scholarly journals Carbon isotopes, stratigraphy, and environmental change: the Middle–Upper Cambrian Positive Excursion (SPICE) in Port au Port Group, western Newfoundland, Canada

2018 ◽  
Vol 55 (11) ◽  
pp. 1209-1222 ◽  
Author(s):  
Rosalia Barili ◽  
Joyce Elaine Neilson ◽  
Alexander Thomas Brasier ◽  
Karin Goldberg ◽  
Tatiana Pastro Bardola ◽  
...  
Keyword(s):  
North America ◽  
Environmental Change ◽  
Carbon Isotope ◽  
Carbon Isotopes ◽  
Carbonate Rocks ◽  
Isotopic Signature ◽  
Upper Cambrian ◽  
Carbon Isotopic ◽  
Carbon Isotope Excursion ◽  
Diagenetic Environment

In many basins, Upper Cambrian carbonate successions display intervals with a positive carbon isotope excursion (CIE) of up to +5‰. In North America, this marks the boundary between the Sauk II–III super-sequences. A Steptoean positive carbon isotope excursion (SPICE) locality previously identified in the Port au Port peninsula, western Newfoundland, has been revisited and an additional potential SPICE locality found. In both locations, a CIE is found to be associated with a prominent bioherm and sandstone layer within a sequence of carbonate rocks. At March Point columnar stromatolites occur, whereas at Felix Cove thrombolites can be seen. In the latter, the sandstone immediately overlies the thrombolites coincident with the CIE, whereas at March Point a dolomitized grainstone occurs above the stromatolites. The sandstone at this locality post-dates the CIE. Although lower than the SPICE in some localities, a positive CIE is present in both sections: March Point (+1.1‰) and Felix Cove (+1.8‰). Additionally, δ13Corg rises from −30.0‰ to −22.0‰ at March Point and from −27‰ to −24.0‰ at Felix Cove and, in accordance with previously published work, we suggest that this could be the SPICE. Comparison of the stratigraphy and petrography between the two localities suggest that both depositional and diagenetic factors could have influenced the nature of the interpreted SPICE in Newfoundland. It is also possible that the local carbon isotopic signature may have been influenced by a semi-restricted depositional and early diagenetic environment related to the paleogeographic configuration rather than the global marine excursion.

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.

Dynamics of a stepped carbon-isotope excursion: Ultra high-resolution study of Early Toarcian environmental change

2012 ◽  
Vol 319-320 ◽  
pp. 45-54 ◽  
Author(s):  
Michaël Hermoso ◽  
Fabrice Minoletti ◽  
Rosalind E.M. Rickaby ◽  
Stephen P. Hesselbo ◽  
François Baudin ◽  
...  
Keyword(s):  
High Resolution ◽  
Environmental Change ◽  
Carbon Isotope ◽  
Carbon Isotope Excursion ◽  
Resolution Study

Extending the record of the Lomagundi–Jatuli carbon isotope excursion in the Labrador Trough, Canada

2020 ◽  
Vol 57 (9) ◽  
pp. 1089-1102
Author(s):  
Malcolm S.W. Hodgskiss ◽  
Kelsey G. Lamothe ◽  
Galen P. Halverson ◽  
Erik A. Sperling
Keyword(s):  
High Resolution ◽  
Water Column ◽  
Carbon Isotope ◽  
Carbon Isotopes ◽  
Large Range ◽  
Authigenic Carbonate ◽  
Elemental Ratios ◽  
Carbonate Carbon ◽  
Carbon Isotope Excursion ◽  
Isotope Analyses

