Middle Cambrian Research Articles

Revision of the Order Paterinida (Brachiopoda) from the Lower and Middle Cambrian of the Siberian Platform

Revision of the Order Paterinida (Brachiopoda) from the Lower and Middle Cambrian of the Siberian Platform

Trace element variations across Middle–Upper Cambrian carbonates: Implications for the paleoenvironment of eastern Laurentia

The investigated Middle–Upper Cambrian carbonates span, from bottom to top, the uppermost Hawke Bay (40 m), the March Point (∼83 m thick), and the lowermost Petit Jardin (∼47 m) formations of the Port au Port Group (western Newfoundland, Canada). A multi-technique evaluation of the preservation of carbonates was applied by using several petrographic and chemical screening tools. The variations in several proxies of bioproductivity (e.g., P, Ni, and Cu), input of weathering products (Mn, Fe, Al, and ∑REE), and paleoredox (e.g., Th/U) have been utilized to study the paleoenvironmental conditions during the investigated time interval. Distinct positive shifts in the profiles of Al, ∑REE, Mn, and Fe have been associated with the negative shifts recorded by the δ13C profile and correlated with the DICE (Middle Cambrian) and base of the SPICE (lowermost Upper Cambrian) events. They reflect contributions from detrital weathered material during sealevel falls. Similar correlated positive shifts are also documented by the P, Ni, and Cu profiles, thus suggesting an increase in the riverine inputs of nutrients associated with the drop of sealevel and increase of weathering activities. In addition, the changes in the bioproductivity and weathering proxies were associated with relative rising in the Th/U ratios (0.1–8.3), which reflects variations in the redox state towards relatively more oxidizing conditions.

In-place operculum demonstrates that the Middle Cambrian Protowenella is a hyolith and not a mollusc

Protowenella is an early–middle Cambrian, isostrophically coiled, calcareous microfossil originally described from the middle Cambrian (Miaolingian) of Australia; it has been referred previously to the molluscan classes Monoplacophora, Helcionelloida or Gastropoda. A unique specimen from the Henson Gletscher Formation (Miaolingian Series, Wuliuan Stage) of North Greenland has a bilaterally symmetrical operculum preserved in place within the shell aperture. Paired cardinal processes and clavicles on the inner side of the operculum indicate that Protowenella was a hyolith morphologically close to the orthothecid Conotheca. Protowenella is transferred from Mollusca to Hyolitha, Order Orthothecida, Family Protowenellidae nov., representing a novel morphological departure from the generally slender cones of other hyoliths. John S. Peel [ john.peel@pal.uu.se ], Department of Earth Sciences (Palaeobiology), Uppsala University, Villavägen 16, SE-75236, Uppsala, Sweden.

Ontogeny, morphology and pedicle attachment of stenothecoids from the middle Cambrian of North Greenland (Laurentia)

Ontogeny, morphology and pedicle attachment of stenothecoids from the middle Cambrian of North Greenland (Laurentia)

Characteristics of natural gas accumulation in the Cambrian weathered crust in southwestern Ordos Basin

The Cambrian weathered crust formed in the Early Paleozoic central paleouplift of the Ordos Basin and its periphery has always been a key target for oil and gas exploration, and important breakthroughs in oil and gas exploration have been made there. In order to further accelerate the process of natural gas exploration in this area, this paper based on systematic analysis of source-reservoir assemblage and trap type in the Cambrian weathered crust in southwestern Ordos Basin, and then evaluates its natural gas exploration potentials and favorable exploration zones. The following research results are obtained. First, the Upper Paleozoic coal-measure source rocks in the basin is the main gas source rocks, forming a source-reservoir assemblage of “upper source and lower reservoir” with Cambrian reservoir. Second, the types of the reservoir in the Cambrian weathered crust are mainly dolomite intercrystalline (dissolution) pores and karst fractures and vugs, whose development is controlled by grain shoal microfacies and karstification in the weathered crust stage, respectively. Third, the traps in the Cambrian weathered crust are mainly lithologic-stratigraphic traps, which were formed in the tectonic uplifting setting of the eastern Ordos Basin during the Yanshanian. There are geological conditions of lithologic and stratigraphic barriers in the updip direction, which is beneficial to the short-distance natural gas migration and accumulation. In conclusion, Huanxian-Zhengning area on the east margin of the central paleouplift in southwestern Ordos Basin is a favorable exploration zone of Cambrian weathered crust gas reservoirs, and the Middle Cambrian Zhangxia Formation and Upper Cambrian Sanshanzi Formation are favorable intervals of oil and gas exploration.

