Agardhfjellet Formation

The Agardhfjellet Formation is a geologic formation in Svalbard, Norway. It preserves fossils dating back to the Oxfordian to Berriasian stages, spanning the Late Jurassic-Early Cretaceous boundary.[1] The formation contains the Slottsmøya Member, a highly fossiliferous unit (Lagerstätte) where many ichthyosaur and plesiosaur fossils have been found, as well as abundant and well preserved fossils of invertebrates.[2][3]

Agardhfjellet Formation
Stratigraphic range: Oxfordian-Berriasian
~157.9–141 Ma
Geologic map of central Svalbard with the formation in dark blue
TypeFormation
Sub-unitsOppdalsåta & Slottsmøya Members
UnderliesRurikfjellet Formation
OverliesKnorringfjellet Formation
Lithology
PrimaryMudstone
OtherDolomite
Location
Coordinates78.3°N 15.8°E / 78.3; 15.8
Approximate paleocoordinates69.6°N 16.3°E / 69.6; 16.3
RegionSvalbard
Country Norway

Description

The formation overlies the Knorringfjellet Formation and is overlain by the Rurikfjellet Formation. The formation comprises the lower Oppdalsåta and upper Slottsmøya Members. The Slottsmøya Member, which averages 55 to 60 metres (180 to 197 ft) in thickness in the study area, consists of dark-grey to black silty mudstone, often weathering to paper shale, and discontinuous silty beds with local occurrences of red to yellowish sideritic concretions as well as siderite and dolomite interbeds.[3] It consists of a mix of shales and siltstones which were deposited in a shallow marine environment, near a patch of deeper marine sediment.[4] The seafloor, which was located about 150 metres (490 ft) below the surface, seems to have been relatively dysoxic, or oxygen-poor, although the diversity of the benthic fauna suggest that these environments were likely not truly anoxic and that oxygen-depletion may have been a seasonal phenomenon.[5][6] Although direct evidence from Slottsmøya is currently lacking, the high latitude of this site and relatively cool global climate of the Tithonian suggest that some sea ice was likely present at least in the winter. There is evidence for the presence of sea ice and glaciers from coeval deposits in eastern Europe and the Volga region of Russia (which shares a number of fauna with those known from the Slottsmøya Member), which were further south than Svalbard at the time.[7][8]

These sites represent shallow-water methane seeps which were spread over a relatively large geographic area, and like modern day seeps, they supported high biodiversity. Near the top of the member, various assemblages of invertebrates have been discovered; these include ammonites, bivalves, lingulate brachiopods, rhynchonellate brachiopods, tubeworms, belemnoids, tusk shells, sponges, crinoids, sea urchins, brittle stars, starfish, crustaceans, and gastropods, numbering 54 taxa in total. The most common and abundant of these taxa were bivalves and brachiopods, each of which make up 27.8% of the known seep fauna. Several chemosymbiotic species are known, such as the bivalve Nucinella.[5] Outside of the cold seeps, several non-seep-restricted invertebrates were also present in abundance.[6] In addition to the invertebrates, the Slottsmøya Member has also revealed a diverse assemblage of marine reptiles, including several taxa of ichthyosaurs and plesiosaurs. Many of these specimens are relatively complete and in articulation, which is rare among Jurassic marine fossil sites.[6] It thus provides a unique and detailed glimpse into the boreal seas of the Late Jurassic. As it spans the Jurassic-Cretaceous boundary, it is also important to understanding how marine ecosystems changed going into the Cretaceous.

Paleobiota

Color key
Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon
Notes
Uncertain or tentative taxa are in small text; crossed out taxa are discredited.

The formation, especially the Slottsmøya Member, has provided an abundance of marine fossils dating to the Late Jurassic-Early Cretaceous.[3]

The timeline below follows stratigraphic data provided in Delsett et al. 2018 and Roberts et al. 2020. [9][10]

NannopterygiusArthropterygiusArthropterygiusArthropterygiusUndorosaurusPliosaurusOphthalmothuleSpitrasaurusSpitrasaurusDjupedaliaColymbosaurus

Vertebrates

Some fragmentary remains of fish have been recovered.[1]

Plesiosaurs

Plesiosaurs from the Agardhfjellet Formation
GenusSpeciesLocationMemberMaterialNotesImages

Tricleidus

T. svalbardensis

Slottsmøya Member

Reassigned to the genus Colymbosaurus after further analysis[11]

Colymbosaurus C. svalbardensis Slottsmøya Member A colymbosaurine cryptoclidid, also known from the Kimmeridge Clay
Djupedalia D. engeri Slottsmøya Member A cryptoclidid plesiosaur
Ophthalmothule O. cryostea Slottsmøya Member Extensive skeletal material including a complete cranium A cryptoclidid plesisosaur which has unusually large orbits.[10]
Spitrasaurus S. wensaasi Slottsmøya Member A cryptoclidid plesiosaur related to Ophthalmothule
S. larseni
Pliosaurus P. funkei Slottsmøya Member Known from two partial skeletons A large thalassophonean pliosaurid which was informally known as "Predator X" prior to being named. This species is notable for having unusually large paddles in comparison to its body size.

