COMMUNICATION

Isotopic characterization of organic matter from the DanekBonebed (Edmonton, Alberta, Canada) with special referenceto amber1

Lauren J. Davies, Ryan C. McKellar, Karlis Muehlenbachs, and Alexander P. Wolfe

Abstract: During the course of excavating the Maastrichtian Danek Bonebed in the city of Edmonton, a range of well-preservedorganic materials was recovered alongside vertebrate remains, including amber, coal, and unpermineralized plant fragments.Herein, we report carbon and hydrogen stable isotopic characterizations of these materials to provide ancillary insights intogenesis of the fossil deposit. These analyses permit isotopic comparisons between the various organic fractions at the Daneklocality, as well as with other Late Cretaceous localities in Alberta. The investigation of amber proves particularly informative,with carbon stable isotope ratios that are regionally consistent and furthermore conform to the larger, global-scale isotopictrend for this material, and hydrogen results that inform paleoclimatic conditions at the time of amber formation. Whencoupled with chemotaxonomic information from amber Fourier-transform infrared spectroscopy, the isotopic results indicatea consistent taxodioid forest composition and relatively stable environmental conditions across the three horizons that encap-sulate the Danek bonebed.

Résumé : Au cours de l’excavation du Danek Bonebed (Maastrichtien) dans la ville d’Edmonton, une gamme de matériauxorganiques bien conservés a été récupérée tout près de restes de vertébrés; ces matériaux comprennent de l’ambre, du charbonet des fragments de plantes non perminéralisés. Dans cet article, nous présentons les caractérisations des isotopes stablescarbone et hydrogène de ces matériaux afin de fournir des points de vue supplémentaires sur la genèse du dépôt fossilifère. Cesanalyses permettent de comparer les isotopes des diverses fractions organiques a l’emplacement Danek et a d’autres localités duCrétacé tardif en Alberta. L’étude de l’ambre s’est avérée particulièrement informative. En effet, les rapports stables des isotopesdu carbone sont constants a travers la région et, de plus, ils concordent avec la tendance isotopique a plus grande échelle pource matériau et avec les résultats pour l’hydrogène qui donnent des indices quant aux conditions paléoclimatiques au moment dela formation de l’ambre. Lorsque jumelés a l’information chimiotaxonomique d’une spectroscopie infrarouge a transformationde Fourier de l’ambre, les résultats isotopiques indiquent une composition de forêt taxodioide et des conditions environnemen-tales relativement stables a travers les trois horizons qui contiennent le « lit d’os » de Danek. [Traduit par le Rédaction]

IntroductionAn array of information can be extracted from dinosaur

bonebed material to recreate both the populations of organismspreserved within the deposit and the environment in which theylived. While the vertebrate fossils themselves are key for recon-structing population dynamics, diet, and behavior, other organicmaterials preserved within the sediments offer valuable insightsthat bolster such reconstructions by providing a broader paleo-ecological context. In this paper, we report botanical remains andtheir associated stable isotopic composition from the exceptionalMaastrichtian Danek Bonebed located in Edmonton, Alberta, Can-ada. We focus on three types of organic material (amber, coal, andunpermineralized plant fragments), revealing strengths and lim-itations of the respective isotopic signatures. Particular attentionis paid to the amber samples, which comprise the bulk of isotopicanalyses and are particularly resistant to diagenetic modification(Tappert et al. 2013). Amber, or polymerized plant resin, occursin the geological record since the late Carboniferous (Bray and

Anderson 2009), and it has been shown to preserve faithfully awealth of environmental and ecological information pertainingto ancient forest ecosystems. Amber deposits have been studiedextensively in Alberta and surrounding regions (Fig. 1), yieldinga rich array of paleoenvironmental information (McKellar et al.2008; McKellar and Wolfe 2010).

Study site and materials consideredSite L2379, known as the Danek Bonebed (hereafter DBB), is

located on the southern bank of Blackmud Creek in south Edmon-ton. Discovered in 1988, the site was excavated in 1989 and 1991 byresearchers from the Royal Tyrrell Museum of Paleontologybefore being reopened in 2006 by the University of Alberta’sLaboratory for Vertebrate Paleontology. There are presently threequarries on site, one from the initial excavation (Quarry 1), a sec-ond 50 m upstream (Quarry 2), and a third opened in 2007 that liesbetween the former two (Quarry 3). All three quarries of the DBBfit within the Whitemud Member (Unit 5) of the Horseshoe Can-yon Formation (Fig. 1). Direct geochronological control is provided

Received 16 March 2014. Accepted 18 July 2014.