The Use of Well-Log Data in the Geomechanical Characterization of Middle Cambrian Tight Sandstone Formation: A Case Study from Eastern Pomerania, Poland

Geomechanical characterization plays a key role in optimizing the stimulation treatment of tight reservoir formations. Petrophysical models help classify the reservoir rock as the conventional or unconventional type and determine hydrocarbon-saturated zones. Geomechanical and petrophysical models are fundamentally based on well-log data that provide reliable and high-resolution information, and are used to determine various relationships between measured borehole parameters and modeled physical rock properties in 3D space, with the support of seismic data. This paper presents the geomechanical characterization of the Middle Cambrian (Cm2) sediments from Eastern Pomerania, north Poland. To achieve the aim of this study, 1D well-log-based and 3D models based on seismic data of the rocks’ petrophysical, elastic, and strength properties, as well as numerical methods, were used. The analysis of the Middle Cambrian deposits revealed vertical and horizontal heterogeneity in brittleness, the direction of horizontal stresses, and the fracturing pressure required to initiate hydraulic fractures. The most prone to fracturing is the gas-saturated tight sandstones belonging to the Paradoxides Paradoxissimus formation of Cm2, exhibiting the highest brittleness and highest fracturing pressure necessary to stimulate this unconventional reservoir formation.

Lower and Middle Cambrian brachiopods from the Iberian Chains and Sierra Morena (Spain)

Brachiopods from the Lower and Middle Cambrian of the Iberian Chains and Sierra Morena are described. The following taxa occur in the Iberian Chains: "Lingulella" sp., Redlichella cf. bohemica (Barrande), Dictyonina radioplicata sp. n., Micromitra sp., Trematobolus simplex (Vogel), Trematobolus borobiensis sp. n. and Jamesella sp. The taxa "Lingulella" sp. and Sibiria? sp. are reported from the Lower Cambrian of Sierra Morena. Brachiopods constitute several distinct associations: the relatively shallow water Trematobolus assemblage near the Lower-Middle Cambrian boundary interval is followed by the deeper Dictyonina­Redlichella assemblage. The alternation of these assemblages permit us to interpret the response of brachiopod communities to sea level changes.

Precambrian and Early Palaeozoic metamorphic complexes in the SW part of the Central Asian Orogenic Belt: Ages, compositions, regional correlations and tectonic affinities

Precambrian metamagmatic complexes of the Zhingeldy and Kendyktas blocks of the Zheltau and Chu-Kendyktas terranes of the SW part of the Central Asian Orogenic Belt (CAOB) consist of predominant Neoproterozoic orthogneisses with the estimated protolith ages of ca. 790–800 Ma, and subordinate epidote and garnet amphibolites, metabasalts and metadolerites of the lower metamorphic grades. The orthogneisses are characterized by negative εNd(t) values of −12 to −4 with Nd model ages of 2.3–1.7 Ga, indicating their protoliths could have formed by a reworking of the Palaeoproterozoic crustal materials. Precambrian metavolcanic rocks in the studied region are rhyolites with the estimated crystallization ages of ca. 800–830 Ma, and are associated with metabasalts. Metasedimentary complexes in the studied region consist of intensively retrogressed garnet-mica schists interlayered with marmorized limestones, metasilicic rocks, epidote and garnet amphibolites and strongly altered eclogites. The inferred protoliths of the garnet-mica schists are terrigenous rocks accumulated during the latest Ediacaran – middle Cambrian and formed from Mesoproterozoic (ca. 1.0 Ga) and to a lesser extent Palaeoproterozoic felsic source rocks (ca. 1.6–1.7 Ga and ca. 2.5 Ga). The garnet-mica schists of the Kendyktas block have negative εNd(t) of −13.4 and a model age tNd(DM) of 2.2 Ga, implying formation of their protolith from Palaeoproterozoic crustal source. The studied Zheltau and Chu-Kendyktas terranes from the SW part of the CAOB have much in common in terms of Precambrian and Early Palaeozoic evolution and chemical compositions of the key rock types. The presence of the Early Precambrian rocks (Zheltau terrane), an abundance of the Late Mesoproterozoic (1000–1100 Ma) detrital zircons in the Ediacaran-Cambrian metasedimentary complexes and a wide distribution of the Late Neoproterozoic magmatism, are distinctive features of the studied terranes. We refer such Precambrian terranes of the western CAOB to the Ulutau-Moyunkum group where tectono-magmatic evolution is consistent with that observed from the northern part of the Tarim craton. Our results also aid comprehensive correlation of metamorphic complexes of the Precambrian terranes from the SW CAOB.

