Influence of Late Quaternary Climatic Changes on Geomorphic and Pedogenic Processes on a Desert Piedmont, Eastern Mojave Desert, California

1987 ◽  
Vol 27 (2) ◽  
pp. 130-146 ◽  
Author(s):  
Stephen G. Wells ◽  
Leslie D. McFadden ◽  
John C. Dohrenwend
Keyword(s):  
Mojave Desert ◽  
Late Quaternary ◽  
Climatic Changes ◽  
Alluvial Fan ◽  
Age Dating ◽  
The Holocene ◽  
Runoff Reduction ◽  
Mechanical Weathering ◽  
Pedogenic Processes ◽  
Age Constraints

AbstractRadiocarbon dating of late Quaternary deposits and shorelines of Lake Mojave and cation-ratio numerical age dating of stone pavements (Dorn, 1984) on the adjacent Soda Mountains piedmont provide age constraints for alluvial and eolian deposits. These deposits are associated with climatically controlled stands of Lake Mojave during the past 15,000 yr. Six alluvial fan units and three eolian stratigraphic units were assigned ages based on field relations with dated shorelines and piedmont surfaces, as well as on soil-geomorphic data. All but one of these stratigraphic units were deposited in response to time-transgressive climatic changes beginning approximately 10,000 yr ago. Increased eolian flux rates occurred in response to the lowering of Lake Mojave and a consequent increase in fine-sediment availability. Increased rates of deposition of eolian fines and associated salts influenced pedogenesis, stone-pavement development, and runoff-infiltration relations by (1) enhancing mechanical weathering of fan surfaces and hillslopes and (2) forming clay- and silt-rich surface horizons which decrease infiltration. Changes in alluvial-fan source areas from hillslopes to piedmonts during the Holocene reflect runoff reduction on hillslopes caused by colluvial mantle development and runoff enhancement on piedmonts caused by the development of less-permeable soils. Inferred increased in early to middle Holocene monsoonal activity resulted in high-magnitude paleo-sheetflood events on older fan pavements; this runoff triggered piedmont dissection which, in turn, caused increased sediment availability along channel walls. Thus, runoff-infiltration changes during the late Quaternary have occurred in response to eolian deposition of fines, pedogenesis, increased sheetflood activity in the Holocene, and vegetational changes which are related to many complicated linkages among climatic change, lake fluctuations, and eolian, hillslope, and alluvial-fan processes.

Palaeoclimatic and morphodynamic implications of Holocene boulder-dominated periglacial and paraglacial landforms in Rondane, South Norway

2021 ◽  
Author(s):  
Philipp Marr ◽  
Stefan Winkler ◽  
Svein Olaf Dahl ◽  
Jörg Löffler
Keyword(s):  
Slope Failure ◽  
Rock Slope ◽  
Control Point ◽  
Alluvial Fan ◽  
Age Dating ◽  
The Holocene ◽  
Holocene Thermal Maximum ◽  
Exposure Age ◽  
Thermal Maximum ◽  
Exposure Ages