Paper handled by Associate Editor Victoria Arbour.

L.J. Davies, K. Muehlenbachs, and A.P. Wolfe. Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, AB T6G 2E3, Canada.R.C. McKellar. Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, AB T6G 2E3, Canada; Royal Saskatchewan Museum,2430 Albert Street, Regina, SK S4P 2V7, Canada.Corresponding author: Lauren J. Davies (e-mail: ljdavies@ualberta.ca).1This paper is part of a Special Issue entitled “The Danek Edmontosaurus Bonebed: new insights on the systematics, biogeography, and palaeoecology of LateCretaceous dinosaur communities”.

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Can. J. Earth Sci. 51: 1017–1022 (2014) dx.doi.org/10.1139/cjes-2014-0057 Published at www.nrcresearchpress.com/cjes on 15 December 2014.

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by volcanic ash underlying the lowermost unit containing here,yielding a provisional maximum age of �67 Ma (Late Maas-trichtian) for the DBB fossil material (Eberth et al., this issue).

To date, four dinosaur taxa have been identified from the local-ity, including numerous hadrosaur bones likely referable toEdmontosaurus, skull elements of the tyrannosaur Albertosaurus, asingle troodontid tooth, and a ceratopsian horn core. These dino-saurs, in particular the hadrosaurs, are assumed to have died enmasse as the result of a catastrophic event such as a storm orflood. The concentration of bone material at the base of the DBBexposure suggests the animals were buried soon after death, al-though mapping of the excavated remains suggests that scaveng-ing occurred before final burial. Excellent preservation of the DBBmaterial allows a unique opportunity for the analysis of amber,coal, and plant fragments from the bone-rich strata, noting that,in general, sediments preserving coeval botanical and vertebratefossils are exceptionally rare in the Late Cretaceous of Alberta.

The botanical specimens considered here originate from threesuccessive stratigraphic horizons within quarries 1 (horizons K59and Q1N) and 2 (Q2E) of the DBB. Stratigraphically, K59 is theyoungest, immediately overlying Q1N, whereas Q2E is the oldest.Botanical fossil were concentrated by sieving (using >425 �m and40–425 �m mesh sizes) and rinsing large volumes of material(�10 kg) from each horizon. Recovered material was suspended indeionized water and cleaned by ultra-sonication (10 min). Thematerial was then air-dried and fragments of amber, coal, andunpermineralized plant tissue were isolated manually under astereomicroscope. No further chemical or thermal pretreatmentwas undertaken. Samples were photographed prior to prepara-tion for stable isotopic and spectroscopic analyses (Fig. 2).

Geochemical analyses: stable isotopes and infraredspectroscopy

Carbon (C) and hydrogen (H) stable isotopic compositions weremeasured from DBB organic specimens (1–10 mg) as follows. Sam-ples were combusted at 800 °C in vacuum-sealed quartz tubeswith CuO (1 g), Cu (100 mg), and Ag (100 mg). CO2 and H2O evolvedduring combustion were extracted off-line, and H2O was reduced

Fig. 1. Albertan amber localities and their distribution relative tothe Edmonton Group. (A) Subcrop diagram of Upper Cretaceousformations in Alberta, with the Saskatchewan River drainageindicated. (B) Stratigraphic diagram of the Edmonton Group,focusing on the Horseshoe Canyon Formation and its recognizedunits. Modified from Energy, Mines and Resources Canada (1985)Canada Drainage Basins map, with geology from Dawson et al.(1994), MacEachern and Hobbs (2004), McKellar and Wolfe (2010),and Eberth and Braman (2012).

Fig. 2. Examples of plant organic matter recovered from theDanek Bonebed. (A) Typical amber fragments showing a range oftextures dominated by hardened droplets. (B) Coal (lignite) and(C) unidentified unpermineralized plant remain, most likely aconifer twig fragment.

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to H2 using Zn (100 mg) prior to the analysis of H isotopes. 13C/12Cand 2H/1H ratios were measured from CO2 and H2 gas, respec-tively, using a Finnigan MAT–252 isotope-ratio mass spectrome-ter. Results are expressed in standard � (delta) notation andreported relative to Vienna Pee Dee Belemnite (VPDB) for �13C andVienna Standard Mean Ocean Water (VSMOW) for �2H. Thesummed reproducibility of these analyses yields uncertaintiesof ± 0.1‰ for �13C and ± 3‰ for �2H.

