Carbon cycle perturbation and mercury anomalies in terrestrial Oceanic Anoxic Event 1b from Jiuquan Basin, NW China

2022 ◽  
pp. SP521-2021-149
Author(s):  
Xiangdong Zhao ◽  
Daran Zheng ◽  
He Wang ◽  
Yanan Fang ◽  
Naihua Xue ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Carbon Cycle ◽  
Central Italy ◽  
Lacustrine Sediments ◽  
Terrestrial Ecosystem ◽  
Western Tethys ◽  
Oceanic Anoxic Event ◽  
Anoxic Event ◽  
Carbon Reservoir ◽  
Global Carbon

AbstractThe Oceanic Anoxic Event (OAE) 1b is well documented in western Tethys, however, records in Eurasia are still lacking. Here, we carried out high-resolution organic carbon isotope (δ13Corg), total organic carbon (TOC) contents and mercury (Hg) concentrations analysis of the lacustrine sediments from the Xiagou and Zhonggou formations in the Hanxiagou section, Jiuquan Basin, northwestern China. The lacustrine δ13Corg curve presents three stages of negative excursions above the basalt layer dated at 112.4 ± 0.3 Ma in the lowermost Zhonggou Formation. The three negative δ13Corg excursions, well corresponded with the three subevents (Kilian, Paquier, and Leenhardt) of the OAE1b in Poggio le Guaine (central Italy), Vocontian Basin (SE France) and St Rosa Canyon (NE Mexico) sections, supporting the record of the terrestrial OAE 1b in the Jiuquan Basin. Five mercury enrichment (ME) intervals in Hg/TOC ratios were recognized, indicating that the pulsed volcanism from the southern Kerguelen Plateau likely triggered the OAE 1b. However, the decoupling between NIE shifts and mercury enrichments signifying other carbon reservoir (with no link to mercury) probably contributed to the global carbon cycle perturbation during the OAE 1b period. Our results provide direct evidence to link the OAE 1b and terrestrial ecosystem in the Eurasia.

scholarly journals Ocean warming affected faunal dynamics of benthic invertebrate assemblages across the Toarcian Oceanic Anoxic Event in the Iberian Basin (Spain)

PLoS ONE ◽  
2020 ◽  
Vol 15 (12) ◽  
pp. e0242331
Author(s):  
Veronica Piazza ◽  
Clemens V. Ullmann ◽  
Martin Aberhan
Keyword(s):  
Carbon Cycle ◽  
Marine Invertebrates ◽  
Benthic Invertebrate ◽  
Ecological Change ◽  
Western Tethys ◽  
Oceanic Anoxic Event ◽  
Faunal Assemblages ◽  
Iberian Basin ◽  
Anoxic Event ◽  
Modes Of Life

The Toarcian Oceanic Anoxic Event (TOAE; Early Jurassic, ca. 182 Ma ago) represents one of the major environmental disturbances of the Mesozoic and is associated with global warming, widespread anoxia, and a severe perturbation of the global carbon cycle. Warming-related dysoxia-anoxia has long been considered the main cause of elevated marine extinction rates, although extinctions have been recorded also in environments without evidence for deoxygenation. We addressed the role of warming and disturbance of the carbon cycle in an oxygenated habitat in the Iberian Basin, Spain, by correlating high resolution quantitative faunal occurrences of early Toarcian benthic marine invertebrates with geochemical proxy data (δ18O and δ13C). We find that temperature, as derived from the δ18O record of shells, is significantly correlated with taxonomic and functional diversity and ecological composition, whereas we find no evidence to link carbon cycle variations to the faunal patterns. The local faunal assemblages before and after the TOAE are taxonomically and ecologically distinct. Most ecological change occurred at the onset of the TOAE, synchronous with an increase in water temperatures, and involved declines in multiple diversity metrics, abundance, and biomass. The TOAE interval experienced a complete turnover of brachiopods and a predominance of opportunistic species, which underscores the generality of this pattern recorded elsewhere in the western Tethys Ocean. Ecological instability during the TOAE is indicated by distinct fluctuations in diversity and in the relative abundance of individual modes of life. Local recovery to ecologically stable and diverse post-TOAE faunal assemblages occurred rapidly at the end of the TOAE, synchronous with decreasing water temperatures. Because oxygen-depleted conditions prevailed in many other regions during the TOAE, this study demonstrates that multiple mechanisms can be operating simultaneously with different relative contributions in different parts of the ocean.

