Sorthat Formation
Stratigraphy
On Bornholm, the lower-middle Jurassic succession is composed of the Rønne (Hettangian–Sinemurian), Hasle (lower–upper Pliensbachian), Sorthat and Bagå Formations. The major Pliensbachian–Bathonian coal-bearing clays and sands that overlie the Lower Pliensbachian Hasle Formation are distributed between both the Sorthat Formation and the overlaying Bagå Formation. The Sorthat Formation is the sister unit of the Röddinge Formation, with both being part of the same fluvial system, as well the regional equivalent of the Ciechocinek Formation of Baltic Germany and Poland, the Fjerritslev Formation of the Danish Basin and the Rya Formation on Scania. The Sorthat Formation beds were referred originally to the Levka, Sorthat and Bagå beds. A major section of the formation is the Korsodde coastal section, located on the southwest part of the island. A detailed stratigraphic interpretation of the beds has been difficult to achieve, in part due to the complicated block faulting, but especially due to the absence of marine fossils and distinct marker beds. The rocks were originally dated as Middle Jurassic using megaspore contents, with the Levka and Sorthat beds being roughly contemporaneous and the Bagå beds possibly slightly younger. Later, when more advanced palynological studies from locations such as the Levka-1 core-well and the Korsodde section Upper Pliensbachian stratum became available, the coals and clays of the Levka beds were removed from the Bagå Formation, as were the coal-dominated beds of the Korsodde and Onsbæk sections. At the time, several megaspores were found to be common in both the Bagå Formation and Sorthat beds, implying the presence of Toarcian–Aalenian strata, although the dating of the megaspore-bearing strata is tentative. With both, the palynological and sedimentological study of all available exposures and cores from the Lower–Middle Jurassic shows that the Hasle Formation (Lower–Middle Pliensbachian) is covered by a succession referable to both the Levka and Sorthat beds, which are composed mostly by bioturbated sands, heteroliths and clays along with abundant coal veins, and contain relatively diverse brackish to marine dinoflagellate assemblages that are indicative of upper Pliensbachian, Toarcian and possibly lower Aalenian strata. The upper stratum is covered by the fluvial gravels and sands, along with lacustrine clays, carbonaceous clays and coals belonging to the Bagå Formation.
Lithology
The Sorthat Formation has a highly variable lithology. The main core studied from the rocks, the Levka-1 well, reveal first sharp-based units fining upwards, 3–14 m thick, consisting of coarse-grained, occasionally pebbly sand, overlain by muddy, coal- and mica-containing, fine- to medium-grained sand that is laminated to homogeneous clay and coal seams with roots. On most of the strata there is a common parallel lamination with subordinate cross-bedding, cross-lamination and Flaser lamination. There are abundant large plant fragments and small bits of quartz. Marine palynomorphs are absent, suggesting that this level was deposited on a coastal or delta plain with fluvial channels, lakes and swamps. This is consistent with finds in the German portion of the Ciechocinek Formation, where a large deltaic system ended: the large Toarcian–Bajocian deltaic systems were the local shoreline, influenced by the proximity between brackish to freshwater and continental biofacies. The North German Basin shows that on an approximately 14.4 m.y. gap, four third-order sea-level fluctuations led the subsequent formation of four individual delta generations in the Bifrons–Thouarsense (Toarcian), Murchisonae–Bradfordensis (Aalenian) and Humpresianum–Garatiana (Bajocian). The Toarcian section was dominated by regressive elongated river-dominated deltas were due to the fall of the sea level the south to southwest directed delta progradation between the Lower and Upper Toarcian, that was deposited as 40 m of deltaic successions, found in places like Prignitz (east) and Brandenburg (north). Most of the palynomorphs found in the Toarcian stratum are connected with ones found in the Sorthat Formation.
Nearly 40 m thick, the upper section of the formation is composed mostly by a series of cross-bedded, cross-laminated, wave-rippled and bioturbated sand and heteroliths with sporadic syneresis cracks, pyrite nodules, the ichnofossils Planolites isp. and Teichichnus isp. and brackish to marine palynomorphs, mostly dinoflagellates. This upper part has a stratum more characteristic of nearshore environments with abundant lagoons, coastal lakes and fluvial channels, with the clean sand at the top probably representing a marine shoreface. The Korsodde section, 93 m thick, is composed mostly of coarse-grained sands with cross-bedding and parallel lamination, being mostly black due to an abundant organic debris. This section has been interpreted as part of the large local fluvial system, probably as a series of minor fluvial channels that were connected with coastal lakes and lagoons where riparian vegetation was abundant, judging by the presence of megaflora remains and palynomorphs. Small ichnofossil burrows and larger burrows, including Diplocraterion isp., are common, indicating that there was at least one subunit that was the fill of an estuarine channel. The uppermost part of the formation in the Korsodde section consists of fine-grained sands of yellowish to brown color with cross-stratification and parallel lamination, along with sandstones with thin bioturbated and wave-rippled heterolithic beds.
