Jansma, E.

Kars, H.

Plicht, J. van der

English

We have performed a high-precision C-14 wiggle-matching study on two oak beams from the ''Castle of Amsterdam''. These beams are also dated by dendrochronology. Our two dating methods can only be made consistent using the recommended calibration curve (1986) instead of the revised one (1993).</p

Dissertations of the University of Groningen

   University of GroningenThe "Amsterdam Castle"Plicht, J. van der; Jansma, E.; Kars, H.Published in:RadiocarbonIMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:1995Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):Plicht, J. V. D., Jansma, E., & Kars, H. (1995). The "Amsterdam Castle": A case study of wiggle matchingand the proper calibration curve. Radiocarbon, 37(3), 965-968.CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license.More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne-amendment.Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 05-06-2022[RADIOCARBON, VoL. 37, No. 3, 1995, P. 965-968] THE "AMSTERDAM CASTLE": A CASE STUDY OF WIGGLE MATCHING AND THE PROPER CALIBRATION CURVE J. VAN DER PLICHT,1 E. JANSMA2 and H. KARS3 ABSTRACT. We have performed a high-precision 14C wiggle-matching study on two oak beams from the "Castle of Amster- dam". These beams are also dated by dendrochronology. Our two dating methods can only be made consistent using the rec- ommended calibration curve (1986) instead of the revised one (1993). INTRODUCTION In the spring of 1994, archaeologists discovered a medieval brick foundation in the center of Amsterdam. Termed "The Castle of the Lords of Amstel", it was a find of possible great historical importance, especially if it could be dated to AD 1200. A castle at the river Amstel has been described in historical documents but the castle itself has never been found. Large oak beams were found protruding from the brickwork. They were first dated by dendrochronology. The results implied that the foundation was several decades younger than expected. However, a few 14C dates centered around 1200, using the latest published calibration curve (Stuiver and Pearson 1993). Thus a seeming discrepancy was created between two independent dating methods (Jansma and Kars, 1995). We decided to perform a high-resolution 14C wiggle-matching study on two of the oak beams that were also dated by dendrochronology, beams "sample 6" and "sample 9". Our resolution of the discrepancy (van der Plicht 1995) was only possible using the 1986 bidecadal calibration curve (Stuiver and Pearson 1986), instead of the 1993 one (Stuiver and Pearson 1993). We here report on this case study. Dendrochronology The wood samples were compared to available master chronologies, including the Netherlands His- torical Chronology 1(the southern Netherlands/Belgium/Germany; AD 427-1752; Jansma 1995); the Central German Chronology (690 BC-AD 1975; Hollstein 1980); the Weserbergland Chronology (Germany; AD 1004-1970; Delorme 1973); the Eastern Belgium Chronology (AD 672-1986; Hoff- summer 1989); and the Lower Saxony Growth Region 1 Chronology (Germany; AD 915-1991; Leuschner, unpublished data). The chronologies used and the statistics that accompany the dendro- chronological dates of samples 6 and 9 are shown in Table 1. The tree rings in sample 6 date from 1157 to 1272. The number of missing sapwood rings was esti- mated as 4 ± 2, so that tree number 6 was felled between 1274 and 1278. The tree rings in sample 9 date from 1103 to 1215. In addition, 30 sapwood rings (including the last formed ring) were counted. Tree number 9 therefore was felled in 1245. Radiocarbon The results of the radiocarbon measurements for trees number 6 and 9 are shown in Table 2. We dated the sapwood samples (23 and 24 rings, respectively), and groups of 10 annual rings as indi- cated in the table. The rings are counted from the outside; here they are used only in a relative way. The samples were analyzed for 14C with the highest possible precision in the large (25 liter) Gronin- gen counter. 1Centre for Isotope Research (CIO), University of Groningen, Nijenborgh 4, 9747AG Groningen, The Netherlands 2Dutch Centre for Dendrochronology (RING), Kerkstraat 1, 3811CV Amersfoort, The Netherlands 3Dutch State Service for Archaeological Soil Research (ROB), Kerkstraat 1, 3811CV Amersfoort, The Netherlands 965 Tnst.E 1. The Match Between Samples 6 and 9 and Some Master Chronologies Date of PVt t-value $ Sample n* last mea- sured ring sapwood date chronology 6 116 1272 2 historical 1 Central Germany 68.3 68.3 Weserbergland 66.5 66.5 Eastern Belgium 61.3 613 9 113 1215 historical l Central Germany 62.1 62.9 Weserbergland 69.6 67.9 Niedersachsen sub 1 62.9 64.7 *n = number of rings; t PV = percentage parallel variation; $t = student's t-value; §a = level of significance; # = series of total ring width; * * = series of standardized and detrended ring widths TABLE 2. Tree-Ring '4C Measurements for Samples 6 and 9 Sample no. Lab code GrN- age (BP) ring 6 21167 