Vardebukta Formation
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The Vardebukta 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
Norway Norway, officially the Kingdom of Norway, is a Nordic countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. The remote Arctic island of Jan Mayen and the archipelago of Svalbard also form part of the Kingdom of ...
. It preserves
fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...
s dating back to the
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 251.9 Ma and 249.9 Ma (million years ago). The Induan is so ...
stage Stage, stages, or staging may refer to: Arts and media Acting * Stage (theatre), a space for the performance of theatrical productions * Theatre, a branch of the performing arts, often referred to as "the stage" * ''The Stage'', a weekly Brit ...
(early
Early Triassic The Early Triassic is the first of three epochs of the Triassic Period of the geologic timescale. It spans the time between 251.9 Ma and Ma (million years ago). Rocks from this epoch are collectively known as the Lower Triassic Series, which ...
). Outcrops are known from the
Hornsund Hornsund is a fjord on the western side of the southernmost tip of northern Norway's Spitsbergen island. The fjord's mouth faces west to the Greenland Sea, and is wide. The length is , the mean depth is , and the maximal depth is . Hornsund cut ...
area but also from
Bellsund Bellsund is a long sound on the west coast of Spitsbergen, part of the Svalbard archipelago of Norway. It is separated from Van Mijenfjorden by the islands of Akseløya and Mariaholmen. Bellsund is located south of Nordenskiöld Land and north ...
and Isfjorden areas.


Subunits

The Vardebukta Formation is divided into the Urnetoppen Member and the overlying Wibebreen Member. Both members are of marine origin. They were deposited in a
sublittoral The littoral zone, also called litoral or nearshore, is the part of a sea, lake, or river that is close to the shore. In coastal ecology, the littoral zone includes the intertidal zone extending from the high water mark (which is rarely in ...
to shallow-
neritic The neritic zone (or sublittoral zone) is the relatively shallow part of the ocean above the drop-off of the continental shelf, approximately in depth. From the point of view of marine biology it forms a relatively stable and well-illuminated ...
environment. The Vardebukta Formation represents the oldest
Mesozoic The Mesozoic Era is the Era (geology), era of Earth's Geologic time scale, geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceous Period (geology), Periods. It is characterized by the dominance of archosaurian r ...
formation in Svalbard.


Urnetoppen Member

The Urnetoppen Member, which is approximately 30 meter thick in the
Hornsund Hornsund is a fjord on the western side of the southernmost tip of northern Norway's Spitsbergen island. The fjord's mouth faces west to the Greenland Sea, and is wide. The length is , the mean depth is , and the maximal depth is . Hornsund cut ...
area, consists of greenish
shales Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g., kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especial ...
,
siltstone Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility. Although its permeabil ...
and fine-grained
sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...
, occasionally with
clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolinite, ). Most pure clay minerals are white or light-coloured, but natural clays show a variety of colours from impuriti ...
-
ironstone Ironstone is a sedimentary rock, either deposited directly as a ferruginous sediment or created by chemical replacement, that contains a substantial proportion of an iron ore compound from which iron (Fe) can be smelted commercially. Not to be c ...
nodules Nodule may refer to: *Nodule (geology), a small rock or mineral cluster *Manganese nodule, a metallic concretion found on the seafloor *Nodule (medicine), a small aggregation of cells *Root nodule Root nodules are found on the roots of plants, p ...
. In the
Hornsund Hornsund is a fjord on the western side of the southernmost tip of northern Norway's Spitsbergen island. The fjord's mouth faces west to the Greenland Sea, and is wide. The length is , the mean depth is , and the maximal depth is . Hornsund cut ...
area, it rests paraconformably on the
Permian The Permian ( ) is a geologic period and System (stratigraphy), stratigraphic system which spans 47 million years, from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.902 Mya. It is the s ...
Kapp Starostin Formation. The Urnetoppen Member is correlated with the Deltadalen Member of the Vikinghøgda Formation, which is of
Dienerian 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 251.9 Ma and 249.9 Ma (million years ago). The Induan is sometim ...
(late Induan) age. The top of the Urnetoppen Member contains the so-called Brevassfjellet '' Myalina'' beds, a 5–6 meter thick, fossiliferous conglomerate.


