========================================================================= Date: Mon, 8 Jul 1996 09:53:29 -0500 Reply-To: Radiocarbon Mailing List Sender: Radiocarbon Mailing List From: "Melissa C. Winans" Subject: Univ. Texas Vertebrate Paleontology WWW Comments: To: Museum-L LISTSERV , Musweb-L LISTSERV , "Nat. Hist. Coll. LISTSERV" , Paleonet , Quaternary LISTSERV , Taxacom LISTSERV , "Vert. Paleo. LISTSERV" Comments: cc: Mary Ann Rankin , Ernest Lundelius , Timothy Rowe , Wann Langston , "N. MacLeod" Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" At long last, and with very generous financial assistance from the dean of the College of Natural Sciences, the University of Texas Vertebrate Paleontology & Radiocarbon Laboratory has made it onto the Web. Our URL is: http://www.utexas.edu/research/vprl Initial offerings include information about both labs, links to their staff and students (both current and former), a searchable account of sample requirements and pretreatment techniques for various types of radiocarbon samples, and a modest-sized test of a searchable version of the lab's vertebrate fossil databases. **************************************************************** Melissa C. Winans, Collection Manager (mcwinans@mail.utexas.edu) Vertebrate Paleontology Laboratory Phone: 512-471-6087 J.J. Pickle Research Campus Fax: 512-471-5973 University of Texas, Austin, TX 78712 ========================================================================= Date: Tue, 9 Jul 1996 10:15:46 -0400 Reply-To: Radiocarbon Mailing List Sender: Radiocarbon Mailing List From: Chris Beekman Subject: Shell dates C14L members, As I mentioned once before in a previous post, I am working on the calibration of previously published age determinations for western and northwestern Mexican archaeology. The project is nearly finished, but I have a few questions that the numerous articles and books on the method did not clarify for me. Age determinations on shell are unfortunately numerous in the area, and I could use some clarification about the modifications. I'll take an age determination, UCLA 593c 1790+- 100, as an example. It was on Pacific shell (although Caribbean shell was frequently traded into the area in precolumbian times), so as I understand it, I use the coastal delta R value of 185+-20 years to modify the date (Stuiver and Braziunas 1993: Modeling Atmospheric 14C influences and 14C ages of marine samples to 10,000 BC: Fig 16). My doubt stems from the fact that the resulting date is much more recent (by about 500 years!) than the other four age determinations from the same context. My main question is, on what kind of shell is this modification to be used? Shallow water, deep water species? Anything living along this stretch of coastline? Secondly, fractionation corrections for shell are large, but as people responded to my previous post, evidently laboratories have been making fractionation calculations and corrections for years, but only in recent years has the information been given to archaeologists, making it appear as if the calculations were not done previously. This is critical for me, as several archaeologists have tried to go back and modify dates on maize and shell by making modifications for fractionation. Are they likely making corrections that have already been made? Thanks for your help. Christopher S. Beekman Box 6050-B Vanderbilt University Nashville, Tennessee 37235 Telephone: (615) 297-4663 FAX: (615) 343-0230 Email: CBEEKMAN@AOL.COM ========================================================================= Date: Tue, 9 Jul 1996 11:07:49 -0500 Reply-To: Radiocarbon Mailing List Sender: Radiocarbon Mailing List From: "Melissa C. Winans" Subject: Re: Shell dates Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" At 10:15 AM 7/9/96 -0400, Christopher S. Beekman wrote: > Secondly, fractionation corrections for shell are large, but >as people responded to my previous post, evidently laboratories >have been making fractionation calculations and corrections for >years, but only in recent years has the information been given to >archaeologists, making it appear as if the calculations were not >done previously. This is critical for me, as several >archaeologists have tried to go back and modify dates on maize >and shell by making modifications for fractionation. Are they >likely making corrections that have already been made? As the "front man" for our radiocarbon lab, I get asked this question pretty frequently. Unfortunately, there is no easy, one-size-fits-all answer. Just as you say, correction information may not have been reported by some labs in the early years (although the U.T. lab always has included this information in its reports); but it is equally true that not all archaeologists have paid attention to the information even when it was reported - probably because they did not always understand its significance. Another factor is that for many years delta-13C corrections were an optional extra (for which the customer was charged an additional fee), and a significant number of customers chose to save a little money by opting not to have it done. The upshot of all this is that the only way to tell for sure is to go back to the original records of the lab that did the analyses, assuming that they are still available. If any of the dates about which you are uncertain bear "Tx-" prefixes, we would be happy to look them up in our files and tell you what we can