scholarly journals An open marine record of the Toarcian oceanic anoxic event

2011 ◽  
Vol 3 (1) ◽  
pp. 385-410 ◽  
Author(s):  
D. R. Gröcke ◽  
R. S. Hori ◽  
J. Trabucho-Alexandre ◽  
D. B. Kemp ◽  
L. Schwark
Keyword(s):  
Organic Matter ◽  
Carbon Cycle ◽  
Carbon Isotope ◽  
Isotope Composition ◽  
Global Carbon Cycle ◽  
Open Ocean ◽  
Black Shales ◽  
Oceanic Anoxic Event ◽  
Anoxic Event ◽  
Global Carbon

Abstract. Oceanic anoxic events were time intervals in the Mesozoic characterized by widespread distribution of marine organic-rich sediments (black shales) and significant perturbations in the global carbon cycle. The expression of these perturbations is globally recorded in sediments as excursions in the carbon isotope record irrespective of lithology or depositional environment. During the Early Toarcian, black shales were deposited on the epi- and peri-continental shelves of Pangaea and these sedimentary rocks are associated with a pronounced (ca. 7‰) negative (organic) carbon isotope excursion (CIE) which is thought to be the result of a major perturbation in the global carbon cycle. For this reason, the Early Toarcian is thought to represent an oceanic anoxic event (the T-OAE). Associated with this event, there were pronounced perturbations in global weathering rates and seawater temperatures. Although it is commonly asserted that the T-OAE is a global event and that the distribution of black shales is likewise global, an isotopic and/or organic-rich expression of this event has as yet only been recognized on epi- and peri-continental Pangaean localities. To address this issue, the carbon isotope composition of organic matter (δ13Corg) of Early Toarcian cherts from Japan that were deposited in the open Panthalassa Ocean was analysed. The results show the presence of a major (>6‰) negative excursion in δ13Corg that, based on radiolarian biostratigraphy, is a correlative of the Early Toarcian negative CIE known from European epicontinental strata. Furthermore, a secondary ca. −2‰ excursion in δ13Corg is also recognized lower in the studied succession that, within the current biostratigraphical resolution, is likely to represent the excursion that occurs close to the Pliensbachian/Toarcian boundary and which is also recorded in European epicontinental successions. These results from the open ocean realm suggest that, in conjunction with other previously published datasets, these major Early Jurassic carbon cycle perturbations affected all active global reservoirs of the exchangeable carbon cycle (deep marine, shallow marine, atmospheric). An extremely negative δ13Corg value (−57‰) during the peak of the T-OAE is also reported, which suggests that the inferred open ocean mid-water oxygen minimum layer within which these sediments are thought to have been deposited was highly enriched in methanotrophic bacteria, since these organisms are the only plausible producers of such 12C-enriched organic matter.

scholarly journals An open ocean record of the Toarcian oceanic anoxic event

Solid Earth ◽  
2011 ◽  
Vol 2 (2) ◽  
pp. 245-257 ◽  
Author(s):  
D. R. Gröcke ◽  
R. S. Hori ◽  
J. Trabucho-Alexandre ◽  
D. B. Kemp ◽  
L. Schwark
Keyword(s):  
Organic Matter ◽  
Carbon Cycle ◽  
Carbon Isotope ◽  
Isotope Composition ◽  
Global Carbon Cycle ◽  
Open Ocean ◽  
Black Shales ◽  
Oceanic Anoxic Event ◽  
Anoxic Event ◽  
Global Carbon

