EAR-PF: Vertebrate Bioapatite Fossilization: Multi-proxy Investigation of Biogenic Preservation and Diagenesis

塞琳娜·苏亚雷斯博士被授予美国国家科学基金会地球科学博士后奖学金，在爱达荷州的博伊西州立大学开展研究和教育计划。苏亚雷斯博士将使用多种工具研究骨骼石化过程中发生的化学和物理变化。这些工具包括稳定同位素地球化学、微量元素(TE)地球化学和拉曼光谱，这些骨骼化石是从全新世到上新世在细粒氧化的陆地环境中化石。这项研究将通过两个主要的研究计划来完成。首先，将对TE分区、胶原保存和骨磷灰石结晶度进行鉴定，以确定骨中摄取的机制。这将通过激光消融TE和元素碳的电感耦合质谱学(13C识别胶原的存在)和拉曼光谱来识别胶原分布和磷灰石结晶度来实现。以前的研究表明，在大样本范围内，胶原保存与磷灰石结晶度/TE浓度呈负相关；但还没有研究分析原位胶原在骨中的分布并将其与TE扩散模型相关联。其次，碳和氧同位素分区的鉴定将与第一个研究计划中对骨骼进行分析时创建的微量元素图相关联。TE浓度分布和拉曼光谱将被用作同位素分析的采样指南。苏亚雷斯博士将对被确定为成岩改变的骨骼(磷酸盐和碳酸盐成分)的同位素组成与那些看起来原始的骨骼进行比较。具有短扩散时间(陡峭的浓度梯度)的骨骼被认为是为了保存生物同位素，而长扩散时间将保留成岩信号。通过评估这些结果，我们可以确定什么摄取机制、沉积环境和时间限制最有可能保存骨中用于解释古生态学和古气候学的生物起源信号。史前和考古脊椎动物遗骸是研究人员用来了解过去气候和环境的基本工具，这些气候和环境被用来模拟未来的气候变化。它们还被用来推断古生态信息，如古饮食和迁徙。脊椎动物生物磷灰石(骨、牙釉质、牙本质和牙骨质)及其保存下来的有机部分(即胶原)的使用需要详细了解石化过程(即将生物材料化学和物理变化为在地球表面稳定的形式)。为了更好地了解脊椎动物的石化过程，已经进行了许多研究，但大多数研究都集中在单一类型的分析来研究石化，而很少有研究使用多种地球化学分析来研究石化。这项拟议的研究打算使用多种原位地球化学分析来研究骨骼的保存和成岩作用。由于微量元素是一种拟议的法医工具，用于识别非法从公共土地上移走的脊椎动物化石，因此拟议的研究直接影响这种技术的有效性。苏亚雷斯博士将积极参与北卡罗来纳州立大学的路易斯·斯托克斯少数民族参与联盟(LSAMP)计划。她将担任LSAMP拉美裔本科生的导师，该本科生将从哈格曼化石床进行稳定同位素古生态学研究，苏亚雷斯博士将作为演讲者参加LSAMP项目。通过参加LSAMP项目，苏亚雷斯希望成为那些可能不认为自己是地球科学家的学生的榜样。

Dr. Celina Suarez has been awarded an NSF Earth Sciences Postdoctoral Fellowship to carry out research and education plans at Boise State University in Idaho. Dr. Suarez will investigate the chemical and physical changes that occur during bone fossilization using multiple tools. These tools include stable isotope geochemistry, trace element (TE) geochemistry, and Raman spectroscopy of bone fossilized in fine-grained oxygenated terrestrial settings from the Holocene to Pliocene. This research will be accomplished through two main research plans. First, identification of TE zoning, collagen preservation, and bone apatite crystallinity will be done to determine uptake mechanisms in bone. This will be accomplished through laser ablation inductively coupled mass spectrometry of both TE and elemental carbon (13C to identify presence of collagen) and Raman spectroscopy to identify collagen distribution and apatite crystallinity. Previous research suggests inverse correlation between collagen preservation and apatite crystallinity/ TE concentration on a bulk sample scale; but no studies have analyzed the distribution of in-situ collagen within the bone and associated it with TE diffusion models. Second, identification of C and O-isotopic zoning will be correlated to the trace element maps created in the analysis of bones from the first research plan. TE concentration profiles and Raman spectra will be used as a guide to sampling for isotopic analysis. Dr. Suarez will compare isotopic composition of bones (phosphate and carbonate components) that were determined to be diagenetically altered with those that appeared pristine. Bones with profiles suggesting short diffusion times (steep-concentration gradients) are hypothesized to preserve biogenic isotopes while bones will long diffusion times will preserve diagenetic signals. By evaluating these results, we can determine what uptake mechanisms, depositional environments, and time constraints most likely preserve biogenic signals in bone that are used to interpret paleoecology and paleoclimatology. Prehistoric and archeologic vertebrate remains are essential tools used by researchers to understand past climates and environments that are used to model future climate change. They are also used to infer paleoecologic information such as paleodiet and migration. The use of vertebrate bioapatites (bone, enamel, dentine, and cementum) as well as its preserved organic fraction (namely collagen) requires a detailed understanding of the fossilization process (i.e. chemical and physical alterations to biologic material into a form stable at the earth's surface). A number of studies have been conducted to better understand the fossilization process of vertebrates, however most studies focus on a single type of analysis to investigate fossilization and few studies use multiple geochemical analyses to investigate fossilization. The proposed research intends to use multiple in-situ geochemical analyses to investigate both preservation and diagenesis of bones. Since trace elements are a proposed forensic tool to identify illegally removed fossil vertebrates from public lands, the proposed research directly impacts the validity of such a technique. Dr. Suarez will be actively engaged in the Louis Stokes Alliance for Minority Participation (LSAMP) program at BSU. She will be acting as a mentor to a LSAMP Hispanic undergraduate student that will be conducting research on stable isotope paleoecology from Hagerman Fossil Beds, and Dr. Suarez will participate as a speaker in the LSAMP program. Through her participation in the LSAMP program, Dr. Suarez expects to be a role model for students that may not see themselves as Geoscientists.