By Peter J. Haeussler1
Open-File Report 98-480
1U.S. Geological Survey, Anchorage, Alaska
cmfmap.pdfDownload Adobe Acrobat Reader - Adobe Acrobat PDF version of the RTL file above, however it does not have the topographic and cultural base. (2 MB)
cmfmap.ps - postscript file. In order to get this file to print properly, the topo and culture had to be removed (see the discussion of the rtl file). (12.7 MB)
cmfmapmedres.GIF - medium resolution gif. Fills a whole screen. (165 KB)
west.e00 - arc export format coverage of west part of map. (1 MB)
fault_w.e00 - arc export format coverage of faults on west part of map. (50 KB)
west.tif - tif file of topo/culture base for west part of map. (25.8 MB)
east.tfw - world file for georeferencing the east.tif raster topo/culture base (17 KB)
west.tfw - world file for georeferencing the west.tif raster topo/culture base (17 KB)
cmftext.txt - explanitory text that accompanies USGS Open-File Report OF 98-480 (ASCII text format) (33 KB)
The following text is the text from that is printed on the map sheet
After ice of the Elmendorf stade melted, modern stream courses were established. These include the southward flowing streams on the flank of the Talkeetna Mountains as well as the west-southwestward flowing Little Susitna River. The Little Susitna River cut down through older river terrace deposits (Qat) to form the active alluvial plain (Qaa). Alluvium from the southward flowing streams (Qas) forms alluvial fans on top of, and presumably interfingering with, active alluvium along the Little Susitna River.
The Castle Mountain fault has a clearly defined scarp at the west end of the map area. Near its intersection with the Parks Highway, the fault bends by about 3 degrees, and at least one splay of the fault is noticeable here along a linear northern edge of a peat deposit (Qp) adjacent to and southwest of the railroad tracks. The fault extends eastward onto alluvium in older river terraces (Qat) of the Little Susitna River. Its trace is delineated by scarps on the north side of the Little Susitna River, and by outcrop along a stream (Barnes and Sokol, 1959), in the east central part of the western half of the map. It is also notable how a broad dogleg in the Little Susitna River follows the trace of the Castle Mountain fault, which suggests the river course has locally been influenced by the fault. The trace of the Castle Mountain fault is lost at the eastern edge of the western half of the map area, and reappears 19 km farther east in bedrock along Hatcher Pass Road, where it juxtaposes rocks of the Paleocene and Eocene Arkose Ridge Formation with Eocene age rocks of the Wishbone Formation. To the north of the expected trace of the Castle Mountain fault are two linear features that are probably faults (Haeussler, 1994). These are the Lost-in-the-woods fault (not near any named geographic feature) and the Bench Lake fault. The Bench Lake fault has a 1-km-long scarp only at its eastern end, and to the west aligned stream drainages suggest a fault is present, which would imply a 12-km-long fault. The Lost-in-the-woods fault has a 5-km long scarp up to 4-m high cut by all modern stream drainages (Qas), and it is clearly visible on aerial photographs. Both features are located below inferred Naptowne-age lateral-moraine and kame-terrace deposits. Therefore the faults have presumably been active in late Quaternary time. Reger and others (1994b) also acknowledge these features may be related to faulting, but suggests they may be related to glaciofluvial processes. Haeussler (1994) concluded the Bench Lake fault scarp was a more recent feature than the Lost-in-the-woods scarp because (1) the Lost-in-the-woods scarp is dissected by minor streams that do not change gradient as they cross the scarp, whereas the Bench Lake scarp is not dissected, (2) the Bench Lake scarp is more clearly defined and steeper than the Lost-in-the-woods scarp, and (3) the soil profile on the Bench Lake fault is dominated by peat containing plant macrofossils and thus may be more youthful than the soil profile adjacent to the Lost-in-the-woods scarp, which is dominated by humus, in which plant macrofossils have decayed. Finally, there are a number of linear swales to the south of the inferred traces of the Castle Mountain fault at the eastern end of the map area. Most of these appear to be related to bedding surfaces in the underlying bedrock, and are not indicative of fault traces.
Combellick, R.A., Cruse, G.R., and Hammond, W.R., 1994, Trial magnetometer profiles across the Castle Mountain fault, southcentral Alaska: Alaska Division of Geological and Geophysical Surveys Report of Investigations 94-28, 18 p.