Ichthyosaurs

Ichthyosaurs from the Agardhfjellet Formation
GenusSpeciesLocationMemberMaterialNotesImages
Cryopterygius C. kristiansenae Slottsmøya Member Junior synonym of Undorosaurus gorodischensis
Undorosaurus U. gorodischensis Slottsmøya Member A single, largely complete specimen A large platypterygiine ichthyosaur, also known from the Russian Volga.[12]
Janusaurus J. lundi Slottsmøya Member Junior synonym of Arthropterygius lundi
Palvennia P. hoybergeti Slottsmøya Member Junior synonym of A. hoybergeti
Keilhauia K. nui Slottsmøya Member A nomen dubium referred to A. sp. cf. chrisorum
Arthropterygius A. lundi Slottsmøya Member Several specimens of varying ages, previously referred to several other genera A widespread genus of ophthalmosaurid ichthyosaur, also known from Canada, Russia, and Argentina. Is present both before and directly after the Jurassic-Cretaceous Boundary. [13]
A. hoybergeti
A. chrisorum
Nannopterygius N. borealis Slottsmøya Member An ophthalmosaurid ichthyosaur present in early Cretaceous strata. This genus is also known from the Kimmeridge Clay and from fossil sites in the Volga.[14]
Brachypterygius B. sp. Slottsmøya Member Partial skull Referred to Brachypterygius by Angst et al. (2010)[15]

Invertebrates

An unnamed galatheid squat lobster is known from a single, poorly preserved fragment.[5]

Cephalopods

Large belemnoid arm hooks are known.[16]

Cephalopods from the Agardhfjellet Formation
GenusSpeciesLocationMemberMaterialNotesImages
Craspedites[17] C. okensis Slottsmøya Member
C. originalis
Borealites B. rossicus Slottsmøya Member
B. sp.
Hectoroceras H. kochi Slottsmøya Member
H. sp.
Kachpurites K. sp. Slottsmøya Member
Surites S. spasskensis Slottsmøya Member
S. spasskensoides
S. tzikwinianus
S. mesezhnikovi
Tollia T. tolli Slottsmøya Member

Echinoderms

Echinoderms from the Agardhfjellet Formation
GenusSpeciesLocationMemberMaterialNotesImages
Chariocrinus C. sp. Slottsmøya Member A form of isocrinid crinoid
Hemipedina H. sp. Slottsmøya Member A species of pedinoid sea urchins related to the extant Caenopedina
Polarasterias P. janusensis Slottsmøya Member Nearly complete specimen A forcipulatid sea star
Savignaster S. septemtrionalis Slottsmøya Member A pterasterid sea star
Ophiogaleus O. sp. Slottsmøya Member A ophiacanthid brittle star
Ophioculina O. hoybergia Slottsmøya Member An ophiurine brittle star

Bivalves

Remains of possible anomiid clams have been found which are as yet undescribed.

Bivalves from the Agardhfjellet Formation
GenusSpeciesLocationMemberMaterialNotesImages
Pseudotrapezium P. aff. groelandicum Slottsmøya Member An arcticid clam which constitutes nearly half of the fauna recovered from the seep assemblages.
Mesosaccella M. rogovi Slottsmøya Member
M. toddi
Nucinella N. svalbardensis Slottsmøya Member The most abundant chemosymbiotic species in the Spitsbergen seeps.
Buchia B. sp Slottsmøya Member
Solemya S. cf. woodwardiana Slottsmøya Member A burrowing chemosymbiotic bivalve which is very abundant in the seep sites
Tehamatea T. rasmusseni Slottsmøya Member A lucinid clam
Cretaxinus C. hurumi Slottsmøya Member A thyacirid clam
Camptonectes C. spp Slottsmøya Member A pectinid clam represented by at least two species
Oxytoma O. octavia Slottsmøya Member
Pseudolimea P. arctica Slottsmøya Member
Dacromya D. chetaensis Slottsmøya Member Rare
Goniomya G. literata Slottsmøya Member Rare

Serpulids

Serpulids from the Agardhfjellet Formation
GenusSpeciesLocationMemberMaterialNotesImages
Propomatoceros P. sp. Slottsmøya Member A serpulid tube worm
aff. Pyrgopolon aff. P. nodulosum Slottsmøya Member A serpulid tube worm which forms mass accumulations in the Echinoderm Bed
Nogrobs N. sp. Slottsmøya Member

