When dead shells are buried in dense silt, deprived of oxygen, it can be preserved a long time with its own gloss.
Just the color fade following the same process : white becomes yellow, red fades orange, black turns brown. They are named “subfossil” but it is not a scientific name.
Most are from the Pleistocene but some from the late Miocene are very well preserved. Many “orange form” found in shell-list are such “subfossil”.
Patrice Bail
2 Square La Fontaine 75016 Paris
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Le 9 mai 2020 à 17:49, Louis Wang <[log in to unmask]> a écrit :

Dear all,

Is there any articles or your own explanations about why some beached shells(Cypraea, Marginella, Oliva) can keep their gloss but the colors are always yellow and orange, sometimes even pink no matter what kind of colors they used to have?

Thanks and kind regards,
Louis


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