Radiocarbon Calibrated ages of surface marine sediments at the Southeast Pacific (methods/regional reservoir ages/results)

The radiocarbon ages (14C) obtained from surface sediment samples at the South East Pacific were measured in mixed upper thermocline planktonic foraminifera (MUTPF), Mixed shallow infaunal benthic foraminifera (MBF) and monospecific benthic foraminifera. All the foraminifera selected for the analysis were Benga-Rose unstained foraminifera. This data set (raw data, radiocarbon ages, 14C) is storage by PANGAEA Data Publisher for Earth & Environmental Science. Radiocarbon ages of surface marine sediments at the South East Pacific (14CSS_SEP_version1). To obtain sediment surface calendar ages, planktic and benthic foraminifera radiocarbon ages were corrected by different regional marine surface reservoir ages expressed as R (R = 14C from the ocean - 14C from the atmosphere), which represents the deviation from the SHCal20 curve at a given time. These R values account for four different upwelling regimes in the South East Pacific: i) a northern upwelling regime between Lima, Peru and Coquimbo, Chile (~11-30 ºS), characterized by permanent upwelling, with an estimated modern R of 505 ± 135 years; ii) a central upwelling zone between Coquimbo and Curicó, Chile (~30-35 °S) were upwelling is permanent but weaker in austral winter, with an estimated modern R of 460 ± 100 years; iii) a southern upwelling regime between Curicó and Valdivia, Chile (~35-40 ºS), where upwelling is seasonal but relatively high, with an estimated modern R of 510 ± 25 years; iv) and finally a north Patagonian zone (>40 ºS) in which no upwelling occurs, with an estimated modern R of 450 ± 55 years. The R values for each of these zones were calculated as the mean modern R estimated based on Merino et al. (2018). Samples with 14C age older than 1000 yrs BP were corrected by an R estimation by Zhao and Keigwin (2018) or Fontugne et al. (2004) in the northern upwelling zone, by Merino et al. (2018) in the central and southern upwelling zone, and by Siani et al. (2013) in the north Patagonia upwelling zone. For PG4-18 (142 m, dated by mixed benthic foraminifera) due the not availability of published R estimations in these latitudes and water depth, a R equal to the modern estimated by Merino et al. (2018) was applied. For the deep benthic foraminifera, an additional correction was made to account for the benthic-planktic foraminifera 14C age difference, which was estimated at 500 ± 250 years. The correction was estimated as the mean benthic-planktic 14C age in core 22SL retrieved nearby site PG4-23 (De Pol-Holz et al., 2010). The planktonic and benthic foraminifera radiocarbon ages were then calibrated by the SHCal20 curve (Hogg et al., 2020) using the python library iosacal 0.6.0 (Costa et al., 2022, https://pypi.org/project/iosacal/). All calibrated ages are reported as years Before Present (BP, considering present the year 1950). We considered foraminifera with radiocarbon ages >1950 (Post-radiocarbon boom period) or samples with radiocarbon ages smaller than the average of the different regional modern reservoir ages calculated for the SEP as recent. In this ZENODO chanel you will find 1) R values (regional and mobile by time) for the South East Pacific 2) Radiocarbon calibrated ages data for 14CSS_SEP_version1 (using Merino et al., 2018 original R calculations based in Marine13 radiocarbon age calibration curve) 3) Radiocarbon calibrated ages data for 14CSS_SEP_version1 (using Merino et al., 2018 recalculated R based in SHCal20 radiocarbon age calibration curve) 3) Python Code developed for calculate calibrated radiocarbon ages based in regional and mobile R https://github.com/Paleobiogeochemistry/calibrar14ages_surfacesediments本数据集针对东南太平洋表层沉积物样品开展了放射性碳（14C）年龄测试，测试对象涵盖混合上层跃层浮游有孔虫（MUTPF）、混合浅栖底栖有孔虫（MBF）以及单种底栖有孔虫。所有用于分析的有孔虫均为Benga-Rose未染色有孔虫。本数据集（含原始数据、放射性碳年龄数据，即14C数据）由地球与环境科学数据出版平台PANGAEA进行存储，数据集名称为东南太平洋海洋表层沉积物放射性碳年龄数据集（14CSS_SEP_version1）。 为获取沉积物表层的日历年龄，研究人员基于区域海洋表层储层年龄R（R=海洋14C活度-大气14C活度）对浮游及底栖有孔虫的放射性碳年龄进行校正，该参数代表特定时间下相对于SHCal20校正曲线的偏移量。东南太平洋存在四类不同的上升流体系，对应的区域R值均基于Merino等人（2018）的现代R均值估算得到： 1. 北部上升流区：位于秘鲁利马与智利科金博之间（约11°S~30°S），为常年上升流区，现代R估算值为505±135年； 2. 中部上升流区：位于智利科金博与库里科之间（约30°S~35°S），上升流常年存在但在南半球冬季强度较弱，现代R估算值为460±100年； 3. 南部上升流区：位于智利库里科与瓦尔迪维亚之间（约35°S~40°S），上升流为季节性且强度较高，现代R估算值为510±25年； 4. 北巴塔哥尼亚区：位于南纬40°以南，无上升流活动，现代R估算值为450±55年。 针对年龄大于1000年BP的样品，北部上升流区采用Zhao与Keigwin（2018）或Fontugne等人（2004）的R估算值进行校正，中部与南部上升流区采用Merino等人（2018）的R估算值，北巴塔哥尼亚区则采用Siani等人（2013）的R估算值。对于PG4-18站位（水深142m，采用混合底栖有孔虫定年），由于该纬度与水深范围内尚无已发表的R估算结果，故采用Merino等人（2018）提出的现代R值进行校正。针对深水底栖有孔虫，需额外校正底栖-浮游有孔虫间的放射性碳年龄差，该差值经估算为500±250年，校正值基于PG4-23站位附近岩芯22SL中测得的底栖-浮游有孔虫放射性碳年龄均值（De Pol-Holz等人，2010）。 随后，研究人员采用Python库iosacal 0.6.0（Costa等人，2022，https://pypi.org/project/iosacal/），基于SHCal20校正曲线（Hogg等人，2020）对浮游及底栖有孔虫的放射性碳年龄进行校正。所有校正后的年龄均以“距今（BP，以1950年为基准年）”的形式报告。本研究将放射性碳年龄大于1950年（后放射性碳爆发期）或小于东南太平洋区域现代储层年龄均值的样品定义为近代样品。 本ZENODO仓库包含以下内容： 1. 东南太平洋区域随时间变化的R值（区域储层年龄参数）； 2. 基于Merino等人（2018）原始R计算方案（采用Marine13放射性碳年龄校正曲线）的14CSS_SEP_version1数据集放射性碳校正年龄数据； 3. 基于Merino等人（2018）重新计算的R值（采用SHCal20放射性碳年龄校正曲线）的14CSS_SEP_version1数据集放射性碳校正年龄数据； 4. 用于基于区域随时间变化的R值计算放射性碳校正年龄的Python代码：https://github.com/Paleobiogeochemistry/calibrar14ages_surfacesediments