========================================================================= Date: Fri, 1 Dec 2000 06:35:24 +0000 Reply-To: Doug Weller Sender: Radiocarbon Mailing List From: Doug Weller Subject: Query about 'young CO2' and recrystalllization Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit I've been following a debate about dating mortar, and there appears to be some disagreement about the effect of recrystallization. I thought that this could make mortar appear younger by introducing 'younger' CO2, but now I've read: "Since about 1890, the use fossil fuels has released large amounts of CO2 into the atmosphere. Because fossils fuels consist of very old coal, oil, and gas with virtually nonexistent Carbon-14 content, the burning of them has diluted the atmosphere with non-radioactive carbon and lowered the natural radiocarbon content by two percent. For example, living wood will have an apparent age of 1,000 to 1,500 years B.P. Thus, as mortar recrystallizes and absorbs industrial revolution age air, it will become "older" in age, not younger. In an industrial New England, with acid rain and plenty of "dead" carbon being pumped into the atmosphere from the burning of fossil fuels, it seems like dissolution and reprecipitation and recrystallization of the calcium carbonate could introduce modern carbon into the mortar and make it older." Any comments would be appreciated. Thank you. -- Doug Weller Moderator, sci.archaeology.moderated Submissions to:sci-archaeology-moderated@medieval.org Doug's Archaeology Site: http://www.ramtops.demon.co.uk Co-owner UK-Schools mailing list: email me for details =========================================================================== To unsubscribe from this list, send the command SIGNOFF C14-L to LISTSERV@LISTSERV.ARIZONA.EDU, or send a request to C14-L-request@LISTSERV.ARIZONA.EDU. ========================================================================= Date: Sat, 2 Dec 2000 15:58:00 +0900 Reply-To: Radiocarbon Mailing List Sender: Radiocarbon Mailing List From: Mark Hall Subject: freshwater mollusc shell dates MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit While its clear I am probably not looking at the right issues of RADIOCARBON, but would anyone have a suggestion on which curve (marine or terristrial) one should use when calibrating C14 dates from freshwater mollusc species that are typically resident in shallow waters (less than 10 m)? Thanks in advance, Mark Hall markhall@gol.com =========================================================================== To unsubscribe from this list, send the command SIGNOFF C14-L to LISTSERV@LISTSERV.ARIZONA.EDU, or send a request to C14-L-request@LISTSERV.ARIZONA.EDU. ========================================================================= Date: Mon, 4 Dec 2000 13:56:29 +0100 Reply-To: Radiocarbon Mailing List Sender: Radiocarbon Mailing List From: Florian Boehm Subject: Re: Query about 'young CO2' and recrystalllization Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 8bit At 06:35 01.12.00 +0000, Doug Weller wrote: >"Since about 1890, the use fossil fuels has released large >amounts of CO2 into the atmosphere. Because fossils fuels >consist of very old coal, oil, and gas with virtually >nonexistent Carbon-14 content, the burning of them has >diluted the atmosphere with non-radioactive carbon and >lowered the natural radiocarbon content by two percent. >For example, living wood will have an apparent age of >1,000 to 1,500 years B.P. > >Thus, as mortar recrystallizes and absorbs industrial >revolution age air, it will become "older" in age, >not younger. In an industrial New England, with acid >rain and plenty of "dead" carbon being pumped into the >atmosphere from the burning of fossil fuels, it seems >like dissolution and reprecipitation and >recrystallization of the calcium carbonate could >introduce modern carbon into the mortar and make it >older." These numbers are not correct. It is true that the radiocarbon content of the atmosphere decreased from 1900 A.D. until 1950 A.D. due to the input of old carbon from fossil fuel burning. However, the effect of this decrease on radiocarbon dates is not to let them appear 1000 years older but only about 200 years. That's the common problem with radiocarbon dating that the initial atmospheric radiocarbon content is not constant. There was a similar shift, for instance, from 1700 A.D. until 1800 A.D., probably a consequence of the increase in solar activity after the Maunder sunspot minimum. What's much more important for your dating problems, is the huge increase (about 100%) in atmospheric radiocarbon starting in the 1950s due to the nuclear bomb testing. It continued until the early 1960s, when bomb testing sites were moved underground and radiocarbon levels slowly started to decrease again. The levels today are still a little above the 1950 value, despite the continuing input of "old" fossil fuel carbon to the atmosphere. If you have only a slight contamination of carbon from the 1960s-1980s this lets your dated sample appear much younger than it really is. Regards, Florian Boehm ******************************************** Florian Boehm GEOMAR Forschungszentrum für Marine Geowissenschaften Wischhofstr. 