Preliminary geologic map of the San Bernardino 30' x 60' quadrangle, California (includes preliminary GIS database)

Morton, Douglas M.; Miller, Fred K.

doi:10.3133/ofr03293

Cited by 14 publications

(36 citation statements)

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“…3 of Nourse (2002). Faults were mapped from Morton and Miller (2003) and the Quaternary fault and fold database of the United States (U.S. Geological Survey and California Geological Survey, 2006). and Rasmussen (2009) model predicts P r values consistent with those reported in the literature from semiarid climates, where P r values typically range from ∼ 30 to 300 m Myr −1 .…”

Section: Introductionmentioning

confidence: 48%

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Quantifying the controls on potential soil production rates: a case study of the San Gabriel Mountains, California

Pelletier

2017

Earth Surf. Dynam.

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Abstract. The potential soil production rate, i.e., the upper limit at which bedrock can be converted into transportable material, limits how fast erosion can occur in mountain ranges in the absence of widespread landsliding in bedrock or intact regolith. Traditionally, the potential soil production rate has been considered to be solely dependent on climate and rock characteristics. Data from the San Gabriel Mountains of California, however, suggest that topographic steepness may also influence potential soil production rates. In this paper I test the hypothesis that topographically induced stress opening of preexisting fractures in the bedrock or intact regolith beneath hillslopes of the San Gabriel Mountains increases potential soil production rates in steep portions of the range. A mathematical model for this process predicts a relationship between potential soil production rates and average slope consistent with published data. Once the effects of average slope are accounted for, a small subset of the data suggests that cold temperatures may limit soil production rates at the highest elevations of the range due to the influence of temperature on vegetation growth. These results suggest that climate and rock characteristics may be the sole controls on potential soil production rates as traditionally assumed but that the porosity of bedrock or intact regolith may evolve with topographic steepness in a way that enhances the persistence of soil cover in compressive-stress environments. I develop an empirical equation that relates potential soil production rates in the San Gabriel Mountains to the average slope and a climatic index that accounts for temperature limitations on soil production rates at high elevations. Assuming a balance between soil production and erosion rates on the hillslope scale, I illustrate the interrelationships among potential soil production rates, soil thickness, erosion rates, and topographic steepness that result from the feedbacks among geomorphic, geophysical, and pedogenic processes in the San Gabriel Mountains.

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Section: Introductionmentioning

confidence: 48%

“…Potential soil production rates inferred from the data of Heimsath et al (2012) are also shown. Lithologic units were compiled using Yerkes and Campbell (2005), Morton and Miller (2003), and fig. 3 of Nourse (2002).…”

Section: Introductionmentioning

confidence: 99%

Quantifying the controls on potential soil production rates: a case study of the San Gabriel Mountains, California

Pelletier

2017

Earth Surf. Dynam.

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“…Observations from steep, bedrock‐dominated portions of the eastern San Gabriel Mountains suggest that this discrepancy may be explained by enhanced weathering in saprolitized bedrock (Dixon, Hartshorn, Heimsath, DiBiase, & Whipple, ) or locally elevated pedogenic rates where thin, patchy soils remain (Heimsath, DiBiase, & Whipple, ). Geologic mapping of the San Gabriel Mountains shows that landslide deposits (Dibblee & Minch, ; Morton & Miller, ) and reworked landslide debris (Scherler, Lamb, Rhodes, & Avouac, ) are a significant component of steep, high relief portions of the landscape (Figure ). Here we consider that soils developed on stored and partially reworked landslide debris may provide an alternative and previously unexplored source of chemical solute that partially explains global observations of high solute fluxes from rapidly eroding landscapes.…”

Section: Introductionmentioning

confidence: 99%

“…The San Gabriel Mountains are a tectonically mountain range in a semi‐arid to sub‐humid climate, located at the northern margin of the Los Angeles basin in southern California (Bull, ). The mountains primarily comprise crystalline plutonic and metamorphic basement units (Morton & Miller, ; Yerkes et al ., ) uplifted since approximately 6 Ma (Nourse, ) by active range‐bounding thrust faults (e.g. the Sierra Madre and Cucamonga fault systems, Crowell, ; McFadden, ; Dolan et al, ; Morton & Miller, ) in a restraining bend of the San Andreas Fault system.…”

