DEATH VALLEY FAULT ZONE
The Death Valley fault zone is structurally distinct from the Furnace Creek fault zone; the former strikes generally north and is characterized by a large, probably predominant component of normal slip. The fault zone was studied between the mouth of Furnace Creek, north of Texas Spring in central Death Valley, and Shoreline Butte at the south end of Death Valley (southernmost part of pl. 2 and pls. 3 and 4). Evidence of youthful faulting persists throughout nearly all of this zone. The main fault zone extends along the east side of Death Valley, but geomorphic evidence of youthful faulting also can be seen along the west side of the valley. Only the main fault zone is described in this report.
South of Shoreline Butte, the Death Valley fault zone changes from a sinuous, north-trending fault to a linear, northwest-trending fault. This southern extension of the Death Valley fault zone was referred to as the Confidence Hills fault zone by Hunt and Mabey (1966). The late Cenozoic history of the southern Death Valley fault zone recently has been described by Butler and others (1988).
Salt Springs Section
The Salt Springs section (SA, pl. 2), 4.4 km in length, extends from about 1 km north of Salt Springs to the mouth of Cow Creek. Excepting the sinuous northern 1.5 km of the section, the average trend is about N. 10° W. The section is marked by discontinuous, sinuous small scarps cutting alluvial fans of sediments shed from the Funeral Mountains. Previous maps covering the Salt Springs section were published by Hunt and Mabey (1966) and Streitz and Stinson (1977).
The Salt Springs section consists of a northern sinuous but generally northeast-trending breached scarp and a southern set of north to northwest-trending discontinuous scarps. The northern sinuous scarp cuts through Salt Springs and is west facing for a mapped length of 2.3 km; this fault may extend further south-southwest into the valley, but was mapped only for the length covered by low-sun-angle aerial photographs. Relief along this scarp is as great as 3.0 m between Salt Springs and State Highway 190 but diminishes in either direction from that point; maximum slope angle of the scarp is 31°. This fault displaces a lake shoreline (fig. 7) that existed briefly in Death Valley about 2,000 years ago (Hunt, 1960; Hunt and Mabey, 1966). The southern set of scarps is discontinuous, with trends ranging from N. 8° W. to N. 25° W., and relief of generally less than 0.5 m. These scarps are not aligned with one another and locally tend to produce trenches.
Mustard Canyon Section
The Mustard Canyon section (MC, pl. 3) is 3.1 km long and is between the mouth of Cow Creek and BM 221 on State Highway 190. Earlier mapping of the Mustard Canyon section was published by Noble and Wright (1954), Hunt and Mabey (1966), and McAllister (1970).
The Mustard Canyon section is distinctive for three reasons: (1) it is not along a range front, (2) no geomorphic evidence of recent fault activity was observed on low-sun-angle aerial photographs, and (3) the most prominent topographic trends are approximately N. 55° W. rather than north. The prominent northwestern topographic trends of this section, such as the southwest-facing slope along the southern flank of the hills surrounding Mustard Canyon, are probably fault controlled, as they are about parallel to northwest-trending faults cutting nearby bedrock mapped by Hunt and Mabey (1966). The main trend of the Death Valley fault zone is not offset across the Mustard Canyon section, so the relationship of the northwest-trending faults to the Death Valley fault zone is obscure.
Golden Canyon Section
The Golden Canyon section (GO, pl. 3) is 8.7 km long and has a mean trend of N. 22° W. Most of the section is expressed as a west-facing scarp along the western side of the northern Black Mountains. In addition, a 2-km-wide zone of east- and west-facing scarps cuts the alluvial fans of Tucki and Blackwater washes on the west side of Death Valley. Earlier mapping of the Golden Canyon section was published by Noble and Wright (1954), Hunt and Mabey (1966), and McAllister (1970).
