The Lower Cambrian Wrekin Quartzite and the age of its unconformity on the Ercall Granophyre

Exceptionally preserved 'Burgess Shale-type' fossil assemblages from the Cambrian of Laurentia, South China and Australia record a diverse array of non-biomineralizing organisms. During this time, the palaeocontinent Baltica was geographically isolated from these regions, and is conspicuously lacking in terms of comparable accessible early Cambrian Lagerst€ atten. Here we report a diverse assemblage of small carbonaceous fossils (SCFs) from the early Cambrian (Stage 4) File Haidar Formation of southeast Sweden and surrounding areas of the Baltoscandian Basin, including exceptionally preserved remains of Burgess Shale-type metazoans and other organisms. Recovered SCFs include taxonomically resolvable ecdysozoan elements (priapulid and palaeoscolecid worms), lophotrochozoan elements (annelid chaetae and wiwaxiid sclerites), as well as 'protoconodonts', denticulate feeding structures, and a background of filamentous and spheroidal microbes. The annelids, wiwaxiids and priapulids are the first recorded from the Cambrian of Baltica. The File Haidar SCF assemblage is broadly comparable to those recovered from Cambrian basins in Laurentia and South China, though differences at lower taxonomic levels point to possible environmental or palaeogeographical controls on taxon ranges. These data reveal a fundamentally expanded picture of early Cambrian diversity on Baltica, and provide key insights into high-latitude Cambrian faunas and patterns of SCF preservation. We establish three new taxa based on large populations of distinctive SCFs: Baltiscalida njorda gen. et sp. nov. (a priapulid), Baltichaeta jormunganda gen. et sp. nov. (an annelid) and Baltinema rana gen. et sp. nov. (a filamentous problematicum).

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“…1979; Hagenfeldt , ; Wright et al . ; Konzalová ; Jachowicz & Moryc ; Zang et al . ; Palacios et al .…”

Section: Small Carbonaceous Fossilsunclassified

A cryptic record of Burgess Shale‐type diversity from the early Cambrian of Baltica

et al. 2016

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“…The Random–Brigus unconformity is suggested here to be comparable to the abrupt lithologic change between the wave-influenced tide-dominated shelf facies of the Wrekin Quartzite (Wright et al . 1993) and overlying greenish-grey, somewhat calcareous, lowest part of the Lower Comley Sandstone (Fig. 2).…”

Section: Earliest Appearance Of Trilobites In Avaloniamentioning

confidence: 99%

“…As discussed below, this interpretation also implies a lengthy hiatus in the Comley area, and supporting evidence comes from Lower Cambrian trace fossils and sparse acritarchs in the Wrekin (Wright et al . 1993) and correlation of the Lower Comley Sandstones.…”

Section: Earliest Appearance Of Trilobites In Avaloniamentioning

confidence: 99%

Reconstructing the Avalonia palaeocontinent in the Cambrian: A 519 Ma caliche in South Wales and transcontinental middle Terreneuvian sandstones

2013

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An Early Cambrian caliche on the St Non's Formation (emended) is the base of the Caerfai Bay Formation (unit-term changed) at Caerfai Bay, South Wales. Subaerial exposure and the caliche mean the two formations were not genetically related units. The St Non's is an older sand sheet (likely tidalitic, not delta-related) referred to Avalonian depositional sequence (ADS) 2, and the Caerfai Bay is a shallow mud basin unit refered to ADS 4A. The similar Random Formation (upper ADS 2) in North American Avalonia has a basal age of c. 528 Ma and is unconformably overlain by red mudstones or sandstones in fault-bounded basins on the Avalonian inner platform. Coeval British sandstones (lower Hartshill, Wrekin, St Non's, Brand Hills?) are unconformably overlain by latest Terreneuvian (ADS 3) or Epoch 2 (ADS 4A) units. Dates of 519 Ma on Caerfai Bay ashes give an upper bracket on the late appearance of Avalonian trilobites and suggest an ADS 2-4A hiatus of several million years. Post-St Non's and post-Random basin reorganization led to abundant Caerfai Bay Formation volcanic ashes and sparse Brigus Formation ashes in Newfoundland.The broad extent of erosional sequence boundaries that bracket lithologically similar to identical units emphasize that 'east' and 'west' Avalonia formed one palaeocontinent. The inner platform in southern Britain was larger than the Midlands craton, a tectonically defined later Palaeozoic area unrelated to terminal Ediacaran -Early Palaeozoic depositional belts. The cool-water successions of Early Palaeozoic Avalonia were distant from coeval West Gondwanan carbonate platforms.

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“…It has also recently been proposed that the Wentnor Group is unconformable on the Stretton Group (Compston, Wright & Toghill, 2002), but no new evidence was presented and is not reconcilable with our field observations (Pauley, 1990(Pauley, , 1991McIlroy & Horák, in press). The Uriconian is, however, in unconformable contact with the overlying Wrekin Quartzite, which is estimated at about 530 Ma, with the local marine Cambrian * Author for correspondence: dmc@esd.mun.ca transgression thus being estimated as spanning 520-530 Ma (Wright et al 1993). This indicates, therefore, that the 6000 m thick Longmyndian Supergroup is an expanded late Neoproterozoic (Ediacaran) succession.…”

Section: Introductionmentioning

confidence: 99%

Fossils and matgrounds from the Neoproterozoic Longmyndian Supergroup, Shropshire, UK

McIlroy

Crimes

Pauley³

2005

Geol. Mag.

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Body and trace fossils of Ediacaran affinity are described from strata of the late Neoproterozoic Longmyndian Supergroup exposed near Church Stretton, Shropshire, UK. The almost spherical soft-bodied Ediacaran fossil Beltanelliformis brunsae Menner occurs rarely in the Burway Formation, but much smaller, simpler, discoidal structures are common in both the Burway and Synalds formations and are referred to Beltanelliformis minutae sp. nov. Similar discoidal structures, but with a distinct central depression, are included in Intrites punctatus Fedonkin and are common at several horizons. Two blocks with numerous examples of Medusinites aff. asteroides (Sprigg) Glaessner & Wade were recovered from the Burway Formation. The purported Ediacaran body fossil ‘Arumberia’ Glaessner & Walter is common at several horizons but its biogenicity is not accepted herein. ‘Arumberia’ is thus treated along with evidence for microbially bound sediment surfaces or matgrounds that have been suggested by several authors to be necessary for some types of Ediacaran preservation. The assemblage of simple trace and body fossils along with matgrounds is typical of latest Neoproterozoic time, though some elements range into the Phanerozoic.

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The Lower Cambrian Wrekin Quartzite and the age of its unconformity on the Ercall Granophyre

Cited by 14 publications

References 20 publications

A cryptic record of Burgess Shale‐type diversity from the early Cambrian of Baltica

A cryptic record of Burgess Shale‐type diversity from the early Cambrian of Baltica

Reconstructing the Avalonia palaeocontinent in the Cambrian: A 519 Ma caliche in South Wales and transcontinental middle Terreneuvian sandstones

Fossils and matgrounds from the Neoproterozoic Longmyndian Supergroup, Shropshire, UK

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