GeologyRocksInclusions in sandstone deposits. Whangaparaoa peninsular New Zealand.
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Some pictures would be great
Fri, 08/03/2012 - 06:27Some pictures would be great - can you resize your images? We have limited storage space, hence the reason for the file size limit on uploads. An image of 1000x1000 pixels is usually more than enough and with JPEG quality set to about 80% should be << 1Mb in size.
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Sort of sounds like you're
Fri, 08/03/2012 - 15:12Sort of sounds like you're describing an iron concretion. If the sandstone was white, I would almost bet money on it.
This following link isn't about your area, but it explains the formation of iron concretions very well. Page 10 has images of the concretions. Do they look similar to what you found?
http://www.geology.utah.gov/online/pdf/pi-77.pdf
My rock ID track record doesn't look so good lately, so please post a pic and get official confirmation from the forum old timers.
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Inclusions in sandstone deposits. Whangaparaoa peninsular New Zealand.
Submitted by davejenknz on Fri, 08/03/2012 - 02:29.I'd like to ask a question about inclusions that I find in my local rocks.
I live on the Whangaparaoa peninsular 30kms north of Auckland on the North Island of New Zealand.The rocks exposed on the cliffs of the peninsular north coast are typical sandstone, mudstone layers.I've noticed a large number of Inclusions in the older sandstone layers and would like to know some more about them.They are typically discus shaped ranging from a few inches wide to a few feet.They comprise a shell of red/brown hard rock surrounding a mix of brownish fine and corse grains sands. Also included are lumps of mud that are still very plastic.How do these inclusions form?The shell material when split along planes shows a thin layer of blue/black material. What might this material be? Dave P.S. I'd add photos but this site does not seem to want to upload them. They are rather large jpegs >5MB