<p>Periglacial, paraglacial and related boulder-dominated landforms constitute a valuable, but often unexplored source of palaeoclimatic and morphodynamic information. The timing of landform formation and stabilization can be linked to past cold climatic conditions which offers the possibility to reconstruct cold climatic periods. In this study, Schmidt-hammer exposure-age dating (SHD) was applied to a variety of boulder-dominated landforms (sorted stripes, blockfield, paraglacial alluvial fan, rock-slope failure) in Rondane, eastern South Norway for the first time. On the basis of an old and young control point a local calibration curve was established from which surface exposure ages of each landform were calculated. The investigation of formation, stabilization and age of the respective landforms permitted an assessment of Holocene climate variability in Rondane and its connectivity to landform evolution. The obtained SHD age estimates range from 11.15 ± 1.22 to 3.99 ± 1.52 ka which shows their general inactive and relict character. Most surface exposure ages of the sorted stripes cluster between 9.62 ± 1.36 and 9.01 ± 1.21 ka and appear to have stabilized towards the end of the ‘Erdalen Event’ or in the following warm period prior to ‘Finse Event’. The blockfield age with 8.40 ± 1.16 ka indicates landform stabilization during ‘Finse Event’, around the onset of the Holocene Thermal Maximum (~8.0–5.0 ka). The paraglacial alluvial fan with its four subsites shows age ranges from 8.51 ± 1.63 to 3.99 ± 1.52 ka. The old exposure age points to fan aggradation follow regional deglaciation due to paraglacial processes, whereas the younger ages can be explained by increasing precipitation during the onset neoglaciation at ~4.0 ka. Surface exposure age of the rock-slope failure with 7.39 ± 0.74 ka falls into a transitional climate period towards the Holocene Thermal Maximum (~8.0–5.0 ka). This indicates that climate-driven factors such as decreasing permafrost depth and/or increasing hydrological pressure negatively influence slope stability. Our obtained first surface exposure ages from boulder-dominated landforms in Rondane give important insights to better understand the palaeoclimatic variability in the Holocene.</p>

scholarly journals The linkage between hillslope vegetation changes and late-Quaternary fluvial-system aggradation in the Mojave Desert revisited

2014 ◽  
Vol 2 (1) ◽  
pp. 181-213
Author(s):  
J. D. Pelletier
Keyword(s):  
Vegetation Cover ◽  
Mojave Desert ◽  
Process Model ◽  
Late Quaternary ◽  
Drainage Density ◽  
Alluvial Fan ◽  
System Response ◽  
Vegetation Changes ◽  
Fluvial System ◽  
Extreme Storm

Abstract. Valley-floor-channel and alluvial-fan deposits and terraces in the southwestern US record multiple episodes of late Quaternary fluvial aggradation and incision. Perhaps the most well constrained of these episodes took place from the latest Pleistocene to the present in the Mojave Desert. One hypothesis for this episode, i.e. the paleo-vegetation change hypothesis (PVCH), posits that a reduction in hillslope vegetation cover associated with the transition from Pleistocene woodlands to Holocene desert scrub generated a pulse of sediment that triggered a primary phase of aggradation downstream, followed by channel incision, terrace abandonment, and initiation of a secondary phase of aggradation further downstream. A second hypothesis, i.e. the extreme-storm hypothesis, attributes episodes of aggradation and incision to changes in the frequency and/or intensity of extreme storms. In the past decade a growing number of studies has advocated the extreme-storm hypothesis and challenged the PVCH on the basis of inconsistencies in both timing and process. Here I show that in eight out of nine sites where the timing of fluvial-system aggradation in the Mojave Desert is reasonably well constrained, measured ages of primary aggradation and/or incision are consistent with the predictions of the PVCH if the time-transgressive nature of paleo-vegetation changes with elevation is fully taken into account. I also present an alternative process model for PVCH that is more consistent with available data and produces sediment pulses primarily via an increase in drainage density (i.e. a transformation of hillslopes into low-order channels) rather than solely via an increase in sediment yield from hillslopes. This paper further documents the likely important role of changes in upland vegetation cover and drainage density in driving fluvial-system response during semiarid-to-arid climatic changes.

Calibrated, late Quaternary age indices using clast rubification and soil development on alluvial surfaces in Pilot Knob Valley, Mojave Desert, southeastern California

2003 ◽  
Vol 60 (3) ◽  
pp. 377-393 ◽  
Author(s):  
John G. Helms ◽  
Sally F. McGill ◽  
Thomas K. Rockwell
Keyword(s):  
Mojave Desert ◽  
Late Quaternary ◽  
Rapid Development ◽  
Slip Rate ◽  
Soil Development ◽  
Alluvial Fan ◽  
Strongly Correlated ◽  
Absolute Age ◽  
Lateral Offset ◽  
Condensed Moisture