Brachiopods

Brachiopods from the Agardhfjellet Formation
GenusSpeciesLocationMemberMaterialNotesImages
Lingularia L. similis Slottsmøya Member The most abundant species of brachiopod that is present in Slottsmøya
Ptilorhynchia P. mclachlani Slottsmøya Member A rhynchonellide brachiopod

Gastropods

Gastropods from the Agardhfjellet Formation
GenusSpeciesLocationMemberMaterialNotesImages
Ambercyclus A. sp. Slottsmøya Member The most abundant species of gastropod that is known from the Slottsmøya seep deposits
Hudlestoniella H. sp. Slottsmøya Member A rissoid gastropod
Cantrainea C. sp. Slottsmøya Member A turbinid gastropod; it is rare and only known from one of the seep sites

See also

References

  1. Connors, Marisa Leigh (2017). "Deciphering the Late Jurassic paleoenvironment through Re-Os isotope geochemistry of the Agardhfjellet Formation, Svalbard". Colorado State University.
  2. Delsett et al., 2019, p.741
  3. Agardhfjellet Formation at Fossilworks.org
  4. Hurum, J.H.; Nakrem, H.A.; Hammer, O.; Knutsen, E.M.; Druckenmiller, P.S.; Hryniewicz, K.; Novis, L.K. (2012). "An Arctic Lagerstätte – the Slottsmøya Member of the Agardhfjellet Formation (Upper Jurassic-Lower Cretaceous) of Spitsbergen" (PDF). Norwegian Journal of Geology. 92: 55–64. ISSN 0029-196X.
  5. Hryniewicz, K.; Nakrem, H.A.; Hammer, O.; Little, C.T.S.; Kaim, A.; S., M.R.; Hurum, J.H. (2015). "The palaeoecology of the latest Jurassic–earliest Cretaceous hydrocarbon seep carbonates from Spitsbergen, Svalbard". Lethaia. 48 (3): 353–374. doi:10.1111/let.12112.
  6. Delsett, L.L.; Novis, L.K.; Roberts, A.J.; Koevoets, M.J.; Hammer, O.; Druckenmiller, P.S.; Hurum, J.H. (2015). "The Slottsmøya marine reptile Lagerstätte: depositional environments, taphonomy and diagenesis" (PDF). In Kear, B.P.; Lindgren, J.; Hurum, J.H.; Milan, J.; Vajda, V. (eds.). Mesozoic Biotas of Scandinavia and its Arctic Territories. Geological Society, London, Special Publications. Geological Society of London, Special Publications. 434. pp. 165–188. doi:10.1144/SP434.2.
  7. Galloway, J.M.; Sweet, A.R.; Swindles, G.T.; Dewing, K.; Hadlari, T.; Embry, A.F.; Sanei, H. (June 2013). "Middle Jurassic to Lower Cretaceous paleoclimate of Sverdrup Basin, Canadian Arctic Archipelago inferred from the palynostratigraphy". Marine and Petroleum Geology. 44. doi:10.1016/j.marpetgeo.2013.01.001.
  8. Price, Gregory G. (1999). "The evidence and implications of polar ice during the Mesozoic". Earth-Science Reviews. 48 (3). doi:10.1016/S0012-8252(99)00048-3.
  9. Delsett, L.L.; Druckenmiller, P.S.; Roberts, A.J.; Hurum, J.H. (October 12, 2018). "A new specimen of Palvennia hoybergeti: implications for cranial and pectoral girdle anatomy in ophthalmosaurid ichthyosaurs". doi:10.7717/peerj.5776. Cite journal requires |journal= (help)
  10. Roberts, A.J.; Druckenmiller, P.S.; Cordonnier, B.; Delsett, L.L.; Hurum, J.H. (2020). "A new plesiosaurian from the Jurassic–Cretaceous transitional interval of the Slottsmøya Member (Volgian), with insights into the cranial anatomy of cryptoclidids using computed tomography". PeerJ. 8: e8652. doi:10.7717/peerj.8652.
  11. E. M. Knutsen, P. S. Druckenmiller, and J. Hurum. 2012. Redescription and taxonomic clarification of ‘Tricleidus’ svalbardensis based on new material from the Agardhfjellet Formation (Middle Volgian). Norwegian Journal of Geology 92:175-186
  12. Nikolay G. Zverkov; Vladimir M. Efimov (2019). "Revision of Undorosaurus, a mysterious Late Jurassic ichthyosaur of the Boreal Realm". Journal of Systematic Palaeontology. 17 (14): 963–993. doi:10.1080/14772019.2018.1515793.
  13. Zverkov, Nikolay G.; Prilepskaya, Natalya E. (2019). "A prevalence of Arthropterygius (Ichthyosauria: Ophthalmosauridae) in the Late Jurassic—earliest Cretaceous of the Boreal Realm". PeerJ. 7: e6799. doi:10.7717/peerj.6799. PMC 6497043. PMID 31106052.
  14. Nikolay G. Zverkov; Megan L. Jacobs (2020). "Revision of Nannopterygius (Ichthyosauria: Ophthalmosauridae): reappraisal of the 'inaccessible' holotype resolves a taxonomic tangle and reveals an obscure ophthalmosaurid lineage with a wide distribution". Zoological Journal of the Linnean Society. Online edition. doi:10.1093/zoolinnean/zlaa028.
  15. ANGST, D.; BUFFETAUT, E.; TABOUELLE, J.; TONG, H. (2010). "An ichthyosaur skull from the Late Jurassic of Svalbard". Bulletin de la Société Géologique de France. 181 (5). doi:10.2113/gssgfbull.181.5.453.
  16. HAMMER, Ø.; HRYNIEWICZ, K.; HURUM, J.H.; HØYBERGET, M.; KNUTSEN, E.M.; NAKREM, H.A. (4 May 2012). "Large onychites (cephalopod hooks) from the Upper Jurassic of the Boreal Realm". Acta Palaeontologica Polonica (58). doi:10.4202/app.2012.0020.
  17. Wierzbowski, A.; Hryniewicz, K.; Hammer, Ø.; Nakrem, H.A.; Little, C.T.S. (October 2011). "Ammonites from hydrocarbon seep carbonate bodies from the uppermost Jurassic – lowermost Cretaceous of Spitsbergen and their biostratigraphical importance". Neues Jahrbuch für Geologie und Paläontologie. 262. doi:10.1127/0077-7749/2011/0198.

