Fossil wood in the upper Santa Fe Group, south-central New Mexico: implications for mineralization style and paragenesis
— Jochems, Andrew P. Hobbs, Kevin M. and George E. Mustoe

Fossilized wood is known from New Mexico strata spanning the Pennsylvanian through Quaternary, but few systematic studies have been conducted to document petrifaction style, timing/sequence, and mineral assemblages. Plio-Pleistocene deposits of the upper Santa Fe Group in south-central New Mexico contain fossil angiosperm wood that has undergone silicification or calcification, the two most common modes of wood petrifaction. Fossil wood occurs in axial-fluvial sediments deposited by the ancestral Rio Grande between ~3.6 and 0.8 Ma. X-ray diffraction (XRD) patterns and petrographic analyses were used to assess calcified and silicified specimens from the Camp Rice Formation (upper Pliocene) in the Hatch-Rincon Basin, and silicified specimens from the Palomas Formation (lower Pleistocene) in the San Marcial Basin. Opalized wood from the Camp Rice Formation is mineralized with both disordered cristobalite and tridymite (opal- CT) and chalcedony, whereas Palomas Formation samples are dominated by crystalline quartz. Preserved anatomical structures agree with longstanding models of initial silicification on wood cell walls, but the age of the deposits in which the specimens were found and co-occurrence of opal-CT and chalcedony challenge paradigms regarding fossil wood age and genetic sequence. Future research should address silica sources in the Camp Rice and Palomas formations and seek to constrain the timing of mineralization.