This week in lab, I had the opportunity to begin the creation of our second trench at the hypothesized quarry site. We narrowed down our interests to two possible locations, the first the trash dump in L10 and the second the ridge of the site. We decided to begin excavation at the trash dump in order to hopefully find some stratification of the same sort of trash we were finding on the surface in order to better understand the chronological history of the site and it’s uses. By the end of lab, we had finally finished clearing the surface, collecting a lot more artifacts and trash than had been collected before and then beginning to go deeper exploring the first strata of the area. That first strata was composed of a dark rich topsoil which contained many roots. It also had some presence of artifacts along with a clear trend of charcoal on the half of the trench which ran through the trash pit now seen as a fire circle. In fact, this had not at all been our initial intention. We at first thought that a 2×2 m trench would be most effective because it would fully cover the fire circle along with enough of its surroundings to get a clear picture of the edges. However, Alex showed us how this was not actually the most effective and efficient method because we could still get a representative sample of the fire pit trash dump by taking a cross section of it and reducing our trench to 2×1 m halving the amount of work required. This would also give us a clear stratigraphy of the site because one edge of the trench would go right through the middle of the pit. We were not able to finish fully excavating the top soil by the end of the day; however, we did run into an interesting flat layer of rock along with a new soil horizon causing progress to slow down as we were approaching a new stratigraphic unit.
This week, we began to fully explore the site of a potential quarry which we were shown in week 2. The Tuesday group got there first and began by creating a basic sketch map of the area along with 16 survey units in a 4×4 grid. We began the day by splitting up into groups with the majority of the class pairing off in order to actually survey the units created by the Tuesday lab with a small group of which I was a part of splintering off in order to use DGPS mapping to begin to create a detailed topographic map of the site. The survey group surveyed a total of 8 different units throughout the lab finding mostly glass fragments and metal from cans. This is because after the hypothesized quarry the site began to be used as a student party spot so there was a clear presence of the remnants of alcohol containers on the surface. The mapping group began the day by setting up the DGPS so that it was set to ping its location off of satellites in order to record a clear picture of where the end of the device was when a point was taken. After calibration, we began actually collecting data with the points marking out the corners of the survey units. This seemed like a fairly easy task, in practice however, it became quite difficult and thought intensive. This is because each flag used to mark the corner of a survey unit was in fact the corner of up to four separate units and because we did not begin systematically in rows quickly became confusing which flags we had already recorded and had yet to record. In the end, we were able to successfully finish up the survey unit boundaries by labeling them by which corner of the square they were a part of. After collecting data on the grid, we began to take a look at the natural landscape of the quarry. The place we began and had to end halfway due to the time constraints of the lab was the lower wall of the quarry face where we were hoping to collect clear topographic data showing how the rock was cut regularly at unnatural angles.
This week we had the opportunity to practice surveying a field in the arb across from the driving range. We did not know of any previous use of the land so it is understandable that we didn’t find any record of previous inhabitation; however, we did discover a strange and interesting phenomenon. There were golf balls in the field. This at first seemed very odd until we realized that they had to have been coming from the driving range. In order to better understand how they were distributed, we later mapped the distribution of the golf balls by survey unit leading to an interesting albeit predictable pattern. They radiated outwards from the driving range with the closest directly across from it, and the least diagonal and farther away from it. Although we have no idea why the golf balls were being hit in the opposite direction from where they were supposed to be, they did give us the opportunity to practice our map making skills using Google Earth to create survey units and then color code them based on the density of our finds. These same density maps were also created based off of total artifacts found and collected. It also taught us some of the quirks and problems with using Google Earth Pro, because the program’s distance measuring is not entirely accurate leading to some of our survey units appearing much longer or narrower than they actually were. Another oddity discovered from our survey was the presence of small white marine shells in the middle of the field. We suspect that because they were only found intact that they must have been deposited fairly recently because they are quite delicate; however, we have no explanation for how or why they were actually deposited.
This week, we explored the arb with its director, Nancy Braker. We began with a brief history of the the arb from Nancy, beginning with its initial founding by a Carleton biology professor interested in having a space to conduct research on woody plants. At the time, this was a relatively new proposition as it was one of the first arboretums in the “West,” as Minnesota was termed at the time. In fact, it even came before major natural resource sites in Chicago, a much larger city. From our starting point at the arb office, we traversed the arb reaching the notable sites of the old Waterford Mill, Women’s League Cabin, and Pine Hill Village, the sites of previous archaeological research performed by ARCN 246 students. In order to reach Waterford Mill, we travelled along a dike, a long human built elevated mound of soil built to help block off water and force it to flow through the Cannon river.
Along the way, we also had the opportunity to see records of Minnesota’s surface geological processes. Specifically, the records of ancient glaciation long receded, but which has clearly shaped surface topography. The most obvious example of a glacial record in the arb is in Kettle Hole Marsh, a large depression formed after the melting of trapped ice left behind by a receding glacier and incorporated into the surrounding sediments which when it eventually melted, left the depression in which the marsh formed. The other sign of historic glaciation which we were able to observe on this outing was the presence of large igneous and metamorphic basement rocks of boulder size randomly appearing on the surface without any exposed bedrock. These boulders were in fact broken away from the plutons where they formed and moved by glaciers. However, when the glaciers eventually receded and melted, all the sediments they were carrying were deposited, including massive igneous and metamorphic boulders which otherwise would not be able to be transported by natural processes.