ARTICLE

Dinosaur trackways from the Upper Cretaceous Oldman andDinosaur Park formations (Belly River Group) of southernAlberta, Canada, reveal novel ichnofossil preservation style1

François Therrien, Darla K. Zelenitsky, Annie Quinney, and Kohei Tanaka

Abstract: Dinosaur tracksites recently discovered in exposures of the Belly River Group in the Milk River Natural Area (MRNA)and Dinosaur Provincial Park (DPP) of southern Alberta represent a novel type of ichnofossils. The tracks, all referable tohadrosaurs, occur as sideritic or calcareous concretions protruding above fine-grained deposits and are here termed concretion-ary tracks. Detailed sedimentological, petrographic, and geochemical analyses reveal that, although the MRNA and DPP tracksare of different mineralogical compositions (calcium carbonate versus siderite, respectively), they display similar internalstructures (microscopic convoluted laminations) and occur in depositional settings indicative of wet paleoenvironments, wherethe ground was soft and water saturated. These characteristics suggest that concretionary tracks are footprint casts that formedas groundwater rich in dissolved carbonates flooded depressions left in the soft substrate. As the ponded water evaporated,minerals began to precipitate and mix with clastic material transported into the depressions, settling as finely laminated mudwithin the tracks and filling them either completely or partially. The geochemical composition of the precipitate would dependon the prevalent groundwater conditions (e.g., pH, dissolved carbonate and sulphate concrentrations). Cementation of the tracksoccurred relatively soon after burial (<100 years), possibly in response to microbial activity and saturation by mineral-richgroundwater, and modern erosion exposed the concretionary tracks by removing the softer host unit. Recognition of this noveltype of ichnofossils suggests dinosaur tracks may be more common than previously thought. Unfortunately, concretionarytracks tend to break apart rapidly when the encasing and underlying substrate erodes away, altering their diagnostic shape andrendering them indistinguishable from nonichnogenic concretions. As such, concretionary tracks may be transient ichnofossilsin the badlands, explaining why they are rarely recognized.

Résumé : Des sites préservant des empreintes de pas de dinosaures récemment découverts dans des affleurements du Groupe de BellyRiver dans la Milk River Natural Area (MRNA) et dans le Dinosaur Provincial Park (DPP) du sud de l’Alberta représentent un nouveautype d’ichnofossiles. Les empreintes, qui ont toutes été produites par des hadrosaures, sont préservées sous forme de concrétionssidéritiques ou calcaires émergeant de dépôts fins et sont ici nommées « empreintes concrétionnaires ». Des analyses sédimen-tologiques, pétrographiques et géochimiques détaillées révèlent que, bien que les empreintes de la MRNA et du DPP soient decompositions minéralogiques différentes (carbonate de calcium et sidérite, respectivement), elles possèdent des structures internessemblables (lamination convolutée microscopique) et se trouvent dans des milieux de dépôt qui reflètent des paléoenvironnementshumides où le sol était mou et saturé en eau. Ces caractéristiques suggèrent ou indiquent que les traces concrétionnaires sont desmoules d’empreintes de pas formés par le remplissage, par de l’eau souterraine riche en carbonates dissous, de dépressions laisséesdans le substrat mou. Alors que l'eau accumulée s'évaporait, des minéraux commencèrent a se précipiter et a se mélanger avec desparticules clastiques transportées dans les dépressions, le tout se déposant sous forme de fines laminations au sein des empreintes,remplissant partiellement ou entièrement ces dernières. La composition géochimique du précipité dépendait des conditions de l’eausouterraine (p. ex. pH, concentrations de carbonate et de sulfate dissous). La cimentation des empreintes s’est produite peu aprèsl’enfouissement (<100 ans), possiblement en réponse a l’activité microbienne et leur saturation par l’eau souterraine riche enminéraux, et l’érosion moderne a exposé les empreintes concrétionnaires en érodant la roche encaissante plus meuble. La reconnais-sance de ce nouveau type d’ichnofossiles suggère ou indique que les empreintes de dinosaures pourraient être plus répandues queprévu. Malheureusement, les empreintes concrétionnaires ont tendance a se désagréger rapidement lorsque le substrat qui lesenglobe et les sous-tend est érodé, modifiant ainsi leur forme diagnostique et les rendant impossibles a distinguer de concrétions nonichnogènes. Les empreintes concrétionnaires pourraient donc constituer des ichnofossiles transitoires dans les badlands, ce quiexpliquerait pourquoi elles sont rarement reconnues.

Received 1 October 2014. Accepted 12 January 2015.

Paper handled by Associate Editor Hans-Dieter Sues.

F. Therrien. Royal Tyrrell Museum of Palaeontology, Box 7500 Drumheller, AB T0J 0Y0, Canada.D.K. Zelenitsky and K. Tanaka. Department of Geoscience, University of Calgary, 2500 University Drive NW, Calgary, AB T2N 1N4, Canada.A. Quinney.* School of Earth, Atmosphere and Environment, Monash University, Clayton, Victoria 3800, Australia.Corresponding author: François Therrien (e-mail: francois.therrien@gov.ab.ca).*Present address: Arctic Institute of North America, University of Calgary, 2500 University Drive NW, Calgary, AB T2N 1N4, Canada.1This article is one of a selection of papers published in this Special Issue commemorating the 30th anniversary of the Royal Tyrrell Museum ofPalaeontology.

630

Can. J. Earth Sci. 52: 630–641 (2015) dx.doi.org/10.1139/cjes-2014-0168 Published at www.nrcresearchpress.com/cjes on 5 August 2015.

Can

. J. E

arth

Sci

. Dow

nloa

ded

from

ww

w.n

rcre

sear

chpr

ess.

com

by

Alb

erta

Gov

ernm

ent L

ibra

ry o

n 08

/05/

15Fo

r pe

rson

al u

se o

nly.

IntroductionDinosaur tracks are widely distributed across western Canada.

They have been reported in Upper Jurassic through uppermostCretaceous rock formations, even as float material in Pleistocenegravels, from Alberta, British Columbia, and Yukon (Currie 1989;Sampson and Currie 1996; Long et al. 2000; McCrea et al. 2014a).Although few track localities were known prior to 1975 (McLearn1923; Sternberg 1926, 1932; Langston 1960; Storer 1975), theirnumbers increased dramatically in the 1980s when the Royal Tyr-rell Museum, under the guidance of Dr. Philip Currie, conductedan exhaustive survey of dinosaur tracksites (Currie 1989). Sincethen, several new Canadian dinosaur tracksites have been discov-ered and described (McCrea and Currie 1998; McCrea 2003;Gangloff and May 2004; Tanke 2004; McCrea and Buckley 2005;McCrea et al. 2005, 2014a, 2014b; Rylaarsdaam et al. 2006; Lockleyet al. 2009; Fanti et al. 2013; Therrien et al. 2014).

