Mt. Diablo

**Remember that Mt. Diablo is within a State Park. It would be best to just take pictures of fossils found.

Geology of the Area:

According to the Mt. Diablo Interpretative Association, Mt. Diablo is a mountain with an elevation of 3849 feet in the Diablo range. Although the mountain has only very recently emerged, the rocks it is composed of are very old. Due to its complex geological history, the rocks of Mt. Diablo can be divided into three groups, Mt. Diablo Ophiolite (Jurassic), Franciscan Complex (Jurassic and Cretaceous), and Great Valley Group (Jurassic and Cretaceous). Additionally, the younger sedimentary rocks on the higher strata are Cenozoic.

Mt. Diablo Ophiolite: An ophiolite is a part of oceanic crust and the underlying upper mantle that has been uplifted and exposed above sea level and often developed onto continental crustal rocks. According to radioactive and fossil-age determinations, the ophiolite emerged approximately 165 million years ago. The ophiolite basalt has a crystalline feel with a black to greenish-brown hue. This is created when lava erupts underwater and ‘freezes’ when it makes contact with the water. Diabase is a coarser version of the ophiolite basalt that is created by lava erupting from vertical fissures underwater. Serpentinite can also be found on Mt. Diablo.

The middle area of the Mt. Diablo strata known as the Franciscan Complex is the result of 140 million years of east-dipping subduction. Concerning fossils, approximately 10% of the Franciscan Complex is composed of shale. Unfortunately, most of it has been converted to argillite as a result of metamorphism.

The Great Valley is composed of sedimentary shale and sandstone from the Upper Jurassic to the Cretaceous period. It is mostly deep-water shale. There are also younger Cenozoic strata on top. As a result of the drying of Central Californian basins during the Miocene and Pliocene, marine fossils end at that time.

Paleontology and Fossils:

Cow and Aelurodon jaws have been found, in addition to plants. Marine fossils from both deep and shallow water environments have been recovered.

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This article contains detailed information and directions to a trail that leads to fossils in Mt. Diablo State Park.

Works Cited:

“The Rocks of Mt. Diablo- Their Type and History,” (Mt. Diablo Interpretative Association 2016) www.mdia.org 

 

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Sespe Wilderness

Geology:

The Sespe Wilderness lies within the Transverse Mountain Ranges. The USGS has information on the geological setting of the mountain range province here. More specifically, the Sespe Wilderness and Sespe Condor Sanctuary are mostly within the Topatopa Mountains and foothills. The  Topatopa Range is composed of Oligocene-Eocene age sandstones of the Juncal, Matilija, Cozy Dell, and Coldwater Formations. The uplifting of the Topatopa Mountains was chiefly caused by the San Cayetano fault, which was initiated at 1.9 Ma.

The fossils in the Sespe Wilderness are incredibly common and can be found on the trail and in the abundant boulders nearby. Marine shells can be seen exposed on the outside of eroded and smooth boulders, and on the surface of the rotated strata of the foothills.

Paleontology:

A variety of marine invertebrates are common in the area, including mussels, oysters, cephalopods, and other shelled organisms.

Works Cited:

MCKAY, HANNAH. QUATERNARY STRATIGRAPHY AND GEOLOGIC EVOLUTION OF OJAI AND UPPER OJAI VALLEYS, WESTERN TRANSVERSE RANGES, CALIFORNIA. P.2011

 

Jalama Beach

Geology of the Area:

The cliffside of this beach contains shale from the Monterey Formation. The fossiliferous shale dates back to the Miocene epoch. There are talus slopes in many areas created by folded and slanted strata. jalama04.jpg

Be careful of falling shale from the cliffside. Although it poses a hazard, the fallen rocks are more convenient to split than extracting shale from the outcropping. Split fishes can be found near the bottoms of the formation. Additionally, petrified whale bone has been recovered on the beach.

 

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As you can see in the figure above, three prominent outcroppings jut out from the Monterey formation, marked 1, 2, and 3 on figures B and C above. Figure A shows that Jalama Beach, to the left of Gaviota, is part of the Monterey Formation bearing marine Miocene fauna, and Oligocene rocks are found more inland.

Paleontology:

Fossil fish and petrified whale bone are in the outcroppings.

Use this Stanford Study of Lompoc Fossil Fishes to identify your fish finds.

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Works Cited:

David Jordan, et.al, “Fossil Fishes of Diatom Beds of Lompoc, California,” (Stanford University, 1920)

Images: “Jalama Beach,” (The Nautiloid Network) www.nautiloid.net 

Kathleen Surpless, et.al, “Evolution and stratigraphic architecture of marine slope gully complexes: Monterey Formation (Miocene), Gaviota Beach, California,” (Trinity University, March 27, 2007)

Capitola Beach

Geology of the Beach:

The yellow brown sandstones that contain the fossils are part of the Purisma formation. Collecting is best at low tide, when the outcroppings are most exposed. 2429587379_250f7320ef.jpg

Paleontology of the Fossils:

The fossils originate from the Pliocene epoch of the Neogene period. Bivalves, gastropods, sea urchins, crabs, marine mammal bones from whales and seals can be found. Shark teeth have also been recovered from the beach, but are rare.

An extensive photo gallery of the fossils common at Capitola Beach can be found here: http://nextcenturyimages.com/nature/capitolafossils2307/index.html 

Works Cited:

“CA Capitola,” (Paleontica Fossiel August 2012) <http://english.fossiel.net/sites/fossil_site.php?plaats=506>

Jacalitos Creek

image069Paleontology:

Fauna found in the area include three species of Echinodermata, two Cirripedia, Pelecy- poda, and 29 Gastropoda. Many new gastropod species were discovered in Jacalitos Creek including  Attralium arnoldi, Chrysodomus coalingemis, Fissuridea subelliplica, Murex perangulatui, Natica (Neverita) orbieularis, Trophon magister, Turritella nova; Pelecypoda : Mytilus ketvi, Tivela trigonalis.

Works Cited:

Jorgen O. Nomland, “Fauna from the Lower Pliocene at Jacalitos Creek and Waltham Canyon, Fresno County, California,” (North American Paleontology 1916) <http://journals.cambridge.org/download.php?file=%2FGEO%2FGEO6_3_08%2FS0016756800206043a.pdf&code=143cdf352a36a8ead990e75cf703ee45>

Shell Creek

Geology of the Area:

The area contains Cenezoic marine strata, which is part of the Temblor Formation.

The Fossils:

In the cliffside just off the road are clams, sand dollars, and Oysters, likely dating to the Miocene or Pliocene epoch.

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