Rahul Kumar Agrawal, Ranjan Kumar Mohanty, Ajayeta Rathi, Shreya Mehta, M G Yadava, Sanjeev Kumar, Amzad H Laskar
Estimation of residence time of groundwater, particularly in regions with inadequate surface waters are very important for formulating sustainable groundwater management policies. We developed a technique for extracting dissolved inorganic carbon (DIC) quantitatively from water for measuring its 14C contents and presented the analytical details here. We also measured stable carbon isotope ratio (δ13C) in soil CO2 and groundwater DIC to correct the groundwater 14C ages. In addition, 14C in soil CO2 were measured for making necessary correction in the initial activity of the recharging water. The corrected 14C contents in the groundwater samples were used to estimate their residence times employing Lumped Parameter Models (LPM), a set of mathematical models to account for the processes that take place during transport from the recharge to the sampling spots. We present a case study focused on the calculation of radiocarbon ages and residence times for a groundwater sample collected from the campus of Physical Research Laboratory in Ahmedabad, Gujarat, India. The study also includes estimations of groundwater residence times using previously measured 14C ages of groundwater samples from Gujarat, India. Various factors controlling the groundwater ages in the LPM and their applicability are discussed.
估算地下水的停留时间,尤其是在地表水不足的地区,对于制定可持续的地下水管理政策非常重要。我们开发了一种从水中定量提取溶解无机碳(DIC)以测量其 14C 含量的技术,并在此介绍了分析细节。我们还测量了土壤 CO2 和地下水 DIC 中的稳定碳同位素比值(δ13C),以校正地下水 14C 年龄。此外,我们还测量了土壤 CO2 中的 14C 含量,以便对补给水的初始活性进行必要的修正。地下水样本中校正后的 14C 含量可用于采用集合参数模型(LPM)估算其停留时间,集合参数模型是一套数学模型,用于解释从补给点到采样点的传输过程。我们介绍了一项案例研究,重点是计算从印度古吉拉特邦艾哈迈达巴德物理研究实验室校园采集的地下水样本的放射性碳年龄和停留时间。该研究还包括利用之前测量的印度古吉拉特邦地下水样本的 14C 年龄估算地下水的停留时间。研究还讨论了控制 LPM 中地下水年龄的各种因素及其适用性。
{"title":"Estimation of groundwater residence time using radiocarbon and stable carbon isotope ratio in dissolved inorganic carbon and soil CO2","authors":"Rahul Kumar Agrawal, Ranjan Kumar Mohanty, Ajayeta Rathi, Shreya Mehta, M G Yadava, Sanjeev Kumar, Amzad H Laskar","doi":"10.1017/rdc.2024.43","DOIUrl":"https://doi.org/10.1017/rdc.2024.43","url":null,"abstract":"<p>Estimation of residence time of groundwater, particularly in regions with inadequate surface waters are very important for formulating sustainable groundwater management policies. We developed a technique for extracting dissolved inorganic carbon (DIC) quantitatively from water for measuring its <span>14</span>C contents and presented the analytical details here. We also measured stable carbon isotope ratio (δ<span>13</span>C) in soil CO<span>2</span> and groundwater DIC to correct the groundwater <span>14</span>C ages. In addition, <span>14</span>C in soil CO<span>2</span> were measured for making necessary correction in the initial activity of the recharging water. The corrected <span>14</span>C contents in the groundwater samples were used to estimate their residence times employing Lumped Parameter Models (LPM), a set of mathematical models to account for the processes that take place during transport from the recharge to the sampling spots. We present a case study focused on the calculation of radiocarbon ages and residence times for a groundwater sample collected from the campus of Physical Research Laboratory in Ahmedabad, Gujarat, India. The study also includes estimations of groundwater residence times using previously measured <span>14</span>C ages of groundwater samples from Gujarat, India. Various factors controlling the groundwater ages in the LPM and their applicability are discussed.</p>","PeriodicalId":21020,"journal":{"name":"Radiocarbon","volume":"7 1","pages":""},"PeriodicalIF":8.3,"publicationDate":"2024-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140812471","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A low-cost and computer-controlled graphitization system connected to an elemental analyzer (EA) has been designed and built at the NTUAMS Lab. This semiautomatic system equips 6-unit reactors for the graphitization of CO2 with H2 on the iron catalyst. The entire procedure takes about 7 hours for iron conditioning, sample combustion and loading, and graphitization. The system can produce good-quality graphite for samples containing 0.5–1.6 mg carbon mass, with the pressure yield of graphitization ranging from 57.7% to 87.1%. The average values of OXI and OXII agree well with the consensus value, but the result of ANU sucrose was observed to be slightly higher than the reported one. The background samples of anthracite over ten months yielded an average of 0.38±0.10 pMC (n=21) corresponding to a 14C age of 45 kyr BP. Intercomparison samples L and M of FIRI exhibit that the measured 14C ages are almost identical to the consensus values and have a small spread in these values. The system has been carrying out graphitization for total organic carbon (TOC) of peat samples, and providing a more efficient and convenient way for AMS 14C dating.