Wibebreen Member

The Wibebreen Member is ca. 90–100 meter thick in the Hornsund area. It consists of black to light-grey coloured shales, marly shales,
arenaceous Arenite (from the Latin ''arena'', "sand") is a sedimentary clastic rock with sand grain size between 0.0625 mm (0.00245 in) and 2 mm (0.08 in) and containing less than 15% matrix. The related adjective is ''arenaceous''. The e ...
marls and siltstone. The lower part of this member contains mainly siltsone layers. The locally developed Skilisen ''Retzia'' Limestone belongs to the uppermost part of the Wibebreen Member. The Wibebreen Member is overlain by the Smithian (early
Olenekian In the geologic timescale, the Olenekian is an age (geology), age in the Early Triassic epoch (geology), epoch; in chronostratigraphy, it is a stage (stratigraphy), stage in the Lower Triassic series (stratigraphy), series. It spans the time betw ...
) aged Lusitaniadalen Member (="Sticky Keep Member") of the Vikinghøgda Formation.


Paleobiota

Fossiliferous layers of the Vardebukta Formation are concentrated to the uppermost part of the Urnetoppen Member ( Brevassfjellet ''Myalina'' beds). These
Dienerian 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 251.9 Ma and 249.9 Ma (million years ago). The Induan is sometim ...
aged beds have yielded the
bivalve Bivalvia () or bivalves, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class (biology), class of aquatic animal, aquatic molluscs (marine and freshwater) that have laterally compressed soft bodies enclosed b ...
s ''Myalina'' and '' Anodontophora'',
crinoids Crinoids are marine invertebrates that make up the class Crinoidea. Crinoids that remain attached to the sea floor by a stalk in their adult form are commonly called sea lilies, while the unstalked forms, called feather stars or comatulids, are ...
,
conodonts Conodonts, are an extinct group of marine jawless vertebrates belonging to the Class (biology), class Conodonta (from Ancient Greek κῶνος (''kōnos''), meaning "cone", and ὀδούς (''odoús''), meaning "tooth"). They are primarily known ...
, numerous isolated fish remains, and
trace fossils A trace fossil, also called an ichnofossil (; ), is a fossil record of biological activity by lifeforms, but not the preserved remains of the organism itself. Trace fossils contrast with body fossils, which are the fossilized remains of part ...
.


Fish

The isolated fish teeth of
bony Bony may refer to: * Adjective relating to bone People * Bony Dashaco, Cameroonian businessman * Bony King, Belgian singer-songwriter * Bony Pierre (born 1991), Haitian footballer * Bony Ramirez (born 1996), Dominican-born American painter and ...
and
cartilaginous fishes Chondrichthyes (; ) is a class of jawed fish that contains the cartilaginous fish or chondrichthyans, which all have skeletons primarily composed of cartilage. They can be contrasted with the Osteichthyes or ''bony fish'', which have skeletons p ...
have been described from the Brevassfjellet ''Myalina'' Bed (upper Urnetoppen Member of the Vardebukta Formation) of Hyrnefjellet,
Hornsund Hornsund is a fjord on the western side of the southernmost tip of northern Norway's Spitsbergen island. The fjord's mouth faces west to the Greenland Sea, and is wide. The length is , the mean depth is , and the maximal depth is . Hornsund cut ...
.. The bony fish teeth are mostly tentatively referred to ''
Saurichthys ''Saurichthys'' (from , 'lizard' and 'fish') is an extinct genus of predatory Actinopterygii, ray-finned fish from the Triassic period (geology), Period. It is the type genus of the family (taxonomy), family Saurichthyidae (Changhsingian-Ju ...
'' sp.


See also

* List of fossiliferous stratigraphic units in Norway


References

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