Manifestation of the Late Famennian Dasberg Event in the shelf-batial transition (Pai-Khoi sequences)

Research subject. Regional manifestations of the Dasberg eustatic event in the shelf and bathyal Pai-Khoi successions. The event appears in the Lower-Middle expansa zones interval (Upper Devonian, Famennian).Aim. To evaluate the manifestations of the event in the realm of transition from the shallow-water shoal succession of the Pai-Khoi carbonate parautokhtone towards the deep-water (bathyal) successions of the Kara shale allokhtone.Materials and methods. A number of successions comprising different facies and located in different parts of Pai-Khoi were studied: the Silova-Yakha River section and Tal’beyshor Creek section (south-western Pai-Khoi), the Lymbad’yakha section and the Peschanaya River section (northern Pai-Khoi). The interpretation of facies and the reconstruction of transgression-regression couplets were conducted based on the previously developed models of shoal and bathyal sedimentation. The stratigraphic framework comprised data on conodonts, transgression acmes, and carbonate carbon isotopic record.Results. The Pai-Khoi successions comprising Lower–Middle expansa zones demonstrate four transgression-regression cycles. The transgression acme of the third cycle marks the Dasberg eustatic event. The absence of anoxia is characteristic of this event in the region under consideration. The carbonate carbon isotope record of the Silova-Yakha River section shows a structure similar to that of North American successions. Variations in δ13Cкарб were likely to be caused by climate changes and perturbations of the global oceanic circulation.Conclusions. The stratigraphic interval comprising Lower–Middle expansa or Lower–Upper expansa (expansa s. l.) zones is detected clearly in different facies. A more detailed subdivision and correlation in the region under consideration is possible on the basis of evaluating manifestations of the Dasberg eustatic event: a characteristic eustatic succession and variations of the carbonate carbon isotopic composition.

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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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Carbon and oxygen isotopic composition of Lower to Middle Cambrian sediments at Taijiang, Guizhou Province, China

Geological Magazine ◽

10.1017/s0016756805001202 ◽

2005 ◽

Vol 142 (6) ◽

pp. 723-733 ◽

Cited By ~ 27

Author(s):

QING-JUN GUO ◽

HARALD STRAUSS ◽

CONG-QIANG LIU ◽

YUAN-LONG ZHAO ◽

DAO-HUI PI ◽

...

Keyword(s):

Organic Matter ◽

Isotopic Composition ◽

Southern China ◽

Carbon Isotopic Composition ◽

Bacterial Biomass ◽

Oxygen Isotopic Composition ◽

Guizhou Province ◽

Middle Cambrian ◽

Carbon Isotopic ◽

Carbonate Carbon

Secular variations in the carbon isotopic composition of organic and carbonate carbon characterize the Lower to Middle Cambrian transition that is exposed on the Yangtze Platform at Taijiang, Guizhou Province, southern China. δ13C values for organic matter range between −33.4 and −26.5‰. The carbon isotopic composition for carbonate carbon fluctuates between −2.7 and +3.1‰. A progressive decrease in the isotopic difference (Δδ) between these two isotope records reflects a decrease in the proportional contribution of bacterial biomass to the total sedimentary organic matter. In general, the observed changes are interpreted to reflect primary depositional values, notably variations in the burial rates of organic matter. These, in turn, are linked to biological changes across the Lower to Middle Cambrian transition. No distinct shift in the carbon isotopic composition marks the proposed Lower–Middle Cambrian boundary.

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Isotope-geochemical characteristics of Wenlock carbonate and terrigenous-carbonate deposits of the Subpolar Urals and the southern part of the Chernyshev ridge

LITOSFERA ◽

10.24930/1681-9004-2021-21-6-829-848 ◽

2021 ◽

Vol 21 (6) ◽

pp. 829-848

Author(s):

D. N. Shebolkin

Keyword(s):

