Eolian saltation, the transport of sand by the wind, involves a variety of physical processes. A fundamental understanding of saltation requires an analysis starting from the level of the individual sand grain. The complexity of this nonlinear dynamical system compels us to divide the problem into more easily handled decoupled components: the saltating grain-bed impact process, the force of the wind on individual grains, the determination of the wind profile from the spatially averaged force of the moving grains on the air, and the formation of small-scale bedforms: ripples.
\r\n\r\nThe impact of a moving sand grain with a bed of sand is studied with two-dimensional dynamical computer simulations and an experiment propelling single grains onto a sand bed. We find that the result of the impact may be described in terms of the rebound of the incident particle and the ejection of bed grains. The bed grain ejections originate from a localized area around the impact point, and at steps in the surface (elevation changes of one grain diameter) which are more widely distributed; these surface steps we term brinks (downstream-facing) and anti-brinks (upstream-facing).
\r\n\r\nA model for steady-state saltation is proposed which incorporates both aerodynamics and the mechanics of the grain-bed impacts, and balances the losses of saltating particles on impact with the bed by gains due to impact generated bed grain ejections. This model does not require data on blowing sand. Results are obtained which qualitatively agree with existing data. Quantitative tests will require new experiments. We argue that grain-bed impacts, not fluid stresses, are the means for entraining grains in steady-state eolian saltation.
\r\n\r\nThe development of sand surface topography is viewed as a result of surface grain transport (reptation) driven by the impact of high-energy saltating grains onto the bed. The collision and merger of small collections of sand, proto-ripples, lead to the asymptotic development of uniform ripples from an initially smoothed surface. The limiting wavelength is pictured as being determined by statistical fluctuations in the saltating impact flux and/or the shortening of the saltation shadow zone below the mean reptation length during a collision between two ripples. Field observations of developing ripple cross-sectional shapes confirm these ideas qualitatively, and rough calculations of limiting wavelengths agree with existing data.
\r\n", "doi": "10.7907/6cbp-es88", "publication_date": "1987", "thesis_type": "phd", "thesis_year": "1987" }, { "id": "thesis:1284", "collection": "thesis", "collection_id": "1284", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-04072004-154813", "primary_object_url": { "basename": "Conca_jl_1985.pdf", "content": "final", "filesize": 22985051, "license": "other", "mime_type": "application/pdf", "url": "/1284/1/Conca_jl_1985.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Differential Weathering Effects and Mechanisms", "author": [ { "family_name": "Conca", "given_name": "James Louis", "clpid": "Conca-James-Louis" } ], "thesis_advisor": [ { "family_name": "Stolper", "given_name": "Edward M.", "orcid": "0000-0001-8008-8804", "clpid": "Stolper-E-M" } ], "thesis_committee": [ { "family_name": "Stolper", "given_name": "Edward M.", "orcid": "0000-0001-8008-8804", "clpid": "Stolper-E-M" }, { "family_name": "Kamb", "given_name": "W. Barclay", "clpid": "Kamb-W-B" }, { "family_name": "Rossman", "given_name": "George Robert", "orcid": "0000-0002-4571-6884", "clpid": "Rossman-G-R" }, { "family_name": "Sharp", "given_name": "Robert P.", "clpid": "Sharp-R-P" }, { "family_name": "Shoemaker", "given_name": "Eugene Merle", "clpid": "Shoemaker-E-M" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "The physical and chemical characteristics of the two differential weathering effects, case hardening and core softening, are examined to determine their formation mechanisms by investigating several field areas exhibiting differential weathering effects. The terms differential weathering effects, factors, mechanisms, processes, morphologies and their cause and effect relationships are defined in the context of the overall problem.
\r\n\r\nBecause differential weathering effects are defined on the basis of spatial variations in relative and absolute hardness, a portable field instrument has been developed to measure rock hardness as manifested in the abrasion resistance of the material.
\r\n\r\nThe design and operation of the instrument as well as results from standard materials are discussed in light of abrasive wear theory. The way in which the instrument removes material appears dominated by abrasive wear mechanisms. However, the concept of hardness implied by such mechanisms is profoundly different for rock than for homogeneous materials, and the effective hardness calculated for rock material using this instrument is more insensitive to mineralogy than expected, and is sensitive to the character of the intergranular bond.
\r\n\r\nAt the first locality, Valley of Fire, Nevada, cavernous weathering of the Aztec Sandstone results from the differential weathering effect of case hardening. The case-hardened crust is an induration phenomenon consisting primarily of host rock, calcite cement, kaolinite and finegrained quartz. The calcite occurs in a wide range of concentrations (0.001 to 5.0 wt%). The hydrated calcium borate, colemanite, was also found as a non-cementing hardening agent on two outcrops and can be used as a tracer constituent. In all cases kaolinite and quartz were the major constituents of the indurating materials by weight and are necessary components of the crust. Eolian deposition and interaction with meteoric water were determined to be the primary differential weathering mechanism within the Valley of Fire.
