Geoscience Reference
In-Depth Information
Table 2.4
Length of record of landforms and depositional
sequencesinaridzones.
...
the spillway appears to have been raised relative to
Owens Lake since water last overflowed toward Sear-
les Lake. These displacements, presumably linked to
regional magmatism and fault activity, have major
implications for the behavior of Owens Lake and
its linkages southward. Such changes would be su-
perimposed upon those attributable solely to climate
change. Conversely, the deformed shoreline record
provides new evidence for the later tectonic behav-
ior of the Coso Range and the Owens Valley fault
zone within the broader context of the eastern Cali-
fornia shear zone (thus)
Landform/
depositional
sequence
Length of record and
comments
References
Pediments
Mojave desert and
Great Basin:
Minimum age of relict
surfaces 8.9-0.85 Ma
Maximum incision rates
47-8 m/Myr
Maximum slope retreat
rates 365-37 m/Myr
Dohrenwend
(1994)
, over the past 23.5 (kyr)
at least, Owens Lake has been filling and draining
mainly in response to hydroclimatic forcing, but in
a structural basin that has been subsiding relative to
the rising Coso Range and the Haiwee spillway to the
south, and to the Inyo Mountains and Sierra Nevada
to the east and west, respectively.
...
Desert
pavements
Cima volcanic field:
time required for
development 0.2-0.7
Myr
Surface stability of
Negev pavement
1.5-1.8 Ma
McFadden,
Wells and
Dohrenwend
(1986)
Matmon
et al.
(2009)
2.5.2
Playas
Lacustrine
sequences
Intercalated volcanic
ashes dated by
40
Ar/
39
Ar, used to
constrain the age of
lacustrine sequences
in East African Rift
(Lake Turkana) to
beyond 3 Ma
Frostick and
Reid (1987)
Playa lakes (see Chapter 15) develop in local topographic
lows within arid zone drainage systems. Many lakes are
set in basins of inland (endoreic) drainage and it is gen-
erally recognised that tectonic activity is the fundamental
cause of basin closure (Currey, 1994a). The astonishing
profusion of playa lakes in the southwest USA, for ex-
ample, is associated with tectonically active interorogenic
basin and range settings (discussed in Chapter 4). Some
drainage systems may be complex, with spillways com-
ing into operation during lake high stands (e.g. the Owens
River drainage system discussed above).
With the exception of the sequences associated with
the East African Rift, which incorporate datable volcanic
ashes and extend back to beyond 3
Aeolian
sequences
-sandseas
Age estimates of sand
seas are derived from
estimates of sand
fluxes and exceed 1
Ma
Cooke. Warren
and Goudie
(1993)
10
6
yr (Frostick and
×
10
6
yr record of sedimentation
in the Owens River-Death Valley system based on
36
Cl
(Jannick
et al.
, 1991), data on lacustrine/playa sequences
still tend to be limited to the age range of
Reid (1987) note that the backtilting and uplift of footwall
blocks essentially diverts drainage away from the main
axial depocentre. A similar example is provided by the
Red Sea-Gulf of Aden region, where rifting began in the
Miocene, in which rivers approaching within 2 km of
the west bank of the Red Sea are diverted into the Nile
catchment (Frostick and Steel, 1993b).
Tectonic disruption of drainage systems in the south-
west USA is invoked by Zimbelman, Williams and
Tchakerian (1994) in their argument that the ancestral Mo-
jave River originally continued to flow eastwards to join
the Colorado River rather than terminating in the Soda
Lake-Silver Lake playas (Brown
et al.
, 1990). Tectonic
activity has also played an important role in the Owens
River catchment. In a recent study, Orme and Orme (2008,
Reid, 1987), and the 2
×
14
Cof4.5
×
10
4
yr (Brown
et al.
, 1990; Currey, 1994b).
2.5.3
Desert pavements
The antiquity of desert pavements has recently been
demonstrated by Matmon
et al.
(2009) for pavements de-
veloped on old alluvial surfaces in the southern Negev.
Using cosmogenic
10
Be they obtained exposure ages of
1.5-1.8 Ma for chert clasts. The combination of very low
slope angles to horizontal surfaces and (contemporary)
