Analyzing the fossils
of Mt. Diablo (cont.)

(page 2 of 3)

Each day, Sarah set out with the appropriate locality maps in hand, information on her targeted localities, a GPS unit supplied by the Park, collecting bags, lunch, and lots of water. After about eight hours of bushwhacking, climbing, and crawling over the mountain each day, the next task was to document, interpret, and compare the findings with past records. In total, Sarah was able to locate 51 of the original localities and identify five additional sites. Many of the historical records she was using were incomplete and often difficult to interpret. Without the current understanding of plate tectonics and todayís technology, it is not surprising to find that there were numerous inaccuracies in much of the earlier work. In some cases, a single geologic formation had as many as three different names in as many publications. In others, that same formation was assigned to the Miocene in one report, while another report listed it as Oligocene. Much of the rationale for the name and age assignments was based on correlation with geologic units and fossil finds in other parts of the state. So as new evidence was found, dates and names of units fluctuated.
Sarah unraveled much of the confusion and conflicts and, in the process, compiled an interesting history of the paleontology and geology research of the area, which she hopes to publish. In the final report to the State Parks Department, Sarah included this research history, a taxonomic listing of the fossils found, a management plan for these resources, as well as three separate maps showing the geology, fossil localities, and management plan.


Without an established state standard to follow, Sarah based the fossil resource management plan on the geologic formations, evaluating each for its level of exposure and fossil content. Now, this resource management plan, as well as the criteria used to generate it, may become the state standard.

Rock from Mt. Diablo Ophiolite Formation
Exposure of Mt. Diablo Ophiolite Formation
A rock sample (top) from an exposure (bottom; see arrow) of the Mt. Diablo Ophiolite Formation, a mixture of oceanic and island arc components dating from the Jurassic Period. (photo by Sarah Rieboldt)

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