Profile
At Korsodde, the environment includes the following:
| Unit | Lithology | Thickness (metres) | Type of environment | Fossil flora | Fossil fauna |
|---|---|---|---|---|---|
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Unit A |
Yellow, weakly cemented muscovite quartz sandstone, medium- to fine-grained in the lower part, fine-grained in the upper part. Ripple or herringbone lamination is present in most of the beds, along discontinuous mudstone drapes around 0.5 cm thick and mudstone intraclasts. The mudstones show often ferruginization. A single thin horizon occurs at about 85 cm of the section and also a thin erosional surface with mudstones at 1 m. There is a layer of heterolithic deposits with fine-grained ripple mudstones and sandstones at 1.65–1.75 m. |
0.45–2.3 m |
Estuarine channel fill (upper or marginal, less energetic part) |
None recovered |
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Unit B |
Intercalations of muscovite quartz sandstones and dark mudstone drapes, with abundant heteroliths. In the vertical section, the sandstone layers (3 cm thick) are lenticular, with some displaying ripple cross- and herringbone lamination, and the mudstone drapes (0.5 cm thick) have wavy lamination. These last have a few laminae separated by thicker, coarser, mainly silty laminae showing abundant ferruginous cementation. There is a layer over B considered transitional to C. |
2.3–3.41 m |
Upper tidal flat deposits surrounding an estuary |
None recovered |
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Unit C |
Two main layers: a series of 20 cm dark mudstone with horizontal lamination and silt intercalations and a series of dark heteroliths with intercalated mudstones and ripple limestones. |
3.41–3.7 m |
Restricted bay passing into upper tidal flat deposits |
None recovered |
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Unit D |
Yellow ripple cross sandstone with abundant muscovite, alternating with continuous and discontinuous dark mudstone with abundant organic material. There are pyrite concretions in the lower part. |
3.7–4.7 m |
Lower tidal flat within an estuary |
Roots |
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Unit E |
Mostly fine-grained sediments with abundant organic matter. Starts with 55 cm of muddy sandstone, dark at the beginning and light in the upper part. A bed of 5 cm of mudstone overlays the sandstone, followed by various levels of fine-grained sandstones interbedded with dark siltstone–mudstone, pyrite concretions and sandy mudstone. Over this is developed a massive coal layer containing Neocalamites stems where pyrite becomes more common. It is overlaid by mudstone and fine sandstone that turn into a poorly sorted yellow ferruginous layer. The upper part, 85 cm thick, is composed of mudstone with allochthonous Neocalamites stems and lignite clasts. |
4.7–6.9 m |
Lagoonal environment above a coal bed |
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Unit F |
Mostly pale, fine-grained, ripple cross muddy sandstone and normal sandstone, separated by thin, pale sandy mudstones or thin mudstone drapes. Pyrite concretions and lignite clasts occur in the sandstones. There are synaeresis cracks noted at 8.15–8.75 m. |
6.9–9.9 m |
Tidal flat deposits in an estuary |
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Unit G |
A prominent erosional surface at the start, composed of yellow medium- to fine-grained cross-laminated sandstones with muscovite. |
9.9–11.35 m |
Estuarine bar |
None reported |
None reported |
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Unit H |
Pale, fine-grained ripple and herringbone sandstones and mudstones, with intercalations of sandy mudstones and mudstone drapes with intense ferruginization, and some layers of mudstone–sandstone heteroliths |
11.35–14.2 m |
Marginal part of an estuary channel fill |
None reported |
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Unit I, J |
Bioturbated muddy sandstone |
14.2–14.4 m |
Short-lived bay or lagoon |
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Biota
The Sorthat Formation represents one of the most complete floras found in Europe dating to the Pliensbachian–Toarcian boundary, as well as among Jurassic palynological deposits found worldwide.
Environment
Beyond the deposits on the west and south coast of Bornholm, the formation is present in the Stina-1 well, which belongs to the Rønne Graben (a large offshore pull-apart basin that also includes the westernmost fringe of the island of Bornholm), where both the Sorthat and the Bagå Formation are deposited on the hanging wall fault block close to the main eastern bounding fault of this graben along the west coast of the island. This graben was emerged during the deposition of the Sorthat Formation, as proven by the sand and clay with numerous coal horizons from the Stina-1 well. The presence of a high kaolinite content in both coeval marine Danish Basin and local Bornholm, as well the abundant reworked Carboniferous palynomorphs, indicate significant erosion of a Carboniferous regolith, which was almost completely eroded by the Middle Jurassic. This suggests Pliensbachian–Toarcian rivers eroded the Bornholm High, eliminating all of the Carboniferous layers and leaving only older Palaeozoic strata, as proven by the granite of the younger Bagå Formation. Due to a Late Pliensbachian marine regression, deposition of coal-bearing strata in the Sorthat Formation resumed on Bornholm until an Early Toarcian transgression terminated peat formation. The two main deposits of the formation, seen at the Levka-1 well and the lower part of the Korsodde section, were deposited in an environment influenced by the sea, the Levka location being populated by lagoons, lakes, channels and low fluvial areas. Then deposition of the Sorthat Formation in the Latest Pliensbachian–Toarcian demonstrated a rapid subsidence and relative sea level rise of the Rønne Graben, while the adjoining Arnager Block suffered a relative sea level fall. This is because the Rønne Graben experienced a rapid relative sea level rise during the Early Toarcian, coeval with the prominent rise registered in the Danish Basin. This peak transgression of the Ligurian Cycle is found in the coeval layers of the Fjerritslev Formation. The Bifrons to Levesquei zone in the coeval units at the east and west of Prignitz, a sandy coastal-deltaic succession, was replaced by laminated shales with pelagic marine fauna, reflected in the shoreline shifts to the northeast, which contributed to retrogradational stratal pattern architectures. In the Sorthat Formation, a transition occurs from upper to lower shoreface environments, indicating a deepening trend. In the Younger Levesquei subzone, delta plain environments were replaced by shoreface setting with active bioturbation and hummocky cross-stratification. The Rǿnne Graben shows seismic lines with onlapping patterns that have been correlated to these Lower Toarcian marine shoreface deposits with intense bioturbation.
The depositional environments include the following:
- The Levka beds start overlying the foreshore deposits of the Hasle Formation. They are composed mostly of interbedded sand, clay and coal beds. Loose sand constitutes the main parts of the unrecovered intervals. This sand is fine to medium-grained, micaceous, very carbonaceous and muddy, showing mostly parallel lamination, with rare cross-bedding, cross-lamination and flaser lamination. These first levels are interpreted as fluvial channel fills, reflecting active channel deposition followed by decreasing current strength and channel abandonment with a passive phase of clay deposition, final overgrowth and change into peat-forming swamps. Between the channel fills are intervals with thinly interbedded sand and clay and common occurrence of rootlets, coal seams and rapid facies changes, interpreted as representing wet, vegetated, floodplain with shallow lakes, swamps and small crevasse deltas receiving overbank spills from nearby active channels. Coal seam analyses revealed that the peat-forming swamps were water-saturated, densely vegetated, anoxic and nutrient-rich. It was followed by a coastal or lower delta plain environment, populated by abundant large fluvial channels or distributaries, and nearby floodplain areas where lacustrine–lagoonal mud, crevasse splays and peat accumulated. Later a rise in the sea level is signalled by the increase of acritarchs and Tasmanites, where a lagoon succession is overlain by the fill of a coastal lake that developed into a palaeosol. Later, marine palynomorphs became absent and the location became again a crevasse delta and fill of an abandoned fluvial channel, intercalated with lake deposits. After this, a lagoon succession is marked with the appearance of Planolites and Teichichnus burrows and dinoflagellate cysts of Nannoceratopsis gracilis, N. senex and N. triceras and common occurrence of Botryococcus, indicating a major marine rise event.
- The Sorthat beds consist of a series of intercalated minor or major extended lower delta plain environment deposits, with pyrite nodules and the trace fossil Arenicolites.
- The Korsodde section overlies the fine-grained sandstones of the Hasle Formation, deposited on a high-energy shoreface environment. This section of the formation started as a derivative of sand units deposited in fluvial channels, with abundant carbonaceous matter probably derived from extensive erosion of peat accumulations during changes in channel courses, as indicated by the abundant presence of rootlets and coaly beds. The intrusion of younger clay beds led to a gradual infilling of relatively small coastal lakes and enclosed lagoons, which became vegetated and turned into peat-accumulating environments (isolated from active clastic sedimentation), eventually forming palaeosols. This units are filled with pyrite nodules and medium-large wood fragments, while the genera Botryococcus, Lecaniella and Mendicodinium (represented by M. reticulatum) occur in varying amounts ranging from abundant to rare, with a few acritarchs also present. This stratum is overlaid by the intercalation of crevasse delta deposits and lacustrine–brackish flooding surfaces with shifts between ordinate and subordinate tidal currents, with scattered small burrows (Diplocraterion) and mud drapes on foresets containing abundant Nannoceratopsis senex. Mancodinium semitabulatum and Mendicodinium groenlandicum are also found in this sections, but subordinated to the inner fluvial dominated part of an estuarine channel, overlaid by a tidally dominated part. Lagoons in various conditions on younger deposits suggest sea level rise, intercalated with riverine deposits, on a series of regression–transgression trends.
