Wednesday, April 23, 2014

Re: [Geology2] Piece of Africa Found Under Alabama



Regarding Elmwood Smith County TN:  They are de-watering at least one of the mines for ultimate reworking there in Carthage, TN.  There are samples of the sphalerite in dolomite to be had outside the mine property enteance.  However, some enterprising dealer has already been through the region picking up miner collected specimens--but you are welcome to come rebeat the circuit for left behind fruit.  I haven't been able to find any myself.  So I imagine we'll have to wait another 5 years for new specimens to start reappearing.

Eman

On Tuesday, April 22, 2014 10:35 PM, Kim Noyes <kimnoyes@gmail.com> wrote:
 
Once I get to Cal Poly and get some financing then I can afford a trip next year Lord willing and the K-T Creek don't rise.

BTW, that is Elmwood Fluorite... and Calcite and Galena, and Sphalerite and Dolomite and so on. Elmwood #1 and #2 in Carthage, Smith County, Tennessee. Mines are closed again but there has got to be a bunch of yard rock of that material and yard sale material and old rock shop material sitting around waiting to be plundered... and maybe rockhound for some float material in the creeks and roadcuts in the vicinity.

Kimmer


On Tue, Apr 22, 2014 at 7:24 PM, Lin Kerns <linkerns@gmail.com> wrote:
 
That black rock, as I found out later, is Gabbro. It's dense and it's heavy and to my chagrin, it's volcanic. But it is a plutonic basalt. That is, it formed beneath, but never made it to the surface as a hot, melty glob of lava. It's fairly common around areas of volcanism, but I found this character on the San Andreas Fault, in a sediment filled gap between the Pacific and N. American plates near Palm Desert.

And yes, I've had a blast collecting all that I have in my meager collection. Most of what I do have is at my dad's house. As soon as I can get my hands on it again, I will photograph it. I plan on getting back down to Coon Creek and doing more collecting and hopefully seeing some local herps, as well.

Now, this begs a story - that iridium, k/t boundary site Kim is interested in is on the lower bank of a creek that was flooding at the time I was there. We all waded chest deep water to get to the other side. One guy that was with us reached out for a branch, then screamed like a girl. He almost man-handled a water snake (Natrix sp.) I almost drowned laughing so hard because my knees gave out. I tried to catch it but by the time I leveled out, it had too much of a head start. The rest of the day all you could hear was someone screaming like that poor guy.

And that's just one of many adventures I've had hunting fossils. I'll share more of them, later, on the blog.

I just need Kimmer to get his arse down here so we can go to Illinois and Middle TN to find the Fluorite. I haven't done much homework on the TN site, but I have all kinds of maps and info for Hicks Dome and Cave in the Wall, in Illinois. HINT HINT. And of course, I'd like to take him to Missouri and Arkansas and show him all the 1811-12 quake damage.

Lin


On Tue, Apr 22, 2014 at 8:45 PM, Allison Maricelli-Loukanis <allison.ann@att.net> wrote:
 
Hi LIn, this is fascinating... there was one black rock next to the red chert.. is that obsidian? What a grand collection and how much fun was that to put together? Thanks.. looking forward to the other parts. Allison

From: Lin Kerns <linkerns@gmail.com>
To: Geology2 <geology2@yahoogroups.com>
Sent: Tuesday, April 22, 2014 6:38 PM

Subject: Re: [Geology2] Piece of Africa Found Under Alabama

 
Here's some of the fossils I've collected from the Coon Creek formation and the surrounding area:

http://1roxxfoxx.blogspot.com/2012/04/adventures-in-fossils-part-1.html


Eman...

I have a question. Is the extinct volcano sitting beneath the coliseum in Jackson, MS related to this suture?

Thanks!

Lin


On Tue, Apr 22, 2014 at 8:33 PM, Allison Maricelli-Loukanis <allison.ann@att.net> wrote:
 
Really interesting.. I would love to go and sit on that gorgeous coast. Allison

From: MEM <mstreman53@yahoo.com>
To: "geology2@yahoogroups.com" <geology2@yahoogroups.com>
Sent: Tuesday, April 22, 2014 6:12 PM
Subject: Re: [Geology2] Piece of Africa Found Under Alabama

 
In case any list members are planing a field trip to the South East--As to Georgia And Alabama geology which gave rise to the geography:  this is why there is volcanic-derived soil on the South Georgia plane that make onions from Vidallia  so sweet.

 It also accounts for the kaolin belt between Columbus and Macon where the basement rock was uplifted to the surface and hydro- theromal broke them down into constituent parts and then sorted them into layers.( Collecting vic Butler, GA) The water saturated clays are plastic/buoyant and squeeze up into the red New Providence Formation.  They behave somewhat like the salt of salt domes in Louisiana and Texas. See New Providence State Park aka The Grand Canyon of Georgia.

These heated waters also broke down the graniteoid bedrock vic La Grange Georgia ( GA/AL stateline) where at the Hogg Mine( fee dig) literal boulders of gemy rose quartz formed as micro-needles of plagioclase feldspar were carried along with the rock quartz by that process. To the west of La Grange but to the east of Talladega AL is a large deposit of black tourmaline/schorl in quartz. Mapquest "Tourmaline Road" and you are there -lol.

