據(jù)2月12日的《科學(xué)》雜志報(bào)道說,，對(duì)在埃迪卡拉紀(jì)時(shí)地球海洋的研究（即在寒武紀(jì)發(fā)生多元化多細(xì)胞生物物種大爆炸之前的那個(gè)時(shí)候）產(chǎn)生了相互矛盾的結(jié)果,。 有研究提出,，在晚埃迪卡拉紀(jì)的時(shí)候，地球各地的洋盆變得氧氣充沛,，而其它的研究則提出了當(dāng)時(shí)深海水域缺氧的與其矛盾的證據(jù),。
現(xiàn)在，研究人員說,，他們從南部中國(guó)的沉積巖所獲得的數(shù)據(jù)可調(diào)和這些結(jié)論相互抵觸的研究,；他們嘗試用一個(gè)埃迪卡拉紀(jì)海洋的層化模型來解釋生物多元化的最大爆發(fā)之前所出現(xiàn)的長(zhǎng)時(shí)間的延遲,。
為了建立這一模型,，Chao Li及其同僚分析了來自中國(guó)南海洋盆的巖石構(gòu)造中的含鐵礦物及其硫化物和硫酸鹽同位素,。 他們的結(jié)果表明，在埃迪卡拉紀(jì)時(shí)（它處于6億3500萬年之前至5億4200萬年之前之間）地球上的海洋是層化的,，其中某些層區(qū)為硫化物水域和富含鐵的水域,。 這些研究人員描述了穩(wěn)定的富含硫化物及硫酸鹽中水柱，而該水柱則被夾在極度缺氧且富含鐵的區(qū)域之間,。 他們還提出,，這些區(qū)域在整個(gè)埃迪卡拉紀(jì)中通過從大陸架釋放出的硫酸鹽的低度流量加上在這些層化水柱中更深部分的可進(jìn)一步減少硫酸鹽的細(xì)菌活動(dòng)而得到維持。 這些研究人員的模型幫助厘清了在這些原始階段的有關(guān)深?；瘜W(xué)的各種相互矛盾的報(bào)告,。他們提出，這種波動(dòng)的海洋環(huán)境還能夠幫助解釋為什么在埃迪卡拉紀(jì)中存在著這些不協(xié)調(diào)的化石記錄,。（生物谷Bioon.com）
生物谷推薦原始出處：
Science February 11, 2010 DOI: 10.1126/science.1182369
A Stratified Redox Model for the Ediacaran Ocean
Chao Li,1,* Gordon D. Love,1 Timothy W. Lyons,1 David A. Fike,2 Alex L. Sessions,3 Xuelei Chu4
The Ediacaran Period (635-542 million years ago) was a time of fundamental environmental and evolutionary change, culminating in the first appearance of macroscopic animals. Here we present a detailed spatial and temporal record of Ediacaran ocean chemistry for the Doushantuo Formation in the Nanhua Basin, South China. We find evidence for a metastable zone of euxinic (anoxic and sulfidic) waters impinging on the continental shelf and sandwiched within ferruginous [Fe(II)-enriched] deep waters. A stratified ocean with coeval oxic, sulfidic and ferruginous zones, favored by overall low oceanic sulfate concentrations, was maintained dynamically throughout the Ediacaran Period. Our model reconciles seemingly conflicting geochemical redox conditions proposed previously for Ediacaran deep oceans and helps explain the patchy temporal record of early metazoan fossils.
1 Department of Earth Sciences, University of California, Riverside, CA 92521, USA.
2 Department of Earth and Planetary Sciences, Washington University in St Louis, MO 63130, USA.
3 Department of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA.
4 State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China.
