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Saint Pierre-Eynac: studying a silcrete source

It's been a little while since I last wrote about my postdoc project, mainly because of finishing (or almost finishing) fieldwork, and then coming back to Bordeaux to get moved in. Various other complications have meant I've been ridiculously busy the past few weeks.
My last post, all about silcrete, was an introduction to what I'm doing, so this post will give a bit more detail about the site I'm working on: Saint Pierre-Eynac, and the field techniques we are planning.

What feels like rather a long time ago, even though it's only a few weeks, I had my first visit to the place which will be the focus of my postdoc research. This is the silcrete source at Saint Pierre-Eynac, near Le Puy-en-Velay, in the Haute-Loire [if you're a bit fuzzy on what exactly silcrete is, check out my last post all about this interesting type of stone].
I had one of those cool experiences when you go somewhere you've heard or read about, and being there suddenly gives you a really good vibe- lucky really, as this is what I need to be excited about for the next 2 years!


The site is now a hill covered in old forest plantation and looks very pretty, especially in low sun. However, as I explained in the last post, it didn't always look like this, and we still don't have a full understanding of the formation context of the silcretes here.
When we visited the site, it was raining and we'd already spent most of the day looking at volcanic geology in the region so we didn't have a lot of time. I'm going back again next week with the geological expert, Michel Piboule, so hopefully I'll learn a lot more then. In the mean time, here are some photos I took at one of the outcrops on the hill.

Walking up the path, lots of the material in the gravel track is silcrete

One of the silcrete outcrops, effectively a small cliff-like formation now but formation may have been involved with faulting

Closer in to the outcrop; some of the fresh areas might be natural thermal fracturing as the Massif Central has very cold winters, but it may also be due to people going up and removing material, whether for geological reasons or not

Another look at part of the outcrop, less fresh, but the impression is still of quite pale rock, despite the great variability observed within the collections

Close-up of a greyer fresh fracture, showing internal variation

Close-up of a fractured area, showing the fine-grained structure of some of the silcrete, as well as some conchoidal rings from energy passing through. The stone is shiny because it was raining, but the wetness shows the good quality well.

Another freshly fractured part (this time by me, taking a sample), again showing the fine-grained aspect of the stone, and some ripples that formed during the fracture.
Hopefully the photos from the field show several things. First, the silcrete really is, at least in some parts of the outcrops, pretty decent quality stone, which readily knaps. Second, much of it is a pale colour, often whitish-grey (although the material collected from the surface of the hill is variable). Third, although there are a couple of fields on the slopes of the hill (see first photo) the current landscape conditions further up are rather tricky for working in- quite heavily wooded in places, with a lot of ground vegetation. Here's another photo showing this:

Tricky fieldwork conditions
This is a problem as we've now decided that one of the primary foci for the project will be to survey the Saint Pierre-Eynac hill properly for the first time.  This is both to get a proper understanding of the geology and locations of the outcrops, but also to gain a detailed picture of what people were doing in the Palaeolithic when they came here to source silcrete.

While local collectors have picked up material from the surface- especially the fields- for a long time, this has not been done systematically, and for archaeology, the context of finds like stone tools is everything. At Saint Pierre-Eynac, we know that people are using the silcrete from the Middle Palaeolithic (Neandertals) through the Upper Palaeolithic (anatomically modern people), both because of the type of tools within the collections from the hill, and also because of material identified within stratified layers at dated cave sites. If we want to understand the source itself as an important place, trying to disentangle different behaviour through time from collections of mixed ages is very difficult.

This is the material collected locally but without any spatial data- it can only tell us so much.

One piece from the collection, covered in old lichen- it's definitely been lying on the surface for a good while! The little bulging lip visible towards the centre of the artefact is a result of being struck with a stone hammer, and is one of the indicators showing this is humanly made.
This is why we need to collect more material, but in a way which preserves the information about where it came from on the hill. If we can get spatial data, it allows us to start looking at whether different aged stone tools are found in different areas, if different activities were happening in particular places, and maybe even see if outcrops were being exploited in different ways.  While I was away for a week from the field (back in Bordeaux waiting for all our furniture to be delivered!), the rest of the team back in the Massif Central went out and did the first proper surface survey. They collected material from along a 200m line going roughly up the side of the hill, and the result can be seen in the two pictures below: a LOT of stones for me to process!

The large (and heavy!) bags and buckets of stones collected on the 200m transect.

The stones, bagged according to 10m height intervals, ready to be washed in the lab at the field centre.
This meant an awful lot of washing for me! I've made a start (and you can see one 10 m interval all washed, dried and bagged up in the photo below), but there's still a lot left. I'll be getting on with that when I return to the field station this week.


Although the team purposefully picked up virtually everything they could see that wasn't obviously just a rock, it's surprising how much appears to be real artefacts and not just naturally fractured. In amongst the hundreds of pieces I've washed so far, there are some really nice lithics, for example this very small and finely worked core. On this piece the end facing you has been carefully prepared with tiny removals so a big flake can be stuck from it, leaving the large bowl shaped scar across the top.

Very nice small core from one of the survey transects

As well as more targetted surface collection, including around the outcrops as well as the slopes, we are hoping to do a landscape survey of the whole hill using the VERY cool LIDAR technology- essentially that's where we pay someone to fly an aeroplane over the site and shoot down a laser which measures the topography really accurately, even in situations like ours where the surface is covered in trees. This will help us map out the outcrops and landforms of the hill, and also give us a high quality map to plot the surface collection transects on.
After this, we're hoping to get permission to do some excavation next summer, probably in the field in the first photograph, to try and determine if there is any stratigraphy at all- if we can find layers within the soil containing artefacts of different ages, this will really help us understand how use of the silcrete source might have changed over time.

More blog updates will come soon, including some very cool photos from the days I spent with Paul Fernandes learning his techniques for identifying silcrete and other types of silex/flint- using microscopes!

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