Brachiopods from the Latham Shale Lagerstätte (Cambrian Series 2, Stage 4) and Cadiz Formation (Miaolingian, Wuliuan), California

AbstractA moderately diverse assemblage of brachiopods from the Latham Shale Lagerstätte (Cambrian Series 2, upper Stage 4) and the upper Cadiz Formation (Miaolingian, Wuliuan), California is described in detail for the first time. The fauna includes both linguliform and rhynchonelliform brachiopods—Hadrotreta primaea(Walcott, 1902),Paterina prospectensis(Walcott, 1884),Dictyonina pannula(White, 1874), andMickwitzia occidensWalcott, 1908; andNisusia fulleriMount, 1981 andWimanella highlandensis(Walcott, 1886), respectively—together with olenellid trilobites and hyolithids. The fauna differs from other Cambrian Konservat-Lagerstätten (notably Cambrian Series 2 Chengjiang and Guanshan Lagerstätten, eastern Yunnan) in that the brachiopod shell valves in many cases are still preserved with their original mineralization. Moreover, the excellently preserved shale-hosted valves even include cases with exquisite epithelial cell molds, otherwise only seen in acid-etched material from carbonate rocks. The pitted ornamentation inD. pannulaclosely resembles that described from Ordovician linguliforms. The unusual preservation ofN. fulleriprovides important clues for ancestral composition of the brachiopod shell. The two articulated rhynchonelliform species probably represent the oldest records of this group from the west Laurentia. The fauna could also represent the earliest onset of the transition from the Cambrian Evolutionary Fauna (CEF) to the Paleozoic Evolutionary Fauna (PEF).

P-047. Elevated placental histone H3K4 methylation via upregulated histone methyltransferases in preeclampsia and its possible involvement in hypoxia-induced pathophysiology

The Cambrian weathered crust formed in the Early Paleozoic central paleouplift of the Ordos Basin and its periphery has always been a key target for oil and gas exploration, and important breakthroughs in oil and gas exploration have been made there. In order to further accelerate the process of natural gas exploration in this area, this paper based on systematic analysis of source-reservoir assemblage and trap type in the Cambrian weathered crust in southwestern Ordos Basin, and then evaluates its natural gas exploration potentials and favorable exploration zones. The following research results are obtained. First, the Upper Paleozoic coal-measure source rocks in the basin is the main gas source rocks, forming a source-reservoir assemblage of “upper source and lower reservoir” with Cambrian reservoir. Second, the types of the reservoir in the Cambrian weathered crust are mainly dolomite intercrystalline (dissolution) pores and karst fractures and vugs, whose development is controlled by grain shoal microfacies and karstification in the weathered crust stage, respectively. Third, the traps in the Cambrian weathered crust are mainly lithologic-stratigraphic traps, which were formed in the tectonic uplifting setting of the eastern Ordos Basin during the Yanshanian. There are geological conditions of lithologic and stratigraphic barriers in the updip direction, which is beneficial to the short-distance natural gas migration and accumulation. In conclusion, Huanxian-Zhengning area on the east margin of the central paleouplift in southwestern Ordos Basin is a favorable exploration zone of Cambrian weathered crust gas reservoirs, and the Middle Cambrian Zhangxia Formation and Upper Cambrian Sanshanzi Formation are favorable intervals of oil and gas exploration.

