ABSTRACTS OF PAPERS SUBMITTED FOR MEETING IN ATLANTA, GEORGIA, DECEMBER 27-29, 1955 (SECTION E, AAAS) SEA-ICE ASPECTS OF MODERN ARCTIC SUPPLY OPERATIONS Charles C. Bates U. S. Navy Hydrographic Office, Washington, D. C. To meet the increasing need for better short- and long-term planning for Arctic bases, the U. S. Navy has a rapidly developing reconnaissance and forecasting program for sea ice. This program encompasses the entire American Arctic and is carried on with the co-operation of the United States Air Force; the Snow, Ice, and Permafrost Research Establishment of the U. S. Corps of Engineers; theatre commands; and several Canadian activities. In 1955, the work involved more than 500,000 miles of aerial ice reconnaissance and the preparation of hundreds of ice forecasts ranging in length from 2 to 120 days. The present ice reporting and forecasting system experienced a stiff test off the northern coast of Alaska during 1955 when one of the worst ice years on record was experienced at a time when the shipping effort was at a maximum. MILITARY GEOLOGY REPORTS Lawrence D. Bonham U. S. Geological Survey, Washington, D. C. The writing of reports in the field of military geology differs in several fundamental ways from writing papers for scientific publications. Location and extent of areas for which reports are written are determined by the needs of the military rather than by the interests of the geologist. Although the geology of some of these areas may be very poorly known, one requirement of military geology reports is that an interpretation be made of all parts of the area under consideration. The frequent need for interpretations based on the most meager and indirect evidence, within a definite and often short period of time, calls for the best scientific talent available. However tenuous the arguments, once conclusions have been reached they are presented as positive statements about such matters as the kind of rock to be found in an area and the effects various properties of the rock would have on military operations. Evidence and lines of reasoning on which the conclusions are based, including theories of origin and of geologic history, have no place in the final report. Despite the technical nature of the subject matter, the report must be written for the nongeologist. This gives rise to numerous problems in presenting information as concretely as possible without dis- torting rather precise geological terminology and concepts. POTASSIUM-ARGON AGES OF METAMORPHIC AND IGNEOUS ROCKS FROM THE SOUTHERN APPALACHIANS Donald R. Carr and J. Laurence Kulp Lament Geological Observatory (Columbia University), Palisades, N. Y. Approximate minimum ages have been determined for the Cranberry gneiss, Carolina gneiss, Beech granite, and Henderson gneiss by measuring A40/K40 ratios on samples of the whole rock. Potassium-argon age measurements have also been made on feldspar and mica minerals taken from a number of pegmatites of the Spruce Pine district. The ages obtained show the metamorphic com- plex to be Precambrian. The initial sedimentation in the Southern Appalachians probably goes back to 1 billion years ago. The pegmatite ages agree fairly well with the 330 m.y. value determined by uranium-lead ages and represent the last significant metamorphic event. Possible sources of error and the general reliability of the potassium-argon method are discussed. 1711 Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/66/12/1711/3431788/i0016-7606-66-12-1711.pdf by guest on 29 September 2021 1712 ABSTRACTS EVALUATION OF NATURAL CONDITIONS FOR THE CONSTRUCTION OF UNDERGROUND INSTALLATIONS Edward C. T. Chao U. S, Geological Survey, Washington, D. C. Studies of suitability for construction of underground installations can be made for any selected area of the world using available geologic literature, maps, and photographs. Such studies are neces- sarily generalized and seem particularly suited for planning purposes prior to reconnaissance or de- tailed field surveys. Geologic, topographic, and hydrologic factors are used to evaluate the natural conditions for the suitability of constructing tunnel-type and bunker-type underground installa- tions. The type of information and engineering data needed for construction planning or site selec- tion is discussed. The usefulness and value of such a study depends largely on (1) the abundance and accuracy of the geologic information; (2) the ability of the geologist to correlate geologic data with engineering data; and (3) the presentation of technical data in a form directly usable and under- stood by the planners. Problems of interpretation are included to illustrate the need for basic research in correlating geologic information with engineering data. APPLICATIONS OF HYDROLOGY IN MILITARY OPERATIONS William B. Craig Washington District, Corps of Engineers, 1st & Douglas Sts., N.W., Washington, D. C. Department of the Army, SR 115-15-5 dated 20 December 1949, assigned the Corps of Engineers the responsibility for the collection, analysis, and