Most dinosaur tracks in western Canada occur as depressionson the surface of sandstone beds or as natural casts on the under-surface of sandstones (see Currie 1989; Currie et al. 1991; McCreaet al. 2014a). While some rock formations preserve dinosaurtracks in great abundance (e.g., St. Mary River Formation; Currieet al. 1991; Nadon 1993), other formations are surprisingly depau-perate in tracks despite being rich in vertebrate fossil remains(e.g., Oldman and Dinosaur Park formations; Currie 1989). Thisapparent paucity of dinosaur tracks may actually reflect preserva-tion and collecting biases, as numerous tracks preserved as sider-itic and calcareous concretions were recently discovered in theseformations (McCrea et al. 2005; Therrien et al. 2014). This type ofichnofossil, hereafter referred to as concretionary tracks, differsdramatically from typical dinosaur tracks discovered around theworld, except for two similar occurrences reported in Montana,USA (Triebold et al. 1999; Manning et al. 2008; Lockley et al. 2014).Consequently, concretionary tracks must have a mode of forma-tion and preservation distinct from that of the more commonlyfound tracks.

Dinosaur concretionary tracksites from the Oldman and Dino-saur Park formations of southern Alberta were investigated sedi-mentologically, petrographically, and geochemically to elucidatethe process by which they formed. The results reveal a new modeof preservation for dinosaur tracks and indicate that concretion-ary tracks may be a common, although rarely recognized, type ofichnofossils worldwide.

Geologic settingThe concretionary tracks studied are located in the Milk River

Natural Area (MRNA) and Dinosaur Provincial Park (DPP) of south-ern Alberta (Fig. 1). They are preserved in exposures of the BellyRiver Group (formerly referred to as the Judith River Group;Eberth and Hamblin 1993), which comprises the Foremost, Old-man, and Dinosaur Park formations. In the MRNA, the Foremostand Oldman formations are predominant while the DinosaurPark Formation is limited in distribution due to the wedge-shapedstratigraphic architecture of the formation in southernmostAlberta (Eberth and Hamblin 1993). In DPP, rock exposures arerestricted to the uppermost Oldman Formation and the DinosaurPark Formation (Eberth 2005). Due to the stratigraphic architec-ture of the Belly River Group and the time-transgressive nature ofthe contact between the Oldman and Dinosaur Park formations,the upper part of the Oldman Formation in the MRNA is time-equivalent to the Dinosaur Park Formation exposed in DPP(Eberth and Hamblin 1993; Eberth 2005).

The Oldman Formation in southernmost Alberta exceeds 160 min thickness and consists of interbedded sandstones, siltstones,and mudstones deposited by ephemeral, low-sinuosity rivers(Eberth and Hamblin 1993). Deposition under a semi-arid to aridclimate characterized by seasonal precipitation is indicated by thepresence of paleosols containing carbonate nodules and slicken-

sides (Eberth and Hamblin 1993). Radiometric dating of volcanicash deposits has revealed that the upper Oldman Formation ofsouthern Alberta was deposited between 76.2 and 74.9 Ma (Eberthand Hamblin 1993).

The Dinosaur Park Formation exposed in DPP is approximately70 m thick and consists of interbedded sandstones, siltstones, andmudstones deposited in perennial, high-sinuosity fluvial settingsand paralic environments (Eberth 2005). The absence of carbonatenodules has been interpreted as evidence of deposition under amore humid climate, although sedimentological and paleontolog-ical features suggest seasonal precipitation (Eberth and Hamblin1993; Eberth 2005). Radiometric dating of volcanic ash depositsindicate that the Dinosaur Park Formation in DPP was depositedbetween 76.5 and 74.8 Ma (Eberth 2005).

Materials and methodsConcretionary tracks were documented in terms of geographic

and stratigraphic location, morphology, composition, and sedi-mentologic setting. Morphometric variables useful for taxonomicidentification of the track maker (e.g., length, divarication, andinterdigital angles, Fig. 2; Moratalla et al. 1988; Romilio andSalisbury 2011) were measured on the original tracks or on dig-ital photographs using the software ImageJ version 1.41o. Photo-graphs were adjusted for brightness and contrast using thesoftware Photoshop CS6. Samples from the tracks and lithologicalunits were collected for petrographic study and bulk X-ray diffrac-tometry (XRD) analysis. XRD analysis was conducted on a RigakuMiniflex II X-ray diffractometer at Calgary Rock and MaterialsServices Inc., Calgary, Alberta.

Concretionary tracks of the Belly River GroupThree concretionary tracksites (Fig. 1) were documented in the

context of this investigation: (i) a hadrosaur trackway located inthe upper member of the Oldman Formation, about 25 m abovethe Comrey Sandstone, in the Milk River Natural Area (MRNAtracksite; see Therrien et al. 2014); (ii) a previously reported had-rosaur trackway from DPP (“tracksite near Q128” of McCrea et al.2005), hereafter referred to as the McCrea trackway, located ap-proximately 5 m above the Oldman–Dinosaur Park formationalcontact; and (iii) a dinosaur trackway discovered in DPP during thesummer 2011, hereafter referred to as the DH3 tracksite, locatedapproximately 20 m above the Oldman–Dinosaur Park contact.The morphology and sedimentological setting of the MRNA track-way has been described in details elsewhere (Therrien et al. 2014),so these aspects will only be discussed briefly. Consequently em-phasis will be placed on the McCrea trackway and the previouslyundocumented DH3 trackway.

Trackway morphologyThe MRNA trackway consists of a series of seven consecutive

and one isolated brown concretions. Three of the concretionspreserve the diagnostic tridactyl pedal shape (Figs. 3A–3C; Table 1),whereas the remaining are amorphous due to heavy weathering(Fig. 3D) and indistinguishable from concretions commonly foundin the Oldman Formation. The tracks are robust with blunt digittermination and exhibit a possible bilobed posterior margin, com-monly seen in large Cretaceous ornithopods from North America(Currie et al. 1991, 2003; Lockley and Hunt 1995; Lockley et al.2004). The tracks do not preserve details of the track maker (e.g.,skin impression). Based on their morphology (Table 2), the tracksare inferred to have been produced by a large hadrosaur ap-proaching 3.4 m at the hip (Therrien et al. 2014).

The McCrea trackway consists of a linear arrangement of regu-larly spaced black, weathered concretions exposed on a flat sur-face between buttes: eight concretions are aligned along the sidea low-ridge and a ninth concretion is located on the other side ofthe ridge (Fig. 1C). Two concretions situated 10 m farther north are

Therrien et al. 631

Published by NRC Research Press

Can

. J. E

arth

Sci

. Dow

nloa

ded

from

ww

w.n

rcre

sear

chpr

ess.

com

by

Alb

erta

Gov

ernm

ent L

ibra

ry o

n 08

/05/

15Fo

r pe

rson

al u

se o

nly.

aligned with the trackway and potentially represent additionaltracks (Figs. 1C, 4A). Although McCrea et al. (2005) noted that someconcretions were clearly recognizable as footprints in the courseof their 2003 field investigation (Figs. 4A, 4C, 4E), only one concre-tion (the ninth) retained a recognizable track shape when wedocumented the site in 2011 (Figs. 1, 4F). The remaining tracks areheavily weathered and broken (Figs. 4B, 4D), rendering them in-distinguishable from sideritic concretions regularly occurringwithin the Dinosaur Park Formation. The trackway is narrow,oriented to the south-west (219o), and can be traced over a distanceof nearly 40 m. The single well-preserved track, located on the

other side of the ridge from the main trackway, has a differentorientation and points to the south (169o). Comparison with aphotograph taken by McCrea et al. (2005) reveals that parts of thetrack have been lost to erosion (e.g., digits II and IV), but its gen-eral morphology has been preserved (Figs. 4E, 4F; see also differ-ences in measurements in Table 1). Overall, the McCrea track issimilar to the MRNA tracks: it is robust with blunt digit termina-tion, longer than wide (length = 59 cm, width � 53 cm, l/w ratio =1.11, but length �60 cm, width �60 cm, l/w ratio �1 based onMcCrea et al. (2005, fig. 21.12)), and up to 17 cm thick (Fig. 4;Table 1). Details of the track maker (e.g., skin impression) are not

