Precambrian Phyllite (metamorphic conglomerate) 1,800Ma, Prescott AZ
About 1,800 million years (Ma) ago, a sedimentary conglomerate with round pebbles was subducted into an oceanic trench, transforming it into a metamorphic phyllite. During this process, the pebbles were flattened out into lens shaped pancakes, sometimes less than 0.5cm think and over 20cm in diameter. Seen here in cross section, some of the larger pebbles are still lens shaped with tapered corners. The dark red pebbles are hematite (deposited as Banded Iron Formation, BIF) Size approx 20 by 30 cm. Prescott Heights AZ, Center for Natural History
Precambrian Phyllite (metamorphic conglomerate) 1,800Ma, Prescott AZ
About 1,800 million years (Ma) ago, a sedimentary conglomerate with round pebbles was subducted into an oceanic trench, transforming it into a metamorphic phyllite. During this process, the pebbles were flattened out into lens shaped pancakes, sometimes less than 0.5cm think and over 20cm in diameter. Seen here in cross section, some of the larger pebbles are still lens shaped with tapered corners. The dark red pebbles are hematite (deposited as Banded Iron Formation, BIF) Size approx 20 by 30 cm. Prescott Heights AZ, Center for Natural History