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Geology of the National Parks - Death Valley

 

click for timescale Death Valley National Park through time

A Mudflat to Remember: Latest Precambrian and Early Cambrian time

Our view of Death Valley's past becomes clearer near the end of Precambrian time. Rocks from this interval are widely exposed and have left a good record for hundreds of miles. Sandy and shaly formations predominate and locally contain mudcracks, worm burrows, ripple-marks, and current features typical of tidal flats, deltas, and nearshore parts of the continental shelf. A shoreline similar to our present Atlantic margin (with coastal lowlands and a wide shallow shelf but no volcanoes) lay to the east near modern Las Vegas.

Abundant quartz and feldspar in the sandstones prove that streams were eroding granitic terrain not far to the east. Erosion was rapid for there were not yet any land-plants. There is not, however, any evidence for a high coastal mountain range. Where rivers released their load to the sea, longshore and strong tidal currents gradually redistributed sandbars and beach sands into submarine sand sheets which stretched for hundreds of miles. To the west, deep-water off-shore equivalents of Death Valley's formations extend all the way to Owens Valley. A few remnants may even survive in the High Sierra.

The side road to Aguereberry Point successively traverses the shaly Johnnie Formation, the white Stirling Quartzite, and dark quartzites of the Wood Canyon Formation; at the Point itself is the great light-colored band of Zabriskie Quartzite dipping away toward Death Valley. (Parts of this sequence are also prominent (1) between Death Valley Buttes and Daylight Pass, (2) in upper Echo Canyon, and (3) just west of Mare Spring in Titus Canyon.) Before tilting into their present orientation, these four formations constituted a continuous pile of mud and sand three miles deep, accumulated slowly on the nearshore ocean bottom.

The dullness of that interval has seldom been surpassed. A gently fluctuating shoreline lay to the east, but in the Death Valley area itself little ever changed but the proportions of sand and silt. A few worms, a little algae, the unrelenting tidal cycle, and a hundred million years worth of mud.

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