Section: Introductionmentioning

confidence: 99%

“…The mountains primarily comprise crystalline plutonic and metamorphic basement units (Morton & Miller, ; Yerkes et al ., ) uplifted since approximately 6 Ma (Nourse, ) by active range‐bounding thrust faults (e.g. the Sierra Madre and Cucamonga fault systems, Crowell, ; McFadden, ; Dolan et al, ; Morton & Miller, ) in a restraining bend of the San Andreas Fault system. Erosion rates determined by low‐temperature thermochronology (Blythe, ) and cosmogenic radionuclides (DiBiase, Whipple, Heimsath, & Ouimet, ) increase with topographic relief, river channel steepness, and mean hillslope angles eastward across the mountains (Spotila & House, ).…”

Section: Introductionmentioning

confidence: 99%

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Storage and weathering of landslide debris in the eastern San Gabriel Mountains, California, USA: Implications for mountain solute flux

Vecchio

Lang

Robins

et al. 2018

Earth Surf Processes Landf

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The weathering of silicate minerals in mountain landscapes provides a critical source of chemical solutes in the global biogeochemical cycles that sustain life on Earth. Observations from across Earth's surface indicate that the greatest flux of chemical solute is derived from rapidly eroding landscapes, where landsliding often limits the development of a continuous soil cover. In this study, we evaluate how weathering of landslide debris deposits may supplement the chemical solute flux from rapidly eroding, bedrock‐dominated landscapes. We present new measurements of depositional surface and soil morphology, soil geochemistry, and luminescence‐based depositional ages from debris stored in Cow Canyon, a tributary to the East Fork of the San Gabriel River in the eastern San Gabriel Mountains of California. Cow Canyon deposits include locally derived debris emplaced by dry colluvial and debris flow processes. Deposits have planar, low‐angle, sloping surfaces with soils exhibiting a greater degree of weathering than nearby soils formed on bedrock. A ~33–40 ka depositional age of Cow Canyon deposits exceeds the estimated recurrence time for the largest landslides in the San Gabriel Mountains, suggesting the stored landslide debris may be a persistent source of chemical solute in this landscape. To quantitatively explore the significance of landslide debris on the landscape solute flux, we predict the flux of chemical solute from bedrock and debris soils using a generic, time‐dependent model of soil mineral weathering. Our modeling illustrates that debris soils may be a primary source of chemical solute for a narrow range of conditions delimited by the initial landslide debris porosity and the comparative soil age. Broadly, we conclude that while landslide debris may be an important local reservoir of chemical solute, it is unlikely to dominate the long‐term solute flux from rapidly eroding, bedrock‐dominated landscapes. © 2018 John Wiley & Sons, Ltd.

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Landslides after wildfire: initiation, magnitude, and mobility

et al. 2020

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In the semiarid Southwestern USA, wildfires are commonly followed by runoff-generated debris flows because wildfires remove vegetation and ground cover, which reduces soil infiltration capacity and increases soil erodibility. At a study site in Southern California, we initially observed runoff-generated debris flows in the first year following fire. However, at the same site three years after the fire, the mass-wasting response to a long-duration rainstorm with high rainfall intensity peaks was shallow landsliding rather than runoff-generated debris flows. Moreover, the same storm caused landslides on unburned hillslopes as well as on slopes burned 5 years prior to the storm and areas burned by successive wildfires, 10 years and 3 years before the rainstorm. The landslide density was the highest on the hillslopes that had burned 3 years beforehand, and the hillslopes burned 5 years prior to the storm had low landslide densities, similar to unburned areas. We also found that reburning (i.e., two wildfires within the past 10 years) had little influence on landslide density. Our results indicate that landscape susceptibility to shallow landslides might return to that of unburned conditions after as little as 5 years of vegetation recovery. Moreover, most of the landslide activity was on steep, equatorial-facing slopes that receive higher solar radiation and had slower rates of vegetation regrowth, which further implicates vegetation as a controlling factor on post-fire landslide susceptibility. Finally, the total volume of sediment mobilized by the year 3 landslides was much smaller than the year 1 runoff-generated debris flows, and the landslides were orders of magnitude less mobile than the runoff-generated debris flows.

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Preliminary geologic map of the San Bernardino 30' x 60' quadrangle, California (includes preliminary GIS database)

Cited by 14 publications

References 0 publications

Quantifying the controls on potential soil production rates: a case study of the San Gabriel Mountains, California

Quantifying the controls on potential soil production rates: a case study of the San Gabriel Mountains, California

Storage and weathering of landslide debris in the eastern San Gabriel Mountains, California, USA: Implications for mountain solute flux

Landslides after wildfire: initiation, magnitude, and mobility

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