Bibliography

  • Roberts, A.J.; P.S. Druckenmiller; B. Cordonnier; L.L. Delsett, and J.H. Hurum. 2020. A new plesiosaurian from the Jurassic-Cretaceous transitional interval of the Slottsmøya Member (Volgian), with insights into the cranial anatomy of cryptoclidids using computed tomography. PeerJ 8. e8652.
  • Delsett, L.L.; A.J. Roberts; P.S. Druckenmiller, and J.H. Hurum. 2019. Osteology and phylogeny of Late Jurassic ichthyosaurs from the Slottsmøya Member Lagerstätte (Spitsbergen, Svalbard). Acta Palaeontologica Polonica 64. 717–743.
  • Delsett, L.L.; A.J. Roberts; P.S. Druckenmiller, and J.H. Hurum. 2017. A New Ophthalmosaurid (Ichthyosauria) from Svalbard, Norway, and Evolution of the Ichthyopterygian Pelvic Girdle. PLoS ONE 12. e0169971. doi:10.1371/journal.pone.0169971 PMID 28121995 PMC 5266267
  • Hryniewicz, K.; C.T. Little, and H.A. Nakrem. 2014. Bivalves from the latest Jurassic-earliest Cretaceous hydrocarbon seep carbonates from central Spitsbergen, Svalbard. Zootaxa 3859. 1-66.
  • Roberts, A.J.; P.S. Druckenmiller; G.P. Sætre, and J.H. Hurum. 2014. A New Upper Jurassic Ophthalmosaurid Ichthyosaur from the Slottsmøya Member, Agardhfjellet Formation of Central Spitsbergen. PLoS ONE 9. e103152. doi:10.1371/journal.pone.0103152 PMID 25084533 PMC 4118863
  • Druckenmiller, P.S.; J.H. Hurum; E.M. Knutsen, and H.A. Nakrem. 2012. Two new ophthalmosaurids (Reptilia: Ichthyosauria) from the Agardhfjellet Formation (Upper Jurassic: Volgian/Tithonian), Svalbard, Norway. Norwegian Journal of Geology 92. 311–339. Accessed 2020-07-03. ISSN 0029-196X
  • Knutsen, E.M.; P.S. Druckenmiller, and J.H. Hurum. 2012a. A new plesiosauroid (Reptilia: Sauropterygia) from the Agardhfjellet Formation (Middle Volgian) of central Spitsbergen, Norway. Norwegian Journal of Geology 92. 213-234.
  • Knutsen, E.M.; P.S. Druckenmiller, and J.H. Hurum. 2012b. A new species of Pliosaurus (Sauropterygia: Plesiosauria) from the Middle Volgian of central Spitsbergen, Norway. Norwegian Journal of Geology 92. 235-258.
  • Knutsen, E.M.; P.S. Druckenmiller, and J.H. Hurum. 2012c. Redescription and taxonomic clarification of 'Tricleidus' svalbardensis based on new material from the Agardhfjellet Formation (Middle Volgian). Norwegian Journal of Geology 92. 175-186.
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