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Since I asked it, this isn't a dumb question (is older up or down?)


SteveE

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As they said in school the only dumb question is the unasked one.   So here goes... Instead of wasting field time fumbling around trying to figure this out, could someone please tell me how to read these sorts of section descriptions?  Is the top of the printed list the top of the rock layer or the bottom?

SectionExample.png

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The top shows the newer rocks deposited on top of progressively older layers following the law of superposition. 

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@SteveE

Not a dumb question at all. 

We all needed to learn and start somewhere. :) 

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It's only dumb if you don't know something and don't ask questions or look for an answer. :)

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Good question as it is implicit and thus not explicitly stated. Folks who are new to reading these stratigraphic reports can easily be confused. Thankfully, the standard is to show the layers in the same orientation that they appear in the field. If the standard had somehow been chosen in the reverse order--progressing from older to younger but writing down from the page as we do, this would really be confusing to those not in the know.

 

 

Cheers.

 

-Ken

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There are occasions in older literature where the numbering starts at the top of the sequence. The important Speeton Beds, Lower Cretaceous of Yorkshire, UK is the only example I can think of where this is still retained though I expect there are others. It goes from A beds at the top down to D beds at the base, and with numbered subdivisions that go the same way.

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Tarquin

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30 minutes ago, Tidgy's Dad said:

The top shows the newer rocks deposited on top of progressively older layers following the law of superposition. 

 

Interesting tact, @Tidgy's Dad! Fortunately the tables conform to the stratigraphic column. For once, paleo science did something the easy and sensible way :D 

 

Here in the Atlantic Coastal Plain, many of our outcrops have water at the base (bay, rivers, creeks), so the strat tables have a notation the water line at the bottom. Its a nice little cheat when you get to thinking sideways (which happens sometimes when you've been comparing multiple sections and they just don't seem to line up).

 

PS:

law of superposition

 

noun

Geology. a basic law of geochronology, stating that in any undisturbed sequence of rocks deposited in layers, the youngest layer is on top and the oldest on bottom, each layer being younger than the one beneath it and older than the one above it.
 

 

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Also...

I nominate this post for the non-existent (but badly needed) award for the best thread title of the year 

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@SteveE

All on-topic questions are valuable (we would not exist without them!). The big picture is that, for every fundamental or elementary question posited, there will be a good percentage of our 30,000 unique visitors every month who will learn from it. Well Done!  :)

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Thanks everyone!  It's obvious when looking at a stratigraphic diagram, but here in print the numbering on the left was a curveball

 

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1 hour ago, sharkdoctor said:

Also...

I nominate this post for the non-existent (but badly needed) award for the best thread title of the year 

:default_rofl:

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9 hours ago, SteveE said:

the only dumb question is the unasked one. 

Well said sir! :thumbsu:

The good thing about science is that it's true whether or not you believe in it.  -Neil deGrasse Tyson

 

Everyone you will ever meet knows something you don't. -Bill Nye (The Science Guy)

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