\r\n\r\nAt Catavina, Baja California, tonalite exhibiting cavernous weathering is found to be core-softened. Soft cores are more chemically weathered than the exterior rock as indicated by higher kaolinite contents. Hematite formed from the leaching of biotite occurs in coatings on rock surfaces, but the hardening effect of the coating is insignificant compared to the core-softening of the interior. The hardness, measured by the abrasion resistance hardness tester, is inversely correlated with kaolinite content in the tonalite. A one-dimensional water flow model was developed for core-softened, cavernously weathered boulders, and indicates that during infiltration and dessication the moisture flux through a boulder's surface is greatest at the interior cavern wall because of changes in the hydraulic conductivities induced by core softening.
\r\n\r\nThe differential weathering effects developed in the Ferrar dolerite within the Labyrinth of the Dry Valleys, Antarctica are caused by two different mechanisms. The primary mechanism is precipitation of a brown, iron-stained silica coating in the exterior rock of outcrops and joint blocks. This is also true for the case-hardened Beacon Sandstone. Precipitation can occur in the rock's outer few millimeters to centimeters, thereby decreasing the exterior rock's permeability, and consequently its susceptibility to chemical weathering. The coating's effect on a dolerite block's internal moisture regime is modeled for the case of saturated flow, and shows that the contours of the pore water flow mimic subsequent morphology. Weathering of material underlying the coating results in core softening of the dolerite. In dolerite blocks of intermediate size, expansion of the interior owing to weathering can cause the less weathered outer zone to separate into an array of polyhedral cracks. Further weathering and removal of the underlying rock by the combined action of hydration, salt weathering and eolian processes leads to the development of cavernous weathering.
\r\n\r\nA less common differential mechanism occurs in the bottom of the Antarctic Labyrinth troughs in which an eolian polish develops on rock surfaces exposed to the austral winter winds. Development of the polish protects the underlying material with similar, but less dramatic effects, than accompanies the presence of the silica coating.
\r\n\r\nExposures of the Bishop Tuff in the Mono Basin exhibit the differential weathering effect of case hardening. Early devitrification along joint planes to an average depth of 1 cm greatly increased the resistance of the joint faces to weathering over that of the joint block interiors. The absolute and relative hardnesses between interior and exterior change systematically with exposure age, and cavernous weathering results only on outcrops with long enough exposure ages, on the order of ten to twenty thousand years.
\r\n\r\nThe Towel Creek Tuff in Cottonwood Basin, Arizona, weathers into peculiar forms: conical-shaped tepees which show cavernous weathering as a result of case-hardening by calcite precipitation in the exterior rock. Calcite contents of different materials are observed to vary directly with the abrasion hardness of the material. Basal surfaces are formed at the base of the tepees by heterogeneous fluvial erosion and the cavernous hollows are initiated in these zones. Although infiltration of meteoric water into the tepees occurs through all surfaces, moisture flow during dessication of the tepees occurs primarily through the basal surfaces and the lower cavernous hollows. Equilibrium aqueous chemistry limits the interior rock's carbonate content, but calcite can accumulate at the rock exterior.
\r\n\r\nBecause of the overall differences in the intergranular bonding character between crystalline materials such as granite and clastic materials such as sandstone, the results of this study indicate that crystalline rocks tend to core-soften whereas clastic materials case-harden. Clastic materials will be affected by redistribution of secondary cements and greater accumulation at an interface can result in case hardening. In clastic rocks therefore, the hardness of different areas can either increase or decrease with time. On the other hand, a crystalline rock in a weathering environment will have its intergranular and intragranular bonds disrupted by chemical alteration. Spatial variations in disruption can result in core softening or case softening, but the hardness of all areas will decrease with time. Accumulation of secondary cements can often enhance differential effects in crystalline rocks but without case hardening the rock.
\r\n ", "doi": "10.7907/VBEQ-RB90", "publication_date": "1985", "thesis_type": "phd", "thesis_year": "1985" }, { "id": "thesis:3214", "collection": "thesis", "collection_id": "3214", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-08242006-080724", "primary_object_url": { "basename": "echelmeyer-ka_1983.pdf", "content": "final", "filesize": 11189946, "license": "other", "mime_type": "application/pdf", "url": "/3214/12/echelmeyer-ka_1983.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Response of Blue Glacier to a Perturbation in Ice Thickness: Theory and Observation", "author": [ { "family_name": "Echelmeyer", "given_name": "Keith Alan", "clpid": "Echelmeyer-Keith-Alan" } ], "thesis_advisor": [ { "family_name": "Hager", "given_name": "Bradford H.", "clpid": "Hager-B-H" } ], "thesis_committee": [ { "family_name": "Hager", "given_name": "Bradford H.", "clpid": "Hager-B-H" }, { "family_name": "Ahrens", "given_name": "Thomas J.", "clpid": "Ahrens-T-J" }, { "family_name": "Kamb", "given_name": "W. Barclay", "clpid": "Kamb-W-B" }, { "family_name": "Meier", "given_name": "Mark", "clpid": "Meier-M" }, { "family_name": "Sharp", "given_name": "Robert P.", "clpid": "Sharp-R-P" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "A unique natural experiment has occurred on Mt. Olympus, Washington, in which the lower part of Blue Glacier has undergone a marked increase in ice thickness and a general decrease in surface slope. In response to this, the glacier flow velocities have increased considerably. The detailed study of the surface configuration and flow of the glacier during the period 1957-59, before the thickening (Meier, et al., 1974) provides a complete baseline against which the recent changes in geometry and surface velocity field are measured.
