CC373: Pristine ammonite and bivavle fossils

Claim CC373:

Mud springs near Swindon, Wiltshire, England produce fossils, supposedly about 165 million years old, of remarkable preservation. Some bivalves still have their original organic ligaments, and ammonites are irridescent and still have their original shells of aragonite, a metastable form of calcium carbonate.

Source:

Snelling, Andrew A. 1997. A '165 million year’ surprise. Creation 19(2): 14-15. http://www.answersingenesis.org/creation/v19/i2/surprise.asp

Response:

The ammonites are well preserved but still consistent with an age of 165 million years. Although the microstrucure of the bivalve ligaments is preserved, their organic material is not. Irridescent fossils are not uncommon from mudrocks of that age. Dr. Hollingworth, cited secondhand in the source for this claim, wrote,
The bivalves found at the Wootton Bassett Mudspring come from the Upper Jurassic, Oxfordian Ampthill Clay Formation and are very well preserved. Several specimens of the bivalve Myophorella have been found articulated with the ligament still preserved and retaining original microstructure. The organic material has been replaced by hydroxyapatite. Aragonite is metastable but in mudrocks is sometimes still preserved due to the impermeable nature of the sediment, especially when compacted. (Hollingworth 2005; see also Harding et al. 2000)

References:

Harding, I. C., J. Armitage, N. Hollingworth, and N. Ainsworth. 2000. Sourcing mudsprings using integrated palaeontological analyses: An example from Wootton Bassett, Wiltshire, England. Geological Journal 35: 115-132.
Hollingworth, 2005. Letter to Jon Fleming. In: Preservation of 165 Mya organic ammonite ligaments?, talk.origins, May 2, 2005.

Previous Claim: CC371.1 | List of Claims | Next Claim: CC381

created 2005-5-2