Graptolite turnover and δ13Corg excursion in the upper Wenlock shales (Silurian) of the Holy Cross Mountains (Poland)

Radzevičius, Sigitas; Raczyński, Paweł; Užomeckas, Marius; Norkus, Audrius; Spiridonov, Andrej

doi:10.2478/geoca-2019-0012

Cited by 4 publications

(1 citation statement)

References 80 publications

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“…While the beginning of the parvus interval is accompanied by stable isotope and gamma ray excursions associated with the aftermath of the early part of the Mulde event both in the Viduklė-61 core and elsewhere in the Baltic Basin (Radzevičius et al 2014(Radzevičius et al , 2017(Radzevičius et al , 2019Venckutė-Aleksienėet al 2016), the diversity of sampled localities and species analysed for counts of annuli is too low in the parvus Biozone to allow for any inferences of environmental correlation.…”

Section: Discussionmentioning

confidence: 99%

Dynamic ecophenotypy in the Silurian Monograptidae (Graptolithina)

Whittingham

Spiridonov

Radzevičius

2021

Earth and Environmental Science Transactions of the Royal Society of Edinburgh

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The monograptids from the Wenlock and Ludlow (mid- to late Silurian) of the palaeotropical Baltic Basin exhibit thickened ring structures (sicular annuli) over their initial phase of growth. Appearing before the lundgreni extinction event, they persisted throughout the remainder of the Silurian, fluctuating in number over that period. To better understand the mechanisms controlling their development and variation, counts of sicular annuli were taken from three well cores in Lithuania, compared between species in each sample and compared with contemporaneous gamma ray data, accompanied by the stable isotope (δ13C), and acritarch diversity data. Mean counts of annuli fluctuated greatly over the studied interval, but showed negligible variation between species, indicating that the trait is ecophenotypic. The fluctuation in annulus presence aligned with variations in fourth- and fifth-order cycles derived from the gamma ray trends, which represent significant sea level fluctuations, δ13C ratios, and primary productivity, suggesting that annuli were more plentiful in high-stand states which are associated with the wetter climate and more productive conditions, whereas dryer, less productive conditions were not conducive to annulus development. In light of this evidence, we hypothesise that the action of upwelling as a result of intensified storm events during wetter periods would have encouraged phytoplankton blooms, increasing construction of annuli. These results show the potential utility of sicular annuli in the study of Silurian climate change and give new insights into graptolite palaeoecology.

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Section: Discussionmentioning

confidence: 99%

Dynamic ecophenotypy in the Silurian Monograptidae (Graptolithina)

Whittingham

Spiridonov

Radzevičius

2021

Earth and Environmental Science Transactions of the Royal Society of Edinburgh

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The Holy Cross Mountains (Poland) terranes palaeoposition and depositional environment in Silurian—new insights from rock magnetic studies

Niezabitowska

Szaniawski²

2023

Geophysical Journal International

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Summary The Holy Cross Mountains (HCM) in Poland, is an isolated natural outcrop of Paleozoic rocks located within the Trans-European Suture Zone (TESZ), a tectonic collage of continental terranes adjacent to the Tornquist margin of the Baltica. This uniqueness made the HCM a target for paleogeographic research. Based on the facies differences, the HCM had been divided into two major units, the southern (the Kielce Unit) and northern (the Łysogóry Unit) part (SHCM and NHCM, respectively). Their position in relation to each other and the Baltica continent during Silurian times is still a matter of discussion, whether both parts of the HCM were separated terranes located along the Baltica margin or they shared in common paleogeographic history. Here, we present the results of comprehensive rock magnetic measurements applied as a tool to interpret paleoenvironmental conditions during deposition and burial and therefore allow discussion about the terranes’ relative position. To recognize the magnetic mineral composition and texture of studied Silurian graptolitic shales several rock magnetic measurements were conducted including low-temperature Saturated Isothermal Remanent Magnetization (SIRM), thermal demagnetization of three-component IRM, and hysteresis measurements, as well as anisotropy of magnetic susceptibility (AMS). The sampled rocks come from both units of the HCM. In all analyzed samples we found single domain (SD) stoichiometric magnetite of mostly diagenetic (i.e., postdepositional) origin and goethite resulting likely from weathering. In turn, detrital magnetite, even if observed in previously investigated Silurian rocks from the Baltica margin, was not identified in this study, what we attribute to dissolution during diagenesis in the deep-water environment. Solely in the NHCM, SD hematite and maghemite grains were observed, which we interpret as detrital in origin. These grains have been preserved in the suboxic environment of the NHCM sub-basin bottom waters due to their resistance to dissolution in marine waters. Considering the deposition conditions (oxygenation of the near-bottom zone) rather similar for both HCM parts, we associate the presence of aeolian hematite grains solely in the NHCM rocks with a more proximal position of the NHCM than the SHCM in relation to the Baltica continent during late Llandovery (Silurian). This conclusion agrees with some existing paleogeographic models. In addition to petromagnetic studies focused on the analysis of ferromagnets, AMS measurements were also carried out. The results indicate that the magnetic susceptibility is mainly governed by paramagnetic minerals, mostly phyllosilicates with small ferromagnetic contributions. Oblate AMS ellipsoid and distinct bedding parallel foliation indicate prevailing sedimentary-compactional alignment. Observed magnetic lineation of tectonic origin resulting from weak strain is related presumably to Variscian deformations.

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Dynamics of ostracod communities throughout the Mulde/ lundgreni event: contrasting patterns of species richness and palaeocommunity compositional change

Rinkevičiūtė

Stankevič

Radzevičius

et al. 2021

JGS

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The Mulde event was one of several significant turnover events during the Silurian. This event is mostly recognized in the fossil record of graptolites and conodonts, as well as stable carbon isotopic data. Therefore, the ostracods – a significant part of the benthos – comprise a new and important dimension in understanding this global geobiological episode. Here, a new ostracod and δ 13C high-resolution record from the upper Wenlock interval from a Gėluva-118 core (central Lithuania) are presented. Analyses revealed that the Mulde/lundgreni event had a negligible effect on the increasing alpha diversity trend during the mid- to upper Wenlock. A stratigraphically constrained time series analysis of ostracod paleocommunities revealed the presence of six temporally distinct compositional states/assemblages consistent with the Milankovitch scale (presumably eccentricity) 4th and 5th order sea level fluctuations. An analysis of ostracod recurrence plots revealed a sudden disruption during the Mulde/lundgreni event and a hierarchical pattern of intercalating compositionally stable states, a pattern expected under the “sloshing bucket” hypothesis of community change. A recurrence quantification analysis of subdominant species revealed that, in the aftermath of the Mulde event, there was a sudden transition to compositionally more stable communities, suggesting a strong ecosystem-level effect from this oceanic perturbation.Supplementary material:https://doi.org/10.6084/m9.figshare.c.5538271

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Graptolite turnover and δ13Corg excursion in the upper Wenlock shales (Silurian) of the Holy Cross Mountains (Poland)

Cited by 4 publications

References 80 publications

Dynamic ecophenotypy in the Silurian Monograptidae (Graptolithina)

Dynamic ecophenotypy in the Silurian Monograptidae (Graptolithina)

The Holy Cross Mountains (Poland) terranes palaeoposition and depositional environment in Silurian—new insights from rock magnetic studies

Dynamics of ostracod communities throughout the Mulde/ lundgreni event: contrasting patterns of species richness and palaeocommunity compositional change

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