Posted by: Jonathan Fowler | May 15, 2015

Operation View Park: Part 1

View north from the hay field overlooking the memorial church at Grand-Pré National Historic Site. Are there archaeological remains underfoot?

View north from the hay field overlooking the memorial church at Grand-Pré National Historic Site, with Cape Blomidon in the distance. Are there archaeological remains underfoot?

As noted in our last post, the first goal of our very busy 2015 season was to geophysically survey the large field recently added to Grand-Pré National Historic Site. Overlooking the memorial church and its surrounding gardens, this field is comparatively undeveloped, and is currently being rented for its hay crop.

But this open field must surely have been close to the bustling centre of the pre-Deportation settlement, where Charles Morris in the late 1740s observed “about 150 houses scatter’d on several small Hills.”

Any buildings that escaped the 1755 Deportation were either dismantled or repurposed by the New England colonists who took up these devastated lands in the 1760s, while the survivors, sporadically mentioned in folklore, seem to have since gone to pieces. Subterranean features may be all that remain, but these backfilled cellars, ditches, wells, and fence lines are the archaeologist’s stock in trade.

To begin the effort of building an archaeological resource inventory of the view park field, we conducted an extensive geophysical survey with our old workhorse, the Geonics EM38B. As described in previous posts, and as detailed in some of the publications in our Readings and Resources section, this instrument measures magnetic susceptibility (how easily the ground is magnetized) and electrical conductivity (how easily the ground conducts electricity), both of which properties can reveal important insights about archaeological features. The instrument is most effective in measuring the upper 50cm (20 inches) of the soil profile, which is actually where most of our evidence is found.

Deploying the EM38 requires the operator – in this case, our student archaeologists – to walk a series of parallel lines across the survey area. The data collected along these lines are later computer processed to create contour maps, which may guide us to areas of interest for higher resolution geophysical surveys (to map the anomalies in greater detail), and ultimately to archaeological test excavations (to determine what is causing the anomalous readings).

The view park field represented something of a challenge on account of its size. Measuring approximately 200m x 400m (or 656′ x 1312′), this area required a lot of footwork even with our transect intervals spaced at a relatively coarse 2m (ca. 6.5′). Not counting the steps required to set up our survey grids or to move equipment around the field, the survey team was required to walk an ambitious 40km (ca. 25 miles) of transects during the four days it took us to complete the survey.

Saint Mary's Archaeological Field School students receiving instruction on the use of a total station to map archaeological features and geophysical survey grids. (Greg is awesome).

Saint Mary’s Archaeological Field School students receiving instruction on the use of a total station to map archaeological features and geophysical survey grids. (Greg is awesome).

Large scale geophysical surveys like the kind recently undertaken at Stonehenge are increasingly motorized and commonly employ global positioning systems (GPS) to maintain spatial control. We are currently looking into acquiring these technologies, but for the present we are relying on traditional (i.e. pedestrian) methods, which to date have been well suited to the smaller areas we have been tackling, and at any rate are easily mapped with a total station. At 8ha (20 acres), though, the view park field may be approaching the threshold of what we might prefer to investigate with a towed array.

For this survey, we established our survey grids by measuring from a baseline established along the eastern boundary of the field. This field boundary has been in existence from at least ca. 1761, when immigrants from Connecticut began to refashion the old French properties of Grand-Pré into a New England township called Horton, so it had the benefit of conveniently anchoring our units of study to a veritable component of the colonial landscape.

Next, we had to come up with a method that would enable our survey team to walk more-or-less parallel transects across the 200m (656′) width of open field. The course we adopted after some discussion was to erect three range poles along each survey line: one at the east end, one mid-field, and one at the west end. So long as the person carrying the instrument took care to maintain a position in visual alignment with the poles, or with the end pole and some other feature on the horizon, the transect should be accurately aligned. Additional guidance, if needed, was signalled by crew members stationed at the range poles.

Geophysical survey team moving down range as seen from the midfield range pole (camera facing west).

