[ { "id": "authors:famq8-6tp87", "collection": "authors", "collection_id": "famq8-6tp87", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20191008-101522828", "type": "book_section", "title": "Kelso Dunes", "author": [ { "family_name": "Sharp", "given_name": "Robert P.", "clpid": "Sharp-R-P" } ], "contributor": [ { "family_name": "Cooper", "given_name": "John D.", "clpid": "Cooper-J-D" } ], "abstract": "Kelso Dunes comprise one of the larger dune fields of the California desert. They lie in the east-central Mojave Desert (lat. 34\u00b0 48' N., long. 115\u00b0 43' W.) roughly midway between the respective freeways to Las Vegas and Needles (Fig. 1) and are now easily accessible by well-graded and largely surfaced desert roads from both north (Baker) and south (east of Amboy). The dunes are part of a larger sand sea extending S. 80\u00b0 E. from the sand-source area; a broad alluvial apron periodically flooded by the Mojave River where it debouches from Afton Canyon (Fig. 1).", "publisher": "Society of Economic Paleontologists and Mineralogists", "publication_date": "1982" }, { "id": "authors:5swfc-pf314", "collection": "authors", "collection_id": "5swfc-pf314", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190911-092204074", "type": "book_section", "title": "Comments on Annual Rates of Accumulation in West Antarctica", "author": [ { "family_name": "Sharp", "given_name": "Robert P.", "clpid": "Sharp-R-P" }, { "family_name": "Epstein", "given_name": "Samuel", "clpid": "Epstein-S" } ], "contributor": [ { "family_name": "Davies", "given_name": "William E.", "clpid": "Davies-W-E" }, { "family_name": "Krinsley", "given_name": "Daniel B.", "clpid": "Krinsley-D-B" } ], "abstract": "Several maps have recently been prepared showing annual accumulation over much or all of Antarctica. These maps, based on surface measurements and on interpretations of pit stratigraphy, differ in detail but are reasonably comparable in broad aspects. Data of this type provide the basis for various recent estimates of mean\nannual precipitation in Antarctica ranging from 7 to 20 cm of water, with a median value near 14 and an average of about 11.5 cm. For many reasons, it is important that this figure be as accurate as possible. \n\nWell over five hundred analyses have been made of oxygen-isotope ratios (O^(18)/O^(16)) in snow samples from pits and bore holes at West Antarctic stations. These ratios display variations similar to those believed to be of seasonal origin in other areas. \n\nGreenland for example. If the variations in the accumulated Antarctic snow represent seasonal influences, they suggest annual accumulation rates 20 to 100 per cent higher than determined by other methods. The following comparative values (O^(18)/O^(16)) (determinations in parentheses) illustrate this point: South Pole, 7 (15); Byrd station, 18 (36); Little America V, 15-24 (30); Wilkes satelite, 13 (15). \n\nIt is possible that annual accumulation rates in West Antarctica have generally been underestimated? It has not yet been established that the (O^(18)/O^(16) variations in the accumulated snow and firn or Antarctica are definitely of seasonal origin; some other type of cycle or influence may be represented. However, the consistency and large magnitude of those variations show that they are not the product of mere chance; a basic control of some sort is reflected. In our present state of knowledge seasonal control seems the most likely. \n\nThe short time interval over which surface measurements of accumulation have been made and the uncertainties attending interpretations of pit stratigraphy in Antarctica arc such that every opportunity should be taken to check these methods by independent means, such as (O^(18)/O^(16) variations.", "publisher": "Gentbrugge Assoc. Internat. d'Hydrologie Scientifique", "publication_date": "1962" }, { "id": "authors:9dkgx-r5c73", "collection": "authors", "collection_id": "9dkgx-r5c73", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200115-105115656", "type": "book_section", "title": "Oxygen-Isotope Ratios and Glacier Movement", "author": [ { "family_name": "Sharp", "given_name": "Robert P.", "clpid": "Sharp-R-P" }, { "family_name": "Epstein", "given_name": "Samuel", "clpid": "Epstein-S" } ], "abstract": "The ratio of the common isotopes of oxygen, O\u00b9\u2078 to O\u00b9\u2076, in snow is influenced by the degree of cooling and the amount of condensation experienced by the air masses involved and by