NTUAMS 实验室设计并建造了一个与元素分析仪(EA)相连的低成本计算机控制石墨化系统。这套半自动系统配备了 6 个反应器,用于在铁催化剂上将 CO2 与 H2 石墨化。整个过程大约需要 7 个小时,包括铁调节、样品燃烧和装载以及石墨化。该系统能为含碳量为 0.5-1.6 毫克的样品生产优质石墨,石墨化的压力产率为 57.7% 至 87.1%。OXI 和 OXII 的平均值与共识值吻合,但 ANU 蔗糖的结果略高于报告值。十个月的无烟煤本底样品的平均值为 0.38±0.10 pMC(n=21),对应的 14C 年龄为 45 kyr BP。FIRI 的互比样品 L 和 M 表明,测得的 14C 年龄与共识值几乎相同,而且这些值的差值较小。该系统对泥炭样本的总有机碳(TOC)进行了石墨化处理,为 AMS 14C 测年提供了更高效、更便捷的方法。
{"title":"A HOMEMADE SEMIAUTOMATIC GRAPHITIZATION DEVICE FOR AMS 14C DATING AT NTUAMS LAB","authors":"Tzu-Tsen Shen, Hong-Chun Li, Rick Qiu","doi":"10.1017/rdc.2024.48","DOIUrl":"https://doi.org/10.1017/rdc.2024.48","url":null,"abstract":"<p>A low-cost and computer-controlled graphitization system connected to an elemental analyzer (EA) has been designed and built at the NTUAMS Lab. This semiautomatic system equips 6-unit reactors for the graphitization of CO<span>2</span> with H<span>2</span> on the iron catalyst. The entire procedure takes about 7 hours for iron conditioning, sample combustion and loading, and graphitization. The system can produce good-quality graphite for samples containing 0.5–1.6 mg carbon mass, with the pressure yield of graphitization ranging from 57.7% to 87.1%. The average values of OXI and OXII agree well with the consensus value, but the result of ANU sucrose was observed to be slightly higher than the reported one. The background samples of anthracite over ten months yielded an average of 0.38±0.10 pMC (n=21) corresponding to a <span>14</span>C age of 45 kyr BP. Intercomparison samples L and M of FIRI exhibit that the measured <span>14</span>C ages are almost identical to the consensus values and have a small spread in these values. The system has been carrying out graphitization for total organic carbon (TOC) of peat samples, and providing a more efficient and convenient way for AMS <span>14</span>C dating.</p>","PeriodicalId":21020,"journal":{"name":"Radiocarbon","volume":"79 1","pages":""},"PeriodicalIF":8.3,"publicationDate":"2024-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140811487","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J Bates, V K Singh, R N Singh, Manisha Singh, Brij Mohan, Sudarshan Chakradhari, Abhay P Singh, Matthew Conte, Yongje Oh
Dates from recently excavated Gangetic site of Sakas in Bihar, India, place it at ca.1800–1100 BC. The ceramic and lithic chronologies have been interpreted as Early Farming, Transitional and Chalcolithic/Developed Farming in date. However, depending on where in the Ganges Plains is studied, the time frame of Early, Developed and Advanced Farming periods varies widely, from 7th millennium to 2nd millennium BC and beyond, making the chronological framing of absolute dates within a regional scheme highly complex. In this paper we report the new radiocarbon results from Sakas and note how while these are critical for cementing the absolute dating of the site, until such time as a more stable periodization linked not only to relative and absolute dates but also human lifeways within the different zones of the Ganges plains is created, there remains difficulties in understanding how Sakas and other sites of similar date fit into the changing social, cultural and economic systems in this region.