Geophysical survey team moving down range as seen from the midfield range pole (camera facing west). Though you can’t see it in the photo, Hannah – with her back to us here – had a device in her backpack playing show tunes. Whenever the survey team approached she would discretely move her range pole and her electromagnetic field to one side.

To further ensure spatial control along each parallel survey line, the we inserted fiducial markers (aka “fids”) in the data stream every five metres (ca. 16.5′). Here the instrument operator took her or his lead from a teammate (affectionately called the “wheelie”) who walked alongside – just out of magnetic range – with a measuring wheel, and who kept pace and maintained alignment during the brisk stroll back and forth across the field, all the while squinting at the counter and calling out the progressively stupefying chant of “one-two-three-four-FID!” A kilometre or so of this brings one to a state that is equal parts cardio workout and mesmerism. Next time we’ll tape an infomercial.

The final member of the survey team is a note-taker, whose job it is to tally the fids and record anything out of the ordinary along the transects (e.g. operator stumbled at fid 13; metal fence post at end of line 40). These notes are occasionally very helpful when the time comes to sort through tens or even hundreds of thousands of readings to isolate those often subtle hints and traces arising from archaeological sources.

With our method in place, then, we set to work.

One of our geophysical survey teams: Todd, Candice, and Jennifer, ready to roll.

One of our geophysical survey teams: Todd (instrument operator), Candice (wheelie), and Jennifer (note-taker), ready to roll. Camera facing northwest.

 

 

 

 

 

Posted by: Jonathan Fowler | May 2, 2015

2015 Field Season Begins

Archaeological survey at Grand-Pré, spring 2015

Archaeological survey at Grand-Pré, spring 2015

Nova Scotia’s weather, temperamental at the best of times, occasionally settles into periods of unrestrained malice. So it was during the punishing winter of 2015 and the succeeding season, which elsewhere is called spring. Having set our field schedule months in advance, we were unable to avoid what faced us when we arrived at Grand-Pré National Historic Site on April 24th.

Spring at Grand-Pré National Historic Site!

Spring at Grand-Pré National Historic Site! (Camera facing west, soul facing south).

A persistent foot of snow covered the site in a wet blanket, only here and there giving way to waterlogged earth. Perched by the roadside behind the memorial church a defiant mass of snow, six feet high, held fast against the lengthening days. Just 10 days earlier, meltwater had threatened to flood Dyke Road, the ribbon of asphalt spanning the Grand-Pré Marsh, tieing Long Island to the mainland. You just can’t dig properly in these conditions, and since we had planned to focus on archaeological geophysics this season anyway, we made a virtue of necessity and focused on the hillside overlooking the garden portion of the national historic site.

Our 2015 survey area at Grand-Pré National Historic Site (outlined), just north of the new view park. Image adapted from GoogleEarth. The location of the webcam is indicated by the yellow dot.

Our 2015 survey area at Grand-Pré National Historic Site (outlined), just north of the new view park. Image adapted from GoogleEarth. The location of the webcam is indicated by the yellow dot.

This area had been added to the national historic site in 2011 thanks to funds raised through donations and matched by the federal government. A fabulous view park has since been constructed at the south end of the property, accessed by The Old Post Road, offering visitors an unparalleled vantage of the national historic site and its iconic landscape. (If you can’t make the drive, check out the webcam, which transmits live updates several times every minute). Most of the newly acquired land is archaeological terra incognita, but now, blown clear of snow by the famous Grand-Pré winds, it presented itself as the only viable target for our team of student archaeologists.

This was a case of archaeological survey, which in this instance may be loosely defined as an investigative process whose purpose is the detection and preliminary identification of archaeological sites. Ordinarily, large areas like this one (our survey area consisted of approximately 8 hectares, or 20 acres) can be effectively surveyed on foot if the ground has been tilled, but our field was covered by turf, which concealed the fragments of ceramics, glass, and other telltale signs of past occupation. Had we more time, or perhaps a legion of diggers, systematic test pitting could pinpoint former activity areas, but even this commonly used method purchases information at the cost of altering the archaeological record.

