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

Result code in 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>

Result on the web

<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>

Result language

angličtina

Original language name

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

Original language description

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.

Czech name

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Czech description

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Type

J_imp - Article in a specialist periodical, which is included in the Web of Science database

CEP classification

—

OECD FORD branch

10505 - Geology

Project

—

Continuities

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Publication year

2025

Confidentiality

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

Name of the periodical

Chemical Geology

ISSN

0009-2541

e-ISSN

1872-6836

Volume of the periodical

685

Issue of the periodical within the volume

July

Country of publishing house

NL - THE KINGDOM OF THE NETHERLANDS

Number of pages

14

Pages from-to

122797

UT code for WoS article

001476319000001

EID of the result in the Scopus database

2-s2.0-105002792021