*sigh*. Its been slow progress over the past month on the PhD front. What with the MAT 251 breaking down, the results from dating taking forever (we outsource to another uni who do it near constantly), the PhD is crawling slowly slowly along. The next step in the journey of the stalagmite from cave to paper is that it needs to be marked up and a decision taken as to where exactly we need to drill into the stal to get our results from.
We want to get our results from as close to the middle of the stal as possible. Thats why we cut slabs out of them to get to the middle, with the slab direction chosen so that the central growth axis of the stal where we want to measure can move (as they tend to do with changing drips) whilst still allowing us to access it. First we chose the side of the slab which we believe is closest to the centre of the stal for the longest duration and that has nice banding. Then we draw a line up the centre of the stal, keeping it roughly midway through the flat parallel layers that define the centre of the stal rather than the sloping edges. And ideally we draw perpendicular to the growth layers to get better sample resolution and less overlap between samples.
Because the growth axis moves around over time (you wouldn't expect a drip from the ceiling of the cave to stay exactly in the same place for tens of thousands of years) this involves stopping the lines, changing angles and shifting left and right as appropriate, but ideally as little as possible to avoid any unwanted changes in isotopes that can sometimes result. Plus we need to shift the lines near the edge of each slab so that we have overlap between the slabs and can therefore overlap our results and make sure they line up perfectly, rather than guessing! It takes a little while longer than just drawing lines would first suggest.
Next time: drilling our samples! (which will hopefully happen sometime in May if we get the new drilling machine up and running).
The stal known as "crusty" is marked up ready for drilling.
Because the growth axis moves around over time (you wouldn't expect a drip from the ceiling of the cave to stay exactly in the same place for tens of thousands of years) this involves stopping the lines, changing angles and shifting left and right as appropriate, but ideally as little as possible to avoid any unwanted changes in isotopes that can sometimes result. Plus we need to shift the lines near the edge of each slab so that we have overlap between the slabs and can therefore overlap our results and make sure they line up perfectly, rather than guessing! It takes a little while longer than just drawing lines would first suggest.
Next time: drilling our samples! (which will hopefully happen sometime in May if we get the new drilling machine up and running).
A close up of one of the lower slabs of crusty
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