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

2016 ◽  
Vol 155 (4) ◽  
pp. 865-877 ◽  
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.

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

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.

Katian (Upper Ordovician) carbon isotope chemostratigraphy in the Neixiang area, central China: implications for intercontinental correlation

2019 ◽  
Vol 156 (12) ◽  
pp. 2053-2066 ◽  
Author(s):  
Xiuchun Jing ◽  
Svend Stouge ◽  
Yufeng Tian ◽  
Xunlian Wang ◽  
Hongrui Zhou
Keyword(s):  
Sea Level ◽  
Carbon Isotope ◽  
Central China ◽  
Sea Level Changes ◽  
Isotopic Data ◽  
Upper Ordovician ◽  
Long Distance ◽  
Carbon Isotopic ◽  
The North ◽  
Main Driver

AbstractThe Katian (Upper Ordovician) Shiyanhe Formation at the Sigang section, Neixiang area, Henan Province, central China, has been investigated for carbon isotope (δ13Ccarb) chemostratigraphy. The carbon isotopic data document signal between the two major Ordovician positive shifts in δ13C, the early Katian Guttenberg and the Hirnantian excursions. The Kope (Ka1/2), Fairview (Ka2/3), Waynesville (Ka3/4), Whitewater (Ka4) excursions and a doubtful Elkhorn (Ka4) excursion are identified herein. The continuous and well-defined conodont zonal succession of the Sigang section provides a secure biostratigraphic framework for the mid-late Katian carbon isotope chemostratigraphy in China. Correlation between carbon-isotope data curve and the relative sea-level changes shows no clear correspondence, and hence the sea-level change is probably not the main driver of δ13C excursions during the Katian. Intercontinentally, the mid–late Katian carbon isotope excursions, identified mainly in the North American and Baltoscandian successions, are useful for improving long-distance stratigraphic correlations. This further suggests that these excursions represent global perturbations in the carbon cycle.

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

2011 ◽  
Vol 149 (3) ◽  
pp. 507-531 ◽  
Author(s):  
ŠTĚPÁN MANDA ◽  
PETR ŠTORCH ◽  
LADISLAV SLAVÍK ◽  
JIŘÍ FRÝDA ◽  
JIŘÍ KŘÍŽ ◽  
...  
Keyword(s):  
Sea Level ◽  
Carbon Isotope ◽  
Benthic Fauna ◽  
Sedimentary Record ◽  
Faunal Change ◽  
Carbon Isotope Excursion ◽  
Extinction Event ◽  
Isotope Record ◽  
Facies Change ◽  
Conodont Fauna

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.

scholarly journals 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

2015 ◽  
Vol 11 (4) ◽  
pp. 669-685 ◽  
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.

TECTONOSTRATIGRAPHIC EVOLUTION OF THE SOUTH-EAST GIPPSLAND BASIN

1991 ◽  
Vol 31 (1) ◽  
pp. 116 ◽  
Author(s):  
B.A. Duff ◽  
N.G. Groilman ◽  
D.J. Mason ◽  
J.M. Questiaux ◽  
D.S. Ormerod ◽  
...  
Keyword(s):  
Sea Level ◽  
Normal Faults ◽  
Plate Boundaries ◽  
Sea Level Changes ◽  
The South ◽  
Seismic Sequences ◽  
Controlled Deposition ◽  
Global Sea Level ◽  
Sequence Boundaries ◽  
Gippsland Basin

Evolution of the south-east Gippsland Basin since ca. 96 Ma has been governed by the interaction of three distinct processes:re-organisation of regional plate boundaries at 96, 80 and 50 Ma, registered as major angular unconformities or megasequence boundaries;intra-basin response of cover to basement-controlled deformational phases, registered as the sequence boundaries within these megasequences; andthe more subtle balance between regressive sedimentation associated with these phases and the transgressive deposition associated with longer-term eustatic sea level rises.The Golden Beach Megasequence (seismic sequences UK1 and UK2) accumulated syntectonically in an extensional setting characterised by an orthogonal array of north-northeast trending transfer faults and associated normal faults. Major compressional tectonism at ca. 80 Ma terminated this regime, initiating a modified mosaic of stratotectonic domains which controlled deposition of the Latrobe Megasequence.The seismic sequences within this megasequence display two types of cyclicity distinguishing intra-Campanian to Top Maastrichtian sequences (UK3-UK5) from early Tertiary sequences (PL1, PL2 and EO1). The sequence boundaries are considered to be the expression of recurrent compressive deformational phases. They are demonstrable as angular unconformities in transpressional and pull-apart structures in domains within which deformation was focused over the older extensional grain.The ca. 50 Ma Top Latrobe megasequence boundary appears to mark the transition from a basement-coupled deformational style characteristic of the Latrobe Megasequence, to a basement-decoupled inversion style of deformation during deposition of the Seaspray Megasequence (post-50 Ma).Seismic sequence boundaries, at least within basins such as the Gippsland, are therefore the stratigraphic expression of deformational phases rather than signatures of global sea-level changes. Eustacy is not invariably a shorter-term process than basin tectonism, nor is it the sole or main determinant of depositional style.

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

2019 ◽  
Vol 156 (10) ◽  
pp. 1805-1819 ◽  
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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