Possible fossil found at the beach

[Mossrute]

Hi, I am new to this forum. I have a degree in biology and a degree in art. I specialized in zoology and my final project was about cephalopod evolution. I am an oil painter, scientific illustrator, and calligrapher. I have limited experience with fossils. I have actually never posted on any forum before, so apologies if I am not doing something correctly.

 

I recently found this odd formation in a rock at the beach. I am not sure what it is. 

Has anyone seen something like this before?

 

[DPS Ammonite]

Welcome to the Forum. Tell us about the rock and where you found it. Can you scratch it with a metal blade? Does it fizz in acid?

 

A wild guess would be a bivalve in diatomite from the Miocene Monterey Group because it is a commonly found white rock layer found along coastal California.

 

Use the map of California geology:

https://maps.conservation.ca.gov/cgs/gmc/

Edited September 4, 2023 by DPS Ammonite

[Mossrute]

Thank you.

I found it in Goleta at the beach mixed in with many other rocks.

a metal blade easily scratches it.

vinegar reacts mildly (bubbles).

 

Yes, according to the map it is Miocene, marine sedimentary.

[DPS Ammonite]

Since it fizzes in acid it is limestone or lime rich rock and not siliceous diatomite.

 

See if you can narrow down the formation:

 

https://pubs.usgs.gov/of/2007/1403/downloads/pdf/OF07-1403_map.pdf

[Mossrute]

I ended up having to use a different map (attached).

Goleta Geo Map .pdf

It was very difficult to pinpoint the location. The map does not seem accurate when compared to google earth.

However. I am fairly certain I figured it out: I think it is "Tmm."

 

Here is a screen shot of the description from  the PDF:

 

 

 

If not "Tmm" then it is probably "Qls", but more likely the former.