Fourier transform infrared (FTIR) micro-spectroscopy was con-ducted on untreated amber flakes chipped from fresh surfacesfree of inclusions. Specimens were mounted on infrared-transparentNaCl discs and kept to thicknesses ≤ 10 �m to minimize oversatu-ration. Absorption spectra were collected over the 700–4000 cm−1

(wavenumber) interval with a Thermo Nicolet Nexus 470 FTIRspectrometer equipped with a Continuum IR microscope. Spec-tral resolution was 4 cm−1 and beam size was set between 50 and100 �m. No additional manipulations, such as continuum re-moval or smoothing, were applied to the spectra. Further detailsof our FTIR methodology have been presented elsewhere, includ-ing results from additional Cretaceous ambers from Alberta thatenable comparative assessment of the results from DBB (McKellarand Wolfe 2010; Tappert et al. 2011).

ResultsUnpermineralized botanical remains are common in the DBB

sediment matrix. Coal is represented by lignite grade fragmentsthat are disseminated throughout the material, and consequentlyunlikely to represent in situ coalification processes, as seen else-where in the Horseshoe Canyon Formation. Coal at the DBB isthus either reworked fluvially from adjacent coal measures orrepresents inputs of locally derived fire-borne char. The immaturecharacter of the material suggests the latter as the most likelyorigin. Plant fragments including stems and foliage are more rare,but these are wholly unpermineralized, which is exceptional forthe Late Cretaceous of Alberta. The plant material appears primar-ily derived from conifers, although other plant taxa, includingangiosperms, appear to be represented as well. A detailed consid-eration of the DBB paleobotanical assemblage is beyond the scopeof this paper but certainly merits attention given the quality ofpreservation: both coalified and unpermineralized plant tissuesfrom the site have the potential to express cellular preservation.However, amber is by far the most commonly recovered form ofplant organic matter, spanning a considerable range of color andclarity, and ranging from translucent to opaque varietals (Fig. 2).

Fig. 3. FTIR spectra of amber exemplars from each horizon in the Danek Bonebed, shown alongside spectra from Albertan Campanianambers and resins of two representative modern cupressaceous conifers, Metasequoia glyptostroboides and Thuja standischii.

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In FTIR spectroscopy, representative amber specimens fromeach of the three DBB horizons are internally consistent (Fig. 3),conferring a common botanical origin. Furthermore, the DBB am-ber FTIR spectra are directly comparable with other and slightlyolder (Campanian) Late Cretaceous amber deposits from Alberta,especially those from Drumheller and the noted Grassy Lake lo-cality (McKellar et al. 2008). Collectively, these ambers are mostlikely attributable to conifers of the family Cupressaceae, givenmore or less pronounced expressions of the aromatic C-H bands at890 and 3090 cm−1. Among modern conifers, these features areonly prominent in cupressaceous taxa, as illustrated by the spec-tra from Metasequoia and Thuja (Fig. 3). Such an assignment isentirely consistent with the recovery of Parataxodium foliage fromGrassy Lake amber (McKellar and Wolfe 2010). Indeed, this extinctgenus is the most likely candidate source tree for the DBB amber,as it appears to have been regionally widespread along the west-ern shores of the Interior Seaway during the Late Cretaceous.Compositionally, the amber from DBB is unexceptional in thecontext of known Alberta amber deposits.

Stable isotopic measurements from DBB amber, coal, andplant tissues are reported in Table 1 and illustrated in Fig. 4. The�13C values of all organic fractions range between −22‰ and−26‰, well within the expected range for amber and C3 plants(Nissenbaum and Yakir 1995). There is no apparent distinctionbetween the �13C values obtained from the different horizons ofDBB material analyzed. The coal and plant fragments have a nar-rower range of �13C values relative to amber samples, althoughthis partially reflects a smaller population size. Coal (n = 3) is onaverage depleted by 0.8‰ relative to amber (n = 12), which in turnis isotopically lighter than the plant fragments (n = 2) by 1.7‰(Table 1). Amber �13C values from the DBB are in general compa-rable to results from Campanian ambers from Grassy Lake,Edmonton (North Saskatchewan River valley) and Morrin Bridge(Red Deer River; Fig. 4A).