1-3, Gebäude 4, D-24148 Kiel email: fboehm@geomar.de http://www.geomar.de/~fboehm/ Tel.: (49)431-600-2842 Fax: (49)431-600-2941 ******************************************** =========================================================================== To unsubscribe from this list, send the command SIGNOFF C14-L to LISTSERV@LISTSERV.ARIZONA.EDU, or send a request to C14-L-request@LISTSERV.ARIZONA.EDU. ========================================================================= Date: Tue, 5 Dec 2000 09:36:10 -0600 Reply-To: Radiocarbon Mailing List Sender: Radiocarbon Mailing List From: Rick Forester Subject: Re: freshwater mollusc shell dates MIME-Version: 1.0 Content-type: text/plain; charset=us-ascii You might find the paper by Brennan, R. and Quade, Jay, 1997. Reliable Late-Pleistocene Stratigraphic Ages and Shorter Groundwater Travel Times from 14C Fossil Snails from the Southern Great Basin, Quaternary Research v. 47, pages 329-336 useful. Rick Forester MS 980 ESP USGS DFC Denver CO 80225 Phone (303)-236-5656 Fax (303)-236-5349 Mark Hall To: C14-L@LISTSERV.ARIZONA.EDU Sent by: cc: Radiocarbon Subject: freshwater mollusc shell dates Mailing List 12/02/00 12:58 AM Please respond to Radiocarbon Mailing List While its clear I am probably not looking at the right issues of RADIOCARBON, but would anyone have a suggestion on which curve (marine or terristrial) one should use when calibrating C14 dates from freshwater mollusc species that are typically resident in shallow waters (less than 10 m)? Thanks in advance, Mark Hall markhall@gol.com =========================================================================== To unsubscribe from this list, send the command SIGNOFF C14-L to LISTSERV@LISTSERV.ARIZONA.EDU, or send a request to C14-L-request@LISTSERV.ARIZONA.EDU. =========================================================================== To unsubscribe from this list, send the command SIGNOFF C14-L to LISTSERV@LISTSERV.ARIZONA.EDU, or send a request to C14-L-request@LISTSERV.ARIZONA.EDU. ========================================================================= Date: Tue, 5 Dec 2000 08:49:22 -0700 Reply-To: Radiocarbon Mailing List Sender: Radiocarbon Mailing List From: Kim T Elliott Subject: Temperature dependence Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" >Date: Mon, 4 Dec 2000 14:49:18 -0800 (PST) >From: Yoav Me-Bar >Subject: Temperature dependence >To: editor@radiocarbon.org > >Dear Editor, >I write to you as a representative of the radiocarbon >listserv. >My question concerns the temperature dependence of the >disintegration rate. Samples that were taken from >under hot volcanic units were at high temperatures (a >few hundred to a thousand degrees C) for a long time >(a few months or more). Although temperature is >primarily an electronic, atomic and molecular effect >and not a nuclear one, can an extended period of high >temperature exposure change somewhat the rate of >disintegration and thus affect the dating of such >samples? > >Sincerely, > > > >===== >Dr. Yoav Me-Bar >Texas Archaeological Research Laboratory >The University of Texas at Austin >Pickle Research Campus, Bldg. 5 >Austin TX 78758 >Phone: 512-471-5960 >Fax: 512-471-5973 > >__________________________________________________ >Do You Yahoo!? >Yahoo! Shopping - Thousands of Stores. Millions of Products. >http://shopping.yahoo.com/ > > =========================================================================== To unsubscribe from this list, send the command SIGNOFF C14-L to LISTSERV@LISTSERV.ARIZONA.EDU, or send a request to C14-L-request@LISTSERV.ARIZONA.EDU. ========================================================================= Date: Tue, 5 Dec 2000 09:41:07 -0700 Reply-To: Radiocarbon Mailing List Sender: Radiocarbon Mailing List From: Warren Beck Subject: Re: freshwater mollusc shell dates In-Reply-To: <00fb01c05c2d$44b266c0$12e6fea9@gol.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" >While its clear I am probably not looking at the right issues of >RADIOCARBON, but would anyone have a suggestion on which curve (marine or >terristrial) one should use when calibrating C14 dates from freshwater >mollusc species that are typically resident in shallow waters (less than 10 >m)? > >Thanks in advance, >Mark Hall >markhall@gol.com Dear Mark, Thats really a tough call. The reason being that freshwater lakes & streams exhibit a wide range of reservoir effects from negligible to thousands of years. Worse yet, freshwater reservoir effects are prone to significant variability, sometimes even on seasonal time scales. The main causes of variability are 1) changes in the amount of "hard-water" from ground water input, relative to inputs from other younger sources such as streams or rivers; 2)Changes in wind intensity driven exchange of CO2 between the atmosphere and water body. While radiocarbon measurements in lacustrine organisms are of course interesting in their own right, if you are interested in deriving a chronology for your lake sediment profile, you