Chemicalfossils (e. g. alkanes and porphyrins) are often the only evidence for life in rocks of PRECAMBRIAN age.
化学化石(烷烃和卟啉)是前寒武纪地层中生命存在的唯一证据。
2
Chemicalfossils Particularly resistant organic chemicals present in geological strata that are thought to indicate the existence of life in the period when the rocks were formed.
残存于地质地层中的有机化学物质，当这样的地层被发现时，可以预测出那个地层形成时期的生命活动现象。
3
Geologists are investigating the chemical composition of carbonate rocks that lie beneath the surfaces where early human fossils have been uncovered.