{"title":"Radiocarbon dates from the archaeological site of Sakas, Bihar, India","authors":"J Bates, V K Singh, R N Singh, Manisha Singh, Brij Mohan, Sudarshan Chakradhari, Abhay P Singh, Matthew Conte, Yongje Oh","doi":"10.1017/rdc.2024.42","DOIUrl":"https://doi.org/10.1017/rdc.2024.42","url":null,"abstract":"<p>Dates from recently excavated Gangetic site of Sakas in Bihar, India, place it at ca.1800–1100 BC. The ceramic and lithic chronologies have been interpreted as Early Farming, Transitional and Chalcolithic/Developed Farming in date. However, depending on where in the Ganges Plains is studied, the time frame of Early, Developed and Advanced Farming periods varies widely, from 7th millennium to 2nd millennium BC and beyond, making the chronological framing of absolute dates within a regional scheme highly complex. In this paper we report the new radiocarbon results from Sakas and note how while these are critical for cementing the absolute dating of the site, until such time as a more stable periodization linked not only to relative and absolute dates but also human lifeways within the different zones of the Ganges plains is created, there remains difficulties in understanding how Sakas and other sites of similar date fit into the changing social, cultural and economic systems in this region.</p>","PeriodicalId":21020,"journal":{"name":"Radiocarbon","volume":"44 1","pages":""},"PeriodicalIF":8.3,"publicationDate":"2024-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140811502","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Wendy Hlengiwe Khumalo, Helene Løvstrand Svarva, Damaris Zurbach, Marie-Josée Nadeau
Obtaining accurate radiocarbon (14C) results from wood samples requires the extraction of cellulose. In the past, this has been done using different combinations of methods including acidified bleaching, acid-base-acid, and strong bases. This often becomes a time-consuming task in most analyses, especially when single ring isotope chronologies are needed from wood samples. Using 14C and Fourier-transform infrared spectroscopy (FTIR), we tested four different pretreatment methods to determine their ability to produce high quality cellulose. We then adjusted the best methods to determine a method for pretreating wood laths of multiple rings. A sequence of base-acid-base-acid-bleach + strong base (BABAB+) and BABAB produced the most accurate results when compared to the Bomb20 Northern Hemisphere Zone 1 curve with an average difference in Δ14C of 1.3‰ and 5.8‰ respectively. These methods were adjusted to pretreat an entire wood lath and a comparison of the FTIR results suggest that our adjusted BABAB+ and BABAB produced high quality cellulose comparable to that of an individually pretreated ring. The possibility to pretreat wood lath samples has the potential to more than double the number of tree rings which can be pretreated in a week. This is a significant reduction in time when creating long tree ring chronologies.