�2H values from amber and coal (Fig. 4B) reveal a clear separa-tion between the two materials. Amber (mean �2H = −309‰ ±12‰) is consistently depleted relative to coal (mean �2H = −147‰ ±18‰). Unfortunately, we were unable to yield gas from the plantfragments to produce �2H results, due to insufficient sample size.These DBB �2H results are consistent with our prior results fromAlberta (McKellar et al. 2008), as well as broader considerations oftypical values for coal and amber (Nissenbaum and Yakir 1995).However, it is unclear to what extent coal samples capture theoriginal isotopic signal imparted by waters accessed by coal-producing plants, as opposed to diagenetic effects imparted onthe hydrogen signature of coal. Indeed, burial effects, with respectto temperature and pressure, may deplete the �2H of plantfractions by up to −20‰ during maturation (Rigby et al. 1981;Schimmelmann et al. 2006). Nonetheless, as with the �13C results,the �2H measurements show no apparent stratigraphic trend be-tween successive horizons in the DBB (Fig. 4).

DiscussionCompositionally (Fig. 3) and isotopically (Table 1; Fig. 4), there is

scant evidence for stratigraphic variability in plant organic matterwithin the DBB. Furthermore, all results fall within the predictedrange for comparable Late Cretaceous materials from Alberta.This attests to the excellent preservation observed at DBB, andfurthermore suggests stable environmental conditions during theinterval of accumulation. Indeed, for a Late Cretaceous ecosystem,the mean amber �13C value of −24.1‰ ± 0.99‰ recorded at DBB isconsistent with minimal tree ecophysiological stress, such asdrought and (or) insect infestation, which would result in conspic-uously enriched �13C signatures (McKellar et al. 2011). The DBBamber �13C values furthermore plot directly on the global seculartrend of amber carbon isotopes presented by Tappert et al. (2013),in being intermediate between the majority of Early Cretaceous

and Paleocene ambers compiled thus far. This provides furtherevidence that resin �13C capture not only a signal relating to localedaphic factors but also a second-order influence underpinned byatmospheric composition with respect to pCO2 and pO2.

With respect to amber �2H, it is possible to extract additionalpaleoclimatic information because plant metabolic waters deriveultimately from precipitation. Indeed, modern resin �2H variespredictably with altitude, latitude, and temperature, producingprogressively more enriched H isotopic ratios with increasingtemperature (Stern et al. 2008; Dal Corso et al. 2011). These pat-terns can be complicated by variations in local source waters —something that should be considered as a caveat for the followinginferences, because of the potential influence of relatively 2Henriched water from the nearby Western Interior Seaway andpotential differences in atmospheric circulation. To estimate theisotopic composition of meteoric waters at the time of amberformation, a constant fractionation of −229‰ between water andplant resin can be applied to the measured �2H values (Chikaraishiet al. 2004; Wolfe et al. 2012). This exercise produces an estimated�2H of −80‰ for meteoric waters at the Danek locality, with arange from −68‰ to −92‰. These values are heavier than all butthe most enriched precipitation values in the modern isoscape ofEdmonton, and correspond to air temperatures of 24 ± 2 °C (Fig. 5).While this is clearly a provisional paleotemperature estimate thatrequires validation by additional proxies, it is a reasonable firstapproximation of mean growing-season temperatures at the DBBlocality, noting that Parataxodium was a deciduous conifer forwhich we assume a similar ecological niche as its closest livingrelative, Metasequoia. As modern mean summer temperature atEdmonton is 16 °C, the reconstruction from amber �2H (Fig. 5)suggests temperatures in the order of 8 °C warmer than present inthe Maastrichtian. However, the range of �2H values recorded byAlberta ambers (Fig. 4B) suggests either that temperatures variedconsiderably during the Campanian-Maastrichtian interval, orthat source waters were strongly modulated by additional factors,such as proximity to the Interior Seaway. For example, amberfrom the North Saskatchewan River in Edmonton, which is asso-ciated with coal measures that are slightly older than the DBB

Table 1. Stable isotopic ratios from various organic fractions collectedin the Danek bonebed.

Material �13C (‰ VPDB) �2H (‰ VSMOW)

K59 horizonAmber −24.0 −302Amber −23.9 −302Amber −24.2 −290Amber −23.6 −331Coal −25.3 −143Q2E horizonAmber −25.2 −300Amber −24.3 −303Amber −23.4 −314Amber −23.3 −327Coal −25.3 −166Plant macrofossil −23.5 —Q1N horizonAmber −25.9 −308Amber −25.3 −316Amber −24.1 −301Amber −22.3 —Coal −24.3 −131Plant macrofossil −22.9 —

Amber mean (SD) −24.1 (0.99) −309 (12)Coal mean (SD) −24.9 (0.55) −147 (18)Plant macrofossil mean (SD) −23.2 (0.40) —

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(Chen et al. 2005), yield �2H values that are fully 30‰ more de-pleted (Fig. 4).

