This week I head to a
meeting in New York City. The meeting is being held at the Metropolitan Museum
of Art (The 'MET' to many). The Synchrotron Radiation in Art and Archaeology
(SR2A) meeting will explore the latest inroads for synchrotron-based research
to these two disciplines...with a few stray
palaeontological presentations to boot! My talk will try, in 30
minutes, to highlight some of the advances that the Stanford Synchrotron
Radiation Lightsouce (SSRL) and University of Manchester team have been working
on these past five years or more. 30 minutes is not a long time, so I will have
to either speak very quickly or just focus on some of our key
findings...I think the latter wins!
The talk
is entitled, 'Mapping Prehistoric Ghosts in the Synchrotron'
and like many such presentations is credited to key members of the team,
myself, Roy Wogelius, Bill Sellers and Uwe Bergmann.
For those of you who
want a sneak preview of the talk...here is my abstract:
Detailed chemical analyses have
never been completed on any fossil bird, such as the remains of Archaeopteryx and Confuciuornis santus,
despite their iconic status. Ideally such analyses would measure and map the
chemistry of bone, soft tissue structures, and characterize embedding matrix.
Mapping the fossil in situ would place constraints on mass
transfer between the enclosing matrix and preserved specimen(s), and therefore
aid in distinguishing taphonomic processes from original chemical zonation
remnant within the fossils themselves. Conventional nondestructive
analytical methods face serious problems in this case and most recent
technological advances have been targeted at developing nanometer-scale rather
than decimeter-scale capabilities. However, the recent development of
Synchrotron Rapid Scanning X-ray Fluorescence (SRS-XRF) at the Stanford
Synchrotron Radiation Lightsource (SSRL) now allows large paleontological and
archaeological specimens to be non-destructively analyzed and imaged using
major, minor, and trace element concentrations. Here we present high-resolution
elemental maps covering entire specimens of Archaeopteryx (Thermopolis)
and Confuciuornis, along with large sections of the enclosing
matrix for Silica, Phosphorus, Sulfur, Chlorine, Calcium, Barium, Manganese,
Iron, Zinc, Copper, Bromine, and Lead. As a complement to the elemental maps,
spatially resolved point analyses provide quantitative results and have been
used to convert mapped intensities to concentrations. Our results unequivocally
show that the feathers in the Archaeopteryx are not simply
impressions. Several rachises are clearly visible in maps of both phosphorous
and sulfur; thus, indicating that feather chemistry has been partially
preserved. Furthermore, zinc and copper levels in the bone are similar to
concentrations in extant avian species. We therefore conclude that part of the
original bone composition is preserved in these critical elements. The SRS-XRF
scans of Confuciuornis show that
trace metals, such as copper, are present in fossils as organometallic
compounds most likely derived from original eumelanin. The distribution of
these compounds provides a long-lived biomarker of melanin presence and density
within a range of fossilized organisms. Metal zoning patterns may be preserved
long after structural evidence (melanosomes) for color has been destroyed. Curation
artefacts have also been resolved. Our results show SRS-XRF is a powerful new
tool for the study of paleontological and archaeological samples.
It
is fun to note that the meeting next week is full! There seems an awful lot of
interest in this wonderful field of synchrotron-based imaging...as well there
should be.
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