are better off trying to isolate terrestrial plant fossils in the sediment for dating. If this is not possible, you might be lucky enough to find someone elses estimate of the reservoir effect for the particular lake you are working on, but be advised that this value is unlikely to be constant through time. I hope this helps. Sincerely, Warren Beck Warren Beck NSF Arizona AMS Facility Department of Physics PAS Bldg. #81 University of Arizona Tucson AZ 85721 Ph#520-621-4277 Fax#520-621-9619 =========================================================================== To unsubscribe from this list, send the command SIGNOFF C14-L to LISTSERV@LISTSERV.ARIZONA.EDU, or send a request to C14-L-request@LISTSERV.ARIZONA.EDU. ========================================================================= Date: Wed, 6 Dec 2000 08:47:38 +1300 Reply-To: Radiocarbon Mailing List Sender: Radiocarbon Mailing List From: Rodger Sparks Subject: Re: Temperature dependence Mime-Version: 1.0 Content-type: text/plain; charset=us-ascii The simple answer to this question is that temperature can affect the chemical composition and isotopic constitution of materials, but it will have no effect whatever on the rate of decay of radiocarbon. More important is the question of just what are you trying to date? Radioactive dating carries the assumption that you have an essentially homogeneous material that has maintained its integrity from a specific time (when it was "formed"), so that the content of a radioactive isotope such as 14C can be used to deduce the time that has elapsed since formation. From the brief description of the environment of these samples it seems to me it could be very difficult to establish the validity of this assumption unless,for example, you are dealing with carbonised plant remains that have been sealed off from the environment during and after the period of intense heating. The possibility of carbon exchange with surrounding, or inflowing, material would need to be considered. The integrity of your sample material is what you need to be concerned about, not the rate of radioactive decay. Rodger Sparks >Date: Mon, 4 Dec 2000 14:49:18 -0800 (PST) >From: Yoav Me-Bar >Subject: Temperature dependence >To: editor@radiocarbon.org > >Dear Editor, >I write to you as a representative of the radiocarbon >listserv. >My question concerns the temperature dependence of the >disintegration rate. Samples that were taken from >under hot volcanic units were at high temperatures (a >few hundred to a thousand degrees C) for a long time >(a few months or more). Although temperature is >primarily an electronic, atomic and molecular effect >and not a nuclear one, can an extended period of high >temperature exposure change somewhat the rate of >disintegration and thus affect the dating of such >samples? > >Sincerely, > > > >===== >Dr. Yoav Me-Bar >Texas Archaeological Research Laboratory >The University of Texas at Austin >Pickle Research Campus, Bldg. 5 >Austin TX 78758 >Phone: 512-471-5960 >Fax: 512-471-5973 =========================================================================== To unsubscribe from this list, send the command SIGNOFF C14-L to LISTSERV@LISTSERV.ARIZONA.EDU, or send a request to C14-L-request@LISTSERV.ARIZONA.EDU. ========================================================================= Date: Wed, 6 Dec 2000 11:05:50 +1100 Reply-To: dizzy@better.net.au Sender: Radiocarbon Mailing List From: Richard Gillespie Subject: Re: freshwater mollusc shell dates In-Reply-To: <00fb01c05c2d$44b266c0$12e6fea9@gol.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" ; format="flowed" Mark asked: >would anyone have a suggestion on which curve (marine or >terristrial) one should use when calibrating C14 dates from freshwater >mollusc species that are typically resident in shallow waters (less than 10 >m)? A possible solution would be to do a "reservoir effect" experiment on modern and museum shells from the same or similar lakes. This would determine the deviation from the terrestrial standard and allow use of that calibration curve. cheers, richard Richard Gillespie Radiocarbon Dating Consultant Dizzy Heights, Ripps Road Stokers Siding NSW 2484 Australia Phone: +612 6677 9500 Email: dizzy@better.net.au =========================================================================== To unsubscribe from this list, send the command SIGNOFF C14-L to LISTSERV@LISTSERV.ARIZONA.EDU, or send a request to C14-L-request@LISTSERV.ARIZONA.EDU. ========================================================================= Date: Wed, 6 Dec 2000 10:31:56 +0000 Reply-To: Radiocarbon Mailing List Sender: Radiocarbon Mailing List From: Paula Reimer Subject: Re: freshwater mollusc shell dates MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Dear all, I agree with Warren about the potential problems with the reservoir corrections for freshwater mollusks, although not all lakes have carbonate groundwater inputs. I would recommend using the atmospheric calibration curve, however, because of the relatively rapid turnover of carbon in lakes and rivers, in general, and because the marine