The Labrador Trough in northern Québec and Labrador is a 900 km long Rhyacian–Orosirian orogenic belt containing mixed sedimentary–volcanic successions. Despite having been studied intensively since the 1940s, relatively few chemostratigraphic studies have been conducted. To improve our understanding of the Labrador Trough in the context of Earth history, and better constrain the local record of the Lomagundi–Jatuli carbon isotope excursion, high-resolution sampling and carbon isotope analyses of the Le Fer and Denault formations were conducted. Carbonate carbon isotopes (δ13C) in the Le Fer Formation record a large range in values from −4.4‰ to +6.9‰. This large range is likely attributable to a combination of post-depositional alteration and variable abundance of authigenic carbonate minerals; elemental ratios suggest that the most 13C-enriched samples reflect the composition of the water column at the time of deposition. Cumulatively, these data suggest that the Lomagundi–Jatuli Excursion was ongoing during deposition of the Le Fer Formation, approximately 2 km higher in the stratigraphy than previously recognised. However, the possibility of a post-Lomagundi–Jatuli Excursion carbon isotope event cannot conclusively be ruled out. The directly overlying Denault Formation records a range in δ13C values, from −0.5‰ to +4.3‰, suggesting that it was deposited after the conclusion of the Lomagundi–Jatuli Excursion and that the contact between the Le Fer and Denault formations occurred sometime during the transition out of the Lomagundi–Jatuli Excursion, ca. 2106 to 2057 Ma.

scholarly journals Record of Early Toarcian carbon cycle perturbations in a nearshore environment: the Bascharage section (easternmost Paris Basin)

2014 ◽  
Vol 6 (1) ◽  
pp. 1073-1100 ◽  
Author(s):  
M. Hermoso ◽  
D. Delsate ◽  
F. Baudin ◽  
L. Le Callonnec ◽  
F. Minoletti ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Carbon Isotope ◽  
Isotopic Signature ◽  
Oxygen Isotopic Composition ◽  
Black Shales ◽  
Positive Trend ◽  
Oceanic Anoxic Event ◽  
Carbon Isotope Excursion ◽  
Oxygen Isotopic ◽  
Global Nature

Abstract. In order to understand the significance of worldwide deposition of black shale facies in the Early Toarcian (~ 183 Ma), considerable attention has been drawn to this Early Jurassic sub-Stage over the last three decades. The discovery of a pronounced negative carbon isotope excursion (CIE) within the black shales disrupting the generally positive trend in carbon isotopes has stimulated many studies, particularly with a view to establish the local vs. global nature of this major geochemical phenomenon. Here we document the sedimentological and chemostratigraphic evolution of a proximal environment in the Luxembourgian sedimentary area, the so-called Gutland. At Bascharage, Lower Toarcian sediments record the isotopic signature of the Early Toarcian Oceanic Anoxic Event (OAE) by a pronounced positive trend that testifies for widespread anoxia. The expression of the carbon isotope perturbation in this section however, is unusual compared to adjacent NW European sections. A first −7 ‰ negative CIE, whose onset is recorded at the top of the tenuicostatum zone, can be assigned to the well-documented and potentially global T-CIE with confidence using the well-constrained ammonite biostratigraphic framework for this section. In this interval, facies contain only a limited amount of carbonate as a result of intense detrital supply in such a proximal and shallow environment. Stratigraphically higher in the section, the serpentinum zone records a subsequent CIE (−6 ‰) that is expressed by four negative steps, each being accompanied by positive shifts in the oxygen isotopic composition of carbonate. The preservation state of coccoliths and calcareous dinoflagellates in the second CIE is excellent and comparable to that observed in under- and overlying strata, so this cannot be an artefact of diagenesis. Considering the nature of this record, and the lack of such a pronounced event in the serpentinum zone in coeval sections in Europe, we hypothesise that this second CIE was caused by local factors. The geochemical record of carbonate with a relatively light carbon and relatively heavy oxygen isotopic composition is compatible with the so-called Küspert model, by which a CIE can be explained by an influx of 12C-rich and cold waters due to upwelling bottom water masses. With the ongoing effort of high-resolution studies of the Meso-Cenozoic eras, further CIEs are likely to be found, but it has to be remembered that their (global) significance can only be determined via an integrated sedimentological, mineralogical, micropalaeontological and geochemical approach.

DECIPHERING THE RECORD OF BIOLOGIC AND ENVIRONMENTAL CHANGE DURING THE LATER CAMBRIAN STEPTOEAN POSITIVE CARBON ISOTOPE EXCURSION

2017 ◽  
Author(s):  
Benjamin C. Gill ◽  
◽  
Matthew A. LeRoy ◽  
Angela Gerhardt ◽  
Theodore R. Them ◽  
...  
Keyword(s):  
Environmental Change ◽  
Carbon Isotope ◽  
Carbon Isotope Excursion
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