Open File Report 2009-5. Geologic map of the Lake...
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Loc no. Age estimate ( 14 C yr B.P.) 13 C/ 12 C (o/oo) Analytical method Material dated Geologic unit Lab no. Elev (ft) Reference Notes LW 527 >46,000 -28.5 14 C AMS wood Qpf Beta 254696 157 this report Sample collected from 2 to 3 ft thick exposure of unit Qpf adjacent to Stimson Creek; unit too small to be shown at map scale Qgt Qpu Qls Qpf Qpu Qpt Qpu Qgo, Qgos, Qgic, Qgoe Qa Qga Figure 1. Generalized schematic stratigraphy of geologic units in the Lake Wooten quadrangle, exclusive of beach, peat, and alluvial fan deposits. Qptu Qpu ? ? ? ? Qgos Qgt Qgt Qgt Qgt Qpt Qptu Qpt Qpt Qptu Qptu Qpu Qpu Qpu Qpu Qpu Qpu Qpu Qpu Qpu Qpu Qls Qa 1000 Elevation (feet) 800 600 400 200 0 1000 Elevation (feet) 800 600 400 200 0 WEST B B¢ -200 -400 -200 -400 WW198 WW44 WW43 WW178 WW183 WW176 WW181 WW177 WW184 Prickett Lake unnamed road unnamed road unnamed road stream stream Hood Canal EAST Qgt Qgt Qgt Qgt Qptu Qptu Qptu Qpu Qpu Qpu Qpu Qpu Qp Qp 1000 Elevation (feet) 800 600 400 200 0 1000 Elevation (feet) 800 600 400 200 0 A A¢ WW241 WW231 WW249 WW234 WW230 WW228 WW303 WW276 WW291 WW293 WW292 WW289 stream stream stream Haven Lake Christine Lake campground unnamed road unnamed road unnamed road unnamed road unnamed road unnamed road unnamed road EAST-NORTHEAST WEST-SOUTHWEST 527 WW289 WW292 WW293 WW291 WW276 WW303 WW228 WW230 WW234 WW249 WW231 WW241 WW198 WW44 WW43 WW178 WW184 WW177 WW181 WW176 WW183 Qpu Qls Qls Qls Qls Qls Qls Qls Qaf Qgt Qgo Qls Qb Qa Qls Qpu Qgt Qpu Qpt Qpt Qaf Qls Qls Qls Qaf Qb Qa Qgt Qpu Qls Qa Qb Qgt Qb Qa Qa Qgt Qgt Qls Qa Qls Qls Qls Qpt Qls Qaf Qls Qa Qls Qaf Qb Qgt Qgt Qpu Qpu Qgt Qgt Qgt Qgt Qpu Qpu Qls Qaf Qaf Qgo Qp Qgo Qaf Qgo Qa Qa Qgt Qgt Qgt Qls Qpu Qpu Qls Qgic Qaf Qgic Qpu Qls Qls Qgt Qgt Qgt Qgic Qls Qb Qaf Qb Qaf Qb Qa Qpu Qls Qa Qgt Qgic Qgo Qls Qa Qa Qgo Qgo Qgt Qgt Qgt Qgt Qp Qgo Qgo Qp Qgt Qp Qp Qp Qpu Qp Qgic Qgic Qa Qgo Qp Qp Qp Qa Qa Qgt Qgo Qgo Qgt Qgt Qgt Qgt Qgt Qgo Qgo Qga Qls Qgic Qgic Qaf Qa Qgic Qa Qaf Qgic Qls Qp Qp Qgo Qp Qa Qgic Qgo Qgt Qgic Qgic Qgic Qgic Qgo Qa Qgt Qgo Qp Qgic Qp Qgt Qgt Qgt Qgt Qgt Qgt Qgic Qgo Qa Qp Qgt Qgt Qgt Qgt Qp Qga Qgic Qaf Qa Qls Qga Qgt Qp Qp Qp Qp Qp Qp Qp Qp Qgt Qgt Qp Qgt Qp Qp Qp Qgo Qp Qp Qp Qpu Qpu Qp Qp Qp Qaf Qaf Qgt Qls Qp Qls Qp Qls Qp Qp Qp Qp Qls Qls Qls Qa Qpu Qpf Qa Qaf Qls Qa Qa Qaf Qaf Qaf Qgt Qaf Qls Qls Qb Qls Qls Qls Qls Qls Qls Qa Qls Qls Qls Qls Qls Qls Qa Qls Qls Qgoe Qls Qb Qb Qb Qls Qaf Qls Qls Qls Qa Qb Qls Qp Qgos Qls Qls Qls Qls Qls Qgo Qgo Qgt Qpt Qaf Qls Qa Qb Qls Qls Qa Qls Qpu Qpu Qpu Qpu Qpu Qpu Qpu Qpu Qpu Qpu Qgo Qgo Qp Qgo Qp Qa Qp Qls Qp Qgt Qp Qls Qp Qgt Qgic Qpu Qpu Qa Qa Qgo Qaf Qpu Qls Qgt Qgt Qgt Qpu Qls Qp Qls Qls Qls Qp Qpu Qp Qgo Qpu Qb Qls Qgo Qp Qp Qgoe Qgoe Qgoe Qgoe Qgoe Qgoe Qgoe Qgoe Qgoe Qgoe Qgoe Qgoe Qgt Qgt B A A¢ B¢ Catfish Lake scarp TACOMA FAULT R R 122°52¢30² 47°30¢00² 123°00¢00² 47°30¢00² 25¢00² 25¢00² 55¢00² 55¢00² 27¢30² 122°52¢30² 47°22¢30² 47°22¢30² 57¢30² 27¢30² 57¢30² R 3 W R 2 W T 23 N T 22 N T 23 N T 22 N 123°00¢00 ² 101 3 106 302 3 101 BELFAIR LILLIWAUP UNION SHELTON SQUAXIN ISLAND LONGBRANCH MCNEIL ISLAND VAUGHN BURLEY FOX ISLAND LAKE WOOTEN MASON LAKE Shelton Seattle fault zone Tacoma fault zone Tacoma fault zone 7000 FEET 1000 1000 0 2000 3000 4000 5000 6000 0.5 1 KILOMETER 1 0 0.5 1 0 1 MILE SCALE 1:24,000 © 2009 Washington Division of Geology and Earth Resources Lambert conformal conic projection