Evidence of Equifinality in Tafoni Genesis

Backscattered electron microscopy, in tandem with energy dispersive X-ray analysis, reveals evidence that multiple processes work in tandem to generate tafoni development in Oman, Papago Park and Picketpost Mountain, AZ. Carbonate precipitation into Papago Park sedimentary breccia wedges apart the host rock, and then dissolves to leave behind uncemented fragments. Oman tafoni also show evidence of carbonate precipitation as a wedging agent, in addition to dissolution of the host carbonate rock and a possible role for organics that occupy some pore spaces. Tafoni in Picketpost Mountain welded tuff displays evidence of multiple processes including: dissolution of glassy groundmass; biotite splitting surrounding minerals; reprecipitation of a variant of silica glaze; and erosion of the tuff after the rock weakens sufficiently. All three sites have in common the synergism of chemical and physical processes operating at the micron scale, where dissolution opens space for physical wedging to operate by carbonate precipitation and biotite splitting. The execution of multiple processes to generate a common form supports the idea of equifinality in tafoni formation.