One of John's missions on this trip was to document the Tiger chert (silicified oil shale) localities as part of his research into several bifaces that have been recovered in the Southwest, dating to the 14th-15th Centuries AD, associated with Pueblo sites (see his co-authored article in Kiva, Vol. 53, No. 4 [Summer, 1988], pp. 321-334). When weathered, some of the oil chert takes on distinct banding, making it readily distinguishable. He collected samples for chemical analysis to determine if the bifaces could have come from the sources we visited. It is unlikely that the individual locations will have distinctive chemical signatures but the information may be used to eliminate other similar sources. If the general source can be isolated to this area, it would indicate that Pueblo IV people may have had contact, directly or indirectly, with Shoshonian groups as part of a wide interaction network.
John documenting a source of Tiger chert
Tiger chert samples with co-ordinates deleted
Since the oil chert can occur as very large nodules, this was also an opportunity for Bruce to demonstrate and practice a technique of production of large flake blanks. While probably not particularly relevant to John's research, it is relevant to understanding how Homo erectus may have produced large flake blanks for handaxes and cleavers hundreds of thousands of years ago in Eurasia and Africa (some of Bruce's research in India). Critical to this technology is not only large solid pieces of flaking stone but also hammerstones that can withstand the extreme energy of large flake production.
Acheulain flake cleavers
Large oil chert nodule
Striking large flake blanks
Flake blanks suitable for Acheulian tools
For this method to be performed efficiently, the hammerstones must be matched to the desired product. Ideally, they should have enough weight so that little muscle force is needed to initiate fracture; let the stone do the work. It is also important that the core be supported on the ground so that the weight provides potential energy. This is best accomplished by holding the core up on a pivot point. I find it amazing that our ancient cousins, Homo erectus, evidently had the intelligence and skill to develop and use this technique, especially with some of the hard stones they flaked such as quartzite and basalt.