about them. **************************************************************** Melissa C. Winans, Collection Manager (mcwinans@mail.utexas.edu) Vertebrate Paleontology Laboratory Phone: 512-471-6087 J.J. Pickle Research Campus Fax: 512-471-5973 University of Texas, Austin, TX 78712 ========================================================================= Date: Tue, 9 Jul 1996 09:53:02 -0700 Reply-To: Radiocarbon Mailing List Sender: Radiocarbon Mailing List From: Jon M Erlandson Subject: Re: Shell dates MIME-version: 1.0 Content-transfer-encoding: 7BIT Christopher: I have been radiocarbon dating marine shells from the Pacific Coast of North America (CA, OR, AK) for years, without running into serious problems. My assessment of marine shell as a dating medium is that it is generally quite reliable if sample collection, selection, and pretreatment are done appropriately. Marine shells even have some advantages over wood or charcoal in that they generally don't suffer from the "Old Wood" effect or the DeVries effect, both of which cause potentially serious uncertainties about the age of cultural events in the past. To calibrate marine shell dates, however, you must be sure to calibrate 13C adjusted ages, which generally push uncorrected dates on Pacific Coast shells back in time about 420 +/- 20 years. Your problem with the cited UCLA date could well be that it was not 13C adjusted prior to your calibration. I'm afraid you will have to determine which shell dates are 13C adjusted before you can effectively calibrate them. Despite international conventions, a number of labs still do not routinely provide 13C adjusted dates unless you specifically request them. To my knowledge, all AMS dates include the adjustment. I think the La Jolla lab started routinely doing the adjustments in the 1970s, but I'm not aware that UCLA instituted any such procedure. You should probably query individuals labs to be certain. Good luck, Jon Erlandson University of Oregon ========================================================================= Date: Tue, 9 Jul 1996 17:50:32 -0400 Reply-To: Radiocarbon Mailing List Sender: Radiocarbon Mailing List From: "Kenneth E. Bannister" Subject: GROUNDWATER Mailing List Comments: To: afwater@aqua.ccwr.ac.za, AQUIFER@VM.CSATA.IT, BURG-CEN@NIC.SURFNET.NL, bww@ukcc.uky.edu, ccwr_users@aqua.ccwr.ac.za, cee-environment@ucdavis.edu, cee-geotecht@ucdavis.edu, CIVIL-L@unb.ca, cwa-environment@lists.Colorado.EDU, cnie@csf.colorado.edu, dialog-agua-l@acc.fau.edu, DLO-E-INFO@NIC.SURFNET.NL, eia@pan.cedar.univie.ac.at, elan@csf.colorado.edu, engineering-all@mailbase.ac.uk, engineering-geotech@mailbase.ac.uk, env-wat@lists.Colorado.EDU, envbus-l@rec.hu, envcee-l@rec.hu, enveng-l@cedar.univie.ac.at, environment-l@cornell.edu, ebc@shore.net, environmental-a@acpub.duke.edu, envmajors@acpub.duke.edu, envst-l@brownvm.Brown.edu, enveng@lists.Colorado.EDU, FELT-L@mecheng.asme.org, geo-computer-models@mailbase.ac.uk, geo-env@mailbase.ac.uk, geo-gig@mailbase.ac.uk, geo-tectonics@mailbase.ac.uk, geochem@u.washington.edu, GEOED-L@UWF.BITNET, gwcan-l@gw2.cciw.ca Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" ANNOUNCING: GROUNDWATER and GROUNDWATER-DIGEST Internet Mailing Lists Please join our global discussion group on groundwater and related topics. There are over 2100 members worldwide, from over 50 different countries. There are many USGS, EPA and Corps of Engineers members. If you have a groundwater question, this is the place to post it. ................................................................ To subscribe to GROUNDWATER send e-mail to: majordomo@ias.champlain.edu In the body of the e-mail type the command: subscribe GROUNDWATER ........................................................... For more information visit the Groundwater.Com Web Site. We hope you will join our lively discussion on this interesting topic. Apologies for the cross posting. Ken Bannister -------------------------------------------------------------- Kenneth E. Bannister President - BANNISTER RESEARCH & CONSULTING Owner - GROUNDWATER Mailing List http://www.groundwater.com KenBannister@groundwater.com Sponsor- Addison United Soccer Club - 1996 Vermont Cup Runner-Up U - 12 Olympic Development League Soccer -------------------------------------------------------------- ========================================================================= Date: Wed, 10 Jul 1996 10:41:25 -0700 Reply-To: Radiocarbon Mailing List Sender: Radiocarbon Mailing List From: Paula Reimer Subject: Re: shell dates Comments: To: cbeekman@aol.com Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII To Christopher Beekman, in response to some your questions: > My main question is, on what kind of shell is this >modification to be used? Shallow water, deep water species? >Anything living along this stretch of coastline? The Delta R values in Stuiver and Braziunas (1993) are applicable to shell samples from the surface ocean (average global reservoir age R ~400). The deep ocean reservoir age was modeled at ~1700 yr so if you truly had samples from the deep ocean the correction would need to be about 1300 yr greater. Shells from rivers or estuaries pose additional problems because more atmospheric CO2 may be mixed in or the watershed may include carbonates. In the case of the Pacific coast of Baja California, the suggested Delta R value of 185 +/- 20 (Stuiver et al.,1986) is the mean of eight shell samples collected in the 1930's