Vikinghøgda Formation
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The Vikinghøgda Formation is a
geologic formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...
in Svalbard,
Norway Norway, officially the Kingdom of Norway, is a Nordic country in Northern Europe, the mainland territory of which comprises the western and northernmost portion of the Scandinavian Peninsula. The remote Arctic island of Jan Mayen and the ...
. It preserves fossils dating back to the
Early Triassic The Early Triassic is the first of three epochs of the Triassic Period of the geologic timescale. It spans the time between Ma and Ma (million years ago). Rocks from this epoch are collectively known as the Lower Triassic Series, which is a un ...
(
Griesbachian The Induan is the first age of the Early Triassic epoch in the geologic timescale, or the lowest stage of the Lower Triassic series in chronostratigraphy. It spans the time between 251.902 Ma and Ma (million years ago). The Induan is sometime ...
-
Spathian In the geologic timescale, the Olenekian is an age in the Early Triassic epoch; in chronostratigraphy, it is a stage in the Lower Triassic series. It spans the time between Ma and Ma (million years ago). The Olenekian is sometimes divided int ...
)
period Period may refer to: Common uses * Era, a length or span of time * Full stop (or period), a punctuation mark Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (or rhetorical period), a concept ...
. It is split into three
members Member may refer to: * Military jury, referred to as "Members" in military jargon * Element (mathematics), an object that belongs to a mathematical set * In object-oriented programming, a member of a class ** Field (computer science), entries in ...
, from oldest to youngest: the Deltadalen Member (
Induan The Induan is the first age of the Early Triassic epoch in the geologic timescale, or the lowest stage of the Lower Triassic series in chronostratigraphy. It spans the time between 251.902 Ma and Ma (million years ago). The Induan is sometime ...
), Lusitaniadalen Member ( Smithian), and Vendomdalen Member (
Spathian In the geologic timescale, the Olenekian is an age in the Early Triassic epoch; in chronostratigraphy, it is a stage in the Lower Triassic series. It spans the time between Ma and Ma (million years ago). The Olenekian is sometimes divided int ...
). The formation can be found in central and southern Spitsbergen, as well as the smaller islands of
Barentsøya Barentsøya, sometimes anglicized as Barents Island, is an island in the Svalbard archipelago of Norway, lying between Edgeøya and Spitsbergen. Barents Island has no permanent human inhabitants. Named for the Dutch explorer Willem Barents (who ...
and
Edgeøya Edgeøya (), occasionally anglicised as Edge Island, is a Norwegian island located in southeast of the Svalbard archipelago; with an area of , it is the third-largest island in this archipelago. An Arctic island, it forms part of the Søraust-S ...
. The type locality is positioned in the vicinity of Vikinghøgda and Sticky Keep, two low peaks along the southeast edge of the
Sassendalen Sassendalen is a valley at Spitsbergen, Svalbard. The valley is among the largest valleys of Svalbard, and continues westwards into Sassenfjorden. Part of the valley divides Sabine Land and Nordenskiöld Land Nordenskiöld Land is the land area ...
valley in Spitsbergen. The two upper members of the Vikinghøgda Formation were previously grouped together as the Sticky Keep Formation.


Subunits

The Vikinghøgda Formation is formed by fine-grained marine sediments, such as mudstones, shales, siltstones, and fine sandstones. There is a trend of finer sediments, deeper waters, and higher organic content through the formation. Though fossils are only abundant in the middle part (Lusitaniadalen Member) of the formation,
index fossils Biostratigraphy is the branch of stratigraphy which focuses on correlating and assigning relative ages of rock strata by using the fossil assemblages contained within them.Hine, Robert. “Biostratigraphy.” ''Oxford Reference: Dictionary of Bio ...
can be found throughout the whole formation. The Vikinghøgda Formation is one of the better records of Early Triassic
chronostratigraphy Chronostratigraphy is the branch of stratigraphy that studies the ages of rock strata in relation to time. The ultimate aim of chronostratigraphy is to arrange the sequence of deposition and the time of deposition of all rocks within a geologic ...
in the Boreal realm, owing to a combination of continuous sedimentation, distinctive index fossils,
palynomorph Palynology is the "study of dust" (from grc-gre, παλύνω, palynō, "strew, sprinkle" and ''-logy'') or of "particles that are strewn". A classic palynologist analyses particulate samples collected from the air, from water, or from deposit ...
stratigraphy,
magnetostratigraphy Magnetostratigraphy is a geophysical correlation technique used to date sedimentary and volcanic sequences. The method works by collecting oriented samples at measured intervals throughout the section. The samples are analyzed to determine their '' ...
, and trace metal
cyclostratigraphy Cyclostratigraphy is a subdiscipline of stratigraphy that studies astronomically forced climate cycles within sedimentary successions. Orbital changes Astronomical cycles (also known as Milankovitch cycles) are variations of the Earth's or ...
.


