The graptolite, conodont and sedimentary record through the late Ludlow Kozlowskii Event (Silurian) in the shale-dominated succession of Bohemia

AbstractThe shale-dominated hemipelagic succession exposed in the southwestern part of the Prague Synform preserves the most complete Ludfordian graptolite record so far encountered from peri-Gondwanan Europe. Four graptolite biozones – theNeocucullograptus inexpectatus,Nc. kozlowskii,Pseudomonoclimacis latilobus–Slovinograptus balticusandPristiograptus fragmentalisbiozones – are recognized in the middle and late Ludfordian, between theBohemograptus tenuisBiozone and the base of the Pridoli Series. Conodont occurrences are restricted to scattered limestone beds, but enable tentative integration of the graptolite and conodont biozonal schemes. Particular attention was paid to faunal and sedimentary changes and the carbon isotope record across the middle Ludfordian Kozlowskii extinction Event. The Kozlowskii Event caused the almost simultaneous extinction of graptolites with ventrally curved rhabdosomes. The generaBohemograptus,PolonograptusandNeocucullograptus, along withPseudomonoclimacis dalejensis, disappeared from the fossil record. The offshore conodont fauna recorded in the section was not strongly affected and similarly the pelagic orthocerids and nektonicCeratiocarispassed unaffected through the extinction interval. The abundant and widespread pelagic myodocopid ostracodEntomis, however, became extinct. The late Ludfordian graptolite recovery gave origin to a novel fauna of Pridoli type from taxa that emerged or just reappeared above the Kozlowskii crisis. In Všeradice and elsewhere in the Prague Synform, the recovery, manifested by the appearance ofPseudomonoclimacis latilobusandSlovinograptus balticus, closely postdates the end of the isotope excursion but pre-dates the first appearance of the conodont index ‘Ozarkodina’snajdri. Here the graptolite recovery was delayed relative to the recovery of the benthic fauna. A canalized intraformational limestone conglomerate corresponds with a gap in the sedimentary record above the Kozlowskii extinction and just below the graptolite recovery. The benthic faunas from the conglomerate matrix and pebbles permit correlation with the shallower part of the basin indicating a distinct fall in sea-level. The present data demonstrate the coincidence of the graptolite crisis with benthic faunal change and eustatic fall in sea-level manifested by facies change and the carbon isotope excursion.Polonograptus chlupacisp. nov., from theNc. kozlowskiiBiozone, is described and several other graptolite taxa are redescribed.

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Sequence stratigraphy, chemostratigraphy and facies analysis of Cambrian Series 2 – Series 3 boundary strata in northwestern Scotland

Geological Magazine ◽

10.1017/s0016756816000947 ◽

2016 ◽

Vol 155 (4) ◽

pp. 865-877 ◽

Cited By ~ 5

Author(s):

LUKE E. FAGGETTER ◽

PAUL B. WIGNALL ◽

SARA B. PRUSS ◽

YADONG SUN ◽

ROBERT J. RAINE ◽

...

Keyword(s):

Sea Level ◽

Sequence Stratigraphy ◽

Carbon Isotope ◽

Sea Level Changes ◽

Carbon Isotopic ◽

Carbonate Carbon ◽

Carbon Isotope Excursion ◽

Isotope Record ◽

Laurentian Margin ◽

Sequence Boundaries

AbstractGlobally, the Series 2 – Series 3 boundary of the Cambrian System coincides with a major carbon isotope excursion, sea-level changes and trilobite extinctions. Here we examine the sedimentology, sequence stratigraphy and carbon isotope record of this interval in the Cambrian strata (Durness Group) of NW Scotland. Carbonate carbon isotope data from the lower part of the Durness Group (Ghrudaidh Formation) show that the shallow-marine, Laurentian margin carbonates record two linked sea-level and carbon isotopic events. Whilst the carbon isotope excursions are not as pronounced as those expressed elsewhere, correlation with global records (Sauk I – Sauk II boundary andOlenellusbiostratigraphic constraint) identifies them as representing the local expression of the ROECE and DICE. The upper part of the ROECE is recorded in the basal Ghrudaidh Formation whilst the DICE is seen around 30m above the base of this unit. Both carbon isotope excursions co-occur with surfaces interpreted to record regressive–transgressive events that produced amalgamated sequence boundaries and ravinement/flooding surfaces overlain by conglomerates of reworked intraclasts. The ROECE has been linked with redlichiid and olenellid trilobite extinctions, but in NW Scotland,Olenellusis found after the negative peak of the carbon isotope excursion but before sequence boundary formation.

