Saturday, August 9, 2008

Prehistoric Sites Along Port Tobacco Creek

Yesterday Pete wrote about our traveling exhibit which will debut at the Charles County fair next month. It will include artifacts, maps illustrating the distribution of those artifacts, and a variety of historical photographs and maps. The map below shows the locations of prehistoric sites that we identified and mapped.

We are using this map and some of the artifacts on which it is based to illustrate something interesting that we learned and that relates to the exhibit and the project at large. Seven of the eight sites date to the Late Archaic period. (The northernmost, which we tested during the spring field session is Late Woodland, and possibly Contact period.) The fact that these sites survive in the floodplain and retain their cohesion (we could define their limits on the ground, they had not been washed away by floodwaters) indicates that the stream channel has not meandered outside of its current channel at least since approximately 1000 BC to 3000 BC.

Why is that important? The stability of the stream channel suggests that the process of sedimentation that denied the town access to navigable water before the Civil War, and as early as the late 18th century, had not begun until after European settlement. Significant deposits of silt would have altered stream flow. The distribution of prehistoric artifacts parallel to the current channel supports the hypothesis that sedimentation occurred during the historic period and likely as a result of specific activities, principally farming and urban development.

If sedimentation occurred during the historic period, and it was due mainly to runoff from surrounding farms and streetscapes, the residents must have known what was happening and foreseen the consequences for the port town and its economy. What, if anything, did they do about it?

We will not rest on this data, but will continue to find and analyze evidence on the sources and timing of sedimentation events. Our assessment of the data to date will appear in the traveling exhibit. We'll post new observations as we proceed with the analysis of data collected during the June field session.


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