Fig. 1. Location of studied concretionary tracks. Inset shows location of Milk River Natural Area (MRNA) and Dinosaur Provincial Park (DPP)in Alberta. (A) Location of hadrosaur trackway in MRNA (black outline). Modified from Therrien et al. (2014), courtesy of Indiana UniversityPress. (B) Location of two hadrosaur trackways in DPP (black outline). (C) Distribution of concretionary tracks at McCrea (white) and DH3(black) trackways. Footprint outline represents recognizable (i.e., high-fidelity) three-toed track. Circles are low-fidelity or weatheredconcretionary tracks. Triangles are potential low-fidelity concretionary tracks. Rectangle represents portion of McCrea trackway illustrated inFig. 4A. Due to the close proximity of two concretions in the middle of the DH3 trackway, they are represented by a single circle in (C).

632 Can. J. Earth Sci. Vol. 52, 2015

Published by NRC Research Press

Can

. J. E

arth

Sci

. Dow

nloa

ded

from

ww

w.n

rcre

sear

chpr

ess.

com

by

Alb

erta

Gov

ernm

ent L

ibra

ry o

n 08

/05/

15Fo

r pe

rson

al u

se o

nly.

preserved. Due to the incompleteness of the track, the interdigitalangles can only be estimated. The total divarication angle of digitsII–IV is similar to that of the MRNA tracks at approximately 65o,but the interdigital angles differ slightly in that the digits II–IIIangle (30o) is slightly smaller than that of digits III–IV (35o). Unlikethe MRNA tracks, the McCrea track does not exhibit a bilobedposterior margin. Morphometric variables predominantly sup-port an ornithopod affinity for the track maker (Table 2), in agree-ment with the interpretation of McCrea et al. (2005). Based on therelationship between track size and leg length in large ornitho-pods (Thulborn 1990), the McCrea track maker is estimated tohave measured approximately 3.5 m at the hip, consistent with alarge hadrosaur exceeding 10 m in length (see Therrien et al. 2014).

The DH3 tracksite consists of a series of seven semi-regularlyspaced, rusty concretions exposed in cross-section in the wall of abutte (Figs. 1C, 5A) along the access road leading to Display House#3 (which shelters a skeleton of Corythosaurus casuarius, TMP1980.23.4, collected at nearby Quarry 128). The trackway is ori-ented to the south (166o) and can be traced over a distance ofnearly 20 m. Given that each pair of concretions seems to beslightly laterally offset relative to the previous one (see Fig. 1C), itis possible that the DH3 trackway was produced by several indi-viduals; unfortunately this is impossible to ascertain given thepreservation conditions of the concretions. Although most con-cretions are amorphous masses that do not bear resemblance totracks, one of them is a partially cemented three-toed pedal trackthat gradually transitions into a plastically deformed depressionin fine-grained sandstone (Figs. 1C, 6). The track is robust, longerthan wide (length = 69 cm, width �70.5 cm, l/w ratio = 0.98), and15 cm thick (Table 1). The concretionary track exhibits blunt digittermination, but the nonconsolidated portion displays a morepointed digit termination (Fig. 6), presumably resulting from plas-tic sediment deformation. The total divarication angle of digitsII–IV (�52o) is smaller than that of the MRNA and McCrea tracksand the interdigital angle of digits II–III (25o) is subequal to that ofdigits III–IV (27o). The irregularity of the posterior margin of thetrack, complicated by the partially cemented nature of the track,makes it difficult to determine if the postero-lateral portion ofthe concretion truly represents a “heel protuberance”. The trackpreserves no details of the track maker (e.g., skin impression).

Morphometric variables predominantly support an ornithopodaffinity for the track maker (Table 2). Following the foot/leg rela-tionship described above, the DH3 track maker is estimated tohave measured approximately 4 m at the hip. This high estimatecould reflect an unusually large individual or be an artifact in-duced by an overestimated track size due to the poorly definedposterior margin of the track.

Due to the incomplete nature of the DPP trackways, walkingspeed estimates, derived following the method of Alexander(1976), can only be approximated. At the McCrea tracksite, dis-tance could be determined between two pairs of consecutive con-cretions, which provide estimated pace lengths of 155 cm (at midtrackway) and 185 cm (at the end of the trackway). Conversion ofpace length into strides reveals that the McCrea track makerwalked at a speed varying between 4.32 (SL/h = 0.89) and 5.83 km/h(SL/h = 1.06). Assuming that the DH3 trackway was produced by asingle individual, spacing between a series of four consecutiveconcretions vary between 240 and 330 cm, providing walkingspeed estimates ranging between 9.04 (SL/h = 1.29) and 9.72 km/h(SL/h = 1.34).

Sedimentological setting of the tracksitesThe MRNA tracks are exposed at the surface of a drab-colored

mudstone. Field investigation revealed the tracks are hosted within alight gray sandy siltstone that overlies the drab-colored mudstone.Petrographic study reveals the presence of soft-sediment defor-mation, root traces, and redoximorphic features within the hostsiltstone (Fig. 7B). All of these features are indicative of trackformation at the top of a poorly drained, hydromorphic paleosolsubject to a fluctuating watertable (see Therrien et al. 2014).

The McCrea tracks are exposed at the surface of a light gray,fine-grained, horizontally laminated sandstone. Investigation ofthe surrounding outcrops reveals that the tracks occur at the topof this sandstone unit, such that erosion of the sandstone resultedin exposure of the tracks. Petrographic study reveals that thesandstone is characterized by an abundance of distorted andconvoluted laminations (Fig. 7A), indicative of soft-sediment de-formation.

Exposed in cross-section, the DH3 tracks occur at the top of alaterally extensive, multi-meter thick, fining-upward channelsequence (Fig. 5A). The lower part of the sequence consists ofmedium- to large-scale trough cross-stratified sandstone with sid-erite pebbles lining foresets and the base of troughs, whereas theupper part is a horizontally laminated interval of interbeddedorganic matter, siderite, and sandstone laminae. This channelsequence is overlain by a multi-meter thick, structureless silt-stone and mudstone unit interpreted as overbank deposits. Thetracks and amorphous concretions occur consistently at the topof the horizontally laminated sandstone and are directly overlainby the overbank deposits. Each concretion is directly underlain bydisrupted and depressed laminations (i.e., load structures), indic-ative of soft-sediment deformation (Figs. 5B, 5C). The bestpreserved DH3 track also shows evidence of soft-sediment defor-mation in plan view, where laminae of the host sandstone aredisrupted and pushed down into the depression of the non-cemented toe print (Fig. 5D).