{"title":"SQUEAKY CLEAN CELLULOSE: COMPARING PRETREATMENT EFFECTIVENESS ON SINGLE TREE RINGS AND WOODEN LATHS","authors":"Wendy Hlengiwe Khumalo, Helene Løvstrand Svarva, Damaris Zurbach, Marie-Josée Nadeau","doi":"10.1017/rdc.2024.20","DOIUrl":"https://doi.org/10.1017/rdc.2024.20","url":null,"abstract":"Obtaining accurate radiocarbon (<jats:sup>14</jats:sup>C) results from wood samples requires the extraction of cellulose. In the past, this has been done using different combinations of methods including acidified bleaching, acid-base-acid, and strong bases. This often becomes a time-consuming task in most analyses, especially when single ring isotope chronologies are needed from wood samples. Using <jats:sup>14</jats:sup>C and Fourier-transform infrared spectroscopy (FTIR), we tested four different pretreatment methods to determine their ability to produce high quality cellulose. We then adjusted the best methods to determine a method for pretreating wood laths of multiple rings. A sequence of base-acid-base-acid-bleach + strong base (BABAB+) and BABAB produced the most accurate results when compared to the Bomb20 Northern Hemisphere Zone 1 curve with an average difference in Δ<jats:sup>14</jats:sup>C of 1.3‰ and 5.8‰ respectively. These methods were adjusted to pretreat an entire wood lath and a comparison of the FTIR results suggest that our adjusted BABAB+ and BABAB produced high quality cellulose comparable to that of an individually pretreated ring. The possibility to pretreat wood lath samples has the potential to more than double the number of tree rings which can be pretreated in a week. This is a significant reduction in time when creating long tree ring chronologies.","PeriodicalId":21020,"journal":{"name":"Radiocarbon","volume":"249 1","pages":""},"PeriodicalIF":8.3,"publicationDate":"2024-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140559894","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yurij K Vasil’chuk, Alla C Vasil’chuk, Nadine A Budantseva, Alexander P Ginzburg, Igor V Tokarev, Jessica Yu Vasil’chuk
Accelerator mass spectrometry radiocarbon (AMS 14C) dating was used for determining the age of wedge ice. It has been found that between 11,270 and 6420 cal BP, or the Greenlandian and Northgrippian stages of the Holocene, ice wedges grew syngenetically in sandy deposits with gravel in the Chara River valley. The variations of δ18O values in the ice wedges are about 8‰, from –25.5‰ to –18.8‰. Based on the stable isotope composition of ice wedges, paleotemperature reconstructions revealed that the mean January temperature was as low as –38°C during the coldest periods of the early half of the Holocene and as high as –28°C during the warmer periods.
{"title":"EARLY HOLOCENE OXYGEN ISOTOPE CHRONOLOGIES (11,267–6420 CAL BP) FROM ICE WEDGE AT CHARA, TRANSBAIKALIA","authors":"Yurij K Vasil’chuk, Alla C Vasil’chuk, Nadine A Budantseva, Alexander P Ginzburg, Igor V Tokarev, Jessica Yu Vasil’chuk","doi":"10.1017/rdc.2024.34","DOIUrl":"https://doi.org/10.1017/rdc.2024.34","url":null,"abstract":"Accelerator mass spectrometry radiocarbon (AMS <jats:sup>14</jats:sup>C) dating was used for determining the age of wedge ice. It has been found that between 11,270 and 6420 cal BP, or the Greenlandian and Northgrippian stages of the Holocene, ice wedges grew syngenetically in sandy deposits with gravel in the Chara River valley. The variations of δ<jats:sup>18</jats:sup>O values in the ice wedges are about 8‰, from –25.5‰ to –18.8‰. Based on the stable isotope composition of ice wedges, paleotemperature reconstructions revealed that the mean January temperature was as low as –38°C during the coldest periods of the early half of the Holocene and as high as –28°C during the warmer periods.","PeriodicalId":21020,"journal":{"name":"Radiocarbon","volume":"48 1","pages":""},"PeriodicalIF":8.3,"publicationDate":"2024-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140560130","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Massive ground ice found in the Barrow Permafrost Tunnel at 3–7 m depths from the surface has been interpreted as an ice wedge and used to reconstruct early Holocene environmental changes. To better understand the development of this ground ice, we conducted radiocarbon dating for 34 samples of plant remains from the massive ground ice and underlying sediment layer. A significantly large gap in the measured radiocarbon ages (more than 24 ka) between massive ice and the underlying sediment layer throughout the tunnel profile suggested at least two possibilities. One is that the lower and older sediment layer had thrust upwards at the boundary between intruding ice wedge and adjacent sediment, and the growing ice had pushed the sediment sideways. Another is that erosional events had removed surface materials at about 12–36 ka BP (14–41 cal ka BP) before the overlaying sediment layer with massive ground ice developed. The overall distribution of radiocarbon ages from the massive ice supported the ice-wedge hypothesis as a formation mechanism, although our results showed several age inversions and large fluctuations. Dating of densely spaced samples revealed two ground-ice regions with similar ages around 11–11.5 and 10–10.5 ka BP divided by a relatively narrow region of transitional ages along the tunnel long-axis. This distribution may be explained by a possible misalignment between the sampling direction and the ice-wedge growth line or by intermittent ice growth with repeated cracking at more random locations than the classic ice-wedge growth model suggested.