AbstractThe orange coating (varnish) that forms on the undersides (ventral sides) of clasts in desert pavements constitutes a potential relative-age indicator. Using Munsell color notation, we semiquantified the color of the orange, ventral varnish on the undersides of clasts from 15 different alluvial fan and terrace surfaces of various ages ranging from less than 500 to about 25,000 yr. All of the surfaces studied are located along the central portion of the left-lateral Garlock fault, in the Mojave Desert of southern California. The amount of left-lateral offset may be used to determine the relative ages of the surfaces. The previously published slip rate of the fault may also be used to estimate the absolute age of each surface. The color of the ventral varnish is strongly correlated with surface age and appears to be a more reliable age-indicator than the percentage coverage of dorsal varnish. Soil development indices also were not as strongly correlated with age, as were the colors of the ventral varnish. In particular, rubification appears to be more useful than soils for distinguishing relative ages among Holocene surfaces. Humidity sensors indicated that the undersides of clasts condensed moisture nightly for a period of several days to over a week after each rain. These frequent wet-dry cycles may be responsible for the rapid development of clast rubification on Holocene surfaces.

Constraining the timing of alluvial fan response to late quaternary climatic changes, southern Tunisia

Geomorphology ◽  
1996 ◽  
Vol 17 (4) ◽  
pp. 295-304 ◽  
Author(s):  
Kevin White ◽  
Nick Drake ◽  
Andrew Millington ◽  
Stephen Stokes
Keyword(s):  
Late Quaternary ◽  
Climatic Changes ◽  
Alluvial Fan ◽  
Southern Tunisia

Soil horizon development and the tempo and modes of vegetation change during the Holocene in a Sonoran Desert basin, USA

The Holocene ◽  
2019 ◽  
Vol 29 (8) ◽  
pp. 1263-1272 ◽  
Author(s):  
Joseph R McAuliffe
Keyword(s):  
Sonoran Desert ◽  
Vegetation Change ◽  
Late Quaternary ◽  
Larrea Tridentata ◽  
Alluvial Fan ◽  
Soil Horizon ◽  
Vegetation Development ◽  
The Holocene ◽  
Perennial Plant ◽  
Soil Features

Silt-rich and clay-rich vesicular horizons (V horizons) that develop beneath desert pavements limit infiltration and plant-available soil moisture. A radiocarbon date from buried charcoal constrains the timing of emplacement of a Sonoran Desert alluvial fan deposit to the very end of the Pleistocene (approximately 12.7 ka). The surface of the fan is dotted with 1.5–3 m light-colored plant scars that mark places once occupied by larger perennial plants. A few very large, ring-like clones of Larrea tridentata have persisted on the surface and represent plants that may have initially established as long ago as the early Holocene. The gravelly fan deposit initially would have possessed high infiltration capacities and fostered the establishment of vegetation. Two principal sets of factors have driven vegetation change over the course of the Holocene. During the first part of the Holocene, differences in life history attributes of various species (dispersal and colonization vs. competitive abilities) would have contributed to a succession of perennial plant occupants, culminating with the predominance of the slow-growing, long-lived, but competitively dominant L. tridentata. During the latter part of the Holocene and continuing to the present, continued development of the pavement and associated V horizon has increasingly diminished the capacity of the surface to absorb precipitation and is responsible for the more recent phase involving progressive elimination of vegetation. Development of soil features that markedly influence soil hydrology is a major component of vegetation change during the late Quaternary in the more arid portions of the Sonoran and Mojave deserts.