Internal structure and composition of the tracksDespite obvious external differences between the MRNA and

DPP concretionary tracks (e.g., color), their internal structure aresurprisingly similar. All concretionary tracks are made of a micro-crystalline sparry carbonate matrix with dispersed sand grainsthat exhibit internal horizontal or convoluted laminations (Figs. 7C–7E).While these laminations are visible macroscopically in the MRNAtracks, they are hardly noticeable in the DPP tracks. It is in termsof their geochemical composition that the tracks differ the most:the MRNA tracks are composed of calcium carbonates (dolomiteand calcite), whereas the DPP tracks are composed primarily of

Fig. 2. Morphometric variables used to determine the taxonomicidentity of dinosaur tracks. L, track length; W, track width; L2–L4,whole digit lengths; BL2–BL4, basal digit lengths; WB2–WB4, basaldigit widths; WM2–WM4, middle digit widths; K and M, heel-to-interdigit lengths. Modified from Therrien et al. (2014), courtesy ofIndiana University Press.

Therrien et al. 633

Published by NRC Research Press

Can

. J. E

arth

Sci

. Dow

nloa

ded

from

ww

w.n

rcre

sear

chpr

ess.

com

by

Alb

erta

Gov

ernm

ent L

ibra

ry o

n 08

/05/

15Fo

r pe

rson

al u

se o

nly.

Fig. 3. Representative hadrosaur concretionary tracks from the Milk River Natural Area (MRNA) trackway. (A–C) Photograph and schematicrepresentation (grey) of tracks with hypothesized outline of complete track (dash line). (D) Photograph and schematic representation (grey) ofheavily weathered and broken track. Scale bar = 10 cm. Modified from Therrien et al. (2014), courtesy of Indiana University Press.

Table 1. Measurements of concretionary tracks (in centimetres). Values in parentheses are derivedfrom McCrea et al. (2005, fig. 21.12).

Morphometricvariable

McRae(left)

DH3(right)

MRNA track A(left)

MRNA track B(right)

MRNA track C(right)

L 59 (�60) 69 52.5 58 �52W 53 (�60) �70.5 39 (min.) 54 �47K 40 (�40) 51.8 37 37 31.2M 42.3 (�41) 50.5 37.4 35.6 ?BL2 4 (�8) 15.1 10.5 ? 9WM2 6.3 (�6.5) 10.2 11.8 ? 7BL4 ? (�15) 10.5 ? ? ?WM4 ? (�11) 10.1 ? ? ?BL3 17.8 (�21) 21.3 12.2 19.7 16.2WM3 9.7 (�13) 10.5 11.7 12.4 7.8L2 45.5 (�49) 67.4 48.1 ? 40.7WB2 10.2 (�10.8) 13.3 14.6 14.8 12.3L4 ? (�57) 61.1 ? ? ?WB4 ? (�23.5) 17.2 ? 14.8 ?L3 59 (�60) 70.7 50.4 53.61 45.6WB3 24.5 (�24.5) 32.9 16 21.4 19.5

Note: See Fig. 2 for explanation of morphometric variables.

Table 2. Morphometric variables used to differentiate ornithopod and theropod tracks.

Morphometricvariable

Threshold value and associatedprobability that track belongsto theropod or ornithopod McCrea DH3

MRNAtrack A

MRNAtrack B

MRNAtrack C

L/W 80% theropod > 1.25 > 88.2% ornithopod 1.11 (�1) 0.98 ? 1.07 ?L3/K 70.5% theropod > 2.00 > 88% ornithopod 1.48 (�1.5) 1.33 1.36 1.45 1.46L3/M 65% theropod > 2.00 > 90.7% ornithopod 1.40 (1.46) 1.37 1.35 1.51 ?BL2/WM2 76.1% theropod > 2.00 > 97.7% ornithopod 0.64 (1.23) 1.48 0.89 ? 1.29*BL4/WM4 76.1% theropod > 2.00 > 97.7% ornithopod ? (1.36) 1.04 ? ? ?BL3/WM3 72.7% theropod > 2.20 > 97.7% ornithopod 1.84 (1.62) 2.03 1.04† 1.59 2.08*L2/WB2 84.6% theropod > 3.75 > 90.2% ornithopod 4.46‡ (4.54‡) 4.77‡ 3.30 ? 3.31L4/WB4 73.7% theropod > 3.75 > 93.4% ornithopod ? (2.43) 3.73 ? ? ?L3/WB3 70.6% theropod > 4.00 > 91.5% ornithopod 2.41 (2.45) 2.10 3.15† 2.51 2.34*

Note: Variables, threshold values, and probability values of ornithopod or theropod affinity are from Moratalla et al. (1988). See Fig. 2for explanation of morphometric variables. Values in parentheses are derived from McCrea et al. (2005, fig. 21.12). Values for MRNAtracks are from Therrien et al. (2014).

*Maximum value due to incompleteness of track.†Minimum value due to incompleteness of track.‡Value within the theropod range.

634 Can. J. Earth Sci. Vol. 52, 2015

Published by NRC Research Press

Can

. J. E

arth

Sci

. Dow

nloa

ded

from

ww

w.n

rcre

sear

chpr

ess.

com

by

Alb

erta

Gov

ernm

ent L

ibra

ry o

n 08

/05/

15Fo

r pe

rson

al u

se o

nly.

siderite (Table 3). Clastic particles (e.g., quartz, plagioclase, potas-sium feldspars, illite) also occur in small amount in the tracks.

Comparison of Belly River concretionary tracks with otherdinosaur tracks

Most dinosaur tracks occur as depressions on the surface ofsedimentary beds or as casts on the undersurface of beds. Bycontrast, the Belly River concretionary tracks occur as casts on thesurface of a sedimentary unit and have a different lithologicalcomposition than their host unit (i.e., chemical concretion versusclastic rock). Although examples of three-dimensional dinosaur

track casts exposed on top of sedimentary bed have been previ-ously reported elsewhere (e.g., Kuban 1989; Huerta et al. 2012),their composition is similar to that of the surrounding rocks and,therefore, these tracks are not considered concretionary tracks.

Only two occurrences of tracks that resemble the Belly Riverconcretionary tracks have been previously reported, both fromthe uppermost Cretaceous Hell Creek Formation of the UnitedStates: (i) a trackway consisting of 16 consecutive tracks left bya large, gracile theropod, possibly a tyrannosaurid, in HardingCounty, South Dakota (Triebold et al. 1999; Lockley et al. 2014); and

Fig. 4. McCrea hadrosaur tracksite. (A) Photograph (looking northeast) showing linear arrangement of concretionary tracks (blackarrowheads). Potential concretionary tracks occur in the background (white arrowheads). Track identified by McCrea et al. (2005, fig. 21.13) butunrecognizable in 2011 is indicated by asterisk. Tracks identified as “badly eroded footprint remnants” in McCrea et al. (2005, fig. 21.14) andunrecognized in 2011 are indicated by hollow arrowheads. (B) Photograph of heavily weathered track. (C) Photograph of hadrosaur trackillustrated in McCrea et al. (2005, fig. 21.13). (D) Photograph of track illustrated in (C) as it appeared in 2011. The track has collapsed and isunrecognizable. (E) Photograph of hadrosaur track illustrated in McCrea et al. (2005, fig. 21.12). (F) Photograph of track illustrated in (E) as itappeared in 2011. This is the only surviving track at the site. Photographs (C) and (E) are reproduced courtesy of Rich McCrea and IndianaUniversity Press. All rights reserved.

Therrien et al. 635

Published by NRC Research Press

Can

. J. E

arth

Sci

. Dow

nloa

ded

from

ww

w.n

rcre

sear

chpr

ess.

com

by

Alb

erta

Gov

ernm

ent L

ibra

ry o

n 08

/05/

15Fo

r pe

rson

al u

se o

nly.

(ii) an isolated, large theropod track, attributed to Tyrannosaurusrex, in Carter County, Montana (Manning et al. 2008). Both HellCreek occurrences consist of sideritized concretionary trackshosted within mudstones. Although the South Dakota tracks areunique in preserving claw impressions, the Hell Creek and BellyRiver tracks are otherwise similar in preserving only the generalpedal morphology and in lacking details of the track maker, suchas skin impression or phalangeal pad imprints (Manning et al.2008; Lockley et al. 2014). Based on their preservation style, theSouth Dakota tracks have been interpreted as three-dimensionalcasts of depressions left by an animal walking through soft, cohe-sive mud (Lockley et al. 2014). Although the mode of formation ofthe casts was not discussed, similarities in preservation style, geo-chemical composition, and sedimentological context between theHell Creek and Belly River concretionary tracks, particularly theDPP tracks, suggest that they all formed in a similar fashion.

Mode of formation of concretionary tracksThe sedimentological and pedological features of the three

Belly River tracksites indicate that the paleoenvironments in

which the tracks formed were characterized by a high watertable.The MRNA tracks are underlain by a drab green mudstone and arehosted within a rooted siltstone that contains clay coatings, re-doximorphic features, and evidence of soft-sediment deformation(Fig. 7B). Together, these pedogenic features reveal the MRNAtracks formed at the top of a gleyed, hydromorphic paleosol char-acterized by a high, but fluctuating watertable (Daniels et al.1971; Vepraskas 1992; PiPujol and Buurman 1994; Vepraskas andCaldwell 2008). In comparison, both DPP trackways occur at thetop of channel sandstones in an interval that displays abundantevidence of soft-sediment deformation. These sedimentologicalfeatures indicate the DPP tracks formed near the shore of a riverin a soft, water-saturated substrate.

Based on the paleoenvironmental setting, internal structure,and geochemical composition of the MRNA and DPP tracks, ascenario can be proposed for the formation of concretionary tracks.As dinosaurs walked on a water-saturated, soft substrate (e.g.,wetland, river shore), their feet sank into the substrate, creatingdepressions and disturbing pre-existing sedimentary structures

Fig. 5. DH3 hadrosaur tracksite. (A) Photograph of trackway exposed in cross-section along the wall of a butte. Concretionary tracks (blackarrowheads) occur at the top of a multi-meter channel sequence. Second concretion from the left is the well-preserved track (see Fig. 6). Scalebar = 2 m. (B) Photograph showing soft-sediment deformation below the concretionary tracks. Concretion on the right is well-preserved track(see Fig. 6). Scale bar = 50 cm. (C) Extensive soft-sediment deformation below concretionary track. Scale bar = 10 cm. (D) Soft-sedimentdeformation surrounding toe impression. Horizontal bedding planes are either dipping gently towards the toe impression (white arrowheads)or sharply tilted to expose cross-section of sedimentary structures at the surface (black arrowheads). White fill represents cemented part oftrack, dash line is outline of footprint impression in sandstone. Scale bar = 5 cm.

636 Can. J. Earth Sci. Vol. 52, 2015

Published by NRC Research Press

Can

. J. E

arth

Sci

. Dow

nloa

ded

from

ww

w.n

rcre

sear

chpr

ess.

com

by

Alb

erta

Gov

ernm

ent L

ibra

ry o

n 08

/05/

15Fo

r pe

rson

al u

se o

nly.

(Fig. 8A). Based on the cohesive properties of the substrate, theshape of the foot could be preserved in the substrate, forming a“high-fidelity track”, or be lost and turn into an amorphous de-pression or “low-fidelity track” (Fig. 9). Due to the high watertablein the area, the depressions filled, either fully or in part, withwater (Figs. 8B, 9). Over time, as the tracks dried and ponded waterevaporated, dissolved carbonates in the groundwater began to pre-cipitate in the depressions. Based on the prevalent groundwaterconditions (pH, dissolved carbonate and sulphate concrentra-tions; see Pye et al. 1990, Browne and Kingston 1993), carbonatesprecipitated either in the form of calcium carbonates (at MRNA) oriron carbonate (in DPP). Precipitating carbonates mixed with clas-tic particles (sand and clay), brought by wind, rain or slow-flowingwater, to gradually form a finely laminated mud deposit thatpartially or entirely filled the tracks (Fig. 8C). After track infillingwas complete, fluvial sedimentation buried the tracks under over-bank deposits and bioturbation took place (Fig. 8D). Cementationof the infilled tracks occurred relatively soon after burial, possiblyin response to microbial activity and saturation by mineral-richgroundwater (Fig. 8E), and the resulting concretions preservedcasts of the original footprint impression. Millions of years later,differential erosion exposed the concretionary tracks by remov-ing the softer overlying and encasing sediment (Fig. 8F).

The amount of time involved in the formation of concretionarytracks is difficult to determine but can be constrained based ongeological and geochemical evidence. Given the presence of roundedsiderite nodules and collapsed sideritized cutbank blocks in channeldeposits of the Dinosaur Park Formation (Eberth 2005) and of cal-cium carbonate nodules as channel lags in the Oldman Formation(F. Therrien, pers. observ.), it is clear that these minerals precipi-tated near the surface, prior to burial diagenesis of the fluvialdeposits. Such early syndepositional lithification would have oc-curred prior to aggradation of the fluvial system, events that occuron a timescale ≥ 10 000 years (see Miall 1992). Field investigationshave demonstrated that authigenic siderite and Mg-rich calcitecan precipitate as a result of microbial decomposition of organicmatter, under low sulphate conditions, in as little as six months(Pye et al. 1990). Furthermore, the presence of primary sedimen-tary structures (i.e., laminations) within the tracks argues for theirrapid lithification as pervasive bioturbation would have other-wise erased them. Consequently, cementation of the concretion-ary tracks likely occurred relatively soon (i.e., <100 years) aftertheir burial.

As none of the Belly River concretionary tracks preserve skin orphalangeal pad impressions, it is unknown if this new track typehas the potential to preserve fine details of the track maker. In thetwo cases of Hell Creek concretionary tracks, claw impressions areonly preserved in the South Dakota tracks, and neither preservesskin or phalangeal pad impressions (Manning et al. 2008; Lockleyet al. 2014). Although the proposed scenario of track formationdoes not preclude preservation of fine details, their presenceor absence may be related to a combination of factors, such asthe cohesive properties of the host sediment and the state ofpreservation of the concretionary tracks at the time of theirdiscovery.

The proposed mode of formation for concretionary tracks dif-fers from the scenario for the formation of typical track casts,which are generally inferred to result from clastic sediment fillingdepressions following a depositional event (e.g., Lockley 1991;Huerta et al. 2012). Concretionary track formation is more similarto the model proposed by Kuban (1989) for Early Cretaceous dino-saur tracks discovered at the Taylor Site near Glen Rose, Texas. Inhis model, footprints are left in a calcitic mud and are infilled withclay that becomes dolomitized in response to “water depth, waterchemistry, microbial activity, and (or) other factors” (Kuban 1989,p. 438). Given the petrographic and geochemical similarity be-tween the infill material and host substrate at the Taylor Site, it islikely that a depositional event (e.g., flooding) is responsible for

Fig. 6. Photograph and schematic representation of DH3 track.Gray outline represents portion of track preserved as concretion anddash line represents portion of track preserved as depression in fine-grained sandstone. Scale bars = 10 cm.

Therrien et al. 637

Published by NRC Research Press

Can

. J. E

arth

Sci

. Dow

nloa

ded

from

ww

w.n

rcre

sear

chpr

ess.

com

by

Alb

erta

Gov

ernm

ent L

ibra

ry o

n 08

/05/

15Fo

r pe

rson

al u

se o

nly.

transporting the material that infilled those tracks. In contrast,the infill material forming the Belly River concretionary tracksdiffers dramatically from typical alluvial lithologies found inthese formations (except for chemical precipitates, i.e., sideriteand calcite). Thus the formation of concretionary tracks mostlikely reflects the greater influence of groundwater ponding andchemical precipitation within the footprint depression than ex-ternal sediment input, a hypothesis supported by the scarcity ofclastic grains present in the tracks (see Table 3).

This novel scenario predicts that concretionary tracks shouldform predominantly in poorly drained paleoenvironments char-acterized by a high, but fluctuating, watertable rich in dissolvedminerals. This new type of dinosaur tracks could potentially befound in rock formations that preserve syndepositional concre-tions and evidence of poorly drained paleoenvironments. Indeed,the presence of concretionary tracks in the Hell Creek Forma-tion (Triebold et al. 1999; Manning et al. 2008; Lockley et al.2014), a rock formation characterized by waterlogged paleosols(e.g., Fastovsky and McSweeney 1987; Retallack 1994), lends sup-port to this interpretation. Thus this new scenario suggests thatdinosaur tracks may be more widespread than previously recog-nized, especially in mudstone-dominated rock formations (seeLockley et al. 2014).

Preservation potential of concretionary tracksAlthough concretionary tracks are more resistant than the host

sediment, they can be subject to rapid weathering and erosion asindividual tracks become fractured and fragmented once ex-posed. For example, the MRNA tracks found during the summer2006 were barely recognizable two years later and some of theDPP tracks reported by McCrea et al. (2005) had become unrecog-nizable masses by the summer 2011 (Figs. 4A, 4D). Inspection ofthe McCrea trackway in 2014 revealed that it is the erosion anddeflation of the encasing and underlying sediment rather thanweathering of the concretions themselves that lead to the fractureand collapse of tracks. As such, concretionary tracks are probablytransient ichnofossils that degrade into amorphous concretionsand escape recognition. In contrast, the well-preserved nature ofthe South Dakota concretionary tracks possibly reflects the factthat most were still encased in bedrock at the time of their dis-covery (Lockley et al. 2014).

Given the abundance of concretions scattered throughoutbadlands, often concentrated within specific stratigraphic in-tervals, it is plausible that some of them may represent low-fidelity dinosaur tracks or heavily weathered tracks that havelost their diagnostic morphology. For example, a large numberof regularly spaced sideritic concretions, each underlain by

Fig. 7. Photomicrographs of concretionary tracks and host sediment. (A) Extensive soft-sediment deformation in host sediment at McCreatracksite. (B) Soft-sediment deformation (ss), root traces (rt), and redoximorphic features (rd) in host sediment at Milk River Natural Area(MRNA) tracksite. Modified from Therrien et al. (2014), courtesy of Indiana University Press. (C) Convoluted laminations in McCrea track.(D) Horizontal and convoluted laminations (black arrowheads) in MRNA track. (E) Burrow (b) and horizontal/undulating laminations (blackarrowheads) in MRNA track. Scale bars = 5 mm. (D) and (E) were photographed against a light brown background to emphasize sedimentarystructures.

Table 3. Geochemical composition of concretionary tracks (in %weight).

Tracksite Siderite Calcite Dolomite Quartz Plagioclase K-feldspar Illite

McCrea 71 10 — 10 9 — —MRNA — 3–17 39–44 23 9–12 5–6 7–12

638 Can. J. Earth Sci. Vol. 52, 2015

Published by NRC Research Press

Can

. J. E

arth

Sci

. Dow

nloa

ded

from

ww

w.n

rcre

sear

chpr

ess.

com

by

Alb

erta

Gov

ernm

ent L

ibra

ry o

n 08

/05/

15Fo

r pe

rson

al u

se o

nly.

soft-sediment deformation, occur in the same horizon as theDH3 trackway (Figs. 4C, 10), which lends support to this possi-bility. In such instances, the linear arrangement and regularspacing of concretions, combined with the occurrence of soft-sediment deformation (i.e., load structures), may be the onlyway to differentiate low-fidelity or highly weathered concre-tionary tracks from randomly occurring concretions.

ConclusionsAlthough dinosaur tracks are generally considered uncommon

in Upper Cretaceous deposits of southern Alberta, a new type ofichnofossil, herein referred to as concretionary tracks, suggeststhat tracks may be more widespread than previously thought.Study of the sedimentological, petrographic, and geochemicalcharacteristics of three tracksites revealed that concretionary

Fig. 8. Scenario for the formation and preservation of concretionary tracks. As the dinosaur stepped onto the soft, water-saturated substrate,it created a depression that disrupted underlying sedimentary structures (A). As it extracted its foot, the watertable filled the depression,either partly or completely (B). Based on substrate properties, the depression either preserved accurately the morphology of the foot (high-fidelity track) or lost all resemblance (low-fidelity track). Over time, carbonate mud precipitated out of the mineral-rich watertable and clasticparticles were transported into the depression (C). The trampled surface was later buried under sediment and bioturbation took place (D).After burial, the material filling the depression was transformed into a concretion, presumably due to the mineral-rich watertable andmicrobial activity, creating a cast of the track (E). Modern erosion removed the softer sediment and exposed the concretionary track (F).

Fig. 9. Trampled surface near flowing stream showing diversity of footprints produced: from high-fidelity to low-fidelity tracks and fromtracks completely filled with water to tracks devoid of water. Photograph courtesy of Brent Kuntz.

Therrien et al. 639

Published by NRC Research Press

Can

. J. E

arth

Sci

. Dow

nloa

ded

from

ww

w.n

rcre

sear

chpr

ess.

com

by

Alb

erta

Gov

ernm

ent L

ibra

ry o

n 08

/05/

15Fo

r pe

rson

al u

se o

nly.

tracks form in wet paleoenvironments, where the ground is softand water saturated. Whereas all concretionary tracks displayinternal horizontal to convoluted laminations, they differ in theirgeochemicalcomposition: theMRNAtracksarepredominantlymadeofcalcium carbonate, whereas the DPP tracks are made of siderite.

Based on the sedimentological setting and internal structure ofthe tracks, a scenario is proposed for the formation of concretion-ary tracks. As dinosaurs walked on a soft, water-saturated sub-strate, footprints could be preserved either as well-defined tracks(i.e., high-fidelity tracks) or amorphous depressions (i.e., low-fidelity tracks) based on the cohesive properties of the substrate.These footprints were flooded by mineral-rich groundwater and,as the ponded water evaporated, dissolved minerals began to pre-cipitate and to mix with clastic particles that washed into the

tracks, filling them completely or partially with finely laminatedmud. Subsequent flood events buried the tracks and host layerunder sediment, and the infilled tracks became consolidated soonafter burial (<100 years) in response to the mineral-rich watertableand (or) microbial activity, preserving a cast of the original foot-print. Modern erosion later removed the softer host rock unit andexposed the concretionary tracks.

Awareness of the existence of concretionary tracks raises thepotential that dinosaur tracks may be more common than previ-ously realized, especially in rock formations characterized by syn-depositional concretions and poorly drained paleoenvironments.However, once fully exposed, concretionary tracks can weatherrapidly, altering their diagnostic morphology and rendering themindistinguishable from nonichnogenic concretions. As such, con-cretionary tracks may be short-lived ichnofossils, explaining whythey have been rarely recognized until recently.

AcknowledgementsThe authors wish to thank Cam Lockerbie, Andrew Hunt, and

Donna Martin for assistance in granting access to the sites;Raymond Strom for producing high-quality thin sections; BrentKuntz for the photograph used in Fig. 9; and Julie Therrien fordiscovering the DH3 tracksite. The authors also wish to thankMartin Lockley and Federico Fanti for their constructive reviewsof the manuscript; and Rich McCrea for enlightening discussionsand his willingness to share photographs used in Fig. 4. This re-search was partly funded by the Royal Tyrrell Museum, a KillamPostdoctoral Fellowship (D.K.Z.), and a Natural Sciences and Engi-neering Research Council Discovery grant (D.K.Z.).

ReferencesAlexander, R.M. 1976. Estimates of speeds of dinosaurs. Nature, 261: 129–130.

doi:10.1038/261129a0.Browne, G.H., and Kingston, D.M. 1993. Early diagenetic spherulitic siderites

from Pennsylvanian palaeosols in the Boss Point Formation, Maritime Can-ada. Sedimentology, 40: 467–474. doi:10.1111/j.1365-3091.1993.tb01346.x.

Currie, P.J. 1989. Dinosaur footprints of Western Canada. In Dinosaur tracks andtraces. Edited by D.D. Gillette and M.G. Lockley. Cambridge University Press,Cambridge, UK. pp. 293–300.

Currie, P.J., Nadon, G.C., and Lockley, M.G. 1991. Dinosaur footprints with skinimpressions from the Cretaceous of Alberta and Colorado. Canadian Journalof Earth Sciences, 28(1): 102–115. doi:10.1139/e91-009.

Currie, P.J., Badamgarav, D., and Koppelhus, E.B. 2003. The first Late Cretaceousfootprints from the Nemegt locality in the Gobi of Mongolia. Ichnos, 10: 1–13.doi:10.1080/10420940390235071.

Daniels, R.B., Gamble, E.E., and Nelson, L.A. 1971. Relations between soil mor-phology and water-table levels on a dissected North Carolina coastal plainsurface. Soil Science Society of America Journal, 35: 781–784. doi:10.2136/sssaj1971.03615995003500050041x.

Eberth, D.A. 2005. The geology. In Dinosaur Provincial Park: a spectacular an-cient ecosystem revealed. Edited by P.J. Currie and E.B. Koppelhus. IndianaUniversity Press, Bloomington, IN. pp. 54–82.

Eberth, D.A., and Hamblin, A.P. 1993. Tectonic, stratigraphic, and sedimento-logic significance of a regional discontinuity in the upper Judith River Group(Belly River wedge) of southern Alberta, Saskatchewan, and northern Mon-tana. Canadian Journal of Earth Sciences, 30(1): 174–200. doi:10.1139/e93-016.

Fanti, F., Bell, P.R., and Sissons, R.L. 2013. A diverse, high-latitude ichnofaunafrom the Late Cretaceous Wapiti Formation, Alberta, Canada. CretaceousResearch, 41: 256–269. doi:10.1016/j.cretres.2012.12.010.

Fastovsky, D.E., and McSweeney, K. 1987. Paleosols spanning the Cretaceous–Paleogene transition, eastern Montana and western North Dakota. Geologi-cal Society of America Bulletin, 99: 66–77. doi:10.1130/0016-7606(1987)99<66:PSTCTE>2.0.CO;2.

Gangloff, R.A., May, K.C., and Storer, J.E. 2004. An early Late Cretaceous dinosaurtracksite in central Yukon Territory, Canada. Ichnos, 11: 299–309. doi:10.1080/10420940490442269.

Huerta, P., Fernández-Baldor, F.T., Farlow, J.O., and Montero, D. 2012. Excep-tional preservation processes of 3D dinosaur footprint casts in Costalomo(Lower Cretaceous, Cameros Basin, Spain). Terra Nova, 24: 136–141. doi:10.1111/j.1365-3121.2011.01047.x.

Kuban, G.J. 1989. Color distinction and other curious features of dinosaur tracksnear Glen Rose, Texas. In Dinosaur tracks and traces. Edited by D.D. Gilletteand M.G. Lockley. Cambridge University Press, Cambridge, UK. pp. 427–440.

Langston, W., Jr. 1960. A hadrosaur ichnite. National Museum of Canada NaturalHistory Papers, 4: 1–9.

Fig. 10. Potential tracks located in the hills near the DH3 tracksiteidentified on the basis of underlying soft-sediment deformation(arrowheads). The potential tracks can appear as amorphousconcretions (A, B), stained sediment (C), or undifferentiatedsediment (D). Scale bars in A and B = 30 cm.

640 Can. J. Earth Sci. Vol. 52, 2015

Published by NRC Research Press

Can

. J. E

arth

Sci

. Dow

nloa

ded

from

ww

w.n

rcre

sear

chpr

ess.

com

by

Alb

erta

Gov

ernm

ent L

ibra

ry o

n 08

/05/

15Fo

r pe

rson

al u

se o

nly.

Lockley, M. 1991. Tracking dinosaurs: a new look at an ancient world. CambridgeUniversity Press, Cambridge, UK.

Lockley, M., and Hunt, A.P. 1995. Dinosaur tracks and other fossil footprints ofthe Western United States. Columbia University Press, New York.

Lockley, M.G., Nadon, G., and Currie, P.J. 2004. A diverse dinosaur-bird foot-print assemblage from the Lance Formation, Upper Cretaceous, easternWyoming: implications for ichnotaxonomy. Ichnos, 11: 229–249. doi:10.1080/10420940490428625.

Lockley, M.G., McCrea, R.T., and Matsukawa, M. 2009. Ichnological evidence forsmall quadrupedal ornithischians from the basal Cretaceous of SE Asia andNorth America: implications for a global radiation. In Late Palaeozoic andMesozoic ecosystems in SE Asia. Edited by E. Buffetaut, G. Cuny, J.L. Loeuff,and V. Suteethorn. The Geological Society of London, Special Publications,315: 255–269. doi:10.1144/SP315.18.

Lockley, M.G., Triebold, M., and Janke, P.R. 2014. Dinosaur tracks from the HellCreek Formation (Upper Cretaceous, Maastrichtian), South Dakota. In Fossilfootprints of Western North America. Edited by M.G. Lockley and S.G. Lucas.New Mexico Museum of Natural History and Science, Bulletin 62. pp. 459–468.

Long, D.G.F., Lowey, G., and Sweet, A.R. 2000. Age and setting of dinosaur track-ways, Ross River area, Yukon Territory (105F/15). In Yukon Exploration andGeology 2000. Edited by D.S. Emond and L.H. Weston. Exploration andGeological Services Division, Yukon, Indian and Northern Affairs Canada.pp. 181–197.

Manning, P.L., Ott, C., and Falkingham, P.L. 2008. A probable tyrannosauridtrack from the Hell Creek Formation (Upper Cretaceous), Montana, UnitedStates. PALAIOS, 23: 645–647. doi:10.2110/palo.2008.p08-030r.

McCrea, R.T. 2003. Fossil vertebrate tracksites of Grande Cache, Alberta. Cana-dian Palaeobiology, 9: 11–30.

McCrea, R.T., and Buckley, L.G. 2005. A dinosaur track site from the Elk Valleycoal district. Marella, 20: 19–20.

McCrea, R.T., and Currie, P.J. 1998. A preliminary report on dinosaur tracksitesin the Lower Cretaceous (Aptian) Gates Formation near Grande Cache,Alberta. New Mexico Museum of Natural History and Science, Bulletin 14.pp. 155–162.

McCrea, R.T., Currie, P.J., and Pemberton, S.G. 2005. Vertebrate ichnology. InDinosaur Provincial Park: a spectacular ancient ecosystem revealed. Edited byP.J. Currie and E.B. Koppelhus. Indiana University Press, Bloomington, IN.pp. 405–416.

McCrea, R.T., Buckley, L.G., Plint, A.G., Currie, P.J., Haggart, J.W., Helm, C.W.,and Pemberton, S.G. 2014a. A review of vertebrate track-bearing formationsfrom the Mesozoic and earliest Cenozoic of western Canada with a descrip-tion of a new theropod ichnospecies and reassignment of an avian ichnoge-nus. In Fossil footprints of Western North America. Edited by M.G. Lockley,S.G. Lucas. New Mexico Museum of Natural History and Science, Bulletin 62.pp. 5–94.

McCrea, R.T., Buckley, L.G., Farlow, J.O., Lockley, M.G., Currie, P.J.,Matthews, N.A., and Pemberton, S.G. 2014b. A ‘terror of tyrannosaurs’: thefirst trackways of tyrannosaurids and evidence of gregariousness and pathol-ogy in tyrannosauridae. PLoS ONE, 9: e103613. doi:10.1371/journal.pone.0103613. PMID:25054328.

McLearn, F.H. 1923. Peace River Canyon Coal area. B.C. Geological Survey ofCanada, Summary Report 1922(B).

Miall, A.D. 1992. Alluvial deposits. In Facies models: response to sea level change.Edited by R.G. Walker and N.P. James. Geological Association of Canada.pp. 119–142.

Moratalla, J.J., Sanz, J.L., and Jimenez, S. 1988. Multivariate analysis on LowerCretaceous dinosaur footprints: discrimination between ornithopods andtheropods. Geobios, 21: 395–408. doi:10.1016/S0016-6995(88)80042-1.

Nadon, G.C. 1993. The association of anastomosed fluvial deposits and dinosaurtracks, eggs, and nests: implications for the interpretation of floodplain en-vironments and a possible survival strategy for ornithopods. PALAIOS, 8:31–44. doi:10.2307/3515220.

PiPujol, M.D., and Buurman, P. 1994. The distinction between ground-water gleyand surface-water gley phenomena in Tertiary paleosols of the Ebro Basin,NE Spain. Palaeogeography, Palaeoclimatology, Palaeoecology, 110: 103–113.doi:10.1016/0031-0182(94)90112-0.

Pye, K., Dickson, J.A.D., Schiavon, N., Coleman, M.L., and Cox, M. 1990. Forma-tion of siderite—Mg-calcite—iron sulfide concretions in intertidal marsh andsandflat sediments, north Norfolk, England. Sedimentology, 37: 325–343.doi:10.1111/j.1365-3091.1990.tb00962.x.

Retallack, G.J. 1994. A pedotype approach to latest Cretaceous and earliest Ter-tiary paleosols in eastern Montana. Geological Society of America Bulletin,106: 1377–1397. doi:10.1130/0016-7606(1994)106<1377:APATLC>2.3.CO;2.

Romilio, A., and Salisbury, S.W. 2011. A reassessment of large theropod dinosaurtracks from the mid-Cretaceous (late Albian-Cenomanian) Winton Forma-tion of Lark Quarry, central-western Queensland, Australia: a case for mis-taken identity. Cretaceous Research, 32: 135–142. doi:10.1016/j.cretres.2010.11.003.

Rylaarsdam, J.R., Varban, B.L., Plint, A.G., Buckley, L.G., and McCrea, R.T. 2006.Middle Turonian dinosaur paleoenvironments in the Upper CretaceousKaskapau Formation, northeast British Columbia. Canadian Journal of EarthSciences, 43(6): 631–652. doi:10.1139/e06-014.

Sampson, S.D., and Currie, P.J. 1996. On the trail of Cretaceous dinosaurs. In Lifein stone: a natural history of British Columbia fossils. Edited by R. Ludvigsen.UBC Press, Vancouver. pp. 143–155.

Sternberg, C.M. 1926. Dinosaur tracks from the Edmonton Formation of Alberta.Geological Survey of Canada Bulletin, 44: 85–87.

Sternberg, C.M. 1932. Dinosaur tracks from Peace River, British Columbia. Na-tional Museum of Canada Annual Report, 1930: 59–85.

Storer, J.E. 1975. Dinosaur tracks, Columbosauripus ungulatus (Saurischia, Coeluro-sauria), from the Dunvegan Formation (Cenomanian) of northeastern BritishColumbia. Canadian Journal of Earth Sciences, 12(10): 1805–1807. doi:10.1139/e75-160.

Tanke, D. 2004. Mosquitoes and mud. The 2003 Royal Tyrrell Museum of Palae-ontology expedition to the Grande Prairie region (north-western Alberta,Canada). Alberta Paleontological Society Bulletin, 19: 3–31.

Therrien, F., Zelenitsky, D.K., Tanaka, K., and Sloboda, W.J. 2014. First hadrosaurtrackway from the Upper Cretaceous (late Campanian) Oldman Formation,southeastern Alberta. In Hadrosaurs. Edited by D.A. Eberth and D.C. Evans.Indiana University Press, Bloomington, IN. pp. 532–539.

Thulborn, T. 1990. Dinosaur tracks. Chapman and Hall, London, UK.Triebold, M., Lockley, M., Janke, P., Nystrom, C., and Boaz, D. 1999. Dinosaur

tracks from the Hell Creek Formation (Upper Cretaceous, Maastrichtian),South Dakota. Journal of Vertebrate Paleontology, 19: 81A. doi:10.1080/02724634.1999.10011202.

Vepraskas, M.J. 1992. Redoximorphic features for identifying aquic conditions.North Carolina Agricultural Research Services Technical Bulletin, 301: 1–33.

Vepraskas, M.J., and Caldwell, P.V. 2008. Interpreting morphological features inwetland soils with a hydrologic model. Catena, 73: 153–165. doi:10.1016/j.catena.2007.07.005.

Therrien et al. 641

Published by NRC Research Press

Can

. J. E

arth

Sci

. Dow

nloa

ded

from

ww

w.n

rcre

sear

chpr

ess.

com

by

Alb

erta

Gov

ernm

ent L

ibra

ry o

n 08

/05/

15Fo

r pe

rson

al u

se o

nly.