在巴罗永久冻土隧道(Barrow Permafrost Tunnel)距地表 3-7 米深处发现的大量地冰被解释为冰楔,并被用来重建全新世早期的环境变化。为了更好地了解这些地冰的发展过程,我们对大量地冰和底层沉积层中的 34 个植物遗骸样本进行了放射性碳测年。在整个隧道剖面中,大块冰和下层沉积层之间的放射性碳年代测定结果差距很大(超过 24 ka),这至少说明了两种可能性。一种可能是,下层较早的沉积层在侵入的冰楔与相邻沉积层之间的边界向上推移,不断增长的冰将沉积层推向一侧。另一种可能是,大约在公元前 12-36 ka 年(公元前 14-41 cal ka 年),侵蚀事件清除了地表物质,然后才形成了覆盖着大量地表冰的沉积层。块冰的放射性碳年龄的总体分布支持冰缘假说的形成机制,尽管我们的结果显示出一些年龄倒置和较大的波动。对间隔密集的样本进行的年代测定显示,在 11-11.5 ka BP 和 10-10.5 ka BP 附近有两个年代相近的地冰区域,而沿隧道长轴则有一个相对狭窄的年代过渡区域。这种分布的原因可能是取样方向与冰缘生长线之间可能存在错位,或者是冰的间歇性生长,在比经典的冰缘生长模型更随机的位置反复开裂。
{"title":"RADIOCARBON AGES OF PLANT REMAINS IN MASSIVE GROUND ICE AND UNDERLYING SEDIMENTS OF THE BARROW PERMAFROST TUNNEL, ALASKA","authors":"Go Iwahana, Masao Uchida, Kazuho Horiuchi, Jody Deming, Hajo Eicken, Hiroshi Ohno, Kanako Mantoku, Toshiyuki Kobayashi, Kazuyuki Saito","doi":"10.1017/rdc.2024.25","DOIUrl":"https://doi.org/10.1017/rdc.2024.25","url":null,"abstract":"Massive ground ice found in the Barrow Permafrost Tunnel at 3–7 m depths from the surface has been interpreted as an ice wedge and used to reconstruct early Holocene environmental changes. To better understand the development of this ground ice, we conducted radiocarbon dating for 34 samples of plant remains from the massive ground ice and underlying sediment layer. A significantly large gap in the measured radiocarbon ages (more than 24 ka) between massive ice and the underlying sediment layer throughout the tunnel profile suggested at least two possibilities. One is that the lower and older sediment layer had thrust upwards at the boundary between intruding ice wedge and adjacent sediment, and the growing ice had pushed the sediment sideways. Another is that erosional events had removed surface materials at about 12–36 ka BP (14–41 cal ka BP) before the overlaying sediment layer with massive ground ice developed. The overall distribution of radiocarbon ages from the massive ice supported the ice-wedge hypothesis as a formation mechanism, although our results showed several age inversions and large fluctuations. Dating of densely spaced samples revealed two ground-ice regions with similar ages around 11–11.5 and 10–10.5 ka BP divided by a relatively narrow region of transitional ages along the tunnel long-axis. This distribution may be explained by a possible misalignment between the sampling direction and the ice-wedge growth line or by intermittent ice growth with repeated cracking at more random locations than the classic ice-wedge growth model suggested.","PeriodicalId":21020,"journal":{"name":"Radiocarbon","volume":"10 22 1","pages":""},"PeriodicalIF":8.3,"publicationDate":"2024-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140560348","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Based on the study of the primary documentation related to the excavations carried out by Eurico Miller in the 1970s at Abrigo do Sol, Mato Grosso (Brazil), we propose a new reading of the stratigraphic and chronological information obtained from this rock shelter. Despite the apparent incongruity in the chrono-stratigraphic distribution of published dates, a detailed examination of the stratigraphy and field notes allowed us to identify a chronometric sequence with regular distribution between the Middle Holocene and the Late Pleistocene periods for the Abrigo do Sol site. We present here the original documents related to radiocarbon dating and their analysis. We finally show the implications of this study for understanding this site and the discussions related to the ancient settlements of the Amazon forest.
