Priscoan

views updated May 08 2018

Priscoan The first of the three subdivisions of Precambrian time, lasting from the formation of the Earth to 4000 Ma ago ( Harland et al., 1989), and followed by the Archaean. See also HADEAN.

A Dictionary of Earth Sciences AILSA ALLABY and MICHAEL ALLABY

Priscoan

views updated May 21 2018

Priscoan In former geologic time scales, the first period of the Precambrian, covering the time from the formation of the Earth (about 4500 Ma ago) until the first appearance of life about 4000 Ma ago. The name has now been abandoned and this period now comprises the Hadean (4500–3800 Ma ago).

A Dictionary of Zoology MICHAEL ALLABY

Priscoan

views updated May 14 2018

Priscoan The earliest of the three subdivisions of the Precambrian, dated at about 4600–4000 Ma ago. It covers the time approximately from the formation of the Earth until the first appearance of life.

A Dictionary of Ecology MICHAEL ALLABY