Paleoenvironmental changes and nitrogen cycling of the lacustrine systems following the Toarcian Oceanic Anoxic Event in the Sichuan Basin (China): Insights from nitrogen isotopes

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F61389005%3A_____%2F25%3A00619379" target="_blank" >RIV/61389005:_____/25:00619379 - isvavai.cz</a>

Výsledek na webu

<a href="https://www.sciencedirect.com/science/article/pii/S0009254125001871" target="_blank" >https://www.sciencedirect.com/science/article/pii/S0009254125001871</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1016/j.chemgeo.2025.122797" target="_blank" >10.1016/j.chemgeo.2025.122797</a>

Jazyk výsledku

angličtina

Název v původním jazyce

Paleoenvironmental changes and nitrogen cycling of the lacustrine systems following the Toarcian Oceanic Anoxic Event in the Sichuan Basin (China): Insights from nitrogen isotopes

Popis výsledku v původním jazyce

The Toarcian Oceanic Anoxic Event (T-OAE) represents a significant disturbance of the Earth's atmosphere-ocean system in the Early Jurassic, and its response in lacustrine systems has been widely studied in recent years. However, the impact of T-OAE on the subsequent environmental changes and nitrogen cycling patterns in lacustrine systems are poorly understood. This study investigated the paleoenvironmental changes following the T-OAE based on elemental geochemistry analyses of organic-rich shales from the Early Jurassic Da'anzhai Member and the Middle Jurassic Lianggaoshan Formation in the Sichuan Basin. The nitrogen cycling during this period was reconstructed drawing on nitrogen isotopes (delta 15N) and their correlations with water column conditions. The results indicated that during the deposition of Da'anzhai shale (i.e., T-OAE period), the lacustrine system was dominated by a temperate-humid climate, with frequent oxic-suboxic variations in the water column. The sedimentary environment of the Lianggaoshan shale was similar to that of the Da'anzhai shale, even though there was a brief arid-cold climate during the sedimentary period at the bottom of Lianggaoshan Formation. The nitrogen isotopes of kerogen (delta 15Nker) were primarily controlled by the redox conditions of water column, and the silicate-bound inorganic nitrogen isotopes (delta 15Nsil) were influenced by combined factors including climate, input of terrestrial clay minerals, and the redox conditions of the bottom water column. These variations in delta 15N provided foundations for reconstructing nitrogen cycling under diverse lacustrine environmental conditions. Under the suboxic water column, the occurrence of denitrification and anaerobic ammonium oxidation (anammox) in the chemocline resulted in enrichment of 15N in kerogen. The positive excursion in delta 15Nsil was a cumulative effect attributed to the enhanced influx of exogenous illite under temperate-humid climatic conditions, as well as the combined influence of anammox on NH4+ concentrations. In water column with elevated oxygen concentrations, biogeochemical processes, predominantly driven by nitrification, resulted in lighter delta 15Nker values, and delta 15Nsil, influenced by the low concentration of NH4+ in the bottom water, also exhibited a lighter isotopic signature. The similar geochemical signatures in the Da'anzhai and Lianggaoshan shales implied that the lacustrine system might be susceptible to variations in localized paleoenvironment, and was not completely consistent with the marine system.

Název v anglickém jazyce

Paleoenvironmental changes and nitrogen cycling of the lacustrine systems following the Toarcian Oceanic Anoxic Event in the Sichuan Basin (China): Insights from nitrogen isotopes

Popis výsledku anglicky

The Toarcian Oceanic Anoxic Event (T-OAE) represents a significant disturbance of the Earth's atmosphere-ocean system in the Early Jurassic, and its response in lacustrine systems has been widely studied in recent years. However, the impact of T-OAE on the subsequent environmental changes and nitrogen cycling patterns in lacustrine systems are poorly understood. This study investigated the paleoenvironmental changes following the T-OAE based on elemental geochemistry analyses of organic-rich shales from the Early Jurassic Da'anzhai Member and the Middle Jurassic Lianggaoshan Formation in the Sichuan Basin. The nitrogen cycling during this period was reconstructed drawing on nitrogen isotopes (delta 15N) and their correlations with water column conditions. The results indicated that during the deposition of Da'anzhai shale (i.e., T-OAE period), the lacustrine system was dominated by a temperate-humid climate, with frequent oxic-suboxic variations in the water column. The sedimentary environment of the Lianggaoshan shale was similar to that of the Da'anzhai shale, even though there was a brief arid-cold climate during the sedimentary period at the bottom of Lianggaoshan Formation. The nitrogen isotopes of kerogen (delta 15Nker) were primarily controlled by the redox conditions of water column, and the silicate-bound inorganic nitrogen isotopes (delta 15Nsil) were influenced by combined factors including climate, input of terrestrial clay minerals, and the redox conditions of the bottom water column. These variations in delta 15N provided foundations for reconstructing nitrogen cycling under diverse lacustrine environmental conditions. Under the suboxic water column, the occurrence of denitrification and anaerobic ammonium oxidation (anammox) in the chemocline resulted in enrichment of 15N in kerogen. The positive excursion in delta 15Nsil was a cumulative effect attributed to the enhanced influx of exogenous illite under temperate-humid climatic conditions, as well as the combined influence of anammox on NH4+ concentrations. In water column with elevated oxygen concentrations, biogeochemical processes, predominantly driven by nitrification, resulted in lighter delta 15Nker values, and delta 15Nsil, influenced by the low concentration of NH4+ in the bottom water, also exhibited a lighter isotopic signature. The similar geochemical signatures in the Da'anzhai and Lianggaoshan shales implied that the lacustrine system might be susceptible to variations in localized paleoenvironment, and was not completely consistent with the marine system.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10505 - Geology

Projekt

—

Návaznosti

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Rok uplatnění

2025

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Název periodika

Chemical Geology

ISSN

0009-2541

e-ISSN

1872-6836

Svazek periodika

685

Číslo periodika v rámci svazku

July

Stát vydavatele periodika

NL - Nizozemsko

Počet stran výsledku

14

Strana od-do

122797

Kód UT WoS článku

001476319000001

EID výsledku v databázi Scopus

2-s2.0-105002792021