NEW FINDINGS IN THE AMARGOSA CHAOS IN DEATH VALLEY, CALIFORNIA, USA

The Amargosa Chaos, in the southeastern portion of Death Valley National Park, consists of highly faulted Proterozoic sedimentary rock overlying crystalline basement. The Chaos plays an important but enigmatic role in many tectonic reconstructions of the area, some of which require northwest translation along a single detachment fault. Virgin Spring Canyon, which cuts through much of the Chaos, hosts a 250-meter-long outcrop with outstanding exposures of both the faults and the rock units that make up the area. This outcrop consists of basement, overlain by quartzite, cherty dolomite, and diabase intrusions of the Crystal Springs formation. The Crystal Springs sits beneath diamictite of the Kingston Peak formation, and the entire outcrop is capped by Noonday Dolomite. Although each unit is distinctly different, they are each sporadically brecciated and largely broken and separated by faults.

After primary data collection, we split the exposure into four parts, separated by three fault sets. Going structurally upwards, these faults separate 1) Basement from Crystal Springs formation, 2) Crystal Springs quartzite from Crystal Springs cherty dolomite, and 3) Noonday Dolomite from Kingston Peak Formation. A fourth set of high angle faults cuts across the entire outcrop and cannot be confined to one lithologic zone. Of these four fault sets, the one between the basement and Crystal Springs marks the location of the alleged Amargosa Fault.

We observed p-foliation, Riedel Shears, slickenlines, and separation that indicate predominantly normal motion on the first three sets, and strike-slip motion on the fourth set. From our data, we argue that these faults indicate overall transport down and to the southeast. This movement contradicts some tectonic reconstruction models, which require top to the northwest transport. We also find that this outcrop was later faulted by a series of high-angle strike-slip faults that are oriented North-South and East-West, likely forming a conjugate pair.