and radiocarbon dated at UCLA (Berger et al, 1966). The individual Delta R's ranged from 132 +/- 51 to 307 +/- 45 with a scatter sigma of about 70 years. The point being that variability in local upwelling and mixing conditions will affect the actual reservoir the sample grew in. Note that 2 shell samples from the Gulf of California gave a mean Delta R value of 520 +/- 40. > Age determinations on shell are unfortunately numerous in >the area, and I could use some clarification about the >modifications. I'll take an age determination, UCLA 593c 1790+- >100, as an example. It was on Pacific shell (although Caribbean >shell was frequently traded into the area in precolumbian times), >so as I understand it, I use the coastal delta R value of 185+-20 >years to modify the date (Stuiver and Braziunas 1993: Modeling >Atmospheric 14C influences and 14C ages of marine samples to >10,000 BC: Fig 16). My doubt stems from the fact that the >resulting date is much more recent (by about 500 years!) than the >other four age determinations from the same context. It would be interesting to have more information on the other dates you mention. Is the archaeological context certain? Are the dates on shell also? Have they been calibrated? When you say you have modified the radiocarbon age using the delta R value of 185, does that mean you took the conventional 14C age - 400 - 185 to get a reservoir corrected age or did you calibrate it with the marine calibration curve and input the Delta R value of 185? While Jon Erlandson is absolutely right that radiocarbon dates must be corrected for 13C fractionation, I would find it hard to believe that this was not done at UCLA from early on. It would be a good idea to check with the lab there to verify this. Good luck and let me know what you find out! Sincerely, Paula Reimer References: Berger, R., Taylor, R.E. and Libby, W.F., 1966, Radiocarbon content of marine shells from the California and Mexican west coast. Science. 153:864-866. Stuiver, M., Pearson, G.W., and Braziunas, T.F., 1986, Radiocarbon Age Calibration of Marine Samples Back to 9000 cal yr BP. Radiocarbon. 28:980-1021. ****************************************************************** * \ | / * * /\ - ( ) - * * //\\ / | \ Paula J. Reimer * * ///\\\ Quaternary Research Ctr Box 351360 * * ////\\\\ University of Washington * * ____||____ Seattle, WA 98195-1360 * * \~~~~~~~~/ Phone: (206) 543-6327 * * \======/ FAX: (206) 543-3191 * * \====/ e-mail: pjreimer@u.washington.edu * ****************************************************************** ========================================================================= Date: Wed, 24 Jul 1996 12:48:52 -0700 Reply-To: Radiocarbon Mailing List Sender: Radiocarbon Mailing List From: David Sewell Subject: Announcement of 16th International 14C Conference MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit I've just posted the announcement and first call for papers for the 16th International Radiocarbon Conference, to be held in Groningen, The Netherlands, 16-20 June 1997, on the Radiocarbon WWW server (http://packrat.aml.arizona.edu/). The announcement includes links to the WWW server at the Groningen Centre for Isotope Research, which should contain periodically updated information on the conference, and an e-mail link to the conference organizers. If you don't have access to a WWW browser, you can send for information via e-mail to C14@phys.rug.nl. David Sewell -- RADIOCARBON: An International Journal of Cosmogenic Isotope Research Department of Geosciences, University of Arizona 4717 E. Ft. Lowell Rd., Tucson, Arizona 85712 USA Telephone: 1-520-881-0857 Fax: 1-520-881-0554 General e-mail address: c14@packrat.aml.arizona.edu WWW server: http://packrat.aml.arizona.edu/ ========================================================================= Date: Mon, 29 Jul 1996 16:07:18 +0200 Reply-To: Radiocarbon Mailing List Sender: Radiocarbon Mailing List From: Peter Becker-Heidmann Subject: Help in searching Radiocarbon lab In-Reply-To: from "David Sewell" at Jul 24, 96 12:48:52 pm Content-Type: text Can anybody help this colleage? Forwarded message:----------------------------------------------------- Date: Mon, 29 Jul 1996 15:14:21 +1000 Reply-To: Research in Quaternary Science Sender: Research in Quaternary Science From: David Godley Subject: Help with C14 lab code To: Multiple recipients of list QUATERNARY Status: RO Netters, I was hoping someone out there could help me solve a bit of a problem. I have a report of an excavation in Central Thailand which mentions three radiocarbon determinations. The lab code mentioned is WSR. There are no registered labs using this code. The details in the report are incomplete and I am trying to track down the complete details from the lab that did the dating. Hence the problem with the lab code. I have already written the Washington State University (WSU) lab in hope that is is merely a typo. Any other suggestions? Regards, David Godley _____________________________________________________________________________ David Godley Davidg@aurora.cc.monash.edu.au Dept of Geography David.Godley@lib.monash.edu.au Monash University Clayton 3168 Phone : +61-3-990-52943 AUSTRALIA Fax. : +61-3-990-52948 -- Peter Becker-Heidmann Institut fuer Bodenkunde Phone: +49 40 4123 2003 Allende-Platz 2 Fax: +49 40 4123 2024 D-20146 Hamburg E-Mail: PBeckerH@Uni-Hamburg.de GERMANY WWW: http://www.geowiss.uni-hamburg.de/geo/i-boden/tt14c.htm