\r\n\r\nA detailed evaluation of the flow response to the changes in thickness and slope is made, testing for the existence of a quantitative observational relation among u, H, and \u03b1. A linear relation between the percentage ice thickness change and the percentage velocity increase is found. The slope of this response line is related to the exponent n in the flow law of ice, and the negative intercept represents an overall decrease in surface slope.
\r\n\r\nDetailed quantitative interpretations of the field measurements on the flow of Blue Glacier and its response to the change in surface configuration are made, using analytical and finite-element techniques.
\r\n\r\nA theoretical discussion of the effects of longitudinal stress gradients on the flow of an ice mass is given. This discussion leads to the development of an exponential Green's function which determines the effect of surface slope and ice thickness variations on the flow. This Green's function provides a weighting factor for longitudinal averaging of slope and thickness. The characteristic length scale up- and downglacier is dependent on the longitudinal strain-rate, the amount of basal sliding, and the flow-law parameters, being approximately three times the mean ice thickness. Application of this longitudinal averaging to the observed slope and thickness changes results in a marked decrease in deviations of the response data from a linear regression on the velocity changes, showing that longitudinal stress gradients are important.
\r\n\r\nA finite-element computer code for the calculation of flow of ice in channel cross sections of arbitrary shape, including transverse flow components, is developed. The model is applied to flow in channels of idealized parabolic cross-sectional shape to reveal the basic effects of channel shape and flow-law parameters on stress and velocity distribution. The stresses are found to be dependent on the flow-law parameters. Components of transverse flow within the cross section that develop in response to transverse convexity of the glacier surface were calculated. Comparison with observations shows that much of the splaying of the velocity vectors within an ablation zone can be attributed to flow driven by this convex surface.
\r\n\r\nAnalytical models of the flow of a glacier in which the flow law parameters vary with position are developed. These models show that there is a nonuniqueness in flow-law parameters obtained from borehole deformation studies. Studies of the response of a glacier to a change in surface configuration can partially eliminate some of this ambiguity.
\r\n\r\nThe theory and finite element calculations are extended to channels that follow a curving course in map view, which is necessary for application to Blue Glacier, since in the reach studied the glacier flows around a gently curving bend of 90\u00b0. Longitudinal channel curvature causes asymmetry in the stress and velocity distribution within a symmetric channel. The stress centerline is shifted toward the inside of the bend, while the position of the maximum velocity is usually shifted outward of the center for n \u2265 3. The effects of curvature are readily observable in the flow and crevassing of Blue Glacier.
\r\n\r\nThe relation between perturbations in ice thickness and surface slope and the change in velocity is developed for arbitrary channels. Analytical and numerical results indicate that there is a linear relation between the changes in slope \u03b1, thickness H, and surface velocity u:
\r\n\r\n[Equation included in scanned thesis' abstract, pp. vii]
\r\n\r\nwhere \u03a8 is termed the response factor. For realistic channel geometries, \u03a8 is in the range 1/2 to 1. This factor represents the change in cross-sectional shape of an ice mass which accompanies a change in ice thickness within a given channel. The value of the stress exponent inferred from the observed flow response is significantly affected by this geometric factor, which is approximately equal to 0.82 for Blue Glacier. The slope of the response line implies that n = 4 for the flow of Blue Glacier when this response factor is taken into account.
\r\n\r\nFinite element models of flow and the flow response within the different cross sections of Blue Glacier (as determined by radio echo sounding) compare well with the observed velocity patterns and response to change in thickness if channel curvature is included. These results again imply a stress exponent of n = 4. The results also agree with the various field measurements which indicate that basal sliding contributes at most 10% to the overall motion of the glacier.
\r\n\r\nThe results presented in this thesis represent the most detailed evaluation of the response of a glacier to perturbations in ice thickness and surface slope. They show that non-linear flow theory with n = 4 is applicable to a good approximation. The relationship between the flow velocity, slope, and thickness found in this work has direct application to the study of effects of climatic change on an ice mass.
