Middle–late Cambrian acritarchs of the Zagros Basin, southwestern Iran

Spina, Amalia; Cirilli, Simonetta; Ghorbani, Mansour; Rettori, R; Sorci, Andrea; Servais, Thomas

doi:10.1080/01916122.2020.1771624

Cited by 14 publications

(10 citation statements)

References 62 publications

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“…Paleomagnetic data together with palaeontological and stratigraphic correlations strongly support a north Gondwanan affinity for Iran and a position near the Arabian Plate during the Cambrian (Alavi, 2004; Becker et al, 1973; Berberian & King, 1981; Ghavidel‐syooki & Vecoli, 2008; Soffel & Forster, 1980; Spina et al, 2020; Vecoli & Le Hérissé, 2004; Wensink, 1983). This location is further supported by previous provenance studies on the Lalun Formation using detrital zircon U–Pb–Hf and rutile U–Pb and trace element analyses (Zoleikhaei et al, 2021; Figure 9), which indicate sediment sources within the Arabian sector of the ANS.…”

Section: Discussionmentioning

confidence: 87%

Evaluating sediment recycling through combining inherited petrogenic and acquired sedimentary features of multiple detrital minerals

2022

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An implicit assumption of most sedimentary provenance analyses is a direct link between source and sink. However, recycling of sedimentary detritus from pre‐existing strata interrupts the direct source‐to‐sink link and can result in incorrect interpretations of paleogeography and paleodrainage. Detrital zircon is the favoured proxy of contemporary provenance studies, but its physiochemical resilience makes it particularly prone to recycling. In this study, we integrate geochemical (age, isotope, and trace elements) and grain roundness data of multiple detrital minerals with different physiochemical stabilities (zircon, tourmaline, rutile, and apatite) to evaluate the importance of recycling in an ancient sedimentary basin. We focus on the early Cambrian Lalun Formation of Iran, which forms part of a laterally extensive sandstone‐rich succession deposited along the northern margin of Gondwana. The Lalun Formation preserves a distinct change of compositional maturity between lower arkose and shale units and an upper unit of quartz‐rich sandstone. Detrital zircon, rutile, and apatite data demonstrate that all units of the Lalun Formation share a common source in the Arabian‐Nubian Shield. Whole‐rock geochemical data further indicate that all units have similar chemical alteration indices, suggesting the change in compositional maturity is not a product of differential weathering of the source region. Analysis of grain roundness reveals that detrital zircon, rutile, and tourmaline in the upper quartz‐rich unit are typically more rounded than those in the underlying arkose and shale units. In contrast, detrital apatite grains are nearly all angular in the quartz‐rich unit but mostly rounded in the lower arkose and shale. Together, the detrital mineral provenance, whole‐rock geochemistry, and morphological data are consistent with recycling of the lower arkose and shale units of the Lalun Formation into the uppermost quartz‐rich unit, with the latter also receiving a component of first‐cycle detritus represented by angular detrital apatite. Our findings demonstrate that integrating the features of detrital minerals acquired during a sedimentary cycle (grain rounding and diversity of mineral assemblages) with features inherited from their ultimate source rocks (age, isotopic, and geochemical proxies) can assist in recognising sediment recycling in ancient strata.

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Section: Discussionmentioning

confidence: 87%

Evaluating sediment recycling through combining inherited petrogenic and acquired sedimentary features of multiple detrital minerals

2022

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“…In Arctic Norway, these fossils appear immediately above the first occurrence of palaeopascichnids and below the first Ediacara-type fossils including discs and dickinsoniamorphs (Högström et al 2013(Högström et al , 2017Jensen et al 2018b), suggesting an age of 565-550 Ma based on radioisotopic ages that constrain similar fossils assemblages (cf. Jensen et al 2018b;Kolesnikov et al 2018;Soldatenko et al 2019). These examined units are not coeval, but their ages are mostly younger than the Shuram anomaly, the most negative carbon isotope excursion in Earth's history and a global, synchronous event with bounding Re-Os ages of 574.0 ± 4.7 to 567.3 ± 3.0 Ma (Rooney et al 2020).…”

Section: B the Life And Times Of The Granomarginata-lagoenaforma Associationmentioning

confidence: 90%

Late Ediacaran occurrences of the organic-walled microfossilsGranomarginataand flask-shapedLagoenaforma collarisgen. et sp. nov.

et al. 2021

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New occurrences of flask-shaped and envelope-bearing microfossils, including the predominantly Cambrian taxon Granomarginata, are reported from new localities, as well as from earlier in time (Ediacaran) than previously known. The stratigraphic range of Granomarginata extends into the Cambrian System, where it had a cosmopolitan distribution. This newly reported Ediacaran record includes areas from Norway (Baltica), Newfoundland (Avalonia) and Namibia (adjacent to the Kalahari Craton), and puts the oldest global occurrence of Granomarginata in the Indreelva Member (< 563 Ma) of the Stáhpogieddi Formation on the Digermulen Peninsula, Arctic Norway. Although Granomarginata is rare within the assemblage, these new occurrences together with previously reported occurrences from India and Poland, suggest a potentially widespread palaeogeographic distribution of Granomarginata through the middle–late Ediacaran interval. A new flask-shaped microfossil Lagoenaforma collaris gen. et sp. nov. is also reported in horizons containing Granomarginata from the Stáhpogieddi Formation in Norway and the Dabis Formation in Namibia, and flask-shaped fossils are also found in the Gibbett Hill Formation in Newfoundland. The Granomarginata–Lagoenaforma association, in addition to a low-diversity organic-walled microfossil assemblage, occurs in the strata postdating the Shuram carbon isotope excursion, and may eventually be of use in terminal Ediacaran biostratigraphy. These older occurrences of Granomarginata add to a growing record of body fossil taxa spanning the Ediacaran–Cambrian boundary.

