Using light to describe the ancient world

Archive for the ‘Infrared’ Category

#Total speculation: an instant isotope reader for fossil bone?

Spinosaurus, the estuary-dwelling super predator. Photo by Kabacchi (2009)

Spinosaurus, a semi-aquatic dinosaur. Photo by Kabacchi (2009)

I am going to do something a little bit different with this post and predict a future scientific instrument. I got the idea for this post after reading an interesting list of inventions inspired by science fiction, compiled by Mark Strauss at the Smithsonian.

You see, I really enjoy science fiction. I like how, given enough time, technological or scientific predictions can become reality. Check out the early predictions of continental drift for a great example. I like that scientists are free to receive inspiration from anywhere, including fiction. So, on that note, allow me to make my own prediction. In the not-too-distant future, I think there will be a non-destructive device that measures the oxygen isotopic composition of phosphate in bone.

Allow me to explain.

Did you know that Spinosaurus, the record-breaking sometimes super-predator, spent much its life standing in water catching fish? We know this because Romain Amiot and colleagues did an amazing job of analysing the oxygen isotopic composition of phosphate in the ancient bones of Spinosaurus. Some background on oxygen isotopes:

  • two atoms of the same element (like oxygen) that differ in their numbers of neutrons are actually two isotopes of the same element
  • the atoms in any substance are actually a mixture of isotopes, and the ratio of isotopes can change from place to place (i.e. different isotopic compositions)
  • thanks to evaporation and precipitation, different bodies of water (rivers, estuaries, oceans) have different oxygen isotopic compositions
  • animals ingest water  – some of the oxygen from this ingested water is stored as phosphate and used by the animal for bone construction
  • ingested oxygen mostly retains it’s isotopic composition, so animals end up storing evidence about the bodies of water they associate with

I have always liked this Spinosaurus study for the simple fact that I now picture this gigantic dinosaur wading in a North African estuary. The obvious next question though, is “Why don’t we have these kinds of stories for every dinosaur?” Quite simply, this is expensive scienceThe process of extracting phosphate from fossil bone is destructive (…fossils are precious) and labor intensive, and analyses require dedicated and often pricey lab equipment. Wouldn’t it be great if there was another way of getting these data, so we could tell more Spinosaurus-like stories?

So here is my speculation. One day we will be able to analyse the isotopic composition of bone phosphate using a non-destructive device. This isn’t totally random – there is actually an existing instrument that does something similar (Note: feel free to skip the video – it’s an advertisement for a scientific instrument):

That video doesn’t do a great job of actually saying how the instrument works. In essence:

  • A spectrometer shines infrared light at a sample
  • Molecules or minerals in that sample contain atoms, and some of these atoms share covalent bonds
  • The atoms shared by the covalent bonds move relative to one another – you can think of the bond ‘stretching’, ‘bending’, ‘twisting’ etc.
  • Each ‘stretch’, ‘bend’ and ‘twist’ requires energy, which is gained by absorbing infrared light
  • Actually, only very specific wavelengths of infrared light are absorbed – the wavelengths absorbed match the energy needed to ‘stretch’, ‘bend’ or’twist’ the bond
  • The energy needed to ‘stretch’, ‘bend’ or ‘twist’ the bond is partly determined by the mass of the atoms sharing the covalent bond
  • Different isotopes have different masses –  the ‘vibrating’ bonds of different isotopes require different wavelengths of light
  • We can figure out which infrared wavelengths correspond to which isotope-bond systems
  • A detector in the spectrometer counts all of the wavelengths that are not absorbed by the sample, which in turn tells us which wavelengths are absorbed
  • By comparing the amounts of each isotope-informative wavelength that are absorbed, we can calculate the isotopic composition of the sample.

Simple enough, right? Well, right now this works well for CO2 because it is a carbon-and-oxygen isotope system. A CO2 molecule with two oxygen-16 isotopes has noticeably different vibrational frequencies compared with a CO2 molecule with two oxygen-18 isotopes, and so we can see distinct peaks for each isotopologue in an infrared spectrum (isotopologues are molecules that only differ in their isotopic compositions). Karl Dierenfeldt provided a great description of this phenomenon in this chemistry experiment (Dierenfeldt 1995). Yes, differences in peak positions from each CO2 isotopologue are subtle, but infrared spectrometers have long been sensitive enough to detect them.