- In the Rønne and Kolobrzeg grabens along the Arnager Block representative offshore layers of the formation appear in the Baltic Sea. In the Rønne Graben this unit is found in a landward direction towards the Arnager Block. The absence of the Sorthat Formation in the Pernille-1 borehole of the Arnager Block could be due to an inversion of the strata, although emersion of this block cannot be ruled out. The whole system is thought to have built a southeast to southwest erosion due to the seaward orientation of the Arnager Block, which tilted towards the northwest. Lagoonal to deltaic systems developed locally, fed by the currents coming from either the Skarup Platform to the west, the Bornholm High to the north and likely the Arnager Block.
Inertinite has been recovered from the coal-bearing levels of the formation, where the palynology shows that the mire vegetation may have been dominated by gymnosperms and also contained ferns characterised by the genera Dicksonia or Coniopteris and the family Osmundaceae. Biomolecules were found in several coal seams there, among which Euulminite and Attrinite were the most abundant huminite macerals recovered. The Levka-1 well section represents fluvial channels, floodplain areas with shallow lakes and lagoons, and small crevasse deltas, with abundant coalified wood fragments and stems, most of them found associated with sandy channel fills and on heavily rooted crevasse and lake deposits in shallow inter-fluvial areas. In the Toarcian at Bornholm, strata indicate a warm, humid climate suggested by the large number of plant species from the interconnected Jameson Land, and thin cutinised leaves of Podozamites and Equisetales comparable in size to modern subtropical bamboos are thought to reflect favourable conditions for plant growth. There is abundant coal, which indicates that wildfires occurred in the bog. Wood particles from this section, both charcoalified and unburned (coalified), with many particles being rounded and worn, imply the influence of greater transportation energies.
Coal
On Korsodde, the Lower Toarcian section records higher temperatures and decreased rainfall and humidity, which led to an increase of the potential for local wildfires, reflected in the increased abundance of charcoal and burnt plants. In the section at Korsodde that includes the Toarcian oceanic anoxic event, thermophilic plant taxa imply that the climate was relatively dry, and presence of micro- and macroscopic charcoal indicates a spike of abundance and increase of the wildfire activity.
Most of the coal seams recovered from the formation come from Levka 1 and the Korsodde section, and are derived in most cases from a densely vegetated, anoxic swamp, which was probably rheotrophic and rich in nutrients. Study of the peat accumulation indicates that it occurred in rather short time intervals (around 2,300 years) and in a warm temperate to subtropical climate, falling short of the rate seen in tropical accumulations, such as the 1.8 mm/yr on the Batang Hari River in Sumatra. Peat accumulation of 1 mm/yr is equal to that of modern Central Kalimantan coastal settings. The deposits have great amounts of thin and clean coal seams, covered by lacustrine–lagoonal flooding peaks, indicating rapid changes in the environment that were controlled by fairly rapid subsidence of the Rønne Graben, which along with eustatic rise in sea level caused decreases and increases in the base level at the coastal plain. The majority of the samples were immature, low-rank coals with generally very high content of humified organic matter, which indicates prevailing anoxic and fully saturated conditions during peat formation, with occasional inundations by freshwater that favoured humification of the plant tissues and also may have increased the gelification processes, raising the pH. Hopanoids are abundant and an indicator of common bacterial activity. The vegetation — both the nearby plants and those of the peat swamp — was probably small in stature, and its diversity suggests a humid, warm-temperate to subtropical climate that favoured prolific vegetation.
- The Levka-1 well has a core of approx. 150 m through the Sorthat Formation, covering the underlying marine strata of the Hasle Formation. The lower part includes 112 m of coal along with sand and clay. There is abundant large, coalified wood fragments and stems. The coal-bearing strata of the Levka-1 are interpreted as fluvial channel fills, with active channel deposition followed by abandonment and a passive phase of clay deposition, gradual overgrowth and change into a peat-forming environment. clay and coal seams present in this stratum have abundant rootlets and a non-marine palynomorph assemblage dominated by spores and pollen, interpreted as representing flood plain areas with shallow lakes, small crevasse deltas and swamps. Some sections have wave ripples, wavy and flaser bedding, bioturbation and transported Equisetites stems that are interpreted as the sediment fill of a local lagoon, deposited on a transgressive shoreline with a series of lagoon successions. Levka-1 coal contains hard, black coal and is very similar petrographically, with huminite in most of the seams, some seams being up to 90% huminite. There is a dominance of macerals from detrital organic matter (humodetrinite) over macerals derived from more woody material (humotelinite). Gelinite appears as the most common component of the samples, followed by huminite.
- The Korsodde section is interpreted as representing a small coastal series of lakes and protected lagoons, where at least six coal seams have been found. It represents a wet, anoxic, and probably rheotrophic, nutrient-rich peat-forming environment. Above the marine strata of the Toarcian transgression lie strata with abundant clay, fine-grained sand, and silt that contains transported, coalified pieces of wood, pyrite nodules, rootlets and a diverse microspore assemblage, in which the marine dinoflagellate Mendicodinium reticulatum is abundant. In these coal seams, the huminite maceral group comprises the majority of the organic matter, with humotelinite dominating over humodetrinite maceral. Eu-ulminite and densinite are the most prominent macerals.
