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Hello again Fossil Forum,

Last week I posted a few pictures of what I thought might be fossil wood that I found on my property in Southeastern PA (Montgomery County, just over the Philadelphia County line).  It seemed that it was possible that my rocks were fossils, but also maybe not...  One helpful user suggested that I might polish some of the ends (hopefully crossections) of a few pieces.  So below and in the next few replies I will post some pictures of a few pieces, for the polished parts I used a cabbing machine.  I live at the bottom of a relatively steep hill and these pieces were all found within about 50ft of each other.  If there seems to be some variety, that is in keeping with what I found after consulting several geological maps of my area: my property appears to lie at the precise intersection of precambrian, lower paleozoic, and cambrian regions and includes both sedimentary and metamorphic rocks. If not fossil wood, possibly stromatolites?

...or just more interesting rocks??

For discussion purposes I'll number the pieces and put them in separate replies.

Thank you again for any thoughts, information, and opinions!

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  • Hslice changed the title to Fossil Wood in Southeastern PA?
FranzBernhard

#2 could be a fossil, but a fibrous vein is more probable. Difficult!
Franz Bernhard

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3 hours ago, Hslice said:

my property appears to lie at the precise intersection of precambrian, lower paleozoic, and cambrian regions

To quote Bugs Bunny, "no no that's too far back".

It was mid to late Devonian before anything that might really be thought of as wood got started.

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hello!  I grew up in nearby Delco, and am familiar with the geology of the area.  You're located in a metamorphic belt that trends NE-SW. The predominant geologic strata are schists and gneisses, and scattered deposits of serpentine.

 

The items that you have resembles either a quartz or calcite fracture infill or perhaps serpentine.  The fracture infilling occurs when over time, water carrying dissolved ions of silicon, oxygen, carbon, calcium, etc, precipitate out within fractures of the surround rock, forming the flat. This is a common phenomenon, and occurs along faults. Subsequent movement along these faults gauge out small scratches in the fracture infilling minerals (usually quartz or calcite), giving a wood-grain appearance.

 

Alternately, they could be associated with serpentine deposits.  Number 1 and number three remind me of magnesite, which is a fracture-infilling mineral in serpentine.

 

Regardless, I believe this are mineral specimens instead of fossils.

 

If you would like some methods to ID the minerals, let me know.

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21 hours ago, Rockwood said:

To quote Bugs Bunny, "no no that's too far back".

It was mid to late Devonian before anything that might really be thought of as wood got started.

Ah, good to know! Thank you. 

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19 hours ago, hemipristis said:

hello!  I grew up in nearby Delco, and am familiar with the geology of the area.  You're located in a metamorphic belt that trends NE-SW. The predominant geologic strata are schists and gneisses, and scattered deposits of serpentine.

 

The items that you have resembles either a quartz or calcite fracture infill or perhaps serpentine.  The fracture infilling occurs when over time, water carrying dissolved ions of silicon, oxygen, carbon, calcium, etc, precipitate out within fractures of the surround rock, forming the flat. This is a common phenomenon, and occurs along faults. Subsequent movement along these faults gauge out small scratches in the fracture infilling minerals (usually quartz or calcite), giving a wood-grain appearance.

 

Alternately, they could be associated with serpentine deposits.  Number 1 and number three remind me of magnesite, which is a fracture-infilling mineral in serpentine.

 

Regardless, I believe this are mineral specimens instead of fossils.

 

If you would like some methods to ID the minerals, let me know.

Wow. You are so knowledgeable and your explanation was so informative and clear—is just so, so helpful. I feel at once that my dreams are dashed but that my head is fu ll with a much better understanding of the geology of my little corner of Motgomery county. Thank you.

 

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20 hours ago, Hslice said:

Wow. You are so knowledgeable and your explanation was so informative and clear—is just so, so helpful. I feel at once that my dreams are dashed but that my head is fu ll with a much better understanding of the geology of my little corner of Motgomery county. Thank you.

 

you're welcome

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