Deltadalen Member

The Deltadalen Member is named after the small stream valley which runs between Vikinghøgda and Sticky Keep. The member consists of about 70 meters of silty shales and fine sandstones, lying above the eroded surface of the Permian-age Kapp Starostin Formation. Some of the sandstone beds may be
glauconitic Glauconite is an iron potassium phyllosilicate (mica group) mineral of characteristic green color which is very friable and has very low weathering resistance. It crystallizes with a monoclinic geometry. Its name is derived from the Greek () me ...
or
hummocky In geology, a hummock is a small knoll or mound above ground.Bates, Robert L. and Julia A. Jackson, ed. (1984). “hummock.” Dictionary of Geological Terms, 3rd Ed. New York: Anchor Books. p. 241. They are typically less than in height and ...
, and
calcareous Calcareous () is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines. In zoology ''Calcareous'' is used as an ad ...
nodules may be present. Fossils are rare and restricted to these nodules, though they include a variety of
silicified In geology, petrifaction or petrification () is the process by which organic material becomes a fossil through the replacement of the original material and the filling of the original pore spaces with minerals. Petrified wood typifies this proce ...
ammonoids Ammonoids are a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs, commonly referred to as ammonites, are more closely related to living coleoids (i.e., octopuses, squid and cuttlefish) ...
,
conodonts Conodonts (Greek ''kōnos'', "cone", + ''odont'', "tooth") are an extinct group of agnathan (jawless) vertebrates resembling eels, classified in the class Conodonta. For many years, they were known only from their tooth-like oral elements, which ...
, bivalves, and
gastropods The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. The ...
. Some index fossils have biostratigraphic significance, such as the ammonoid '' Otoceras boreale'' and the conodonts '' Neogondolella carinata'' and '' Neospathodus svalbardensis''. These species constrain the member to the Induan stage, between the early Griesbachian and early Dienerian substages. The sandiest intervals can be found at the base and the top of the member. The
depositional environment In geology, depositional environment or sedimentary environment describes the combination of physical, chemical, and biological processes associated with the deposition of a particular type of sediment and, therefore, the rock types that will be ...
is reconstructed as a shallow marine setting influenced by storms and nearby
deltaic A river delta is a landform shaped like a triangle, created by deposition of sediment that is carried by a river and enters slower-moving or stagnant water. This occurs where a river enters an ocean, sea, estuary, lake, reservoir, or (more rarel ...
sediments. The Deltadalen Member has been equated with two other Induan-age formations in its vicinity: the Vardebukta Formation (exposed in western Spitsbergen) and the Havert Formation (under the
Barents Sea The Barents Sea ( , also ; no, Barentshavet, ; russian: Баренцево море, Barentsevo More) is a marginal sea of the Arctic Ocean, located off the northern coasts of Norway and Russia and divided between Norwegian and Russian territo ...
). A 2020 study reported that the Permian-Triassic boundary occurs near the start of the Deltadalen Member. This was supported by several lines of evidence. The conodont '' Hindeodus parvus'', which defines the base of the Triassic, was reported from a sediment layer 4.1 meters above the base of the member. An overlying
tephra Tephra is fragmental material produced by a volcanic eruption regardless of composition, fragment size, or emplacement mechanism. Volcanologists also refer to airborne fragments as pyroclasts. Once clasts have fallen to the ground, they re ...
bed was dated to 252.13 ± 0.62 Ma via U-Pb radiometric dating, an age which is congruent with other reported estimates for the boundary.