Fungi
Color key
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Notes Uncertain or tentative taxa are in small text; |
| Genus | Species | Stratigraphic position | Abundance | Material | Notes | Images |
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Abundant but limited to the upper layers |
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Fungal spores of uncertain classification. The three uppermost samples of the Korssode section are poor in diversity, but fungal spores are common in at least one sample; these have not been recorded from the samples below. Fungal spores represent various morphotypes: amerospores (unicellular, aseptate, sphaerical or sack-shaped spores of variable size), phragmospores (with transverse septa) and dictyospores (multicellular spores) were recovered from the sister Mechowo borehole in the Ciechocinek Formation (Kaszuby Land). |
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Phytoplankton
In the Lower Jurassic of Bornholm there were several successions of nearshore peat formations with dinoflagellates. Coal-bearing strata were deposited in an overall coastal plain environment during the Hettangian–Sinemurian, and then during the Early Pliensbachian deposition was interrupted until the late Pliensbachian–Lowermost Toarcian due to a sea regression.
| Genus | Species | Stratigraphic position | Abundance | Material | Notes | Images |
|---|---|---|---|---|---|---|
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Very rare and limited to the middle layers |
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An algal acritarch, probably related to freshwater red algae, similar to extant Florideophyceae (for example, Hildenbrandia) or Batrachospermales (Batrachospermum) and Thoreales. |
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Abundant to very abundant towards the upper sections |
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Type genus of the Botryococcaceae in the Trebouxiales. A colonial green microalga of freshwater and brackish ponds and lakes around the world, where it often can be found in large floating masses. Sorthat Formation Botryococcus lived in an environment interpreted as a coastal lake, permanently vegetated and shallow, that was occasionally flooded by the sea. |
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Very rare and limited to the lower layers |
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Affinities with the family Zygnemataceae. A genus derived from freshwater filamentous or unicellular, uniseriate (unbranched) green algae. |
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Very rare and limited to middle section |
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Affinities with the family Pycnococcaceae. |
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Very rare with peak in middle-upper layers in Levka-1 borehole; Very rare and limited to the lowermost layers in Sorthat beds |
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Affinities with the family Pterospermopsidaceae. |
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Common |
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A foraminifer, member of the family Lituoloidea in the Lituolida. |
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Very rare and only present in the middle section |
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A dinoflagellate, member of the Cribroperidinioideae. |
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Rare to Abundant but limited to the lower-middle section |
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Affinities with the family Zygnemataceae. |
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Very abundant either on the lower middle or upper sections, very rare or absent in all other layers |
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Affinities with the family Prasinophyceae. |
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Abundant but only present in the middle section |
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A dinoflagellate, member of the Luehndeoideae. It establishes the Luehndea spinosa zone; the age of this zone is late Pliensbachian to early Toarcian. |
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Very rare and only present in the middle section |
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A dinoflagellate, type genus of the Mancodinioideae. |
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Rare to Abundant but limited to the lower-middle section |
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A dinoflagellate, member of the family Gonyaulacales. |
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Abundant but limited to the middle section |
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An acritarch, familia incertae sedis |
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Abudant in the lower section in Levka-1; Very abundant in the middle-upper sections in Sorthat beds and Korsodde |
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A dinoflagellate, member of the family Nannoceratopsiaceae. It is characteristic of marine deposits. The presence of N. gracilis, N. senex and N. triceras, and common occurrence of Botryococcus is interpreted as indicating a lagoon succession overlying a transgressive surface and signals a rise in relative sea level. |
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Very rare with peaks in the middle layers |
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Affinities with the family Zygnemataceae. A genus derived from freshwater filamentous or unicellular, uniseriate (unbranched) green algae. |
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Very rare and limited to middle section |
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Affinities with the family Pterospermataceae. |
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Abundant to very abundant but limited to the lower section |
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An algal palynomorph unique to the setting and probably related to freshwater red algae; similar to extant Batrachospermales. |
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Rare |
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A foraminifer, type genus of the Spirillinidae in the Spirillinida. |
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Very rare to abundant in the upper sections |
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Brown algae, type genus of the family Striatellaceae in the Striatellales. These brown algae diatoms are associated with either brackish or marginal marine environments. |
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Abudant to very rare, limited to the middle layers |
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Affinities with the family Pyramimonadaceae. Found on shoreface and shoreface–offshore transition zone deposits. |
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Abundant but limited to the lowermost layer in Levka-1 borehole; Abudant to rare in Sorthat beds & Korsodde |
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Affinities with the family Zygnemataceae. |
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Very rare and limited to the lower layers |
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A dinoflagellate, member of the Dinophyceae. |
In Early Toarcian carbonates, local bulk organic matter and wood fragments have been associated with carbon cycle perturbations, shedding light on the reaction of the continental biota to the Toarcian oceanic anoxic event, which accompanied large-scale volcanism. There are several changes to the woody vegetation in the wood-derived carbon, with pollen assemblages dominated by pollen types in the Sciadopityaceae and Miroviaceae, such Cerebropollenites associated with cycad pollen types (Chasmatosporites) and the hirmeriellaceous Corollina. The local palynology has shown the terrestrial changes of the local flora. In the Pliensbachian the dominant palynofacies were ones in the Cupressaceae such as Perinopollenites, along with cycads such as Cycadopites, found in mid-latitude Mediterranean climates. Then, at the start of the event the local pollen assemblages show a shift to spore-rich layers, showing a long-term increase in ferns and lycophytes, an indicator of more humid conditions. Finally, after the Toarcian anoxic event, the Sorthat Formation showed an abrupt rise of pollen of Hirmeriellaceae such as Corollina and specially Spheripollenites, both indicators of semidesertic to dry Mediterranean climates, implying an abrupt warming event coeval with the changes happening at sea. The main deposits of macroflora are the Hasle clay pit and the Korsodde section. The flora was originally stated to be coeval with the Rhaetian–Hettangian floras of Sweden, but found later to be Pliensbachian–Toarcian. Möller did the two major studies on the local flora, with 68 species described, 50% of them ferns. The Late Pliensbachian section is dominated by ferns, suggesting a warm and humid climate, which fits with the palaeolatitude of Bornholm, firmly within the Jurassic warm biome. But the presence of Ginkoaleans and absence of large-leafed Bennettites suggest this warm climate was seasonal. Ferns and sphenophytes in the assemblage are interpreted to have occupied the forest floor. Bennettites were mid-storey shrubs, and conifers, such as Pagiophyllum, together with ginkgoaleans, make up the main arboreal flora. All the flora developed on a meandering river system with well-vegetated marshy flood plains. The Toarcian section shows a radical change on the local flora, as Hirmeriellaceae conifers take over the role of dominant flora, representing 95% of the pollen recovered, along with the rise of seed ferns, Bennettites and Czekanowskiales. The dominance of Pagiophyllum and its related pollen Corollina torosus indicate high temperature and aridity with seasonal wildfires (though some sections show a low coal ratio and are derived from slightly more humid environments), with rare occurrences of Brachyphyllum and one Cyparissidium. Is also common to found wood from the nearshore deposits of Korsodde, with two sets: macroscopic wood, recognizable to the naked eye, up to branch-sized; and microscopic wood (0.25 to 1 mm average dimension).
