Here at stop #1, you can see the basement rock layer for our study, the Payson granite. The layer right above the granite is the Tapeats Sandstone (also represented at the GC). Whats amazing here is what is called the great unconformity. To the untrained eye, theese rock layers look like a normal transition, or juust like the same rock alltogether. But the bottom layer is 1.2 billion years older than the top layer (540 million years old.) What this means is that there is 1.2 billion years of rock history that is entirely gone.
Here is one of my professors (Dr. Stump) explaining some of the finer details of the strata (strata means column of rocks).
Here is another shot of the rocks:
A little farther up the section we came to the disconformity between the Redwall Limestone and the Naco Formation. The Naco is the layer on the top of the road-cut, whilst the Redwall is the bottom layers:
Here are some other views of the two groups. Can you see the division??
The Naco formation is LOADED with fossils! We took 60 minutes to sample and log some (which we also got to keep for our personal collections) I found about 30 or so in that time. Ranging from crinoids to brachiopods, there were some sweet samples! Ask me sometime and I'll post close-up's of the different ones. I also founs a cool sample that has criniods, brachiopods and fossilized bryozoans. These fossils are all form the Pennsylvanian period so they are about 300 million years old.
Here is a scenery shot of what the forests look like up there:
Here is a self portrait of me as I an taking notes:
There are more scenery shots. One of them is our group sitting at the top of the main section of Coconino Sandstone.
Here is one last shot of the group hiking to a remote locaton to look at a sample of the Apache Group formation, and then the Apache Group Formation itself.
3 comments:
Hey, that looks like a pretty cool field trip. I have two questions. 1. What could have possibly happened to the rock in the middle of the two layers. 1.2 billion years is a lot of rock to be missing. What do scientists think happened? 2. Could you please post a picture or two of your fossils. I am totally fascinated by fossils and would love to see some of your favorites.
Sure.
Answer #1: The reason for the unconformity is generally erosion. At the time that the tapeats sand stone was being deposited was a time where there were oceans in the area. By looking closely at the photograph where there is the guy in the green shirt, you can infact see several "rip-up-clasts" (small angular white rocks) in the bottom of the sandstone layer . Those are pieces of the granite that was ripped off by violent water currents passing by. We know that an ocean moved inland here because of what is called a transgressive sequence. First sand was deposited, then a layer of mud, then limestone which comes from the accumulation of sea shells and other carbonate things (not to mention dissolved calcium carbonate in the water itself.)
Question #2, i'll post it tomorrow for you.
Hey Robert
You sure look like a Geologist!! I am surprised that Idaho isn't more red and brown. We have had so many fires this summer and we have little volcanoes every where they probably are dead but they are still there. I think I will just come live on the Moon with ya or maybe Mars I think they found water there:)!
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