Geology topics
Source-linked reports with geographic coverage including Fairbanks, Alaska.
The preliminary geomagnetic data included here is made available to scientific personnel and organizations, as part of a cooperative effort and on a data exchange basis because of the early need by some users. To avoid delay, all of the data is copied from original forms processed at the observatory; therefore it should be regarded as preliminary.
The preliminary geomagnetic data included here is made available to scientific personnel and organizations, as part of a cooperative effort and on a data exchange basis because of the early need by some users. To avoid delay, all of the data is copied from original forms processed at the observatory; therefore it should be regarded as preliminary.
The preliminary geomagnetic data included here is made available to scientific personnel and organizations, as part of a cooperative effort and on a data exchange basis because of the early need by some users. To avoid delay, all of the data is copied from original forms processed at the observatory; therefore it should be regarded as preliminary.
The preliminary geomagnetic data included here is made available to scientific personnel and organizations, as part of a cooperative effort and on a data exchange basis because of the early need by some users. To avoid delay, all of the data is copied from original forms processed at the observatory; therefore it should be regarded as preliminary.
The preliminary geomagnetic data included here is made available to scientific personnel and organizations, as part of a cooperative effort and on a data exchange basis because of the early need by some users. To avoid delay, all of the data is copied from original forms processed at the observatory; therefore it should be regarded as preliminary.
The preliminary geomagnetic data included here is made available to scientific personnel and organizations, as part of a cooperative effort and on a data exchange basis because of the early need by some users. To avoid delay, all of the data is copied from original forms processed at the observatory; therefore it should be regarded as preliminary.
The preliminary geomagnetic data included here is made available to scientific personnel and organizations, as part of a cooperative effort and on a data exchange basis because of the early need by some users. To avoid delay, all of the data is copied from original forms processed at the observatory; therefore it should be regarded as preliminary.
The preliminary geomagnetic data included here is made available to scientific personnel and organizations, as part of a cooperative effort and on a data exchange basis because of the early need by some users. To avoid delay, all of the data is copied from original forms processed at the observatory; therefore it should be regarded as preliminary.
The preliminary geomagnetic data included here is made available to scientific personnel and organizations, as part of a cooperative effort and on a data exchange basis because of the early need by some users. To avoid delay, all of the data is copied from original forms processed at the observatory; therefore it should be regarded as preliminary.
The preliminary geomagnetic data included here is made available to scientific personnel and organizations, as part of a cooperative effort and on a data exchange basis because of the early need by some users. To avoid delay, all of the data is copied from original forms processed at the observatory; therefore it should be regarded as preliminary.
The preliminary geomagnetic data included here is made available to scientific personnel and organizations, as part of a cooperative effort and on a data exchange basis because of the early need by some users. To avoid delay, all of the data is copied from original forms processed at the observatory; therefore it should be regarded as preliminary.
The preliminary geomagnetic data included here is made available to scientific personnel and organizations, as part of a cooperative effort and on a data exchange basis because of the early need by some users. To avoid delay, all of the data is copied from original forms processed at the observatory; therefore it should be regarded as preliminary.
In 1965, a deep test hole drilled near Eielson Air Force Base, Fairbanks district, Alaska, penetrated 9,774 ft (2,979.1 m) into schists of the metamorphic complex of the Yukon-Tanana Upland. Cores recovered from the test hole show that the section is dominated by calc-magnesian rocks with subordinate pelitic schists. Pelitic mineral assemblages define a progressive increase in metamorphic grade with depth, from the garnet to the kyanite isograd. Diopside first appears in the calc-magnesian schists that were cored at a depth of 9,766 ft (2,976.5 m), indicating the onset of the reaction: Tremolite + 3 calcite -f- 2 quartz→5 diopside + 3CO 2 +H 2 O. Ubiquitous staurolite and rare andalusite occur in the kyanite-bearing pelitic schists. Andalusite appears to have crystallized under postkinematic conditions, and the staurolite is apparently of both synkinematic and postkinematic origin. Hornblende and biotite from calc-magnesian schists sampled at depths of 7,142½ ft (2,176.9 m) and 9,766 ft (2,976.5 m) gave 40 K/ 40 Ar ages of 140±8 and 57.3±1.9 m.y., respectively. The hornblende age is believed to represent the age of the latest synkinematic metamorphism, and the biotite age appears to be an anomalously young one related to the outgassing of argon from biotite at greater depth in the section. Recent experimental data on andalusite-kyanite-sillimanite and staurolite equilibria and the stability field of calcite+quartz+tremolite versus diopside in calc-magnesian rocks suggest that the rocks recovered from the 8,218- to 9,770-ft (2,504.7- to 2,977.7-m) interval were synkinematieally recrystallized at crustal depths of 17 to 19 km and at temperatures of 515° to 580°C; the present thermal gradient (31.5°C/km) is similar to that which accompanied metamorphism in Jurassic time.
