Coastal (Geo)Archaeology on my Mind

Human occupation and coastlines have a long, but not very well-understood history. Global sea level has fallen and subsequently risen by over 120m during the last glacial cycle (~132,000 years), driven by fluctuations of the masses of ice sheets. These changing coastal landscapes have produced, or take away, opportunities for humans to exploit the resources they offer. In early prehistory, the use of coastal resources has been argued to have facilitated the dispersal of hominins out of Africa and across the globe and/or aided the development of fully modern human brains and behaviours, as well as providing resources to support specialised, marine-focussed ways of life in later prehistory. Coastal archaeology is therefore at the forefront of some of archaeology’s ‘Big Questions’. Yet it’s not just about understanding the past – studies of past sea level change, and the location and survey of ‘benchmarks’ left by these sea levels, helps us to better predict how, in a world of rising seas, the hundreds of millions of people who live along coastlines will be impacted in the coming decades.

The Greek Islands. Someone has to work there… Photo: R. Inglis.

My month has been decidedly more coastal than usual in theme, and not just because I’m pining after my recent holiday in Western Australia. Working backwards from today, this week I have been analysing sediments from excavations at a Neanderthal cave site on one of the Ionian Islands, Greece. During periods of low sea level, the area around the island would have been very different, with lagoons and wetlands and all the marine resources they would have contained in the area now covered by sea. Investigations on land and underwater are being carried out in order to understand more about how the landscape changed over time, and how this affected the humans and Neanderthals who left archaeology within it.

After a week making thin sections of some of the sediments (#TBT my 2016 DoA post on how and why to make thin sections), I’ve been running particle size analysis on the sediments from the cave in order to learn more about how these sediments got to where they did, and how these site formation processes impacted the archaeology within them. Of course, things are never straightforward, and getting the stony clay samples sieved and prepared for analysis was about as pleasant as excavating through them had been, involving wet sieving, muck, and ovens – I may even have to change tack and restart the whole thing. So to be honest, I’m not in the mood to talk more about them just yet…thank goodness it’s Friday!

Sediments on their way to becoming the worst brownies ever baked – in the oven overnight at 110ºC. Photo: R. Inglis.

The Mastersizer in motion! The particle size distribution curve, showing the number of particles in each size class can be see on the graph on the screen. Photo: R. Inglis.

Also in the batch were more straightforward sandy samples (though obviously not THAT straightforward, this is applied science…) from southwest Saudi Arabia, the study area for my current project, SURFACE. With these sediments, taken from a fossil beach and dune complex that formed during a period of higher sea level (Dhahaban Quarry – learn more here), I was using Particle Size Analysis (PSA) to distinguish between shallow marine sediments and the windblown dune sediments – the transition from one to the other would mark the highest point of past sea level, thus providing a sea level ‘benchmark’. It worked after a fashion – the aeolian sediments appear to be ‘well-sorted’ e.g. all one size class, what you’d expect from a dune, and the muddy lagoonal sediments were, well, a muddy mix of all particle sizes. Still more work to be done, but it’s encouraging!

Shallow marine sediments at Dhahaban Quarry, now approximately 5m above sea level. The holes are for samples taken for optically stimulated luminescence (OSL) dating. Photo: R. Inglis.

Away from the lab, and the muck, and the clay (which actually maybe predominantly fine silt – who knew!), coasts still dominate my to-do list. I’m wrestling with reviewer revisions on a book chapter presenting the field survey of the coral and marine terraces that are along the coastline of the volcanic Harrat Al Birk, SW Saudi Arabia, including the Dhahaban Quarry site, which we undertook in December 2014. Through this detailed survey of the marine terraces, and future dating of the corals that are found within them, we will learn more about the position of the past coastline that created them. This has geological implications for understanding the opening of the Red Sea Rift, (which is pushing its western and eastern coastlines up and out), helps us to place the archaeology we find on land in its relationship to the sea and potential use of coastal resources, and is another data point to underpin future sea level predictions.

The final piece of coastal news this week is the publication, after a looong process, of a paper by the MEDFLOOD community, which takes a long-term view of sea level change and human occupation and use of coastal regions in the Mediterranean (the last 132,000 years). It’s chock-full of methodological data on measuring sea level, evidence for the use of coastal resources by Neanderthals and humans up to the historic period, and areas in which new research, both underwater and on land, needs to be undertaken. A superb effort to bring together this diverse group of researchers with different approaches.

MEDFLOOD meetings are always held in challenging locations, such as the Northern Adriatic, close to Venice. Photo: R. Inglis.

So there you have it. From very challenging lab work to writing to that sweet feeling of seeing a paper finally published, almost the full cycle of coastal research. I’ll wind up this post by wishing you a happy Day of Archaeology 2017, and leave you with this thought from Coastal Archaeologist extraordinaire Prof. Geoff Bailey (tweeted to the world by MEDFLOOD’s Dr Alessio Rovere):

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