North American Datum of 1927; to place on North American Datum of 1983, move the projection lines approximately 20 meters north and 95 meters east as shown by crosshair corner ticks Base map from scanned and rectified U.S. Geological Survey Lake Wooten 7.5-minute quadrangle, 1999 Shaded relief generated from a lidar bare-earth digital elevation model (available from Puget Sound Lidar Consortium, http://pugetsoundlidar.ess. washington.edu/); sun azimuth 290°; sun angle 60°; vertical exaggeration 2X Digital cartography and GIS by Elizabeth E. Thompson, Anne C. Heinitz, and J. Eric Schuster Editing by Jaretta M. Roloff, Jessica L. Czajkowski, and Karen D. Meyers Production by Jaretta M. Roloff This geologic map was funded in part by the U.S. Geological Survey National Cooperative Geologic Mapping Program. contour interval 20 feet APPROXIMATE MEAN DECLINATION, 2009 MAGNETIC NORTH TRUE NORT H 17° http://www.dnr.wa.gov/AboutDNR/Divisions/GER/ WASHINGTON DIVISION OF GEOLOGY AND EARTH RESOURCES OPEN FILE REPORT 2009-5 Lake Wooten 7.5-minute Quadrangle July 2009 Geologic Map of the Lake Wooten 7.5-minute Quadrangle, Mason County, Washington by Robert E. Derkey, Nicholas J. Hehemann, and Katelin Alldritt July 2009 Suggested citation: Derkey, R. E.; Hehemann, N. J.; Alldritt, Katelin, 2009, Geologic map of the Lake Wooten 7.5-minute quadrangle, Mason County, Washington: Washington Division of Geology and Earth Resources Open File Report 2009-5, 1 sheet, scale 1:24,000. [http://www.dnr.wa.gov/Publications/ger_ ofr2009-5_geol_map_lakewooten_24k.pdf] Disclaimer: This product is provided ‘as is’ without warranty of any kind, either expressed or implied, including, but not limited to, the implied warranties of merchantability and fitness for a particular use. The Washington Department of Natural Resources and the authors of this product will not be liable to the user of this product for any activity involving the product with respect to the following: (a) lost profits, lost savings, or any other consequential damages; (b) fitness of the product for a particular purpose; or (c) use of the product or results obtained from use of the product. This product is considered to be exempt from the Geologist Licensing Act [RCW 18.220.190 (4)] because it is geological research conducted by the State of Washington, Department of Natural Resources, Division of Geology and Earth Resources. Cross Sections. Cross sections were constructed based on sparse reliable water well data. Unit Qptu, depicted in the southeastern part of Cross Section A, does not appear in water will logs in the northeastern part of the section. Wells were used to establish the stratigraphy and do not depict a precise depth to unit contacts. The cross sections schematically represent stratigraphy and should not be used to determine depth to a particular stratigraphic unit at any point along their path. MAJOR FINDINGS • The Catfish Lake scarp of the Tacoma fault probably extends to the west into the Lake Wooten quadrangle at least as far as Hood Canal. • All glacial till in the quadrangle was initially thought to be only Vashon in age. An interbedded sediment sequence yielded an infinite radiocarbon date, meaning that the till beneath it is pre-Vashon in age. • Most landslides in the area are rooted in Vashon advance outwash and pre-Vashon fluvial or glaciofluvial deposits. • Detail was added to the local glacial stratigraphy (O’Neal, 2004). INTRODUCTION Most of the land surface of the Lake Wooten