", "doi": "10.7907/ZQHK-NA29", "publication_date": "1983", "thesis_type": "phd", "thesis_year": "1983" }, { "id": "thesis:1324", "collection": "thesis", "collection_id": "1324", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-04102003-122837", "primary_object_url": { "basename": "gillespie_ar_1982.pdf", "content": "final", "filesize": 50336898, "license": "other", "mime_type": "application/pdf", "url": "/1324/14/gillespie_ar_1982.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Quaternary Glaciation and Tectonism in the Southeastern Sierra Nevada, Inyo County, California", "author": [ { "family_name": "Gillespie", "given_name": "Alan Reed", "clpid": "Gillespie-Alan-Reed" } ], "thesis_advisor": [ { "family_name": "Ahrens", "given_name": "Thomas J.", "clpid": "Ahrens-T-J" } ], "thesis_committee": [ { "family_name": "Ahrens", "given_name": "Thomas J.", "clpid": "Ahrens-T-J" }, { "family_name": "Allen", "given_name": "Clarence R.", "clpid": "Allen-C-R" }, { "family_name": "Sieh", "given_name": "Kerry E.", "orcid": "0000-0002-7311-2447", "clpid": "Sieh-K-E" }, { "family_name": "Sharp", "given_name": "Robert P.", "clpid": "Sharp-R-P" }, { "family_name": "Wasserburg", "given_name": "Gerald J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Clark", "given_name": "M. M.", "clpid": "Clark-M-M" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "The southeastern Sierra Nevada consists of three geographic regions. From west to east, they are: an upland region across the crest, a steep east-facing escarpment along which Owens Valley has partly subsided, and foothill blocks intermediate to the Sierra Nevada and Owens Valley. Farther east, Owens Valley is a deep graben separating the Sierra Nevada and the Inyo Range.
\r\n\r\nThe main goals of this thesis were the detailed mapping of Quaternary glacial and other deposits in these regions, dating of critical events, and geomorphic analysis of the range front. The focus was on Pleistocene moraines near the range front. The motivation of this research was to improve our understanding of the chronology of Pleistocene events, to characterize details of the tectonic history of the Sierra, to infer faulting, erosion, and deposition rates, and to provide a basis for the comparison of the Quaternary geology in the southeastern Sierra and in more intensively studied regions in the central and northern Sierra and elsewhere.
\r\n\r\nThe study area extended from the alluvial fans of Owens Valley west to the Sierra crest from latitude 36\u00b045' N to 37\u00b000' N. It included the southern part of the Big Pine volcanic field, an eruptive center for basaltic lavas for most of the Pleistocene Epoch. Elevations within the study area ranged from about 1000 m (Owens Valley) to about 4000 m (peaks along the crest).
\r\n\r\nThroughout the study area the principal rocks are granodiorite and quartz monzonite of Cretaceous age. Plutons are rather small, and individual drainages generally include more than one. In the southern part of the study area, Jurassic-Triassic metavolcanic rocks are found as roof pendants. These rocks, originally ranging in composition from basalt to rhyolite, are most common near the Sierra crest. In the northern canyons of the study area, Paleozoic metasedimentary rocks including sandy marbles and biotite schist replace the metavolcanic pendants. The foothill blocks are identical to the Sierras in composition.
\r\n\r\nBelow the foothills coalescing alluvial fans grade a few km east to the alluvium and lacustrine sediments of the Owens River and Owens Lake. These sediments have been shown in geophysical studies to mask a second escarpment as high as the one of the range front, and the total bedrock relief from the Sierra crest to the floor of the graben is as much as 6 km.
\r\n\r\nDuring the Quaternary Period the southeastern Sierra Nevada was characterized by the down-faulting of Owens Valley along two zones, one a series of normal faults along the range front (Independence Fault) and the other a series of faults along the center of the valley (Owens Valley fault zone). This same period has seen the cutting of deep canyons through the 2-km-high escarpment. During repeated glaciations these canyons were widened and deepened. Traces of at least seven glaciations were found during this study. Moraines and other deposits left during these glaciations could be distinguished based on the degree of weathering of granitic clasts, vegetative cover, and morphologic characteristics. Absolute age limits were obtained for two of the Pleistocene glaciations by radiometric dating of basalt flows interfingered with the moraines.
\r\n\r\nThree of the recognized glaciations, probably corresponding to the Matthes, Recess Peak, and Hilgard neoglaciations found by J.H. Birman in the central Sierra Nevada, occurred during the Holocene Epoch. The youngest glaciers (Matthes glaciation) left unconsolidated and unvegetated till in stagnant rock glaciers and moraines in cirques on high peaks. Some rock glaciers are still ice-cored. Extending out from the cirques and into the upper reaches of the canyons are moraines correlating to the Recess Peak glaciation. Till is generally consolidated and supports heavy lichen growth and bushes but few trees. The oldest Holocene glaciation (Hilgard) left few large moraines in the study area. Hilgard glaciers extended much farther down-canyon than the younger Holocene glaciers, sometimes within one or two km of the Tioga terminal moraines. Those Hilgard terminal moraines which were found have been barely breached by streams. Moraines tend to be heavily forested, and lakes are largely unsedimented. The Hilgard glaciation may have simply been the last stade of the Tioga glaciation from the evidence found in this study.
