The geological and geoarchaeological significance of Cerro Pedernal, Rio Arriba County, New Mexico
Gary A. Smith and Bruce B. Huckell
Cerro Pedernal is an isolated basalt-capped peak of substantial geologic and geoarchaeological significance. The peak is located on the Colorado Plateau near the boundary of the Rio Grande rift. Oligocene-Miocene stratigraphic units on Cerro Pedernal correlate to thicker sections within the rift and document initiation of rift-basin subsidence before 25 Ma. Cessation or near cessation of sedimentation on the nascent rift margin led to hypothesized extensive weathering and formation of pedogenic calcrete horizons that were later buried by volcaniclastic deposits that overlapped the rift margin. Diagenesis of vitric volcaniclastic detritus likely led to silica replacement of the calcareous soils to form the Pedernal chert, which was commonly used for lithic-tool manufacture for more than 13 millennia of human occupation in northern New Mexico. Heavily utilized chert quarries in the Cerro Pedernal-San Pedro Parks region were important lithic-material sources, but so were redeposited cobbles of chert that are ubiquitous in alluvial deposits on the Colorado Plateau and in the Rio Grande rift. The combination of primary and secondary chert sources has confounded efforts to determine the exact source locations of artifact raw materials. Fire, along with simple prying tools and hammerstones were likely used to dislodge large chert pieces for tool manufacture. Preliminary working of cores and bifaces produced large volumes of irregular flakes and rejected pieces that were mistaken by some early workers as finished products of more ancient tool-making cultures.
- Smith, Gary A.; Huckell, Bruce B., 2005, The geological and geoarchaeological significance of Cerro Pedernal, Rio Arriba County, New Mexico, in: Geology of the Chama Basin, Lucas, Spencer G.; Zeigler, Kate E.; Lueth, Virgil W.; Owen, Donald E., New Mexico Geological Society, Guidebook, 56th Field Conference, pp. 425-431.