757 ± 15 (sapwood) 21175 817 ± 10 33-43 21177 839 t 12 533 21178 839± 13 63-73 21180 870± 12 83-93 21182 862 ±9 103-113 9 21154 807± 11 (sapwood) 21156 844 ± 17 28-38 21158 848 ± 10 48-58 21160 853 ±17 68-78 21162 906 ± 18 88-98 21164 930± 17 108-118 21166 952± 10 128-138 "Amsterdam Castle": A Case Study 967 The set of 14C dates for each tree can be "wiggle-matched" to the calibration curve by minimizing the quantity (Pearson 1986). [BP1 (curve) - BP1 (date) ]2 (1) The solution of the wiggle-match procedure to the recommended bidecadal calibration curve (Stuiver and Pearson, 1986) is shown in Figure 1(sample 6) and Figure 2 (sample 9). The figures show the calibration curve (solid line), the 1Q error envelope of the curve (dotted line), the individ- ual calibration data points and-drawn as rectangles-the set of data matched to the curve. The sides of the rectangles represent the error bars: vertically, the errors (1Q) for the 14C dates and hori- zontally, the ring width of the samples. For sapwood, this is 23 rings for tree number 6 and 24 for number 9; in all other cases, 10 annual rings were taken. Note that also the calibration data points are bidecadal and are thus an average for 20 annual rings. The cutting date of the tree, deduced from this procedure, is 1278 cal AD for sample 6 and 1250 cal AD for sample 9. C:\CALSOWIOOLEVIZKGB.DTA 1000 BP 800 C.I.O. Oroningen 10?O 1120 li70 1220 1270 cal AD Fig. 1. Wiggle-matched result for wood sample 6 The Calibration Curve 1320 The results of the case study reported here, obtained by two independent dating methods, dendro- chronology and radiocarbon, are in excellent agreement. For the radiocarbon part of the exercise, this agreement could only be obtained by high-resolution wiggle matching to the 1986 calibration curve (Stuiver and Pearson 1986), which formally is still recommended (hook 1986). This curve has been revised recently by applying a correction of 18 radiocarbon years (Stuiver and Pearson 1993). Using this corrected calibration curve, agreement between the dendro- and 14C dates in the case study reported here is not possible: the cutting dates of the trees considered are then 15-20 (calendar) years too young. This observation therefore sup- 968 J. van der Pticht, E. Jansma and H. Kars ports the contention of McCormac et al. (1995) that the revision of the calibration curve in hindsight is not justified. C.I.O. Oroningen 8P 800 1020 Fig. 2. Wiggle-matched result for wood sample 9 REFERENCES Delorme, A. (ms.) 1973 Dendrochronologische Untersu- chungen an Eichen des Sildlichen Weser- and Leineberglandes. Ph.D. dissertation, Universitat Got- tingen. Hoffsummer, P. (ms.) 1989 L'evolution des toits a deux versants dans le Bassin Mosan: L'apport de la dendro- chronologie (XI-XIXe sibcle) 1-3. Ph.D. dissertation, Universit de Liege. Hollstein, E. 1980 Mitteleuropaische Eichenchronolo- gie. Mainz am Rhein, Verlag Phillipp von Zabern. Jansma, E. 1992 Dendrochronological methods to deter- mine the origin of oak timber: A case study on wood from 's-Hertogenbosch. Helinium 32:195-214. 1995 (ms.) The development and application of lo- cal and regional tree-ring chronologies of oak for the purposes of archaeological and historical research in the Netherlands. Ph.D. dissertation, Universiteit Am- sterdam. Jansma, E. and Kars, H. 1995 Het dendrochronologisch onderzoek naar het "Kasteel van Amstel", Spiegel Historiael 30(1): 9-11. Mook, W. G. 1986 Recommendations / resolutions adopted by the Twelfth International Radiocarbon Conference. In Stuiver, M. and Kra, R. S., eds., Pro- 1170 1220 1270 cal AD 1320 ceedings of the 12th International 14C Conference. Ra- diocarbon 28(2A): 799. Pearson, G. W. 1986 Precise calendrical dating of known growth-period samples using a "curve fitting" tech- nique. In Stuiver, M. and Kra, R. S., eds., Proceedings of the 12th International 14C Conference. Radiocar- bon 28(2A): 292-299. van der Plicht, J. 1995 Nogmaals het "Kasteel van Ams- tel": de 14C-dateringen. Spiegel Historiael 7/8: 270- 272. Stuiver, M. and Pearson, G. W. 1986 High-precision cal- ibration of the radiocarbon time scale, AD 1950- 500 BC. In Stuiver, M. and Kra, R. S., eds., Calibration Issue. Radiocarbon 28(2B): 805-838. 1993 High-precision bidecadal calibration of the ra- diocarbon time scale, AD 1950-500 BC and 2500- 6000 BC. In Stuiver, M., Long, A. and Kra, R. S., eds., Calibration 1993. Radiocarbon 35(1):1-24. McCormac, F. G., Baillie, M. G. L., Pilcher, J. R., and Ka- lin, R. M. 1995 Location-dependent differences in the 14C content of wood. In Cook, G. T., Harkness, D. D., Miller, B. F and Scott, E. M., eds., Proceedings of the 15th International Radiocarbon Conference. Radio- carbon 37(2): 395-407. 

The "Amsterdam Castle":A case study of wiggle matching and the proper calibration curve

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The "Amsterdam Castle":A case study of wiggle matching and the proper calibration curve

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