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A strongly positive sulphur isotopic shift in late Ediacaran-early Cambrian seawater : evidence from evaporites in the Salt Range Formation, northern Pakistan

Meng Fanwei, Zhang Zhili, Bukowski Krzysztof, Zhuo Qingong, Ahsan Naveed, Ur-Rehman Saif, Ni Pei

Geological Quarterly

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2021

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Vol. 65, No. 2

art. no. 30

EN

The Salt Range Formation in northern Pakistan is globally well-known for its extremely large evaporite deposits dated to the upper Ediacaran-lower Cambrian. This huge evaporite belt formed an area covering present-day parts of India, Pakistan, Iran, Oman, and even South China (~200,000 km2 in South China). Sulphate minerals, including anhydrite and gypsum, can continuously record seawater sulphur isotopic composition. Until now, there was only one dataset reporting the isotopic composition of evaporites in Pakistan. This study reports new data, which points to a strongly positive sulphur isotopic shift (>+30‰, VCDT values) in the Salt Range Formation in Pakistan. Based on the stratigraphic position, similarity in lithology, age, and sulphur isotope data of the evaporitic sequences, it can be inferred that the Neoproterozoic Indo-Pakistan Plate and the Yangtze Platform were closely related palaeogeographically during the terminal Neoproterozoic. This interpretation can improve understanding of the palaeogeographical evolution of the area during the Neoproterozoic, with particular reference to the origin of biogeochemical cycles and the diagenetic evolution of the evaporitic deposits.

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The Cambrian trilobites of Jordan - taxonomy, systematic and stratigraphic significance

Elicki O., Geyer G.

Acta Geologica Polonica

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2013

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Vol. 63, no. 1

1-56

EN

Marine carbonates and siliciclastic rocks of the Burj Formation in Jordan include paucispecific trilobite associations of the (traditional) Lower. Middle Cambrian boundary interval. Comprehensive new material of these trilobites allows a review of their taxonomy and systematic positions as well as a refined morphological description and a reconsideration of previous interpretations of their stratigraphic position and thus the correlation of the fossiliferous beds. In addition to the classic species Kingaspis campbelli (King, 1923) and Redlichops blanckenhorni Richter and Richter, 1941, Timnaella? orientalis (Picard, 1942) and Hesa problematica Richter and Richter, 1941, the discussed trilobites include Issalia gen. nov. with Issalia scutalis gen. nov., sp. nov., Tayanaspis gen. nov. with Tayanaspis bulbosus gen. nov., sp. nov., Uhaymiria gen. nov. with Uhaymiria glabra gen. nov., sp. nov., Cambrunicornia? jafnaensis sp. nov., Myopsolenites palmeri (Parnes, 1971), M. hyperion sp. nov., and Enixus cf. antiquus (Chernysheva, 1956). Myopsolenites boutiouiti Geyer and Landing, 2004 is now regarded as a junior synonym of Myopsolenites altus (Lian and Gozalo, 1986). A detailed discussion of the correlation with a focus on global aspects provides clues for the utility of potential index fossils for the global Cambrian Series 3 and Stage 5.

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A unified Lower - Middle Cambrian chronostratigraphy for West Gondwana

Geyer G., Landing E.

Acta Geologica Polonica

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2004

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Vol. 54, no. 2

179--218

EN

Similarities in biotic successions support a unified, composite chronostratigraphy for the Lower-Middle Cambrian of the Iberian and Moroccan margins of West Gondwana. The Curdubian Series (emended from an Iberian stage-level unit) comprises the sub-trilobitic Lower Cambrian of West Gondwana. This series represents ca. half of the Cambrian (ca. 25 m.y.), has a base defined at the lowest occurrence of diagnostic Cambrian ichnogenera in central Spain, and is comparable to the Placentian Series of Avalon. The overlying trilobite-bearing Lower Cambrian (ca. 9 m.y. duration), or Atlasian Series (new), of West Gondwana consists of two stages originally defined in highly fossiliferous (trilobites and archaeocyaths) Moroccan sections where they have great potential for precise U-Pb geochronology. The penultimate Lower Cambrian stage, the Issendalenian, with the near-joint lowest occurrence of trilobites and archaeocyaths, is approximately comparable with the sparsely fossiliferous, Iberian"Ovetian Stage" (designation abandoned). The "Ovetian" as currently revised is invalid because it is an objective homonym of Sdzuy's original "Ovetian". The "Ovetian" is not a practically applicable unit as its basal stratotype horizon lacs any identified fossils, and its trilobites are so rare that it cannot serve as a standard for interregional correlation. By contrast, the Banian Stage as defined in Marocco is suitable as the terminal Lower Cambrian stage of West Gondwana. It is based on very fossiliferous successions that allow recognition of three successive trilobite zones and is similar in concept to the Iberian 'Marianian Stage' (designation abandoned). The "Marianian" lacs a designated lower boundary stratotype locality, lacs a biostratigraphically defined base at a stratotype, and is so sparsely fossiliferous that no biostratigraphic zonation exists. Long-term problems involving regional definition of the West Gondwana Lower-Middle Cambrian boundary are resolved. The lowestoccurrence of paradoxidid trilobites, the classic index for the base of the Middle Cambrian, is diachronous in West Gondwana and other regions, with the group showing a delayed appearance in Iberia, Sweden, and Bohemia, by comparison with Morocco. Taxonomic revision of Iberian trilobites and new documentation of their ranges in Morocco show that the Iberian terminal "Lower Cambrian" "Bilbilian Stage" (designation abandoned) correlates with the Moroccan upper Banian and lower and middle "Tissafinian" Stages and with the Siberian upper Toyonian (traditionally assigned to the Lower Cambrian in Siberia) and lower Amgan (assigned to the Middle Cambrian in Siberia) Stages. The "Bilbilian" thus includes Middle Cambrian strata in a traditional international concept. Faunas from the base of the Iberian "lowest" Middle Cambrian "Leonian Stage" (designation abandoned) correlate largely into the second trilobite zone of the "Tissafinian" and are now understood to appear above an intra-Middle Cambrian faunal break. This faunal break is still poorly understood and may be an artifact of collection failure immediately above the sparsely fossiliferous, problematical "Valdemiedes event" interval. The base of this "Middle Cambrian", now termed Celtiberian Series (new designation), in west Gondwana is best defined by the base of the lower Middle Cambrian Agdzian Stage (new designation). The Agdzian includes the "Tissafinian" and overlying lower "Toushamian Stage" (designations abandoned) of Morocco, and has its top defined by the base of the middle Middle Cambrian Caesaraugustian Stage, as defined in Spain at the lowest occurrence of Badulesia tenera. The Languedocian, originally defined at the lowest occurrence of Solenopleuropsis (Manublesia) thorali in the southern Montagne Noire of France comprises the third, and terminal stage of the Celtiberian Series. We suggest that the designations "Lower Cambrian" and "Middle Cambiran" be regarded as descriptive and nonchronostratigra-phic terms in discussions of the Cambrian. New taxa or taxonomic combinations include Myopsolenites altus (Linan & Gozalo, 1986), M. boutiouiti sp. nov., M. kielciensis (Bednarczyk, 1970), and Hamatolenus (Hamatolenus) vincenti sp. nov.