Bryophyta
| Genus | Species | Stratigraphic position | Abundance | Material | Notes | Images |
|---|---|---|---|---|---|---|
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Very rare and present in certain intervals |
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Incertae sedis; affinities with Bryophyta. This spore is found in Jurassic sediments associated with the polar regions. The Sorthat Formation is among its southernmost locations. |
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Very rare and only in a few layers, with a few layers of very abundant presence in the middle |
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Affinities with the family Notothyladaceae in the Anthocerotopsida. Hornwort spores. |
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Very rare and only in the middle layers |
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Affinities with the family Notothyladaceae in the Anthocerotopsida. Hornwort spores. |
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Abudant in the lowermost layer to very rare or absent in the upper ones |
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Affinities with the family Sphagnaceae in the Sphagnopsida. |
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Very rare and only in a few layers of very abundant presence in the uppermost section |
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Affinities with the family Encalyptaceae in the Bryopsida. Branching moss spores, indicating high water-depleting environments. |
_2281.JPG) | |
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Very rare with an abundant peak in the middle in Levka-1; very rare and limited to lower layers in Sorthat beds and Korsodde |
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Affinities with the family Sphagnaceae in the Sphagnopsida. "Peat moss" spores, related to genera such as Sphagnum that can store large amounts of water. |
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Very rare and only in a few layers, with a few layers of very abundant presence in the middle |
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Affinities with the family Sphagnaceae in the Sphagnopsida. |
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Very rare in the lower layers and absent in the youngest layers, with peak moderately abundant in the middle in Levka-1; very rare and limited to lower middle and uppermost layers in Sorthat beds and Korsodde |
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Affinities with the family Sphagnaceae in the Sphagnopsida. |
Lycophyta
| Genus | Species | Stratigraphic position | Abundance | Material | Notes | Images |
|---|---|---|---|---|---|---|
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Peak in the upper middle, very abundant to very rare in the lowermost and uppermost layers in Levka-1; absent to abundant in upper layers in Korsodde |
Spores |
Affinities with the Selaginellaceae in the Lycopsida. Herbaceous lycophyte flora, similar to ferns, found in humid settings. This family of spores are also the most diverse in the formation. |
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Abundant only in the middle upper section; absent in all other levels |
Spores |
Affinities with the Selaginellaceae in the Lycopsida. |
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Very rare |
Spores |
Affinities with the family Lycopodiaceae in the Lycopodiopsida. |
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Very rare and only in a few layers, with an exceptional peak in the middle upper section |
Spores |
Affinities with the Selaginellaceae in the Lycopsida. |
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Very rare and only in the middle layers |
Spores |
Affinities with the Selaginellaceae in the Lycopsida. |
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Very rare in the lower layers to moderately abundant in the upper |
Spores |
Affinities with the family Lycopodiaceae in the Lycopodiopsida. |
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Limited to a few specimens |
Fine stems |
Affinities with Selaginellaceae and Lycopodiidae in the Lycopodiales. It was originally described as Lycopodites falcatus. The leaves of this species are more prominently anisophyllous than in the Raheto-Hettangian S. coburgensis from Franconia. |
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Very rare and limited to the lowermost layer |
Spores |
Affinities with the family Lycopodiaceae in the Lycopodiopsida. Lycopod spores, related to herbaceous to arbustive flora common in humid environments. |
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Very rare and in a few samples in Levka-1; abundant but only in the lowermost layer in Sorthat beds; very rare in Korsodde section |
Spores |
Affinities with the Selaginellaceae in the Lycopsida. |
Equisetales
| Genus | Species | Stratigraphic position | Abundance | Material | Notes | Images |
|---|---|---|---|---|---|---|
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Abudant in the upper section, rare to not present in the underliying layers in Levka-1; very rare and only in the middle in Sorthat beds; abundant to very abundant in the middle Korsodde section |
Spores |
Affinities with the Calamitaceae in the Equisetales. Horsetails are herbaceous flora found in humid environments and are flooding-tolerant. In the sections of the formation such as Korsodde, this genus has small peaks in abundance in the layers where more Equisetites stems are found. |
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Extremely Common |
Stems |
Affinities with Equisetaceae in the Equisetales. Related equisetalean stems are found in the Hettangian strata along Skane, Sweden. In the lagoonar sections there is correlation between bioturbation and transported Equisetites stems. Local Equisetales reached a considerable size, comparable to modern subtropical bamboos, close to lakes and in the wettest environments. |
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Rare |
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Affinities with Calamitaceae in the Equisetales. Related equisetalean stems are found in strata of the same age along Skane, Sweden. Based on analogies with morphologically similar extant Equisetum species, it is interpreted to represent a plant of consistently moist habitats, such as marshes, lake margins or forest understorey, normally developing dense thickets. |
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Rare |
Leaf whorls |
Affinities with Equisetidae in the Equisetales. |
Pteridophyta
| Genus | Species | Stratigraphic position | Abundance | Material | Notes | Images |
|---|---|---|---|---|---|---|
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Very rare and only in the lower layers |
Spores |
Affinities with the genus Saccoloma, type representative of the family Saccolomataceae. This fern spore resembles those of the living genus Saccoloma, being probably from a pantropical genus found in wet, shaded forest areas. |
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|
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Moderately abundant |
Spores |
Affinities with the family Osmundaceae in the Polypodiopsida. Near fluvial current ferns, related to the modern Osmunda regalis. |
_-_Cape_St._Mary%27s_Ecological_Reserve,_Newfoundland_2019-08-10.jpg) | |
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Abudant |
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Affinities with Osmundaceae in the Osmundales. Related to species commonly reported from the Triassic–Jurassic of southern Sweden. |
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Rare |
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Affinities with Osmundaceae in the Osmundales. Specimens assigned to this morphothype have been found in the Middle Jurassic flora of Yorkshire, associated with Todites miospores, and were originally described as Asplenites cladophleboides. |
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Very rare and only in a few upper layers |
Spores |
Affinities with the family Cyatheaceae in the Cyatheales. Arboreal fern spores. |
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Abudant |
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Affinities with Dipteridaceae in the Polypodiales. |
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Moderately to abudant in the middle layers in Levka-1; very rare and only in middle to upper layers in Sorthat beds and Korsodde |
Spores |
Incertae sedis; affinities with the Pteridophyta |
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Rare |
Incomplete frond fragment |
Affinities with Polypodiales in the Polypodiidae. Common cosmopolitan Mesozoic fern genus. Recent research has reinterpreted it a stem group of the Polypodiales (closely related to the extant genera Dennstaedtia, Lindsaea, and Odontosoria). |
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Abudant throughout the interval in Levka-1; moderately common under to abundant in the upper Sorthat beds; rare or not present in lower to moderlately common in upper Korsodde |
Spores |
Incertae sedis; affinities with the Pteridophyta |
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Rare |
Leaflets |
Affinities with Dicksoniaceae in the Cyatheales. It show similarities with Sphenopteris longipinnata in the morphological outline of the leaflets and the keels of the pinnate axis. |
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Abudant |