So, what about the different isotopologues of phosphate in bone? First off, infrared spectrometers work really well on gases, liquids and translucent or highly polished solids. Of course, polishing a sample requires some destruction, which is what we would need to do to fossil bone. That’s fine, we can instead use Raman spectroscopy to get our spectrum without sample destruction. The real problem is resolution. At the moment we cannot resolve the peaks we get from a Raman spectrum of bone into phosphate isotopologues. Such fine levels of resolution might be possible one day, and on that day, we will have a device that can quickly give us ancient environmental data from dinosaur bones (even while they are on display in a Museum).

What a day that will be.
Dierenfeldt KE. 1995. Isotope ratio, oscillator strength, and band positions from CO2 IR spectra: a physical chemistry experiment. Journal of Chemical Education 72: 281-283.

Amiot R, Buffetaut E, Lécuyer C, Wang X, Boudad L, Ding Z, Fourel F, Hutt S, Martineau F, Medeiros A, Mo J, Simon L, Suteethorn V, Sweetman S, Tong H, Zhang F, Zhou Z. 2010. Oxygen isotope evidence for semi-aquatic habits among spinosaurid theropods. Geology 38: 139–142.

#Organic traces in dinosaur embryos

Robert Reisz and colleagues have described dinosaur embryos in a Letter published in Nature. The embryos are from a sauropodomorph dinosaur, “…probably Lufengosaurus…”, and were collected from Early Jurassic sediments (Sinemurian, 190–197 million years old) in the Yunnan Province of China. The tiny embryonic bones are impressive and the microstructural detail (i.e. histology) is astounding. The thing that caught my eye, though, was the evidence for organic molecules.

Thin sections of the tiny dinosaur bones were analysed at the National Synchrotron Radiation Research Center (NSRRC) in Taiwan. The researchers were interested in the wavelengths of infrared light that would be absorbed by the fossils (the synchrotron was their light source). Infrared absorbance is an excellent method for identifying molecules in a sample. Atoms bind together to form molecules – the type of atoms and the way they are bound controls the wavelengths of light that a molecule will absorb. More specifically, a molecule can be identified from the wavelengths of light it absorbs. The researchers presented the results from one bone: infrared wavelengths were directed at 120 points (150 × 180 µm, one spectrum collected every 15 µm), and the spectrum of wavelengths absorbed from each point was mapped.

Organic remnants in a dinosaur bone. Infrared absorption in the amide I and amide II regions provides strong evidence for a peptide bond, the ‘backbone’ of proteins, including collagen. Light microscope images show section of fossil bone that was analysed (left), colored maps show the distribution of apatite, amide I and a carbonate (middle), and spectra were collected from points highlighted with a red cross (right). Reprinted by permission from Macmillan Publishers Ltd: Nature. RR Reisz et al. Nature 496, 210-214 (2013) doi:10.1038/nature11978, copyright (2013).

Organic remnants in a dinosaur bone. Infrared absorption in the amide I and amide II regions provides evidence for a peptide bond, which are found in proteins. Light microscope images show section of fossil bone that was analysed (left), colored maps show the distribution of apatite, amide I and a carbonate (middle), and spectra were collected from points highlighted with a red cross (right). Reprinted by permission from Macmillan Publishers Ltd: Nature. RR Reisz et al. Nature 496, 210-214 (2013) doi:10.1038/nature11978, copyright (2013).

Some of wavelengths absorbed by the dinosaur bones would also be absorbed by the proteins of living animals. The basic structure of a protein involves a set of small molecules (amino acids) linking together to form a long chain (peptide). The ‘linking together’ forms a peptide bond, which has a characteristic infrared absorption. The characteristic absorptions of a peptide bond appear at very specific regions in an infrared absorption spectrum – two of those regions fall between 1500 and 1700 cm-1 and are termed ‘amide I and amide II’. The embryonic dinosaur bones absorb infrared light in the amide I and amide II regions, suggesting the presence of a peptide. Bone is a mixture of mineral (bioapatite) and protein (collagen), so it might be possible that the peptide traces in the fossil are remnants of collagen. The authors state that “…Previous reports of preserved dinosaur organic compounds, or ‘dinosaurian soft tissues’, have been controversial because it was difficult to rule out bacterial biofilms or some other form of contamination as a possible source of the organics. Our results clearly indicate the presence of both apatite and amide peaks within woven embryonic bone tissue, which should not be susceptible to microbial contamination or other post-mortem artefacts….”

Remnant collagen from a 190 million year old dinosaur embryo? Might well be.

Reisz, R R et al. 2013. Embryology of Early Jurassic dinosaur from China with evidence of preserved organic remains. Nature 496, 210-214.

