The Folkeslunda Limestone is a thin

limestone Limestone is a type of carbonate rock, carbonate sedimentary rock which is the main source of the material Lime (material), lime. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphism (materials science) ...

and

mudstone Mudstone, a type of mudrock, is a fine-grained sedimentary rock whose original constituents were clays or muds. Mudstone is distinguished from ''shale'' by its lack of fissility.Blatt, H., and R.J. Tracy, 1996, ''Petrology.'' New York, New York, ...

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 ...

Sweden Sweden, formally the Kingdom of Sweden, is a Nordic countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. It borders Norway to the west and north, and Finland to the east. At , Sweden is the largest Nordic count ...

. The formation crops out on the island of

Öland Öland (, ; ; sometimes written ''Oland'' internationally) is the second-largest Swedish island and the smallest of the traditional provinces of Sweden. Öland has an area of and is located in the Baltic Sea just off the coast of Småland. ...

to the east of

Kalmar Kalmar (, , ) is a city in the southeast of Sweden, situated by the Baltic Sea. It had 41,388 inhabitants in 2020 and is the seat of Kalmar Municipality. It is also the capital of Kalmar County, which comprises 12 municipalities with a total of ...

, where Folkeslunda is located. Other exposures of the formation are in

Dalarna Dalarna (; ), also referred to by the English exonyms Dalecarlia and the Dales, is a (historical province) in central Sweden. Dalarna adjoins Härjedalen, Hälsingland, Gästrikland, Västmanland and Värmland. It is also bordered by Nor ...

Jämtland Jämtland () is a historical provinces of Sweden, province () in the centre of Sweden in northern Europe. It borders Härjedalen and Medelpad to the south, Ångermanland to the east, Lapland, Sweden, Lapland to the north and Trøndelag and Norw ...

and

Östergötland Östergötland (; English exonym: East Gothland) is one of the traditional provinces of Sweden (''landskap'' in Swedish) in the south of Sweden. It borders Småland, Västergötland, Närke, Södermanland and the Baltic Sea. In older English li ...

. The Folkeslunda Limestone was deposited in an open marine environment with an estimated water depth of in a eustatically transgressive phase. The formation preserves

fossils 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 preserved ...

dating back to the late

Darriwilian The Darriwilian is the upper stage of the Middle Ordovician. It is preceded by the Dapingian and succeeded by the Upper Ordovician Sandbian Stage. The lower boundary of the Darriwilian is defined as the first appearance of the graptolite species ' ...

( Lasnamägi stage in the regional stratigraphy) of the

Middle Ordovician The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era, and the second of twelve periods of the Phanerozoic Eon. The Ordovician spans 41.6 million years from the end of the Cambrian Period Ma (milli ...

period Period may refer to: Common uses * Period (punctuation) * Era, a length or span of time *Menstruation, commonly referred to as a "period" Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (o ...

, dating to 463.5 to 460.9 Ma. Several genera of

nautiloid Nautiloids are a group of cephalopods (Mollusca) which originated in the Late Cambrian and are represented today by the living ''Nautilus'' and ''Allonautilus''. Fossil nautiloids are diverse and species rich, with over 2,500 recorded species. Th ...

trilobite Trilobites (; meaning "three-lobed entities") are extinction, extinct marine arthropods that form the class (biology), class Trilobita. One of the earliest groups of arthropods to appear in the fossil record, trilobites were among the most succ ...

brachiopod Brachiopods (), phylum (biology), phylum Brachiopoda, are a phylum of animals that have hard "valves" (shells) on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear e ...

s and

ostracod Ostracods, or ostracodes, are a Class (biology), class of the crustacean, Crustacea (class Ostracoda), sometimes known as seed shrimp. Some 33,000 species (only 13,000 of which are extant taxon, extant) have been identified,Brandão, S.N.; Antoni ...

s were found in the maximum thick formation. Erratic blocks of the same formation are also found in Germany (

Mecklenburg-Vorpommern Mecklenburg-Vorpommern (MV; ; ), also known by its Anglicisation, anglicized name Mecklenburg–Western Pomerania, is a Federated state, state in the north-east of Germany. Of the country's States of Germany, sixteen states, Mecklenburg-Vorpom ...

) and along the

Vistula River The Vistula (; ) is the longest river in Poland and the ninth-longest in Europe, at in length. Its drainage basin, extending into three other countries apart from Poland, covers , of which is in Poland. The Vistula rises at Barania Góra ...

Bydgoszcz Bydgoszcz is a city in northern Poland and the largest city in the historical region of Kuyavia. Straddling the confluence of the Vistula River and its bank (geography), left-bank tributary, the Brda (river), Brda, the strategic location of Byd ...

and in

Żary Żary (, , , ) is a town in western Poland with 37,502 inhabitants (2019), situated in the Lubusz Voivodeship. It is the administrative seat of the Żary County and of the Gmina Żary within the county, though the town is not part of the gmina (c ...