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Affinities with Dipteridaceae in the Polypodiales. Dictyophyllum is a common dipteridacean genus of the mid-Mesozoic. |
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Dominant |
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Affinities with Dicksoniaceae in the Cyatheales. The Lund material is dominated by ferns belonging to the genus Eboracia (28 specimens of E. lobifolia and 14 of another Eboracia sp.). The latter has smaller pinnules than E. lobifolia. |
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Very rare and in a few samples |
Spores |
Affinities with the Gleicheniales in the Polypodiopsida. Fern spores from low herbaceous flora. |
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Very rare |
Isolated pinnae |
Affinities with Matoniaceae in the Gleicheniales. |
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Abudant |
Isolated pinnae |
Affinities with Dipteridaceae in the Polypodiales. Specimens from the same species have been found in the Hettangian Höör Sandstone at southern Sweden. |
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Very rare and only in a few upper layers |
Spores |
Incertae sedis; affinities with the Pteridophyta |
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Very rare and only in a few layers with a few layers of very abundant presence in the middle |
Spores |
Affinities with the Gleicheniales in the Polypodiopsida. Fern spores from low herbaceous flora. |
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Very rare and only in a few layers |
Spores |
Incertae sedis; affinities with the Pteridophyta |
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Very rare and only in a few layers |
Spores |
Affinities with the family Lygodiaceae in the Polypodiopsida. Climbing fern spores. |
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Rare and in concrete samples in Korsodde; very rare and only in the middle in Levka-1 |
Spores |
Incertae sedis; affinities with the Pteridophyta |
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Very rare and only in a few layers |
Spores |
Affinities with the family Dennstaedtiaceae in the Polypodiales. Forest fern spores. |
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Very rare and in concrete samples in Levka-1 & Sorthat beds; abundant but limited to lower layers in Korsodde |
Spores |
Affinities with the Ophioglossaceae in the Filicales. Fern spores from lower herbaceous flora. |
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Abundant in the lower middle section, very rare in upper Levka-1; very rare and only in the middle in Sorthat beds |
Spores |
Affinities with the Pteridaceae in the Polypodiopsida. Forest ferns from humid ground locations. |
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Very rare |
Isolated pinnae |
Affinities with Marattiaceae in the Marattiopsida. |
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Very rare and in the lower layers only in Levka-1; very rare but also in upper layers in Sorthat beds and Korsodde |
Spores |
Affinities with the Marattiaceae in the Polypodiopsida. Fern spores from low herbaceous flora. |
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Abundant |
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Affinities with Matoniaceae in the Gleicheniales. |
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Very rare and only in a few layers |
Spores |
Incertae sedis; affinities with the Pteridophyta |
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Rare |
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Incertae ordinis in the Pteridophyta. Spiropteris is the name given to the fossil of a coiled, unopened fern leaf. |
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Very rare and only in a few uppermost layers |
Spores |
Incertae sedis; affinities with the Pteridophyta |
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Very rare |
Isolated pinnae |
Affinities with Dipteridaceae in the Polypodiales. |
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|
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Very rare and only in the middle layers in Levka-1; very rare and only in the uppermost section in Sorthat beds |
Spores |
Affinities with the family Osmundaceae in the Polypodiopsida. |
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Very rare down to moderately abundant in Levka-1; very rare and only in upper layers in Sorthat beds and Korsodde |
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Affinities with the genus Dicksoniaceae in the Polypodiopsida. Tree fern spores. |
_C.Chr._by_Jason_Hollinger_001.jpg) | |
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Very rare and limited to the middle |
Spores |
Incertae sedis; affinities with the Pteridophyta |
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Only in the uppermost layers and very rare |
Spores |
Affinities with the Callistophytaceae in the Callistophytales. Spores from large arboreal to arbustive ferns. |
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Very rare and only in the lowermost layers |
Spores |
Affinities with the family Cyatheaceae in the Cyatheales. Arboreal fern spores. |
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Peltaspermales
| Genus | Species | Stratigraphic position | Abundance | Material | Notes | Images |
|---|---|---|---|---|---|---|
|
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Very rare and only in the lower to middle layers in Levka-1; abundant to very abundant in Sorthat beds and Korsodde |
Pollen |
Affinities with the families Peltaspermaceae, Corystospermaceae or Umkomasiaceae in the Peltaspermales. Pollen of uncertain provenance that can be derived from any of the members of the Peltaspermales. The lack of distinctive characters and poor conservation make this pollen difficult to classify. Arboreal to arbustive seed ferns. |
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Common |
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Plant propagules that may be from Pteridospermatophyta, Vladimariales, Bennettitales or Pinales. Fruits or seeds of uncertain placement. |
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Very rare |
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Affinities with Umkomasiaceae in the Pteridospermatophyta. |
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Very rare |
Isolated pinnae |
Affinities with Corystospermaceae in the Pteridospermatophyta. |
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Very rare |
Leaf compressions |
Affinities with Umaltolepidaceae in the Vladimariales. These belong to a group parallel to Gingkoaceans and derived probably from Umkomasiaceae. |
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Very rare and in concrete layers |
Pollen |
Affinities with the families Peltaspermaceae, Corystospermaceae or Umkomasiaceae in the Peltaspermales. |
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Very rare |
Isolated pinnae |
Affinities with Umkomasiaceae in the Pteridospermatophyta. |
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Very rare |
Isolated pinnae |
Affinities with Umkomasiaceae in the Pteridospermatophyta. Less common than other arboreal plants. |
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Common |
Isolated pinnae |
Affinities with Umkomasiaceae in the Pteridospermatophyta. |
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Very rare |
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Affinities with Pteridospermae in the Pteridospermatophyta. |
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Common |
Isolated pinnae |
Affinities with Caytoniaceae in the Pteridospermatophyta. Related to seed ferns present in the Rhaetic flora of Sweden. |
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Very rare and only in the lower layers |
Pollen |
From the family Caytoniaceae in the Caytoniales. Caytoniaceae are a complex group of Mesozoic fossil floras that may be related to both Peltaspermales and Ginkgoaceae. |
Erdtmanithecales
| Genus | Species | Stratigraphic position | Abundance | Material | Notes | Images |
|---|---|---|---|---|---|---|
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Abudant but limited to lower layers |
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Type pollen of the Erdtmanithecales, related to the Gnetales. Thick tectum, infratectum of small granules, indistinct or absent foot layer. Originally thought to come from angiosperms, then suggested to come from arbustive Bennettites. It was recently found to come from Eucommiitheca, a member of the enigmatic Erdtmanithecales, reinterpreted as an unusual gymnosperm grain with a single distal colpus flanked by two subsidiary lateral colps. Is very similar to the pollen of the extant Ephedra and Welwitschia (mainly on the basis of the granular structure of the exine). |
Cycadophyta
| Genus | Species | Stratigraphic position | Abundance | Material | Notes | Images |
|---|---|---|---|---|---|---|
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Rare |
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Affinities with Cycadales in the Cycadopsida. Originally described as Podozamites ensiformis. |
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Abundant lower to very abundant upper |
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Affinities with the family Zamiaceae in the Cycadales. It is among the most abundant flora recovered on the upper section of the coeval Rya Formation, and was found to be similar to the pollen of the extant Encephalartos laevifolius. |