#Ancient plants record mountain growth

Plant walls includes 'sunblock' compounds, and plants that live at higher altitudes have higher 'sunblock' concentrations. Barry Lomax and colleagues consider the mountain building implications of this relationship. Photo from Wikimedia Commons. Graph reproduced after Lomax et al. 2012

Plants that live at higher altitudes have higher concentrations of ‘sunblock’ compounds in their walls. Barry Lomax and colleagues consider the mountain building implications of the ‘sunblock’/altitude relationship. Photo from Wikimedia Commons. Graph reproduced after Lomax et al. 2012

How quickly do mountains rise? The Southern Alps have been rapidly rising for the last five million years (…stone giants?), and India started raising the Himalayas about 10 million years ago. We might imagine dramatically different landscapes in these parts of the world before the mountains grew. Mountains have a profound effect on local climate, vegetation and animals, so when we reconstruct ancient environments in mountainous places, we need to know how tall the mountains were back in the day.

Modeling the rate of mountain growth is a difficult business, and many models factor in climate change, which is a science all on its own. Fortunately, infrared spectroscopy might provide an easier method. Barry Lomax and colleagues have recently described a method for calculating paleoaltimetry, that is, how high something was in the past, and suggested it could be useful for figuring out rates of mountain growth. In essence, imagine you are standing next to a deposit of fossil plants, and you know the altitude you are standing at, and the age of the fossil deposit. If you calculate the altitude that those plants were growing at during ancient times, then you can calculate a rate of altitude change. So, how can we calculate paleoaltimetry from a fossil plant?

It all comes down to sunlight. From Lomax et al. 2012 “…UV-B radiation flux increases with altitude…due to the physical properties of the atmosphere…” Consider then, that “…The vast majority of terrestrial land plants require sunlight to drive photosynthesis leading to exposure to high-energy short wavelength UV-B radiation, resulting in damage to plant proteins, membrane lipids and DNA. One mechanism by which plants can mitigate these effects is via the up-regulation of UV-B absorbing compounds (UACs)…” (Lomax et al. 2012). Plants that grow at higher altitudes have more UACs – more sunblock – and hence plants record the altitude of their growth.

The UV-B absorbing compounds include ferulic acid and p-coumaric acid, which very importantly, contain aromatic rings of carbon atoms. An aromatic ring is a group of atoms that are joined together in a closed loop, and which freely share electrons, which is what makes them useful for gobbling up UV light. An infrared spectrum of “…[s]poropollenin, the biopolymer that makes up the exine (outer wall) of spores and pollen…” includes a band at 1520 cm-1, which is attributed to aromaticity (Lomax et al. 2012). Lomax and colleagues describe the relative abundance of UACs in sporopollenin by normalizing the 1520 cm-1 band against the absorption of hydroxyl groups (a band around 3200 cm-1). Lomax and colleagues then show a relationship between UAC abundance and altitude. Sure enough, plants that live at higher altitudes need more sunblock.

The next step is to include fossils. The method of Lomax and colleagues could be applied to well-preserved fossil plants found on a mountainside, to figure out how tall the mountain was when the plants lived.

Lomax BH, Fraser WT, Harrington G, Blackmore S, Sephton MA, Harris NBW. 2012. A novel palaeoaltimetry proxy based on spore and pollen wall chemistry. Earth and Planetary Science Letters 353-354: 22–28.

Top image modified from Wikimedia Commons

#Recent News: Extending the preservation age of intact fossil chitin

Chitin, a nearly fantastical, yet completely biogenic compound, has recently been reported from a Late Eocene cuttlefish. The discovery reported by Weaver and colleagues extends the preservation age of intact chitin from 25 million to 36 million years. Image from Wikimedia.

Chitin is a natural compound with fantastical properties. Pure chitin is see-through, bendy, strong, and chemically adaptable. Plasticky and leathery pure chitin can be easily modified: adding calcium carbonate can produce armour plating and food shredding surfaces. The dynamic properties of chitin have made it a target for research, and the natural compound is now weaved into much of civilisation. New medical applications for chitin have recently been developed that might see substantial improvements for patients recovering from ear, nose and throat surgeries. All considered, chitin is natural Clarkian magic, which is perhaps surprising for a compound that has probably existed on Earth for more than 540 million years.

