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HomeMy WebLinkAboutLiterature Review and Recommendations - Amanda Kolker UAFNaknek – King Salmon area Geology: Literature Review and Recommendations for Future Work Prepared by: Amanda Kolker, University of Alaska Fairbanks 10/29/2006 Background The Alaska peninsula is an active convergent plate margin (subduction zone) that is associated with recent volcanism and deep faulting. The peninsula is therefore a promising area for geothermal exploration. There are no known geothermal expressions (e.g., hot springs, fumaroles) in the study area. The closest known potential geothermal resource area (PGRA) is located at Gas Rocks, on the south shore of Becharof lake; but further exploration work would be necessary before this resource is deemed viable for energy use. Other identified geothermal resource areas are given in a report by the author to NEA (Kolker, 2006). Gas Rocks and all other potential and known geothermal resources in Northern Alaska peninsula lie within federal lands (Becharof National Wildlife Refuge, Katmai National Park and Preserve). Surface Geology King Salmon and Naknek lie in the Nuchagak-Bristol Bay Lowland. The lowland is characterized by quaternary alluvium deposits. The village of Naknek sits atop glacial drift deposits and outwash deposits. Drift deposits consist of unsorted, angular rock debris within cirques and valleys less than 3 km from modern glaciers; outwash deposits are poorly sorted sand and gravel forming plains in front of moraines (Riehle & Detterman, 1993). The King Salmon sits atop outwash deposits characterized by morainal topography (PDC, 2000). The depth to bedrock (i.e., the thickness of the unconsolidated deposits) is unknown for the entire area. Water wells drilled in the King Salmon area to a depth of 320 ft. did not reach bedrock (Thomas, 2006), and bedrock is not exposed in the bluffs along the Naknek River near King Salmon (PDC, 2000). It is reasonable to assume that the deposit thickness increases in a westerly direction; therefore the depth to bedrock in the Naknek area should be even greater. Subsurface Structure Since the area is covered with thick deposits of unconsolidated sediments, subsurface geologic structures (such as faults, fractures, bedrock contacts, etc.) are “buried” and therefore unknown. The Bruin Bay fault is the closest known deep structure. The fault branches off the Castle Mountain fault around Mt. Susitna, near Anchorage, and runs NE-SW to terminate at an unknown location. Some workers believe it terminates in Upper Ugashik lake (Haeussler & Saltus, 2004, Power et al). Others speculate that the fault extends all the way to Aniakchak volcano near Port Heiden (Church et al, 1989). A line due east of King Salmon would intersect the surface fault trace at approximately 55 miles (Riehle et al, 1993). The type of fault and degree of offset is unknown for the Bruin Bay fault, but it has been hypothesized to be a major reverse (thrust) fault that dips 45-80° to the northwest. It has had a number of small epicenters associated with it, including a magnitude 7.3 earthquake in 1943 (Power et al). The Bruin Bay Fault parallels several others to the east of the Alaska peninsula, and is undoubtedly related to the subduction of the Pacific plate under the North American plate. The Lake Clark fault, which runs parallel to the Bruin Bay fault at its northern end, is a major right-lateral strike-slip fault that has had ~26 km offset over the last 34-39 million years. Its southern extent is not known but the elongation direction of Bristol Bay and the direction of the Kvichak river follow its azimuth. It is likely that more unmapped faults exist in the Western part of the Alaska peninsula between the Bruin Bay fault and the Lake Clark fault, but they remain unmapped because they are buried beneath the sedimentary cover and/or the waters of Bristol Bay. Aerial magnetic (aeromag) surveys were conducted to image buried subsurface structures and bedrock types in the Northern Alaska peninsula (Church et al, 1992). Glacial sedimentary deposits are not highly magnetic because they lack significant amounts of magnetite; therefore any magnetic “highs” should reflect underlying bedrock and/or structures in that bedrock. The aeromag maps delineate several NE-SW trending linear anomalies. These are interpreted by the