[Rockhounds] Rockhounds Digest, Vol 35, Issue 5

[Robert Bennett III]

Re: Tomales Bay, CA, And Bolinas

The geology in and around Tomales, Bolinas and Stinson are fascinating.  Subduction zone volcanics, deposition by incoming sea floor and more.  The bays from Tomales and Bolinas are created by the San Andreas fault, which is separating, moving the beaches away from the headlands.  I do question the explanation of gravel deposition by the water surge as being limited to a rush of climate produced glacial or heavy rains.  The bays being caused by the fault will on occasion of fault movement, open and suddenly the water will disappear into the fault.  The fault then may close and eject the water violently and or the seawater will rush into the created void with equal violent speed.  This may be a viable explanation, depending upon the condition of the fault and bays at the time the fossil/s were covered.

On my last trip to Bolinas my Daughter and I observed a wale skeleton, buried in the sand, (not a fossil), beach agates and a biomimicrite containing pyrite in various cracks. I don't know what the rules are about collecting on this beach.

Thanks,
Bob
----------------------------------------------------------------------

-----Message: 1
-----Date: Wed, 6 Nov 2019 19:30:07 -0600
-----From: Paul <etchplain at att.net>

---Scientists hope ancient Tomales Bay mammoth molar holds clues to prehistoric environment The Press Democrat, October 11, 2019 --------------
----- https://link.zixcentral.com/u/5cb287b3/WPUnV5YB6hGg6sUn9u_1Kg?u=https%3A%2F%2Fwww.pressdemocrat.com%2Fnews%2F10135759-181%2Fpaleontologists-hopes---ancient-mammoth-molar

----Mammoth molar found on bay beach holds clues Point Reyes Light, October 16, 2019 --https://link.zixcentral.com/u/63fcc543/hBQoV5YB6hGg6sUn9u_1Kg?---u=https%3A%2F%2Fwww.ptreyeslight.com%2Farticle%2Fmammoth-molar-found-bay-beach-holds-clues

---ACR family member makes mammoth find on
---Tomales Bay. ACR Conservation in Action
----https://link.zixcentral.com/u/203ed868/yjIoV5YB6hGg6sUn9u_1Kg?u=https%3A%2F%2Fwww.egret.org%2Facr-family-member-makes-mammoth-find-tomales-bay

---Tomales Bay
---https://link.zixcentral.com/u/d66d9a84/YFEoV5YB6hGg6sUn9u_1Kg?u=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FTomales_Bay

---Ice Age clues near Bodega. Scientist thinks mammoths rubbed coast rocks 12,000 years ago By Peter Fimrite, SF Gate, December 3, 2006 -- 
----https://link.zixcentral.com/u/06ae58a7/3m4oV5YB6hGg6sUn9u_1Kg?u=https%3A%2F%2Fwww.sfgate.com%2Fbayarea%2Farticle%2FIce-Age-clues-near-Bodega----Scientist-thinks-2466058.php

----Mammoth Rocks, California
----https://link.zixcentral.com/u/7f99c4b3/dI0oV5YB6hGg6sUn9u_1Kg?u=https%3A%2F%2Fwww.parks.ca.gov%2F%3Fpage_id%3D23566
----https://link.zixcentral.com/u/bbccb623/lKkoV5YB6hGg6sUn9u_1Kg?u=https%3A%2F%2Fwww.parks.ca.gov%2F%3Fpage_id%3D23822

---Yours,

---Paul H.