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

Geologica Carpathica ◽

10.2478/geoca-2019-0012 ◽

2019 ◽

Vol 70 (3) ◽

pp. 209-221

Author(s):

Sigitas Radzevičius ◽

Paweł Raczyński ◽

Marius Užomeckas ◽

Audrius Norkus ◽

Andrej Spiridonov

Keyword(s):

Sea Level ◽

Carbon Isotope ◽

Deep Water ◽

Benthic Fauna ◽

Northern Margin ◽

Holy Cross Mountains ◽

New Information ◽

Carbon Isotope Excursion ◽

Małopolska Block ◽

The Given

Abstract The mid–late Homerian Age of the Silurian Period was a time of intense changes in biota, oceanic chemistry, and sea level and is known as the lundgreni extinction (for the graptolite extinctions), the Mulde bioevent (for the conodont turnover event) or the Homerian carbon isotope excursion (CIE) probably related to glacially influenced climate perturbation. New information on this interval from the deep water sedimentary and graptolite succession of the Kielce Region (Holy Cross Mountains, Poland) of the northern margin of the Małopolska Block is presented here based on analysis of the Prągowiec Ravine section. The lundgreni–nilssoni graptolite biozones interval have been recognized there. This interval is composed by dark shales with very rare benthic fauna, which indicate the deep open-marine (pelagic) paleoenvironment. Ten samples were taken for the δ13Corg analysis from the lundgreni (2 samples), parvus (2 samples), praedeubeli (2 samples), praedeubeli–deubeli (1 sample), ludensis (2 samples) and nilssoni (1 sample) biozones. According to the δ13Corg results, the first positive δ13Corg excursion of the Mulde Bioevent is well recognized. The δ13Corg values rise from −30.7 – −30.1 ‰ in the lundgreni Biozone to −29.3 – −28.7 ‰ in the parvus Biozone and fall below −30 ‰ in the praedeubeli–deubeli interval. The second positive δ13Corg peak of the Mulde Event was not recognized in the Prągowiec Ravine. Based on the numerical comparisons using Raup-Crick metric of co-occurrences of graptolite species, the upper Homerian was characterized by significant between-biozone turnover of these taxa at the given locality.

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Carbon isotope (δ<sup>13</sup>C) excursions suggest times of major methane release during the last 14 kyr in Fram Strait, the deep-water gateway to the Arctic

Climate of the Past ◽

10.5194/cp-11-669-2015 ◽

2015 ◽

Vol 11 (4) ◽

pp. 669-685 ◽

Cited By ~ 23

Author(s):

C. Consolaro ◽

T. L. Rasmussen ◽

G. Panieri ◽

J. Mienert ◽

S. Bünz ◽

...

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Carbon Isotope ◽

Deep Water ◽

Planktonic Foraminifera ◽

Sediment Supply ◽

The Arctic ◽

Fram Strait ◽

The North ◽

Carbon Isotope Excursion

Abstract. We present results from a sediment core collected from a pockmark field on the Vestnesa Ridge (~ 80° N) in the eastern Fram Strait. This is the only deep-water gateway to the Arctic, and one of the northernmost marine gas hydrate provinces in the world. Eight 14C AMS dates reveal a detailed chronology for the last 14 ka BP. The δ 13C record measured on the benthonic foraminiferal species Cassidulina neoteretis shows two distinct intervals with negative values termed carbon isotope excursion (CIE I and CIE II, respectively). The values were as low as −4.37‰ in CIE I, correlating with the Bølling–Allerød interstadials, and as low as −3.41‰ in CIE II, correlating with the early Holocene. In the Bølling–Allerød interstadials, the planktonic foraminifera also show negative values, probably indicating secondary methane-derived authigenic precipitation affecting the foraminiferal shells. After a cleaning procedure designed to remove authigenic carbonate coatings on benthonic foraminiferal tests from this event, the 13C values are still negative (as low as −2.75‰). The CIE I and CIE II occurred during periods of ocean warming, sea-level rise and increased concentrations of methane (CH4) in the atmosphere. CIEs with similar timing have been reported from other areas in the North Atlantic, suggesting a regional event. The trigger mechanisms for such regional events remain to be determined. We speculate that sea-level rise and seabed loading due to high sediment supply in combination with increased seismic activity as a result of rapid deglaciation may have triggered the escape of significant amounts of methane to the seafloor and the water column above.

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The geochemistry of the late Cambrian carbonate in North China: the Steptoean Positive Carbon Isotope Excursion (SPICE) record suppressed in a coastal condition?