Abstract. Oceanic anoxic events were time intervals in the Mesozoic characterized by widespread distribution of marine organic matter-rich sediments (black shales) and significant perturbations in the global carbon cycle. These perturbations are globally recorded in sediments as carbon isotope excursions irrespective of lithology and depositional environment. During the early Toarcian, black shales were deposited on the epi- and pericontinental shelves of Pangaea, and these sedimentary rocks are associated with a pronounced (ca. 7 ‰) negative (organic) carbon isotope excursion (CIE) which is thought to be the result of a major perturbation in the global carbon cycle. For this reason, the lower Toarcian is thought to represent an oceanic anoxic event (the T-OAE). If the T-OAE was indeed a global event, an isotopic expression of this event should be found beyond the epi- and pericontinental Pangaean localities. To address this issue, the carbon isotope composition of organic matter (δ13Corg of lower Toarcian organic matter-rich cherts from Japan, deposited in the open Panthalassa Ocean, was analysed. The results show the presence of a major (>6 ‰) negative excursion in δ13Corg that, based on radiolarian biostratigraphy, is a correlative of the lower Toarcian negative CIE known from Pangaean epi- and pericontinental strata. A smaller negative excursion in δ13Corg (ca. 2 ‰) is recognized lower in the studied succession. This excursion may, within the current biostratigraphic resolution, represent the excursion recorded in European epicontinental successions close to the Pliensbachian/Toarcian boundary. These results from the open ocean realm suggest, in conjunction with other previously published datasets, that these Early Jurassic carbon cycle perturbations affected the active global reservoirs of the exchangeable carbon cycle (deep marine, shallow marine, atmospheric).

scholarly journals A global CO<sub>2</sub> flux dataset (2015–2019) inferred from OCO-2 retrievals using the Tan-Tracker inversion system

2021 ◽  
Author(s):  
Zhe Jin ◽  
Xiangjun Tian ◽  
Rui Han ◽  
Yu Fu ◽  
Xin Li ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Carbon Cycle ◽  
Carbon Flux ◽  
Carbon Budget ◽  
Terrestrial Ecosystem ◽  
Carbon Fluxes ◽  
Global Carbon Cycle ◽  
Ocean Carbon ◽  
Global Carbon ◽  
Regional Fluxes

Abstract. Accurate assessment of the various sources and sinks of carbon dioxide (CO2), especially terrestrial ecosystem and ocean fluxes with high uncertainties, is important for understanding of the global carbon cycle, supporting the formulation of climate policies, and projecting future climate change. Satellite retrievals of the column-averaged dry air mole fractions of CO2 (XCO2) are being widely used to improve carbon flux estimation due to their broad spatial coverage. However, there is no consensus on the robust estimates of regional fluxes. In this study, we present a global and regional resolved terrestrial ecosystem carbon flux (NEE) and ocean carbon flux dataset for 2015–2019. The dataset was generated using the Tan-Tracker inversion system by assimilating Observing Carbon Observatory 2 (OCO-2) column CO2 retrievals. The posterior NEE and ocean carbon fluxes were comprehensively validated by comparing posterior simulated CO2 concentrations with OCO-2 independent retrievals and Total Carbon Column Observing Network (TCCON) measurements. The validation showed that posterior carbon fluxes significantly improved the modelling of atmospheric CO2 concentrations, with global mean biases of 0.33 ppm against OCO-2 retrievals and 0.12 ppm against TCCON measurements. We described the characteristics of the dataset at global, regional, and Tibetan Plateau scales in terms of the carbon budget, annual and seasonal variations, and spatial distribution. The posterior 5-year annual mean global atmospheric CO2 growth rate was 5.35 PgC yr−1, which was within the uncertainty of the Global Carbon Budget 2020 estimate (5.49 PgC yr−1). The posterior annual mean NEE and ocean carbon fluxes were −4.07 and −3.33 PgC yr−1, respectively. Regional fluxes were analysed based on TransCom partitioning. All 11 land regions acted as carbon sinks, except for Tropical South America, which was almost neutral. The strongest carbon sinks were located in Boreal Asia, followed by Temperate Asia and North Africa. The entire Tibetan Plateau ecosystem was estimated as a carbon sink, taking up −49.52 TgC yr−1 on average, with the strongest sink occurring in eastern alpine meadows. These results indicate that our dataset captures surface carbon fluxes well and provides insight into the global carbon cycle. The dataset can be accessed at https://doi.org/10.11888/Meteoro.tpdc.271317 (Jin et al., 2021).