The main trace of the Golden Canyon section, along the east side of Death Valley, consists of three pans. The northern 2.1-km-long part trends N. 32° W., and is characterized by several north-trending trenches developed within 0.8 km west of the frontal fault, which is discontinuously exposed. These trenches are mainly in an older surface developed on the Pliocene and Pleistocene(?) Funeral Formation; they are of variable but significant relief, with side slopes inclined generally less than 20°. The southern two parts of the section contain Holocene or late Pleistocene scarps associated with the frontal fault, exposed more or less continuously as a single west-facing fault scarp, which continues into the Artists Drive section to the south at the base of the Black Mountain range front.
The central 3.8-km-long reach of this section, extending southward from just north of Furnace Creek Ranch, trends about N. 11° W. and consists mostly of a west-facing scarp ranging from 0.2 m to 2.3 m high with free-face slopes as steep as 57°, although undercutting by modern alluvial erosion may have oversteepened some slopes. Slopes of scarps in this part of the fault range from 23° to 30°, and from 46° to 57°. These two ranges in slope may represent two faulting events, separated by enough time for the slopes to decline on the older set before the younger set formed.
Careful geodetic leveling across two scarps in this central part of the section, 1.5 km south of Furnace Creek Wash, showed significant vertical creep across the scarps (Sylvester and Bies, 1986); between 1970 and 1985, scarp height on the eastern scarp increased by 7 mm and that on the western scarp by 2 mm.
The southern part of the Golden Canyon section trends linearly N. 30° W. in unconsolidated deposits for 3.2 km. Relief on west-facing scarps is as great as 2.1 m. A few scarps west of the main fault trace define small grabens.
The youngest faulting in the Golden Canyon section, possibly the youngest clearly fault related feature of the Death ValleyFurnace Creek fault system, displaces alluvium that is interpreted to be of late Holocene (Q1B) age. The youngest faulted alluvium is not varnished, contains scarps with free faces, and grades into recent unfaulted alluvium. According to Wallace (1977, 1978), scarps with free faces persist only a few hundred to a few thousand years in central Nevada.
Artists Drive Section
The Artists Drive section (AD, pl. 3) is 13.1 km long with a mean trend of N. 26° W. This section extends from 0.7 km east of the mouth of Desolation Canyon on the north to 0.7 km northwest of Natural Bridge on the south. Earlier mapping of the Artists Drive section was published by Noble and Wright (1954), Hunt and Mabey (1966), and Streitz and Stinson (1977).
This section defines the eastern margin of the Artists Drive fault block of Hunt and Mabey (1966), who mapped the Artists Drive section as continuous with the Golden Canyon section to the north and the Badwater turtleback section to the south. The Artists Drive section is the only section of the Death Valley fault zone that has mainly exposed bedrock west of the most recently active fault trace. Consequently, geomorphic features produced by recent fault activity are not well preserved; scarps within this section offset upper Tertiary volcanic rocks of the Artists Drive Formation of Hunt and Mabey (1966), which are mantled by Tertiary and Quaternary gravels and typically do not have a free face exposed. The north end of the section consists of east-facing scarps in alluvium and bedrock, and at the mouth of Desolation Canyon a short, west-facing scarp has relief of 0.8 m.
The central part of this section consists of a west-facing scarp in unconsolidated gravels with relief of 0.8 m to 3.4 m. A complex trench or graben as wide as 800 m is west of the main scarp, indicating extension normal to the main fault trace. In the southern part of the section, the fault cuts exposed bedrock, and traces indicating recent fault activity are not preserved, even in colluvial gravel deposits along the western margin of the fault. Along the west side of Death Valley, about 12 km west of the faults cutting the west side of the Black Mountains, a series of scarps trending about N. 13° E. defines a complex trench.
The most recent faulting event in the Artists Drive section appears to displace alluvium believed to be of Q1B age with a scarp 0.8-1.2 m high; older alluvium inferred to be of Q1C age has a scarp as high as 5 m. Scarps on an older, Q2, surface are large (as much as 4.8 m of relief) and rounded. These three distinct sets of scarps appear to depict at least three faulting events along the Artists Drive section.