Given these conditions, we opted for geophysics…

 

 

Posted by: Jonathan Fowler | July 27, 2014

Is This John Winslow’s Wall?

Stone cross built by John Frederic Herbin over a century ago to mark the location of the pre-Deportation Acadian cemetery at Grand-Pré. SOURCE: Parks Canada.

Stone cross built by John Frederic Herbin over a century ago to mark the location of the pre-Deportation Acadian cemetery at Grand-Pré. IMAGE: Herbin’s Cross ca. 1916 (camera facing east), Parks Canada.

In the late summer of 1755, Lieut. Col. John Winslow’s New England troops arrived at Grand-Pré. Winslow’s orders were to deport the French inhabitants, but the precise means by which he was to effect this policy were left to him. While he weighed his options, and while the local people made plans for the harvest, Winslow set his men to work constructing a wooden palisade around his camp. The completed stockade enclosed the parish church of St-Charles-des-Mines, the priest’s house, which Winslow now occupied as his own quarters, another neighbouring dwelling, and the parish cemetery. In Winslow’s mind, the completed circuit of sharpened posts secured his camp against the kind of surprise attack that had decimated Arthur Noble’s men during the Battle of Grand-Pré in 1747.

‘Winslow’s wall’ has been an archaeological target since our project began in 2000. Above ground, the palisade line itself has naturally vanished without a trace. I’ve never seen any reference to it in historical documents or maps after 1755, though presumably it was left standing when the last of Winslow’s men abandoned the site in January, 1756. Did the New Englander colonists, who took possession of these lands in the summer of 1760, encounter the tottering line of weathered pickets, or had others removed them in the intervening years? We may never know.

Beneath the sod, though, traces of Winslow’s palisade may still remain in the form of archaeological features, in this case a soil stain marking the line of narrow trench dug by the soldiers to receive the contiguous line of timber posts. Winslow, in his orderly book, refers to the digging of this socket trench and, supposing his men did their job reasonably well, even the back-filled line with the pickets removed should be visible as a continuous soil stain against the otherwise uniform sub-soil.

Saint Mary's University archaeology students record features during test excavations east of Herbin's Cross in May, 2014.

Saint Mary’s University archaeology students record features during test excavations east of Herbin’s Cross in May, 2014. Camera facing west.

Our 2014 excavations at Grand-Pré National Historic Site were aimed at detecting traces of Winslow’s palisade by introducing excavation units in a line extending east of Herbin’s Cross, which marks the location of the pre-Deportation cemetery. By removing the disturbed upper 25 or so centimetres of soil only (i.e. the plough zone), as we had done in previous seasons, we succeeded in detecting subtle changes in soil colour and texture indicating where graves had been dug centuries ago. Pausing only to record their locations (we did not excavate any of them), we proceeded eastward, hoping to find the eastern edge of the cemetery and, perhaps a short distance beyond, some evidence of the palisade line Winslow’s troops built to enclose the cemetery and its associated buildings.

A short distance past the end of our 2013 excavations, a couple of interesting features came to light. In the order in which we encountered them, the first was a narrow trench feature (labelled ‘a’, below, and measuring approximately 15cm wide and 40cm deep) running north-south across our excavation unit. Looking very much like an old fence line, this feature appears to mark the eastern limit of the graves, and may therefore be interpreted as the eastern boundary of the Acadian cemetery. Despite having extended our excavations over 10m eastward of this location, we have found no additional evidence of graves.

Two mysterious trench features located east of Herbin's Cross. The narrow feature (a) may be a fence marking the eastern limit of the pre-Deportation Acadian cemetery, while the larger feature (b) may be the eastern palisade line of the New England military camp of 1755.

Two mysterious trench features located east of Herbin’s Cross. The narrow feature (a) may be a fence marking the eastern limit of the pre-Deportation Acadian cemetery, while the larger feature (b) may be the eastern palisade line of the New England military camp of 1755.

