Radioactive nodules 50 - 200 mm in size can be found in Littleham Bay rocks and even on the beach.

Does anyone know of other places they can be found ?

https://southwestcoastphotos.com/photo_16759619.html

Colorado, Utah and Oklahoma in the US.

https://www.usgs.gov/publications/uranium-bearing-carbonaceous-nodules-southwestern-oklahoma

https://nmgs.nmt.edu/publications/guidebooks/downloads/32/32_p0165_p0170.pdf

Just now, swansont said:

Colorado, Utah and Oklahoma in the US.

https://www.usgs.gov/publications/uranium-bearing-carbonaceous-nodules-southwestern-oklahoma

Thanks, your link works, but not the pdf.

The Littleham rocks are clastic sediments (soft silstones and mudstones of permo-trassic age (200 - 250 mya) and form part of the 'red coast'.

1 hour ago, studiot said:

Radioactive nodules 50 - 200 mm in size can be found in Littleham Bay rocks and even on the beach.

Does anyone know of other places they can be found ?

https://southwestcoastphotos.com/photo_16759619.html

What’s the origin of the nodules? I note the Oklahoma ones are over 40% carbon. Since I’m aware crude oil has vanadium and other heavy metals in it , I wonder if these nodules may be derived from petroleum seepage or something, from deeper lying rocks.

1 hour ago, studiot said:

Thanks, your link works, but not the pdf.

Replaced with link

Just now, exchemist said:

What’s the origin of the nodules? I note the Oklahoma ones are over 40% carbon. Since I’m aware crude oil has vanadium and other heavy metals in it , I wonder if these nodules may be derived from petroleum seepage or something, from deeper lying rocks.

This study seems to support your notion, although the jury is still out.

esp see pages 12 - 14

https://nora.nerc.ac.uk/id/eprint/509450/1/WP92001.pdf

Dr Ian West of Southampton University ( specialist in Wessex geology and petroleum geology) currently runs courses along there

https://wessexcoastgeology.soton.ac.uk/Budleigh-Salterton.htm

Interesting. I had some work involvement with the Wytch Farm development back in the nineties. The hydrocarbon source is the same early Triassic Sherwood Group sandstones that underlie your Littleham nodule beds.

So upwards migration via local faulting of reducing fluids from that source is quite reasonable.

As @studiot's reference suggests, the primary source for the uranium and other exotic metals is almost certainly from weathering of the Exmoor granite a little to the north.

Just now, sethoflagos said:

Interesting. I had some work involvement with the Wytch Farm development back in the nineties. The hydrocarbon source is the same early Triassic Sherwood Group sandstones that underlie your Littleham nodule beds.

So upwards migration via local faulting of reducing fluids from that source is quite reasonable.

As @studiot's reference suggests, the primary source for the uranium and other exotic metals is almost certainly from weathering of the Exmoor granite a little to the north.

Sorry I missed a reference to Exmoor granite could you point it out please.

I say this because I would not expect to find any Exmoor granite since the entire Exmoor area is sedimentary, not plutonic.

Are you sure you don't mean Dartmoor ? or even the volcanic activities outliers around Exeter, associated with the SW peninsula granite intrusion and batholith ?

Littleham is at point 15 A on the attached map.

Edited June 4Jun 4 by studiot

23 minutes ago, studiot said:

Sorry I missed a reference to Exmoor granite could you point it out please.

I say this because I would not expect to find any Exmoor granite since the entire Exmoor area is sedimentary, not plutonic.

Are you sure you don't mean Dartmoor ?

Sorry, senior moment. Deposition came from south and west so that's Dartmoor as you say.

Well spotted!

14 hours ago, studiot said:

This study seems to support your notion, although the jury is still out.

esp see pages 12 - 14

https://nora.nerc.ac.uk/id/eprint/509450/1/WP92001.pdf

Dr Ian West of Southampton University ( specialist in Wessex geology and petroleum geology) currently runs courses along there

https://wessexcoastgeology.soton.ac.uk/Budleigh-Salterton.htm

So the greenish colour of the nodules is Fe(II), reduced from the general red/brown Fe(III) of the sandstone by the presence of hydrocarbons, as indicated by the high carbon content of the nodules.

What is interesting is not so much the source of the minerals, but the mechanism of their accretion or aggregation.

More recent studies have veered away from the carbon theory and apparantly the nodules aaggregated some tens of millions of years after the sediment was laid down.

Although on my simplified map the volcanic rocks around Exeter are shown as granite, there are also outcrops of other volcanics that are a more likely source, especially as the nodules do not seem to appear in the more northerly Mercia series.

The new red sandstone is part of the Mercia group , which is more widespread, and here is some very modern information, from Dave Green.