Rugose? Rudist? CA ID

[mokojin]

Found in San Benito county, CA in the creek beds. We have found clams, sand dollars, barnacles, oysters, scallops, cone shells, and even a whale bone, but this has had us stumped for a year. My first thought was a rugose coral, but after learning about rudists, I am considering that. 

 

 

[DPS Ammonite]

What is the name and age of the formation that contain all the fossils that you mentioned? Eocene to Miocene? Note that rudists are Cretaceous.

[mokojin]

2 hours ago, DPS Ammonite said:

What is the name and age of the formation that contain all the fossils that you mentioned? Eocene to Miocene? Note that rudists are Cretaceous.

How would we figure this out? It is along the San Andreas fault. I have found scallops, coral, and oysters on top of the mountain and in the valleys. 

[Thomas.Dodson]

6 minutes ago, mokojin said:

How would we figure this out? It is along the San Andreas fault. I have found scallops, coral, and oysters on top of the mountain and in the valleys. 

This would typically be done by utilizing geologic maps online and matching what they list to your location. Not necessarily the right quadrangle but here is an example.https://pubs.usgs.gov/publication/ofr79376

 

If you're finding these in creeks not in-situ then some transport and mixing can't be discounted. It appears that Cretaceous outcrops exist in San Benito county in addition to Miocene, Eocene, and others so rudist isn't out of the question. I will say that porous structure is very rudist like to me.

[DPS Ammonite]

If you give us a better location then maybe we can find a geology map.

 

My recollection is that the Cretaceous formations in that area were mostly deep water such as the Panoche Fm. You would not expect rudists there.

 

The overall shape sort of looks like wood. What is the rock made out of? Does the woody area fizz in acid or scratch with a metal knife blade?