根据对尤里科-米勒(Eurico Miller)于 20 世纪 70 年代在巴西马托格罗索州阿布里戈-多索尔(Abrigo do Sol)进行发掘的相关原始文献的研究,我们对从该岩洞获得的地层学和年代学信息提出了新的解读。尽管已公布日期的年代-地层分布明显不一致,但通过对地层和实地记录的详细研究,我们确定了 Abrigo do Sol 遗址的年代序列,其在全新世中期和更新世晚期之间的分布是有规律的。我们在此介绍与放射性碳测年有关的原始文件及其分析。最后,我们展示了这项研究对于了解该遗址以及与亚马逊森林古代定居点相关的讨论的意义。
{"title":"NEW PERSPECTIVES ON OLD MATTERS: A REVIEW OF ARCHAEOLOGICAL AND CHRONOMETRIC DATA FROM ABRIGO DO SOL (MATO GROSSO, BRAZIL)","authors":"Simon-Pierre Gilson, Lucas Bueno","doi":"10.1017/rdc.2024.30","DOIUrl":"https://doi.org/10.1017/rdc.2024.30","url":null,"abstract":"<p>Based on the study of the primary documentation related to the excavations carried out by Eurico Miller in the 1970s at Abrigo do Sol, Mato Grosso (Brazil), we propose a new reading of the stratigraphic and chronological information obtained from this rock shelter. Despite the apparent incongruity in the chrono-stratigraphic distribution of published dates, a detailed examination of the stratigraphy and field notes allowed us to identify a chronometric sequence with regular distribution between the Middle Holocene and the Late Pleistocene periods for the Abrigo do Sol site. We present here the original documents related to radiocarbon dating and their analysis. We finally show the implications of this study for understanding this site and the discussions related to the ancient settlements of the Amazon forest.</p>","PeriodicalId":21020,"journal":{"name":"Radiocarbon","volume":"249 1","pages":""},"PeriodicalIF":8.3,"publicationDate":"2024-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140559921","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Tamara Blagojević, Marko Porčić, Sofija Stefanović
The intensity of changes in the population dynamics of the Early Neolithic (ca. 6250–5300 cal BC) communities in the Central Balkans was addressed by estimating the growth rate values. The Bayesian approach (Crema and Shoda 2021) of estimating intrinsic growth rates by fitting different models of population growth was applied to radiocarbon dates from the Early Neolithic sites in Serbia. We explored two possible episodes of population growth based on the results of the population dynamics reconstruction using the summed calibrated radiocarbon probability distributions (SPD) method. The results have shown that, within the first episode of growth, the intrinsic growth rate mean values are higher than the estimated continental average (between 1% and 2%). The results indicate a sudden and fast rise in population size, possibly due to the influx of the new population settling in the region at the beginning of the Neolithic. Lower values for the second episode could indicate more gradual population growth due to the mechanisms associated with the Neolithic Demographic Transition and the rise in fertility.
