Geology of The Death Valley Area - Passive Margin Formed

Passive Margin Formed

As the incipient ocean widened in the Late Proterozoic and Early Paleozoic, it broke the continental crust in two and a true ocean basin developed to the west. All the earlier formations were thus dissected along a steep front on the two halves of the previous continent. A wedge of clastic sediment then started to accumulate at the base of the two underwater precipices, starting the formation of opposing continental shelves.

Three formations developed from sediment that accumulated on the wedge. They are, from oldest to youngest:

• Johnnie Formation (varicolored shaly),
• Stirling Quartzite,
• Wood Canyon Formation, and the
• Zabriskie Quartzite.

Together the Stirling, Wood Canyon, and Zabriskie units are about 6,000 feet (1,800 m) thick and are made of well-cemented sandstones and conglomerates. They also contain the region's first known fossils of complex life: Ediacara fauna, trilobites, archaeocyathas, and primitive echinoderm burrows have been found in the Wood Canyon Formation. The very earliest animals are exceedingly rare, occurring well west of Death Valley in lime-rich offshore muds contemporary to the Stirling Quartzite. Good outcrops of these formations are exposed on the north face of Tucki Mountain in the northern Panamint Mountains.

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. Prominent outcrops are located between Death Valley Buttes and Daylight Pass, in upper Echo Canyon, and just west of Mare Spring in Titus Canyon. Before tilting to their present orientation, these four formations were a continuous pile of mud and sand 3 miles (4.8 km) deep that accumulated slowly on the nearshore ocean bottom.