scholarly journals Carbon Stock Variation along altitudinal gradient of Wacho Forest in Hawa Galan District, Kellem Wollega Zone, Oromia Region, Ethiopia

2020 ◽  
Author(s):  
Gezahegn Gashu ◽  
Gebre Gidey ◽  
Sime Deressa ◽  
Zame Fekansa ◽  
Halid Awoke
Keyword(s):  
Forest Ecosystem ◽  
Carbon Stock ◽  
Terrestrial Ecosystem ◽  
The Third ◽  
Natural Break ◽  
Below Ground ◽  
Carbon Reservoir ◽  
Potential Strategy ◽  
Atmospheric Concentrations ◽  
Global Carbon

Abstract Background Forest ecosystem plays a crucial role in the global carbon cycle; as such, mitigating high atmospheric concentrations of carbon dioxide and other greenhouse gases by naturally taking carbon from the atmosphere through photosynthesis. Verification and accounting of carbon stock in forest ecosystem have been renowned as a potential strategy to reduce and stabilize atmospheric concentrations of greenhouse gas. Forest sequesters and store more carbon than any other terrestrial ecosystem and it is an important natural break on climate change. It acts as a carbon reservoir by storing large amount of carbon in trees, undergrowth vegetation, forest floor and soil. Result The mean carbon stock of each carbon pool was changed along altitudinal class of the study area. The largest mean above and below ground carbon stock was found in the second altitudinal class(1560.01-1643m) followed by first altitudinal class(1435-1560m) and the third altitudinal class (1643.01-1704m) of the study area. The largest mean dead tree and dead wood carbon stock was also stored in the first altitudinal class followed by the third and the second altitudinal class of the study area. The largest mean litter carbon stock was found in the first altitudinal class followed by the second and the third altitudinal class of the study area. The largest mean soil organic carbon was found in the third altitudinal class followed by the second and the first altitudinal class of the study area. Conclusions The carbon stock variation along altitudinal gradients indicated that, altitude had no a statistically significant effect on any of the carbon pools except litter carbon of the study area at 95% of confidence interval.

Onset of Oceanic Anoxic Event 2 in the Lower Saxony Basin – Insights fromhigh-resolution stable isotope stratigraphy and geochemical modelling

2021 ◽  
Author(s):  
Pia Müller ◽  
Ulrich Heimhofer ◽  
Christian Ostertag-Henning
Keyword(s):  
Organic Matter ◽  
High Resolution ◽  
Stable Isotope ◽  
Carbon Cycle ◽  
Geochemical Modelling ◽  
Positive Anomaly ◽  
Lower Saxony ◽  
Data Set ◽  
Oceanic Anoxic Event ◽  
Anoxic Event