Chitin is an organic compound that does not preserve well in the fossil record. Recognisable arthropods are known from the Cambrian Explosion but their chitinous composition is only assumed. A discovery reported in 1997 placed the oldest tangible evidence for fossil chitin at 25 million years. In early 2011 George Cody and colleagues extended the age of fossil chitin to 417 million years on the basis of protein remnants. Very recently, however, Patricia Weaver and colleagues reported the discovery of intact fossil chitin dated to 36 million years, extending the preservation age of chitin into the Late Eocene. Evidence for the chitin was provided in part by vibrational spectroscopy.

Weaver and colleagues analysed a cuttlebone from a fossil cuttlefish (Mississaepia mississippiensis), which, as the name subtly hints at, was collected in the state of Mississippi, USA. Using Fourier Transform infrared spectroscopy, the authors observed “…[p]eaks at 1649 cm-1… and 1544 cm-1 in cuttlefish, squid and fossil spectra indicat[ing] organics consistent with β-chitin…”. These bands are attributed to carbonyl (C=O), amide (N-H) and other functional groups typical of protein. “…Closer examination of the region ca. 600–1400 cm-1…shows the principle change in M. mississippiensis is the loss of peaks in Amide III region. Amide I and II peaks may arise from chitin, but also from proteins, humics or other chemicals. It is parsimonious to assume the presence of chitin-like molecules rather than an admixture of substances displaying a similar spectrum…” The exceptional preservation of chitin in M. mississippiensis has been attributed to an originally anoxic, clay-rich depositional environment – ideal conditions for establishing physical and geochemical resistance from microbial, chemical and physical degradation. Apart from the exciting discovery of a complex, biogenic compound with almost 40 million years of antiquity, the preservation of organic molecules opens up new avenues of phylogenetic research. “Future work will focus on comparisons with other Eocene cuttlefish and the phylogenetic implications of chitinous structures with regards to the origin cuttlefish…”

Weaver PG, Doguzhaeva LA,Lawver DR, Tacker RC, Ciampaglio CN, Crate JM, Zheng W. (2011) Characterization of Organics Consistent with b-Chitin Preserved in the Late Eocene Cuttlefish Mississaepia mississippiensis. PLoS ONE 6: e28195. doi:10.1371/journal.pone.0028195

Image from Wikimedia.

#News: Spectroscopic proof for fossil feather pigmentation

Fossil feathers from Gansus yumenensis have recently revealed evidence for the preservation of original pigmentation structures. The above reconstruction of Gansus was created in 2006 (by Mark Klinger/CMNH) before melanosomes had been used to describe fossil feather pigmentation (i.e. prior to the publication of Li et al. 2010). Barden et al. (2011) indicate that that eumelanin is indeed preserved in some Gansus yumenensis feathers, which may have imparted a dark colouration to some feathers.

Microorganisms can be a bit of a problem when interpreting fossil soft tissues (see Schweitzer et al. 2005 and Kaye et al. 2008) and the problem compounds when the soft tissues are bacteria-sized and bacteria-shaped. Consider melanosomes: these sphere to cigar shaped bodies are lipid sacks stuffed full of melanin that give rise to a variety of colours. Bacteria, unfortunately, can mimic the “…size, form, spatial arrangement, organisation and apparent embedding within soft tissue…” shown by melanosomes (Barden et al. 2011).  Melanosomes have been used to describe colouration in ancient birds and dinosaurs (e.g. Clarke et al. 2010; Li et al. 2010; Zhang et al. 2010): these ancient feather artworks obviously assume that the pigment structures are melanosomes, and not bacterial reproductions. Validation may require closer scrutiny. In other words, we should check to see if the palette used to produce these master artworks actually contains paint.

This is exactly what Holly Barden and colleagues have done (Barden et al. 2011). Barden et al. (2011) combined “…morphological (imaging) and organic geochemical techniques to analyse feathers from the early Cretaceous Chinese bird Gansus yumenensis…”. Gansus was an aquatic bird that lived in the ancient Changma basin in what would become the Gansu Province of northwestern China (early Aptian/Aptian, 125 to 112 Ma). Mid-infrared spectroscopy was among the roster of geochemical techniques used to analyse two fossil feathers from Gansus yumenensis, providing the first reported used of vibrational spectroscopy on fossil feathers. Barden et al. (2011) also collected mid-IR spectra from pure melanin as a comparative standard “…The infrared spectra obtained from the fossil feathers were clearly different from those taken within the surrounding matrix…[t]he matrix showed only the presence of an inorganic silica band, whereas the fossil feathers also showed carboxylic acid, ketone, hydroxyl and potential secondary amine peaks..[t]hese peaks all occur in the Sepia officinalis melanin spectra and the responsible functional groups are clearly seen in the chemical structure of eumelanin…” Further, “…FTIR analysis revealed no bands characteristic of modern bacteria including CH bending from fatty acids or P-O-C and P-O-P stretching from phospholipids, ribose and phosphate chain pyrophosphate…” Hence, Barden and colleagues demonstrated that pigment bodies have indeed been preserved in the fossil feathers of Gansus yumenensis.