A metre or so past this narrow line we found a second and larger trench feature, also running north-south (labelled ‘b’, right). Measuring approximately 25 cm wide, it had originally been dug to a depth of approximately 50cm, which may seem a little shallow for a palisade trench, but then again Winslow’s men were colonial volunteers rather than Royal Engineers. Who knows how deep they were told to dig, or how closely their work was monitored? It happens that Jeremiah Bancroft, one of Winslow’s junior officers, records in his diary that two Acadian prisoners escaped from the camp on the night of Sept. 27th, 1755, by removing a couple of pickets and squeezing through the gap.

So, is this larger trench feature actually John Winslow’s wall?

The question can’t be decided with the evidence at hand, but it doesn’t seem that any property boundaries ever ran this way, and we are encouraged by the fact that all of the archaeologically known graves are located west of the narrower line. Additional excavations are required to determine how far the feature in question continues to the north and south. We know Winslow’s palisade enclosed the parish church and two other buildings as well as the cemetery, therefore our feature should at some point turn westward and in the direction of those structures.

Assuming it remains largely intact, a series of linear test excavations introduced at intervals, perpendicular to the supposed line of the trench feature, should enable us to trace its course. Along the way we’ll have to dodge the hedges, flower beds, and numerous buried pipes that form the commemorative infrastructure of Grand-Pré National Historic Site. But that will be a job for next season.

 

 

 

 

Posted by: Jonathan Fowler | June 30, 2014

Student Perspectives: Let’s Get Geophysical!

In this post, student Hayley Schofield describes her first encounter with archaeological geophysics. – JF

The Geonics EM38B and data logger, ready for another day's work.

The Geonics EM38B and data logger, ready for another day’s work.

This year in Saint Mary’s Archaeological Field School geophysical data were collected from an apple orchard in Grand Pré, Nova Scotia. The data resulted in two new sites being located and partly excavated, both of which yielded discoveries that corresponded with the anomalies shown in the geophysical data.

Geophysics is one of the many instances where archaeology meets hard science. Equipped with geophysical equipment, archaeologists scan the area in which they hope to locate a dig site. The EM38B records the ground’s conductivity and its magnetic susceptibility half a metre down. By walking straight lines down the entire site one can generate maps that display geophysical anomalies.

The spiked area at the center of the image below exhibits abnormally high magnetic susceptibility, which is caused by concentrations of magnetite. This is what archaeologists take an interest in. Magnetite concentrations are high in soil containing certain iron oxides and mafic stone like basalt. Soil that has been subjected to burning can also cause anomalies that the EM38 can pick up.

A magnetic susceptibility anomaly discovered during our 2014 surveys (and a target for excavation).

A magnetic susceptibility anomaly discovered during our 2014 surveys (and a target for excavation).

 

Ultimately, we need to dig to determine for certain the cause of geophysical anomalies. This case, which we have called Site 1, turned out to be a prime example of successful geophysics because our test excavation revealed positive results. The 2X2 metre trench we opened at the SW corner of the anomaly provides sufficient information to better understand our data. Many of the stones revealed by this excavation, when tested with powerful magnets, were found to be magnetically susceptible. Several smaller iron items, such as nails, were also discovered here. An additional source of the anomalous readings was found in the form of burned brick fragments and charcoal. So far, the main archaeological feature at Site 1 appears to be a back-filled cellar – likely part of a destroyed Acadian house.

Site 1 as partly revealed by archaeological excavation. It looks like an old cellar.

Site 1 as partly revealed by archaeological excavation. It looks like an old cellar.

Geophysics, when done properly, can yield accurate maps of an area’s archaeological resources. Once an area is cleared of obstacles, the scan itself can be done and the data processed in just a few hours. My personal experiences during the course was that a 20X30 metre area could be scanned in an hour to an hour and 30 minutes and the data processed in no more than an hour.

