able to “fly” in a steadier manner.  The second is that it can be pre-programmed for the survey and launched from either a boat or the shore.  With a forward looking sonar onbaord for collision avoidance the AUV does all the work while you sit back and have a cup of coffee – at least that is what should happen in theory!

The AUV (named “Freya”) was brought to the site by a team from the Scottish Association for Marine Science out of Dunstaffnage (SAMS) and was part of a small grant awarded to us by the Marine Alliance for Science and Technology Scotland (MASTS).  For John Howe, Karen Wilson and Colin Abernethy it was a first for not only visiting Orkney but also for using the AUV on an archaeological project.   Time was split between surveying the loch of Harray, near to the Ring of Brodgar and Ness of Brodgar archaeological sites and surveying in the Bay of Firth close to areas where we have previously mapped and reported unusual features on the sea floor.

Context

The Rising Tides project has been investigating the area around the Ring of Brodgar for a number of years.  Most recently we have completed a full bathymetry and sub-bottom sonar survey of the loch of Stenness to the west.  The purpose of this work was to reconstruct the palaeo-landscapes and environments when the Ring of Brodgar and Ness of Brodgar were being built and used. What our work demonstrates is that the loch was smaller at that time and further that there was a complex history of sealevel rise associated with the infilling of sediments with a step change in sediment input coincident with changes in vegetation in the catchment at about 6ka BP. For more details on this see our publication “The environmentalcontext of the Neolithic monuments on the Brodgar Isthmus, Mainland, Orkney”

Caroline and I have also been experimenting with digital reconstructions for the area that can be seen on our test site "Ancient Lands" 

AUV in the Loch of Harray

In order to match the work in the loch of Stenness we brought the AUV to the loch of Harray.  This loch is a shallow, freshwater loch to the east of the Brodgar isthmus.  Previous surveying with the sub-bottom profiler showed it to not only very shallow at the southern end (less than 4m water depth), but also that the sediments were gas saturated for the most part.  Because of the very shallow water the AUV was not able to “fly” beneath the water and had to be operated as a surface vehicle.  This, combined with the fresh water challenged both the vehicle and the operations team to come up with novel ways of ensuring the AUV did not either crash into the bottom or into any of the small fishing vessels on site! Unfortunately, the weather also proved problematic with strong winds.  The vehicle was able to survey a few lines of data but the automated tracking features did not work correctly and so the vehicle did not manage to stay on course in order to survey a complete grid of data.

AUV in Bay of Firth

Following the tests in Harray (also useful because it was a confined loch and so there was no chance of the AUV being lost out to sea!) we took Freya to the Bay of Firth.  Here she was much more at home back in saltwater and also with a greater depth range to work in (up to 9m water depth).  A survey grid was programmed in the centre of the bay over areas where we have previously recorded and dived on unusual stone features.  Freya was deployed from a small rib and perfectly performed her planned mission of bathymetry mapping, sidescan sonar imaging and photography.  The preliminary results, processed within minutes of return to shore (another huge advantage over old methods of survey) showed a resolution that we had not seen before.  Fantastic new images of the seafloor which we will now ponder over before our return to dive on them in August.  Look out for results in a later post.

The AUV opens up a new era for us with archaeological survey.  There are so many sites that could benefit from this type of survey and many new and exciting discoveries to be made.

The AUV team with Richard and Caroline in Orkney - check out the renewable power sources!

 PS – on a historic note, the Gavia is approximately half the size (half the length and diameter) of the original WW I torpedoes and weighs about the same as the explosive head that these carried

Sanday, Orkney Core Sampling

The Storm Chasers are Back!

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

Seismic Data, Orkney

Previous Rising Tides Geophysics Results
Over the past couple of years we have been collecting bathymetry and sub-bottom seismic information from the Bay of Firth and Loch of Stenness.  These give us the first hint at palaeo-landscapes. 

Bathymetry in Bay of Firth showing deep inner basin

 The bathymetry information was acquired using a SEA Swathplus 468kHz sonar deployed on our department boat, Envoy and also on my specially adapted Zego Boat.  The sub-bottom information was acquired with a Sesistec Boomer system in the Bay of Firth and using a Tritech SeaKing Parametric Sonar on Loch of Stenness.

The results allow us to target areas of the seafloor that are rock and those of sediment.  The rock areas are investigated by ROV (remotely operated vehicle) or diver and the sediment by coring

Section of bathymetry from Loch of Stenness near Brodgar World Heritage Site

Sub-bottom profiles through stone features and sediment sequences in Stenness

Rising Tides - January Coring

Orkney - The Rising Tides Project

Its January and its Orkney - Coring on a new raft I have built in the Bay of Firth and the Loch of Stenness.  This is part of the Rising Tides Project, an archaeological study of how sealevel rise has inundated lost landscapes that were used by early settlers in Orkney during the Mesolithic and Neolithic.  

We have been working in Orkney for a number of years, as a multi-disciplinary team of archaeologists, geologists and geophysicists. For my part I have been acquiring geophysics of the sea floor and sub-seafloor sediments. Using this seismic information I am building models of submerged and buried surfaces that we will interpret as palaeo-landscapes once the others have done their work on the sediments.  Getting ground truth sediment has been quite a challenge but now armed with a new raft (a segmented, modular assembly from which we can operate a vibro-corer) we can acquire the necessary sediment cores to be able to analyse the environments that the geophysics has hinted at.  The cores are not only vital to interpretation of the geophysics but are a crucial step in trying to re-people the landscapes.  

So, first week in Jan and the raft arrives on site and is assembled.

Its all bolted together ad floated out.  Since its the maiden voyage a can of Guinness was sacrificed in the launch!

Out to site and the Vibro-corer is attached.

Perfect sediment record.

The whole exercise in both the Loch of Stenness and Bay of Firth caused a bit of a stir locally that prompted a Radio Orkney reporter to venture out

Its now back to the lab for core analysis of micro-fossils and sediment dating....more to report once all this is done