\r\n\r\nAt least four Pleistocene glaciations occurred in the southeastern Sierra Nevada. All four postdate most of the significant incision of streams through the escarpment. The three youngest probably correlate with the Tioga, Tenaya, and Tahoe stages (in order of increasing age) recognized throughout the Sierra. In each case, moraine morphology has been well preserved. Tioga moraines were found down to about 2200 m elevation. Nested sets of moraines were common. The terminal moraines of the youngest of these were sometimes intact. lakes were rare; one (Sawmill Meadow) was completely sedimented. Granitic boulders in the moraines were largely unweathered. Weathering of boulders in Tenaya moraines was similar, but a small fraction of granitic boulders were grusy. Boulders from Tahoe moraines were conspicuously weathered, and the moraines themselves were rounded and gullied.
\r\n\r\nThe oldest group of moraines probably significantly predates the Tahoe glaciation. It is nevertheless post-Sherwin. Moraines in this group were found in five of the eight canyons studied. While obviously eroded, these moraines still retained their original shape. All surficial boulders were heavily weathered, but some exposed in road cuts were fresh. No moraines of Sherwin age were identified, although Sherwin till is widespread only a few km to the north. However, on plateaus and ridges 200 to 300 m above the modern canyons near the Sierra crest were found ancient diamictons, some of which could be till. Remnants of U-shaped valleys preserved as high passes across the crest or as cols between canyons east of the crest may be testimonials to ancient glaciers of Sherwin age or older.
\r\n\r\nRadiometric dating (40Ar - 39Ar) of basalts interfingered with moraines in Sawmill Canyon provided a new upper limit of 0.12 my for a moraine of the Tahoe glaciation, and a range of 0.13 - 0.46 my for one pre-Tahoe glaciation. These results confirm that the Tahoe glaciation occurred during the Wisconsin stage of the continental ice age, and conclusively demonstrate the existence of pre-Wisconsin glaciers in the southern Sierra. Relative dating based on acoustic wave speeds through weathered boulders on the moraines indicates the age of the pre-Wisconsin moraine may be close to the upper limit.
\r\n\r\nAlluvial fans appear to have aggraded early in the Wisconsin glaciation (Tahoe glaciation). Subsequently, the fan heads have been incised and the locus of deposition has moved eastward down the fans. The Tenaya and Tioga glaciers during the late Wisconsin stage left outwash plains and terraces along streams cut into the older fans, but aggradation during these events was considerably less than earlier.
\r\n\r\nThree ages of fans were found. The oldest fanglomerate probably is pre-Wisconsin and is exposed in regions protected from later deposition. The heavily weathered fan deposits of this group overlie basalts which appear to be contemporaneous with dated 1.1 - 1.2 my-old basalts nearby. In the middle elevations of the fans, roughly 10 m of fanglomerate was deposited over the old fanglomerate, probably during the Tahoe glaciation. Deposition rates probably are about 0.1 mm/y for the late Pleistocene Epoch. The extent and distribution of the youngest fans (Tenaya-Tioga) are variable, but they are generally found downstream from the incised Tahoe fan heads.
\r\n\r\nFaulting along the range front appears to have been dip-slip only. The offset rate along the range-front faults was determined at several canyons where the fault crossed dated moraines or lava flows. At least during the Wisconsin glaciation faulting on this zone appears to have been erratic, with rates ranging from zero to 0.5 mm/y or more. Offset moraines and terraces at Independence Creek indicated a faulting rate of 0.1 mm/y. Only a few km to the north, Tahoe moraines of both forks of Oak Creek were not offset at all, although scarps could be seen on adjacent hillsides. At Sawmill Creek an offset lava flow gave a lower limit of 0.5 mm/y. It seems that during the late Pleistocene Epoch, offset on the range front faults has been less than on the mid-valley faults east of the study area. Geodetic studies have suggested modern strain rates of 2.2 mm/y for the Owens Valley fault zone.
\r\n\r\nBasalts found in canyons through the escarpment and on terraces and ridges in the foothills to the east document stream erosion during the Pleistocene Epoch. Ridgetop basalts, dated at 1.2 my, stand at least 125 m above the modern streams through the foothills. This indicates an erosion rate of ~ 0.1 mm/y. A comparable rate of ~ 0.15 mm/y for the last 0.46 my was found for Sawmill Creek within the Sierra Nevada. Thus at least during the late Pleistocene Epoch erosion rates in the Sierra and in the foothills have been similar.