ConclusionBotanical fossils, and especially amber, provide coherent �13C

and �2H signatures for the Danek Bonebed. With respect to �13C,amber is slightly enriched relative to coal but depleted relative tounpermineralized plant macrofossils. Amber �2H is depleted by150‰ relative to coal, reflecting different biosynthetic pathwaysand potentially diagenetic overprinting of the coal. The �13C and�2H values are entirely consistent with prior results from the LateCretaceous of Alberta and furthermore show no directional strati-graphic variability within the bonebed. Of the materials consid-ered, we deem amber the most reliable environmental isotoperecorder, in part because the isoprenoid (C5H8) building blocks ofterpene resin acids that polymerize to form amber are particu-larly resistant to isotopic exchange (Diefendorf et al. 2012). Amber�13C values from the Danek locality suggest unstressed ecologicalconditions for resin-producing trees, whereas �2H indicate warm(�24 °C) growing seasons. We surmise that taxodioid forests inthe immediate environs of the DBB were healthy and living undernearly ideal growth conditions, and that environmental condi-tions were stable during and after accumulation of the locality’srich vertebrate assemblage.

AcknowledgementsWe thank Philip Currie and Eva Koppelhus for the opportunity

to work on the Danek Bonebed material, Ralf Tappert andMichelle Tappert for assistance in regional fieldwork, Jessica

Fig. 4. Isotopic results from the various plant organic fractions recovered from the Danek Bonebed. (A) �13C and (B) �2H. These are shownalongside a range of prior results from Campanian ambers in Alberta (McKellar et al. 2008).

Fig. 5. The relationship between modern precipitation �2H and airtemperature for Edmonton, taken from the Global Network ofIsotopes in Precipitation network (IAEA/WMO 2014). The dashed lineand shaded grey area represent the mean and 2 SD range,respectively, for the predicted �2H of Maastrichtian precipitation,using a constant fractionation of −229‰ between plant water andamber �2H from the Danek Bonebed.

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Edwards for insights concerning fossil plant assemblages, ThomasStachel for unrestricted access to spectroscopic facilities, andChris Holmden and one anonymous reviewer for constructivecomments that improved this manuscript. Research was fundedby the Natural Sciences and Engineering Research Council of Can-ada (Discovery Grants to K.M. and A.P.W.; Postdoctoral Fellowshipto R.C.M.).

ReferencesBray, P.S., and Anderson, K.B. 2009. Identification of carboniferous (320 million

years old) class Ic amber. Science, 326: 132–134. doi:10.1126/science.1177539.PMID:19797659.

Chen, D., Langenberg, W., and Beaton, A. 2005. Horseshoe Canyon-Bearpawtransition and correlation of associated coal zones across the Alberta plains.Alberta Energy and Utilities Board, EUB/AGS Geo-Note 2005-08. pp. 1–23.

Chikaraishi, Y., Naraoka, H., and Poulson, S.R. 2004. Carbon and hydrogen iso-topic fractionation during lipid biosynthesis in a higher plant (Cryptomeriajaponica). Phytochemistry, 65: 323–330. doi:10.1016/j.phytochem.2003.12.003.PMID:14751303.

Dal Corso, J., Preto, N., Kustatscher, E., Mietto., P., Roghi, G., and Jenkyns, H.2011. Carbon-isotope variability of Triassic amber, as compared with woodand leaves (Southern Alps, Italy). Palaeogeography, Palaeoclimatology, Pa-laeoecology, 302: 187–193. doi:10.1016/j.palaeo.2011.01.007.

Dawson, F.M., Evans, C.G., Marsh, R., and Richardson, R. 1994. Geological historyof the Peace River Arch. In Geological atlas of the western Canadian sedimen-tary basin, Compiled by G.D. Mossop and I. Shetson. Canadian Society of Pe-troleum Geologists and Alberta Research Council, Calgary, Alberta [online].Available from http://www.ags.gov.ab.ca/publications/wcsb_atlas/atlas.html[cited 14 March 2014].

