Meng Cheng

Chengdu University of Technology | CDUT · Institute of Sedimentary Geology

Molybdenum (Mo) concentrations and Mo isotopes have been widely used as proxies for local and global redox conditions in early oceans (>520 Ma) that were stratified and characterized by dynamically euxinic mid-depth waters. However, the nature of the Mo cycle and accompanying isotopic fractionations in such oceans remain poorly known. To fill this...

Many late Neoproterozoic to early Cambrian fossils of multicellular eukaryotes, including those of benthic animals, are found preserved under anoxic and even euxinic bottom-water conditions, which is contradictory to the consensus that oxygen is essential to eukaryotes. To investigate this conundrum, we conducted an integrated study of iron speciat...

The Neoproterozoic oxygenation event (NOE) likely began earlier than 800 Ma, raising oxygen levels in the Earth’s atmosphere-ocean system and, thus, setting the stage for the emergence and diversification of animals. However, the redox history of the oceans during the following Cryogenian Period (~720-635 Ma) remains poorly constrained. Here, we pr...

Oxygenation of the early Cambrian ocean is commonly ascribed to high organic export to the sediment due to the rise of algae and filter-feeding animals, but direct evidence of elevated export fluxes has been lacking to date. Here, we report an integrated proxy dataset (U-Mo isotopes, Fe speciation, and major and trace elements) for lower Cambrian b...

In order to explore Cryogenian seawater chemistry and its underlying controls, we present an integrated study of iron speciation, major and trace elements, and carbon isotopes of Mn‑carbonates and their host black shales in the Datangpo Formation from three drillcores (Gaodi, Xixibao and Changxingpo) in the Nanhua Basin, South China. A key aspect o...

The largest negative inorganic carbon isotope excursion in Earth’s history, namely the Ediacaran Shuram Excursion (SE), closely followed by early animal radiation, has been widely interpreted as a consequence of oceanic oxidation. However, the primary nature of the signature, source of oxidants, and tempo of the event remain contested. Here, we sho...

Phosphorus is a limiting nutrient that is thought to control oceanic oxygen levels to a large extent1–3. A possible increase in marine phosphorus concentrations during the Ediacaran Period (about 635–539 million years ago) has been proposed as a driver for increasing oxygen levels4–6. However, little is known about the nature and evolution of phosp...

尽管对寒武纪早期南华盆地已开展了大量古环境重建研究，但南华盆地在寒武纪早期与广海之间的连通性仍不明确，这阻碍了对该时期海洋氧化还原状态演化及其与寒武纪大爆发关系的深入认识.针对上述问题，本研究分析了来自南华盆地内不同水深的三个下寒武系剖面(陆架边缘相道沱、斜坡-盆地相袁家和渣拉沟)的全岩B/Ga组成—这一新近提出的、可用于地质历史时期水体盐度重建的理想指标，以期对寒武纪第2~3期南华盆地的盐度及水文动力学过程进行重建.结果显示在寒武纪早期南华盆地内的水体盐度存在一个由浅水向深水逐渐增加的梯度，该梯度在九门冲组/牛蹄塘组/渣拉沟组的黑色页岩沉积阶段尤为显著.我们认为该盐度梯度可能是在一个中等局限盆地内由临近陆块上输入大量淡水和广海输入海水相混合的结果.在约9Myr的研究区间内，三个剖面的水体盐...

The Ediacaran Period (635–539 Ma) witnessed the largest negative excursion in inorganic carbon isotope (δ13Ccarb) over the Earth’s geological history, also known as the Shuram Excursion (SE) event. The occurrence of the SE has been widely attributed to an increase in atmospheric-oceanic oxygen levels and the subsequent oxidation of organic matters...

埃迪卡拉纪(635~539Ma)发生了地质历史上最大的一次无机碳同位素(δ13Ccarb)负漂移事件(简称为SE事件). 该事件常被解释为大气-海洋的氧含量增加对表生有机质氧化的结果，然而已有数据多难以直接约束氧含量的变化. 因此，重建SE及其前后海洋溶解氧含量([O2])演化对于认识当时海洋碳循环扰动的发生机制具有重要意义. 碳酸盐岩I/(Ca+Mg)是近年来发展起来的能够定量反映古海洋表层海水[O2]的有效指标. 本文分析了塔里木古陆Mochia-Khutuk (简写为MK)剖面埃迪卡拉系水泉组SE事件相关地层的I/(Ca+Mg)组成，发现在该剖面上I/(Ca+Mg)与δ13Ccarb具有同向、同步变化的关系，即I/(Ca+Mg)平均值先随δ13Ccarb的降低由2.2μmol/mol下...