\r\n\r\nPatches of boulders and gravels atop the basalt show that some time after 1.2 my BP the foothill block was submerged by alluvial fans. Incision may have begun in response to the inception or renewal of subsidence of the graben along the Owens Valley fault zone.
\r\n\r\nExtensive volcanism in the Big Pine Volcanic field appears to have begun at least 1.2 my ago, and has continued sporadically up to perhaps 0.05 my ago. Minor eruptions may have occurred more recently.
\r\n\r\nThe eastern escarpment of the Sierra Nevada consists of two zones of truncated ridges. Within the study area, the upper zone is about 950 m high; the lower is about 750 m high. Triangular facets of the upper zone have a gradient of only ~ 24\u00b0, lower than slopes of ~ 29\u00b0 in the lower zone. This could be explained if subsidence of Owens Valley along the range-front faults occurred in two great pulses.
\r\n\r\nBoth absolute and relative dating methods were refined for this study. Absolute dating of the K-poor basaltic lavas was done indirectly, by 40Ar - 39Ar analysis of K-rich granitic xenoliths found in the lava. These ancient xenoliths were partially degassed of their accumulated 40Ar during heating in the magma, and it proved possible to date this heating event.
\r\n\r\nIn addition to conventional relative dating methods, a new quantitative approach based on the speed of acoustic waves through individual clasts in a deposit was investigated. This method had been used only once before, on terrace deposits. The technique proved to be very useful, and was capable of discriminating moraines successfully in well-studied canyons in the central Sierra. Acoustic wave speeds may be controlled by the abundance of intergranular cracks in granitic boulders. If this is the case, then this technique relies on different processes than those exploited by conventional methods of relative dating. The successful application to moraines in this study enhances our ability to analyse glacial sequences and complements conventional semi-quantitative methods of relative dating.
", "doi": "10.7907/GNES-QH83", "publication_date": "1982", "thesis_type": "phd", "thesis_year": "1982" }, { "id": "thesis:2718", "collection": "thesis", "collection_id": "2718", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-06242009-141311", "primary_object_url": { "basename": "Smith_rsu_1976.pdf", "content": "final", "filesize": 32480924, "license": "other", "mime_type": "application/pdf", "url": "/2718/1/Smith_rsu_1976.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Late-Quaternary Pluvial and Tectonic History of Panamint Valley, Inyo and San Bernardino Counties, California", "author": [ { "family_name": "Smith", "given_name": "Roger Stanley Uhr", "clpid": "Smith-Roger-Stanley-Uhr" } ], "thesis_advisor": [ { "family_name": "Sharp", "given_name": "Robert P.", "clpid": "Sharp-R-P" } ], "thesis_committee": [ { "family_name": "Sharp", "given_name": "Robert P.", "clpid": "Sharp-R-P" }, { "family_name": "Albee", "given_name": "Arden Leroy", "clpid": "Albee-A-L" }, { "family_name": "Allen", "given_name": "Clarence R.", "clpid": "Allen-C-R" }, { "family_name": "Smith", "given_name": "George I.", "clpid": "Smith-G-I" }, { "family_name": "Rossman", "given_name": "George Robert", "orcid": "0000-0002-4571-6884", "clpid": "Rossman-G-R" }, { "family_name": "Birman", "given_name": "Joseph Harold", "clpid": "Birman-J-H" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "Panamint Valley was filled to overflowing on five, possibly six, separate instances, fed largely by runoff from the Sierra Nevada discharged through Owens and Searles lakes. These high water levels are best represented by uplifted lake terraces and associated deposits at Pleasant Canyon on the, west face of the Panamint Range, where shorelines at five, possibly six, levels have formed with respect to the level of Wingate Pass, (present elevation 1977 \u00b11 feet) into Death Valley. The level of this sill seems to have been tectonically stable, but was permanently raised about 50 feet by a mudflow which poured into the pass during a long-lasting lake stage, herein named Gale Stage. Paired Gale-Stage shorelines, attributed to lake stands stabilized at pre- and post-mudflow sill levels are found throughout Panamint Valley. The lower shoreline is 1.26 times older than the higher, more prominent shoreline, based on 1.26 times greater tectonic deformation at most localities. On the rising range block at Pleasant Canyon, the higher shoreline seems superposed on the lower to form a composite shoreline at 2177\u00b110 feet elevation. Shoreline elevations at Pleasant Canyon (and probable uplift they experienced) are: 2410\u00b110 feet (480\u00b125 feet); 2298\u00b110 (368\u00b125); 2265\u00b110 (335\u00b125); 2177\u00b110 (247\u00b125 to 200\u00b111); 2127\u00b110 (150\u00b111); and 2040\u00b140? (63\u00b141?). If the long-term uplift rate has been constant, the age of each shoreline should be proportional to its height above its sill level. Relatively steady deformation rates throughout Panamint Valley are suggested by the constant proportion (1.26:1.00) of deformation between the older (lower) and younger (higher) Gale-Stage shorelines.