July 16

Okay, now onto my lab work (which I conveniently avoided describing for the first few days). I'm helping Adam with

his project on the Guadalupian extinction and to do that, we need to make sure the samples that he got (from Sichuan, China)

hadn't gone through diagenesis, which is a fancy term for "being changed after deposition." Basically, we wanted

to make sure that no alien material had gotten into the samples he gathered, and this would take a long time as

he actually gathered a over a hundred samples.

So, how do we do this? First, we cut the rock so that the cut is in the same plane as the stratigraphic north. Basically,

visualize a cliff of rock (an outcrop). We want to cut the sedimentary rock so that we can see the rock from top to bottom,

so that we know how old the rock is. The further toward the surface the rock is, the younger it is. The further away

from the surface a rock is, the older it is. So, we cut these samples so that we could see as much of its age as possible.

The process itself is pretty tedious. We had to label each sample about 3-4 times (because we used a water saw to cut them

so half the time, the label would fade away after the cut). What we want in the end is the measurement of trace elements,

so ,in this case, Mg, Mn, Fe, and Sr. If any of these trace elements show a significant positive or negative excursion,

we can conclude that diagenesis has occured and the rock is altered.