Isotopic Composition ◽

Isotope Analysis ◽

Carbon Isotopic Composition ◽

Time Intervals ◽

Subpolar Urals ◽

Carbon Isotopic ◽

Carbonate Carbon ◽

Wide Range ◽

Chernyshev Ridge ◽

Oxygen Isotopic

Research subject. Wenlock deposits in the Subpolar Urals and southern part of the Chernyshev Ridge. Materials and methods. Carbonate and terrigenous-carbonate rock samples from sections of the Subpolar Urals (outcrops 212, 217) and the southern part of the Chernyshev Ridge (outcrop 479) were studied by isotope analysis of carbonate carbon and oxygen.Results. The isotopic composition of the studied sections varies across a wide range of δ13С (–6.4…–0.05‰) and δ18O (20.0–26.9‰). Therefore, three time intervals characterized by distinctive isotopic characteristics can be distinguished, roughly corresponding to early Sheinwoodian (I), late Sheinwoodian (II) and Homerian (III). Interval I is characterized exclusively by the rocks of outcrop 479 with δ13С (–3.6…–3.0‰) and δ18O (22.4–23.6‰). In Interval II, the average values of isotopic characteristics of outcrop 479 indicate a tendency to weighting carbon (–5.5…–3.5‰) and somewhat heavier oxygen (23.2–25.2‰) isotopes. In outcrop 212, the average isotopic values for carbon and oxygen vary from –2.9 to –1.3‰ and from 21.9 to 24.3‰, respectively. In outcrop 217, the average values are δ13C (–1.8…–0.8‰) and δ18O (22.4–25.4‰). In Interval III, the average values of carbon isotopic composition in outcrop 479 are becoming heavier from –2.5 to –0.7‰. In outcrop 212, the isotopic values of oxygen (21.9–23.1‰) and carbon (–4.9…–2.5‰) tend to become weighting; however, in outcrop 217, the average isotopic values of δ13C (–1.9…–0.5‰) and δ18O (22.3–24.5‰) remain constant. The conducted litho-facial studies showed that the weighting carbon isotopic composition ranging from –6.4…to –3.0‰ is associated with an increase in microbial activity in sediments, the manifestation of vadose-phreatic conditions, and the intake of light carbon dioxide with a flow of terrigenous material from the earth. In the latter case, oxygen isotopic values are also the most lightweight (20.0–23.0‰).Conclusions. The obtained isotopic characteristics of the Wenlock rocks under study indicate the expedience of identifying three time intervals and their correlation with paleogeographic reconstructions of Wenlockian sedimentation in the Timan-northern Ural region.

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Stratigraphy around the Cretaceous-Paleogene boundary in sediment cores from the Lord Howe Rise, Southwest Pacific

Geological Society of America Bulletin ◽

10.1130/b36112.1 ◽

2021 ◽

Author(s):

Junichiro Kuroda ◽

Kyoko Hagino ◽

Yoichi Usui ◽

Paul R. Bown ◽

Kan-Hsi Hsiung ◽

...

Keyword(s):

Isotopic Composition ◽

Sediment Cores ◽

Carbon Isotopic Composition ◽

Time Interval ◽

Calcareous Nannofossils ◽

Impact Event ◽

Southwest Pacific ◽

Carbon Isotopic ◽

Carbonate Carbon ◽

Chicxulub Impact

During Deep Sea Drilling Project (DSDP) Leg 21, Cenozoic and latest Cretaceous sediments were recovered at Site 208 on the Lord Howe Rise, Southwest Pacific. We provide new biostratigraphic, magnetostratigraphic and chemostratigraphic data from Site 208 to constrain the stratigraphy around the Cretaceous-Paleogene (K-Pg) boundary and to determine the depth of the K-Pg boundary more precisely. Biostratigraphic data from calcareous nannofossils indicate a near-continuous succession of sediments from the mid-Maastrichtian (Late Cretaceous) to lowermost Thanetian (Paleocene) at depths of 540−590 m below seafloor (mbsf). The biostratigraphic data suggest that the K-Pg boundary corresponds to a siliceous claystone at the base of an interval of silicified sediments (576.0−576.8 mbsf). Carbonate carbon isotopic composition (δ13Ccarb) reveals a negative shift across this interval, which is consistent with global patterns of δ13C across the K-Pg boundary. Osmium concentration and Os isotopic composition (187Os/188Os) can also be used to identify the K-Pg boundary interval, as it is marked by a peak in Os concentration and a drop in 187Os/188Os values to 0.12−0.15, both of which are the result of the Chicxulub impact event. Our 187Os/188Os data show trends similar to those of coeval global seawater with the lowest value of 0.12−0.16 in the siliceous claystone (576.8 mbsf). However, the concentration of Os is low (<80 pg g−1) in this sample, which suggests that this siliceous claystone was deposited around the K-Pg boundary but may not include the boundary itself. Although the sedimentary record across the K-Pg interval at Site 208 may not be completely continuous, it nevertheless captures a time interval that is close to the Chicxulub impact event.

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