Lusitaniadalen Member

The Lusitaniadalen Member is named after a glacier on the western flank of Vikinghøgda. The member is about 90 meters thick, mostly composed of laminated silty mudstones. Sandstone beds are less common, though when they occur, they are hummocky. Fossiliferous calcareous nodules are abundant in the sandstone-bearing layers, encasing well-preserved fossils of both invertebrates and vertebrates. The ammonoid index fossils '' Euflemingites romunderi'' and '' Wasatchites tardus'' indicate that the Lusitaniadalen Member was deposited during the Smithian substage of the Olenekian stage. Fish and amphibian fossils have also been found in this member, particularly at the "Fish Niveau" bonebed. The depositional environment corresponds to a deeper and calmer conditions, indicative of a major transgression (sea level rise) affecting the continental shelf. The Lusitaniadalen Member has been equated with the Iskletten Member of the Tvillingodden Formation (in western Spitsbergen) and the lower part of the Klappmyss Formation (under the Barents Sea). It has also been previously described as the Iskletten Member of the Sticky Keep Formation.


Vendomdalen Member

Dark shale (laminated mudstone) dominates the 90-meter-thick Vendomdalen Member, though silty yellowish
dolomitic Dolomite () is an anhydrous carbonate mineral composed of calcium magnesium carbonate, ideally The term is also used for a sedimentary carbonate rock composed mostly of the mineral dolomite. An alternative name sometimes used for the dolomiti ...
beds also occur. Very large dolomite nodules or
lenses A lens is a transmissive optical device which focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (''elements''), ...
, some over a meter in width, can also be found in this member. However, fossil-bearing concretions are rarer and more deformed than in the Lusitaniadalen Member. Fossils include abundant bivalves and Spathian ammonoid index fossils, such as '' Bajarunia euomphala'', '' Keyserlingites subrobustus'', and '' Parasibirites elegans''. Marine reptile and fish bonebeds also occur in the Vendomdalen Member, the two most prominent being the older "''Grippia'' Niveau" and younger "Lower Saurian Niveau". The Vendomdalen Member corresponds to the deepest part of the continental shelf, with high organic matter deposition and no influence from storm events. The Vendomdalen Member has been equated with the Kaosfjellet Member of the Tvillingodden Formation (in western Spitsbergen) and the upper part of the Klappmyss Formation (under the Barents Sea). It has also been previously described as the Kaosfjellet Member of the Sticky Keep Formation.


Paleobiota


Reptiles


Amphibians


Fish

A diverse fish assemblage has been described from the "Sticky Keep Formation", including
lungfish Lungfish are freshwater vertebrates belonging to the order Dipnoi. Lungfish are best known for retaining ancestral characteristics within the Osteichthyes, including the ability to breathe air, and ancestral structures within Sarcopterygii, i ...
,
coelacanths The coelacanths ( ) are fish belonging to the order Actinistia that includes two extant species in the genus ''Latimeria'': the West Indian Ocean coelacanth (''Latimeria chalumnae''), primarily found near the Comoro Islands off the east coast ...
,
chondrosteans Chondrostei is a group of non-neopterygian ray-finned fish, while the term originally referred to a paraphyletic group of all non-neopterygian ray-finned fish, it was redefined by Patterson in 1982 to be a clade comprising the Acipenseriformes (w ...
, and
hybodont Hybodontiformes, commonly called hybodonts, are an extinct group of shark-like chondrichthyans, which existed from the late Devonian to the Late Cretaceous. They form the group of Elasmobranchii closest to neoselachians, the clade of modern shar ...
sharks.


See also

*
List of fossiliferous stratigraphic units in Norway See also * Lists of fossiliferous stratigraphic units in Europe ** List of fossiliferous stratigraphic units in Denmark ** List of fossiliferous stratigraphic units in Scotland See also *Lists of fossiliferous stratigraphic units in ...


References

Geologic formations of Norway Triassic System of Europe Triassic Norway Induan Stage Olenekian Stage Mudstone formations Siltstone formations Shale formations Sandstone formations Geology of Svalbard {{Triassic-stub