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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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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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Trace fossil Cruziana tenella from the Furongian (Upper Cambrian) deposits of Poland

Sadlok G.

Acta Geologica Polonica

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2010

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Vol. 60, no. 3

349-355

EN

A minute, bilobate ribbon-like trace fossil, assigned to the ichnospecies Cruziana tenella, is recorded for the first time from Furongian (Upper Cambrian) strata of the Wiśniówka Formation exposed in the Wiśniówka Wielka quarry, Holy Cross Mountains, central Poland. The collected material of C. tenella is interpreted as arthropod pascichnia trails. A significant gap in size distribution and morphology between C. tenella and other Cruziana trails from Wiśniówka Wielka suggests that the former cannot be regarded as produced by juveniles of the biotaxa responsible for the latter. C. tenella from Wiśniówka Wielka was most probably produced by arthropods reaching a small adult size.

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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.