&lt;p&gt;The Oceanic Anoxic Event (OAE) 2 spanning the Cenomanian-Turonian boundary (93.5 Ma)&lt;br&gt;represents a major perturbation of the global carbon cycle and is marked by organic-rich&lt;br&gt;sediments deposited under oxygen-depleted conditions. In many studies the eruption of the&lt;br&gt;Caribbean LIP is considered to be the cause for rapidly increasing CO2 concentrations and&lt;br&gt;resulting global warming accompanied by widespread oceanic anoxia. In the Lower Saxony&lt;br&gt;Basin of northern Germany, the deposits of the OAE 2 are exposed in several industry drill&lt;br&gt;cores. In this study, the lower part of the OAE 2 has been studied in the HOLCIM 2011-3 drill&lt;br&gt;core. Sedimentary rocks are composed of limestones, marly limestones, marls and black&lt;br&gt;shales and have been analysed with a high-resolution stable isotope approach&lt;br&gt;(approximately one sample every 2 cm) combined with geochemical modelling. Using stable&lt;br&gt;carbon isotopes, bulk rock parameters and petrographic analysis, the onset of OAE 2 has&lt;br&gt;been investigated in detail. The high-resolution &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C curve exhibits overall stable values&lt;br&gt;around 3 &amp;#8240; before the onset of the Plenus event. This background level is interrupted by&lt;br&gt;three short-lived and small but significant negative carbon isotope excursions (CIEs) down to&lt;br&gt;&amp;#948;&lt;sup&gt;13&lt;/sup&gt;C values of 2.5 &amp;#8240;, 2.7 &amp;#8240; and 1.9 &amp;#8240;. Immediately before the main rise in the Plenus bed,&lt;br&gt;a longer-lasting negative CIE down to 2.8 &amp;#8240; is observed, preceding the large positive CIE of&lt;br&gt;the OAE 2 to values of 5.2 &amp;#8240; over 33 ka. Thereafter, the &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C values decrease to 3.5 &amp;#8240; over&lt;br&gt;a period of approximately 130 ka. The results can be correlated with the lower-resolution&lt;br&gt;data set of Voigt et al. (2008) but enable a more accurate characterization of the subtle&lt;br&gt;features of the CIE and hence events before and during this time interval. Carbon cycle&lt;br&gt;modelling with the modelling software SIMILE using a model based on Kump &amp; Arthur (1999)&lt;br&gt;reveals that the negative excursion before the Plenus bed can be explained by a massive&lt;br&gt;volcanic pulse releasing of 0.95*10&lt;sup&gt;18&lt;/sup&gt; mol CO2 within 14 ka. This amount corresponds to only&lt;br&gt;81 % of the calculated volume of CO&lt;sub&gt;2&lt;/sub&gt; release during emplacement of the Caribbean LIP by&lt;br&gt;Joo et al. (2020). In the model the volcanic exhalation increases atmospheric CO&lt;sub&gt;2&lt;/sub&gt;&lt;br&gt;concentrations. This will increase global temperatures, intensify the hydrological cycle and&lt;br&gt;thus increase nutrient input into the ocean, resulting in an expansion of the oxygen minimum&lt;br&gt;zone, the development of anoxic conditions and an increase in the preservation potential for&lt;br&gt;organic material. In the model enhanced primary productivity and organic matter preservation&lt;br&gt;can be controlled by the implemented riverine phosphate input and the preservation factor for&lt;br&gt;organic matter. For the positive anomaly, the riverine phosphate input must be nearly&lt;br&gt;doubled (from 0.01 &amp;#956;mol/kg PO&lt;sub&gt;4 &lt;/sub&gt;to 0.019 &amp;#956;mol/kg) for the period of the increasing &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C&lt;br&gt;values (app. 33 ka), with a concomitant rise of the preservation factor from 1 % to 2 %. This&lt;br&gt;model scenario accurately reproduces the major features of the new high-resolution &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C&lt;br&gt;record over the onset of the OAE 2 CIE.&lt;/p&gt;

A new record of the Toarcian oceanic anoxic event from Scotland (UK) and environmental responses

2021 ◽  
Author(s):  
Wenhan Chen ◽  
David Bryan Kemp ◽  
Tianchen He ◽  
Chunju Huang
Keyword(s):  
Chemical Weathering ◽  
Coarse Grained ◽  
Global Ocean ◽  
Geochemical Data ◽  
Oceanic Anoxic Event ◽  
Organic Carbon Isotope ◽  
Anoxic Event ◽  
Geographic Differences ◽  
Environmental Responses ◽  
Global Carbon

