Unknown Among Dendraster Specimens

[AncientEarth]

I'm not sure if this is a partial bone fragment or plant remains, but I have been finding this and others, all of the same general diameter, just partial segments or broken lengths amongst these Dendraster ashleyi specimens while I blast them clean. This one almost comes to a closure like it was crimped shut on the end.

Anyone familiar with this Pliocene age material have an idea in mind?

Thank you

Aaron

[Auspex]

Could it be a lined burrow?

[AncientEarth]

That's actually a good possibility and would explain the "crimping". There are known shrimp/lobster burrows from Pliocene/Pleistocene in the region, just nothing quite this small.

[Indy]

That's actually a good possibility and would explain the "crimping". There are known shrimp/lobster burrows from Pliocene/Pleistocene in the region, just nothing quite this small.

Baby shrimp

[siteseer]

Aaron,

Before Chevron stopped allowing fossil collecting on the Kettleman Hills property (Kings County, CA), I used to do some hunting in the Etchigoin and San Joaquin Formations (Early Pliocene, Late Pliocene respectively) but never found anything like that. My only guess would be a worn large crab claw tip but then I wouldn't expect the rather delicate ashleyi specimens to be in that good a shape. It doesn't look like bone.

Jess

I'm not sure if this is a partial bone fragment or plant remains, but I have been finding this and others, all of the same general diameter, just partial segments or broken lengths amongst these Dendraster ashleyi specimens while I blast them clean. This one almost comes to a closure like it was crimped shut on the end.

Anyone familiar with this Pliocene age material have an idea in mind?

Thank you

Aaron

Edited August 19, 2013 by siteseer

[AncientEarth]

Thanks for the input Jess

I think I have come across hints of the Etchegoin Frm here in the extremities of SLO county, but not anywhere near where this was found, this is from the Careaga Formation, as far as I know, from near Lompoc.

There are a couple crab spots known, but nothing in this loose sandy material I've heard of, almost entirely shale type localities for those. Would be pretty awesome to find a crab, but on this I am leaning towards a small burrow.

[Plantguy]

Hey Aaron, enjoyed seeing some familiar finds. I did some collecting up in Norcal years ago in the Plio-Pleistocene Merced Fm. I think Lake Merced was isolated from any of the Socal material.

Here's a small Dendraster and a crab leg....

Sediments were pretty much loose sand with isolated calcareously cemented lens. Thinking your tube is more like some of the burrows we found as well that I dont have any samples of any longer...

Regards, Chris

[AncientEarth]

Hi Chris,

I am not familiar with the Merced Frm, what makes you think it is not in relation to anything in Central CA or southern?

What you described as loose sand and cemented areas sounds very much like this part of the formation. There are even Dendrasters found in concretions to the East of this site, more akin to Monterey Frm type material.

Hopefully I can find a more complete burrow in this material, only one I have seen from this area (a bit further south) was about 10x as large, but still that's about 100x smaller than those on my ranch, I can fit my fist into those.

Thanks for the additional input, if you come across any old photos of specimens I would be interested in seeing them.

[siteseer]

I have seen a few great white shark teeth from the Careaga Sand.

I once collected at a site in Daly City (just south of San Francisco). The layer had been considered by some geologists to be the Merced but others thought it was just about the same age and they put Merced in quotation marks. I found several sand dollars of the species Scutellaster interlineatus, a gastropod, and a crab claw. The weird thing about that site was that it was also in the San Andreas Fault Zone. Many of the sand dollars were distorted, some even looking like they had been broken and glued back but offset by just a couple of millimeters.

I have been told you can find Merced Formation fossils near or at a dump (landfill) in Sonoma County.

Jess

Thanks for the input Jess

I think I have come across hints of the Etchegoin Frm here in the extremities of SLO county, but not anywhere near where this was found, this is from the Careaga Formation, as far as I know, from near Lompoc.

There are a couple crab spots known, but nothing in this loose sandy material I've heard of, almost entirely shale type localities for those. Would be pretty awesome to find a crab, but on this I am leaning towards a small burrow.

[Plantguy]

Hi Chris,

I am not familiar with the Merced Frm, what makes you think it is not in relation to anything in Central CA or southern?

What you described as loose sand and cemented areas sounds very much like this part of the formation. There are even Dendrasters found in concretions to the East of this site, more akin to Monterey Frm type material.

Hopefully I can find a more complete burrow in this material, only one I have seen from this area (a bit further south) was about 10x as large, but still that's about 100x smaller than those on my ranch, I can fit my fist into those.

Thanks for the additional input, if you come across any old photos of specimens I would be interested in seeing them.

Seems like I remember discussions about those deposits being somehow isolated from SoCal as the San Andreas Fault and other resulting fault zones were continuing to slice thru the state with the Pacific tectonic plate moving north relative to the N.American plate. Its been a very long time since I roamed those Norcal hills so maybe Bobby and some of the others with more familiarity with current/newer research/theories of the area can provide input. I'm wondering if we are talking about contemporaneous deposits that are simply on different sides of a major plate boundary?

As Jess mentioned above these are indeed finds from Sonoma County. Here are a few more really tiny ones...

Nassarius sp. and Polinices sp. on the left and center...I dont remember the other one on the right...and havent unfortunately finished labeling them.

Regards, Chris

[AncientEarth]

I have seen a few great white shark teeth from the Careaga Sand.

I once collected at a site in Daly City (just south of San Francisco). The layer had been considered by some geologists to be the Merced but others thought it was just about the same age and they put Merced in quotation marks. I found several sand dollars of the species Scutellaster interlineatus, a gastropod, and a crab claw. The weird thing about that site was that it was also in the San Andreas Fault Zone. Many of the sand dollars were distorted, some even looking like they had been broken and glued back but offset by just a couple of millimeters.

I have been told you can find Merced Formation fossils near or at a dump (landfill) in Sonoma County.

Jess

The teeth come from another part of the Careaga Sand Frm. I believe Careaga is divided up into at least 4 sections, I've had problems finding recent info on the layer, seems it had a revision in at least age at some point. The Odontocete specimens I posted here: http://www.thefossilforum.com/index.php?/topic/40693-late-pliocene-odontocete-fossils-from-california/ are from that teeth bearing layer, another which is distorted from fault activity.

The spot in Daly City sounds interesting, these Dendrasters aren't along the SA fault as far as I know, but another locality I collect, which is, can produce very distorted and sometimes agatized Astrodapsis sp. that have folded over themselves and preserved that way.

Seems like I remember discussions about those deposits being somehow isolated from SoCal as the San Andreas Fault and other resulting fault zones were continuing to slice thru the state with the Pacific tectonic plate moving north relative to the N.American plate. Its been a very long time since I roamed those Norcal hills so maybe Bobby and some of the others with more familiarity with current/newer research/theories of the area can provide input. I'm wondering if we are talking about contemporaneous deposits that are simply on different sides of a major plate boundary?

As Jess mentioned above these are indeed finds from Sonoma County. Here are a few more really tiny ones...

Merced Formation Small Gastropods.jpg

Nassarius sp. and Polinices sp. on the left and center...I dont remember the other one on the right...and havent unfortunately finished labeling them.

Regards, Chris

Good point, I am curious too where the line is drawn for separation in a geological/fossil record to overlap, like today, for species interaction and settlement over the terrain. Those specimens aren't ones I am familiar with from reading local fauna lists, so maybe there is some reason for the separation theory aside from a geological plate boundary.