Badwater Turtleback Section
The Badwater turtleback section (BT, pl. 3) is 6.5 km long, has a mean trend of N. 6° W., and extends from 0.7 km northwest of Natural Bridge on the north to 0.4 km east-northeast of Badwater. Earlier mapping of the Badwater turtleback section has been published by Curry (1954), Drewes (1963), and Hunt and Mabey (1966).
Scarps in unconsolidated deposits face mainly westward; many branch scarps or secondary scarps occur in the downthrown block west of the main scarp at the base of the mountain front. The trends of scarps are generally north, but one prominent trench 1 km north of Badwater trends N. 52° W. The predominant type of displacement appears to be down-to-the-west normal faulting. The slopes of scarps within this section are as steep as about 35°, although below an elevation of -260 ft they appear to be modified and oversteepened, probably by lakeshore erosion when ancient Lake Manly reached this elevation about 2,000 years ago (Hunt, 1960). Scarps mapped with slopes of 34°-36° above -260 ft but below sea level are topographically below lake deposits that may correlate with a 10,000 to 11,000-year-old stand of Lake Manly identified by Hooke (1972). These relationships suggest that most scarps within the Badwater turtleback section are between 10,000-11,000 years and 2,000 years old (Q1C age).
Some faults cut deposits inferred to be as young as Q1B. A discontinuous east-facing scarp about 30 m west of the 2.0-m-high east-facing scarp, about 1 km south of the section's northern boundary, cuts surfaces of two ages: (1) a surface on a narrow bar of well-varnished gravel (inferred unit Q1C) south of the road to Natural Bridge, containing two scarps, each with about 0.5 m of relief, and (2) a raised surface to the north covered by unvarnished gravel (inferred unit Q1B) containing a scarp with 0.15 m of relief.
Two faulting events were also identified west of the main fault trace about 1 km north of the section's southern boundary. Here, an older faulted surface shows little varnish and probably represents unit Q2 that was covered by Lake Manly. The maximum slope of a scarp cutting this surface is 12° with relief of 0.7 m. A younger surface at this locality (probably unit Q1B) on premodern alluvium with no varnish is partly obscured by modern Q1A-age alluvium. A scarp cutting the inferred Q1B surface has relief of about 0.2 m.
Black Mountains Section
The Black Mountains section (BM, pl. 3) is 11.2 km long, has a mean trend of N. 4° W., and extends southward from near Badwater to the mouth of Copper Canyon. Earlier mapping of the Black Mountains section was published by Curry (1954), Drewes (1963), Noble and Wright (1954), and Hunt and Mabey (1966).
Faults cutting inferred Q1B surfaces are the youngest along this section, similar to the youngest faults observed in the three sections to the north. A spectacular example of youthful faulting is near the mouth of a wineglass canyon in the center of the Black Mountains section, where inferred Q1B-age alluvium contains east-facing scarps with about 0.2 m of relief. The same ruptures cut an older alluvial unit thought to be of Q1C age, where the relief on the scarps is 0.5 to 1.5 m. These relationships suggest at least two events, one older and one younger than 2,000 years.
A main west-facing frontal scarp is mapped discontinuously at the base of the Black Mountains, and a few east- and west-facing scarps occur in the alluvium west of the frontal scarp. Fissures of unknown origin are along the margins of all of the fans of this section, as well as along the southern margin of the Copper Canyon fan just south of this section. The most recent scarps along the Black Mountains section are commonly west of the frontal scarp, and they may be as steep as 34° to 61° with as much as several meters of vertical offset. Many of the scarps cutting surfaces inferred to be older than Q1B (2,000 years) have free-face slopes steeper than 34°, and slopes of 50° or more are common.