Church et al ( ) to signal the presence of buried volcanic rocks, intrusions by highly magnetic plutons of intermediate composition, and/or sedimentary rocks with magnetic components such as greenstone. Intriguingly, the linear structures correlate with NE-SW trending “linears” found in remote sensing studies (Lappi, 2006). They also parallel the Bruin Bay fault, the elongation direction of Bristol Bay, the direction of the Kvichak river, the trend of subduction on a general scale, etc. Haeussler & Saltus (2004) interpret aeromagnetic “lows” to indicate subsurface faulting in the Lake Clark area. The Church et al study only reports anomalies, not highs or lows. Hence the “anomalies” in that study could represent subsurface faults, but there is no way to tell from the report. Nearby Wells The following table lists information from wells for which I was able to obtain logs. Temperatures are given as bottom hole temps (bht) or maximum temps (max). WELL NAME LAT LONG DEPTH (ft) TEMPERATURE DATE Iniskin Unit B1 9745 198 °F (bht) 10/1955 Iniskin Unit Z1 10920 200 °F (max) 12/1959 Bear Ck. Unit1 12063 227 °F (bht) 03/1955 Great Basins 2 8865 -Not listed- 11/1959 Ugashik 1 9476 198 °F (bht) 08/1966 Painter Ck 1 7912 150 °F (bht) 07/1967 Becharof 1 9023 210 °F (bht=max) 01/1985 I will attempt to obtain exact locations for the above wells. These data might be used in the future to generate a regional heat flow map. It cannot be done at the time of writing because heat flow is the product of the thermal gradient times the thermal conductivity of rocks – the latter of which is unknown at this time. Site Recommendations for Shallow Drilling Site C3 (1 mile south of Horseshoe Bend in the King Salmon River)  Intersects aerially-located NE-SW “linear”  Shows highest Hg and As values  Is relatively accessible for drilling  Intersects S edge of aeromag anomaly JT11 (interpreted by Church et al to signal intermediate-composition intrusions with a “lobate” shape) Site Z (Zimin allotment)  Intersects W edge of large aeromag anomaly V6 (interpreted by Church et al to represent Tertiary volcanic rocks (andesite or basalt))  Close to linear aeromag anomaly R1 (uninterpreted by Church et al)  Land accessible by winter trail; land status favorable for drilling References Church, S. E., Reihle, J. R., Magoon, L. B., and Campbell, D. L., 1992. Mineral and Energy Resource Assessment Maps of the Mount Katmai, Naknek, and Western Afognak Quadrangles, Alaska. 1:250000 map and pamphlet, USGS Miscellaneous Field Studies #MF-2021-F. Church, S. E., Detterman, R. L., and Wilson, F. H. 1989. Mineral and Energy Resource Assessment Maps of the Ugashik, Bristol Bay, and Western Karluk Quadrangles, Alaska. 1:250000 map, 2 sheets, USGS Miscellaneous Field Study #MF-1539-1. Detterman, R. L., Case, J. E., Wilson, F. H., and Yount, M. E., 1993. Geologic Map of the Ugashik, Bristol Bay, and Western Karluk Quadrangles, Alaska. 1:250000 map, 1 sheet, USGS Miscellaneous Investigation #I-1685. Haeussler, P. J., & Saltus, R. W., 2004. 26 km of Offset on the Lake Clark Fault Since Late Eocene Time. USGS Professional Paper 1709-A. Kolker, A. M., 2006. Preliminary Geothermal Resource Assessment: Northern Alaska Peninsula / Southern Cook Inlet Area. Unpublished report to Naknek Electric Association. Kolker, A. M., Naknek – King Salmon Area Soil Mercury (Hg) and Arsenic (As) – Phase 1 results. Unpublished report to Naknek Electric Association. Lappi, D. W., 2006. Remote Sensing report (title?) Paug-vik Development Corporation (PDC) / Oasis Environmental, 2000. Record of Decision for Final Remediation: North Bluff (LF005) and South Bluff (LF014) Groundwater Zone 3 (OT029). Report to US Air Force. Power, J., Moran, S., Haeussler, P. Seismic Studies in the Mount Peulik/Becharof Lake area, Alaska. Riehle, J. R., and Detterman, R. L., 1993. Quaternary Geologic Map of the Mount Katmai Quadrangle and Adjacent Parts of the Naknek and Afognak Quadrangles, Alaska. 1:250000 map, 1 sheet, USGS Miscellaneous Investigation #2032 Riehle, J. R., Detterman, R. L., Yount, M. E., and Miller, J. W., 1993. Geologic Map of the Mount Katmai Quadrangle and Adjacent Parts of the Naknek and Afognak Quadrangles, Alaska. 1:250000 map, 1 sheet, USGS Miscellaneous Investigation #I- 2204. Thomas, Steve, 2006. Johnson Drilling Company Well Log for Well #1, Nelbro Packing Co., King Salmon, AK, 4/98.