Geophysical surveys are much faster than traditional test pit surveys, in which archaeologists look for sites by digging small test excavations, often at 5-metre intervals. These intervals also leave room for error. Things can be missed completely if an archaeological feature sits between the test pits. While geophysics also has room for error, it collects consistent lines rather than spurts of data. Geophysics is also less destructive; once you have dug something up that contextual information is lost forever and is contained only within the notes taken during the dig. Geophysical scans capture data without altering archaeological deposits. They can also be conducted in smaller increments (i.e. tighter transect intervals) to create more precise data maps of an area before even placing a shovel in the ground. This enhances the excavation process by allowing archaeologist to cut down on futile digging.

 

 

Posted by: Jonathan Fowler | June 14, 2014

Student Perspectives: Sifting Through Screens

In this post, student Nikki Lachance offers a few thoughts on a standard part of the archaeological tool kit: steel mesh. – JF

Max Tardy (headless, at left) operates one of our rocker screens.

Max Tardy (headless, at left) operates one of our rocker screens.

Screening (also called sieving or sifting) is a process used by archaeologists to sift through soil taken from excavation units, trenches and test pits. This process allows archaeologists to sift through the displaced dirt in order to locate any artifacts that may not have been otherwise located while working within the excavation unit.

There are different types of screens and different mesh sizes archaeologists can use to search for smaller artifacts during an excavation. The larger the mesh size, the less time it could take to sift through soil, but the greater the likelihood of small objects slipping through. Choosing a smaller mesh size can take more time, however, there is a greater chance of locating smaller artifact pieces. Determining the proper screen type and mesh size may depend on accessibility and preference.

For archaeologists working on sites where lugging a large, heavy, and often times awkward screen is conducive to screening nightmares, a portable or backpack screen may be used. These screens can be as small as 15” x 10” or as large as 17” x 12”, making them easy to carry. The actual process of loading the screen with dirt and shaking it back and forth may be awkward for those who lack upper body strength.

The tripod screen, which is a box screen that hangs in the centre of a tripod, much like a pendulum, allows for easy dirt dumping and fairly laid back sifting. I personally have not used this type of screen, but I cannot find any fault with this type, other than the lack of developing your biceps.

Archaeologists looking for portability, durability and more stability often use the rocker screen. This particular type of screen is what we used during our excavations at Grand-Pré National Historic Site as well as the neighboring orchard and field. This screen has a frame with two legs that sit on the ground and allows the screen to be shaken back and forth with additional support.

Soil types can help or hinder in finding artifacts while screening. Archaeologists tend to prefer a type of soil that is dry and loosely compacted. The dry soil will go through the mesh like flour, and if it is loose, then it is less likely to stick together and form balls or clumps. Trying to force a wet, compact, clay-rich soil through a mesh screen can be tedious and strenuous as well as the cause for angry outbursts. A trowel or a gloved hand may be used to push the soil through the screen, and if the excavation site has access to water, wet screening can be the solution to difficult soil. Wet screening uses water to assist in pushing the soil through the mesh. This method can speed up the screening process and can make artifacts easier to find, as the water cleans away the dirt and leaves the artifacts behind. But this is messy.

As screening is an important process for finding artifacts within excavation units, it is therefore important to be able to distinguish between artifacts and non-artifacts. Archaeologists train their eyes to be able to make this distinction. Depending on the familiarity with ceramics, for example, being able to locate these artifacts while screening may require a second opinion. New archaeologists may be faced with the realization that the majority of their finds are merely pretty rocks.

When I first started screening, my eyes caught every single oddity – sparkly things, sharp things, oddly shaped things. It was only with time and consultation that I learned how to separate artifact from non-artifact. I am no pro, but compared to my first day screening, my identification skills have improved because I had a lot of practice and worked with a team who had higher levels of artifact identification skills.

A little advice? The most effective way to locate artifacts by screening the soil is to work a little bit at a time. Soil tends to clump unless it is extremely dry, so taking the time to sort out the clumps by pushing them apart with a trowel or breaking them apart in a gloved hand can be the difference between finding an artifact or not.

 

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