Several grabens are oriented adjacent and roughly parallel to the west side of the main frontal scarp. Additional geomorphic trenches are west of the main scarp near the base of several alluvial fans and define arcuate patterns concentric to the fans. These unusual patterns suggest that fan morphology governs trench geometry and that the trenches are probably caused by compaction of fine-grained deposits at the toe of the fans due to alluvial loading.
Copper Canyon Turtleback Section
The Copper Canyon turtleback section (CO, pl. 4) is 5.8 km long and has a mean trend of N. 28° W. The northern 3.3 km has a mean trend of N. 38° W., and the southern 2.5 km has a mean trend of N. 17° W. The section is between the mouths of Copper Canyon on the north and Sheep Canyon on the south. Earlier mapping of the Copper Canyon turtleback section was published by Curry (1954), Noble and Wright (1954), Wright and Troxel (1954), Drewes (1959), and Hunt and Mabey (1966).
Scarps in unconsolidated deposits in the Copper Canyon turtleback section are predominantly west facing; a few branch faults with east-facing scarps define trenches with the predominant west-facing scarps. The southwest side of the turtleback, a domed and erosionally exposed fault surface separating Tertiary rocks above the surface from Precambrian rocks below (Hunt and Mabey, 1966), trends approximately N. 38° W., and is marked by a discontinuously exposed frontal fault scarp separating Precambrian rock to the northeast from alluvium to the southwest. Many of the scarps have relief in excess of 4 m, and virtually all of the scarps have free-face slopes in excess of 40°. The steepness of the slopes may be related to the bouldery talus present along the base of the range.
Four trenches are identified along this section; three trend north and are on the downthrown block immediately west of the main west-facing scarp. The fourth trench is 490 m wide and trends N. 49° E.
At least three faulting events, the oldest thought to be older than 10,000 years, are preserved at several localities along this section. At a locality 1.6 km north of the mouth of Sheep Creek, a large west-facing scarp with a free face offsets a probable Q2 surface. A smaller scarp, also with a free face, generally follows the trace of the older, larger scarp and displaces a bouldery deposit that shows a well-developed varnish (Q1C age?); the scarp also displaces a Q1B surface by a lesser amount. West of the smaller scarp at this locality is another young scarp that displaces a coarse debris flow interpreted to be Q1B in age. Near the head of the Copper Canyon fan, Q1C-age alluvium is cut by a prominent west-facing scarp, although about 80 m southwest of this scarp, another scarp cuts alluvium of probable Q1B age.
Willow Creek Section
The Willow Creek section (WC, pl. 4) is 5.5 km long with a mean trend of N. 53° E. The section extends from Sheep Canyon southwestward to Mormon Point. Earlier mapping of the Willow Creek section was published by Curry (1954), Drewes (1959), Hill and Troxel (1966), and Hunt and Mabey (1966).
This section is characterized by Quaternary faults that trend northeast, about 60° to the general trend of the Death Valley fault zone. The youngest scarps within the section displace Q1B-age alluvial deposits. All scarps are higher in elevation than the 2,000-year-old Lake Manly shoreline of Hunt and Mabey (1966), so the relative age of faulting to that shoreline is unknown. Most scarps face northwest, although a few face southeast, so that faulting along this section is predominantly down to the northwest, with no evidence observed of a lateral component of slip. Relief on scarps is as much as 9.4 m, with maximum slopes ranging from 21° to overhanging, suggesting local reverse faulting. All scarps are dissected by stream channels filled with unfaulted alluvium. Beveled scarps at two localities within the section are weak evidence for more than one faulting event; at one locality the upper and lower beveled surfaces slope 22° and 70°, whereas at the other locality they slope 40° and 70°. The great heights (as much as 9.4 m) of some scarps of the section also suggest that more than one faulting event occurred along the section; extreme northwest-southeast extension in the Death Valley region (Burchfiel and Stewart, 1966) would logically produce large normal faults along this northeast-oriented section.