{"title":"ADDRESSING THE INTENSITY OF CHANGES IN THE PREHISTORIC POPULATION DYNAMICS: POPULATION GROWTH RATE ESTIMATIONS IN THE CENTRAL BALKANS EARLY NEOLITHIC","authors":"Tamara Blagojević, Marko Porčić, Sofija Stefanović","doi":"10.1017/rdc.2024.23","DOIUrl":"https://doi.org/10.1017/rdc.2024.23","url":null,"abstract":"The intensity of changes in the population dynamics of the Early Neolithic (ca. 6250–5300 cal BC) communities in the Central Balkans was addressed by estimating the growth rate values. The Bayesian approach (Crema and Shoda 2021) of estimating intrinsic growth rates by fitting different models of population growth was applied to radiocarbon dates from the Early Neolithic sites in Serbia. We explored two possible episodes of population growth based on the results of the population dynamics reconstruction using the summed calibrated radiocarbon probability distributions (SPD) method. The results have shown that, within the first episode of growth, the intrinsic growth rate mean values are higher than the estimated continental average (between 1% and 2%). The results indicate a sudden and fast rise in population size, possibly due to the influx of the new population settling in the region at the beginning of the Neolithic. Lower values for the second episode could indicate more gradual population growth due to the mechanisms associated with the Neolithic Demographic Transition and the rise in fertility.","PeriodicalId":21020,"journal":{"name":"Radiocarbon","volume":"25 1","pages":""},"PeriodicalIF":8.3,"publicationDate":"2024-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140560698","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Cathodes with recessed sample surfaces have several benefits in cesium sputter ion sources, including higher output, more efficient use of sample material, and improved focusing of the extracted ion beam. However, the Ionplus MICADAS uses cathodes with a graphite surface that is essentially flush with the sample holder. To evaluate the performance of recessed graphite with the MICADAS and determine the optimal surface depth, we tested four different depths, including the standard (flush) pressing method, 0.5 mm, 1.0 mm, and 1.5 mm. We found that recessed depths of 1.0 and 1.5 mm resulted in 20% higher ion beam current compared to the standard method under the same source conditions. The results are consistent with the beam produced from the recessed targets being more narrowly focused with a lower emittance, resulting in better transmission through the accelerator. Small graphite samples (200 µg C) with recessed surfaces produced higher currents for longer, leading to a 2–3× increase in sample ionization efficiency. Additionally, there was some evidence that isotopic ratio measurements of recessed samples were more stable over time. Overall, samples recessed to 1 mm depth offered numerous advantages over the standard pressing method and we have subsequently started pressing all MICADAS graphite using this approach.
{"title":"IMPROVING IONPLUS MICADAS PERFORMANCE WITH RECESSED GRAPHITE","authors":"Taylor A B Broek, Mark L Roberts","doi":"10.1017/rdc.2024.36","DOIUrl":"https://doi.org/10.1017/rdc.2024.36","url":null,"abstract":"Cathodes with recessed sample surfaces have several benefits in cesium sputter ion sources, including higher output, more efficient use of sample material, and improved focusing of the extracted ion beam. However, the Ionplus MICADAS uses cathodes with a graphite surface that is essentially flush with the sample holder. To evaluate the performance of recessed graphite with the MICADAS and determine the optimal surface depth, we tested four different depths, including the standard (flush) pressing method, 0.5 mm, 1.0 mm, and 1.5 mm. We found that recessed depths of 1.0 and 1.5 mm resulted in 20% higher ion beam current compared to the standard method under the same source conditions. The results are consistent with the beam produced from the recessed targets being more narrowly focused with a lower emittance, resulting in better transmission through the accelerator. Small graphite samples (200 µg C) with recessed surfaces produced higher currents for longer, leading to a 2–3× increase in sample ionization efficiency. Additionally, there was some evidence that isotopic ratio measurements of recessed samples were more stable over time. Overall, samples recessed to 1 mm depth offered numerous advantages over the standard pressing method and we have subsequently started pressing all MICADAS graphite using this approach.","PeriodicalId":21020,"journal":{"name":"Radiocarbon","volume":"24 1","pages":""},"PeriodicalIF":8.3,"publicationDate":"2024-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140560365","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Stephen E Schwartz, Quan Hua, David E Andrews, Ralph F Keeling, Scott J Lehman, Jocelyn C Turnbull, Paula J Reimer, John B Miller, Harro A J Meijer
Observations of radiocarbon (14C) in Earth’s atmosphere and other carbon reservoirs are important to quantify exchanges of CO2 between reservoirs. The amount of 14C is commonly reported in the so-called Delta notation, i.e., Δ14C, the decay- and fractionation-corrected departure of the ratio of 14C to total C from that ratio in an absolute international standard; this Delta notation permits direct comparison of 14C/C ratios in the several reservoirs. However, as Δ14C of atmospheric CO2, Δ14CO2 is based on the ratio of 14CO2 to total atmospheric CO2, its value can and does change not just because of change in the amount of atmospheric14CO2 but also because of change in the amount of total atmospheric CO2, complicating ascription of change in Δ14CO2 to change in one or the other quantity. Here we suggest that presentation of atmospheric 14CO2 amount as mole fraction relative to dry air (moles of 14CO2 per moles of dry air in Earth’s atmosphere), or as moles or molecules of 14CO2 in Earth’s atmosphere, all readily calculated from Δ14CO2 and the amount of atmospheric CO2 (with slight dependence on δ13CO2), complements presentation only as Δ14CO2, and can provide valuable insight into the evolving budget and distribution of atmospheric 14CO2.
