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Exotic trilobites from the uppermost Cambrian Series 3 and lower Furongian of Sweden

Żylińska A., Weidner T., Ahlgren J., Ahlberg P.

Acta Geologica Polonica

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2015

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Vol. 65, no. 1

21--67

EN

Seventeen taxa of exotic trilobites representing eight families are described from the olenid- and agnostoid-dominated strata of the uppermost Cambrian Series 3 and lower Furongian alum shale facies of Sweden and from glacial erratic boulders of Denmark. Only five taxa are assigned to species level, i.e., Maladioidella abdita (Salter, 1866), Olentella rara (Westergård, 1922), Pedinocephalus peregrinus (Henningsmoen, 1957), Ptychoparia pusilla (Westergård, 1922), and Westergaardella olenorum (Westergård, 1922), whereas the others are left under open nomenclature or remain unrecognized. Most are described for the first time from the Cambrian of Scandinavia. Their affinities point to a strong connection with East Gondwana, Laurentia, Kazakhstania and Siberia. Exotic trilobites appear in the succession directly after periods of very low oxygen concentration in the Alum Shale Sea; their occurrences correspond to the ranges of agnostoid arthropods in the succession and seem to be linked to global transgressive events causing an influx of cool and/or oxygen-depleted waters onto the shelf of the Baltica palaeocontinent.

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Rusophycus inexpectus isp. nov. from the Furongian (Upper Cambrian) of the Holy Cross Mountains (Poland

Sadlok G.

Annales Societatis Geologorum Poloniae

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2014

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Vol. 84, No. 2

143--151

EN

A new trace fossil Rusophycus inexpectus isp. nov. is described from the Furongian (Upper Cambrian) strata of the Holy Cross Mountains. This ichnospecies is probably non-trilobite in origin and is commonly preserved as an undertrace. This preservation style resembles that of Rusophycus ramellensis Legg, an index fossil of the Cambrian Series 3. Therefore, previous workers misinterpreted material from the Wiśniówka Sandstone Formation as Rusophycus ramellensis Legg (recorded by them as Cruziana barbata) and put the Cambrian Series 3 and Furongian boundary within this unit. Rusophycus inexpectus isp. nov differs from Rusophycus ramellensis Legg: 1) in having a smooth trapezoidal area behind the lobes; 2) in the presence of a direct contact between the endopodal lobes and cephalic margin imprints and 3) in the restriction of the occurrence of the endopodal lobes and scratches to the cephalic region of the trace fossil. Care must be taken, when dealing with the undertrace preservation style of Rusophycus ramellensis Legg in other assemblages, as it may represent Rusophycus inexpectus isp. nov.

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New data on the trace fossil, Cruziana semiplicata (Furongian, Wiśniówka Sandstone Formation, Poland) : origin, ethology and producer

Sadlok G.

Annales Societatis Geologorum Poloniae

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2014

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Vol. 84, No. 1

35--50

EN

Cruziana semiplicata Salter is a well known ichnospecies, ascribed to trilobites. Despite that, there are still contradicting views on its origin (infaunal vs. epifaunal), the ethology represented (crawling vs. feeding) and the identity of its producer (a few trilobite genera were proposed). In this paper, new data are presented and com- bined to create a coherent interpretative model for Cruziana semiplicata. According to this new model, Cruziana semiplicata is a fossilized version of an epifaunal, pascichnial (feeding) trace produced by an organism, positioned above the seabed with only a few frontal appendages touching the depositional surface and processing the sedi- ment below. This model is based on observations of trace fossil morphology and neoichnological observations of the feeding behaviour of Triops australiensis. Also, a short geometrical comparison with the co-occurring Rusophycus polonicus is made to show that these trace fossils most likely had different trace makers.

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Sadlok G.

Annales Societatis Geologorum Poloniae

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2013

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Vol. 83, No. 4

317--327

EN

In general, the trace fossil Rusophycus, preserved as a concave-upward structure on the top of a bed, is considered to be a fossilized marking, made by a trace maker. The structures described from the Cambrian (Furongian) of central Poland are genetically related to Rusophycus. However, despite their occurrence on the tops of beds, they are not fossilized traces, but compaction-related features, resulting from differential sandstone and mudstone compaction with possible mediation by organic-rich, heterolithic sediments. The preservation of these structures probably was influenced by biofilms or biomats.

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Slide origin of breccia lenses in the Cambrian of the North China Platform: new insight into mass transport in an epeiric sea

Van Loon A. J. (Tom), Han Zuozhen, Han Yu

Geologos

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2012

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Vol. 18, No. 4

223--235

EN

An oolite in the Furongian (Late Cambrian) Chaomidian Formation in Shandong Province, China, which was deposited on the North China Platform in an epeiric sea, contains several limestone breccia lenses of various dimensions (centimetres to decimetres thick and decimetres to more than 10 metres in length) in an E-trending section. The oolite, which is approximately 40 cm thick, was originally thicker, as indicated by a planar truncation surface that formed by wave abrasion. The breccia lenses in this oolite are generally mound-shaped with a flat base and a convex top. The western margin of the lenses is commonly rounded whereas the eastern margin commonly has a tail (consisting of a rapidly eastwards thinning breccia horizon that gradually ends in a horizon of isolated clasts). Some of the breccia lenses are underlain by a shear zone. The formation of the breccia lenses cannot be easily explained by normal depositional or deformational processes. It is concluded that the lenses represent fragments of a partly consolidated layer, consisting of both rounded and angular platy clasts, which slid down over a very gently inclined sedimentary surface which acted - possibly together with a water film - as a lubricant layer. During transport, the layer broke up into several discrete bodies that formed small ‘highs’ at the sedimentary surface of the shallow epeiric sea. Subsequently, waves partially eroded the lenses, mostly at their margins, producing their mound-shaped form. Sliding of blocks is known from a wide variety of environments in the sedimentary record; however, this is the first description of the sliding of blocks in an epeiric sea. This indicates that such a low-relief submarine carbonate setting is, like its siliciclastic counterparts, susceptible to this process.

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Wstępne dane o tropach stawonogów z furongu (górnego kambru) Wiśniówki Wielkiej (Góry Świętokrzyskie) i ich tafonomii

Sadlok G.

Przegląd Geologiczny

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2011

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Vol. 59, nr 1

82-90

EN

Previous works on arthropod trace fossils from the Furongian (Upper Cambrian) section exposed at theWioeniówkaWielka quarry (Holy Cross Mountains, Poland) focused on trilobite-made structures referred to as Rusophycus polonicus and Cruziana semiplicata. Arthropod trackways did not receive much attention. The present paper contains preliminary data on new records of arthropod trackways from the Furongian of the Wioeniówka Wielka section and on their taphonomy. The material studied comprises undetermined arthropod tracks and specimens belonging to three ichnogenera: ?Asaphoidichnus, Diplichnites and Petalichnus.

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The trace fossil Rusophycus versans from the Furongian (Upper Cambrian) of central Poland - an example of behavioural convergence amongst arthropods

Sadlok G., Machalski M.

Acta Geologica Polonica

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2010

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Vol. 60, no. 1

119-123

EN

Traces assigned to Rusophycus versans are recorded for the first time from Furongian (Upper Cambrian) strata, as exposed at Wiśniówka Wielka quarry, Holy Cross Mountains, central Poland. These traces are ascribed to the life activity of trilobites in a fully marine environment. In contrast, previous records of R. versans have been attributed to notostracans, isopods or arthropleurids and are preserved in non-marine settings. The relatively wide phylogenetic distribution of R. versans within various arthropod groups indicates that this ichnotaxon represents behavioural convergence amongst arthropods.