the temperature at which precipitations occur. Analyses of firn from the Saskatchewan Glacier, Canada, and the Greenland Ice Sheet show that the individual strata composing an annual firn layer have distinctly different oxygen-isotope ratios which reflect: altitude of accumulation, seasonal influences, differences among individual storms, and subsequent diagenetic changes. Lower precipitation temperatures usually yield lower O\u00b9\u2078/O\u00b9\u2076 ratios. \n\nSamples of ice taken along a centerline profile on Saskatchewan Glacier from the firn limit to the terminus show an irregular trend toward lower O\u00b9\u2078/O\u00b9\u2076 ratios downglacier which is the reverse of the normal precipitation pattern. This could be due to the fact that ice at progressively lower positions on the ice tongue originated at successively higher sites in the accumulation area. If so, the isotope ratios nicely confirm deductions made 60 years ago by Reid concerning flow lines in a valley glacier. Isotope ratios in ice samples from a transverse profile 6.75 km above the terminus of Saskatchewan Glacier indicate that the marginal ice comes from higher parts of the firn area than the center ice. This is partly the result of topographic configuration and partly the result of a lower flow velocity and a higher ablation rate in the marginal zones. A greater dispersion of isotope ratios in closely spaced samples from marginal ice may be due to the steep velocity gradient and greater shear displacements near the margin which bring ice masses of distinctly different composition into juxtaposition. \n\nAlthough a high degree of homogenization has been affected in Saskatchewan Glacier ice by diagenetic changes in the firn or by processes associated with deformation and flowage, identification of vestigial sedimentary layering in the glacier tongue may be possible in some instances by means of oxygen-isotope analyses. The generally higher O\u00b9\u2078/O\u00b9\u2076 ratios in the ice tongue of Saskatchewan Glacier compared to the firn is as yet an unsolved problem perhaps involving diagenetic changes in the firn or alterations associated with flowage. The possibility that they reflect a major climatological change during accumulation of the material composing this glacier seems unlikely. \n\nIsotope ratios in ice samples from the Malaspina Glacier, Alaska, confirm deductions concerning the constitution and structure of this large piedmont sheet made on the basis of earlier field studies. The O\u00b9\u2078/O\u00b9\u2076 ratios show that intensely deformed bands of clean and debris-rich ice probably represent original valley glaciers and medial moraines from far back in the accumulation area. The ratios also confirm that one of the major ice units in the Malaspina consists of material accumulated in sedimentary fashion in the large basin of the upper Seward Glacier. \n\nVariations in oxygen-isotope ratios appear to constitute a parameter of considerable potential value for investigation of glaciers.", "publisher": "IAHS Press", "publication_date": "1958-09" }, { "id": "authors:vdcsy-wmd75", "collection": "authors", "collection_id": "vdcsy-wmd75", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181130-131438657", "type": "book_section", "title": "Objectives of Antarctic Glaciological Research", "book_title": "Antarctica in the International Geophysical Year: Based on a Symposium on the Antarctic", "author": [ { "family_name": "Sharp", "given_name": "Robert P.", "clpid": "Sharp-R-P" } ], "contributor": [ { "family_name": "Crary", "given_name": "A. P.", "clpid": "Crary-A-P" }, { "family_name": "Gould", "given_name": "L. M.", "clpid": "Gould-L-M" }, { "family_name": "Hulburt", "given_name": "E. O.", "clpid": "Hulburt-E-O" }, { "family_name": "Odishaw", "given_name": "Hugh", "clpid": "Odishaw-H" }, { "family_name": "Smith", "given_name": "Waldo E.", "clpid": "Smith-W-E" } ], "abstract": "Antarctic glaciological studies should focus principally upon features unique to the region and upon basic relations of world\u2010wide significance. Antarctic ice is the greatest mass of land\u2010locked water substance on Earth, and determination of its volume by geophysical means is needed with respect to a complete world water inventory, to a determination of Pleistocene eustatic shifts of sea level, and to estimates of possible future shifts of sea level. A prediction is made that ice in East Antarctica may prove to be as much as 3500 to 4000 