Microbially induced sedimentary structures from the Xinji Formation (Cambrian Series 2), Western Henan, North China

Abundant well‐preserved microbially induced sedimentary structures (MISS) are exposed in the Xinji Formation, the earliest Cambrian sedimentary unit in North China. The MISS herein are categorized into microbial mat growth structure (wrinkle structures and mat biolaminites) and microbial mat destruction structure (sand cracks and ‘Manchuriophycus’ structures). The MISS developed on the surface of thick quartz sandstones, as well as the lithologic interface between thin sandstone and mudstone. Most of the sand cracks lack the direct evidence of microbial activities, whereas the mat biolaminites that consist of filamentous mica, clay minerals, and quartz grains may record the in situ microbial mats. The Xinji Formation deposited along with the Cambrian explosion when biodiversity and abundance of metazoan stayed relatively low. Besides, the intermittently exposed tidal flats are not the ideal place for early life, which exacerbated the ecological vacuum therein. The massive occurrence of the MISS in the siliciclastic rocks of the Xinji Formation indicated that the tidal flat setting during this period was still beneficial for accumulations of microbial mat because of the deficient grazing metazoans and weak bioturbation.

Evidence for microbially mediated silver enrichment in a middle Cambrian Burgess Shale-type deposit, Mackenzie Mountains, northwestern Canada

The Selwyn basin and Mackenzie platform of northwestern Canada house an array of mineral deposits and prospects that are rich in silver, including Neoproterozoic red-bed or Kupferschiefer-type Cu and lower Paleozoic sedimentary exhalative (SEDEX) and Zn–Pb deposits. Within this overall metallogenic setting, the middle Cambrian (Drumian) Rockslide Formation was deposited under a largely oxic water column on the platform-to-basin slope along the eastern side of the Selwyn basin. The formation includes an interval termed the Ravens Throat River Lagerstätte, which is a localized Burgess Shale-type calcareous mudstone about 2 m thick that preserves soft-bodied fossils. The mudstone contains comparatively large amounts of organic carbon preserved as thin carbonaceous laminae and discontinuous seams, representing benthic microbial mats, the remains of cyanobacteria and algae that were living in the water column, fecal pellets, large coprolites, and degraded animal tissues. The upper part of the Rockslide Formation, including the fossiliferous interval, contains elevated concentrations of Ag, up to 0.47 ppm. Some of the Ag in the mudstone occurs as aggregates of elemental particles ∼10 µm in size, preferentially on the carbonaceous material comprising the coprolites. This localized enrichment suggests bioaccumulation of Ag nanoparticles or Ag+ from the water column by microorganisms on the coprolites or degrading organic matter in them. The source of the Ag may have been from penecontemporaneous SEDEX metallogeny or from broadly related subsurface fluids in the Selwyn Basin that enriched the overlying seawater.

A new eocrinoid from the Guanshan Biota (Cambrian Series 2, Stage 4), with implication of the development of different attachment modes in early Cambrian

Eocrinoids are scarce in the Guanshan Biota (Cambrian Series 2, Stage 4), Yunnan Province, southwest China. Here, we introduce a new gogiid: Kunmingeocrinus cupuliformis n. gen. n. sp. which is characterized by a short stalk and a well-developed attachment disc. Preservation may indicate a weakly biomineralized body for the new taxon. Morphological similarities between the new taxon and other eocrinoids with attachment discs from Cambrian Lagerstätten of Guizhou Province (Series 2, Stage 4 and Miaolingian, Wuliuan) might suggest a similar mode of life. The eocrinoids from the Guanshan Biota possibly utilized different attachment modes.

Thrombolites and ichnofossils in the Middle Cambrian of south North China Block: Implications for the environmental controls on the evolution of microbes and metazoans

Thrombolites and ichnofossils are well‐preserved in a carbonate succession of the Cambrian (Miaolingian Series) Zhangxia Formation, south North China Block. This provides a chance to investigate the factors controlling the distributions of thrombolites and metazoans. Three types of thrombolites are identified, on the basis of clot shape and their array styles, namely, bushy, columnar, and blocky thrombolites. Bushy thrombolites occur in the lower part of the study unit, columnar thrombolites in the middle, and blocky thrombolites in the upper. Thrombolitic intervals alternate with bioturbated limestones, with the latter including two ichnogenera: Balanoglossites triadicus Mägdefrau, 1932 and Sulcolithos variabilis Knaust, 2019. Both thrombolites and bioturbated limestones are covered by oolitic limestones. The facies analysis indicates depositional environments from deep to shallow subtidal, then to oolitic shoals upwards. Such a sequence represents an overall shallowing‐upward trend. Thrombolites generally flourished during transgressions, whereas bioturbated and oolitic limestones represent regressive systems. Thus, relative sea level was a main factor controlling the alternations of thrombolites and ichnofossils in the Zhangxia Formation. Although there is no clear evidence that bioturbation can directly destroy thrombolites, exploration of new habitats by benthic animals and the increasing mixing degree of substrates could have destroyed the previous firmground substrate required for thrombolite development. The alternations of thrombolites and bioturbated limestones demonstrate that ecological conditions frequently fluctuated in the neritic environment during the Middle Cambrian.

