Sand Stromatolites from Blackberry Hill

Coming from the Krukowski Quarry, Mount Simon Wonewoc Sandstone, these unique fossil stromatolites were are remains of a microbial biofilm on a tidal beach during the Cambrian in what is now Central Wisconsin. This quarry has been producing some intriguing trace or ichnofossils, including huge Scyphozoan madusae (jellyfish), tentacled jellyfish, Diplichnites, Protichnites, and the so-called sand stromatolite you see here, among others.

Sand stromatolite is conjectured to be a nucleation nodule of a small colony of cyanobacteria. Depending on environment conditions, this colony could grow large in the familiar large domes, or would otherwise perish.

Sand stromatolites are uncommon in the Krukowski quarry, and no large stromatolitic structures are found in the vicinity of the formation. Perhaps these small bacterial colonies served as a food source for the early animals that lured them ashore on this Cambrian beach, leaving their footprints in the sand, in fact, the first footprints on land. Scientists studying these ancient intertidal sand flads hypothesize that the microbial mats mediated the preservation of the Blackberry Hill ichnofossils and body fossils. That is, they prevented tidal erosion of the fossils.

Also see: Cambrian Shadows

References:
- York, A., Hagadorn, J. W., and Bernstein, J. (2005) Upper Cambrian sand stromatolites of central Wisconsin: Geological Society of America Abstracts.
- Getty, P, Producing and Preserving Climactichnites, Proceedings of the Annual Meeting of the Geological Societ of America, Paper 197-6, 2006
- Seilacher, A. (2008). "Biomats, biofilms, and bioglue as preservational agents for arthropod trackways". Palaeogeography, Palaeoclimatology, Palaeoecology 270 (3–4): 252–257.