calibration curve (for the first 8800 years BP) is based on an ocean model with various parameters that would not pertain to lake circulation. For the freshwater mollusks, the estimated reservoir correction would need to be subtracted from the radiocarbon ages before calibrating. Sincerely, Paula Reimer Warren Beck wrote: > >While its clear I am probably not looking at the right issues of > >RADIOCARBON, but would anyone have a suggestion on which curve (marine or > >terristrial) one should use when calibrating C14 dates from freshwater > >mollusc species that are typically resident in shallow waters (less than 10 > >m)? > > > >Thanks in advance, > >Mark Hall > >markhall@gol.com > > Dear Mark, > > Thats really a tough call. The reason being that freshwater lakes & > streams exhibit a wide range of reservoir effects from negligible to > thousands of years. Worse yet, freshwater reservoir effects are prone to > significant variability, sometimes even on seasonal time scales. The main > causes of variability are 1) changes in the amount of "hard-water" from > ground water input, relative to inputs from other younger sources such as > streams or rivers; 2)Changes in wind intensity driven exchange of CO2 > between the atmosphere and water body. While radiocarbon measurements in > lacustrine organisms are of course interesting in their own right, if you > are interested in deriving a chronology for your lake sediment profile, you > are better off trying to isolate terrestrial plant fossils in the sediment > for dating. If this is not possible, you might be lucky enough to find > someone elses estimate of the reservoir effect for the particular lake you > are working on, but be advised that this value is unlikely to be constant > through time. I hope this helps. > > Sincerely, > > Warren Beck > > Warren Beck > NSF Arizona AMS Facility > Department of Physics > PAS Bldg. #81 > University of Arizona > Tucson AZ 85721 > > Ph#520-621-4277 > Fax#520-621-9619 > > ============================================================================ > To unsubscribe from this list, send the command SIGNOFF C14-L to > LISTSERV@LISTSERV.ARIZONA.EDU, or send a request to C14-L-request@LISTSERV.ARIZONA.EDU. -- ****************************************** Dr. Paula J. Reimer School of Archaeology & Palaeoecology Queen's University of Belfast Belfast BT7 1NN Northern Ireland Phone: 44-(0)28-9027-3980 FAX: 44-(0)28-9031-5779 e-mail: p.j.reimer@qub.ac.uk http://www.qub.ac.uk/arcpal/staff/reimer =========================================================================== To unsubscribe from this list, send the command SIGNOFF C14-L to LISTSERV@LISTSERV.ARIZONA.EDU, or send a request to C14-L-request@LISTSERV.ARIZONA.EDU. ========================================================================= Date: Thu, 7 Dec 2000 15:06:50 +0300 Reply-To: zaretsk Sender: Radiocarbon Mailing List From: zaretsk Organization: GIN Subject: repeated dating Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Hello C14-L, Dear listserv, I am interested in publications on repeater radiocarbon dating of ONE geological (or archeological or paleoenvironmental) event,with dates obtained from various kinds of organic detritus. Thanks in advance Natasha Zaretskaia Moscow Geological Institute -- Best regards, zaretsk mailto:zaretsk@geo.tv-sign.ru =========================================================================== To unsubscribe from this list, send the command SIGNOFF C14-L to LISTSERV@LISTSERV.ARIZONA.EDU, or send a request to C14-L-request@LISTSERV.ARIZONA.EDU. ========================================================================= Date: Fri, 22 Dec 2000 11:21:02 +0000 Reply-To: Radiocarbon Mailing List Sender: Radiocarbon Mailing List From: Stewart Freeman Subject: Scots AMS Mime-version: 1.0 Content-type: text/plain; charset="US-ASCII" Content-transfer-encoding: 7bit The SUERC is pleased to announce the creation of a new accelerator mass spectrometry laboratory for environmental science. The facility will complement established radiocarbon and other cosmogenic isotope radiometric and AMS-sample preparation labs. An order has been placed with NEC for a 5 MV instrument with anticipated useful capabilities for Be, C, Al, Cl and I AMS. The much motorised and automated system includes both a high capacity solid sample ion source and one for both solid and gas sample operation intended for small sample C14 analysis. The laboratory building is to be completed in 2001, with the facility due to be commissioned in 2002. Staff are to be recruited next year. Happy holidays everyone! -- Stewart P.H.T. Freeman Scottish Universities Environmental Research Centre Scottish Enterprise Technology Park East Kilbride G75 0QF email: TooDeep@suerc.gla.ac.uk direct: 01355 270138, voicemail & fax: 0870 1287142 switchboard: 01355 223332, SUERC fax: 01355 229898 (US voicemail & fax: (630) 214-6597) =========================================================================== To unsubscribe from this list, send the command SIGNOFF C14-L to LISTSERV@LISTSERV.ARIZONA.EDU, or send a request to C14-L-request@LISTSERV.ARIZONA.EDU.