C14 has a half-life just short of 6,000 years and becomes useless prior to 62,000 years. Dates beyond 40,000 can be screwy. U series is your best bet but I don't know the recovery/handling techniqes.
Yeah, I'm not real sure either, Pat.
Your right though: as you get into the 40,000-50,000 B.P. range with 14C dating, the maximum end becomes very uncertain.
But if the C14 date comes out at 12,000-14,000 years it would still be useful to know.
If the dates do start to get "screwy" there are, as you say, other ways of measuring them.
In either case, Charlie is going to get a lot of flack from the Club. May as well try a pre-emptive strike on their obvious comebacks.
Good point, Min. The more different techniques that are used, and that agree, the harder time anyone's gonna have disputing the overall package. For example, Al Goodyear's 14C 50,000 B.P. minimum dates could be paired up with Uranium series dating, to strenghthen the credibility of both (assuming the results of the U series dating comes out to more than 50,000 B.P.).
The bottom line is $$. So far, funding has been provided for the U/Th dating, here locally.
Here's a write-up on Warren Sharp, who is currently analyzing 6 specimens sent to him from this local site:
Warren D. Sharp
Geochronologist
Ph.D. Geology, 1984
University of California at Berkeley
U-series Dating, Quaternary Geochronology, Paleoclimate, Geomorphology,
Paleoanthropology,
Archaeology(
)
Warren D. Sharp was born in 1952 in Berkeley, California. Sharp received both his B.A. (1974), and his Ph.D. (1984) in Geology from the University of California at Berkeley. His doctoral research involved development and application of K-Ar and U-Pb geochronometry to the formation of continental crust via plate tectonics processes. He accepted a faculty position in the Department of Earth and Space Sciences, State University of New York at Stony Brook, where he taught and established a research program centered on 40Ar/39Ar geochronometry applied to problems in continental crustal evolution. Since coming to the Berkeley Geochronology Center (then Institute of Human Origins) in 1992, his research has focused on providing a time-axis for significant geologic processes and events over the last ~million years, including active volcanism, glaciation, paleoclimatic change and active faulting. In particular, he has developed innovative applications of uranium-series dating to silica and carbonate soil components to provide ages for geologically youthful surfaces and strata in order to elucidate human physical and cultural evolution, relations between regional and global climate change, and rates of crustal deformation. He serves on the editorial board of Quaternary Geochronology, as co-leader of the International Quaternary Association’s Drylands Dating Sub-Commission, and as Associate Director of the BGC.
http://www.bgc.org/people/each_person/sharp_w.html
As attested to by their involvement in the Valsequillo dating, BGC is not afraid to get involved in controversial sites. I love geologists!!
Paul Renne, responsible for the Ar/ Ar dating at Valsequillo:
Paul R. Renne was born in 1957 in San Antonio, Texas. He received his A.B. with Highest Honors in Geology from the University of California, Berkeley in 1982. He received his Ph.D. in Geology from the University of California at Berkeley in 1987. After a postdoctoral fellowship at Princeton University, he returned to Berkeley in 1990 as a Research Associate at the Institute of Human Origins and became Director of Geochronology in 1991. He was the founding Director of the Berkeley Geochronology Center in 1994, and has served in that role (and as Board President) since then with a hiatus from 2000 to 2003. In 1995 Renne was appointed Adjunct Professor in the Earth and Planetary Science Department at U.C. Berkeley, where he teaches courses in petrology, geochronology and field geology, and serves as formal research advisor to graduate students and postdocs. Renne specializes in 40Ar/39Ar geochronology and paleomagnetism applied to broad topics in the evolution of Earth’s biosphere and lithosphere, and to the relationships between these and extraterrestrial processes such as meteoroid impacts in the inner solar system. He is also heavily engaged in refinement of methodologies for these techniques.
Renne’s contributions to his field were recognized by the American Geophysical Union in 2005 with the Bowen Award "…for innovations in high-precision Ar-Ar dating and for application of these techniques to refining the geologic and paleomagnetic timescales, to paleoanthropology, and, most notably, to ages and durations of LIP volcanism and their relationship to mass extinctions and global environmental crises". Renne serves as a Corresponding Editor for Eos, and as Editor for Quaternary Geochronology.
http://www.bgc.org/people/each_person/renne_r.html
Paul reported a 1.1 million B.P. date for the Hueyatlaco Ash, overlying the artifacts recovered. Mike Waters and Paul went back down to Hueyatlaco in November, for further analyses. The whole group of researchers there in 2004 is scheduled to regroup there this year. I need to find out the exact dates.
I'm gonna post this portion of this thread on the Hueyatlaco dating thread, just to keep it current.
