美國研究人員最近對中國貴州陡山沱出土的古代巖石樣本進行研究后發(fā)現(xiàn),，迄今為止最早的動物化石存在于古代湖泊沉積巖中,，并非像之前普遍認為的那樣存在于海底沉積物中,。這一發(fā)現(xiàn)表明,，早期動物可能以湖為家,。
美國加利福尼亞大學研究人員在新一期美國《國家科學院院刊》（PNAS）月刊網(wǎng)絡(luò)版上發(fā)表論文說,，他們在中國貴州陡山沱地區(qū)發(fā)現(xiàn)了大量保存有早期動物化石的黏土礦物——蒙脫石,，這種礦物一般會隨著地質(zhì)演變發(fā)生質(zhì)變,，而陡山沱地區(qū)的蒙脫石卻保存完好。研究人員對這一地區(qū)蒙脫石的進一步研究證明,，這種礦物只能存在于堿水湖中,。
研究人員認為，這一發(fā)現(xiàn)可能表明,，動物最早在湖中進化,，而且只有某些特定的湖泊環(huán)境適宜動物進化。
中國貴州陡山沱是世界上最古老的化石遺址之一,，蘊藏有迄今6.3億年歷史的動物胚胎化石,。（生物谷Bioon.com）
生物谷推薦原始出處：
PNAS doi: 10.1073/pnas.0901080106
Mineralogical constraints on the paleoenvironments of the Ediacaran Doushantuo Formation
Thomas F. Bristowa,1, Martin J. Kennedya, Arkadiusz Derkowskia, Mary L. Drosera, Ganqing Jiangb and Robert A. Creaserc
Assemblages of clay minerals are routinely used as proxies for paleoclimatic change and paleoenvironmental conditions in Phanerozoic rocks. However, this tool is rarely applied in older sedimentary units. In this paper, the clay mineralogy of the Doushantuo Formation in South China is documented, providing constraints on depositional conditions of the Ediacaran Yangtze platform that host the earliest animal fossils in the geological record. In multiple sections from the Yangtze Gorges area, trioctahedral smectite (saponite) and its diagenetic products (mixed-layer chlorite/smectite, corrensite, and chlorite) are the dominant clays through the lower 80 m of the formation and constitute up to 30 wt% of the bulk rock. Saponite is interpreted as an in situ early diagenetic phase that formed in alkaline conditions (pH ≥ 9). The absence of saponite in stratigraphically equivalent basin sections, 200–400 km to the south, indicates that alkaline conditions were localized in a nonmarine basin near the Yangtze Gorges region. This interpretation is consistent with crustal abundances of redox-sensitive trace elements in saponitic mudstones deposited under anoxic conditions, as well as a 10‰ difference in the carbon isotope record between Yangtze Gorges and basin sections. Our findings suggest that nonmarine environments may have been hospitable for the fauna preserved in the Yangtze Gorges, which includes the oldest examples of animal embryo fossils and acanthomorphic acritarchs.
