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Reading pleistocene deposits


Jared C

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I've noticed that despite the seeming abundance of Pleistocene deposits shown on geologic maps such as this one (https://txpub.usgs.gov/txgeology/), finding how or where they expose is much more difficult. 

On the geologic maps I use, when I hunt late cretaceous fossils, for example, late cretaceous exposures area all classified specifically with their own names (Eagle Ford, Ozan, Del rio clay, etc.). I can then research each individual formation, and it makes narrowing down spots much easier.

 

It seems that for Pleistocene exposures, there are no "formation names" assigned to them. This makes it hard to make my research about them specific. Obviously some Pleistocene exposures must be better than others, and many probably have their own unique identifying characteristics,  but I can't research any of that, as it seems all the Pleistocene occurrences on the map are just given blanket names like "terrace deposits " or "high gravel deposits".

 

So, how do I direct my research to be successful for finding productive Pleistocene spots? Are there any Texans too who can tell me how the local geology looks with productive Pleistocene stuff? Any or all advice from anyone would help.

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“Not only is the universe stranger than we think, it is stranger than we can think” -Werner Heisenberg 

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From what I've read, Lissie gravel formation exposures and Beaumont clay formation exposures produce Pleistocene material on the Brazos River.

Others likely know more about it than I do.

 

Fleming/Willis formation exposures on the Brazos can produce Miocene material.

 

The material tends to wash up on sandbars and the gravel beds in and around them.

 

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2 hours ago, Jared C said:

I've noticed that despite the seeming abundance of Pleistocene deposits shown on geologic maps such as this one (https://txpub.usgs.gov/txgeology/), finding how or where they expose is much more difficult. 

On the geologic maps I use, when I hunt late cretaceous fossils, for example, late cretaceous exposures area all classified specifically with their own names (Eagle Ford, Ozan, Del rio clay, etc.). I can then research each individual formation, and it makes narrowing down spots much easier.

 

It seems that for Pleistocene exposures, there are no "formation names" assigned to them. This makes it hard to make my research about them specific. Obviously some Pleistocene exposures must be better than others, and many probably have their own unique identifying characteristics,  but I can't research any of that, as it seems all the Pleistocene occurrences on the map are just given blanket names like "terrace deposits " or "high gravel deposits".

 

So, how do I direct my research to be successful for finding productive Pleistocene spots? Are there any Texans too who can tell me how the local geology looks with productive Pleistocene stuff? Any or all advice from anyone would help.

 

You might have to pick an area and walk it.  Pleistocene formations tend to be composed of unconsolidated sediments - not old enough to have formed/compressed into a rock layer.  I have, however, dealt with chunks of tar that might be less than 30,000 years old and they seem to be as hard as any rock I've put a hammer to.   Storms can wash sand and gravel around.  You could make it easier for yourself by scouting where the formation is intersected by a waterway or road and then walk where you can from there assuming it's okay to do that in that area.

 

Doing your own prospecting is hit-and-miss - mostly miss - and it costs gas and time but at least you know where not to go next time.  You will find your own spot if you do it enough times, though.  One time, a friend and I did find a new spot for late Miocene sea urchins by scouting an area that looked promising on a map.

 

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Almost any gravel layer, uncomformably sitting on top of Cretaceous formations in Central Texas, is Pleistocene age.  Bones found in them, in that area, are most often not mineralized.  This may not give you pause when you find a mammoth bone, but it can be confusing or frustrating if it is Bison, Equus, etc.

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The human mind has the ability to believe anything is true.  -  JJ

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Just keep your brain filter flipped on for bone material anytime you are looking for marine fossils where there is stream gravel.  I know you can multi task as I've seen the cool artifacts you've found while fossiling.  Pleisto stuff can pop up unexpectedly.  I found my first mammoth tooth while hunting ammonites, and never found anything else of Pleisto significance in that stream in the dozen years since.

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Grüße,

Daniel A. Wöhr aus Südtexas

"To the motivated go the spoils."

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