Wenlock Series lagerstätte

The Silurian lagerstätte preserved in the limestone Wenlock Series of Herefordshire, England, offers paleontologists a rare snapshot of a moment in time, about 420 Mya. In the formation, layers of fine-grained volcanic ash punctuate a sequence of carbonate muds that were accumulating in a marine environment on the outer continental shelf. In this fine-grained matrix, soft-bodied animals and delicate, lightly-sclerotized chitinous shells are often preserved in three dimensions, as calcitic fossilizations within calcareous nodules. Calcitic fossilization is an unusual feature.

The lagerstätte, discovered and first published in 1996, provides a wider representation of organisms than a conventional fossilizations of shelly and bony elements. The Wenlock Series offers a diverse macrofauna that includes polychaete worms ("Kenostrychus"), sponges, graptolites, a chelicerate ("Offacolus") and a vermiform mollusc ("Acaenoplax"). On the microscopic scale the diverse microfauna includes abundant well-preserved radiolarians.

The delicate Wenlock fossils are difficult to separate from split sections, so Mark Sutton and his team have devised a method of serially grinding sections; from digital photographs three-dimensional "digital fossils" are reconstructed from datasets.

References

* [http://palaeo-electronica.org/2001_1/s2/s2.pdf Mark D. Sutton, Derek E.G. Briggs, David J. Siveter, and Derek J. Siveter, "Visualization and reconstruction of three-dimensional fossils from the Silurian Herefordshire lagerstätte", "Palaeontologia Electronica", 4.1 (2001)] (pdf file)
*Briggs, Derek E G, David J. Siveter, and Derek J. Siveter, 1996. "Soft-bodied fossils from a Silurian volcaniclastic deposit," "Nature", 382 pp248-250.
* [http://www.findarticles.com/p/articles/mi_qa3721/is_200001/ai_n8897561/pg_2 Orr, Patrick J, Briggs, Derek E G, Siveter, David J, Siveter, Derek J., "Three-dimensional preservation of a non-biomineralized arthropod in concretions in Silurian volcaniclastic rocks from Herefordshire, England", "Journal of the Geological Society", January 2000] (pdf file)