Diefendorf, A.F., Freeman, K.H., and Wing, S.L. 2012. Distribution and carbonisotope patterns of diterpenoids and triterpenoids in modern temperate C3trees and their geochemical significance. Geochimica et Cosmochimica Acta,85: 342–356. doi:10.1016/j.gca.2012.02.016.

Eberth, D.A., and Braman, D.R. 2012. A revised stratigraphy and depositionalhistory for the Horseshoe Canyon Formation (Upper Cretaceous), southernAlberta plains. Canadian Journal of Earth Sciences, 49(9): 1053–1086. doi:10.1139/e2012-035.

Energy, Mines and Resources Canada. 1985. Canada—drainage basins. The Na-tional Atlas of Canada. 5th ed. Geographical Services Division, Surveys andMapping Branch, Ottawa, Ont. http://geogratis.gc.ca/api/en/nrcan-rncan/ess-sst/7b309ad9-9398-51d4-89d2-32b3871ec3ab.html.

IAEA/WMO. 2014. Global network of isotopes in precipitation. The GNIP data-base. Available from http://www.iaea.org/water [accessed 1 March 2014].

MacEachern, J.A., and Hobbs, T.W. 2004. The ichnological expression of marineand marginal marine conglomerates and conglomeratic intervals, Creta-ceous Western Interior Seaway, Alberta and northeastern British Columbia.Bulletin of Canadian Petroleum Geology 52(1): 77–104. doi:10.2113/52.1.77.

McKellar, R.C., and Wolfe, A.P. 2010. Canadian amber. In Biodiversity of fossils inamber from the major world deposits. Edited by D. Penney. Siri ScientificPress. pp. 96–113.

McKellar, R.C., Wolfe, A.P., Tappert, R., and Muehlehbachs, K. 2008. Correlationof Grassy Lake and Cedar Lake ambers using infrared spectroscopy, stableisotopes, and palaeoentomology. Canadian Journal of Earth Sciences, 45(9):1061–1082. doi:10.1139/E08-049.

McKellar, R.C., Wolfe, A.P., Muehlehbachs, K., Tappert, R., Engel, M.S., Cheng, T.,and Sánchez-Azofeifa, G.A. 2011. Insect outbreaks produce distinctive carbonisotope signatures in defensive resins and fossiliferous ambers. Proceedingsof the Royal Society of London B: Biological Sciences, 278: 3219–3224. doi:10.1098/rspb.2011.0276.

Nissenbaum, A., and Yakir, D. 1995. Stable isotope composition of amber. InAmber, resinite and fossil resins. Edited by K.B. Anderson and J.C. Crelling.American Chemical Society Symposium, 617: 32–42. doi:10.1021/bk-1995-0617.ch002.

Rigby, D., Batts, B.D., and Smith, J.W. 1981. The effect of maturation on theisotopic composition of fossil fuels. Organic Geochemistry, 3: 29–36. doi:10.1016/0146-6380(81)90010-3.

Schimmelmann, A., Sessions, A.L., and Mastalerz, M. 2006. Hydrogen isotopic(D/H) composition of organic matter during diagenesis and thermal matura-tion. Annual Review of Earth and Planetary Sciences, 34: 501–533. doi:10.1146/annurev.earth.34.031405.125011.

Stern, B., Lampert Moore, C.D., Heron, C., and Pollard, A.M. 2008. Bulk stablelight isotopic ratios in recent and archaeological resins: towards detectingthe transport of resins in antiquity? Archaeometry, 50: 351–370. doi:10.1111/j.1475-4754.2007.00357.x.

Tappert, R., Wolfe, A.P., McKellar, R.C., Tappert, M.C., and Muehlenbachs, K.2011. Characterizing modern and fossil gymnosperm exudates using micro-Fourier transform infrared spectroscopy. International Journal of Plant Sci-ences, 172: 120–138. doi:10.1086/657277.

Tappert, R., McKellar, R.C., Wolfe, A.P., Tappert, M.C., Ortega-Blanco, J., andMuehlenbachs, K. 2013. Stable carbon isotopes of C3 plant resins and ambersrecord changes in atmospheric oxygen since the Triassic. Geochimica etCosmochimica Acta, 121: 240–262. doi:10.1016/j.gca.2013.07.011.

Wolfe, A.P., Csank, A.Z., Reyes, A.V., McKellar, R.C., Tappert, R., andMuehlenbachs, K. 2012. Pristine early eocene wood buried deeply in kimber-lite from northern Canada. PLoS ONE, 7: e45537. doi:10.1371/journal.pone.0045537. PMID:23029080.

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