Mr. Atkinson concluded that the bones were those of a Native American (based on the teeth) female (based on the shape of the pelvis) between the ages of 14 and 16 years of age (based on the teeth again). Because of severe disarticulation (the pelvis, mandible, parts of the skull, humerus and several ribs were all found in the small block excavated and returned to the laboratory) of the bones and because no grave goods were found or evidence of backfilling observed, we concluded that these bones were washed into this stream terrace during a flood.

I do not think the bones were carefully examined for signs of predation.  Did a California "Golden Bear" bury the remains of this individual, intending to return for a later meal?  "Ve ist too soon too old und too late too smart."

These bones no longer exist; the collagen was separated and used for C-14 analysis in the radiocarbon laboratory at The University of California (Riverside), which required the entire bone mass. The C-14 age was consistent with the amino acid racemization age - about 5000 years old.

Deformation of this recent terrace and uplift of other terrace deposits in the immediate area suggest either very rapid erosion or recent tectonic uplift. Old terraces of the San Benito River southwest of the San Andreas fault are easily identified because they contain clasts of Franciscan rocks from the North American of the San Andreas fault in addition to granitic rocks of the Gabilan Range. Stone Canyon, a valley deeply eroded into the granitic rocks of the Gabilan Range, has the appearance of a "hanging valley" where it meets the erosional scarp of the San Benito River and the San Andreas fault. This observation was first pointed out to me by Dr. John H. Healy, USGS (ret.), although I can not certify that he did not hear it from another source.

Ten to twenty meters of alluvium now cover the floor of the canyon to a distance of at least 3 kilometers into the Gabilan Range. In other words, the floor of Stone Canyon is now a depositional environment. Has this tectonic block tilted, uplifting the eastern edge?

Many clasts of the arkosic conglomerate exposed in this quarry are shattered but not sheared. Most fractures resemble tension fractures. Shear zones in which rocks are reduced to powder cut the conglomerate, but many rocks between these shear zones have been broken into disks. Dip-slip slickensides on clay gouge faulted against the conglomerate document vertical displacement. I do not know if slow deformation (creep) can generate such nice clean slicks - I get the feel that these represent a single violent episode of uplift, a thrust earthquake, an early sibling of the 1989 Loma Prieta event.

Could these clasts have been shattered by coseismic strains during a massive thrust earthquake? How much tensile strain can a rock withstand without failure, and how does this compared with P-wave dilation in rocks immediately adjacent to a propagating fault?

I do not know if this quarry "outcrop" still exists - floods have no doubt washed out the causeway, requiring additional excavation and construction. The property was posted and permission to enter denied the last time I was in the area, and I now spend most of my time far to the east. The thrust component of the Loma Prieta earthquake triggered some rethinking of what was observed in and around the entrance to Stone Canyon. Perhaps finding, mapping and dating (THAT will require considerable luck as well as effort) some old river terraces in this area will provide clues to just how preposterous this speculation really is.

Comments?  Share them with Dr. Don Stierman - Geology Department - The University of Toledo <Ohio>

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