Furongian (Jiangshanian) occurrences of radiodonts in Poland and South China and the fossil record of the Hurdiidae.

The Furongian period represents an important gap in the fossil record of most groups of non-biomineralizing organisms, owing to a scarcity of Konservat-Lagerstätten of that age. The most significant of these deposits, the Jiangshanian strata of the Sandu Formation near Guole Township (Guangxi, South China), have yielded a moderately abundant, but taxonomically diverse soft-bodied fossil assemblage, which provides rare insights into the evolution of marine life at that time. In this contribution, we report the first discovery of a radiodont fossil from the Guole Konservat-Lagerstätte. The specimen is an incomplete frontal appendage of a possibly new representative of the family Hurdiidae. It is tentatively interpreted as composed of seven podomeres, six of which bearing laminiform endites. The best preserved of these endites is especially long, and it bears short auxiliary spines that greatly vary in size. This is the second occurrence of hurdiids and more generally radiodonts in the Furongian, the first being the external mould of an oral cone from Jiangshanian strata of the Wiśniówka Sandstone Formation in Poland. Restudy of this Polish specimen confirms that it belongs to a hurdiid radiodont and best compares to Peytoia. The family Hurdiidae includes the oldest (basal Cambrian Epoch 2) and youngest (Early Ordovician, possibly Early Devonian) representatives of the Radiodonta and as such, has the longest stratigraphical range of the group. Yet, hurdiids only became prominent components of marine ecosystems during the middle Cambrian (Miaolingian), and their fossil record in younger strata remains limited.

OnCallavia(Trilobita) from the Cambrian Series 2 of Iberia with systematic status of the genus

AbstractOlenellid trilobites from the lower Cambrian of the Iberian Peninsula are very scarce and poorly studied, making them difficult to compare with defined species and to include in biostratigraphic and paleobiogeographic analyses. Based on newly collected specimens, we revise the species ‘Callavia?lotzei’ Richter and Richter, 1941 from the ‘Cumbres beds’ of Cumbres de San Bartolomé and the ‘Herrerías shale’ of Cañaveral de León, Sierra del Bujo, and Hinojales (Huelva, Spain), and ‘Paradoxides choffati’ Delgado, 1904 from the Vila Boim Formation of Elvas (Portugal). The new material indicates thatCallavia?lotzeiis a junior synonym of ‘P. choffati.’ The Iberian species are here assigned toCallaviaMatthew, 1897, for which morphological characters are reassessed, offering a valuable opportunity to discuss characters previously misinterpreted for this genus. Traditionally assigned to the Olenelloidea Walcott, 1890,Callavialacks some of the diagnostic characters of this superfamily and is here assigned to Judomioidea Repina, 1979. A new diagnosis for this genus is provided, andSdzuyomiaLieberman, 2001 is considered to represent a junior synonym ofCallavia. The genusCallaviais distributed across the western margin of Gondwana, from the western Mediterranean region (Iberia and Morocco) throughout all the Avalonia sectors (UK, eastern Newfoundland, and Massachusetts). Its presence in Iberia supports the faunal links between the West Gondwana domain and Avalonia during Cambrian Series 2. The Iberian records ofCallavia choffatiare assigned to the middle part of the regional Marianian Stage (uppermost Cambrian Stage 3 to the lowermost Cambrian Stage 4) and correlates with theCallaviaBiozone of Avalonia (lower Branchian Series).

