Thursday, June 2, 2011

Got Rocks?

Excuse my lame title, but I just wanted to talk a bit about the Geology of the area. Myself and many others in the class have had none, or limited experience in the field. I guess one of the things that can really speed up and streamline (certainly not at the expense of accuracy and thorough screening) a dig, is a general understanding of local geology.

As students of archaeology, many of us are familiar with things that are directly used by humans but can still get fooled by the occcasional regional eccentricities. For me, it was tabular quartz in Nevada's playas and it was caliche here at DSCQHR. Alot of the time you can spot these tricksters but in some cases you get pieces that look ambiguous enough that you do a double take.

Additionally, knowing the assemblages in the area can help you to know what to look for. The type, color and associated minerals can always be of service, particularly where chert is concerned. Knowing what materials were available allows you to key in more precisely, what you are looking for and what stones are of interest in identifying sites that may have a large concentration of the mineral.

Talking to Brenna and David during the course of the field school, I learned that Monterrey chert is found farther from its source than I had previously thought. I had previously thought that Franciscan chert and obsidian from the Clear Lake area was the mainstay of the groups that lived in and around DSCQHR.

A book I highly recommend for anyone interested in the geology of the Bay Area is Doris Sloan's Geology of the San Francisco Bay Area. It is an excellent guide for the beginning/intermediate student of geology and gives a great overview of the assemblages in map and text form. The illustrations are great and it is easy to understand. Hopefully you can pick one up if interested.


  1. Thanks for the suggestion on the book! Knowing the difference between rock and artifact was one of the biggest challenges I faced during the class! Hopefully I can continue to improve on identifying things in order to make the excavation process MUCH faster!

  2. Indispensable suggestion. An archaeologist can do nothing but profit from a sound understanding of local geology. Well stated.

  3. I would also recommend taking a geology class. I took one at the local community college, and it has helped me out a lot when distinguishing geological features of the land.


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