Agardhfjellet Formation

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

Agardhfjellet Formation Stratigraphic range: Tithonian-Berriasian ~150–140 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Geologic map of central Svalbard with the formation in dark blue
Type	Formation
Sub-units	Oppdalsåta & Slottsmøya Members
Underlies	Rurikfjellet Formation
Overlies	Knorringfjellet Formation
Lithology
Primary	Mudstone
Other	Dolomite
Location
Coordinates	78.3°N 15.8°E / 78.3; 15.8
Approximate paleocoordinates	69.6°N 16.3°E / 69.6; 16.3
Region	Svalbard
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 sediments comprise mudstones, dolomites and shales deposited in an open to deep marine low oxygen environment. 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.[2]

Fossil content

The formation, and especially the Slottsmøya Member, has provided the following fossils:[2]

Vertebrates

Group	Taxa	Notes	Images
Ichthyosaurs	Cryopterygius kristiansenae	[3]
	Janusaurus lundi	[4]
	Keilhauia nui	[5]
	Palvennia hoybergeti	[3]
	Brachypterygius sp.	[6]
Plesiosaurs	Colymbosaurus svalbardensis	[7]
	Djupedalia engeri	[6]
	Ophthalmothule cryostea	[8]
	Spitrasaurus larseni	[6]
	S. wensaasi
Pliosaurs	Pliosaurus funkei ("Predator X", red)	[9]

Invertebrates

Bivalves[10]

• Mesosaccella rogovi
• Nucinella svalbardensis
• Pseudotrapezium aff. groenlandicum
• Buchia sp.

See also

• List of fossiliferous stratigraphic units in Norway
• Tithonian formations
• Berriasian formations

References

1. Delsett et al., 2019, p.741
2. Agardhfjellet Formation at Fossilworks.org
3. Druckenmiller et al., 2012
4. Roberts et al., 2014
5. Delsett et al., 2017
6. Knutsen et al., 2012a
7. Knutsen et al., 2012c
8. Roberts et al., 2020
9. Knutsen et al., 2012b
10. Hryniewicz et al., 2014

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.