I’m just wrapping up a report on some field stone piles, and thought it might be worth a brief post.
Field stone piles are, of course ubiquitous in cultivated fields. Sometimes they are obviously of recent origin, sometimes it is hard to tell. The problem out here on the Plains is that Native American peoples have built and used cairns for a variety of reasons (including burials). When we do an archaeological survey, we want to be carefully not to write a cairn off as a field stone pile. Aggravating this issue has been the mixed rigor and accuracy of field stone pile identification in standard archaeological surveys. Universities don’t teach seminars on field stone piles, and in fieldwork (by necessity) we record them pretty quickly. I have seen cases where piles that were obviously made with a bulldozer are identified as prehistoric cairns, and I’ve seen cairns written off as field stone piles.
The North Dakota Department of Transportation is now requiring a survey of field stone piles that have been sold for use as road fill [this happens fairly frequently]. A few times in the recent past, construction equipment has revealed that what everyone assumed was a field stone pile was a cairn (and a burial). Much of this re-evaluation is being driven by Tribal Historic Preservation Offices (especially at the Standing Rock Sioux Tribe and Sisseton-Wahpeton Oyate).
So here is how I inventory field stone piles and cairns. As context, you should know I have spent a fair amount of time working with Tribal representatives recording stone features; I’ve learned a great deal from them. For each pile I record the height of the pile, the smallest rock size, the largest rock size and the median rock size. By looking at these I am trying to figure out whether the pile was made with the assistance of heavy machinery. If there are lots of boulders, for example, that means machinery. The median rock size is critical. Median sizes of 20-30cm are a red flag, as that is a typical size for Native American cairns. Smallest rock size can also indicate the use of recent rock-picking or digging, if they are under 2ocm. While I am doing this, I am also looking at weathering and lichens; do any of the rocks look like they have been recently turned or moved? Sod development around the pile is also a clue. If there is none, the pile is probably recent. If the rocks are almost covered by sod, it probably is old.
I also look a the placement of the rock piles in and around cultivated fields. If they are on roads or section lines, that may indicate that they are recent. If they are on ridge lines or midslope, that may mean they predate agriculture. Note the may. Cairns can wind up on section lines just by chance. The first generation farmers sometimes left piles on slopes and hilltops, because that was the best they could do. Complicating this issue is the tendency of humans to pile rocks on rocks. Farmers and Native Americans placed piles/cairns on natural boulder lag piles. Farmers also sometimes expand a cairn into a field stone pile. The feature that worries me most is a cairn buried completely under a huge field stone pile; I have no way to identify those.
So using the techniques above and a few more things I don’t have time to write up, I make a judgment call: historic field stone pile, Native American stone feature, both, or I dunno (meaning more research needed). The problem is there is no way to tell for sure (as an archaeologist) what is under a stone pile unless I take it apart and look. That would a)take forever and cost a fortune and b)eventually get me in real trouble (and cost me some friends). If a rock pile turned out to be a burial cairn, I’ll would find that out by desecrating the grave. So I make the best identification I can, err on the side of caution, throw in some disclaimers, and hope for the best.
The top two photos are agricultural field stone piles (in ND), the photo below is a Native American cairn (in SD).