dissemination of the hydrological data required by the armed forces and the authorization to carry out the necessary research and development thereto. Those functions relating to the collection of special meteorological information were given to the Air Forces. "Artificial Flooding," a most important consideration in an intelligence study, is defined as the increase in flooding over the existing natural flow conditions of a stream or over an area. The tech- niques of creating artificial floods may be classified into three general categories: (1) Increasing streamflow, by breaching a dam or releasing a flood wave by outlet-gate regulation (2) Retarding the streamflow to raise the water surface, by temporary dam construction (3) Creating drainage obstacles, by preventing the drainage of a normally drained area; or flooding a protected area by breaching the levees or opening the tide gates. An example of creating an artificial flood by increasing the streamflow is the breaching of the Moehne and Eder dams in Western Germany. On 17 May 1943 the RAF successfully bombed the dams and flooded the Eder, Fulda, Weser, and Ruhr valleys. More than 1200 lives were lost, and many bridges, power plants, and navigation locks were destroyed. Two examples of artificial flooding by outlet-gate regulation are given by the cyclical flood waves released from the Isoletta Dam in the Rapido-Garigliano River sectors of Italy during January- February 1944 and the flood releases from the Hwachon Dam on the Pukhan River, Korea, in April 1951. The German flooding of the Ay River in Normandy during July 1944, and the 111 River in Alsace during the winter 1944-1945 are examples of retarding the streamflow by temporary damming to augment the defense. Destruction by the Germans of the pump stations draining the Pontine marshes in Italy, 1944, and the British bombing of the protective dikes of Walcheren Island, Netherlands, in 1944 are ex- amples of artificial flooding caused by the creation of two classes of drainage obstacles. The practical application of hydrology to military operations requires the assembly and analysis of hydraulic data for all major drainage basins of the world, far in advance of actual hostilities. The data to be assembled should include the physical description of the river (river-bottom profiles and cross sections), the man-made developments (physical dimensions, shapes, and elevations of the hydraulic structures), and the hydraulic characteristics of the river and structures (discharge rating curves and flow variation). Downloaded from http://pubs.geoscienceworld.org/gsa/gsabulletin/article-pdf/66/12/1711/3431788/i0016-7606-66-12-1711.pdf by guest on 29 September 2021 DECEMBER MEETING OF SECTION E 1713 The physical and hydraulic data are analyzed to determine the artificial flooding potentialities of the river system and submitted to the field commander as engineer studies. Artificial flooding techniques have played an important part in past military operations, and it is important in the future that competent engineers be available to analyze and interpret the hydraulic data for the advanced planning of military operations. MAGNETIC MAP OF DURHAM, NORTH CAROLINA, FAULT TROUGH John Dooley, W. R. Johnson, Jr., and H. W. Straley, III Georgia Institute of Technology, Atlanta, Ga. Restudy of Durham, North Carolina, Triassic basin by geomagnetic investigation leads to addi- tional interpretations: (1) Bordering highs and lows appear to encircle the northern terminus of the structure. (2) The possibility of cross faulting in the neighborhood of the Neuse River, on both sides of the basin, cannot be ignored. (3) As Harrington showed, when he mapped new border faults, the structure of the trough is by no means as simple as earlier workers, including the senior writers, were led to think. LOWER GLACIAL LAKE MISSOULA SEDIMENTS IN MONTANA Portland P. Fox Cleveland, Tenn. Although the silts and fine sands in the upper portion of this former lake are well known and have been described by several authors, there has been little recognition of the type and character of the sediments at the extreme lower portion of the lake because they are largely covered by recent allu- vium or are below present river level. Recent explorations along the Clark Fork River in Montana between Stevens Creek and Bull River have penetrated more than 200 feet of brown, fat, varved clay having a liquid limit of 42-63 per cent. This clay has a dry density of 83 pounds per cubic foot and a natural water content of 31-51 per cent. Locally, a small percentage of the clay is silty and sometimes interbedded with fine sand, but the larger portion of the lake sediments in this area con- sists of a fat clay. RELATION OF MINOR FRACTURES TO THRUST FAULTS Willard H. Grant Emory University, Ga. The faults occur in slightly metamorphosed calcareous graywacke and are composed of a series of narrow mylonitized movement zones separated by much wider zones of rock which range from systematically fractured to brecciated.