========================================================================= Date: Sat, 1 Jul 1995 13:57:08 -0400 Reply-To: Radiocarbon Mailing List Sender: Radiocarbon Mailing List From: "Donald M. Thieme" Subject: Re: Forwarded message In-Reply-To: Message of Fri, 30 Jun 1995 10:13:57 -0700 from There are numerous discussions of this issue in the literature by archaeologists. One example I know of is F. E. Smiley on chronometry of Basketmaker II sites on the Colorado Plateau. However, I think archaeologists often make the mistake of treating this as a purely statistical issue. The standard deviations reported by radiocarbon labs reflect laboratory accuracy but not the variable "spread" that results from long-term changes in the rate of 14C production in the upper atmosphere. In other words, what has not been worked out is how to "cluster" dates with different standard deviations and calibrate both the dates and the standard deviations uniformly. This probably requires understanding spatial as well as temporal variability in production of 14C and careful attention to the delta-13C of the material dated. A methodological proposal along these lines would be useful not only to to archaeologists but to other Quaternary scientists as well. ========================================================================= Date: Mon, 3 Jul 1995 16:03:01 -0400 Reply-To: Radiocarbon Mailing List Sender: Radiocarbon Mailing List From: "Michael D. Campbell" Subject: Re: Forwarded message Ladies/Gentlemen: I have pieces of very old "wood" or charcoal that came from the contact of bedrock and landslide material. Based on their position, if we knew the age of this carbon material, we could estimate when the slide or quake occurred. The only variable on setting the date would then be laboratory variations. Is this true? By the way, the contact marked the upper boundary of a major gold-bearing zone in an open pit mine in central Nevada. Would someone be interested in age-dating these samples? They have been wrapped in alluminum foil since 1984. I'll provide the necessary geologic information. Could make an interesting short paper. Regards to all, MDC ========================================================================= Date: Wed, 5 Jul 1995 12:13:25 +0900 Reply-To: Radiocarbon Mailing List Sender: Radiocarbon Mailing List From: Kimura K Subject: Source of Conatmination Dear, Forum members I have a question about possible source of carbon contamination of soil. I'm not a 14C scientist but just a "user" of 14C dates. Once I asked dating of some buried peaty soil samples to an lab. and got 14C dates of 3400 and 2800 yBP (methanol LSC). The soil was developed on a tephra (pyroclastic flow deposit errupted 6300yBP; this is studied very well) and buried 50-100cm depth. Only granite rock or weatherd granite was found below the tephra. So, there is no organic material below the buried soil. When I got the 14C dates, I thought they were newer because of contamination of tree roots. But, many paleobotainsts around me said that it might be newer but it could be older by carbon source from volcanic material or bed rock. But still I think carbon from non-organic material is negligible and the source of contamination that I need to aware is root. Am I right? Regards _ KIMURA Katsuhiko ( ) ^ Global Environment Research Division ( ) / \ National Institute for Environmental Studies //|\\ Onogawa 16-2, Tsukuba 305, Japan | ///|\\\ TEL 81-298-50-2426 ^ | _ | FAX 81-298-51-4732 /|\| ( ) | _________________|_|__|____|______ ========================================================================= Date: Wed, 5 Jul 1995 17:44:04 +0200 Reply-To: Radiocarbon Mailing List Sender: Radiocarbon Mailing List From: Peter Becker-Heidmann Subject: Re: Source of Conatmination In-Reply-To: <9507050306.AA17716@sun61a.nies.go.jp> from "Kimura K" at Jul 5, 95 12:13:25 pm Dear colleague, besides roots, which are probably the main contaminants in that depth if you have forest vegetation, also dissolved organic matter percolating through the soil can have an impact. Due to the nature of the exponential decay curve, a small amount of contemporary material alters the radiocarbon age more than the same amount of 14C free material would do. This could have taken place during the soil development already and need not to be linked to contamination after being buried. Therefore, 2800 y is the maximum time from the burial of the soil up to now, if there was no contamination after the burial. In case of subsequent contamination the soil had been buried even earlier. Kind regards P. Becker-Heidmann > > Dear, Forum members > > I have a question about possible source of carbon contamination of soil. > I'm not a 14C scientist but just a "user" of 14C dates. > > Once I asked dating of some buried peaty soil samples to an lab. and got > 14C dates of 3400 and 2800 yBP (methanol LSC). The soil was developed on a > tephra (pyroclastic flow deposit errupted 6300yBP; this is studied very > well) and buried 50-100cm depth. Only granite rock or weatherd granite was > found below the tephra. So, there is no organic material below the buried > soil. > > When I got the 14C dates, I thought they were newer because of > contamination of tree roots. But, many paleobotainsts around me said that > it might be newer but it could be older by carbon source from volcanic > material or bed rock. > > But still I think carbon from non-organic material is negligible and the > source of contamination that I need to aware is root. Am I right? > > Regards > > _ > KIMURA Katsuhiko ( ) ^ > Global Environment Research Division ( ) / \ > National Institute for Environmental Studies //|\\ > Onogawa 16-2, Tsukuba 305, Japan | ///|\\\ > TEL 81-298-50-2426 ^ | _ | > FAX 81-298-51-4732 /|\| ( ) | > _________________|_|__|____|______ > --------------------------------------------------------------------- Peter Becker-Heidmann : : /YY\ : : Institute of Soil Science : |YYYY|. : Allende-Platz 2, D-20146 Hamburg, GERMANY : . \YY/. : : Phone: +49 40 4123 2003, Fax: +49 40 4123 2024 __:__:_||__:__:__ E-Mail: PBeckerH@Uni-Hamburg.de SOILSOILSOILSOILS --------------------------------------------------------------------- ========================================================================= Date: Thu, 6 Jul 1995 12:39:43 -0400 Reply-To: Radiocarbon Mailing List Sender: Radiocarbon Mailing List From: "Donald M. Thieme" Subject: Re: Source of Conatmination In-Reply-To: Message of Wed, 5 Jul 1995 12:13:25 +0900 from You are probably right in this case. However, it is definitely possible to have "old" carbon contamination from carbonates. Most labs treat the samples with acids to take care of this. If you were dealing with very calcic volcanic rocks and if soil carbonates (calcic horizons) formed in your profiles you should at least explain how the samples were treated in publishing the results. in these profiles? ========================================================================= Date: Fri, 7 Jul 1995 16:35:26 +1200 Reply-To: Radiocarbon Mailing List Sender: Radiocarbon Mailing List From: "Sparks, Rodger" Subject: Source of Conatmination - Reply I tossed this question to Nicola Redvers-Newton, who looks after our sample processing, and she replied as follows: " The contamination in the soil could come from 3 main sources; roots, mobile organic compounds, or carbonates, the last 2 being carried by ground water into the buried soil. The roots would contain younger carbon, of course, but the mobile organic compounds (humic compounds) and the carbonate could be any age. At the Rafter Radiocarbon Laboratory humic acids removed from a variety of buried materials from different sites have been found to range in age from very ancient to bomb carbon. Also, younger carbonate has been found from ancient tooth apetite of 28000 BP. I agree with Donald Thieme that the pretreatment method has to be known before any strong conclusions can be drawn. If the standard acid-alkali-acid pretreatment has not been applied then the presence of contaminating carbonates (removed by acid) and mobile organic compounds (removed by alkali) cannot be ruled out. However, I would like to know more about the soil microbes. Could bacteria or fungi introduce young carbon while living off the old carbon of an ancient soil? Any biologists listening? " ========================================================================= Date: Mon, 10 Jul 1995 18:37:00 SAT Reply-To: Radiocarbon Mailing List Sender: Radiocarbon Mailing List From: Museo de Arte Precolombino Subject: some help I=B4m preparing a note about RC Dating method in one public educational=20 magazine that we have here in the museum (El Precolombino). I have all the= =20 scientific information that I need, but I need one anecdotical information= =20 about the first RC 14 analysis ever made, something like the site wish come= =20 from and the date . Thanks in Advance Luis E. Cornejo B. Museo Chileno de Arte Precolombino lcbmchap@reuna.cl=20 ========================================================================= Date: Tue, 11 Jul 1995 11:13:08 +1200 Reply-To: Radiocarbon Mailing List Sender: Radiocarbon Mailing List From: "Sparks, Rodger" Subject: some help - Reply Willard Libby's book "Radiocarbon Dating" (University of Chicago Press, 1955) lists sample No. C-1 as: "Zoser: Acacia wood beam in excellent state of preservation from tomb of Zoser at Sakkara. Known age 4650 +/- 75 years according to John Wilson..." The mean radiocarbon age obtained by Libby was 3979 +/- 350 I don't know if this was literally the first sample, but it heads the list. Rodger Sparks Rafter Radiocarbon Laboratory R.SPARKS@GNS.CRI.NZ ========================================================================= Date: Thu, 13 Jul 1995 19:37:01 +0200 Reply-To: Radiocarbon Mailing List Sender: Radiocarbon Mailing List From: Peter Becker-Heidmann Subject: Re: some help In-Reply-To: from "Museo de Arte Precolombino" at Jul 10, 95 06:37:00 pm > > I=B4m preparing a note about RC Dating method in one public educational=20 > magazine that we have here in the museum (El Precolombino). I have all the= > =20 > scientific information that I need, but I need one anecdotical information= > =20 > about the first RC 14 analysis ever made, something like the site wish come= > =20 > from and the date . > > Thanks in Advance > > > Luis E. Cornejo B. > Museo Chileno de Arte Precolombino > lcbmchap@reuna.cl=20 > The first radiocarbon age determinations were carried out by Libby, Anderson and Arnold on two Egyptian wood samples of known age (ca. 4600 years before present), one from the tomb of Sneferu at Meydum, the other from the tomb of Zoser at Sakkara. The results were published 1949 in Science, Vol. 109, No. 2827, pp. 227-228. They used a half-life value of 5720+-47 years and hit the real date within an error of 5-10% without enrichment. In the same year, Arnold and Libby published the more classical paper "Age Determinations by Radiocarbon Content: Checks with Samples of Known Age" in Science, Vol. 110, No.2869, pp. 678-680. Hope this helps Peter --------------------------------------------------------------------- Peter Becker-Heidmann : : /YY\ : : Institut fuer Bodenkunde : |YYYY|. : Allende-Platz 2, D-20146 Hamburg, GERMANY : . \YY/. : : Phone: +49 40 4123 2003, Fax: +49 40 4123 2024 __:__:_||__:__:__ E-Mail: PBeckerH@Uni-Hamburg.de SOILSOILSOILSOILS --------------------------------------------------------------------- ========================================================================= Date: Wed, 26 Jul 1995 14:15:10 +0100 Reply-To: Radiocarbon Mailing List Sender: Radiocarbon Mailing List From: Carbon14 Group Subject: OxCal v2.17 Re: OxCal Windows calibration and statistical analysis program. OxCal v2.17 is now available. The main changes since v2.15 are the fixing of a bug in the Windows interface which made the program crash on some computers. If you still have similar problems with the program please let me know the details. You can get the program itself and information relating to the changes from previous versions over the Internet by accessing the WWW page: http://www.ox.ac.uk/depts/rlaha/ Or by sending a (stamped) addressed envelope with a blank IBM formatted 3.5" disk. Christopher Ramsey Research Lab for Archaeology 6 Keble Rd. Oxford OX1 3QJ Previous Item Next Item