This suture generally follows what is known as the "fall line" which is a string of "rapids" from Columbus to Athens and gave rise to the industry/mills in those towns along its transition of resistant basement --now surface rocks onto the sedimentary clays, marls, and chalks which make up mid southern Georgia.  (Columbus, Macon, Athens and others were important heavy industry towns during the Civil War owing to the natural hydro-power the falls offered). 

The Ripley formation of "Coon Creek fame" is one of those marls. Lynn lives a top some of its exposures, this formtion covers much of the area below the fall line and curves all the way up through East Memphis and into Missouri--perhaps into Iowa.  Very few of the out-wash sediments in this area lithofied( turned to rock) so fossil collecting is easier than most other places. And those fossils are preserved in great detail. Follow gullies and runoffs aside the roads.  I have shells from the Ripley and Ewtoh formations that have hair thin spines still intact. Shark and skate teeth are common.

 I would be remiss to not mention Wetumpka Crater where an asteroid 81-81 mybp formed a 4-5 mile wide crater. And in Beckly and Dodge Counties east of Macon are where Georgia tektites have been found (although rarely and not in recent years).  These are splatter forms from the Chesapeake Astrobleme 34mybp.  Graves Mountain south east of Atlanta is likely related to the suture and is open to organized clubs/collecting groups several times a year.

While the soils from the volcanic island arc remain in south Georgia--forming as the Africa plated closed in on the NA plate in the Permian( 250mybp), there is strangely no evidence of basalt flows filling the gap during the rift at the beginning of the Triassic( 190mybp) like we see outside New York City and Paterson NJ. Perhaps these beds if they exist are deeply buried by Cretaceous and earlier sediments Above the fall line the rocks are 1.2-1.3 billion years old. Walk down stream a few feet and the rocks(sic) are 82-68 million years old. 3 miles further and they are post-cretaceous. 60-40Mybp.

Much of the soil below the suture is very, very, sandy so if in Americus, stop in and see Jimmy Carter's peanut farm or if you are headed to the Froggy Bottom-- Ripley collecting area, Westville in Lumpkin Georgia is a working 1840's town where you can help wash kaolin clays for the pottery works.

If you've read this far most of these exposures/sites/formations can be visited over a 3 day trip.  So pack your collection bags--rock hammer optional.

Eman

On Tuesday, April 22, 2014 6:22 PM, Lin Kerns <linkerns@gmail.com> wrote:
 
A scene from Alabama's Gulf Coast.

Piece of Africa Found Under Alabama

Apr 22, 2014 // by Larry O'Hanlon
Geoscientists have identified a chunk of Africa stuck onto the southeastern United States.
A long mysterious zone of unusual magnetism that stretches from Alabama through Georgia and offshore to the North Carolina coast appears to be the suture between ancient rocks that formed when parts of Africa and North America were pressed together 250 million years ago. If so, Africa could have left a lot more behind in the American southeast when the conjoined continents rifted apart and formed the Atlantic Ocean.
"There are some large faults in the magnetic data," said geologist Robert Hatcher of the University of Tennessee in Knoxville, regarding what is called the Brunswick Magnetic Anomaly and other magnetic features in the region. "They have not been active for a very long time. They are strike-slip faults like the San Andreas today. But there's also younger fall with opposite direction."
Play Video

On a recent dinosaur dig Kasey-Dee Gardner noticed that fossils not only come in all shapes and sizes, but also in all different colors.
The faults appear to be the remains of the collision and then messy divorce of Africa and North America.
"There was an attempt to rip away Florida and southern Georgia," said Hatcher. "So you have a failed rift there. We know there's a suture there between African crust and newer crust from the Appalachians. There are pieces of crust that started in Africa."
A rift is what happens when the crust is pulled apart. When that happened 200 million years ago, 50 million years after African and North America collided, it appears to have started near the old collision zone, but then shifted to weaker crust to the east.
That rift zone split open and caused volcanic eruptions which created new oceanic crust -- what is today the crust of the Earth under the Atlantic Ocean. The rifting continues today at what's called the Mid-Atlantic Ridge.
"The age of the suture zone is believed to be about 250 million years old, but that's not very well constrained," said geologist Elias Parker, Jr., of the University of Georgia in Athens. He published a paper reviewing what's known about the Brunswick Magnetic Anomaly in the latest issue of GSA Today.
The big challenge in sorting out the history of the southeast U.S. is that there are intriguing magnetic signals, as well as gravimetric measurements, but there is not enough deep borehole studies or seismic data to confirm the faults and the proposed scenarios.
"There are deeper faults and more shallow features," said Parker. "It makes the interpretation really challenging."
Among the seismic projects that could help increase the resolution of the structures, said Parker, is the Southeastern Suture of the Appalachian Margin Experiment (SESAME) and the Suwanee Suture and Georgia Rift Basin Experiment.
"This is just the start to understanding the structure of the southeast U.S.," said Parker. "What I'm trying to do is come up with a simple explanation for this."


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