Stable isotope data for Sturgeon and Paddlefish specimens, Leaf Mining Data, and Yearling Fish Sizes from the Tanis Location in the Hell Creek Formation of North Dakota (U.S.A.): Isotope Data

Fossil specimens were obtained via field work over several years (2014-2021) at the Tanis site, in North Dakota, U.S.A. The specimens include: i) Sub-samples of sturgeon spines and paddlefish dentaries which were epoxy impregnated and sectioned using facilities at Florida Atlantic University. In 2024 a set of these samples were analyzed for stable isotope zonation (carbon and oxygen) at the Department of Earth Sciences, Durham University (UK). A customized micromill setup (computer-controlled ESI/New Wave Micromill with a 500 micron tungsten carbide drill bit) was used to sample fossil sturgeon and paddlefish specimens. Powders were removed by micro-spatula and weighed, with location of drill trace relative to outermost specimen edge logged via high resolution camera imaging. Powders were then analyzed by a Thermo-Finnigan (now Thermo Fisher Scientific) MAT 253 Isotope Ratio Mass Spectrometer into which CO2 was introduced through a Gasbench II device (external precision of about 0.05–0.10‰). Fossil fish powder samples were dissolved in 10 drops of orthophosphoric acid (H3PO4) under a helium (grade 5) atmosphere in exetainer vials. The solution was left to digest at 50 °C for two hours. The resultant gas mixture (CO2 and He) was introduced to a gas chromatographic column to isolate CO2. After passing a second water trap the CO2 was admitted to the mass spectrometer. Each sample run measured isotope ratios in 16 or 17 fossil fish powders and multiple replicates of four reference standards: 1) IAEA (International Atomic Energy Agency) international reference material CO1 (marble), 2) IAEA reference material LS VEC (lithium carbonate), 3) Durham internal standard DCS01 (calcite), and 4) a Durham internal standard DOBINS (equine hydroxyapatite). 13C/12C and 18O/16O ratios are reported as d values (‰ deviations) relative to Vienna PeeDee Belemnite (VPDB). ii) Fossil angiosperm leaves from the time-synchronous Chicxulub Event Deposit, sedimentary units 2a-c, were analyzed for the presence of insect leaf-mining traces, and a tally of trace absent vs. trace present specimens recorded. iii) Fossils of sub-yearling (young-of-year) fish from Unit 2a were also examined. Here. these were identified as members of one of three groups: sturgeon, paddlefish, or Amiidae, and their lengths and orientations recorded. iv) Synchrotron Rapid Scanning-X-ray Fluorescence (SRS-XRF) imaging was performed in this study at wiggler beamline 6-2 (SSRL). Incident beam energy for the experiments was set at 3.15 keV (flux ~10^9 photons-1) for Low-Z mapping and specimens were analysed within a He-purged chamber. Experiments utilized a beam diameter of either 50 or 100 µm, defined by a pinhole. A four-element Vortex ME4 silicon drift detector was used to detect fluoresced X-rays.

本数据集的化石标本采集自美国北达科他州塔尼斯（Tanis）遗址，野外工作于2014至2021年间开展，历时7年。标本包含以下四类：
i) 鲟鱼脊柱与白鲟齿骨的子样本：该类样本经环氧树脂浸渍后，依托佛罗里达大西洋大学（Florida Atlantic University）的设备完成切片。2024年，英国杜伦大学（Durham University）地球科学系对其中一组样本开展了稳定同位素分带（碳、氧同位素）分析。实验采用定制化微铣装置（计算机控制的ESI/New Wave微铣机，配备500微米碳化钨钻头）对鲟鱼与白鲟化石样本进行取样。通过显微刮刀获取粉末并称量，利用高分辨率相机成像记录钻孔痕迹相对于样本最外缘的位置。随后将粉末引入赛默飞世尔科技（原Thermo-Finnigan）MAT 253同位素比率质谱仪进行分析，该仪器通过Gasbench II装置导入二氧化碳（CO₂），外部精度约为0.05~0.10‰。将化石鱼类粉末样品置于氦气（5级）氛围下的Exetainer样品瓶中，加入10滴正磷酸（H₃PO₄）进行溶解，随后在50℃下消解2小时。生成的混合气体（CO₂与He）先通过气相色谱柱分离CO₂，再经过二级除水阱后导入质谱仪。每轮实验同时分析16或17份化石鱼类粉末样本，以及4种参考标准品的多组平行样：1) 国际原子能机构（IAEA）国际参考物质CO1（大理石）；2) 国际原子能机构参考物质LS VEC（碳酸锂）；3) 杜伦大学内部标准DCS01（方解石）；4) 杜伦大学内部标准DOBINS（马羟基磷灰石）。碳同位素比值¹³C/¹²C与氧同位素比值¹⁸O/¹⁶O以相对于维也纳佩德贝lemnite（VPDB）的δ值（以‰为单位的偏差）形式报告。
ii) 同时期希克苏鲁伯事件沉积层（沉积单元2a-c）中的被子植物叶片化石：对其开展昆虫潜叶痕迹检测，并记录有无潜叶痕迹的标本数量。
iii) 沉积单元2a中的亚龄（当年生）鱼类化石：对其进行分类鉴定，归为鲟鱼、白鲟或弓鳍鱼科（Amiidae）三类之一，并记录其体长与朝向。
iv) 同步辐射快速扫描X射线荧光（SRS-XRF）成像：本研究在斯坦福同步辐射光源（SSRL）的摇摆器光束线6-2开展相关实验。低原子序数元素成像实验的入射束能量设置为3.15 keV（通量约10⁹光子·s⁻¹），样本置于氦气吹扫腔中进行分析。实验采用针孔光阑定义光束直径，可选50 µm或100 µm。使用四单元Vortex ME4硅漂移探测器检测荧光X射线。