Mesolithic Scholar Happy to Get High

[More blog entries about archaeology, Mesolithic, Sweden; arkeologi, mesolitikum, jägarstenåldern, Stockholm.]

My old buddy from undergrad days, hard-core Mesolithic scholar, painter and woodsman Mattias Pettersson, sent me a pair of wonderful breathless letters on 19 and 21 July about new high-end discoveries. This is all about ancient seal-hunting camps in an area with dramatic shore displacement, which is why Mattias is so happy to get high -- 75 meters above current sea level! High means early here, so early that the top sites are pushing the chronological limit set by the last Ice Age. (More context & pix here). I quote (and translate) with Mattias's permission:

19 July.

The Tyresta project is limping on with sporadic work. Roger has been up to #121 and dug squares and I've started at Björkkärren ["the birch bogs"]. Quarter-square-meters every second meter across site 28, a sandy incline toward a fen at 60 m a.s.l. I've also marked out squares (on every meter) at another site on 65 m a.s.l. in the same area.

But here's the coolest development: I took a walk during "lunch" and scaled Tyresta's highest hilltop, 85 m a.s.l., a stone's throw from the aforementioned site 28. There's a great location up there that we've been planning to test-pit: a protected harbour inlet at 75 m a.s.l. The island [i.e. the current hilltop] was 250 m long and the second largest in the Tyresta archipelago of that era, which consisted only of a few dispersed islets. You can't dig in the normal way, having instead to hack down between the stones in the washed-out ground. A first try at the bottom of the inlet was fruitless; just a lot of boulders with peat between them. If you knapped quartz there it would just fall uselessly between the stones and it would have been damned uncomfortable. I started to go back to the dig, but I caught sight of a washed-out shingle ridge at the inner end of the inlet, right below the 85-meter-curve, where Roger, Janne and I stood in the spring measuring the level with GPS: 76 m a.s.l. "I wonder what it's like to stand in there", I mused. Standing on the shingles, I started to wonder where you could sit down. "Where can I find a non-lumpy surface?" So I found one and started pawing down between the boulders. I was pleased (and increasingly excited) to find yellow sand, not just erosion gravel. Original sediment! In some mysterious way, this sand had survived the heavy wave action. I dug as if in a trance, and suddenly something glinted -- unbelievably: quartz, super quality quartz! A few more scrapes with the trowel at the same spot, and three more chips! I howled and pinched myself in the arm.

The following day I returned, cleaning up and sieving the sand I had shifted. No more quartz chips there, but toward the escarpment under fallen trees and dense underbrush (I had to crawl in) there was another non-lumpy surface. A tiny test pit dug with a trowel near the edge of the surface gave an incredible seven quartz chips, all of the same super quality! Every poke with the trowel dislodged another chip and I soon restrained myself to keep from destroying more context.

This site is a crown jewel, as Roger put it on the phone. Over the past week he's been walking around mumbling like a mantra: 75, 75, 75... Before returning to my family duties, I have to ask: is this a shoreline site or have these people gone in from a slightly lower shoreline? The shore right at the base of the shingle ridge is a great location, but when the shoreline was farther down, say, at 70, they may have gone in and hung out on this surface that was (at the time) nice and sheltered in the island's interior and right by the lookout spot at the top of the 85er. And still not inconveniently far from the boats. Maybe there are components both of early and later visits? Anyway, it's a site to make your head spin and I think there will be a few test pits later this summer.

21 July.

They chose to sit on the washed-out moraine because it was elevated above the bottom of the little lagoon, being drier and nicer. The lower parts of the little vale were probably wet or too rocky. The flat cliffs surrounding it were also useful, but it would have been harder to erect tents etc. there, and if you put your tent on a rock surface you'll get rain water flowing through it [...] (unless you make a little dyke of impermeable material or build yourself a raised floor). But why go to all the trouble when there's good moraine around? It was easy to stick poles securely into it for various purposes and with a bit of muscle you could reorganise the boulders and make nice non-lumpy "hut floors" to "settle" on. Any sparse vegetation (wormwood, Sw. malört, stunted birch or what-have-you) would have provided some protection against the wind. Next time we'll check methodically for such structures.