Lower Silesia Lower Silesia ( ; ; ; ; ; ; ; ) is a historical and geographical region mostly located in Poland with small portions in the Czech Republic and Germany. It is the western part of the region of Silesia. Its largest city is Wrocław. The first ...

, Poland.

Description

Ordovician sedimentary rocks are exposed in patches across the southern half of Sweden. The northernmost exposure is surrounding the

Siljan Ring The Siljan Ring () is a prehistoric impact structure in Dalarna, central Sweden. It is one of the 15 largest known impact structures on Earth and the largest in Europe, with a diameter of about . The impact that created the Siljan Ring occurred ...

, a

Devonian The Devonian ( ) is a period (geology), geologic period and system (stratigraphy), system of the Paleozoic era (geology), era during the Phanerozoic eon (geology), eon, spanning 60.3 million years from the end of the preceding Silurian per ...

impact crater An impact crater is a depression (geology), depression in the surface of a solid astronomical body formed by the hypervelocity impact event, impact of a smaller object. In contrast to volcanic craters, which result from explosion or internal c ...

. Other outcrops are found west and south of

Örebro Örebro ( ; ) is the seventh-largest city in Sweden, the seat of Örebro Municipality, and capital of Örebro County. It is situated by the Närke Plain, near the lake Hjälmaren, a few kilometers inland along the small river Svartån, and ...

, northeast of Livköping, west and southwest of

Skövde Skövde () is a Urban areas in Sweden, locality and urban centre in Skövde Municipality and Västra Götaland County, in the Västergötland, Västergötland (Western Gothland region) in central southern Sweden. Skövde is situated around 150 k ...

and surrounding

Falköping Falköping () is a locality and the seat of Falköping Municipality in Västra Götaland County, Sweden. It had 16,350 inhabitants in 2010. History The town of Falköping was first spoken of in the Icelandic ''Rimbegla'' (around 1100 A.D.), ...

. Underlying the Granby crater, west of

Linköping Linköping ( , ) is a city in southern Sweden, with around 167,000 inhabitants as of 2024. It is the seat of Linköping Municipality and the capital of Östergötland County. Linköping is also the episcopal see of the Diocese of Linköping (Chu ...

, the Ordovician has a larger exposure. The southernmost Ordovician outcrops are situated in

Skåne Scania ( ), also known by its native name of Skåne (), is the southernmost of the historical provinces of Sweden, provinces () of Sweden. Located in the south tip of the geographical region of Götaland, the province is roughly conterminous w ...

, due east of

Lund Lund (, ;"Lund"
(US) and ) is a city in the provinces of Sweden, province of Scania, southern Swed ...

and at the southeastern tip of Sweden.Bergman et al., 2012 Most of the island of

consists of Ordovician sediments, where Folkeslunda is located, the namesake for the formation.Folkeslunda, Öland
/ref> Previous names for the formation were Upper Grey Orthoceratite Limestone, Chiron Limestone, Centaurus Limestone and Schroeteri Limestone (lower part). The type section is located in the southeastern part of the parish of Långlöt and the northeastern part of the parish of Runsten on Öland. The best section of the unit on Öland is in a quarry close to the road from Vedby to Bäcklunda, east of Hornsjön.Ebbestad et al., 2007, p.17 The formation is the uppermost unit in the traditional Orthoceras Limestone of Sweden, overlying the

Seby Limestone Seby may refer to: People * Seby B. Jones (1915–2002), American politician * Seby Zavala (born 1993), American baseball player Places * Seby, Öland, Sweden * Séby Séby (; ) is a Communes of France, commune in the Pyrénées-Atlantiques De ...

and the Folkesunda Limestone is overlain by the

Furudal Limestone Furudal is a small locality located in Rättvik Municipality, Dalarna County, Sweden Sweden, formally the Kingdom of Sweden, is a Nordic countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. It borders Norway t ...

.Ebbestad et al., 2007, p.10 The Folkeslunda Limestone dates to the Lasnamägi stage, part of the Purtse, belonging to the Virunian in the regional stratigraphy of Sweden, corresponding to a late

age of the Middle

Ordovician The Ordovician ( ) is a geologic period and System (geology), system, the second of six periods of the Paleozoic Era (geology), Era, and the second of twelve periods of the Phanerozoic Eon (geology), Eon. The Ordovician spans 41.6 million years f ...