&lt;p&gt;The early Toarcian oceanic anoxic event (T-OAE, ~183 Ma) was characterized by a prominent environmental perturbation, likely associated with a large amount of &lt;sup&gt;12&lt;/sup&gt;C-enriched carbon released into the global ocean-atmosphere system. This effusion caused a marked disruption to the global carbon cycle and propagated a series of remarkable changes in ocean chemistry and climate. Although the T-OAE has been recognized worldwide, clear geographic differences in the character of the event and its environmental effects have been recognized. Here, we present new geochemical data from a lower Toarcian succession on the Isle of Raasay, NE Scotland (Hebrides Basin, Northwest European Shelf). Organic carbon isotope data through the Raasay section reveal a pronounced negative excursion, similar to that recognised globally. The excursion interval is enriched in organic matter, and redox sensitive element data suggest that suboxic bottom water conditions contemporaneously occurred, likely interspersed with anoxic episodes. Our findings contrast with evidence of more pervasive anoxia/euxinia in nearby basins, and emphasize how deoxygenation was spatially variable within the T-OAE. Inorganic geochemical data and sedimentological observations suggest a significant enhancement in chemical weathering and coarse-grained detrital flux during the T-OAE on Raasay. These findings support evidence from other localities for a strengthening of hydrological cycling in response to global warming during the T-OAE.&lt;/p&gt;

Recurrent global carbon cycle disturbances during the Aalenian: Evidence from France and Chile

2021 ◽  
Author(s):  
Alicia Fantasia ◽  
Thierry Adatte ◽  
Jorge E. Spangenberg ◽  
Emanuela Mattioli ◽  
Enrique Bernárdez ◽  
...  
Keyword(s):  
High Resolution ◽  
Carbon Cycle ◽  
Middle Jurassic ◽  
Environmental Changes ◽  
Global Carbon Cycle ◽  
Oceanic Anoxic Event ◽  
Carbon Substrates ◽  
Rock Eval ◽  
Resolution Dataset ◽  
Global Carbon

&lt;p&gt;The Jurassic was punctuated by several episodes of abrupt environmental changes associated with climatic instabilities, severe biotic crisis, and perturbations of the global carbon cycle. Over the last decades, the Toarcian Oceanic Anoxic Event (Early Jurassic, ~183 Ma) and the early Bajocian Event (Middle Jurassic, ~170&amp;#8211;168 Ma) have attracted much attention because they represent such episodes of global and severe environmental change. Bracketed in between the Toarcian and the Bajocian, the Aalenian stage (Middle Jurassic, ~174-170 Ma) has received less attention, although there is some evidence from Tethyan and Boreal records that it was a time of environmental changes marked by marine biotic turnovers. The lack of knowledge about the Aalenian palaeoenvironments leaves a gap in our understanding of the wider context of the Toarcian and Bajocian events and hence of environmental feedback mechanisms surrounding Mesozoic carbon cycle perturbations. In this study, we provide a high-resolution, biostratigraphically well-defined carbon isotope records (&lt;em&gt;&amp;#948;&lt;/em&gt;&lt;sup&gt;13&lt;/sup&gt;C&lt;sub&gt;org&amp;#160;&lt;/sub&gt;and &lt;em&gt;&amp;#948;&lt;/em&gt;&lt;sup&gt;13&lt;/sup&gt;C&lt;sub&gt;carb&lt;/sub&gt;) combined to Rock-Eval data for the upper Toarcian&amp;#8211;lower Bajocian interval from two expanded marl/limestone alternation successions from France (French Subalpine Basin) and Chile (Andean Basin). The comparison with available records from the Tethyan and Boreal domains highlights that medium-term &lt;em&gt;&amp;#948;&lt;/em&gt;&lt;sup&gt;13&lt;/sup&gt;C fluctuations are reproducible across different palaeoceanographic settings from both hemispheres and between different carbon substrates. The new high-resolution dataset highlights the complexity of the Aalenian &lt;em&gt;&amp;#948;&lt;/em&gt;&lt;sup&gt;13&lt;/sup&gt;C record, including previously identified &lt;em&gt;&amp;#948;&lt;/em&gt;&lt;sup&gt;13&lt;/sup&gt;C shifts and hitherto undescribed fluctuations. This study provides one of the most expanded high-resolution chemostratigraphic reference records for the entire Aalenian stage, and shows compelling evidence from both hemispheres that it was a time marked by recurrent perturbations to the global carbon cycle and environmental changes.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;

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