对地球大气层和其他碳库中放射性碳(14C)的观测对于量化碳库之间的二氧化碳交换非常重要。14C 的数量通常用所谓的 Delta 符号来报告,即 Δ14C,即经过衰变和分馏校正的 14C 与总 C 之比偏离绝对国际标准的比率;这种 Delta 符号允许直接比较几个储层中的 14C/C 比率。然而,由于大气中 CO2 的 Δ14C (Δ14CO2)是基于 14CO2 与大气中 CO2 总量之比,因此其值不仅会因为大气中 14CO2 量的变化而变化,而且也会因为大气中 CO2 总量的变化而变化,这就使得将 Δ14CO2 的变化归因于其中一个或另一个量的变化变得更加复杂。在此,我们建议将大气中的 14CO2 量表述为相对于干燥空气的摩尔分数(地球大气中每摩尔干燥空气中 14CO2 的摩尔数),或表述为地球大气中 14CO2 的摩尔数或分子数,所有这些都很容易从 Δ14CO2 和大气中 CO2 的数量(与 δ13CO2 稍有关系)计算出来,这是对仅表述为 Δ14CO2 的表述的补充,可以为了解大气中 14CO2 不断变化的预算和分布提供有价值的信息。
{"title":"DISCUSSION: PRESENTATION OF ATMOSPHERIC 14CO2 DATA","authors":"Stephen E Schwartz, Quan Hua, David E Andrews, Ralph F Keeling, Scott J Lehman, Jocelyn C Turnbull, Paula J Reimer, John B Miller, Harro A J Meijer","doi":"10.1017/rdc.2024.27","DOIUrl":"https://doi.org/10.1017/rdc.2024.27","url":null,"abstract":"<p>Observations of radiocarbon (<span>14</span>C) in Earth’s atmosphere and other carbon reservoirs are important to quantify exchanges of CO<span>2</span> between reservoirs. The amount of <span>14</span>C is commonly reported in the so-called Delta notation, i.e., Δ<span>14</span>C, the decay- and fractionation-corrected departure of the ratio of <span>14</span>C to total C from that ratio in an absolute international standard; this Delta notation permits direct comparison of <span>14</span>C/C ratios in the several reservoirs. However, as Δ<span>14</span>C of atmospheric CO<span>2</span>, Δ<span>14</span>CO<span>2</span> is based on the ratio of <span>14</span>CO<span>2</span> to total atmospheric CO<span>2</span>, its value can and does change not just because of change in the amount of atmospheric<span>14</span>CO<span>2</span> but also because of change in the amount of total atmospheric CO<span>2</span>, complicating ascription of change in Δ<span>14</span>CO<span>2</span> to change in one or the other quantity. Here we suggest that presentation of atmospheric <span>14</span>CO<span>2</span> amount as mole fraction relative to dry air (moles of <span>14</span>CO<span>2</span> per moles of dry air in Earth’s atmosphere), or as moles or molecules of <span>14</span>CO<span>2</span> in Earth’s atmosphere, all readily calculated from Δ<span>14</span>CO<span>2</span> and the amount of atmospheric CO<span>2</span> (with slight dependence on δ<span>13</span>CO<span>2</span>), complements presentation only as Δ<span>14</span>CO<span>2</span>, and can provide valuable insight into the evolving budget and distribution of atmospheric <span>14</span>CO<span>2</span>.</p>","PeriodicalId":21020,"journal":{"name":"Radiocarbon","volume":"86 1","pages":""},"PeriodicalIF":8.3,"publicationDate":"2024-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140302806","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}