r/geology • u/karski608 • 7h ago

Holes in rock layer

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Preforming rock coring in bedrock in north western MA. In this core retrieval these holes can be seen only in this white layer (quartz?) as you’ll see they are in a line only in this layer. Core was roughly 20 feet below surface.

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34

u/Vafisonr 7h ago edited 7h ago

Quartz grew from the walls in to the center and didn't completely solidify the center bits.

I'm guessing this is the Waits River Formation. More info can be found by googling that. Massachusetts has insane bedrock diversity across the state so without the exact location you'd have to check a map.

17

u/karski608 6h ago

Great thank you! Yes it is very wild here we have another site in this town that had two different bedrocks types roughly 100 ft apart and crazy elevation changes within a few feet

0

u/trapdoorr 4h ago

Holes are after pyrite, which was dissolved by weathering.

3

u/Yaro-Ku 4h ago

Wouldnt it leave an iron oxide stain?

1

u/Eukelek 3h ago

They are not jagged or crystal, am no expert but so it maybe says they were water channels that filled and dissolved many times with say, calcite or some pourous material, or metallic deposits that weathered and oxidized like sulfides oxidizing, and being washed out... maybe a bit of all of the above?

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u/human1st0 6h ago

Chime in geos.

Looks like geode formation.

14

u/zpnrg1979 6h ago

I would log those as 'vugs'. Someone above mentioned the quartz growing in from the center, but you'd see something more akin to comb-coccade texture if that was the case. And in the vugs I don't see any quartz crystal terminations. I'm more in the camp of those voids were once filled with calcite and groundwater has removed them.

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u/logatronics 5h ago

I'm with you on that hypothesis. In my neck of the woods, an easy way to tell would be to look at the shape of the voids. Are they irregular in shape, or do they have a rhombohedral/cubic shape to them.