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Abudant but limited to lower layers in Levka-1; abundant to very abundant in Sorthat beds and Korsodde |
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Affinities with the family Cycadaceae in the Cycadales. The structure of the exine of Clavatipollenites hughesii from Jurassic deposits is fundamentally different from that of Cretaceous grains referred to the same species, confirming observations made previously on the basis of analysis under the light microscope and suggesting a possible derivation from cycadalean rather than angiospermous plants. |
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Rare |
Leaflets |
Affinities with Cycadales in the Cycadopsida. |
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Rare |
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Affinities with Cycadidae in the Cycadopsida. |
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Bennettitales
| Genus | Species | Stratigraphic position | Abundance | Material | Notes | Images |
|---|---|---|---|---|---|---|
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Very abundant but present only in the uppermost sections |
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Affinities with the family Cycadaceae and Bennettitaceae. It has been found associated with the Bennetite pollen cone Bennettistemon. It increases towards the Toarcian section. |
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Rare |
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Affinities with Williamsoniaceae in the Bennettitales. |
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Very abundant |
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Affinities with Cycadeoidaceae in the Bennettitales. The most common and abundant bennetite on the formation. |
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Very abundant |
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Affinities with Cycadeoidaceae in the Bennettitales. |
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Dominant |
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Affinities with Williamsoniaceae in the Bennettitales. Insufficient and incomplete material prevents certain assignment of Otozamites cf. reglei and Otozamites cf. mimetes |
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Very abundant |
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Affinities with Williamsoniaceae in the Bennettitales. |
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Rare |
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Affinities with Williamsoniaceae in the Bennettitales. |
_from_Whitby,_Estuarine_Series,_Middle_Jurassic_(L.8044)_@mcrmuseum_-NaturesLibrary_(21548076115).jpg) |
Ginkgoales
| Genus | Species | Stratigraphic position | Abundance | Material | Notes | Images |
|---|---|---|---|---|---|---|
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Common |
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Affinities with Karkeniaceae in the Ginkgoales. Unlike other plant specimens from the location, it is more characteristic of Middle Jurassic flora. |
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Common |
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Affinities with Czekanowskiales in the Ginkgoales. This genus is related to flora from the Rhaetian–Hettangian boundary of Jameson Land, but also present in Romania. |
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Rare |
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Affinities with Czekanowskiales in the Ginkgoales. Linked to the Lower Liassic flora of Greenland. |
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Common |
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Affinities with Ginkgoaceae in the Ginkgoales. Seven species assigned to either Ginkgo or Ginkgoites have been reported from Latest Triassic to middle Jurassic strata of southern Sweden. |
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Rare |
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Affinities with Ginkgoales in the Ginkgoopsida. |
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Abundant but limited to the middle layers |
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Affinities with the family Karkeniaceae and Ginkgoaceae in the Ginkgoales. Had been considered pollen of Chloranthaceae but is likely from Ginkgoales, which can have similar features |
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Rare |
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Affinities with Czekanowskiales in the Ginkgoales. This species was described on the basis of individuals collected in Greenland from the Triassic–Jurassic boundary. |
Coniferophyta
| Genus | Species | Stratigraphic position | Abundance | Material | Notes | Images |
|---|---|---|---|---|---|---|
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Abundant |
Affinities with Hirmeriellaceae or Araucariaceae in the Pinales. Originally Araucarioxylon württembergica. This genus is usually associated with leaf-bearing twigs referred to as Pagiophyllum, abundant in the Sorthat Formation. |
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Very rare and only in upper layers |
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Affinities with Araucariaceae in the Pinales. |
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Rare |
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Affinities with Taxaceae in the Pinales. Was first identified in Bornholm. Is similar to the cretaceous Taxus huolingolensis and extant Taxus in leaf gross morphology and has papillate abaxial cuticles, probably being close to this genus. |
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Abundant |
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Affinities with Araucariaceae or Hirmeriellaceae in the Pinales. Is related to the Hettangian axis found in Scania, Sweden |
_(cropped).jpg) | |
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Very rare and only in a few layers |
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Affinities with the family Araucariaceae in the Pinales. Conifer pollen from medium to large arboreal plants. |
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Abundant to very abundant |
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Affinities with both Sciadopityaceae and Miroviaceae in the Pinopsida. This pollen's resemblance to extant Sciadopitys suggest that Miroviaceae may be an extinct lineage of Sciadopityaceae-like plants. |
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Very abundant |
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Affinities with Coniferales in the Coniferopsida. |
_06.jpg) | |
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Very abundant, but with intercalations of layers of total absence in Levka-1; very abundant and almost dominant in some samples in Sorthat beds and Korsodde |
Pollen |
Affinities with the Hirmeriellaceae in the Pinopsida. |
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Very Rare |
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Affinities with Cupressoideae in the Cupressales. It matches with the Middle Jurassic Cyparissidium blackii from Yorkshire, England. |
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Dominant, up to 95% |
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Affinities with Hirmeriellaceae in the Pinales. It is related to other representatives of the genus of the Toarcian of Italy and Lower Jurassic of Israel. Spheripollenites co-occurs with cuticles of Dactylethrophyllum ramonensis, and the species S. psilatus may be produced by the conifer genus Dactylethrophyllum. |
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Rare |
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Affinities with Thujaceae in the Cupressales. It was originally described as Taxites? subzamioides, later merged with Elatocladus. |
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Very rare and limited to upper layers |
Pollen |
Affinities with the family Cupressaceae in the Pinopsida. Pollen that resembles that of extant genera such as the genus Actinostrobus and Austrocedrus, probably derived from dry environments. |
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Rare |
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Affinities with Hirmeriellaceae in the Pinales. The main genus of the Hirmeriellaceae, found in dry environments and probably fire tolerant. |
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Rare to very rare and limited to the lower middle and uppermost layers in Levka-1; peak of abundance in middle layers in Sorthat beds and Korsodde |
Pollen |
Affinities originally suggested with the family Podocarpaceae in the Pinopsida. Quadraeculina is not comparable to pollen of any modern gymnosperm family. |
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Rare |
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Affinities with Krassiloviaceae in the Voltziales. |
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Rare |
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Affinities with Taxaceae in the Pinales. Originally described as Taxus jurassica. |
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Very abundant |
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Affinities with Araucariaceae or Hirmeriellaceae in the Pinales. P. kurrii (originally P. steenstrupi) is preferred as this species is characterised by relatively broad leaves inserted at high angles to the stem. P. peregrinum has been found on the Hettangian Rønne Formation associated with hirmeriellidaceous wood of Simplicioxylon. On the Toarcian levels, is the most common plant cuticle recovered locally. |
