 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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