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

Celina Suarez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，以及全新世至上新世细颗粒含氧陆地环境中骨骼化石的拉曼光谱。本研究将通过两个主要的研究计划来完成。首先，鉴定TE分区、胶原保存和骨磷灰石结晶度，以确定骨中的摄取机制。这将通过激光烧蚀电感耦合质谱分析TE和元素碳（13C以确定胶原的存在）和拉曼光谱来确定胶原的分布和磷灰石的结晶度来完成。先前的研究表明胶原保存与磷灰石结晶度/ TE浓度呈负相关；但没有研究分析骨内原位胶原蛋白的分布并将其与TE扩散模型联系起来。其次，C和o同位素分区的鉴定将与第一个研究计划中骨骼分析中创建的微量元素图相关联。TE浓度剖面和拉曼光谱将用作同位素分析取样的指南。苏亚雷斯博士将比较被确定为成岩作用改变的骨头的同位素组成（磷酸盐和碳酸盐成分）与那些看起来原始的骨头。假设扩散时间短（浓度梯度陡）的骨骼可以保存生物同位素，而扩散时间长的骨骼可以保存成岩信号。通过评估这些结果，我们可以确定哪些摄取机制、沉积环境和时间限制最有可能保存骨骼中的生物成因信号，这些信号用于解释古生态学和古气候学。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重要工具，用于模拟未来的气候变化。它们也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）及其保存的有机部分（即胶原蛋白）的使用需要详细了解石化过程（即生物材料在地球表面稳定形成的化学和物理变化）。为了更好地了解脊椎动物的石化过程，已经进行了大量的研究，但大多数研究都集中在单一类型的分析来研究化石，很少有研究使用多种地球化学分析来研究化石。本研究拟采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被提议的法医工具，用于识别从公共土地上非法移除的脊椎动物化石，因此拟议的研究直接影响了这种技术的有效性。苏亚雷斯博士将积极参与波士顿州立大学路易斯·斯托克斯少数民族参与联盟（LSAMP）项目。她将担任LSAMP西班牙裔本科生的导师，该本科生将对哈格曼化石床的稳定同位素古生态学进行研究，而苏亚雷斯博士将作为演讲者参加LSAMP项目。通过参加LSAMP项目，苏亚雷斯博士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.