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 an outcropping, some of the larger pebbles are still lens shaped with tapered corners. 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 an outcropping, some of the larger pebbles are still lens shaped with tapered corners. Prescott Heights AZ, Center for Natural History