As I said, the location may have been good at a lower sea level as well. The island held a particular attraction with its peak, the highest one in the area. Such attraction would have remained until the sea had receded to a level where the landscape knitted together enough that you could no longer look for seal from the hilltop. Then (I imagine) the hilltop would only have had a sentimental worth and perhaps lived on in people's minds as "the seal lookout of the ancestors" or so. And if we want to stick to evidence-based archaeology, supposing that the quartz has been deposited for entirely prosaic reasons (sorry, Hodder), then the peak loses its purely economic importance about a shoreline level of 65-60 m a.s.l.

Looking at the rest of the island, we have good landing sites with quartz at 65 and 60, so at that time there was apparently no need to look for inland settlement spots. At 70, though, there aren't any really good landing coves, (actually better at 75 with the known inlet), and so it seems plausible that the find-yielding site belongs to this level and wouldn't have been directly tied to the shore. Possibly the quartz belongs both to when the shore was at 75 and to later visits through the period until it reached the next level with new good inlets. If there are any cleaned-up hut floors in the rock jumble, then these would have been useful for a long time. Maybe that's why there's such an extreme find density at least in certain spots? Veeery exciting!

Roger is out kayaking with Angelica (currently somewhere around Nåttarö). He calls me from time to time and tries my patience with exciting discoveries in the inner parts of remote islands -- know what I mean!? A pick strapped to the aft deck, sun glare and gravelly shores. Aaargh!

Update 8 August: Comments Mattias:

Here comes a discussion on the dating of the site:

We have, the site being newly found, no absolute dates. However, since the place exhibits terrain qualities typical of shore-bound sites (see above), a hypothetical shore-line dating can be made.

In shoreline-dating, the date is read graphically from a shore-displacement graph. In this case, a model published by Jan Risberg in 2003 is used. The site's level above the present shore-line, 76 m, would give a dating to c. 8,500 radiocarbon years BP, that is, 7500 cal BC.

However, there are many uncertainties about the graph. The standstill (seen as a "plateau" in the graph around 80 m a.s.l.) during the early Ancylus Lake phase of the Baltic is probably correct, but its duration is too long, which is especially apparent when one calibrates the curve's dates [some bits of the graph's time axis get stretched, others compressed]. This too prolonged standstill does not fit with recent models and gives little space for the regression down to the levels of the early Littorina Sea. The curve has a very fast regression from 75 down to 60 m a.s.l. in only 200 years, between c. 7500 and 7300 cal BC. We would like to propose an alternative curve, following new theories about what happened in the Ancylus Lake's outlet in today's Store Baelt area. There is still a consensus that the enormous freshwater lake was finally drained here and that the outlet river rather rapidly (geologically speaking) eroded into soft sediments, creating a (now submerged) canyon and causing a lowering of the Baltic's surface. But in the new models, in contrast to earlier ones, the lowering is only about 5 m over a period of 200 years: a less dramatic lowering of the Baltic's level than the catastrophic event previously often put forth. This lowering is believed to have taken place slightly before 8000 cal BC. This would, returning to the Stockholm area, give an earlier end to the Ancylus transgression plateau than in Risberg's 2003 graph, followed by a fast regression of c. 5 m over 200 years and then a not-that-rapid regression over 1,000 years, during which the shore-displacement gradually decreased to the very slow rate (or slight transgression) of the early Littorina Sea. Are you following me?

Briefly put, for the site in question, if it was situated immediately at the shore-line, 75 m a.s.l., it would give a dating to around 8000 cal BC. Furthermore, it would affect the shore-line dates of all sites between 60 and 75 m a.s.l.

The position of the shore-line at c. 75 m a.s.l. around 8000 fits well with the isolation date of a certain bog, Gladö some 20 km west of Tyresta. This is the only basin in Anna Hedenström's (1996) study of Preboreal shore-displacement, where macro-fossils were dated (in the other basins in the study, dating was conducted on bulk sediment).

In some recent studies, Jan Risberg has successfully used birch seeds for dating, and we hope that in the near future, money could be raised for the purpose of a renewed study of the area's earliest shore displacement