Miocene Era Fossils from Santa Cruz Mtns #4

[MioceneFossils]

I collect fossils in already disturbed areas around Scotts Valley, CA, mostly sand quarries and road cuts. The fossilized sand dollars I've collected date to the Miocene 10-12 million and, from what I understand, most everything found in this area is similar from a chronological point of view. This region was a vast, shallow ocean back then so most of the fossils are aquatic. An intact sea cow from this era was famously collected in this region. The first fossil I posted appears to be coral. The second remains unidentified, but someone floated the idea of a worn sea urchin.

 

Here are a few more fragments. They look like fossilized bone to me, but I'm clueless.

 

 

[Harry Pristis]

That would be the marine Topanga Formation of Late Hemingfordian age.  You might look for a species list(s) for that formation for clues to what you are finding.  The three fragments you present here are unidentifiable, in my opinion.

[Spoons]

Curious how many of your specimens exhibit these “holes”.

[siteseer]

2 hours ago, Harry Pristis said:

That would be the marine Topanga Formation of Late Hemingfordian age.  You might look for a species list(s) for that formation for clues to what you are finding.  The three fragments you present here are unidentifiable, in my opinion.

 

Hi Harry,

 

The layer is most likely the Lower Santa Margarita Formation which is exposed around Scotts Valley.  I used to collect at the Lockhart Gulch Road site before it became a storage locker facility.  I recognize the preservation of those pieces and two are a good match for bone though I'm not certain that one on the lower right is bone.  You get a lot of worn bits of bone like that in the fomation.  Some of it is rather brittle but some pieces are quite hard.  Local jewelry-makers like to incorporate the harder pieces because they can be drilled, are natural, and can be found in different colors.

 

You can find shark teeth in that layer but they are also often water-worn to the point of looking like a guitar pick.  You can occasionally find an identifiable marine mammal tooth or bone (even a land mammal tooth) as well.

 

The Topanga is known farther south in Orange County.  I'm not sure of its northernmost extent.

 

Jess

[siteseer]

Hi MioceneFossils,

 

I'd have to see the sand dollars you're finding but I can tell you that there are sand dollars from the latest Miocene to perhaps early Pliocene.  They tend to be found closer to Santa Cruz (genus Dendraster).  There are also sea urchins (genus Astrodapsis) that are a little older from the upper part of the Santa Margarita Formation.  These have been found around Scotts Valley and Felton.  A lot of sites for those have been closed to collecting in part due to construction.  

 

The sea urchins come out of the upper part of the Santa Margarita while the shark teeth come out of the lower part with maybe 4-5 million years in between the deposition of those layers.  Years ago, I was told that the upper part is about 5 million years old and the lower part is 9-12 million years old.  I don't know if that has been revised though various sites in North America have been studied in more detail with more precise means of rock-dating. 

 

You can find a few spines of another genus of sea urchin with Astrodapsis but I don't think anyone has found a test (body) of that sea urchin yet.  I've also seen some gastropods and barnacles.

 

Jess