East-central Alaska had record floods near Fairbanks following extensive rains of August 8-20, 1967. Precipitation during this period totaled as much as 10 inches, which is close to the average annual precipitation for this area. The most extensive flooding occurred in the White Mountains northeast of Fairbanks and along the major streams draining those mountains. Some of the major streams flooded were the Salcha, Chena, Chatanika, Tolovana, and lower Tanana Rivers, and Birch Creek west of Circle. Peak discharges on some streams in the flood area were from two to four times the probable 50-year flood. The peak discharge of 74,400 cubic feet per second of the Chena River at Fairbanks, from 1,980 square miles of drainage area, was 2.6 times the 50-year flood. The rise of ground-water levels in the Tanana River flood plain to the land surface during the flood caused foundation failures and prevented drainage of subsurface structures. Above-normal ground-water levels existed until the middle of September. Total flood damage was estimated in excess of $85 million. Six lives were reported lost, and about 12,000 persons were evacuated during the flood. This report has been prepared to furnish hydrologic data for development planning. Included are discussions of antecedent streamflow, meteorology of the storm, descriptions of floods, flood damage, flood frequency, ground-water conditions, and stages and discharges of major streams for August 1967.
This report has been compiled from data gathered in the field in September and October, 1966, and from a detailed survey of the various geologic and mining reports on the Fairbanks lode mining district. A number of people who are familiar with mining in this district have provided some additional information, and their help is gratefully acknowledged. The map (fig. 1) and table 1 give an essentially complete coverage of the locations and pertinent geologic data for all lode mines and prospects in this district. Analyses of 101 samples, collected on a reconnaissance basis from dump material and exposures that are available around some of the mines and prospects and from several igneous rock bodies that are closely related to the lode deposits, are given in table 2. The analyses provide data for a preliminary evaluation of the geochemical characteristics of the deposits and the rocks to which they are presumably genetically related, and may be helpful background information for future detailed geologic studies and exploration. The metal contents that are shown in table 2 have not been incorporated in table 1.
A compilation of records of about 450 wells in the Fairbanks area is presented herein. The data were collected by D. J. Cedarstrom and Troy L. Pewe during the first phases of an investigation by the United States Geological Survey of the permafrost, terrain, and water resources of the Fairbanks area. The enclosed map of the area, showing well locations, was prepared by the Regional Sanitary Engineer, Sanitation and Engineering, Alaska Department of Health and Welfare. The data were released to the Survey's open file in 1948, but are reproduced in the Alaska Department of Health and Welfare Hydrological Data series to insure preservation. Where known, the data include for each well the names of the owner and driller; the depth of the well; the depth to the top and bottom of permafrost; and the reported quality of water. The well records and location may be very useful for future subsurface investigations or construction. The well location map was based on the Fairbanks street names as of 1948. Since that time, many of the street names and the numbering system have changed. Hence, the reader should not refer to the address of a particular well, but to the well number when locating a well on the map. The Geological Survey has recompiled the well data in the Fairbanks area for its final phase of a ground-water study. Data through 1954 is to be presented in a Water-Supply Paper now in preparation. Pertinent portions of the enclosed well data will be presented in the forthcoming report. Some of the enclosed well data, and additional well logs, have been published in a report (Pewe, Troy L., 1958, Geology of the Fairbanks (D-2) quadrangle, Alaska: U. S. Geological Survey GQ 110) describing the geology and subsurface conditions in the area.
Seasonal freezing of the ground is common throughout most of the world's land surface. As the ground freezes the surface of the ground may rise--this rising is termed frost heaving. Upward displacement of the ground upon freezing is not due alone to the freezing of water originally contained in the soil voids, but is due mostly to the formation of clear-ice segregations in the sediments. Ice segregations form as water is drawn to points of freezing from adjacent unfrozen ground; the basic physical phenomenon which permits the growth of such segregations is that some water in the ground remains liquid although subjected to temperatures below 0°C, and can therefore move to the growing ice segregations