U-Shaped Structure - Dendrochronology Update

Photo courtesy of Mistik Askiwin Dendrochronology Laboratory (MAD Lab), University of Saskatchewan

by John Wonnacott, P. Eng - Contributing Writer
  Last February we published “The U-shaped Structure at Smith’s Cove, Oak Island”, and in the article I said that we (meaning me, Les MacPhie and Danny Hennigar) had sent a sample to a Dendrochronology research lab to attempt to learn the date when the tree was cut, from which our sample was taken. That date would almost certainly have been close to the date when the U-shaped structure was built. However we ran into two problems.  Our sample had only 34 tree growth rings, while a proper dendrochronological investigation needs at least 50 rings to have the best chance of finding a unique age match.

  So for this reason, the lab took a lot of extra time trying to find clues in the data which would help determine the age of the sample.  Secondly, the Dendrochronology lab we used is located at the University of Saskatchewan, and the pace of lab work was determined by other events going on within the university. So it has taken a long time for the lab to reach a conclusion, and even now we only have a draft report of the findings. I have been waiting until now to write this follow-up article, preferring to have a final report that I can share with you. But the professor who directed our work has said it is fine with him for us to publicize the results presented in the rough draft.    

   Our sample was determined to be Red Spruce (Picea rubens), and that species identification helped us in a curious way. Red Spruce trees are prone to infestations of spruce budworms, which cause characteristic damage to the tree, and such damage is observable in the growth rings for the years of infestation. For hundreds of years, budworm infestations occurred about every 40 years in Nova Scotia, and if our sample had included growth rings from infestation years, these would have acted as markers that would have helped the lab obtain a match. However we were not so lucky and the 34 years of growth exhibited by our sample was between budworm infestations. However this turned out to be quite a help just the same. The lab did find 3 possible matches for our sample, when they compared our growth ring sequence to their master chronology. Our growth ring sequence could be for one of the following three periods: 1659 to 1695 (meaning the tree sprouted in 1659 and was cut down in 1695), or 1711 to 1747, or 1822 to 1858. The interesting and valuable thing is this: for each of these three possible periods, there were no spruce budworm infestations! So the lab is quite sure that one of these three periods is correct and that means our sample probably dates to either 1695, 1747 or 1858.
  Here is a photograph of our dendrochronological sample, after it was prepared by the lab. The pencil lines on the sample indicate where measurements were taken by the analysts:

Larger photo of the sample submitted for testing. Photo courtesy of Mistik Askiwin Dendrochronology Laboratory (MAD Lab), University of Saskatchewan

1695... 1747... 1858?

  The data base that the lab uses for their work is called a master chronology and it consists of individual tree growth ring sequences from many samples with over-lapping years of growth. The database has less than 5 Nova Scotia samples for the 1659 to 1695 and 1711 to 1747 growth periods, while they have quite a lot more data for the 1822 to 1858 period. Because of this variance in data density for the earlier possibilities, the lab has concluded that the date our sample tree was cut was more likely 1858. That’s not good news for those of us who are hoping the U-shaped structure could have been built before 1795, however, like so many findings at Oak Island, the answer is not definitive. Maybe our sample is older.

  We have shared a copy of the dendrochronological testing report with Rick and Marty Lagina, and I have asked them if they could possibly get a permit to re-excavate at Smith’s Cove, in the area of the U-shaped structure. In my correspondence with the Lagina brothers I explained how we triangulated from old photographs to find the U-shaped structure about 15 years ago, and I suggested if they get a chance to dig in the area, to focus on the south arm of the structure, so that a new sample of the structure could be obtained (that would be from a different log than the one our recent sample was taken from, and hopefully they would find a log with more than 50 growth rings).
The lab at the University of Saskatchewan has told me that they would be very willing to investigate a new sample if we can obtain one. So I am crossing my fingers that Rick and Marty Lagina can come up with a new specimen, and that we will be allowed to take a thin slice of wood from it, so we can continue the Dendrochronology work. I think it would be great if we can learn the date for sure, when the U-shaped Structure was built!

   As a footnote to this update, Danny Hennigar and I had an interesting adventure this week. Danny is responsible for the “Explore Oak Island Display” (located in the old historic train station in the village of Chester, Lunenburg County. The display is actually an museum of oak Island artifacts located at 20 Smith Road, open 7 days a week with free admission), and he had a visitor to the museum who observed the U-shaped structure sample shown in the photograph in this article. The visitor told Danny that he had found another piece of the same structure about 15 years ago, when he was beachcombing on a nearby island (This turned out to be a tiny island just north of Oak Island, between Oak Island and the mainland). This seemed plausible, because back in 1970 when Dan Blankenship had built the temporary cofferdam at Smith’s Cove, and the U-shaped structure was partially exposed, a very high tide flooded the workings and washed out the cofferdam. So a piece of the structure could have floated away from the excavation, and it could easily have washed up on a nearby island. So Danny called me and we made arrangements to go see this log.

  When we arrived at the visitor’s place, we saw an impressively large piece of log, about 6 feet long and 12 inches in diameter. There were notches cut near one end (and the far end had rotten away), and 2 inch diameter oak pegs had been driven through the holes, just like the U-shaped structure. But the notches had sloping sides and they were not identical to the U-shaped structure notches, and there were no other notches at 4 foot spacings as we would have expected. On the other hand one notch was cut in a shape like those used to make corners in a log cabin – so we thought it was possible that this log could have been the south end piece of the base of the U-shaped structure which lies parallel to the shore, and the “log cabin” notch might have been where the south arm of the structure was joined to the base. However after carefully examining the log and thinking about it for a while, we concluded that this interesting new log was probably part of a very old wharf that was built somewhere in Mahone Bay. The most disappointing thing concerning this log was that it is too rotten for a dendrochronological sample to be cut from it. So we were left with a tantalizing experience.

Here are two photographs of the log.

Mahone Bay Mystery Log. Photo courtesy of Danny Hennigar

Mahone Bay Mystery Log. Photo courtesy of Danny Hennigar

  What do you the Readers think?   Could this mystery log have been part of the U-shaped structure?