Hayden Butte Lab

This is the first outdoor lab for the historical geology class. Located on ASU Campus, Hayden Butte (A Mountain) is a well known site for and ASU student. The butte holds the Sun Devil Stadium (Home of ASU Football and Super Bowl XXX) on a saddle on the south east side. The lab began by looking at the oldest rocks on the butte, located on the north side in a drainage canal parallel to Rio Salado Pky. The exposed sandstone layers here are estimated to be only 17 Ma. The oldest sandstone beds are perforated with trace worm burrow fossils.

Just up the rock strata we found:

This is the trace fossil of mud cracks. Cracks were formed into a layer of mud, that has since turned into shale. Sand filled the cracks and formed a layer of sandstone. Later, the underlying shale eroded and left the negative impression of the cracked mud.

A little farther up the strata we found:

This section of Sandstone / Shale Interbedding shows a fault. Although the age of the fault is unknown, is can be assumed that it was caused by the tilting event.

Now this was unusual:


This is a very perculeier formation. What this is is a 2m thick volcanic ash formation. However as you can see, the bedding has been convoluted into ball and pillow shapes. This can be caused by either seismic activity on the wet rock, or by being compressed from above (also while the rock was still wet. This formation was so cool that I had to grab a smaple for my collection.

Finally the youngest rocks on the butte were a nice andesite lava flow. A short ways down from the top I found some eroded chunks of the andesite:


and here is what I thought was really cool; this is where a lava flowed over sandstone, resulting in contact metamorphisim:


And here is a rip-up clast of sandstone that had been metamorphosed into quartzite: