the sirius passet lagerstätte of north greenland: a remote … · the sirius passet lagerstätte...

The Sirius Passet Lagerstaumltte of North Greenland a remotewindow on the Cambrian Explosion

David A T Harper12 Emma U Hammarlund23 Timothy P Topper45Arne T Nielsen6 Jan A Rasmussen7 Tae-Yoon S Park8 amp M Paul Smith91 Palaeoecosystems Group Department of Earth Sciences Durham University Durham DH1 3LE UK2 Department of Geology University of Lund Soumllvegatan 12 SE 223 62 Lund Sweden3 Department of LaboratoryMedicine Translational Cancer Research Lund University Scheelevaumlgen 2Medicon Village 404SE-223 81 Lund Sweden

4 Shaanxi Key Laboratory of Early Life and Environments State Key Laboratory of Continental Dynamics and Department ofGeology Northwest University Xirsquoan 710069 China

5 Department of Palaeobiology Swedish Museum of Natural History Box 50007 SE-104 05 Stockholm Sweden6 Department of Geosciences and Natural Resource Management Copenhagen University Oslashster Voldgade 10 DK-1350Copenhagen K Denmark

7 Fossil and Mo-clay Museum Museum Mors Skarrehagevej 8 DK-7900 Nykoslashbing Mors Denmark8 Division of Earth-System Sciences Korea Polar Research Institute 26 Songdomirae-ro Yeonsu-gu Incheon 21990Republic of Korea

9 Oxford University Museum of Natural History Parks Road Oxford OX1 3PW UKDATH 0000-0003-1315-9494 EUH 0000-0001-7625-4793 TPT 0000-0001-6720-7418 JAR 0000-0003-0520-9148

T-YSP 0000-0002-8985-930X MPS 0000-0002-5141-1577Correspondence davidharperdurhamacuk

Abstract The lower Cambrian Lagerstaumltte of Sirius Passet Peary Land North Greenland is one of the oldest of thePhanerozoic exceptionally preserved biotas The Lagerstaumltte evidences the escalation of numbers of new body plans and lifemodes that formed the basis for a modern functionally tiered ecosystem The fauna is dominated by predators infaunal benthicand pelagic and the presence of abundant nekton including large sweep-net feeders suggests an ecosystem rich in nutrientsRecent discoveries have helped reconstruct digestive systems and their contents muscle fibres and visual and nervous systemsfor a number of taxa New collections have confirmed the complex combination of taphonomic pathways associated with thebiota and its potentially substantial biodiversity These complex animal-based communities within the Buen Formation wereassociated with microbial matgrounds now preserved in black mudstones deposited below stormwave base that provide insightinto the shift from late Neoproterozoic (Ediacaran) to Cambrian substrates and communities Moreover the encasing sedimentholds important data on the palaeoenvironment and the water-column chemistry suggesting that these animal-basedcommunities developed in conditions with very low oxygen concentrations

Received 19 March 2019 revised 20 June 2019 accepted 20 June 2019

The Sirius Passet fossil biota is the most remote one of the leastwell-known and to date one of the least diverse of the majorCambrian Lagerstaumltten Following its serendipitous discovery in1984 (Conway Morris et al 1987 see Conway Morris 1998 andPeel amp Ineson 2011 for detailed accounts of the discovery and earlyexploration) the locality in the Buen Formation of North Greenlandhas been visited by only nine collecting expeditions in the 35 yearssince the discovery most recently in 2009 and 2011 bymultidisciplinary and multinational groups led by the NaturalHistory Museum of Denmark University of Copenhagen and in2016 2017 and 2018 by the Korea Polar Research InstitutendashUniversity of BristolndashCopenhagen group The Sirius PassetLagerstaumltte occurs in black mudstones deposited at the shelfndashslope break on the Laurentian margin Although deformed andmetamorphosed by a Devonian tectonic event the EllesmerianOrogeny the locality preserves the original depositional relation-ships to a large degree and allows a detailed interpretation of theenvironmental setting of this early Cambrian ecosystem and thusassists in understanding the ecological and environmental con-straints on the Cambrian Explosion (Babcock 2005) Thefossiliferous site is located beside J P Koch Fjord Peary LandNorth Greenland at 82deg 4759rsquo N 42deg 1354rsquo W (Fig 1) and analtitude of 420 m This remote locality can be reached only by short

take-off and landing aircraft that can use a rough 200 m strip in thevalley 2 km to the west of the fossiliferous site (Fig 2)

Geological context

During the early Cambrian Sirius Passet lay on the northern marginof Laurentia at a palaeolatitude of around 15deg S (Fig 1a) (Cocks ampTorsvik 2011) This segment of the GreenlandndashCanada margin iscommonly referred to as the Franklinian Basin (Higgins et al 1991Trettin et al 1991) it accommodates a succession of EdiacaranndashDevonian age extending from Kronprins Christian Land in easternNorth Greenland westwards to Ellesmere Island and the Arcticislands of Nunavut Canada (Fig 1b) (Higgins et al 1991 Trettinet al 1991 Blom 1999) Despite tectonic deformation (Soper ampHiggins 1987 1990) the early Paleozoic margin of Greenland isnotable for preserving an intact transition between shelf slope anddeep-water basin and its changing position and character throughtime has been documented in detail (Higgins et al 1991)

The Buen Formation overlies a carbonate unit the PortfjeldFormation (Figs 1c and 2) which crops out extensively across NorthGreenland and is the lateral correlative of the Ella Bay Formation onEllesmere Island (Long 1989 Dewing et al 2004) In the southernpart of North Greenland the Portfjeld Formation is subdivided by a

copy 2019 The Author(s) This is an Open Access article distributed under the terms of the Creative Commons Attribution 40 License (httpcreativecommonsorglicensesby40) Published by The Geological Society of London Publishing disclaimer wwwgeolsocorgukpub_ethics

Review Focus article Journal of the Geological Society

Published online July 26 2019 httpsdoiorg101144jgs2019-043 | Vol 176 | 2019 | pp 1023ndash1037

by guest on June 21 2020httpjgslyellcollectionorgDownloaded from

regionally developed karst surface into a lower (180 m thick) unit ofstorm-dominated dolostones and an upper 100 m thick mixedcarbonatendashclastic succession of fluvial and shallow marine sedi-ments (Higgins et al 1991 Ineson amp Peel 2011)

The Portfjeld Formation thickens northwards towards thecontinental margin where it is 400ndash700 m thick and passes intoits deep-water equivalent the Paradisfjeld Group which is made upof dark siliciclastic and carbonate mudstones interbedded withcarbonate turbidites and debris-flow deposits some of whichcontain large olistoliths (Surlyk amp Ineson 1987 Higgins et al 1991Ineson amp Peel 2011) The presence of large-scale debris flows andolistoliths led Surlyk amp Ineson (1987) to infer the exposure of anescarpment bounding the Portfjeld Formation to the north and anintact example of the escarpment with abutting debris flows wasdocumented by Ineson amp Peel (2011) 2 km NE of the Sirius Passetlocality

The age of the Portfjeld FormationndashParadisfjeld Group has beenthe subject of some debate Dewing et al (2004) considered thePortfjeld Formation to be of Ediacaran age on the basis of regionalcorrelations but Peel (1988) described cyanobacteria he consideredto be of early Cambrian age and Peel amp Higgins (1980) documentedthe coeloscleritophoran Chancelloria and nonarticulated brachio-pods from the upper part of the Paradisfjeld Group The presence ofa disconformity within the formation suggests that both ages arecorrect the unit comprising an older Ediacaran component and ayounger early Cambrian part The latter stratigraphic unit suggests

that the younger part of this phase of basin development is no olderthan Cambrian Stage 2

The Portfjeld Formation is overlain unconformably by sand-stones and mudstones of the Buen Formation The boundary is wellexposed adjacent to the Sirius Passet locality where the upper partof the carbonates is deeply fretted by karstic erosion with deepgrykes vadose fissures and accompanying shallow phreatic tubesall of which are infilled by millet-seed quartz arenite This lithologyis also seen as a thin sheet overlying the Portfjeld Formationregionally and passing upwards into black mudstones and siltstonesof the basal Buen Formation (Fig 2) In the deep-water successionthe uppermost limestone conglomerate bed of the ParadisfjeldGroup has a distinctive quartz sand matrix (Higgins et al 1991)which is partly correlative with the erosion surface

The Buen Formation and its correlatives crop out extensivelyacross North Greenland The most inboard development insouthern Peary Land is up to 500 m thick and dominated bysandstones deposited on a tide- and storm-influenced shelf that passnorthwards to a more mudstone- and siltstone-dominated shelf tothe north where the unit is up to 700 m thick (Higgins et al 1991)Transgressive surfaces bound three coarsening-upward sequencesacross the shelf that show an overall deepening trend (Davis ampHiggins 1987 Ineson amp Peel 2011) Northwards the shelfsediments pass into the deep-water succession of thePolkorridoren Group where the turbidites and deep-water mud-stones of units 3 4 and 5 of Davis amp Higgins (1987) are correlatives

Fig 1 Maps of the palaeogeographical and geographical setting of the Sirius Passet Lagerstaumltte (a) Location of North Greenland in the early Cambrian atc 520 Ma constructed in Bugplates (Torsvik 2009) Circle indicates location of the Sirius Passet Lagerstaumltte (b) The eastern Franklinian Basin (modifiedfrom Ineson amp Peel 2011) Red box indicates position of (c) (c) The Sirius Passet locality at 82deg 4759rsquo N 42deg 1354rsquo W east of J P Koch Fjord ismarked with a red star (modified from Le Boudec et al 2014)

1024 D A T Harper et al


of the three coarsening-upwards sequences of the Buen Formation(Davis amp Higgins 1987) The lower units of the PolkorridorenGroup (units 1 and 2 of Davis amp Higgins 1987) are probablycorrelative with the erosion surface at the top of the PortfjeldFormation together with the uppermost part of the ParadisfjeldGroup

The identification of carbonate debris flows in depositionalcontact with the Portfjeld Formation escarpment and the location ofthe Sirius Passet Lagerstaumltte adjacent to a vertical boundary withPortfjeld Formation dolostones led Ineson amp Peel (2011) to infer adepositional model in which mudstones of the lower BuenFormation lie at the foot of a relict escarpment of eroded PortfjeldFormation analogous to some hypotheses for the depositionallocation of the Burgess Shale Lagerstaumltte (Fletcher amp Collins 1998)However regional mapping during the 2009 and 2011 field seasons(Figs 2 and 3a) suggests that the relationship is more complex (seebelow)

Although Ineson amp Peel (2011) noted that the trilobites at theSirius Passet locality are typically inverted (lying ventral up) theyconsidered the section to be the right way up However detailedlogging in 2011 showed that 93 (n = 737) of the trilobites andmuch of the soft-bodied fauna is also inverted and thin graded bedsand cross-laminations were also seen to be inverted in thin sectionThe strata containing the Sirius Passet Lagerstaumltte are thus invertedbut directly adjacent to near-horizontal and right way up PortfjeldFormation (Fig 3) The Lagerstaumltte is thus interpreted here as beinglocated within a thin inverted horse of Buen Formation bounded onboth sides by faults that are part of a duplex beneath the Buen Thrust(Soper amp Higgins 1987 1990) the position of which is locallydetermined by the Portfjeld escarpment At the time of deposition

the Sirius Passet Lagerstaumltte did not sit at the foot of the escarpmentinstead local mapping (Figs 2 and 3a) suggests that it waspositioned at the outer edge of the relict platform at thecontemporary shelfndashslope break

The late Paleozoic Ellesmerian orogenic activity that generatedthe fold-and-thrust belt also led to regional metamorphism Platychloritoid porphyroblasts up to 5 mm in size are distributedthroughout the muddier intervals of the Sirius Passet Lagerstaumltte andare typically randomly oriented relative to laminations (Strang et al2016b fig 3F) They are accompanied by abundant Al-richchloritendashmica aggregates up to 10ndash20 microm in diameter (Strang et al2016b) Together these are taken to represent low greenschist-faciesmetamorphism which has influenced the presentation of thetaphonomic detail

Age of the Sirius Passet Lagerstaumltte

The most reliable indicator for the age of the Sirius Passet fauna isthe very abundant nevadiid trilobite Buenellus higginsi Blaker1988 Its range is correlated with the Nevadella trilobite biozone(Palmer amp Repina 1993 Blaker amp Peel 1997) and this ageinterpretation is supported by the distribution of other olenellinetrilobites in the Buen Formation (Blaker amp Peel 1997) Acritarchsamples from the basal part of the Buen Formation are either barrenor contain a sparse non-age diagnostic flora (Vidal amp Peel 1993)The Lagerstaumltte is thus correlated with the middle to upperMontezuman Stage in Laurentian terms as it contains a trilobitespecies (and is therefore younger than the pre-trilobite series) andlies below strata that contain early Dyeran trilobites (Palmer ampRepina 1993 Blaker amp Peel 1997 Babcock amp Peel 2007) The

Fig 2 Geological map of the Sirius Passet Lagerstaumltte and surrounding area in Peary Land North Greenland The outer shelfndashslope mudstone andsandstone units of the Buen Formation are equivalent to the lsquoTransitional Buen Formationrsquo of Ineson amp Peel (2011)

1025Sirius Passet Lagerstaumltte


recently described Buenellus chilhoweensis Webster amp Hageman2018 from the Murray Shale of Tennessee is very similar to theGreenland species and is assumed to be of a broadly similar age Ininternational terms the Nevadella zone age of the Sirius PassetLagerstaumltte corresponds to middle to upper Cambrian Stage 3(Atdabanian 515ndash518 Ma) (Ogg et al 2016) The fauna is thus ofclosely similar age to the more fully explored Chengjiang fauna ofsouthern China (Zhang et al 2008 Yang et al 2018) and with theavailable biostratigraphic resolution is of indistinguishable age

In sequence stratigraphic terms the Buen Formation correspondsto the base of the Sauk 1 supersequence (Sloss 1963 Palmer amp Peel1981 Golonka amp Kiessling 2002) which is recognizable acrossLaurentia as a major marine flooding and continental inundationevent (Morgan 2012 Peters amp Gaines 2012) Farther to the southalong the Laurentian margin in NE Greenland the base of Sauk 1 ismarked by the base of the Kap Holbaeligk Slottet and Kloslashftelvformations of the autochthon and allochthon (Smith et al 2004Smith amp Rasmussen 2008) in NW Scotland by the EribollFormation (Higgins et al 2001 Raine amp Smith 2012) and inNewfoundland by the Bradore Formation (Lavoie et al 2012)

The base of Sauk I is often marked across Laurentia byunfossiliferous quartz arenitic sandstones and granulestones andin consequence the age of the flooding event is poorly constrainedin many places The Nevadella Zone Sirius Passet fauna at the baseof the Buen Formation represents one of the few accurate temporalconstraints on this event in northern Laurentia (Fig 1)

Sedimentology and depositional setting

In the distal Buen Formation of the central J P Koch Fjord areaDavis amp Higgins (1987) recognized a basal unit of mature quartzarenites up to 40 m thick This unit as noted above also penetratesthe karstic erosion surface on top of the Portfjeld Formation In the

vicinity of the Sirius Passet locality the quartz arenite thins from afew metres to the south of the locality to being present only as infillsin the Portfjeld Formation palaeokarst adjacent to the locality Thisbasal sandstone unit is overlain by two coarsening-upwardssequences of mudstone and siltstone capped by sandstone whichequate to the lsquoTransitional Buen Formationrsquo of Ineson amp Peel(2011) the lower sequence is 50 m thick and the upper is 80 m(Davis ampHiggins 1987) These two sequences may be correlated forover 200 km along-strike from northern Nyeboe Land in the west toPeary Land in the east The lowest part of each of the sequencescontains black mudstones and siltstones which Davis amp Higgins(1987) noted had a lsquovarvedrsquo finely interlaminated appearance TheSirius Passet Lagerstaumltte is located within the lower of these twomudstone units and the geological context together with the highproportion of mudstone relative to siltstone indicate that it liestoward the base

The Lagerstaumltte section has been excavated to a thickness of 12 mand is covered by extensive talus at both ends it is also terminatedby a small fault at the stratigraphic base The sediments range fromlaminated mudstones to muddy siltstones and siltstones that havebeen metamorphosed to pelites and semi-pelites protolith termin-ology relating to the original sedimentary rock types is used for thefollowing description Four lithofacies were recognized andrepresent progressively higher proportions of silt-grade materialrelative to mud from (1) finely laminated mudstones to (2) siltymudstones with 3ndash10 mm lamination (3) flaggy muddy siltstonesand (4) massive siltstones (Fig 4)

The silty mudstones and muddy siltstones are dark grey and havea more widely spaced parting ranging from 3 mm up to 10 cmBioturbation with occasional preserved burrow forms is presentfrom 0 to 3 m and from 9 to 12 m in the measured section and in thecoarser siltstone beds from 3 to 9 m but is conspicuously absentfrom the thinly laminated mudstones containing the exceptional

Fig 3 (a) Panoramic view of the Sirius Passet locality looking towards the NE showing the geological relationships at the shelfndashslope boundary Thelocality is indicated by the inverted white younging symbol B sandstone-dominated shelf Buen Formation Bm mudstone-dominated Buen Formation ofthe shelfndashslope transition (= lsquoTransitional Buen Formationrsquo mudstone of Ineson amp Peel 2011) Bq basal quartz-arenites of the Buen Formation Bssandstone-dominated Buen Formation of the shelfndashslope transition (= lsquoTransitional Buen Formationrsquo sandstone of Ineson amp Peel 2011) d Cretaceous basicdykes FF Frigg Fjord Mudstones of the Polkorridoren Group P Portfjeld Formation Unit boundaries are indicated by heavier white dashed lines beddingtraces by lighter weight dashed lines faults are shown as red dashed lines (b) The Sirius Passet Lagerstaumltte locality viewed from the west showing the darksilty mudstones of the Buen Formation in faulted contact with the white carbonate rocks of the Portfjeld Formation (c) Close-up of the Sirius Passet localityshowing the quarry opened up on the 2011 expedition people for scale



preservation (Fig 4) The coarsest intervals in the section are mid-to dark grey siltstones that are typically massive or bioturbated butcontain occasional planar lamination (Fig 4)

In thin section silty layers are typically interlaminated withmudstone on a millimetre scale but occasionally display planarlamination and ripple cross-lamination sharp-based graded beds arealso present on a millimetre scale (Strang et al 2016b fig 3A D EG H) Silt laminae are often discontinuous on a millimetre tocentimetre scale andmay be no thicker than a single grain Althoughthe sharp-based graded and laminated beds are on amillimetre scalecoarsening-upwards packages from mudstone to siltstone can alsobe recognized on a decimetre to metre scale (Fig 4)

The finest-grained sediments are thinly laminated very dark greyto black mudstones with minor silt and a 1ndash3 mm parting It is thisinterval from 3 to 6 m that contains the exceptional preservation ofthe Sirius Passet Lagerstaumltte (Fig 4) and the conspicuously smoothbedding surfaces exhibit abundant meandering bedding-parallel

burrows preserved in convex and concave epirelief (Fig 4) Theburrow systems are concentrated around body fossils particularlythose of the large euarthropod Arthroaspis (Maacutengano et al 2012)Bedding surfaces are frequently covered by yellow to orange ironoxidendashhydroxide films and powder the latter the result ofweathering

Maacutengano et al (2012) considered the morphology of the burrowsystems in this interval to have clear commonalities with the feedingstrategies of under-mat miners (Seilacher 1999) From thislithofacies Strang et al (2016b fig 2CndashF) also documented thepresence of crinkly occasionally anastomosing carbonaceouslaminae sometimes silicified that are interlaminated with mudstoneand siltstone The carbonaceous laminae have markedly differentcathodoluminescence properties from the non-organic laminae(Strang et al 2016b fig 4C) Together this evidence supports thepresence of microbial mats that overgrew the sediment surface andthe cadavers of arthropods and that exhibit many of the diagnosticcharacters of microbial mats on muddy substrates (Schieber 2007)Intraclasts interpreted as fragments of early silicified microbial matoccur infrequently in both finer and coarser lithofacies (Strang et al2016b fig 3C) Evidence for these matgrounds is found only in theinterval with exceptional preservation (Fig 4)

In contrast the presence in the Sirius Passet succession ofgrading planar lamination and cross-lamination is consistent withdeposition from low-density sediment gravity flows at or just belowstorm wave base These gravity flows periodically covered themicrobial mats and their fauna The high proportion of mud and thepresence of very thin millimetre-scale fining-upwards packagessuggests that the depositional site lay below storm wave base andthat sediment was transported from further inboard by dilute densitycurrents A depositional site below storm wave base and probablythe photic zone in turn might suggest that the mats werechemoautotrophic Dense mats do occur in low light conditions(Haas et al 2018) below the photic zone in the modern ocean (Karlet al 1988 Emerson amp Moyer 2002 Levin 2003) which are alsoassociated with specific low-oxygen niches that are presumed tohave been more common in the past (Glazer amp Rouxel 2009)

The combination of sedimentological observations and thegeological context indicates that the depositional site of the SiriusPasset Lagerstaumltte was situated below storm wave base at the shelfndashslope break in the Franklinian Basin (Fig 5) Microbial mats in thislocation would have been periodically obruted by distal dilutegravity flows transporting mud and silt Given the low gradient ofthe outer shelf these gravity flows were probably generated bystorms In most of the section the sediment deposited from gravityflows was subject to bioturbation but in the interval containingexceptional preservation this did not occur

The Sirius Passet fauna

The Sirius Passet fauna has some similarities to that of the BurgessShale although it is of lower diversity currently comprisingapproximately 45 species (see Box 1) including trilobites spongesworms halkieriids lobopods and non-trilobite bivalved euarthro-pods The faunal list is provided in Table 1 a number of additionaltaxa are under investigation and more await description followingthe 2009 2011 2016 2017 and 2018 field seasons

The depositional context of microbial mats with a periodic influxof dilute sediment gravity flows is also reflected in the Sirius Passetbiota which may be divided into (1) a guild of mat dwellers and (2)allochthonous components The mat-dwelling guild includessuspension feeders (sponge species) mat grazers (for exampleHalkieria) and probable deposit feeders or omnivores (the trilobiteBuenellus and possibly the euarthropod Arthroaspis) The mat-dwelling guild is predominantly found at bed partings correspond-ing to the bases of event beds where they were obruted whereas the

Fig 4 Sedimentary log of the Sirius Passet Lagerstaumltte Peary LandNorth Greenland Orange bars indicate the presence of particulate ironoxides and films on bedding surfaces and red bars indicate the incidenceof exceptionally preserved soft tissues The event beds that make up thebulk of the sediment are of millimetre scale



allochthonous components are preferentially encased as BurgessShale-type films within the event beds

Penetrative vertical or subvertical burrows are absent in themudstone intervals with microbial mats The allochthonouscomponents are more diverse and include infaunal burrowers (egpriapulids palaeoscolecids and possibly loriciferans) and compo-nents of the nekton (Isoxys gilled lobopodians includingKerygmachela and the radiodontan Tamisiocaris together withvetulicolians) (see Box 2 for detail on the ecology of the biota)

Preservation and taphonomy

The Sirius Passet Lagerstaumltte predates the Burgess Shale (c 510 Ma)and is comparable in age with the Chengjiang biotas (c 518 MaYang et al 2018) it is therefore one of the earliest examples ofhigh-fidelity soft-tissue preservation in the Phanerozoic record Thetaphonomic pathways of the Sirius Passet Lagerstaumltte are yet to befully understood but preservation has been interpreted to be a resultof fluctuating oxygen conditions on the seafloor (Budd 1995Ineson amp Peel 2011 Peel amp Ineson 2011) strong redox gradientsand hampered diffusion aided by the carcasses themselves(Maacutengano et al 2012) or even deposition under a veneer of wind-blown dust (Le Boudec et al 2014) Despite these uncertainties theSirius Passet Lagerstaumltte has been considered to lie within thespectrum of Burgess Shale-type (BST) preservation (Budd 2011Topper et al 2018) Preservation through the deposit is howevervariable Trilobites are preserved as complete moulds showing aveneer of authigenic silica (Strang et al 2016b) and othermineralized forms such as hyolithids and halkieriids also preservemuch of their relief (ConwayMorris amp Peel 1995 Peel 2010a) Lessbiomineralized taxa such as Campanamuta and Arthroaspis arepreserved in slight relief replicated by silica and clay minerals(Budd 2011) and some taxa are preserved as 2D kerogenouscompressions (Vinther et al 2011a b Topper et al 2018) withsome degree of fidelity (Park et al 2018) Digestive tracts arecommonly phosphatized and preserved in three dimensions (Peel2017c) and some taxa (eg Campanamuta mantonae Budd 2011and Pambdelurion whittingtoni Budd 1998a) preserve silicified 3Dmuscle fibres (Budd 2011 Peel 2017c Young amp Vinther 2017)

Although the presence of 2D kerogenous films and somephosphatized digestive tracts in the Sirius Passet Lagerstaumltte iscomparable with preservational modes seen in BST deposits thereare a number of distinct taphonomic differences The authigenicsilica veneer documented from trilobite specimens (Strang et al2016b) is more reminiscent of preservation seen in some Ediacarandeposits (Tarhan et al 2016) than of preservation in conventionalBST deposits (Gaines 2014) In fact the large majority ofdocumented organisms from the Sirius Passet Lagerstaumltte have anelement of 3D preservation (eg Budd 1993 1999 2011 ConwayMorris amp Peel 1995 Stein et al 2010) which is dissimilar to theBST deposits where organisms have experienced a complete loss ofcellular detail and are predominantly preserved in two dimensions(Butterfield 1990 1995 2003 Gaines et al 2008 Gaines 2014Briggs 2015) Hyoliths for example in the Sirius Passet Lagerstaumltteare generally preserved as moulds in three dimensions (Peel 2010a)contrasting with specimens from the Burgess Shale Lagerstaumltte thatare preserved as kerogenous compressions (Moysiuk et al 2017)However an easier comparison can be drawn with hyolithsdocumented from the Chengjiang Lagerstaumltte that are also preservedas moulds with slight topographic relief (Hou et al 2017) Indeedquite a few taxa in the Chengjiang biota retain a level of threedimensionality as elegantly exhibited by Zhai et al (2019) Fossilsfrom the Burgess Shale Lagerstaumltte also typically show tissue-specific variation in the elemental composition of phyllosilicatetemplates (Orr et al 1998 Page et al 2008) The kerogenous filmsin the Sirius Passet do not generally show any specific tissue-relatedmineral variation and are instead homogeneous most probably as aresult of exposure to higher temperatures during metamorphism(Topper et al 2018) Nevertheless there is some high-fidelitypreservation most notably the brain nervous system and eyes ofKerygmachela (Park et al 2018) The preservation of muscles inthree dimensions is rare in Cambrian Lagerstaumltten having beendocumented only in Campanamuta and Pambdelurion in the SiriusPasset fauna muscles have been also identified in specimens ofMyoscolex from the Emu Bay Shale in South Australia (Briggs ampNedin 1997) a site like Sirius Passet not currently considered to beBST (Jago et al 2012 Paterson et al 2016) owing to the effectsof early andor late diagenetic mineralization (Gaines 2014)

Fig 5 Schematic block diagramillustrating the depositional environmentof the Sirius Passet Lagerstaumltte and theBuen Formation of the Franklinian shelfduring the early Cambrian (Stage 3) Thedepositional location of the Sirius PassetLagerstaumltte is indicated by a red starVertical scale greatly exaggeratedModified after Strang et al (2016b)



Moreover the remarkable preservation of guts in Campanamuta(Strang et al 2016a) and midgut glands in the lobopodianPambdelurion indicates the evolution of carnivory and macrophagywithin the trajectory of arthropod evolution (Vannier et al 2014)

These different preservation modes in the Sirius Passet biota mayreflect differences in the general composition of the original tissuesof the organism and their variable susceptibility to decay (Topperet al 2018) but also potentially to fluctuations in ocean chemistryand the presence or absence of microbial mats at the time Trilobitesand other three-dimensionally preserved taxa for example arepreserved in association with the microbial mats whereas thecompressed kerogenous films are more typically preserved withingravity flows with no direct association with themicrobial mats Theunderstanding of the preservational processes in the Sirius PassetLagerstaumltte is currently less advanced than that for the BurgessShale and Chengjiang Lagerstaumltten and new investigations mayprovide further clarification of these preservational modesHowever the clear presence of matgrounds and trace fossils inclose association with fossils is fairly unusual for Cambrian

Lagerstaumltten preserving soft parts (Buatois et al 2014) and incombination with the complex set of taphonomic modes presentshows that the Sirius Passet represents a rather unusual CambrianLagerstaumltte

Water column chemistry

Our high-resolution geochemical exploration of palaeoenviron-mental conditions in the Sirius Passet Lagerstaumltte has involved todate the analysis of 144 samples through 12 m of the BuenFormation (Hammarlund et al 2019 Fig 10) The geochemicaltrends displayed through the succession are subtle but appear to bemutually correlated especially at the transitions into and out of theinterval with thinly laminated mudstones that also contain thehighest fossil abundance (28ndash77 m) (Fig 10) At these twotransitions both the content of total organic carbon (TOC) (c 1 wt) and ratios of highly reactive iron to total iron (FeHRFeT) increase(Fig 10) Occasionally high FeHRFeT values (maximum 069)indicate intervals of water column anoxia but generally FeHRFeT

Table 1 The Sirius Passet fauna

Aaveqaspis inesoni Peel amp Stein 2009 EuarthropodaArthroaspis bergstroemi Stein et al 2013 EuarthropodaBuenaspis forteyi Budd 1999 EuarthropodaBuenellus higginsi Blaker 1988 EuarthropodaCampanamuta mantoni Budd 2011 EuarthropodaIsoxys volucris Williams et al 1996 Stein et al 2010 Nielsen et al 2017 EuarthropodaIsoxys sp Williams et al 1996 EuarthropodaKiisortoqia soperi Stein 2010 EuarthropodaKleptothule rasmusseni Budd 1995 EuarthropodaMolaria steini Peel 2017a EuarthropodaPauloterminus spinodorsalis Taylor 2002 EuarthropodaSidneyia sp Peel 2017b EuarthropodaSiriocaris trollae Lagebro et al 2009 EuarthropodaHadranax augustus Budd amp Peel 1998 LobopodiaKerygmachela kierkegaardi Budd 1993 1999 Park et al 2018 LobopodiaPambdelurion whittingtoni Budd 1998a Vinther et al 2016 LobopodiaTamisiocaris borealis Daley amp Peel 2010 Vinther et al 2014 RadiodontaChalazoscolex pharkus Conway Morris amp Peel 2010 PalaeoscolecidaXystoscolex boreogyrus Conway Morris amp Peel 2010 PalaeoscolecidaSinguuriqia simony Peel 2017a PriapulidaPhragmochaeta canicularis Conway Morris amp Peel 2008 AnnelidaPygocirrus butyricampum Vinther et al 2011a AnnelidaHalkieria evangelista Conway Morris amp Peel 1990 1995 Vinther amp Nielsen 2005 MolluscaHyolithus cf tenuis Peel 2010a HyolithaHyolithid sp Peel 2010a HyolithaOrthothecid sp Peel 2010a HyolithaTrapezovitus sp Peel 2010a HyolithaSirilorica carlsbergi Peel 2010b Peel et al 2013 LoriciferaSirilorica pustulosa Peel 2010b Peel et al 2013 LoriciferaOoedigera peeli Vinther et al 2011b VetulicoliaGenus and species indeterminate A Vinther et al 2011b VetulicoliaArchaeocyatha spp Peel 2010a PoriferaChoia cf carteri Botting amp Peel 2016 PoriferaConstellatispongia canismajorii Botting amp Peel 2016 PoriferaCrassicoactum cucumis Botting amp Peel 2016 PoriferaDemospongiae indet Botting et al 2015 PoriferaFieldospongia bellineata Botting amp Peel 2016 PoriferaHamptonia limatula Botting amp Peel 2016 PoriferaLenica cf unica Botting amp Peel 2016 PoriferaLenica hindei Botting amp Peel 2016 PoriferaLenica perverse Botting amp Peel 2016 PoriferaSaetaspongia cf densa Botting amp Peel 2016 PoriferaSaetaspongia procera Botting amp Peel 2016 PoriferaSalactiniella cf plumata Botting amp Peel 2016 PoriferaStephanella sp Botting amp Peel 2016 Porifera



values remain below the threshold of 038 that is conventionallyused to define anoxic settings (Poulton amp Canfield 2011) In low-grade metamorphic rocks like those at Sirius Passet highly reactiveiron may have become unavailable for extraction and thuscompromise the proxy and underestimate the presence of watercolumn anoxia (Poulton amp Canfield 2011) However the SiriusPasset Lagerstaumltte also contains trace fossils of a meiofauna(Maacutengano et al 2012) This indicates that the water column was

probably not persistently anoxic suggesting that the iron-basedproxy has not been dramatically altered in favour of lower valuesTherefore the FeHRFeT values in the interval of thinly laminatedmudstones and highest fossil abundance (023 plusmn 011) are acceptedas realistic and can be considered lsquointermediatersquo These FeHRFeTvalues fall within the range of intermediate FeHRFeT values (above014 but below 038) observed in low-oxygen depositional settingsboth modern and ancient (Raiswell amp Canfield 1996 Farrell et al

Box 1 Rarefaction analysis

How diverse was the Sirius Passet faunaThe remote location inability to transport large sample collections and the relatively short field seasons populated by small groups of researchers have led to

relatively small-scale investigations of the site to date The extensive sampling programmes led by the Geological Survey of Greenland with the universities ofCambridge and Uppsala relied almost entirely on specimens from the richly fossiliferous scree slopes Collections were accumulated and courtesy of DrMartin Steinwho curated the collections in Uppsala University data were made available for rarefaction analysis (Hammer et al 2001) Based on a sample size of some 8000specimens species diversity appeared to level off at around 25 species suggesting that no further collecting would increase the diversity of the fauna (Fig 6a) Thescree-slope fauna appears however to have limited ability to capture or predict the possible diversity of the entire fauna presumably owing to the more weatheredscree specimens being more challenging to identify During the 2011 field season the section was sampled bed-by-bed and despite the uncertainties of fieldidentification the c 6000 specimens suggest a diversity in excess of 45 species with a curve that has yet to level off (Fig 6b) There is thus much more to be gleanedfrom the exposures regarding the diversity of the Sirius Passet fauna together with its composition structure and taphonomy

Box 2 Composition and ecology of the fauna

Some 45 species of animals are currently known from the Sirius Passet fauna (see Table 1) representing at least eight major clades The fauna is unique showing ahigh level of endemism and sharing only a few taxa with other Cambrian Lagerstaumltten (Holmes et al 2018) Taxon counts are summarized in Figure 7 for diversityand abundance The specimens illustrated are reposited in the Natural History Museum of Denmark University of Copenhagen (prefix MGUH) They indicate thediversity and preservation of the abundant euarthropods (Fig 8) evidencing the presence of key stem groups (Budd 1998ab) and other key elements of the fauna(Fig 9) In terms of taxa species numbers are dominated by euarthropods and sponges (Fig 7a) and bed-by-bed identifications of specimens during the 2011 fieldseason indicate that numerically euarthropods are significantly the most dominant (Fig 7b) Ecologically the biota comprises a mat-dwelling fauna including agrazing and omnivorous mobile benthos (eg the mollusc Halkieria the trilobite Buenellus Fig 8a and the euarthropods Buenaspis and Kleptothule Fig 8d and e)and fixed suspension-feeders (eg sponges Fig 8j and hyoliths) The infauna included a range of worms with carnivorous life styles including palaeoscolecides(Fig 8i) and polychaetes (Fig 9c) but these taxa are not interpreted to be preserved in situ Nektobenthos and nekton included a range of predators including variouseuarthropods (eg Campanamuta and Kiisortoqia Fig 8c and g) Isoxys (Fig 8f ) which probably formed shoals together with a diverse fauna of lobopodians (egHadranax Pambdelurion and Kerymachela Fig 9e and f ) and the sweep-net feeder Tamisiocaris (Fig 9a)This is also an emerging pattern in other early Cambrian Lagerstaumltten where detritus and suspension-feeders are much less common than during the subsequent

Phanerozoic (Bush amp Bambach 2011) Nevertheless the presence of large sweep-net feeders such as Tamisiocaris indicates already a sufficiency of pelagic prey inthe early Cambrian oceans (Vinther et al 2014) New discoveries from the Sirius Passet Lagerstaumltte have not only increased the diversity of early Cambrian faunasbut the excellence of preservation despite some metamorphism and tectonism has presented new information on the gut contents of a number of euarthropods andlobopods supporting predatory andor scavenging life modes (Strang et al 2016a Peel 2017c) as well as on their visual and nervous systems (Park et al 2018)together with muscle fibres (Budd 2011 Peel 2017c) This distinctive ecosystem structure emphasizes the contrast between the Cambrian and Paleozoic evolutionaryfaunas the latter dominated by a suspension-feeding benthos generated during the Great Ordovician Biodiversification Event (Harper 2006 Servais et al 2010Servais amp Harper 2018) The early Cambrian assemblages display a high degree of endemism (Meert amp Lieberman 2008 Peng et al 2012) that changed only later inthe Cambrian with the more widespread distribution of nonarticulate brachiopods (Bassett et al 2002) and more complex and diverse distributional patterns in thetrilobites (Aacutelvaro et al 2013)

Fig 6 Rarefaction curves (a) based on data from the scree collections kindly provided by M Stein (b) based on data from the intensive bed-by-bedsampling during the 2011 expedition



2013 Scholz et al 2014 Hammarlund et al 2017) and are higherthan the average FeHRFeT ratio (014 plusmn 011) determined forCambrian sediments deposited below an oxic water column(PoultonampRaiswell 2002) An intermediate setting is also consistentwith the occurrence of sparse trace fossils On one hand the finelylaminated mudstones suggest that the setting was uninhabitable forbioturbating organisms that would have vertically disrupted andmixed the sediment On the other hand the presence of themeiofauna that left a network of fine calibre burrows (Maacutengano et al2012) excludes a persistently anoxic water column Thus tracefossils and FeHRFeT data collectively suggest a low-oxygen but notanoxic water column The co-enrichment of trace metals (VAl andMoAl) is also consistent with a depositional setting below a watercolumn with very low concentrations of oxygen (Piper amp Dean2002 Brumsack 2006) Taken together FeHRFeT TOC VAl andMoAl data are consistent with intervals of very low water-columnoxygen concentrations during deposition of the Sirius Passetsuccession What drove the development of these conditions

remains unclear but changes in sea-level or primary productionor both are options consistent with these observations

The highest diversity of animal species recorded in the intervalbetween 30 and 77 m in the Sirius Passet succession correspondsto an interval where the water column appears to have containedvery low concentrations of dissolved oxygen (Fig 10) there is asignificant positive correlation (P = 53 times 10minus7) between diversityand FeHRFeT values (Hammarlund et al 2019) The intervals oflow-oxygen water-column conditions thus directly correlate withpreserved biodiversity Although reducing bottom water conditionsare expected to associate with favourable preservational conditionsthis is by no means the only requirement (Gaines 2014) Thus thepresence and preservation of the Lagerstaumltte fauna was mostprobably facilitated by additional factors of biological geological ortaphonomical character or a combination of them

The seemingly contradictory observations at Sirius Passet withsignificant in situ animal preservation and yet the general absence ofvertical bioturbation other than superficial burrow systems can be

Fig 7 (a) Diversity of taxa based onpublished data (Table 1) (b) Abundance oftaxa based on bed-by-bed sampling duringthe 2011 expedition



Fig 8 (a) Buenellus higginsi Blaker 1988 MGUH 33376 scale bar 1 cm (b) Arthroaspis bergstroemi Stein Budd Peel amp Harper 2013 MGUH 33377scale bar 3 cm (c) Campanamuta mantoni Budd 2011 MGUH 33378 scale bar 2 cm (d) Kleptothule rasmusseni Budd 1995 MGUH 33379 scale bar5 mm (e) Buenaspis forteyi Budd 1999 MGUH 33380 scale bar 5 mm (f ) Isoxys volucris Williams Siveter amp Peel 1996 MGUH 33381 scale bar5 mm (g) Kiisortoqia soperi Stein 2010 MGUH 33382 scale bar 5 mm (h) Sirilorica carlsbergi Peel 2010b MGUH 33383 scale bar 5 mm(i) Xystoscolex boreogyrus Conway Morris amp Peel 2010 MGUH 33384 scale bar 5 mm ( j) Lenica hindei (Dawson 1896) MGUH 33385 scale bar 1 cm



understood by comparison with modern low-oxygen ecosystemsThe lack of bioturbation but the presence of horizontal trace makerspioneering species and chemosynthesis-based nutrition are allobservations that may be reconciled with extremely low-oxygensettings (Levin 2003) Modern Oxygen Minimum Zones (OMZs)also share certain ecological characteristics with the Sirius Passetbiota For example a generally low diversity characterized by large

predators and detrivores and a short food chain (Levin 2003) areobserved in both settings Taken together we interpret the SiriusPasset Lagerstaumltte as having been deposited in a dynamic settingexperiencing both intermittent turbulence (with sediment gravityflows punctuating quieter background sedimentation) and fluctuat-ing oxygen concentrations The geochemical and palaeontologicaldata from Sirius Passet are comparable with those in modern OMZs

Fig 9 (a) Tamisiocaris borealis Daley amp Peel 2010 MGUH 30500 scale bar 2 cm (b) Ooedigera peeli Vinther Smith amp Harper 2011b MGUH 29279scale bar 5 mm (c) Pygocirrus butyricampum Vinther Eibye-Jacobsen amp Harper 2011a MGUH 29288 scale bar 5 mm (d) Aaveqaspis inesoni Peel ampStein 2009 MGUH 33386 scale bar 5 mm (e f ) Kergymachela kierkegaardi Budd 1993 MGUH 32048a ((e) close-up of head region scale bar 5 mm(f ) plan view scale bar 2 cm) (g) Pauloterminus spinodorsalis Taylor 2002 MGUH 33387 scale bar 1 cm



(eg chemosynthetic nutrition monospecific communities andshort food chain) and are also consistent with an interpretation thatoxygen concentrations were variable but consistently low whichrestricted bioturbation but were at times sufficient to permit theestablishment of a limited nektobenthic community (Fig 10)Although optimal conditions for preservation were associated withfluctuations in water-column chemistry and sea-level we envisagethat a substantial component of the Sirius Passet animal communityalso lived at or near the site tolerating conditions of low water-column oxygen concentrations The geochemical analysis indicatesthat the Sirius Passet Lagerstaumltte represents an early Cambrian biotathat in terms of oxygen lived at concentrations that we todayconsider extremely low (Hammarlund et al 2019)

Significance of the fauna

The Sirius Passet biota is one the oldest of the CambrianLagerstaumltten and may form a bridge between NeoproterozoicEdiacara biotas and the diverse communities of the Paleozoic era(Erwin amp Valentine 2013) It retains some features of the latestProterozoic ecosystems such as a seafloor associated in placeswith microbial mats and a unique style of preservation in some taxaBut in most other features such as an overwhelming dominance ofanimals particularly predators a highly populated water columnand locally abundant trace fossils the fauna is an early window onthe evolution of the Paleozoic biota The fauna also provides anopportunity to study the early evolution of a number of animalgroups the mode of construction of some of the first animal-basedcommunities and an indication of the environment and seawaterchemistry that were associated with the initial stages of theCambrian Explosion

The Sirius Passet Lagerstaumltte preserves remnants of the earliestCambrian microbial mat community associated with exceptionalpreservation predating the Burgess Shale by c 10 myr Aremarkable array of distinctive faunal elements and preservationalmodes demonstrate that the Sirius Passet represents a unique andsignificant site on which to study the Cambrian Explosion Thesemicrobial mat communities dissipated with the appearance ofabundant mat grazers and burrowers as the Cambrian Explosion

intensified and the seafloor switched from a Neoproterozoiclsquosavannahrsquo to the modern marine seascapes of the Phanerozoic(Budd amp Jensen 2015) The Sirius Passet biota thus has considerablesignificance in understanding the early radiation ofmetazoan groupsthe assembly of the first complex animal-based communities theirrelationship to oxygen and the establishment of modern ecosystems

Acknowledgements J Vinther was a member of the 2011ndash18 expedi-tions to North Greenland He directed and stimulated a significant number of ourresearch themes and we thank him for his input We also thank J W Hansen andM Stein for their assistance in the field during the 2011 expedition to SiriusPasset D Briggs J Ortega-Hernaacutendez and an anonymous reviewer significantlyimproved the clarity of the paper We thank A Bashforth (Natural HistoryMuseum of Denmark University of Copenhagen) for registering the specimenswith MGUH numbers Finally we thank P Donoghue for his invitation (andconstant encouragement) to contribute to the Journal of the Geological SocietyrsquoslsquoReview Focusrsquo series

Funding We thank Geocenter Danmark the Wenner-Gren Foundation theAgouron Institute Carlsbergfondet the Leverhulme Trust and the SwedishResearch Council (VR) for financial support

Author contributions DATH Conceptualization (Equal) Formalanalysis (Equal) Funding acquisition (Lead) Writing ndash Original Draft (Equal)Writing ndash Review amp Editing (Equal) EUH Formal analysis (Equal)Investigation (Equal) Writing ndash Review amp Editing (Supporting) TPT Datacuration (Equal) Writing ndash Review amp Editing (Equal) ATN Data curation(Equal) Investigation (Supporting) Writing ndash Review amp Editing (Supporting)JAR Data curation (Supporting) Investigation (Equal) Writing ndash Review ampEditing (Supporting) TSP Writing ndash Review amp Editing (Supporting) MPSConceptualization (Equal) Formal analysis (Equal) Writing ndash Original Draft(Equal) Writing ndash Review amp Editing (Equal)

Scientific editing by Philip Donoghue

ReferencesAacutelvaro JJ Ahlberg P et al 2013 Global Cambrian trilobite palaeobiogeo-

graphy assessed using parsimony analysis of endemicity In Harper DAT ampServais T (eds) Early Palaeozoic Biogeography and PalaeogeographyGeological Society London Memoirs 38 273ndash296 httpsdoiorg101144M3819

Babcock LE 2005 Interpretation of biological and environmental changesacross the NeoproterozoicndashCambrian boundary developing a refined under-standing of the radiation and preservational record of early multicellular

Fig 10 Correlation of geochemical trends (FeHRFeT TOC δ15NT VAl) in the Sirius Passet section with fossil abundance (black continuous line) and

species diversity (red dashed line) next to cumulative abundance (n = 100 between individual tick marks) of the five most common fossils (BuenellusArthroaspis Campanamuta and Kleptothule (presumed nektobenthic) and Isoxys (certainly nektonic)) together with inferred changes (dashed black lines)of bottom water oxygen concentrations [O2]BW and relative water depth Yellow zone in FeHRFeT column brackets intermediate FeHRFeT values betweenthe Cambrian average value of 014 and the 038 value that is used to distinguish oxic and anoxic waters Proposed intervals of periodic anoxia in blue withhorizontal ruling Modified from Hammarlund et al 2019



organisms Palaeogeography Palaeoclimatology Palaeoecology 220 1ndash5httpsdoiorg101016jpalaeo200409013

Babcock LE amp Peel JS 2007 Palaeobiology taphonomy and stratigraphicsignificance of the trilobite Buenellus from the Sirius Passet biota Cambrianof North Greenland Memoirs of the Association of AustralasianPalaeontologists 34 401ndash418

Bassett MG Popov LE amp Holmer LE 2002 Brachiopods CambrianndashTremadoc precursors to Ordovician radiation events In Crame JA amp OwenAW (eds) Palaeobiogeography and Biodiversity Change the Ordovicianand MesozoicndashCenozoic Radiations Geological Society London SpecialPublications 194 13ndash23 httpsdoiorg101144GSLSP20021940102

Blaker MR 1988 A new genus of nevadiid trilobite from the Buen Formation(Early Cambrian) of Peary land central North Greenland In Peel JS (ed)CambrianndashJurassic fossils trace fossils and stratigraphy from GreenlandGroslashnlands Geologiske Undersoslashgelse Rapport 137 33ndash41

Blaker MR amp Peel JS 1997 Lower Cambrian trilobites from NorthGreenland Meddelelser om Groslashnland Geoscience 35

Blom H 1999 Vertebrate remains from Upper Silurian Lower Devonian bedsof Hall Land North Greenland Geology of Greenland Survey Bulletin 182

Botting JP amp Peel JS 2016 Early Cambrian sponges of the Sirius PassetBiota North Greenland Papers in Palaeontology 2 463ndash487 httpsdoiorg101002spp21048

Botting JP Caacuterdenas P amp Peel JS 2015 A crown-group demosponge fromthe early Cambrian Sirius Passet Biota North Greenland Palaeontology 5835ndash43 httpsdoiorg101111pala12133

Briggs DEG 2015 The Cambrian Explosion Current Biology 25R864ndashR868 httpsdoiorg101016jcub201504047

Briggs DEG amp Nedin C 1997 The taphonomy and affinities of theproblematic fossil Myoscolex from the Lower Cambrian Emu Bay Shale ofSouth Australia Journal of Paleontology 71 22ndash23 httpsdoiorg101017S0022336000038919

Brumsack HJ 2006 The trace metal content of recent organic carbon-richsediments Implications for Cretaceous black shale formationPalaeogeography Palaeoclimatology Palaeoecology 232 344ndash361httpsdoiorg101016jpalaeo200505011

Buatois LA Narbonne GM Maacutengano MG Carmona NB amp Myrow P2014 Ediacaran matground ecology persisted into the earliest CambrianNature Communications 5 3544ndash3549 httpsdoiorg101038ncomms4544

Budd G 1993 A Cambrian gilled lobopod from Greenland Nature 354709ndash711 httpsdoiorg101038364709a0

Budd G 1995 Kleptothule rasmusseni gen et sp nov an olenellinid-liketrilobite from the Sirius Passet fauna (Buen Formation Lower CambrianNorth Greenland) Earth and Environmental Science Transactions of the RoyalSociety of Edinburgh 86 1ndash12 httpsdoiorg101017S0263593300002121

Budd GE 1998a Stem-group arthropods from the Lower Cambrian Sirius Passetfauna of North Greenland In Fortey RA amp Thomas RH (eds) ArthropodRelationships Systematics Association Special Volume Series 55 125ndash138

Budd GE 1998b Arthropod body-plan evolution in the Cambrian with anexample from anomalocaridid muscle Lethaia 31 197ndash210 httpsdoiorg101111j1502-39311998tb00508x

Budd G 1999 A nektaspid arthropod from the Early Cambrian Sirius Passetfauna with a description of retrodeformation based on functional morphologyPalaeontology 42 99ndash122 httpsdoiorg1011111475-498300064

Budd GE 2011 Campanamuta mantonae gen et sp nov an exceptionallypreserved arthropod from the Sirius Passet Fauna (Buen Formation lowerCambrian North Greenland) Journal of Systematic Palaeontology 9217ndash260 httpsdoiorg101080147720192010492644

Budd GE amp Jensen S 2015 The origin of the animals and a lsquoSavannahrsquohypothesis for early bilaterian evolution Biological Reviews 92 446ndash473httpsdoiorg101111brv12239

Budd GE amp Peel JS 1998 A new xenusiid lobopod from the early CambrianSirius Passet fauna of North Greenland Palaeontology 41 1202ndash1213

Bush AM amp Bambach RK 2011 Paleoecologic trends in Metazoa AnnualReview of Earth and Planetary Sciences 39 241ndash269 httpsdoiorg101146annurev-earth-040809-152556

Butterfield NJ 1990 Organic preservation of non-mineralizing organisms andthe taphonomy of the Burgess Shale Paleobiology 16 272ndash286 httpsdoiorg101017S0094837300009994

Butterfield NJ 1995 Secular distribution of Burgess-Shale-type preservationLethaia 28 1ndash13 httpsdoiorg101111j1502-39311995tb01587x

Butterfield NJ 2003 Exceptional fossil preservation and the Cambrianexplosion Integrative and Comparative Biology 43 166ndash177 httpsdoiorg101093icb431166

Cocks LRM amp Torsvik TH 2011 The Palaeozoic geography of Laurentia andwestern Laurussia a stable craton with mobile margins Earth-ScienceReviews 106 1ndash51 httpsdoiorg101016jearscirev201101007

Conway Morris S 1998 The Crucible of Creation the Burgess Shale and theRise of Animals Oxford University Press Oxford

Conway Morris S amp Peel JS 1990 Articulated halkieriids from the LowerCambrian of north Greenland Nature 345 802ndash805 httpsdoiorg101038345802a0

Conway Morris S amp Peel JS 1995 Articulated halkieriids from the LowerCambrian of North Greenland and their role in early protostome evolutionPhilosophical Transactions of the Royal Society Series B 347 305ndash358httpsdoiorg101098rstb19950029

Conway Morris S amp Peel JS 2008 The earliest annelids lower Cambrianpolychaetes from the Sirius Passet Lagerstaumltte Peary Land North GreenlandActa Palaeontologica Polonica 53 137ndash148 httpsdoiorg104202app20080110

Conway Morris S amp Peel JS 2010 New palaeoscolecidan worms from thelower Cambrian Sirius Passet Fossil-Lagerstaumltte (North Greenland) LathamShale (California) and Kinzers Shale (Pennsylvania) Acta PalaeontologicaPolonica 55 141ndash156 httpsdoiorg104202app20090058

Conway Morris S Peel JS Higgins AK Soper NJ amp Davis NC 1987 ABurgess shale-like fauna from the Lower Cambrian of North GreenlandNature 326 181ndash183 httpsdoiorg101038326181a0

Daley AC amp Peel JS 2010 A possible anomalocaridid from the CambrianSirius Passet Lagerstaumltte North Greenland Journal of Paleontology 84352ndash355 httpsdoiorg10166609-136R11

Davis NC amp Higgins AK 1987 CambrianndashLower Silurian stratigraphy in thefold and thrust zone between northern Nyeboe Land and JP Koch Fjord NorthGreenland In Report on the 1985 geological expedition to central and westernNorth Greenland Groslashnlands Geologiske Undersoslashgelse Rapport 133 91ndash98

Dawson JW 1896 Additional notes on fossil sponges and other organic remainsfrom the Quebec Group of Little Meacutetis on the lower St Lawrence with noteson some of the specimens by Dr G J Hinde Transactions of the RoyalSociety of Canada 44 91ndash121

Dewing K Harrison JC Pratt BR amp Mayr U 2004 A probable lateNeoproterozoic age for the Kennedy Channel and Ella Bay formationsnortheastern Ellesmere Island and its implications for passive margin historyof the Canadian Arctic Canadian Journal of Earth Sciences 41 1013ndash1025httpsdoiorg101139e04-044

Emerson D amp Moyer CL 2002 Neutrophilic Fe-oxidizing bacteria areabundant at the Loihi Seamount hydrothermal vents and play a major role in Feoxide deposition Applied Environmental Microbiology 68 3085ndash3093httpsdoiorg101128AEM6863085-30932002

Erwin DH amp Valentine JW 2013 The Cambrian Explosion RobertsGreenwood Village CO

Farrell UacuteC Briggs DE Hammarlund EU Sperling EA amp Gaines RR2013 Paleoredox and pyritization of soft-bodied fossils in the OrdovicianFrankfort Shale of New York American Journal of Science 313 452ndash489httpsdoiorg10247505201302

Fletcher TP amp Collins DH 1998 The Middle Cambrian Burgess Shale and itsrelationship to the Stephen Formation in the southern Canadian RockyMountainsCanadian Journal of Earth Sciences 35 413ndash436 httpsdoiorg101139e97-120

Gaines RR 2014 Burgess Shale-type preservation and its distribution in spaceand time Paleontological Society Papers 20 123ndash146 httpsdoiorg101017S1089332600002837

Gaines RR Briggs DEG amp Zhao Y 2008 Cambrian Burgess Shale-typedeposits share a common mode of fossilizationGeology 36 755ndash758 httpsdoiorg101130G24961A1

Glazer BT amp Rouxel OJ 2009 Redox speciation and distribution withindiverse iron-dominated microbial habitats at Loihi SeamountGeomicrobiology Journal 26 606ndash622 httpsdoiorg10108001490450903263392

Golonka J amp Kiessling W 2002 Phanerozoic time scale and definition of timeslices In Kiessling W Fluumlgel E amp Golonka J (eds) Phanerozoic ReefPatterns SEPM Special Publications 72 11ndash20 httpsdoiorg102110pec02720011

Haas S de Beer D et al 2018 Low-light anoxygenic photosynthesis and FendashS-biogeochemistry in a microbial mat Frontiers in Microbiology 9 httpsdoiorg103389fmicb201800858

Hammarlund EU Gaines RR Prokopenko MG Qi C Hou X-G ampCanfield DE 2017 Early Cambrian oxygen minimum zone-like conditionsat Chengjiang Earth and Planetary Science Letters 475 160ndash168 httpsdoiorg101016jepsl201706054

Hammarlund EU Smith MP Rasmussen JA Nielsen AT Canfield DEamp Harper DAT 2019 The Sirius Passet Lagerstaumltte of North Greenland ndash ageochemical window on early Cambrian low-oxygen environments andecosystems Geobiology 17 12ndash26 httpsdoiorg101111gbi12315

Hammer Oslash Harper DAT amp Ryan PD 2001 PAST Paleontological StatisticsSoftware Package for Education and Data Analysis PalaeontologiaElectronica 4 1ndash9

Harper DAT 2006 The Ordovician biodiversification Setting an agenda formarine life Palaeogeography Palaeoclimatology Palaeoecology 232148ndash166 httpsdoiorg101016jpalaeo200507010

Higgins AK Ineson JR Peel JS Surlyk F amp Soslashnderholm M 1991 LowerPalaeozoic Franklinian Basin of North Greenland In Peel JS ampSoslashnderholm M (eds) Sedimentary basins of North Greenland GroslashnlandsGeologiske Undersoslashgelse Bulletin 160 71ndash139

Higgins AK Leslie AG amp Smith MP 2001 NeoproterozoicndashLowerPalaeozoic stratigraphical relationships in the marginal thin-skinned thrust beltof the East Greenland Caledonides comparisons with the foreland inScotland Geological Magazine 138 143ndash160 httpsdoiorg101017S0016756801005076

Holmes JD Garciacutea-Bellido D amp Lee MSY 2018 Comparisons betweenCambrian Lagerstaumltten assemblages using multivariate parsimony andBayesian methods Gondwana Research 55 30ndash41 httpsdoiorg101016jgr201710007



Hou X-g Siveter DJ et al 2017 The Cambrian Fossils of ChengjiangChina The Flowering of Early Animal Life 2nd Edition Wiley BlackwellChichester httpsdoiorg1010029781118896372

Ineson JR amp Peel JS 2011 Geological and depositional setting of the SiriusPasset Lagerstaumltte (Early Cambrian) North Greenland Canadian Journal ofEarth Sciences 48 1259ndash1281 httpsdoiorg101139e11-018

Jago JB Gehling JG Paterson JR amp Brock GA 2012 Cambrianstratigraphy and biostratigraphy of the Flinders Ranges and the north coast ofKangaroo Island South Australia Episodes 35 247ndash255

Karl DM McMurtry GM Malahoff A amp Garcia MO 1988 LoihiSeamount Hawaii a mid-plate volcano with a distinctive hydrothermalsystem Nature 335 532ndash535 httpsdoiorg101038335532a0

Lagebro L Stein M amp Peel JS 2009 A new lamellipedian arthropod fromthe Early Cambrian Sirius Passet Fauna of North Greenland Journal ofPaleontology 83 820ndash825 httpsdoiorg10166609-0111

Lavoie D Desrochers A Dix G Knight I amp Hersi OS 2012 The GreatAmerican Carbonate Bank in eastern Canada An overview In Derby JRFritz RD Longacre SA Morgan WA amp Sternbach CA (eds) The GreatAmerican Carbonate Bank The Geology and Economic Resources of theCambrianndashOrdovician Sauk Megasequence of Laurentia AAPG Memoirs98 499ndash523

Le Boudec A Ineson J Rosing M Doslashssing L Martineau F Leacutecuyer C ampAlbarede F 2014 Geochemistry of the Cambrian Sirius Passet LagerstaumltteNorthern Greenland Geochemistry Geophysics Geosystems 15 886ndash904httpsdoiorg1010022013GC005068

Levin L 2003 Oxygen minimum zone benthos Adaptation and communityresponse to hypoxia Oceanography and Marine Biology Annual Review 411ndash45

Long DGF 1989 Ella Bay Formation Early Cambrian shelf differentiation inthe Franklinian basin central eastern Ellesmere Island Arctic CanadaCanadianJournal of Earth Sciences 26 2621ndash2635 httpsdoiorg101139e89-223

Maacutengano MG Bromley RG Harper DAT Nielsen AT Smith MP ampVinther J 2012 Nonbiomineralized carapaces in Cambrian seafloorlandscapes (Sirius Passet Greenland) Opening a new window into earlyPhanerozoic benthic ecology Geology 40 519ndash522 httpsdoiorg101130G328531

Meert JG amp Lieberman BS 2008 The Neoproterozoic assembly of Gondwanaand its relationship to the EdiacaranndashCambrian radiation GondwanaResearch 14 5ndash21 httpsdoiorg101016jgr200706007

Morgan WA 2012 Sequence stratigraphy of the Great American CarbonateBank In Derby JR Fritz RD Longacre SA Morgan WA ampSternbach CA (eds) The Great American Carbonate Bank The Geology andEconomic Resources of the CambrianndashOrdovician Sauk Megasequence ofLaurentia AAPG Memoirs 98 37ndash82

Moysiuk J Smith MR amp Caron J-B 2017 Hyoliths are Palaeozoiclophophorates Nature 541 394ndash397 httpsdoiorg101038nature20804

Nielsen ML Rasmussen JA amp Harper DAT 2017 Sexual dimorphismwithin the stem-group arthropod Isoxys volucris from the Sirius PassetLagerstaumltte North Greenland Bulletin of the Geological Society of Denmark65 47ndash58

Ogg J Ogg G amp Gradstein FM 2016 AConcise Geologic Time Scale 2016Elsevier Amsterdam

Orr PJ Briggs DE amp Kearns SL 1998 Cambrian Burgess Shale animalsreplicated in clay minerals Science 281 1173ndash1175 httpsdoiorg101126science28153801173

Page A Gabbott S Wilby P amp Zalasiewicz J 2008 Ubiquitous BurgessShale-style lsquoclay templatesrsquo in low-grade metamorphic mudrocks Geology36 855ndash858 httpsdoiorg101130G24991A1

Palmer AR amp Peel JS 1981 Dresbachian trilobites and stratigraphy of theCass Fjord Formation western North Greenland Groslashnlands GeologiskeUndersoslashgelse Bulletin 141

Palmer AR amp Repina LN 1993 Through a glass darkly taxonomyphylogeny and biostratigraphy of the Olenellina University of KansasPaleontological Contributions New Series 3

Park TYS Kihm JH et al 2018 Brain and eyes of Kerygmachela revealprotocerebral ancestry of the panarthropod head Nature Communications 91019 httpsdoiorg101038s41467-018-03464-w

Paterson JR Garcia-Bellido DC Jago JB Gehling JG Lee MSY ampEdgecombe GD 2016 The Emu Bay Shale Konservat-Lagerstaumltte a view ofCambrian life from East Gondwana Journal of the Geological SocietyLondon 173 1ndash11 httpsdoiorg101144jgs2015-083

Peel JS 1988 Spirellus and related helically coiled microfossils (cyanobacteria)from the Lower Cambrian of North Greenland In Peel JS (ed) CambrianndashJurassic fossils trace fossils and stratigraphy from Greenland GroslashnlandsGeologiske Undersoslashgelse Rapport 137 5ndash32

Peel JS 2010a Articulated hyoliths and other fossils from the Sirius PassetLagerstaumltte (early Cambrian) of North Greenland Bulletin of Geosciences 85385ndash394 httpsdoiorg103140bullgeosci1207

Peel JS 2010b A corset-like fossil from the Cambrian Sirius Passet Lagerstaumltteof North Greenland and its implications for cycloneuralian evolution Journalof Paleontology 84 332ndash340 httpsdoiorg10166609-102R1

Peel JS 2017a Feeding behaviour of a new worm (Priapulida) from the SiriusPasset Lagerstaumltte (Cambrian series 2 stage 3) of North Greenland(Laurentia) Palaeontology 60 795ndash805 httpsdoiorg101111pala12316

Peel JS 2017b Molaria (Euarthropoda) from the Sirius Passet Lagerstaumltte(Cambrian Series 2 Stage 3) of North Greenland Bulletin of Geosciences 92133ndash142 httpsdoiorg103140bullgeosci1658

Peel JS 2017c Mineralized gutfills from the Sirius Passet Lagerstaumltte(Cambrian Series 2) of North Greenland GFF 139 83ndash91 httpsdoiorg1010801103589720161260051

Peel JS amp Higgins AK 1980 Fossils from the Paradisfjeld Group NorthGreenland fold belt Groslashnlands Geologiske Undersoslashgelse Rapport 101

Peel JS amp Ineson JR 2011 The extent of the Sirius Passet Lagerstaumltte (earlyCambrian) of North Greenland Bulletin of Geosciences 86 535ndash543 httpsdoiorg103140bullgeosci1269

Peel JS amp Stein M 2009 A new arthropod from the lower Cambrian SiriusPasset Fossil-Lagerstaumltte of North Greenland Bulletin of Geosciences 84625ndash630 httpsdoiorg103140bullgeosci1158

Peel JS Stein M amp Kristensen RM 2013 Life cycle and morphology of aCambrian stem-lineage loriciferan PLoS ONE 8 e73583 httpsdoiorg101371journalpone0073583

Peng S Babcock LE amp Cooper RA 2012 The Cambrian Period InGradstein FM Ogg JG Schmitz M amp Ogg G (eds) The Geological TimeScale Elsevier Amsterdam 437ndash488

Peters SE amp Gaines RR 2012 Formation of the lsquoGreat Unconformityrsquo as atrigger for the Cambrian explosion Nature 484 363ndash366 httpsdoiorg101038nature10969

Piper DZ amp Dean WE 2002 Trace-element deposition in the Cariaco BasinVenezuela shelf under sulfate-reducing conditions ndash a history of the localhydrography and global climate 20 Ka to the present US Geological SurveyProfessional Papers 1670

Poulton SW amp Canfield DE 2011 Ferruginous conditions A dominantfeature of the ocean through Earthrsquos history Elements 7 107ndash112 httpsdoiorg102113gselements72107

Poulton SW amp Raiswell R 2002 The low-temperature geochemical cycle ofiron From continental fluxes to marine sediment deposition AmericanJournal of Science 302 774ndash805 httpsdoiorg102475ajs3029774

Raine RJ amp Smith MP 2012 Sequence stratigraphy of the Scottish Laurentianmargin and recognition of the Saukmegasequence In Derby JR Fritz RDLongacre SA Morgan WA amp Sternbach CA (eds) The Great AmericanCarbonate Bank The geology and Economic Resources of the CambrianndashOrdovician Sauk Megasequence of Laurentia AAPG Memoirs 98 575ndash596

Raiswell R amp Canfield DE 1996 Rates of reaction between silicate iron anddissolved sulfide in Peru Margin sediments Geochimica et CosmochimicaActa 60 2777ndash2787 httpsdoiorg1010160016-7037(96)00141-X

Schieber J 2007 Microbial mats on muddy substrates ndash examples of possiblesedimentary features and underlying processes In Schieber J Bose PKEriksson PG Banerjee S Sarkar S Altermann W amp Catuneanu O (eds)Atlas of Microbial Mat Features Preserved within the Siliciclastic RockRecord Atlases in Geoscience 2 Elsevier Amsterdam 117ndash133

Scholz F Severmann S McManus J Noffke A Lomnitz U amp Hensen C2014 On the isotope composition of reactive iron in marine sediments Redoxshuttle versus early diagenesis Chemical Geology 389 48ndash59 httpsdoiorg101016jchemgeo201409009

Seilacher A 1999 Biomat-related lifestyles in the Precambrian Palaios 1486ndash93 httpsdoiorg1023073515363

Servais T amp Harper DAT 2018 The Great Ordovician BiodiversificationEvent (GOBE) definition concept and duration Lethaia 51 151ndash164httpsdoiorg101111let12259

Servais T Owen AW Harper DAT Kroumlger B amp Munnecke A 2010 TheGreat Ordovician Biodiversification Event (GOBE) the palaeoecologicaldimension Palaeogeography Palaeoclimatology Palaeoecology 29499ndash119 httpsdoiorg101016jpalaeo201005031

Sloss LL 1963 Sequences in the Cratonic Interior of North AmericaGeological Society of America Bulletin 74 93ndash114 httpsdoiorg1011300016-7606(1963)74[93SITCIO]20CO2

Smith MP amp Rasmussen JA 2008 CambrianndashSilurian development of theLaurentian margin of the Iapetus Ocean in Greenland and related areas InHiggins AK Gilotti JA amp Smith MP (eds) The Greenland CaledonidesEvolution of the Northeast Margin of Laurentia Geological Society ofAmerica Memoirs 202 137ndash167

Smith MP Rasmussen JA Robertson S Higgins AK amp Leslie AG 2004Lower Palaeozoic stratigraphy of the East Greenland Caledonides GeologicalSurvey of Denmark and Greenland Bulletin 6 5ndash28

Soper J amp Higgins AK 1987 A shallow detachment beneath the NorthGreenland fold belt implications for sedimentation and tectonics GeologicalMagazine 124 441ndash450 httpsdoiorg101017S0016756800017027

Soper J amp Higgins AK 1990 Models for the Ellesmerian mountain front inNorth Greenland a basin margin inverted by basement uplift Journal ofStructural Geology 12 83ndash97 httpsdoiorg1010160191-8141(90)90050-9

Stein M 2010 A new arthropod from the Early Cambrian of North Greenlandwith a lsquogreat appendagersquo-like antennula Zoological Journal of the LinneanSociety 158 477ndash500 httpsdoiorg101111j1096-3642200900562x

Stein M Peel JS Siveter DJ ampWilliams M 2010 Isoxys (Arthropoda) withpreserved soft anatomy from the Sirius Passet Lagerstaumltte lower Cambrian ofNorth Greenland Lethaia 43 258ndash265 httpsdoiorg101111j1502-3931200900189x

Stein M Budd GE Peel JS amp Harper DAT 2013 Arthroaspis n gen acommon element of the Sirius Passet Lagerstaumltte (Cambrian North



Greenland) sheds light on trilobite ancestry BMC Evolutionary Biology 1399 httpsdoiorg1011861471-2148-13-99

Strang KM Armstrong HA amp Harper DAT 2016a Minerals in the gutscoping a Cambrian digestive system Royal Society Open Science 3 160420httpsdoiorg101098rsos160420

Strang KM Armstrong HA Harper DAT amp Trabucho-Alexandre JP2016b The Sirius Passet Lagerstaumltte silica death masking opens the windowon the earliest mat ground community of the Cambrian explosion Lethaia 49631ndash643 httpsdoiorg101111let12174

Surlyk F amp Ineson J 1987 Aspect of Franklinian shelf slope and troughevolution and stratigraphy in North Greenland In Report on the 1985geological expedition to central and western North Greenland GroslashnlandsGeologiske Undersoslashgelse Rapport 133 41ndash58

Tarhan LG Hood AVS Droser ML Gehling JG amp Briggs DEG 2016Exceptional preservation of soft-bodied Ediacara biota promoted by silica-richoceans Geology 44 951ndash954 httpsdoiorg101130G385421

Taylor RS 2002 A new bivalved arthropod from the early Cambrian SiriusPasset fauna North Greenland Palaeontology 45 97ndash123 httpsdoiorg1011111475-498300229

Topper TP Greco F Hofmann A Beeby A amp Harper DAT 2018Characterization of kerogenous films and taphonomic modes of the SiriusPasset Lagerstaumltte GreenlandGeology 46 359ndash362 httpsdoiorg101130G399301

Torsvik TH 2009 BugPlates software (IGCP 503) With reconstructionsof Torsvik T H and Cocks LRM (2002ndash2009) Statoil Hydro Stavanger

Trettin HP Mayr U Long GDF amp Packard JJ 1991 Cambrian to EarlyDevonian basin development sedimentation and volcanism Arctic IslandsIn Trettin HP (ed) Geology of the Innuitian Orogen and Arctic Platform ofArctic Canada Geological Society of America Geology of North AmericaVolume E 165ndash238

Vannier J Liu J Lerosey-Aubril R Vinther J amp Daley AC 2014Sophisticated digestive systems in early arthropods Nature Communications5 3641 httpsdoiorg101038ncomms4641

Vidal G amp Peel JS 1993Acritarchs from the Lower Cambrian Buen Formationin North Greenland Groslashnlands Geologiske Undersoslashgelse Bulletin 164

Vinther J amp Nielsen C 2005 The Early Cambrian Halkieria is a molluscZoologica Scripta 34 81ndash89 httpsdoiorg101111j1463-6409200500177x

Vinther J Eibye-Jacobsen D amp Harper DAT 2011a An Early Cambrianstem polychaete with pygidial cirri Biology Letters 7 929ndash932 httpsdoiorg101098rsbl20110592

Vinther J Smith MP amp Harper DAT 2011b Vetulicolians from the LowerCambrian Sirius Passet Lagerstaumltte North Greenland and the polarity ofmorphological characteristics in basal deuterostomes Palaeontology 54711ndash719 httpsdoiorg101111j1475-4983201101034x

Vinther J Stein M Longrich NR amp Harper DAT 2014 A suspension-feeding anomalocarid from the Early CambrianNature 507 496ndash499 httpsdoiorg101038nature13010

Vinther J Porras L Young FJ Budd GE amp Edgecomble GD 2016 Themouth apparatus of the Cambrian gilled lobopodian Pambdelurion whitting-toni Palaeontology 59 841ndash849 httpsdoiorg101111pala12256

Webster M amp Hageman SJ 2018 Buenellus chilhoweensis n sp from theMurray Shale (lower Cambrian Chilhowee Group) of Tennessee the oldestknown trilobite from the Iapetan margin of Laurentia Journal ofPaleontology 92 442ndash458 httpsdoiorg101017jpa2017155

Williams M Siveter DJ amp Peel JS 1996 Isoxys (Arthropoda) from the EarlyCambrian Sirius Passet Lagerstaumltte North Greenland Journal ofPaleontology 70 947ndash954 httpsdoiorg101017S0022336000038646

Yang C Li X-H Zhu M Condon DJ amp Chen J 2018 Geochronologicalconstraint on the Cambrian Chengjiang biota South China Journal of theGeological Society London 175 659ndash666 httpsdoiorg101144jgs2017-103

Young FJ amp Vinther J 2017 Onychophoran-like myoanatomy of theCambrian gilled lobopodian Pambdelurion whittingtoni Palaeontology 6027ndash54 httpsdoiorg101111pala12269

Zhai D Ortega-Hernaacutendez J Wolfe JM Hou X Cao C amp Liu Y 2019Three-Dimensionally Preserved Appendages in an Early Cambrian Stem-Group Pancrustacean Current Biology 29 171ndash177e1 httpsdoiorg101016jcub201811060

Zhang X Liu W amp Zhao Y 2008 Cambrian Burgess Shale-type Lagerstaumlttenin south China distribution and significance Gondwana Research 14255ndash262 httpsdoiorg101016jgr200706008



regionally developed karst surface into a lower (180 m thick) unit ofstorm-dominated dolostones and an upper 100 m thick mixedcarbonatendashclastic succession of fluvial and shallow marine sedi-ments (Higgins et al 1991 Ineson amp Peel 2011)

The Portfjeld Formation thickens northwards towards thecontinental margin where it is 400ndash700 m thick and passes intoits deep-water equivalent the Paradisfjeld Group which is made upof dark siliciclastic and carbonate mudstones interbedded withcarbonate turbidites and debris-flow deposits some of whichcontain large olistoliths (Surlyk amp Ineson 1987 Higgins et al 1991Ineson amp Peel 2011) The presence of large-scale debris flows andolistoliths led Surlyk amp Ineson (1987) to infer the exposure of anescarpment bounding the Portfjeld Formation to the north and anintact example of the escarpment with abutting debris flows wasdocumented by Ineson amp Peel (2011) 2 km NE of the Sirius Passetlocality

The age of the Portfjeld FormationndashParadisfjeld Group has beenthe subject of some debate Dewing et al (2004) considered thePortfjeld Formation to be of Ediacaran age on the basis of regionalcorrelations but Peel (1988) described cyanobacteria he consideredto be of early Cambrian age and Peel amp Higgins (1980) documentedthe coeloscleritophoran Chancelloria and nonarticulated brachio-pods from the upper part of the Paradisfjeld Group The presence ofa disconformity within the formation suggests that both ages arecorrect the unit comprising an older Ediacaran component and ayounger early Cambrian part The latter stratigraphic unit suggests

that the younger part of this phase of basin development is no olderthan Cambrian Stage 2

The Portfjeld Formation is overlain unconformably by sand-stones and mudstones of the Buen Formation The boundary is wellexposed adjacent to the Sirius Passet locality where the upper partof the carbonates is deeply fretted by karstic erosion with deepgrykes vadose fissures and accompanying shallow phreatic tubesall of which are infilled by millet-seed quartz arenite This lithologyis also seen as a thin sheet overlying the Portfjeld Formationregionally and passing upwards into black mudstones and siltstonesof the basal Buen Formation (Fig 2) In the deep-water successionthe uppermost limestone conglomerate bed of the ParadisfjeldGroup has a distinctive quartz sand matrix (Higgins et al 1991)which is partly correlative with the erosion surface

The Buen Formation and its correlatives crop out extensivelyacross North Greenland The most inboard development insouthern Peary Land is up to 500 m thick and dominated bysandstones deposited on a tide- and storm-influenced shelf that passnorthwards to a more mudstone- and siltstone-dominated shelf tothe north where the unit is up to 700 m thick (Higgins et al 1991)Transgressive surfaces bound three coarsening-upward sequencesacross the shelf that show an overall deepening trend (Davis ampHiggins 1987 Ineson amp Peel 2011) Northwards the shelfsediments pass into the deep-water succession of thePolkorridoren Group where the turbidites and deep-water mud-stones of units 3 4 and 5 of Davis amp Higgins (1987) are correlatives

Fig 1 Maps of the palaeogeographical and geographical setting of the Sirius Passet Lagerstaumltte (a) Location of North Greenland in the early Cambrian atc 520 Ma constructed in Bugplates (Torsvik 2009) Circle indicates location of the Sirius Passet Lagerstaumltte (b) The eastern Franklinian Basin (modifiedfrom Ineson amp Peel 2011) Red box indicates position of (c) (c) The Sirius Passet locality at 82deg 4759rsquo N 42deg 1354rsquo W east of J P Koch Fjord ismarked with a red star (modified from Le Boudec et al 2014)


































































































































































































































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