Use of Multiparameter Relative-Age Methods for Age Estimation and Correlation of Alluvial Fan Surfaces on a Desert Piedmont, Eastern Mojave Desert, California

1989 ◽  
Vol 32 (3) ◽  
pp. 276-290 ◽  
Author(s):  
Leslie D. McFadden ◽  
John B. Ritter ◽  
Stephen G. Wells
Keyword(s):  
Particle Size ◽  
Mojave Desert ◽  
Late Quaternary ◽  
Complex Interaction ◽  
Alluvial Fan ◽  
Initial Particle ◽  
Initial Particle Size ◽  
Relative Age ◽  
Middle Holocene ◽  
Geomorphic Surfaces

AbstractNumerical and calibrated age determinations of the late Quaternary alluvial fan deposits of the Soda Mountains piedmont in the Mojave Desert provide an opportunity to study the utility of the multiparameter relative-age (RA) method for distinguishing and mapping geomorphic surfaces on a desert piedmont. Most RA parameters could not discriminate between deposits of Holocene age, although pavements have formed over locally significant parts of surfaces as young as middle Holocene. Several parameters, including lithologic composition, particle size, soil development, and varnish cover, permit distinguishing between Holocene surfaces and late Pleistocene surfaces. Statistically significant differences in initial particle size and lithology of the deposits, inferred to be the result of complex interaction among hillslope, alluvial fan, and eolian processes and climatic change, create conditions unfavorable for use of most RA techniques. In contrast, soil-profile development and varnish cover data are successful in discrimination among deposits of Holocene and Pleistocene age. This is attributed to the development of pedogenic features and varnish that are strongly dependent on dust influx and to the relatively minor dependence of these features on differences in the depositional character of the fan.

scholarly journals The linkages among hillslope-vegetation changes, elevation, and the timing of late-Quaternary fluvial-system aggradation in the Mojave Desert revisited

2014 ◽  
Vol 2 (2) ◽  
pp. 455-468 ◽  
Author(s):  
J. D. Pelletier
Keyword(s):  
Vegetation Cover ◽  
Mojave Desert ◽  
Process Model ◽  
Late Quaternary ◽  
Drainage Density ◽  
Primary Phase ◽  
Alluvial Fan ◽  
System Response ◽  
Fluvial System ◽  
Extreme Storm

Abstract. Valley-floor-channel and alluvial-fan deposits and terraces in the southwestern US record multiple episodes of late-Quaternary fluvial-system aggradation and incision. Perhaps the most well-constrained of these episodes took place from the latest Pleistocene to the present in the Mojave Desert. One hypothesis for this episode – i.e., the paleovegetation-change hypothesis (PVCH) – posits that a reduction in hillslope vegetation cover associated with the transition from Pleistocene woodlands to Holocene desert scrub generated a pulse of sediment that triggered a primary phase of aggradation downstream, followed by channel incision, terrace abandonment, and initiation of a secondary phase of aggradation further downstream. A second hypothesis – i.e., the extreme-storm hypothesis – attributes episodes of aggradation and incision to changes in the frequency and/or intensity of extreme storms. In the past decade a growing number of studies has advocated the extreme-storm hypothesis and challenged the PVCH on the basis of inconsistencies in both timing and process. Here I show that in eight out of nine sites where the timing of fluvial-system aggradation in the Mojave Desert is reasonably well constrained, measured ages of primary aggradation are consistent with the predictions of the PVCH if the time-transgressive nature of paleovegetation changes with elevation is fully taken into account. I also present an alternative process model for PVCH that is more consistent with available data and produces sediment pulses primarily via an increase in drainage density (i.e., a transformation of hillslopes into low-order channels) rather than solely via an increase in sediment yield from hillslopes. This paper further documents the likely important role of changes in upland vegetation cover and drainage density in driving fluvial-system response during semiarid-to-arid climatic changes.

scholarly journals Late Quaternary Slip Rate and Kinematics of the Baoertu Fault, Constrained by 10Be Exposure Ages of Displaced Surfaces within Eastern Tian Shan

Lithosphere ◽  
2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Guangxue Ren ◽  
Chuanyou Li ◽  
Chuanyong Wu ◽  
Huiping Zhang ◽  
Siyu Wang ◽  
...  
Keyword(s):  
Late Quaternary ◽  
Active Faults ◽  
Slip Rate ◽  
Alluvial Fan ◽  
Age Dating ◽  
Significant Information ◽  
Total N ◽  
Differential Movement ◽  
Exposure Ages ◽  
Tian Shan