A Guzhangian (late Middle Cambrian) fauna from the Gidgealpa 1 drillhole, Warburton Basin, South Australia

A Cambrian Series 3 (Guzhangian, Boomerangian) fauna is described from Core 12 of the Gidgealpa 1 drillhole from the Warburton Basin, northeastern South Australia. There are four agnostoid taxa: Ammagnostus laiwuensis, Lejopyge calva, L. armata and an unassigned pygidium, and six polymerid trilobite taxa: Fuchouia sp., Dorypyge sp., Solenoparia changi sp. nov., Pianaspis sp., an unassigned cranidium and an unassigned pygidium. This fauna suggests a correlation with the Goniagnostus nathorsti Zone or the lower part of the Lejopyge laevigata Zone (Boomerangian on the northern Australian biostratigraphic scheme), with the latter preferred. These are the first published descriptions of fossils of this age from the Warburton Basin. Xiaowen Sun [Xiaowen_s@yahoo.com.au], Sun Petroleum Geoservices, 4 Jolie Grove, Box Hill, Victoria 3128, Australia; Christopher J. Bentley [ bigfossil@bigpond.com], 30 Albert Street, Clare, South Australia, 5453, Australia; James B. Jago [jim.jago@unisa.edu.au], University of South Australia–STEM, Mawson Lakes, South Australia 5095, Australia.

Exceptionally preserved hyolithids from the middle Cambrian of North China

AbstractHyoliths are extinct enigmatic organisms of early lophotrochozoan affinity known globally from the Palaeozoic Era and were especially diverse and abundant in the Cambrian Period. However, the commonly incomplete preservation of hyolith exoskeletons and our limited knowledge of their soft anatomy makes their ecological and biological aspects unclear. Konservat-Lagerstätte are crucial windows to unlock the mysteries of hyoliths. Here we report a new occurrence of exceptionally preserved hyolithid hyoliths from the middle Cambrian Mantou Formation (Miaolingian, Wuliuan) in Shandong Province, North China. The preserved soft organs of the new species Novakotheca weifangensis sp. nov. include a U-shaped gut and possible pharynx, oesophagus, stomach and digestive gland, which provide significant new information for the reconstruction of the digestive system of hyolithids. Two taphonomic modes of hyoliths described herein are recognized: soft tissue preservation through pyritization and three-dimensional shell preservation through phosphatization. Morphological variations due to different preservational pathways in the same species are revealed, highlighting the taphonomic bias on taxonomy. The ecological association between hyoliths and small brachiopod epibionts is a direct example of species interactions, providing insights into the ecological structures and adaptability of early animals during Cambrian time.

Corynexochine trilobites of the Harkless Formation and Mule Spring Limestone (Cambrian Series 2, Stage 4), Clayton Ridge, Nevada

AbstractMost Cambrian Series 2 faunas of Laurentia are dominated by olenelline trilobites; however, non-olenelline trilobites occur with the olenellines and sometimes dominate the assemblages. Reported here are such non-olenelline trilobites from the Harkless Formation and Mule Spring Limestone at Clayton Ridge, Nevada. At the bottom of the Saline Valley Tongue, Harkless Formation, are two assemblages that are characterized by corynexochines and/or ptychoparioids, with olenellines occurring as only rare components. The corynexochines present in these assemblages include Bonnia cf. B. brennus (Walcott, 1916), Ovatoryctocara cf. O. yaxiensis Yuan et al., 2009, Protoryctocephalus? aff. P.? arcticus Geyer and Peel, 2011, Ogygopsis sp. indet., and Oryctocephalops frischenfeldi Lermontova, 1940. These assemblages are from the mid-Dyeran Stage, below the lowermost zone in the upper Dyeran (Arcuolenellus arcuatus Biozone), and can be correlated to Series 2 Stage 4 (Cambrian) assemblages in Greenland, Siberia, and South China based on the corynexochines.Also in the Saline Valley Tongue and the overlying Mule Spring Limestone and lowermost Emigrant Formation are olenelloid-dominated assemblages that contain the corynexochines Bonnia columbensis Resser, 1936, Zacanthopsis aff. Z. levis (Walcott, 1886), and Z. sp. indet.

Morphology and ecology of the bradoriid arthropods Spinospitella and Nikolarites from the Cambrian (Series 2, Stage 4) of North Greenland (Laurentia)

Tuberculate fragments referred to Nikolarites spasskyi are compared with a complete carapace and other material of Spinospitella from Cambrian Series 2, Stage 4 in North Greenland. The descriptions expand earlier brief records from Laurentia of the two bradoriids, originally described from Siberia and Australia, respectively. The mutually exclusive occurrences of the two taxa indicate ecological control of their distribution in North Greenland. Robust fragments of Nikolarites spasskyi occur in reworked higher energy deposits of the Aftenstjernesø Formation, while thin-walled carapaces of Spinospitella characterise deeper water mudstones within the Buen and Aftenstjernesø formations.