\r\n\r\nA radiocarbon age of 31,150\u00b11400 B.P. on snail shells establishes a minimum age for the shoreline at 2127 feet. Extrapolation using steady uplift rates indicates the following youngest-possible ages (in thousands of years) for the other uplifted shorelines: 2410 ft: 100\u00b117; 2298 ft: 77\u00b114; 2265 ft: 70\u00b113; 2177 ft: 52 to 42\u00b17; and 2040 ft?,: 14\u00b110?. The probable age of each lake stage is about 20 per cent greater than its youngest possible age, a judgement based on correlation with the stages of Searles Lake (G.I. Smith, 1968).\r\n\r\nThe higher, younger Gale-Stage shoreline is prominent throughout Panamint Valley. Differential tectonic deformation of this feature amounts to about 370 feet, as established by a maximum elevation of 2190\u00b110 feet on the central Panamint Range to a minimum of 1820\u00b120 at Panamint Valley's north end. Deformation involves differential north- south warping of crustal block on both sides of the Panamint Valley and Ash Hill fault zones, which respectively define the east and west margins of Panamint Valley.\r\n\r\nRight-lateral displacement of Quaternary features along the Panamint Valley fault zone exceeds their vertical, offset. Sixty feet of right-lateral offset have occurred since desiccation of the last, low lake to occupy Panamint Valley (15,000\u00b15,000 B.P.), and cumulative offset of a sheet of monolithologic (landslide?) breccia of Plio-Pleistocene age from its probable source in Wildrose Canyon may total 10,000 to 15,000 feet.\r\n\r\nPanamint Valley is abruptly and massively closed at its north end, where valley-floor deposits appear to underthrust Mesozoic plutonic rocks of Hunter Mountain along a northwest-trending zone which may represent the northwestward continuation of the Panamint Valley fault zone. Along the middle part of this reach of the zone, poorly-sorted (talus?) rubble of sound crystalline boulders underlies a 50 to 100-foot-thick zone of crushed crystalline rock which dips 17 to 35 degrees to the northeast beneath unshattered crystalline rocks. Thrusting may reflect a response to regional northwest-southeast right-lateral shear, possibly imposed upon classical Basin-Range bounding faults. The complex pattern of warping and faulting throughout the rest of Panamint Valley is also consistent with right-lateral shear, and the valley itself may have originated as a right-lateral \"pull apart\".\r\n\r\nThe unusually large volume of deposits along the 2177-foot shoreline suggests correlation with the Sierra Nevada Tahoe glaciation, which is distinguished by unusually large moraines. The small volume of 2127-foot shoreline deposits suggests correlation with the Tenaya glaciation, whose moraines are small. Thus the queried 2040-foot shoreline could represent the Tioga glaciation and the 2410-foot shoreline the Mono Basin glaciation. The 2265 and 2298-foot shorelines may represent early Tahoe events, suggesting that the Tahoe may be divided into early and late phases. Tentative ages of glaciations, based on correlation with pluvial events in Panamint Valley, are (in thousands of years B.P.): Mono Basin: 120\u00b120; Tahoe (early): 92\u00b115 to 78\u00b115; Tahoe (late): 65\u00b113 to 48\u00b110; Tenaya: 38\u00b16; Tioga?: 23\u00b110?.", "doi": "10.7907/W934-HC84", "publication_date": "1976", "thesis_type": "phd", "thesis_year": "1976" }, { "id": "thesis:14013", "collection": "thesis", "collection_id": "14013", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:12042020-203212461", "type": "thesis", "title": "Scour and Fill in Ephemeral Streams", "author": [ { "family_name": "Foley", "given_name": "Michael Glen", "clpid": "Foley-Michael-Glen" } ], "thesis_advisor": [ { "family_name": "Sharp", "given_name": "Robert P.", "clpid": "Sharp-R-P" } ], "thesis_committee": [ { "family_name": "Vanoni", "given_name": "Vito A.", "clpid": "Vanoni-V-A" }, { "family_name": "Brooks", "given_name": "Norman H.", "clpid": "Brooks-N-H" }, { "family_name": "Dix", "given_name": "Charles Hewitt", "clpid": "Dix-C-H" }, { "family_name": "Sharp", "given_name": "Robert P.", "clpid": "Sharp-R-P" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "The classical concept that mean bed elevation over an entire stream reach is lowered by scour during flood-wave passage and is re\u00adstored by deposition in the waning flood phase (mean-bed scour and fill) can be challenged. The alternative that both scour and fill occur concurrently at different migrating loci within a reach (local scour and fill) is more consistent with published field data. The field and laboratory investigations reported herein suggest that mean-bed scour and fill in a uniform channel is minor compared to local scour and fill caused by bedform migration, and that maximum local scour and fill may occur on the waning flood in some instances.