Despite intensive study of the early Cambrian Nanhua Basin (ECNB) in South China, its degree of connectedness to the open ocean remains uncertain, impeding analysis of contemporaneous oceanic redox evolution and its role in the Cambrian Explosion. We analyzed bulk-shale B/Ga, a newly proposed proxy for watermass salinity in ancient depositional sys...

The Ediacaran Period (~635-539 Ma) witnessed the largest negative carbonate carbon isotope (δ13Ccarb) excursion in Earth history (to −12‰ VPDB), known as the Shuram Excursion (SE), which has been attributed to oxidation of a massive dissolved organic matter (DOM) reservoir, yielding highly 13C-depleted oceanic dissolved inorganic carbon (DIC). Lime...

Deposition of iron-enriched redbeds occurred episodically on different continents throughout the mid-Proterozoic, but their origin remains unclear. Since these sediments host abundant Fe oxides, their occurrence potentially represents changes in ocean-redox state, a hypothesis having significant implications for the evolution of early aerobic eukar...

The terminal Ediacaran (∼551–539 Ma) was a crucial period in Earth’s history that witnessed the first appearance of skeletonized animals and complex ecosystems (e.g., the Shibantan Biota) in the ocean. However, the trigger for such biological innovations and their feedbacks to the environment are still poorly understood. In this study, to explore p...

The Ediacaran Period (∼635 to 541 Ma) witnessed the early diversification and radiation of metazoans, in the form of the Ediacaran Biota. This biological revolution, beginning at ∼575 Ma, has been widely attributed to a temporally restricted episode of deeper ocean oxygenation, potentially caused by a contemporaneous rise in atmospheric oxygen leve...

The sulfur isotopic composition (δ³⁴S) of Carbonate Associated Sulfate (CAS) is widely used to track changes in the isotopic composition of ancient seawater sulfate which signify the global sulfur cycle, Earth's surface redox evolution, and biological activity. However, our understanding of to what extent the isotopic composition of CAS records amb...

The Ediacaran Period (~635-539 Ma) witnessed the largest negative inorganic carbon isotope (δ 13 C carb) excursion in Earth's history (i.e., the Shuram Excursion), which is characterized by decoupling from the organic carbon isotope (δ 13 C org) record. The cause(s) of this event remains highly debated. Here, we report a major (~8-9-Myr-long) episo...

The delayed diversification of early animals until the middle Ediacaran Period, despite their likely origin in the Cryogenian Period or earlier, has been attributed to low levels of dissolved O2 in global seawater. To provide more robust constraints on the extent of global-ocean oxygenation during the mid-Cryogenian Period, we analyzed paired U (δ²...

Geobiology explores how Earth's system has changed over the course of geologic history and how living organisms on this planet are impacted by or are indeed causing these changes. For decades, geologists, paleontologists, and geochemists have generated data to investigate these topics. Foundational efforts in sedimentary geochemistry utilized sprea...

The widely developed black shales deposited during the early Cambrian recorded paleoenvironmental information about co-eval seawater. Numerous studies have been conducted on these shales to reconstruct the paleomarine environment during this time period. However, most research has been conducted on stratigraphic sections in South China, and equival...

Benthic oxygen oases linked to photosynthetic mats have been reported in modern anoxic aquatic systems. Benthic macroalgal blooms were common in stratified, anoxic Neoproterozoic oceans, leading us to hypothesize the existence of benthic oxygen oases at that time. This hypothesis has significant implications regarding the bioavailability of transit...

The widely developed black shales deposited during the early Cambrian recorded paleoenvironmental information about coeval seawater. Numerous studies have been conducted on these shales to reconstruct the paleomarine environment during this time period. However, most research has been conducted on stratigraphic sections in South China, and equivale...

The Ediacaran radiation of metazoans is widely thought to have been triggered by an increase in atmospheric and oceanic oxygen levels. Although supported by other proxies, rising oxygen levels were deduced to a significant degree from sedimentary enrichments of redox-sensitive trace elements (RSTEs). However, some organic-rich shales of this period...

