Putting It All Together

Stereonets can be be a useful tool to geologist as they can help visualize large amounts of data and plot them to find trends.  Remember when we talked about the Lamprophyre Dikes and how they were off set.  There are two hypothesis as to why they are off set.  The first is that there is a fault at Mather Gorge.  The second is that the dikes were naturally crooked and when the Potomac River incised down over time, the truth of the offset was eroded leaving the two limbs on either side of the river offset.
If there is a fault under Mather Gorge then we should expect to see no apparent trend line that lines up with Mather Gorge on the stereonets.

Mather Gorge (green line) compared to poles to jointing

Mather Gorge (green) poles to foliation

Mather Gorge (green) poles to bedding

I constructed a stereonet from the class data.  After plotting the poles, I compared that to the plot of Mather Gorge and found no trend from the class' data that lined up with Mather Gorge--or even came close.  In fact, the class' data was so random that a clear trend was not possible, or even a murky trend.  For this reason, I was not able to conclude whether, or not, there was a fault under Mather Gorge or a crooked dike. It does give evidence for the presence of a fault.  I wasn't able to disprove the presence of a crooked path, however, because in order to do this I would have to physically look at the dike.  I can't do that nor can anyone because the river is too deep and treacherous with large boulders in the base of the channel.  I guess the mystery of Mather Gorge will have to be solved on another occasion.