The Ordovician Period

Goldman, Daniel; Sadler, Peter M.; Leslie, Stephen A.; Melchin, Michael J.; Agterberg, Frits; Gradstein, Felix M.

doi:10.1016/b978-0-12-824360-2.00020-6

Cited by 86 publications

(56 citation statements)

References 244 publications

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“…Integrating the biostratigraphic (conodont, graptolite, and chitinozoan) and chemostratigraphic ( 87 Sr/ 86 Sr and δ 13 C carb isotope) constraints with the numerical Ordovician 2012 Geological Time Scale (Cooper and Sadler, 2012; see the Supplemental Material), McLaughlin et al (2016) inferred that the entire ∼1100-m-thick Vauréal Formation represents a few million years, implying that the 5-10 m cycles each represents a few tens of thousands of years. This interpretation is also consistent with the 2020 Ordovician Geological Time Scale (Goldman et al, 2020). These independent time constraints exclude eccentricity time scales for the 5-10 m cycles.…”

Section: Cyclostratigraphic Analysissupporting

confidence: 84%

Precession-driven climate cycles and time scale prior to the Hirnantian glacial maximum

Sinnesael

McLaughlin

Desrochers

et al. 2021

Geology

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Paleozoic astrochronologies are limited by uncertainties in past astronomical configurations and the availability of complete stratigraphic sections with precise, independent age control. We show it is possible to reconstruct a robust Paleozoic ~104-yr-resolution astrochronology in the well-preserved and thick Upper Ordovician reference record of Anticosti Island (Canada). The clear imprint of astronomical cycles, including ~18 k.y. precession, potential obliquity, and short and long eccentricity, constrains the entire Vauréal Formation (~1 km thick) to only ~3 m.y. in total, representing ~10 times higher accumulation rates than previously suggested. This ~104 yr resolution represents an order of magnitude increase in the current standard temporal resolution for the Katian and even allows for the detection of sub-Milankovitch climate-scale variability. The loss of a clear precession signal in the uppermost Vauréal Formation might be related to contemporaneous global cooling prior to the Hirnantian glacial maximum as indicated by the δ18O record. Complementary to the study of cyclostratigraphy of longer and often simplified records, it is important to recognize stratigraphic hiatuses and complexities on the ~104 yr scale to achieve robust sub-eccentricity-scale Paleozoic astrochronologies.

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Section: Cyclostratigraphic Analysissupporting

confidence: 84%

Precession-driven climate cycles and time scale prior to the Hirnantian glacial maximum

Sinnesael

McLaughlin

Desrochers

et al. 2021

Geology

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“…The successions are dated based on conodont biostratigraphy [61] and occur below the Kinnekulle K-bentonite, itself dated using U/Pb zircons to 454.41 ± 0.17 Ma [62,63], confirming a Sandbian age. The spore was sampled from 48.2m, corresponding to the Baltoniodus variabilis biozone, with a maximum age corresponding to the top of the Sandbian, 458.18 ± 0.7 Ma [61,64].…”

Section: C_23: Bryophyta: Hypnanae -Brynanaementioning

confidence: 99%

Divergent evolutionary trajectories of bryophytes and tracheophytes from a complex common ancestor of land plants

Harris

Clark

Schrempf

et al. 2021

Preprint

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The origin of plants and their colonization of land resulted in the transformation of the terrestrial environment. Here we investigate the evolution of the land plants (embryophytes) and their two main lineages, the tracheophytes (vascular plants) and bryophytes (non-vascular plants). We used new fossil calibrations, relative lineage dating implied by horizontal gene transfer, and new phylogenomic methods for mapping gene family origins. Distinct rooting strategies resolve tracheophytes and bryophytes as monophyletic sister groups that diverged during the Cambrian, 515-494 Ma. The embryophyte stem is characterised by a burst of gene innovation, while bryophytes subsequently experienced a no less dramatic episode of reductive genome evolution in which they lost genes associated with the elaboration of vasculature and the stomatal complex. Overall, our analyses confirm that extant tracheophytes and bryophytes are both highly derived; as a result, understanding the origin of land plants requires tracing character evolution across the diversity of modern lineages.

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“…It can be concluded that the stratigraphic distribution of Vikisphaera spans at least two conodont zones within the Kunda Regional Stage, lower Darriwilian. According to recent estimates, the Kunda Regional Stage corresponds to ca 3-5 Ma (Lindskog et al 2017;Goldman et al 2020), suggesting that the known temporal range of Vikisphaera is a few million years. Such a restricted stratigraphic distribution implies its biostratigraphic utility.…”

Section: Notes On the Distributionmentioning

confidence: 99%

Possible metazoan egg fossils from the Darriwilian (Middle Ordovician) of Baltoscandia

Hints¹,

Liang²,

Nõlvak³

2021

EJES

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The Ordovician Period

Cited by 86 publications

References 244 publications

Precession-driven climate cycles and time scale prior to the Hirnantian glacial maximum

Precession-driven climate cycles and time scale prior to the Hirnantian glacial maximum

Divergent evolutionary trajectories of bryophytes and tracheophytes from a complex common ancestor of land plants

Possible metazoan egg fossils from the Darriwilian (Middle Ordovician) of Baltoscandia

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