Reconstructing the Geology of the Marin Headland Field Trip Page

Introduction and Problem


From the Marin Headlands, toward Golden Gate Bridge
taken by: Heather Marshall

Introduction: The Marin Headlands offer a short cut glimpse into the formation of the Coast Ranges.  In a relatively small area, you can go back into the past and read the history of the Earth as it unfolds in the rocks.  By looking at the types of rocks present at different locations in the Marin headlands, you can collect data on depositional environment, sources of the rocks, and how the rocks got to where they are now.  The Coast Ranges are much larger than can be handled in a short field trip, but the Marin Headlands offer a glimpse into the Ophiolite Sequences that make up much of the Coast Ranges.

The Marin Headlands are located just North of San Francisco, off of the Golden Gate Bridge.  The map below outlines the road access to the Headlands.  They consist of layers of folded cherts, sheeted dikes, pillow basalts, greenschist, sandy turbidite sequences and some serpentinite that make up the Franciscan Assemblage of the Coast Ranges.  In case you are unfamiliar with any of these terms, there is a table with links to help you understand how these layers form, what an ohpiolite sequence is and more.
Introduction taken from personal notes taken during Field Trip by DiLeonardo March 10, 2011
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Map shows approximate locations of STOPs 1-4.
Modified From: http://www.google.com/images?q=marin+headlands&oe=utf-8&rls=org.mozilla:en-US:official&client=firefox-a&um=1&ie=UTF-8&source=og&sa=N&hl=en&tab=wi&biw=1176&bih=519

Problems: How were the Marin Headlands and the Coast Ranges of California formed?  What tectonic processes were in play prior to the San Andreas Fault System?  How can we reconstruct the history of this area?

Methods: We will reconstruct the geologic history of this area by taking a virtual field trip to the Marin Headlands.  As we go to the "Stops", we evaluate what is happening at each location, and what forces, depositional environment, and or tectonic/volcanic processes might be at play.  From the "Stops" we will be able to reconstruct the geologic history of the Marin Headlands and thus the Coast Ranges.  

Terms for Investigation:  Research the following terms on the internet to determine how they form, where they form, traits of the feature, an how they might have gotten from where they are typically formed to the West Coast of California ont he Marin Headlands and the Coast Ranges.
Pillow basalts ophiolite sequence
sheeted dikes chert
gabbro greenstone/ greenshist
subduction zone accreted terrane
shale turbidite sequence
sandstone melange
serpentinite blueschist
fault fold
slumps/landslides uplift
Franciscan Assemblage Sonomian terrane
Go to the Research and Investigation of the Marin Headlands