Cardenas Basalt

Cardenas Basalt Cardenas Lava(s) Stratigraphic range: Meso-Proterozoic, 1,104 Ma:
Cardenas Lava on the Colorado River, at Lipan Point–Desert View, East Rim, Grand Canyon
Type	Geological formation
Unit of	Unkar Group
Underlies	Nankoweap Formation
Overlies	Dox Formation
Thickness	985 feet (300 m) approximate maximum
Lithology
Primary	basalt
Other	hyaloclastite, sandstone, and lapillite
Location
Region	Arizona east Grand Canyon Lava Butte region on Colorado River, near Lipan Point
Country	United States of America
Type section
Named for	Cardenas Butte and Cardenas Creek
Named by	Keyes (1938) and Ford et al. (1972)

The Cardenas Basalt, also known as either the Cardenas Lava or Cardenas Lavas, is a rock formation that outcrops over an area of about 310 km² (120 mi²) in the eastern Grand Canyon, Coconino County, Arizona. The lower part of the Cardenas Basalt forms granular talus slopes. Its upper part forms nearly continuous low cliffs that are parallel to the general course of the Colorado River. The most complete, readily accessible, and easily studied exposure of the Cardenas Basalt lies in Basalt Canyon. This is also its type locality.

The Cardenas Basalt is part of the Unkar Group. The Unkar Group is about 1,600 to 2,200 m (5,200 to 7,200 ft) thick and composed, in ascending order, of the Bass Formation, Hakatai Shale, Shinumo Quartzite, Dox Formation, and Cardenas Basalt. In ascending order, the Cardenas Basalt is overlain by the Nankoweap Formation, about 113 to 150 m (371 to 492 ft) thick; the Chuar Group, about 1,900 m (6,200 ft) thick; and the Sixtymile Formation, about 60 m (200 ft) thick. The Grand Canyon Supergroup, of which the Unkar Group is the lowermost part, overlies deeply eroded granites, gneisses, pegmatites, and schists that comprise Vishnu Basement Rocks.

The Cardenas Basalt has also been called the Rama Formation. However this name, which was originally applied to the dikes and sills intruding strata underlying the Cardenas Basalt has been formally abandoned in the geological literature.