Geological Magazine ◽

10.1017/s0016756819000025 ◽

2019 ◽

Vol 156 (10) ◽

pp. 1805-1819 ◽

Cited By ~ 2

Author(s):

Jing Huang ◽

Yali Chen ◽

Xuelei Chu ◽

Tao Sun

Keyword(s):

Sea Level ◽

Carbon Isotope ◽

North China ◽

Coastal Environment ◽

Sedimentary Records ◽

Late Cambrian ◽

Geochemical Proxies ◽

Carbon Isotope Excursion ◽

Globally Distributed ◽

Shallow Coastal Environment

AbstractThe Steptoean Positive Carbon Isotope Excursion (SPICE) is globally distributed in late Cambrian sedimentary records but controversially heterogeneous in its magnitudes. Here we use multiple geochemical proxies to investigate the late Cambrian carbonates from the Tangwangzhai section in North China, which were deposited in a shallow coastal environment with three depositional sequences (S1–S3). Each sequence comprises a transgressive systems tract (TST) and a highstand systems tract (HST). The REE + Y and trace element records are consistent with the depositional condition and indicate that terrigenous influence was more significant in the TST than HST. δ13Ccarb and δ34SCAS are low in the TST relative to HST, consistent with the scenario that terrigenous inputs were profoundly aggressive to seawater by introducing 13C-depleted and 34S-depleted materials. Within the TST of S2, the SPICE excursion shows a scaled-down δ13Ccarb positive shift (∼1.7 ‰) relative to its general records (∼4–6 ‰); the corresponding δ34SCAS show no positive excursion. This ‘atypical’ SPICE record is attributed to enhanced 13C-depleted and 34S-depleted terrigenous influence during the TST, which would reduce the amplitude of δ13Ccarb excursion, and even obscure δ34SCAS excursion. Meanwhile the subaerial unconformity at the base of TST would also cause a partially missing and a ‘snapshot’ preservation. Our study confirms significant local influence to the SPICE records, and further supports the heterogeneity and low sulphate concentrations of the late Cambrian seawater, because of which the SPICE records may be vulnerable to specific depositional conditions (e.g. sea-level, terrigenous input).

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Carbon isotope record for the onset of the Lomagundi carbon isotope excursion in the Great Lakes area, North America

Precambrian Research ◽

10.1016/j.precamres.2006.03.008 ◽

2006 ◽

Vol 148 (1-2) ◽

pp. 145-180 ◽

Cited By ~ 87

Author(s):

A. Bekker ◽

J.A. Karhu ◽

A.J. Kaufman

Keyword(s):

North America ◽

Great Lakes ◽

Carbon Isotope ◽

Carbon Isotope Excursion ◽

Isotope Record ◽

Area North

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New Chronostratigraphic Constraints on the Lower Jurassic Pliensbachian–Toarcian Boundary at Chacay Melehue (Neuquén Basin, Argentina)

10.21203/rs.3.rs-1042905/v1 ◽

2021 ◽

Author(s):

Aisha H. Al-Suwaidi ◽

Micha Ruhl ◽

Hugh C. Jenkyns ◽

Susana E. Damborenea ◽

Miguel O. Manceñido ◽

...

Keyword(s):

High Resolution ◽

Carbon Isotope ◽

Volcanic Ash ◽

Lower Jurassic ◽

Zircon Geochronology ◽

Organic Carbon Isotope ◽

Carbon Isotope Excursion ◽

Isotope Record ◽

Age Model ◽

Zonal Boundary

Abstract The Pliensbachian–Toarcian boundary interval is characterized by a ~3‰ negative carbon-isotope excursion (CIE) in organic and inorganic marine and terrestrial archives from sections in Europe, such as Peniche (Portugal) and Hawsker Bottoms, Yorkshire (UK). A new high-resolution organic-carbon isotope record, illustrating the same chemostratigraphic feature, is presented from the Southern Hemisphere Arroyo Chacay Melehue section, Chos Malal, Argentina, corroborating the global significance of this disturbance to the carbon cycle. The negative carbon-isotope excursion, mercury and organic-matter enrichment is accompanied by high-resolution ammonite and nannofossil biostratigraphy together with U-Pb CA-ID-TIMS geochronology derived from intercalated volcanic ash beds. A new age of ~183.71 ± 0.40/-0.51 Ma for the Pliensbachian–Toarcian boundary, and 182.77 +0.11/-0.21 for the tenuicostatum–serpentinum zonal boundary, is assigned based on high-precision U-Pb zircon geochronology and a Bayesian Markov chain Monte Carlo (MCMC) stratigraphic age model.

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Molecular and isotopic evidence reveals the end-Triassic carbon isotope excursion is not from massive exogenous light carbon

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1917661117 ◽

2020 ◽

Vol 117 (48) ◽

pp. 30171-30178

Author(s):

Calum P. Fox ◽

Xingqian Cui ◽

Jessica H. Whiteside ◽

Paul E. Olsen ◽

Roger E. Summons ◽

...