The rapid diversification of early animals during the Ediacaran (635-541 Ma) and early Cambrian (ca. 541-509 Ma) has frequently been attributed to increasing oceanic oxygenation. However, the pattern of oceanic oxygenation and its relationship to early animal evolution remain in debate. In this review, we examine the redox structure of Ediacaran an...

Marine redox conditions and their dynamic variations in the early Cambrian are thought to have strongly influenced the evolution of early animals. However, the patterns and mechanisms of contemporaneous marine redox variation remain poorly understood. The Nanhua Basin (South China) was a failed rift basin located between the Yangtze Block (NW margi...

The Mesoproterozoic Era (1.6–1.0 Ga), long regarded as an interval of sluggish biotic evolution and persistently low atmospheric-oceanic oxygen levels, has become the subject of recent controversy regarding putative large-scale oxygenation events. In this study, we conducted a comprehensive investigation of redox, productivity, seawater sulfate con...

The role of O2 in the evolution of early animals, as represented by some members of the Ediacara biota, has been heavily debated because current geochemical evidence paints a conflicting picture regarding global marine O2 levels during key intervals of the rise and fall of the Ediacara biota. Fossil evidence indicates that the diversification the E...

Although oxic surface, ferruginous deep, and euxinic intermediate waters have been documented, the redox heterogeneity of early Cambrian oceans remains largely unclear, precluding our understanding of the relationship between marine redox evolution and early animal diversification. In this study, we analyzed iron species, redox-sensitive trace elem...

It is generally agreed that early diversification of animals and significant rise of atmospheric and oceanic oxygen (O2) levels occurred in the Ediacaran (635–541 million years ago, Ma) and early Cambrian (ca. 541–509 Ma). The strength and nature of their relationship, however, remain unclear and debated. A recent wave of paleoredox research — with...

The Ediacaran Shuram Excursion (SE) was a major negative δ¹³Ccarb excursion (to-12‰) thought to reflect significant atmosphericoceanic oxidation, although direct evidence is limited. Here, we model changes in seawater sulfate concentrations ([SO²⁻4]sw) during the SE by using paired S-isotope data of cogenetic sedimentary pyrite and carbonate-associ...

The early-middle Cambrian (Fortunian to Age 4) is characterized by a significant increase in metazoan diversification. Furthermore, this interval is marked by a prominent environmental and ecological expansion of arthropod- and echinoderm-rich biotas. Recent redox work has suggested that this shift occurred during stable or decreasing marine oxygen...

Although oceanic anoxia is regarded as a leading cause of the Permian-Triassic boundary (PTB) mass extinction, its timing, extent, and underlying causes remain unclear. Here, we conducted a high-resolution Fe-S-C-Mo geochemical study of the entire Changhsingian and lowermost Induan succession in a carbonate-ramp setting at Ganxi, western Hubei Prov...

The early Cambrian Period was a key interval in Earth history with regard to changes in both ocean chemistry and animal evolution. Although increasing ocean ventilation has been widely assumed to have played a key role in the rapid appearance, diversification and spatial colonization of early animals, this relationship is in fact not firmly establi...

Records of the Ediacaran carbon cycle (635-541 million years ago) include the Shuram excursion (SE), the largest negative carbonate carbon isotope excursion in Earth history (down to -12‰). The nature of this excursion remains enigmatic given the difficulties of interpreting a perceived extreme global decrease in the δ(13) C of seawater dissolved i...

Oxygenation has widely been viewed as a major factor driving the emergence and diversification of animals. However, links between early animal evolution and shifts in surface oxygen levels have largely been limited to extrapolation of paleoredox conditions reconstructed from unfossiliferous strata to settings in which contemporaneous fossils were p...

Early oceans (>520 Ma) were characterized by widespread water-column anoxia, stratification, and limited oxidant availability, which are comparable to the chemical characteristics of modern marine sedimentary pore-waters in productive continental margins. Based on this similarity and our current understanding of the formation mechanism of early Ear...

Molybdenum (Mo) proxies, including bulk concentration and isotopic composition, have been increasingly used to reconstruct ancient ocean redox states. This study systematically reviews Mo cycles and their accompanying isotopic fractionations in modern ocean as well as their application in paleo-ocean redox reconstruction. Our review indicates that...