.Ebbestad et al., 2007, p.11 The unit is thick in the Vikarby section and thick in the Kårgärde section of the western Siljan Ring.Holmer, 1989, p.11 In the Lunne section of

the unit is between thick.Karis & Larsson, 1982, p.70

Lithologies

Diversity evolution of Ordovician zooplanktonic organisms compared with global eustatic sea-level curve

The base of the formation is formed by a thick grey calcarenitic

bed, which is overlain by thin-bedded calcarenitic and calcilutitic limestones. The upper half of the formation consists of thick-bedded calcarenitic limestones. In Kårgärde, the formation comprises medium-bedded, coarse-grained, grey to dark grey

s with chamositic grains in some beds.Kårgärde
at

Fossilworks Fossilworks was a portal which provides query, download, and analysis tools to facilitate access to the Paleobiology Database, a large relational database assembled by hundreds of paleontologists from around the world. History Fossilworks was cr ...

.org Other parts of the formation contain finely nodular lime

s and mudstones,Vikarbyn
at

.org and thick-bedded, coarse grained, in part coquinoid grey to dark grey limestones. 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 b ...

of the limestone has been interpreted as reef platform

facies In geology, a facies ( , ; same pronunciation and spelling in the plural) is a body of rock with distinctive characteristics. The characteristics can be any observable attribute of rocks (such as their overall appearance, composition, or con ...

.Ebbestad et al., 2007, p.44 The

eustatic sea level The eustatic sea level (from Greek εὖ ''eû'', "good" and στάσις ''stásis'', "standing") is the distance from the center of the Earth to the sea surface. An increase of the eustatic sea level can be generated by decreasing glaciation, inc ...

change globally during deposition of the Folkeslunda Limestone was a transgression,Chen & Lindström, 1991, p.7 and based on the low implosion rate of fossil shells during fossilization, the water depth at time of deposition of the Folkeslunda Limestone has been estimated at .Chen & Lindström, 1991, p.14

Erratic boulders

Erratic boulders belonging to the formation have been found in

,Erratic block Mecklenburg-Vorpommern
at

.org Germany and

Lubusz Lebus () is a historic town in the Märkisch-Oderland District of Brandenburg, Germany. It is the administrative seat of '' Amt'' ("collective municipality") Lebus. The town, located on the west bank of the Oder river at the border with Poland, wa ...

and Kuyavia-Pomerania, Poland.Erratic block Lubusz
at

.orgErratic block Kuyavia-Pomerania
at

.org The German boulder was described by Schlotheim (1820) and Boll (1857). Boll's collection is fortunately preserved at the regional Müritz Museum of Waren, Mecklenburg. Dzik (1984) described and illustrated Ordovician nautiloids of the erratic boulders in Poland.Kröger, 2004, p.58

Paleontology

With respect to both fauna and lithology, the unit in the Siljan District resembles its development on Öland. The fauna shares many common species with the Seby Limestone, but is also distinct with respect to the cephalopods and hyolithids. Faunal differences with respect to the underlying formation were notes in the

phosphatic Phosphates are the naturally occurring form of the element phosphorus. In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthophosphor ...

fauna, although the dominant species is the same as in the Seby Limestone. Trilobites from the Folkeslunda Limestone were described by Holm (1883) and Törnquist (1884), while Janusson (1957) described ostracods. Species of nautiloid cephalopods were reported by Holm in 1896, Troedsson (1931, 1932), and Kröger (2004). Biostratigraphically, the Folkeslunda Limestone spans the '' Pygodus serra''

conodont Conodonts, are an extinct group of marine jawless vertebrates belonging to the class Conodonta (from Ancient Greek κῶνος (''kōnos''), meaning " cone", and ὀδούς (''odoús''), meaning "tooth"). They are primarily known from their hard ...

zone and the '' Eoplacoghnathus reclinatus'' subzone.

Correlations

The '' Eoplacoghnathus reclinatus'' subzone extends from the lowermost part of the Folkeslunda Limestone into the lower part of the Furudal Limestone. The subzone index species is not common outside

Baltoscandia Baltoscandia or the Baltoscandian Confederation is a geopolitical concept of a Baltic–Scandinavian ( Nordic) union comprising Denmark, Estonia, Finland, Iceland, Latvia, Lithuania, Norway, and Sweden. The idea was proposed by a Swedish Profes ...

but has been recorded from a few localities in eastern North America (Bergström 1973), Argentina (Albanesi & Ortega 2002), and China (Zhang 1998).Ebbestad et al., 2007, p.32

Fossil content

Middle Ordovician South Polar paleogeography - 460 Ma

The following fossils have been found in the rocks belonging to the formation:

References

Bibliography

* * * * * * * * {{citation , last1=Karis , first1=Lars , last2=Larsson , first2=Kent , year=1982 , title=Jämtland Road Log , publisher=N.N. , pages=64–76