The Geochemistry of Fossil Pigment Preservation

The Geochemistry of Fossil Pigment Preservation
Principal Investigator: R.A. Wogelius
Co-Investigators: P.L. Manning, W.I.Sellers, B.E. van Dongen

Summary
The University of Manchester Palaeontology and Geochemistry Groups, in collaboration with the Stanford Synchrotron Radiation Lightsource and other international partners, has recently shown that newly developed analytical techniques can resolve previously undetected chemical information about fossilized tissues. Several publications from this group (Wogelius et al., 2011; Edwards et al., 2011; Barden et al., 2011; Bergmann et al., 2010) have combined state-of-the-art synchrotron rapid scanning x-ray fluorescence imaging (SRS-XRF) with other sensitive techniques in order to show the chemical details of exceptionally preserved bones, feathers, skin, and a range of other soft tissues. Most importantly, this work has shown that patterns of copper distribution in the soft tissues of a number of fossils may successfully be used as biomarkers for the original distribution of eumelanin pigment. This finding was used to restore the eumelanin patterns within the oldest documented bird with a fully derived avian beak, the 120 million year old Confuciusornis sanctus. However, besides eumelanin, there are a number of other pigments that are important for life. In particular, chemical detection of phaeomelanin would provide critical information about the evolution of avian and mammalian species. Building on our successes with identifying and mapping the chemical residues of eumelanin and beta keratin, herein we propose an analytical and experimental plan to enhance our ability to detect and image key components of soft tissue. First of all we will perform a series of experiments with extant soft tissue so that we can monitor and determine the breakdown reactions of organic compounds as a function of host lithology, moisture content, and trace metal inventory. Secondly, we will complete an analytical programme, including SRS-XRF imaging, which will include these experimental run products as well as a series of time-stepped fossil samples of varying ages and host lithology so that we may build up a database which allows us to refine our general understanding of reaction paths during fossil degradation. Because the techniques we have developed are non-destructive we now have opened up the possibility for detailed analysis of extremely rare specimens which hold important information but cannot be destructively sampled. Finally, these experimental and analytical results from fossils and comparable extant species will be combined in order to answer several critically important questions in palaeontology, biology, and geochemistry, such as:
1) What are the key factors that control the breakdown kinetics of eumelanin, and thus what conditions favour exceptional preservation?
2) How does the presence of melanin affect the fossilisation process?
3) Can we reliably detect phaeomelanin as opposed to eumelanin, since the presence of this alternative form will improve our ability to resolve further aspects of fossil colour?
4) Because phaeomelanin is only found in birds and mammals, can it be used as a biomarker for endothermy and/or homeothermy?
5) Finally, can we reliably resolve the residues of other chemical pigments?


Project partners:

University of Nancy, CNRS, Prof. R. Michels
Feather degradation experiments
SLAC Linear Accelerator Center, Linac Coherent Light Source, Dr. U. Bergmann
SRS-XRF scans of large objects and x-ray spectroscopy
SLAC Linear Accelerator Center, Stanford Synchrotron Radiation Lightsource, Prof. C. Kao
SRS-XRF scans of large objects
DIAMOND Lightsource, Prof. Fred Mosselmans
XAS spectroscopy

1) Academia. This proposed research will benefit a wide circle of academia including not only Palaeontology and Geochemistry but also Biology, Physics, Analytical Chemistry, and Environmental Science. This is already discussed in the "Academic Beneficiaries" document, but essentially our work will have technological, conceptual, and theoretical impacts across a broad cross-section of academia.
2) Public sector. Our work has already prompted the USDOE investment in SRS-XRF technology at the SLAC National Accelerator Laboratory and our continued success at SSRL will inspire other facilities to do the same. What we learn has already had an impact on Museum curation methodologies and will continue to drive the development of new ways to handle precious specimens. Since what we are developing is non-destructive, we also envision that our work will increase Museum resource allocation for chemical analysis of rare specimens that are off limits for destructive analysis.
3) Business/Industry. What we have done so far has already impacted on the technological development of commercial FTIR systems and positively affected sales of FTIR instruments. We expect that industry will have increased demand for synchrotron access and that there will be parallel needs for technological development coming out of our work, in, for example, detectors and sample chambers. NERC has already selected our work for a REF Impact of Science Case study because what we learn about trace metal complexation informs us directly about the development of enhanced sequestration methods in land-based disposal of hazardous and radioactive wastes. Fossil specimens are the only cases of sequestration that have run for periods longer than the million years required for radwaste safety cases and as such we need to learn from these natural analogues. An improved understanding of melanin may have potential impacts on understanding melanogenesis and melanoma.
4) General public- cultural impact will be that of answering fundamental scientific questions that humans have pondered ever since Darwin, such as "What were the colors of past life?", and "How did birds become so colorful?" Our research has already had significant cultural impact.
For instance see the attached letter from Poppy Leeder at NERC detailing our contributions to Planet Earth Online (Roy Wogelius PE letter_NERC.pdf).
5) Direct impacts of staff development. PDRA and technician will be trained in state-of-the-art analytical methods which can be applied to any chemical problem that might arise in a range of business applications, from analyzing environmental toxins to screening manufactured components of Formula 1 cars.