Detterman, R.L., Plafker, G., Hudson, T., Tysdal, R.G., and Pavoni, N., 1974, Surface geology and Holocene breaks along the Susitna segment of the Castle Mountain fault, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-618, 1 map sheet, scale 1:24,000.
Detterman, R.L., Plafker, G., Russell, G.T., and Hudson, T., 1976a, Features along part of the Talkeetna segment of the Castle Mountain-Caribou fault system, Alaska: U.S. Geological Survey Miscellaneous Field Studies Map MF-738, 1 map sheet, scale 1:63,360.
Haeussler, P.J., 1994, Possible active fault traces on or near the Castle Mountain fault between Houston and the Hatcher Pass Road: in Till, Alison, and Moore, Thomas, eds., Geologic studies in Alaska by the U.S. Geological Survey, 1993: U.S. Geological Survey Bulletin 2107, p. 49-58.
Karlstrom, T.N.V., 1964, Quaternary geology of the Kenai lowland and glacial history of the Cook Inlet region, Alaska: U.S. Geological Survey Professional Paper 443, 69 p.
Lahr, J.C., Page, R.A., Stephens, C.D., and Fogleman, K.A., 1986, Sutton, Alaska, earthquake of 1984: evidence for activity on the Talkeetna segment of the Castle Mountain fault system: Bulletin of the Seismological Society of America, v. 76, p. 967-983.
Reger, R.D., 1981a, Geology and geologic-materials maps of the Anchorage C-8 SE Quadrangle, Alaska: Alaska Division of Geological and Geophysical Surveys Geologic Report 65, 2 map sheets, scale 1:25,000.
_____, 1981b, Geology and geologic-materials maps of the Anchorage C-8 SW Quadrangle, Alaska: Alaska Division of Geological and Geophysical Surveys Geologic Report 68, 2 map sheets, scale 1:25,000.
Reger, R.D., and Updike, R.G., 1983, Upper Cook Inlet region and the Matanuska Valley, p. 185-263, in P�w�, T.L., and Reger, R.D., eds, Guidebook to permafrost and Quaternary geology along the Richardson and Glenn Highways between Fairbanks and Anchorage, Alaska: Fourth International Conference on Permafrost, Fairbanks, July 18-22, 1983, Field Trip Guidebook 1: Alaska Department of Natural Resources, Division of Geological and Geophysical Surveys, 263 p.
_____, 1989, Upper Cook Inlet region and Matanuska valley, in P�w�, T.L., and Reger, R.D., eds., Quaternary geology and permafrost along the Richardson and Glenn Highways between Fairbanks and Anchorage, Alaska, in 28th International Geological Congress Field Trip Guidebook T102: American geophysical Union, p. 45-54.
Reger, R.D., Combellick, R.A., and Pinney, D.S., 1994a, Geologic and derivative materials maps of the Anchorage C-7 NE Quadrangle, Alaska: Alaska Division of Geological and Geophysical Surveys Report of Investigations 94-24, scale 1:25,000.
_____, 1994b, Geologic and derivative materials maps of the Anchorage C-7 NW Quadrangle, Alaska: Alaska Division of Geological and Geophysical Surveys Report of Investigations 94-25, 2 map sheets, scale 1:25,000.
_____, 1994c, Geologic and derivative materials maps of the Anchorage C-8 NE Quadrangle, Alaska: Alaska Division of Geological and Geophysical Surveys Report of Investigations 94-26, 2 map sheets, scale 1:25,000.
Reger, R.D., Pinney, D.S., and Combellick, R.A., 1994, Geologic and derivative materials maps of the Anchorage C-8 NW Quadrangle, Alaska: Alaska Division of Geological and Geophysical Surveys Report of Investigations 94-27, 2 map sheets, scale 1:25,000.
Schmoll, H.R., and Yehle, L.A., 1986, Pleistocene glaciation of the upper Cook Inlet basin, in Hamilton, T.D., Reed, K.M., and Thorson, R.M., eds., Glaciation in Alaska; The geologic record: Anchorage, Alaska Geological Society, p. 193-218.
Schmoll, Henry R., Szabo, B.J., Rubin, Meger, and Dobrovolny, Ernest, 1972, Radiometric dating of marine shells from the Bootlegger Cove Clay, Anchorage area, Alaska: Geological Society of America Bulletin, v. 83, p. 1107-1113.
U.S. Department of the Interior, U.S. Geological Survey
Maintained by: Carolyn Donlin
Last update: 01/15/2002 (cad)
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