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Geology of the National Parks - Death Valley


Death Valley National Park through time

Saratoga Springs
View north across Saratoga Spring ponds to hills consisting of late Precambrian Pahrump Group rocks. White band is talc formed by reaction of dolomite with the black diabase enclosing it. A sill of diabase magma intruded between sedimentary layers of Crystal Spring Formation, now seen flanking the diabase at lower left. All units now tilt to east (right). The spring water rises along a fault and becomes ponded by fringing barrier dunes. Photo from NPS archives.

Sediments blanket Death Valley's metamorphic basement

Late Precambrian time

After 1.4 billion years ago, the metamorphosed Precambrian basement rocks had begun to be uplifted. Huge volumes of rocky metamorphic debris must have been eroded and redeposited, but no one knows where.

By about 1.3 billion years ago, sediment began to accumulate on Death Valley's metamorphosed basement rock. At first, muddy debris (now conglomerate) was deposited on land. A shallow sea then washed over these terrestrial deposits, covering the region with thick layers of limestone and dolomite. Algal mats spread across the sea bottom, forming lumpy structures called stromatolites.

The Death Valley region once again rose above sea level and terrestrial deposition resumed, then sank beneath the seas again. The deposits left behind by this alternating sequence of shallow marine, then terrestrial deposition make up the "Pahrump Group" of sandstones, carbonates, and conglomerates.

Move forward in time to Glaciers in the Tropics? (Late Precambrian time)
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