美国研究人员最近对中国贵州陡山沱出土的古代岩石样本进行研究后发现，迄今为止最早的动物化石存在于古代湖泊沉积岩中，并非像之前普遍认为的那样存在于海底沉积物中。这一发现表明，早期动物可能以湖为家。
美国加利福尼亚大学研究人员在新一期美国《国家科学院院刊》（PNAS）月刊网络版上发表论文说，他们在中国贵州陡山沱地区发现了大量保存有早期动物化石的黏土矿物——蒙脱石，这种矿物一般会随着地质演变发生质变，而陡山沱地区的蒙脱石却保存完好。研究人员对这一地区蒙脱石的进一步研究证明，这种矿物只能存在于碱水湖中。
研究人员认为，这一发现可能表明，动物最早在湖中进化，而且只有某些特定的湖泊环境适宜动物进化。
中国贵州陡山沱是世界上最古老的化石遗址之一，蕴藏有迄今6.3亿年历史的动物胚胎化石。（生物谷Bioon.com）
生物谷推荐原始出处：
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.