\r\n\r\nThe field experiment, utilizing a rectilinear array of buried maximum-scour indicators (scour-cords), produced data for contouring of maximum scour and fill in an ephemeral streambed during two floods. In the first flood, 24 cm of scour and fill was measured for a bankfull flow depth of 23 cm.\tIn the second, maximum scour and fill was at least 66 cm for a bankfull flow depth of 34 cm.
\r\n\r\nEstimates of antidune amplitudes for the two floods, based on theoretical models and laboratory and field observations, are 28 to 64 cm and 48 to 97 cm, respectively. This indicates that all scour and fill measured by the scour-cord array could have been caused by antidune migration.
\r\n\r\nLaboratory experiments were conducted in an 18 m-long open-circuit flume with automated sediment and water input-rate controls. A series of experiments in a 26.7 cm-wide sand-bed channel with rigid walls, at grade for a simulated flood patterned after those typical of ephemeral streams, showed that mean-bed scour and fill was less than 3 percent of local scour and fill. For these experiments, mean sand size was 0.3 mm, channel slope was .009, maximum water depth was 40 mm, maximum local scour and fill was 22 mm, and maximum mean-bed scour and fill was 0.6 mm.\tMaximum mean bed elevation variation was thus only two sand-grain diameters. Fill occurred at peak flow followed by scour to the pre-flood mean bed elevation on the waning flood. Maximum local scour and fill took place near the end of the simulated floods, when bedform amplitudes were the greatest.
\r\n\r\nA series of simulated-flood experiments in a sand-bed channel with erodible sand banks showed scour and fill behavior qualitatively similar to that of the rigid-wall channel. Bank erosion, channel meandering, and braiding prevented quantitative scour and fill measurements in these alluvial-bank experiments. Measured flow and bedform parameters and scour and fill data derived from small laboratory scour-chains were compatible with those estimated from the theoretical model used in the field experiment.
", "doi": "10.7907/gbn5-jb14", "publication_date": "1976", "thesis_type": "phd", "thesis_year": "1976" }, { "id": "thesis:4399", "collection": "thesis", "collection_id": "4399", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-11042002-153232", "primary_object_url": { "basename": "Watson_k_1964.pdf", "content": "final", "filesize": 4070255, "license": "other", "mime_type": "application/pdf", "url": "/4399/1/Watson_k_1964.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "I. The Thermal Conductivity Measurements of Selected Silicate Powders in Vacuum from 150\u00b0 to 350\u00b0 K. II. An Interpretation of the Moon's Eclipse and Lunation Cooling as Observed through the Earth's Atmosphere from 8-14 Microns", "author": [ { "family_name": "Watson", "given_name": "Kenneth", "clpid": "Watson-Kenneth" } ], "thesis_advisor": [ { "family_name": "Brown", "given_name": "Harrison", "clpid": "Brown-Harrison" }, { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" } ], "thesis_committee": [ { "family_name": "Press", "given_name": "Frank", "clpid": "Press-F" }, { "family_name": "Wasserburg", "given_name": "Gerald J.", "clpid": "Wasserburg-G-J" }, { "family_name": "Sharp", "given_name": "Robert P.", "clpid": "Sharp-R-P" }, { "family_name": "Brown", "given_name": "Harrison", "clpid": "Brown-Harrison" }, { "family_name": "Murray", "given_name": "Bruce C.", "clpid": "Murray-B-C" } ], "local_group": [ { "literal": "div_gps" } ], "abstract": "An apparatus was constructed to measure the thermal conductivity of powders in vacuum from 150\u00b0 to 350\u00b0K. It was found that the conductivity of selected silicate powders can be adequately represented, within the experimental errors, by a temperature independent term related to the contact conduction plus a temperature cube term which is due to radiative transfer between and through the grains. The conductivity for glass spheres approximately suggests an inverse grain size dependence and does not appear to be related in any simple manner to the elastic contact area between the spheres. The effects of angular grains, produced by crushing, and limited chemical composition range are not significant when compared with the experimental errors. The radiative transfer term which is grossly independent of chemical composition and grain texture is dominated by radiation between the grains for grain sizes > 300 \u03bc. Radiation through the grains is significant for grain sizes < 100 \u03bc.
\r\n\r\nPrevious interpretations of the eclipse observations of Pettit and Nicholson indicate that homogeneous constant thermal property models provide an adequate fit. The recent lunation observations of Murray and Wildey cannot be adequately explained by homogeneous models with either constant thermal properties or with thermal properties which are based on the results of this experimental investigation and existing specific heat data. It is suggested that the possibility of layering can best be examined in the region of the morning terminator.
\r\n", "doi": "10.7907/7HDE-1M52", "publication_date": "1964", "thesis_type": "phd", "thesis_year": "1964" } ]