vgabndo
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Does anyone know the geology of these La Bocana sandstones?
Just south of La Bocana there are uplifted sandstones in eroded layers with some of them exhibiting this formation on the upper edge. Very curious. I
don't suppose it is any use asking that we keep this to geology?
Undoubtedly, there are people who cannot afford to give the anchor of sanity even the slightest tug. Sam Harris
"The situation is far too dire for pessimism."
Bill Kauth
Carl Sagan said, "We are a way for the cosmos to know itself."
PEACE, LOVE AND FISH TACOS
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vgabndo
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Here's the side view of the nose cone shown before. They appear to be pure sandstone, and there were several similar "nose cones".
Undoubtedly, there are people who cannot afford to give the anchor of sanity even the slightest tug. Sam Harris
"The situation is far too dire for pessimism."
Bill Kauth
Carl Sagan said, "We are a way for the cosmos to know itself."
PEACE, LOVE AND FISH TACOS
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mtgoat666
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| Quote: | Originally posted by vgabndo
Does anyone know the geology of these La Bocana sandstones?? Very curious. I don't suppose it is any use asking that we keep this to geology?
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Concretions in siltstone, sandstone are simply zones of rock that are more competently cemented, and weather more slowly,... so they stand out as
spherical. Sometimes concretions formed like this because of dead critter causing localized geochemical conditions -- in some sed rocks I have seen
where you crack the concretions with a hammer and find a fossil in the heart of many of the concretions.
Don't really know Bocana area, but based on general Baja geology, I hazard an educated guess that the sedimentary rocks are probably Miocene (5 to 23
million years old).
p.s. republicans don't fund basic science research, so if scientific knowledge is what you seek, ask a democrat!
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mcfez
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| Quote: | Originally posted by vgabndo
Just south of La Bocana there are uplifted sandstones in eroded layers with some of them exhibiting this formation on the upper edge. Very curious. I
don't suppose it is any use asking that we keep this to geology? |
I'm just a stupid guy here but....
These rocks look like they have been rolling back and forth in a water wave action (?)
Old people are like the old cars, made of some tough stuff. May show a little rust, but good as gold on the inside.
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Geo_Skip
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mtgoat666 has it exactly right!. Good to fins another commenter who has some Geology comprehension.
Expect fossils in many concretions ( shells)...they are a b-tch to break though..I have a nasty scar on my left thumb from my rock hammer thanks to a
Plio-Pleistocene concretion from the Border Park area just north of the border at Tijuana. By the way, the border fence was three rusted strands of
barbed wire which wands broken down and buried in sand in 1975!
Great fossils though!
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BigOly
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Now this is interesting.
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vgabndo
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I was amazed at the purity of the sandstone. I couldn't find anything that wasn't sand. Just a clue. and multiple nosecones.
Undoubtedly, there are people who cannot afford to give the anchor of sanity even the slightest tug. Sam Harris
"The situation is far too dire for pessimism."
Bill Kauth
Carl Sagan said, "We are a way for the cosmos to know itself."
PEACE, LOVE AND FISH TACOS
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vgabndo
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Another view
Undoubtedly, there are people who cannot afford to give the anchor of sanity even the slightest tug. Sam Harris
"The situation is far too dire for pessimism."
Bill Kauth
Carl Sagan said, "We are a way for the cosmos to know itself."
PEACE, LOVE AND FISH TACOS
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Bob H
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| Quote: | Originally posted by Geo_Skip
mtgoat666 has it exactly right!. Good to fins another commenter who has some Geology comprehension.
Expect fossils in many concretions ( shells)...they are a b-tch to break though..I have a nasty scar on my left thumb from my rock hammer thanks to a
Plio-Pleistocene concretion from the Border Park area just north of the border at Tijuana. By the way, the border fence was three rusted strands of
barbed wire which wands broken down and buried in sand in 1975!
Great fossils though! |
Geo Skip.... you should get in touch with Georock on this board. She is very good at this stuff also!!
Bob H
The SAME boiling water that softens the potato hardens the egg. It's about what you are made of NOT the circumstance.
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BajaDanD
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There are rock formations in the estuary under water that are shaped just like the one in your picture. also as you drive the road along La bocana
estuary you will see the same rocks in many places along the road
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woody with a view
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so there are whale vertebrae fossils inside?
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DENNIS
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Here....Have fun.
--------------
Coastal evolution of Late Cretaceous and Pleistocene rocky shores: Pacific rim of northern Baja California, Mexico
Markes E. Johnson1, Jorge Ledesma-Vázquez2, Hovey C. Clark3 and Jennifer A. Zwiebel3
1Department of Geology, Williams College, Williamstown, Massachusetts 012672Area de Geología, Universidad Autónoma de Baja California, Ensenada, Baja
California, Mexico 228003Department of Geology, Williams College, Williamstown, Massachusetts 01267
Abstract
Cretaceous on Cretaceous and Pleistocene on Cretaceous unconformities are mapped throughout a 45 km2 field area surrounding the village of Eréndira on
the Pacific coast of northern Baja California, Mexico. The unconformities represent a late Pleistocene rocky shore (120000–130000 ka) directly
superimposed on a Campanian–early Maastrichtian rocky shore (77–70 Ma). Superb exposure and preservation of coastal features allow for precise
paleogeographic restorations. Physical analysis includes a comparison of rocky-shore composition, configuration, and overall length. Paleoecological
analysis permits the recognition and comparison of preferred wave directions. High-intensity, windward biotas during the Late Cretaceous included
rock-encrusting rudists and coralline red algae, while low-intensity, leeward biotas were characterized by rock-encrusting oysters, scleractinian
corals, and bryozoans. During the Pleistocene, the open coast was exploited by the byssate bivalve Mytilus and boring bivalves including Petricola and
Penitella, while more protected settings were dominated by the gastropods Olivella and Saxidomus. Amino-acid analysis of Saxidomus nuttalli yielded an
age estimate consistent with the last interglacial epoch (oxygen isotope stage 5e). Wave impact was oblique to the paleoshore during the late
Pleistocene; onshore winds were generated from the west. In contrast, wave movement was generated from the east to southeast and parallel to shore
during the Late Cretaceous. Field data are integrated with paleogeographic reconstructions and predictive models, including computer models for local
and global oceanography. Where different paleogeographies and oceanographic models conflict, field mapping of this sort adds a much needed element of
ground truth.
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mcfez
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...... wave movement was generated from the east to southeast and parallel to shore
So....do I win the Chicken dinner for having it right? 
Old people are like the old cars, made of some tough stuff. May show a little rust, but good as gold on the inside.
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Cypress
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DENNIS, Thanks. Thought maybe those Saxidomas had something to do with 'em. Believe the rudists played a larger part than suspected.
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DENNIS
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| Quote: | Originally posted by mcfez
So....do I win the Chicken dinner for having it right?
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Of course. We'll put it in the mail this afternoon. You should receive it by dinner time............around the 18th of the month. YUMMY
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