Gregory Peak Section
The Gregory Peak section (GP, pl. 4) is along the western base of Smith Mountain from Mormon Point to a location 8.9 km to the south. The mean trend of the section is about N. 28° W. Earlier mapping within the section was published by Hunt and Mabey (1966) and Noble and Wright (1954).
Scarps within the section generally face westward, with secondary and branch scarps facing both eastward and westward. Relief on scarps interpreted as the main range-front fault is as high as 8.8 m. Measured maximum slopes on all scarps vary from 25° to 52°; this wide range in slope angles suggests more than one period of faulting.
No distinct evidence for lateral slip was found along the Gregory Peak section, although at the southern end of the section incised streambeds are faulted with scarp geometry that could be ascribed to normal slip combined with right slip. Also, en echelon northeast fault trends in the southern part of the section may be Reidel fractures associated with a component of right slip.
Four prominent trenches and two prominent branch scarps occur in the downthrown block of the Gregory Peak section west of the main, west-facing range-front fault. The trenches trend north-south to N. 30° W., and the two prominent branch scarps trend north-south to N. 20° E.
Scarps cut alluvium younger than 2,000-year-old lake deposits; the youngest surface faulted appears to be unit Q1B. A well-developed west-facing scarp near the southern border of the section cuts an inferred Q1C surface. A northward extension of the scarp, 0.7 km north of the southern end of the section, has distinctly lower relief where it cuts a Q1B(?) surface and is in part buried by modern (Q1A-age) alluvium.
North Ashford Mill Section
The north Ashford Mill section (NM, pl. 4) is 5.8 km long and has a mean trend of N. 13° W. The northern end of the section is at the northern limit of outcrop of a wedge of Pliocene and Pleistocene(?) Funeral Formation where it is in fault contact with Precambrian rocks on the west side of the Mormon Point turtleback (Nobel and Wright, 1954). At the south end of the section, a 2.2-km-wide zone of outcrop of Funeral Formation separates the Death Valley fault zone and the exposed turtleback surface. Earlier mapping of this section was published by Noble and Wright (1954) and Noble (1941).
This section follows a dissected west-facing fault scarp along the mountain front that has as much as 200 m of relief; the fault displaces interbedded volcanics and fanglomerate of the Funeral Formation (Noble, 1941). Younger east- and west-facing scarps in alluvium along the base of the scarp generally face westward and have as much as 6.6 m of relief; most scarp faces slope between 35° and 40°.
The most recent faults in this section cut Q1B surfaces and are similar in age to the most recent faulting in the Gregory Peak section. No lateral component of movement was noted in the section.
South Ashford Mill Section
The south Ashford Mill section (SM, pl. 4), 2.7 km long, marks the southern extent that was studied along the Death Valley fault zone. The south Ashford Mill section is characterized by a sinuous fault pattern that trends between N. 10° W. and N. 40° W., and extends southward to the southern limit of mapping, about 1 km northwest of Ashford Mill. The fault zone probably extends southward beneath the modern alluvium of the Amargosa River. Earlier mapping of the south Ashford Mill section was published by Noble (1941).
The section crosses the base of an alluvial fan at the mouth of Ashford Canyon and mostly consists of isolated, subdued, rounded scarps in alluvium. In the northern 0.8 km of the section, older scarps with about 80 m of relief displace interlayered basalt, breccia, and fanglomerate of Pliocene(?) age (Noble, 1941). A scarp in Quaternary deposits with 0.3 m of relief is 18 m west of the larger, older scarps. Another discontinuously expressed fault trace trends about N. 10° W. for 2.7 km near the Amargosa River. Scarps along this trace face westward, have relief varying from less than 0.3 m to as much as 0.6 m, and are breached by streams containing unfaulted alluvium. Scarps of this trace also are oriented in a series of en echelon, left-stepping sections, suggesting a component of right slip.
Last Updated: 24-Jul-2009