文献类型：期刊文献

英文题名：Nitrogen and carbon isotopic perturbations at the onset of Great Ordovician Biodiversification Event of North China

作者：Huang, Hanli[1,2,3];Cao, Hansheng[1,2,3];Chen, Fajin[1,2,3];Wang, Zaiyun[1,2,3];Zhou, Fengxia[1,2,3];Chen, Qiuping[1,2,3];Zeng, Yuda[1,2,3];Chen, Chunqing[1,2,3]

机构：[1]Guangdong Ocean Univ, Coll Ocean & Meteorol, Lab Coastal Ocean Variat & Disaster Predict, Zhanjiang 524088, Peoples R China;[2]Guangdong Ocean Univ, Coll Ocean & Meteorol, Dept Educ Guangdong Prov, Key Lab Climate Resources & Environm Continental S, Zhanjiang 524088, Peoples R China;[3]Minist Nat Resources, Key Lab Space Ocean Remote Sensing & Applicat, Beijing 100081, Peoples R China

年份：2027

卷号：18

期号：1

外文期刊名：GEOSCIENCE FRONTIERS

收录：SCI-EXPANDED(收录号：WOS:001872455200001)、、WOS

基金：We thank the editor and the reviewers, Professor Li Tian and one anonymous reviewer, for their thorough and constructive comments. This research is supported by the Guangdong Natural Science Foundation of China (2025A1515012009, 2022A1515012100) , Zhanjiang Municipal Science and Technology Special Project (2024B01069) .

语种：英文

外文关键词：Early Ordovician; Nitrogen isotopes; Silicate-bound nitrogen; Carbon and nitrogen cycling; North China Craton

外文摘要：The Early Ordovician represents a critical transitional interval in Earth's history, marked by the initial rise of the Paleozoic evolutionary fauna and the onset of the Great Ordovician Biodiversification Event (GOBE). However, this interval remains relatively understudied compared with the main phase of the GOBE, limiting our understanding of the evolution of geochemical and biotic conditions during the early stage of the GOBE. Here, we present a high-resolution nitrogen and carbon isotope record from a successively drilled carbonate core in the North China Craton, including carbonate carbon and oxygen isotopes (b13Ccarb, b18O), organic carbon isotopes 3Corg), bulk nitrogen isotopes 5Nbulk), silicate-bound nitro(b1(b1 gen isotopes 5Nsilicate), biogenic silica (BSi), and nutrient-related elements. The 3Ccarb record signif(b1b1 icantly showed and correlated with the global Top-Skullrock Isotopic Carbon Excursion (TSICE) and the Late Tremadocian Negative Isotopic Carbon Excursion (LTNICE). In the early Tremadocian, high b13Ccarb and 3Corg values are consistent with high-productivity proxies. These carbon isotope signals are attribb1 uted to enhanced organic matter burial associated with the expansion of anoxia in highly productive sea. Meanwhile 5Nsilicate remains systematically higher than coeval 5Nbulk, with an offset exceeding 10 parts per thousand , b1 b1 during the early Tremadocian, indicating enhanced anammox activity at the sediment-water interface. From the middle Tremadocian to the Floian, coeval negative excursions in both b 13Ccarb and b13Corg, together with a reduced D13C (D13C = 3Ccarb-3Corg), are attributed to enhanced oxidative remineralb1b1 ization of organic matter and a decrease in &p (photosynthetic fractionation). The persistently negative b15Nsilicate excursions, along with the concurrent slight negative shift in 5Nbulk and the progressively b1 narrowing offset between the silicate and bulk sedimentary fractions, collectively suggest a gradual suppression of anaerobic nitrogen cycling, consist with enhanced bottom-water oxygenation. The LTNICE interval, in particular, is accompanied by decoupled 3Ccarb-3Corg behavior and minimal D13C, indicatb1b1 ing an oxygenation pulse that enhanced both organic matter oxidation and initial diversification of marine animals, suggesting that oxygen availability may have acted as key environmental triggers for the early diversification phase of the GOBE. (c) 2026 China University of Geosciences (Beijing) and Peking University. Published by Elsevier B.V. on behalf of China University of Geosciences (Beijing). This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).