Abstract Investigation on the kinematics and deformation rates about active fault interior of the Tian Shan can provide significant information for strengthening our understanding on the present tectonic evolution of this range. The Baoertu Fault (BETF) is a major E-W striking active structure within the eastern Tian Shan and separates the south and central Tian Shan. But its kinematics and slip rates in the late Quaternary have never been systematically reported before. Based on interpretations of remote sensing images, drone photography, and detailed field investigations, we propose that the BETF is characterized by left-lateral strike-slip faulting with a thrust component and provides the first late Pleistocene slip rate for this fault. At the northern margin of the Kumishi Basin, combining offset reconstructions of displaced alluvial fan surfaces with the terrestrial cosmogenic nuclide (TCN) exposure age dating, we calculate an average sinistral slip rate of 0.65±0.16 mm/yr and average vertical slip rate of 0.07±0.01 mm/yr for the BETF since 95-106 ka. The differential movement eastward between the central Tian Shan block and Yanqi-Kumishi Basin block is likely the dominant driver of the left-lateral slip of the BETF. Synthesizing other quantitative data in eastern Tian Shan, we suggest that the hinterland active faults or folds, including the BEFT, roughly accommodate ~28-45% of the total N-S convergence across the eastern Tian Shan.

scholarly journals Late Quaternary geochronologic record of soil formation and erosion: Effects of climate change on Mojave Desert hillslopes (Nevada, USA)

Geology ◽  
2021 ◽  
Author(s):  
L.P. Persico ◽  
L.D. McFadden ◽  
J.R. McAuliffe ◽  
T.M. Rittenour ◽  
T.E. Stahlecker ◽  
...  
Keyword(s):  
Climate Change ◽  
Mojave Desert ◽  
Vegetation Change ◽  
Climatic Factors ◽  
Late Quaternary ◽  
Perennial Grass ◽  
Soil Development ◽  
Grass Cover ◽  
The Holocene ◽  
Middle Holocene

Climate change is an often-cited control on geomorphic processes in the arid southwestern United States, but links to direct climatic factors and vegetation change remain under debate. Hillslopes at a site in the eastern Mojave Desert in southern Nevada are mantled by 0–1.5 m of colluvial deposits. Accumulation of weathered bedrock combined with eolian inputs of fine sand and silt led to the formation of well-developed soil profiles. Surface sediments from both sources were incorporated into colluvium, allowing both processes to be dated with optically stimulated luminescence (OSL). OSL ages indicate a period of increased colluviation in the Late Pleistocene facilitated by enhanced bedrock weathering and dust deposition. Hillslope aspect strongly controls predominant soil environments and associated vegetation. Well-developed soils with dense grass cover extensively mantle the mesic north-aspect hillslopes, while more xeric south-aspect hillslopes are dominated by thin colluvium with minimal soil development, extensive bedrock exposure, and desertscrub vegetation. Remnants of older colluvium with moderately developed soils on south aspects, however, indicate they were once more extensively mantled by thicker colluvial deposits. The transition to drier conditions in the Holocene diminished vegetation cover on more xeric south aspects, triggering widespread erosion, whereas the more mesic north aspects retained denser grass cover that minimized erosion. The transition to drier conditions in the Holocene altered the vegetation; however, persistent perennial grass cover minimized erosion into the middle Holocene. Increasing aridity during the middle Holocene significantly reduced grass cover on more xeric south aspects, triggering erosion and alluvial deposition. OSL dates of dust incorporated into terrace sediments indicate late Middle Holocene aggradation and soil development in the Late Holocene. In contrast, maintenance of substantial perennial grass cover on mesic north aspects minimized erosion from those hillslopes throughout the Holocene.

Sign in / Sign up

Export Citation Format

Share Document