Agardhfjellet Formation
Agardhfjellet Formation | ||
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Ma | ||
Approximate paleocoordinates 69°36′N 16°18′E / 69.6°N 16.3°E | | |
Region | Svalbard | |
Country | Norway | |
Extent | Central Spitsbergen Basin |
The Agardhfjellet Formation is a
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 may have been present at least in the winter. [7][8]
These sites represent shallow-water
Paleobiota
Color key
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Notes Uncertain or tentative taxa are in small text; |
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]
Vertebrates
Bony fish
Bony fish from the Agardhfjellet Formation
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Genus | Species | Location | Member | Material | Notes | Images |
Leptolepis[11] | L. nathorsti | Oppdalssåta & Lardyfjellet Members |
Plesiosaurs
Plesiosaurs from the Agardhfjellet Formation | ||||||
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Genus | Species | Location | Member | Material | Notes | Images |
T. svalbardensis |
Slottsmøya Member |
Reassigned to the genus Colymbosaurus after further analysis[12] | ||||
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
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Genus | Species | Location | Member | Material | Notes | Images |
Cryopterygius | C. kristiansenae | Slottsmøya Member | Junior synonym of Undorosaurus gorodischensis | |||
Undorosaurus | U. gorodischensis | Slottsmøya Member | A single, largely complete specimen | A large | ||
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. [14] | ||
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.[15] | |||
Brachypterygius | B. sp. | Slottsmøya Member | Partial skull | Referred to Brachypterygius by Angst et al. (2010)[16] |
Invertebrates
An unnamed galatheid squat lobster is known from a single, poorly preserved fragment.[5]
Cephalopods
Large belemnoid arm hooks are known.[17]
Cephalopods from the Agardhfjellet Formation | ||||||
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Genus | Species | Location | Member | Material | Notes | Images |
Craspedites[18] | 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 | ||||||
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Genus | Species | Location | Member | Material | Notes | Images |
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 | ||||||
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Genus | Species | Location | Member | Material | Notes | Images |
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
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Oxytoma | O. octavia | Slottsmøya Member | ||||
Pseudolimea | P. arctica | Slottsmøya Member | ||||
Dacromya
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D. chetaensis | Slottsmøya Member | Rare | |||
Goniomya | G. literata | Slottsmøya Member | Rare |
Serpulids
Serpulids from the Agardhfjellet Formation
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Genus | Species | Location | Member | Material | Notes | Images |
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 | ||||||
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Genus | Species | Location | Member | Material | Notes | Images |
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
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Genus | Species | Location | Member | Material | Notes | Images |
Ambercyclus | A. sp. | Slottsmøya Member | The most abundant species of gastropod that is known from the Slottsmøya seep deposits
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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
- ^ Connors, Marisa Leigh (2017). Deciphering the Late Jurassic paleoenvironment through Re-Os isotope geochemistry of the Agardhfjellet Formation, Svalbard (Thesis). Colorado State University.
- ^ Delsett et al., 2019, p.741
- ^ a b c Agardhfjellet Formation at Fossilworks.org
- ISSN 0029-196X.
- ^ .
- ^ ]
- .
- .
- PMID 30345178.
- ^ PMID 32266112.
- hdl:10852/71055.
- ^ 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
- S2CID 91912834.
- PMID 31106052.
- .
- .
- .
- .
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. 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. 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. 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. .