Keyword(s):

Sea Level ◽

Carbon Isotope ◽

Microbial Mats ◽

Type Locality ◽

Marine Biota ◽

Marine Strata ◽

Carbon Isotopic ◽

Carbon Isotope Excursion ◽

Global Extinction ◽

Extinction Events

The negative organic carbon isotope excursion (CIE) associated with the end-Triassic mass extinction (ETE) is conventionally interpreted as the result of a massive flux of isotopically light carbon from exogenous sources into the atmosphere (e.g., thermogenic methane and/or methane clathrate dissociation linked to the Central Atlantic Magmatic Province [CAMP]). Instead, we demonstrate that at its type locality in the Bristol Channel Basin (UK), the CIE was caused by a marine to nonmarine transition resulting from an abrupt relative sea level drop. Our biomarker and compound-specific carbon isotopic data show that the emergence of microbial mats, influenced by an influx of fresh to brackish water, provided isotopically light carbon to both organic and inorganic carbon pools in centimeter-scale water depths, leading to the negative CIE. Thus, the iconic CIE and the disappearance of marine biota at the type locality are the result of local environmental change and do not mark either the global extinction event or input of exogenous light carbon into the atmosphere. Instead, the main extinction phase occurs slightly later in marine strata, where it is coeval with terrestrial extinctions and ocean acidification driven by CAMP-induced increases inPco2; these effects should not be conflated with the CIE. An abrupt sea-level fall observed in the Central European basins reflects the tectonic consequences of the initial CAMP emplacement, with broad implications for all extinction events related to large igneous provinces.

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Carbon isotope (δ13Ccarb) and facies variability at the Wenlock–Ludlow boundary (Silurian) of the Midland Platform, UK

Canadian Journal of Earth Sciences ◽

10.1139/cjes-2015-0194 ◽

2016 ◽

Vol 53 (7) ◽

pp. 725-730 ◽

Cited By ~ 5

Author(s):

John A. Blain ◽

David C. Ray ◽

James R. Wheeley

Keyword(s):

High Resolution ◽

Sea Level Rise ◽

Sea Level ◽

Carbon Isotope ◽

Carbonate Platform ◽

Temporal Variations ◽

Spatial Variations ◽

Sea Level Fluctuations ◽

Depositional Settings ◽

Carbon Isotope Excursion

The Wenlock–Ludlow series boundary (Silurian) has been recognized as a time of pronounced sea-level rise and the end of a globally recognized Late Homerian Stage (Mulde) positive carbon isotope excursion (CIE). However, the precise timing and synchronicity of the end of the excursion with respect to the Wenlock–Ludlow boundary is debated. Within the type Wenlock and Ludlow areas (UK), high-resolution δ13Ccarb isotope data are presented across the Wenlock–Ludlow boundary, and within a range of carbonate platform settings. Correlation between sections and depositional settings has been based upon the characteristics of high-order sea-level fluctuations (parasequences). Comparisons between parasequence-bounded δ13Ccarb values reveal clear spatial variations, with lighter values recorded from more distal settings and heavier values from shallower settings. Temporal variations in the δ13Ccarb values are also documented and appear to reflect local variations in carbonate provenance and productivity in response to sea-level rise. While δ13Ccarb values converge in all sections towards the Wenlock–Ludlow boundary, the apparent end of the Mulde CIE appears diachronous and is progressively older within more distal settings.

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A carbon-isotope perturbation at the Pliensbachian–Toarcian boundary: evidence from the Lias Group, NE England

Geological Magazine ◽

10.1017/s0016756809990458 ◽

2009 ◽

Vol 147 (2) ◽

pp. 181-192 ◽

Cited By ~ 109

Author(s):

KATE LITTLER ◽

STEPHEN P. HESSELBO ◽

HUGH C. JENKYNS

Keyword(s):

Organic Matter ◽

Carbon Isotope ◽

Similar Pattern ◽

Oceanic Anoxic Event ◽

European Section ◽

Extinction Event ◽

Anoxic Event ◽

Global Extinction ◽

Isotope Record ◽

Bulk Organic Matter

AbstractA perturbation in the carbon-isotope record at the time of the Pliensbachian–Toarcian boundary (~ 184 Ma) in the Early Jurassic is reported, based on new data from Yorkshire, England. Two sharp δ13Corg negative excursions, each with a magnitude of ~ −2.5 ‰ and reaching minimum values of −28.5 ‰, are recorded in the bulk organic-matter record in sediments of latest Pliensbachian to earliest Toarcian age. A similar pattern of negative carbon-isotope excursions has been observed at the stage boundary in the SW European section at Peniche, Portugal in δ13Ccarbonate, δ13Cwood and δ13Cbrachiopod records. The isotopic excursion is of interest when considering the genesis and development of the later Toarcian Oceanic Anoxic Event (OAE), as well as the second-order global extinction event that spans the stage boundary. Furthermore, the isotope excursion potentially provides a chemostratigraphic marker for recognition of the stage boundary, which is currently achieved on the basis of different ammonite faunas in the NW European and Tethyan realms.

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