Barden HW, Wogelius RA, Li D, Manning PL, Edwards NP, van Dongen, BE. 2011. Morphological and geochemical evidence of eumelanin preservation in the feathers of the Early Cretaceous bird, Gansus yumenensis. PLoS ONE 6: e25494. doi:10.1371/journal.pone.0025494

Clarke JA, Ksepka DT, Salas-Gismondi R, Altamirano AJ, Shawkey MD, D’Alba L, Vinther J, DeVries TJ, Baby P. 2010. Fossil evidence for evolution of the shape and color of penguin feathers. Science 330: 954–957.

Kaye TG, Gaugler G, Sawlowicz Z .2008. Dinosaurian soft tissues interpreted as bacterial biofilms. PLoS ONE 3: e2808. doi:10.1371/journal.pone.0002808

Li Q, Gao K-Q, Vinther J, Shawkey MD, Clarke JA, D’Alba L, Meng Q, Briggs DEG, Prum RO. 2010. Plumage color patterns of an extinct dinosaur. Science 327: 1369–1372.

Schweitzer MH, Wittmeyer JL, Horner JR, Toporski JK. 2005. Soft-tissue vessels and cellular preservation in Tyrannosaurus rex. Science 307: 1952–1955

Zhang F,KearnsSL, Orr PJ, Benton MJ, Zhou Z, Johnson D, Xu X, Wang X. 2010. Fossilized melanosomes and the colour of Cretaceous dinosaurs and birds. Nature 463: 1075–1078.

Image credit: Mark A Klingler/CMNH 

#Archive: The origin of Baltic Amber

Alexander Wolfe and colleagues used Fourier-transform mid-infrared spectroscopy to determine the botanical origin of Baltic amber. Image is from Wikimedia commons

The value of amber has been recognised throughout human history. Amber beads were found with Teti, a pharaoh who reigned during the sixth dynasty of Egyptin ~2340 BC. Amber remained a prized possession into the 18th Egyptian dynasty as large beads were among the chattels in Tutankhamen’s tomb (Gestoso Singer 2008; Serpico and White 2000). The trade of amber flowed to Northern Africa down the ‘Amber Road’, where it was collected from the shoreline of the Baltic Sea. Such was the importance of amber that knights of the medieval Teutonic Order occupied the southern coast of the Baltic Sea in order to control the Amber Road (Heinze, 2003). The value of amber outlasted the Teutonic Knights, and in the early 1700s an entire room of the Catherine Palace was decorated in panels of amber from the coast of theBaltic Sea (the amber was later stolen during World War II). Baltic amber is still a valuable commodity, not least of all for the scientific secrets it holds.

In 2009 Alexander Wolfe and colleagues sought the botanical origin of Baltic amber. Amber is hardened tree resin and can be chemically complex. Wolfe and colleagues describe amber as being “…polymerized from a broad range of isoprenoid compounds originally produced by plant secondary metabolism. These compounds include primarily terpenoids, carboxylic (resin) acids and associated alcohols…” Further, “…the great diversity of organic compounds present in modern and fossil resins…are of considerable use in establishing relationships between amber and source trees…” Hence, the chemistry of amber is a ‘fingerprint’ for the tree that produced it. In this way, it should be possible to reconstruct the forest that was responsible for the Baltic amber.

Earlier studies had linked the production of Baltic amber to trees in one of two families, Araucariaceae or Pinaceae. Araucariaceae is mostly found in the Southern Hemisphere, and resin from the araucarian Agathis australis was a significant trade good in New Zealand during the 19th and 20th centuries. Pinaceae are mostly found in the Northern Hemisphere and are typified by pine trees. Spruce and other trees in family Pinaceae occur around theBaltic Sea today. Both tree families are viable candidates for the vast quantities of Baltic amber that has been recovered, but Wolfe and colleagues observed that “…neither group fully satisfies the range of geochemical and phytogeographical criteria…” In response, the authors decided to study the amber with vibrational spectroscopy.

Baltic amber was produced by a family of trees with a single descendent that today lives only in Japan. Image above is of Koyamaki (Sciadopitys verticillata), from Wikimedia commons.

