Dr. Robert W. Simpson, currently with the U. S. Geological Survey, discoverer of these bones, holds a meter stick. The burial is approximately 40 cm to the left and about 40 cm below the tip of the meter stick. This photograph was taken in 1975.
At first, only the broken tip of a long bone was exposed. I recognized these remains as human after removing sediment and exposing a human mandible.
Dipping beds of poorly sorted sand and gravel are visible behind Bob's left elbow. To reach the bones, I had to stand on the gasoline can set on top of sediment accumulated at the base of the vertical exposure. These rocks were exposed when the operator of the 101 Ranch quarried sand and gravel from the side of this hill to build a road across the San Benito River.Side view of emerging mandible.
Front view of emerging mandible. Close-up of "dig". The mandible has lost some front teeth. These were collected. Still closer. Time to quit fooling around and call in a professional before we ruin something else. Archaeology students from Stanford University arrive at the "dig". Master's degree candidate Lacy Atkinson (red and white striped shirt, mostly concealed by other students) supervised. The "dig" is located above step ladder, and the San Andreas fault is at the extreme right of this photo. Light-colored rocks are an arkosic conglomerate, shattered and sheared but not noticeably weathered. Clasts are mostly granitic (quartz monzonite, perhaps some diorites, I was not making observations carefully enough to pass a quiz on acidic intrusives), similar to rocks of the Gabilan Range. Archaeologists continue discussing strategy. Excavation begins.Usually archaeologists dig from the top down. Here, they excavate horizontal trenches.
Nails and strings subdivide the dig into "units". However, no grave good were found, and the sediments and soil above the bones show no signs of disturbance.
Shadows now point east. Work progresses.
This block was removed and returned to the laboratory, where Lacy Atkinson removed and identified each bone or bone fragment.
Panoramic photo of dig (white T-shirt in shadows, right center), San Andreas fault (concrete creepmeter box in foreground is on the Pacific plate), and road across the San Benito River (culvert visible, below right center of photograph). The vertical contact between conglomerate and fault gouge is visible about 4 meters to the right of the car. Layering of sand and pebbles downdip from the burial. Ruler is 6 inches long.Dr. John Weeks points at fracture in mold formerly occupied by a large conglomerate clast. John was last seen torturing rocks under laboratory conditions. This photograph was taken in 1977. No additional bones, human or otherwise, or ancient cultural materials were discovered at this location during later visits.
Close-up of John's hand (for scale) pointing out fracture
. Note how clasts in upper left and lower right of photo are shattered. Some clasts broke into slabs like so many slices of bread. Slab surfaces showed no evidence of shearing.Experimental petrophysicist stands in line with the conglomerate-gouge contact.
Vertical slickensides on clay show relative movement of underlying wedge of conglomerate. Dip-slip faulting? Did a prehistoric event similar in mechanism to the Loma Prieta earthquake elevate and shatter this wedge? Highly shattered fault separating blocks of not-quite-so-shattered conglomerate. Block to the left appears to have moved up with respect to block on the right, placing overlying clay in fault contact with conglomerate. Large clast in center is broken but the pieces show no relative offset.Faults separate the conglomerate into 4 blocks
. Shattering of otherwise solid crystalline rock suggests conditions different from the creep that broke the concrete floor of the Almaden winery building or drainage ditches a few kilometers to the northwest.Eric Floyd examines another river terrace, this one located high above and a few hundred meters northwest of the "dig". This deposit, also used for building ranch roads, contains large (boulder size - up to 80 cm long) rounded cobbles typical of Franciscan rocks as well as rounded rocks of granitic composition. Most granitic cobbles, although nicely rounded, found in this deposit are so thoroughly weathered that they shatter into a pile of plagioclase and quartz crystals when struck with a hammer. This photograph was taken in 1984. Nothing was found in this terrace that could be used to provide an absolute age.
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