meters thick and that the average thickness of Antarctic inland ice exceeds 1600 meters. Return of even a part of this water to the oceans has far\u2010reaching geological and economic significance, but changes in Antarctic ice wastage will probably be slow enough and small enough so that the sea level shifts will not be catastrophic. Data on the past, present, and future behavior of this ice will be sought through studies of accumulation and wastage, of firn stratigraphy, of geological evidence for ancient fluctuations, and of pertinent glaciometeorological factors. Identification of annual accumulation layers is essential, and oxygen\u2010isotope ratios (O^(18)/O^(16)) promise to be useful for this and for identifying and indicating the nature and magnitude of earlier secular climatic variations.", "doi": "10.1029/gm001p0027", "isbn": "9781118669204", "publisher": "American Geophysical Union", "place_of_publication": "Washington D. C.", "publication_date": "1956", "pages": "27-35" }, { "id": "authors:ejmye-x4d07", "collection": "authors", "collection_id": "ejmye-x4d07", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200219-155134241", "type": "book_section", "title": "Some Physiographic Aspects of Southern California", "author": [ { "family_name": "Sharp", "given_name": "Robert P.", "clpid": "Sharp-R-P" } ], "contributor": [ { "family_name": "Jahns", "given_name": "Richard H.", "clpid": "Jahns-R-H" } ], "abstract": "Southern California is a land of physiographic abundances, contrasts, and peculiarities. The wide range of geological materials and structures, the considerable differences in climatic environments, the host of geological processes at work, and the recency of diastrophic events are the principal factors responsible.", "publisher": "California Division of Mines and Geology", "publication_date": "1954" }, { "id": "authors:9wb70-21r78", "collection": "authors", "collection_id": "9wb70-21r78", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200220-155654280", "type": "book_section", "title": "Physiographic Features of Faulting in Southern California", "author": [ { "family_name": "Sharp", "given_name": "Robert P.", "clpid": "Sharp-R-P" } ], "contributor": [ { "family_name": "Jahns", "given_name": "Richard H.", "clpid": "Jahns-R-H" } ], "abstract": "The abundance and variety of faults in southern California provide good opportunity for study of landforms created directly by faulting or indirectly by other processes acting upon faulted materials. High-angle gravity faults, high- and low-angle thrusts, and faults with large strike-slip displacement are present (see Chapter IV). Furthermore, all degrees and dates of activity are represented.\nLandforms created by faulting can be classed as primary and secondary, or as original and subsequent (Lahee, 1952, p. 248). Primary features are those formed by actual fault displacement. They are nearly always modified by erosion, but should be classed as primary until completely effaced. Secondary or fault-line features are those formed solely by other processes acting upon faulted materials. \n\nFurther subdivision into initial and modified primary forms and into erosional and depositional secondary forms would be possible, but it is not urged.", "publisher": "California Division of Mines and Geology", "publication_date": "1954" }, { "id": "authors:28e8d-p3n76", "collection": "authors", "collection_id": "28e8d-p3n76", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200221-151117104", "type": "book_section", "title": "The Nature of Cima Dome", "author": [ { "family_name": "Sharp", "given_name": "Robert P.", "clpid": "Sharp-R-P" } ], "contributor": [ { "family_name": "Jahns", "given_name": "Richard H.", "clpid": "Jahns-R-H" } ], "abstract": "In the Mojave Desert of southeasternmost California is a remarkably\nsmooth, symmetrical rock-alluvial dome which takes its name\nfrom Cima on the Union Pacific Railroad. Lawson (1915, pp. 26, 33)\ncited Cima Dome as a prime example of a panfan, but Thompson\n(1929, p. 550) later showed that its upper part is bare rock. Davis\n(1933, pp. 240-243) considered it a fine example of a convex desert\ndome evolved from back-wearing of a fault block, but this concept\nis contradicted by the geological relations (Hewett, 1954), which\nthrow more light on the nature and origin of Cima Dome than do\ngeomorphological theories.", "publisher": "California Division of Mines and Geology", "publication_date": "1954" } ]