Fourier-transform mid-infrared (FTIR) spectra were collected from modern conifer resins: Five species of Araucariaceae, 17 species of Cupressaceae, 26 species of Pinaceae and Sciadopitys verticillata, the only living representative of Sciadopityaceae. A set of modern and fossil resins were also analysed in tandem, to gauge whether the chemistry of extant trees could be matched to ancient amber. Finally, specimens of Baltic amber fromGermany,Latvia,Poland,Russia and southernSweden were analysed. From Wolfe and colleagues, “…[s]amples were first examined with a binocular microscope and crushed to fragments of less than 500 mm prior to mounting directly on NaCl stages…”

The FTIR spectra of the modern and fossil pairs were indistinguishable, meaning that the identity of fossil resins could be predicted from modern specimens. Key diagnostic regions were subsequently identified in the resin and amber spectra. These regions were to attributed functional groups within the specimens (e.g. OH stretching/asymmetric CH stretching of terminal alkene): the amber and resin specimens could be distinguished from variations in these six regions. Wolfe and colleagues analysed these diagnostic spectral regions with hierarchical clustering. In essence, spectra that were most similar clustered together, producing a ‘tree’ that described the relatedness of the samples to one another (the same method is used in cladistics). Surprisingly, Baltic amber clustered most closely with Sciadopitys verticillata and not species of Araucariaceae or Pinaceae, strongly suggesting that Baltic amber was produced by family Sciadopityaceae. The only living member of Sciadopityaceae is the Koyamaki which is endemic toJapan. In the words of Wolfe and colleagues, “…[o]ur conclusions challenge hypotheses advocating members of either of the families Araucariaceae or Pinaceae as the primary amber-producing trees and correlate favourably with the progressive demise of subtropical forest biomes from northernEurope as palaeotemperatures cooled following the Eocene climate optimum…”

Gestoso Singer G. 2008. Amber in the ancient Near East. I-Medjat 2: 17-19.

Heinze KG. 2003. Baltic sagas: events and personalities that changed the world!, 340 pp.

Serpico M, White R. 2000. Resins, amber and bitumen. In Nicholson PT, Shaw I (eds.). Ancient Egyptian materials and technology.CambridgeUniversityPress, p 430-475.

Wolfe AP, Tappert R, Muehlenbachs K, Boudreau M, McKellar RC, Basinger JF, Garrett A. 2009. A new proposal concerning the botanical origin of Baltic amber. Proceedings of the Royal Society B: Biological Sciences 276: 3403-3412.

Images sourced from Wikimedia commons:

#Recent News: A closer look

Microstructure of bone – Matthieu Lebon and colleagues present spectroscopic maps of diagenetic alteration at this fine scale

Imagine a world where you can analyse a fossil as you find it, learning what an ancient creature ate and what it’s world was like, all while sitting at its final resting place. As far fetched as that sounds, we are actually stepping closer and closer towards this point. An interesting step along this path was recently presented by Matthieu Lebon and colleagues in the Journal of Analytical Atomic Spectrometry. One of the battles with analysing a sample without first scrubbing it down is knowing where to sample, and understanding how samples change from place to place. Lebon and colleagues used Fourier Transform Infrared spectroscopy to produce fine scale chemical maps from the surfaces of fossil bones. One type of map shows the intensity of a spectral band attributed to carbonate normalised against phosphate, and hence reflects the distribution of carbonate: carbonate is a biological component of bone, but is also a near ubiquitous diagenetic gremlin that can potentially confound isotopic studies. Maps from a 15 thousand year old bone showed that carbonate had a close relationship with collagen, suggesting that the ion was an original, biogenic component. In contrast, maps from a 60 thousand year old bone showed that carbonate was centered in the most porous part of the bone, telling us that it had formed while that vile counterpart to diagenesis – groundwater – was flowing through the bone. The fine scale mapping approach may help us target the most immaculately preserved regions of fossil bone if we ever have the chance to sample on such a fine scale. Which, of course, is what our In-The-Field-Dinosaur-Analyser (ITFDA) will eventually be able to do.

Lebon M, Müller K, Bahain J-J, Fröhlich, Falguères C, Bertrand L, Sandt C, Reiche I. 2001. Imaging fossil bone alterations at the microscale by SR-FTIR microspectroscopy. Journal of Analytical Atomic Spectrometry 26: 922-929.

Image courtesy of the Department of Histology, Jagiellonian University Medical College, and sourced from Wikimedia Commons

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