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.
The main objective of this study was to identify chemical and physical changes that occur to bone during the fossilization process. To do this, I analyzed trace element (primarily trace metals such as uranium and rare earth elements) to track diagenetic alteration to original bioapatite from the surface to the interior of bones. I also monitored the changes in molecules within the bone by using infrared spectroscopy. Finally, to look at changes in the isotopic composition of bone, (which can be used to determine aspects of paleoclimate) I analyzed the oxygen isotopic composition of the phosphate component of bone and the carbon and oxygen isotopic composition of carbonatethat substitutes for the phosphate protion of bone. I found that most bone is fossilized by a process of diffusion of diagenetic fluids into the bone and recrystallization of bone along the way. The fossilization front does have a limit based on the extent of recrystallization and the porosity of the surrounding matrix. Fossilization fluids can be traced using trace element concentrations profiles. When compared to IR spectroscopy, we see that locations of high trace element concentration also correspond to a loss of organics and water within the bone and to the loss of the carbonate molecule that substitutes for the OH portion of bone. This may also alter the isotopic composition of bone carbonate resulting in a loss of biogenic isotopic information. However, by analyzing trace element profiles through the cortex of bone and identifying the fossilization front, we can use the isotopic composition of bone (within the interior of the bone) to gain biogenic information via stable isotope analysis. This is important because often bone fragments can be the only mineral available to be analyzed for paleoclimate-proxy data. By understanding what type of bone is useable for this information, we can help to gain better knowledge of ancient ecosystems.
