Steve Dutch, a geologist and avocational skeptic, has gone from criticism of the Great Lakes as impacts craters (not a central claim of the YDB team, in any case) to taking on Rick Firestone and others in Isotopic Chemistry.
The interdisciplinary nature of this debate is fun and healthy, but if were Dutch, I would stick with midwestern geology, and leave the isotopic chemistry to Firestone — Rick is pretty competent in that area.
On 4/13/2010 10:38 AM, Dutch, Steve wrote:“I don’t think that all evidence for isotopic dating of impacts is affected enough by neutrons released in the hypervelocity impacts themselves. The problem is, we don’t know. Why don’t we know? Lack of money.”Money isn’t the issue. It’s the missing isotopes.Everyone who wants to ignore radiometric dating (creationists, Velikovskians, etc.) postulates magical particle fluxes capable of rearranging isotope ratios. The problem is that any imaginable particle flux would create a host of other isotopes that are just not there. For example, the principal natural isotope of calcium is Ca-40. The next isotope, Ca-41, has a half life of 100,000 years. Any recent neutron flux should have produced a lot of Ca-41. The two principal isotopes of nickel are Ni-58 (70%) and Ni-60 (27%). In between is Ni-59 with a half life of 76,000 years. Any recent neutron flux should have created a lot of Ni-59 – your pocket change should be radioactive. And where’s all the technetium? It has no stable isotopes but several with half lives of a few million years and is easy to manufacture. Surely any intense natural particle bombardment ought to create a lot of Tc.So, yes, we do know. It doesn’t happen.Click below for Firestone’s response
Steve, get your facts straight.The isotope evidence is there. Radiocarbon in the environment doubled 45,000 years ago and remained higher until now. The cause is well known and due to increased cosmic ray flux in the past. Radiocarbon dating doesn’t work without the corrections measured by Hughen et al in tree rings, corals and ocean sediments. Similar past increases are well established for 10Be and 36Cl. 60Fe has been found in ocean sediments.Many other cosmogenic isotopes are noted in the literature. The cosmic ray rate is not constant and cosmic rays produce neutrons. In the case of 14C the carbon is preserved in the carbon cycle and can easily be seen. For the other elements sudden increases due to nearby supernovae stay put in the strata where they were produced so they are harder to identify. Neutrons produced in the atmosphere are generally absorbed by the 14N(n,p) reaction before reaching the ground. If you fly a CCD detector to a telescope it will be radioactive when it arrives.For extraterrestrial objects it is well known that some isotopes have anomalous abundances. Most notable are 187Os, whose abundance can vary by an order of magnitude, and 40K whose abundance can vary by a factor of 2000. 234U and 36S abundances also varies by an order of magnitude terrestrially. Lunar data have shown that significant increases in 26Al, 59Ni, and 14C occurred >20,000 years ago.At the time of the YD impact there has was a sudden significant increase in global radiocarbon. This is well established and too rapid to be due to changes in Earth’s magnetic field. We find many carbon spherules containing nanodiamonds in the well dated impact layer that were dated at UC Irvine hundreds of years into the future. There are only two plausible scenarios for this. 1) Neutrons produced by nuclear fusion in the comet as it entered the atmosphere or 2) 14C carried in by the comet which originated as shrapnel from a recent nearby supernova. The first hypothesis has been suggested by astrophysicists but I don’t think it works. The second hypothesis is consistent with a supernova that I discovered which exploded 100 pc from Earth 44,000 years ago. Its arrival is consistent with the velocities observed in shrapnel from the Crab SNR. Radiocarbon is produced at 10**7 times terrestrial abundance by nucleosynthesis in type II SN.Regards,Rick Firestone