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Very rare and limited to the middle layers |
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Affinities with the family Pinaceae in the Pinopsida. Conifer pollen from medium to large arboreal plants. |
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Rare |
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Affinities with Palissyaceae in the Palissyales. Descriptions of Palissya come mostly from coeval deposits in the Northern Hemisphere, based on a very few specimens from Sweden, Germany and America. |
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Intercalations of very abudant presence in some layers with others of total absence in Levka-1; very abudant in all layers in Sorthat beds and Korsodde |
Pollen |
Affinities with the family Cupressaceae in the Pinopsida. |
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Abundant to very abundant with intercalations of absence |
Pollen |
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Rare |
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Affinities with Schizolepisaceae in the Pinaceae. This genus is found associated with Schizolepis on many places, making diverse authors to put both on Pinaceae. |
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Rare |
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Affinities with Schizolepisaceae in the Pinaceae. |
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Abundant |
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Affinities with Krassiloviaceae in the Voltziales. The local Podozamites show a great range of growth, reflecting tropical to subtropical conditions. |
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Rare |
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Affinities with Schizolepisaceae in the Pinaceae. Placed in the Pinaceae on the basis of separated scales and bract scales. |
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Rare |
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Affinities with Cunninghamioideae in the Cupressales. Cunninghamia-like conifers belonging to half-evergreen trees. |
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Abundant |
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Affinities with Hirmeriellaceae in the Pinales. Originally identified as Brachyoxylon rotnaensis, now thought to be a synonym of Simplicioxylon. Wood from these conifers is also found in the Hettangian–Sinemurian Rønne Formation and the Toarcian Úrkút Manganese Ore Formation. |
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Very rare in lower layers to dominant (95% of total) in upper ones |
Pollen |
Affinities with the Hirmeriellaceae in the Pinopsida. Spheripollenites psilatus composes up to 95% of the Lower Toarcian section and is correlated with Toarcian carbon cycle anomalies including the oceanic anoxic event, suggesting dry climates. |
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Very rare |
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Affinities with Palissyaceae in the Palissyales. |
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Rare |
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Affinities with Taxaceae in the Pinales. Known only from Bornholm and belongs to an extant genus. This species is related to the Middle Jurassic floras of Yorkshire. |
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Amber
| Type | Location | Material | Notes |
|---|---|---|---|
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Sorthat beds |
Amber fragments |
B. Eske Koch corroborated the presence of amber drops in the Sorthat Formation. This record represents one of the few worldwide from Jurassic layers. This amber was quoted as derived from Coniferales indet. |
Ichnofossils
| Genus | Species | Location | Material | Type | Origin | Notes | Images |
|---|---|---|---|---|---|---|---|
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Dwelling traces |
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Marine, brackish or freshwater unbranched U-shaped burrows having a subvertical orientation, with or without lining and passive fill. Are common on modern coastal environments. |
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Tubular traces |
Agrichnia |
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Burrow-like ichnofossils. Exclusive to the Sorthat Formation, Bornichnus differs from Palaeophycus Hall in its tangled, contorted morphology and abundant branching. Small open burrows produced probably by farming worm-like animals (probably Polychaeta). Similar complicated burrow systems are produced by the polychaete Capitomastus cf. aciculatus. |
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Tubular fodinichnia |
Fodinichnia |
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Burrow-like ichnofossils. Interpreted as the feeding burrow of a sediment-ingesting animal. A more recent study has found that Scoloplos armiger and Heteromastus filiformis, occurring in the German Wadden Sea in the lower parts of tidal flats, make burrows that are homonymous with numerous trace fossils of the ichnogenus. |
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Burrowing and track ichnofossils |
Domichnia |
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Burrow-like ichnofossils, found only in the uppermost part of the section; probably represents Polychaeta burrows. |
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U-shaped burrows |
Domichnia |
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Burrow-like ichnofossils. Most show only protrusive spreit, like the local ones, produced under predominantly erosive conditions where the organism was constantly burrowing deeper into the substrate as sediment was eroded from the top. Most Diplocraterion show only protrusive spreiten, like the local ones produced under predominantly erosive conditions where the organism was constantly burrowing deeper into the substrate as sediment was eroded from the top. |
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Cylindrical, predominantly horizontal to inclined burrows |
Domichnia |
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Burrow-like ichnofossils. They occur in different size classes, 3, 5 and 10 mm in diameter. |
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Cylindrical burrows |
Pascichnia |
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Burrow-like ichnofossils referred to vermiform deposit-feeders. Sometimes considered a junior synonym of Palaeophycus. |
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Trace fossil |
Sequestrichnia |
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Burrow-like ichnofossils. Vertical or oblique complex trace fossil composed of a bunch of spindle-shaped structures and associated tubes, typical of a restricted environment (?estuarine/lagoonal). The local Rosselia is similar to the ichnogenus Parahentzschelinia surlyki from the lower Jurassic of Greenland, which may be a junior synonym. This trace fossil is interpreted as made by a small deposit-feeding animal, living in a tube communicating with the sea floor. These traces are linked with shrimps or other aquatic arthropods, since the tunnels possess scratch patterns. |
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Cylindrical to subcylindrical burrows |
Domichnia |
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Burrow-like ichnofossils made by organisms advancing along the bottom surface. Very narrow, vertical or subvertical, slightly winding unlined shafts filled with mud. Interpreted as dwelling structures of vermiform animals; specifically, the domichnion of a suspension-feeding worm or phoronidan, with certain Skolithos representing entrance shafts to more complicated burrows. |
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Dwelling traces |
Fodinichnia |
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Burrow-like ichnofossils. The level where this ichnogenus is more abundant is also composed of abundant fragments of spreite lamination, derived from the intersection with the ichnofossil. They are believed to be fodinichnia, with the organism adopting the habit of retracing the same route through varying heights of the sediment, which would allow it to avoid going over the same area. Believed to derive from annelid worms. |
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Tubular fodinichnia |
Fodinichnia |
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Burrow-like ichnofossils. Large burrow-systems consisting of smooth-walled, essentially cylindrical components. Found in association with Teichichnus. |
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See also
- List of fossiliferous stratigraphic units in Denmark
- Neringa Formation, Lithuania
- Pliensbachian formations
- Blanowice Formation, Southern Poland
- Clarens Formation, South Africa
- Mizur Formation, North Caucasus
- Fernie Formation, Canada
- Hasle Formation, Denmark
- Kota Formation, India
- Los Molles Formation, Argentina
- Mawson Formation, Antarctica
- Rotzo Formation, Italy
- Whiteaves Formation, British Columbia
- Navajo Sandstone, Utah
- Kandreho Formation, Madagascar
- Kota Formation, India
- Cattamarra Coal Measures, Australia
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