Age dating of basalt
) in the eastern Grand Canyon, Coconino County, Arizona.
The lower part of the Cardenas Basalt forms granular talus slopes.
Thus, the contact between the Cardenas Lavas and the Dox Formation is conformable and interfingering.
The lava within this unit consists of pahoehoe lava flows of olivine-rich basalt.It is about 200 m (660 ft) thick and contains four to six, prominent lava flows that range in composition from quartz tholeiite to tholeiitic andesite (icelandite).Some of the lava flows are fan-jointed, ropy, and have porphyritic to aphanitic and vesicular textures.The lower unit ranges in thickness from 75 to 90 m (246 to 295 ft) and forms low, talus covered slopes.It consists of complexly interbedded, thin, and discontinuous beds of basalt, hyaloclastite, and sandstone.