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“…This formation has a thickness of 100 m and consists mainly of medium-to thickly-bedded brachiopod-bearing fossiliferous limestone. Based on palynological data, this formation was assigned to the late Middle-Late Cambrian (Ghavidel-Syooki 2006, 2019Ghavidel-Syooki and Vecoli 2008;Spina et al 2021) in both the Zagros and the Alborz Mountains. The Lashkarak Formation overlies the Mila Formation, and the Geirud Formation disconformably rests at the top (Figures 3 and 4).…”

Section: Geological Setting and Lithostratigraphymentioning

confidence: 99%

Peri-Gondwanan acritarchs and chitinozoans from the Lower–Middle Ordovician Lashkarak Formation in the Alborz Mountain Ranges, northern Iran: regional stratigraphical significance and palaeogeographical implications

Ghavidel‐Syooki

Piri-Kangarshahi

2023

Palynology

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The Lashkarak Formation (Lower-Middle Ordovician) in the Gerdkuh locality, 10 km west of Damghan city, northern Iran, has been found to contain acritarchs and chitinozoans. This study aimed to understand these chitinozoan and acritarch successions as well as brachiopods in this part of the Alborz Mountains, in a novel manner. Ninety-seven surface samples from this succession were collected and analysed. Thirty samples yielded well-preserved palynomorph taxa such as acritarchs, chitinozoans, and scolecodonts, as well as graptolite remains. In total, 53 taxa were identified among the acritarchs (38 species belonging to 21 genera) and chitinozoans (15 species belonging to 10 genera). Although scolecodonts and graptolite remains were also observed, they were not studied in detail. The palynological analyses revealed the presence of several diagnostic acritarchs in the Lashkarak Formation, including Vulcanisphaera simplex, Arbusculidium filamentosum, Coryphidium bohemicum, Dactylofusa velifera, Striatotheca mutua, Arkonia virgata, and Orthosphaeridium ternatum. These acritarchs allowed the recognition of five acritarch assemblage zones. Similarly, seven chitinozoan biozones were recognised: Eremochitina brevis, Desmochitina ornensis, Belonechitina henryi, Cyathochitina protocalix, Cyathochitina calix, Siphonochitina formosa, and Laufeldochitina clavata. These findings confirm the inclusion of the Alborz Mountains in the peri-Gondwana palaeoprovince during the Early-Middle Ordovician. The co-occurrence of the acritarch and chitinozoan taxa with previously identified brachiopods allowed for the establishment of a more detailed Early-Middle Ordovician biozonation, demonstrating their potential usefulness for global chronostratigraphy. Based on palynological and brachiopod assemblages, a shallow marine inner shelf setting is suggested for the Early-Middle Ordovician at the Gerdkuh locality. Moreover, in this study, four new morphotype species were erected, consisting of one new chitinozoan (Cyathochitina gerdkuhensis sp. nov.) and three new acritarchs (Baltisphaeridium razii sp. nov., Navifusa alborzensis sp. nov., and Orthosphaeridium iranense sp. nov.). However, Othosphaeridium cf. ternatum was left in open nomenclature. HIGHLIGHTSPalynomorphs from the Lower-Middle Ordovician (Lashkarak Formation) were recorded from the Alborz Mountains. 15 chitinozoan species (10 genera) were recorded from the Lashkarak Formation, S. Caspian Sea. 38 acritarch taxa (21 genera) were identified, indicating the N. Gondwanan Domain. The diagnostic acritarch taxa are Arbusculidium, Coryphidium, Striatotheca, and Arkonia. Chitinozoan biozones are E. brevis, D. ornensis, B. henryi, C. protocalix, C. calix, S. formosa, and L. clavata. Baltisphaeridium razii sp. nov., Navifusa alborzensis sp. nov., Cyathochitina gerdkuhensis sp. nov., and Orthosphaeridium iranense sp. nov. is recorded for the first time. A major hiatus corresponds to the Late Ordovician, Silurian, and Early-Middle Devonian.

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Middle–late Cambrian acritarchs of the Zagros Basin, southwestern Iran

Cited by 14 publications

References 62 publications

Evaluating sediment recycling through combining inherited petrogenic and acquired sedimentary features of multiple detrital minerals

Evaluating sediment recycling through combining inherited petrogenic and acquired sedimentary features of multiple detrital minerals

Late Ediacaran occurrences of the organic-walled microfossilsGranomarginataand flask-shapedLagoenaforma collarisgen. et sp. nov.

Peri-Gondwanan acritarchs and chitinozoans from the Lower–Middle Ordovician Lashkarak Formation in the Alborz Mountain Ranges, northern Iran: regional stratigraphical significance and palaeogeographical implications

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