quadrangle, located near the center of the Puget Lowland, is covered by a thin veneer of glacial drift of the Vashon Stade of the Fraser Glaciation (Armstrong and others (1965) overlying a sequence of pre-Vashon glacial and nonglacial sediments. The southwest-trending elongate hills that characterize much of the terrain are drumlins sculpted by the Puget lobe of the Vashon continental glacier. Outcrops of pre-Vashon glacial and nonglacial deposits are rarely well exposed in the quadrangle, as they are less resistant to erosion and do not form prominent outcrops. Poorly consolidated pre-Vashon fluvial and glaciofluvial deposits are more permeable than Vashon deposits and have low cohesion. They are the source of numerous landslides in the quadrangle. The sediments brought by glaciers into the Puget Lowland may be from any of three different source regions. If the predominant rock fragments and grains are from granitic and metamorphic rocks, the probable source is the Coast Range of British Columbia (northern provenance); if the sediments contain andesitic volcanic rock fragments and glass in addition to granitic and metamorphic rock fragments, the probable source is the Cascade Range of Washington (Cascades provenance); and if the predominant rock fragments and grains are from basalt and mafic rocks, the probable source is the Olympic Mountains (Olympics provenance). Thin sections of glacial deposits from the Lake Wooten quadrangle consist of granitic and metamorphic rock fragments and lack andesitic rock fragments and glass, indicating that the deposits are of northern provenance. This differs from deposits in the eastern part of the Puget Lowland, which contain andesitic volcanic rock fragments and glass indicative of Cascades provenance (Walsh and others, 2003). GEOLOGIC HISTORY Bedrock does not crop out in the quadrangle; depth to bedrock is more than 500 ft in the eastern part of the quadrangle (Buchanan-Banks and Collins, 1994). Bedrock is believed to be basalt and related rocks of the Crescent Formation, exposed in the Olympic Mountains (Tabor and Cady, 1978) and on Green and Gold Mountains 5 mi north of the quadrangle (Haeussler and Clark, 2000). Our mapping dealt with only the uppermost 200 to 300 ft of the more than 500 ft of glacial and nonglacial deposits exposed or intercepted by water wells in the Lake Wooten quadrangle. This 200- to 300-ft-thick sequence is divided into Vashon and pre-Vashon deposits. Pre-Vashon Deposits Sediments deposited prior to the Vashon Stade of the Fraser Glaciation are subdivided into four units: pre-Vashon deposits, undifferentiated (unit Qpu); pre-Vashon deposits, fine grained (unit Qpf, stratigraphic position shown only on Fig. 1); pre-Vashon till (unit Qpt); and pre-Vashon till, undifferentiated (unit Qptu). Pre-Vashon till (unit Qpt) is difficult to distinguish from Vashon till (unit Qgt). The exposure confirmed as pre-Vashon till occurs north of Hood Canal on Stimson Creek (sec. 3, T22N R2W) directly beneath a clay bed from which a radiocarbon infinite date (sample 527) was obtained. Both the exposed clay bed and till bed on Stimson Creek are too small to be shown at map scale. Two larger exposures of pre-Vashon till (unit Qpt) are mapped south of Hood Canal. A second, presumably older, pre-Vashon till (unit Qptu) occurs in the subsurface near the southeast corner of the Lake Wooten quadrangle. Its existence is inferred based on water well logs—drillers often designate the compacted layers of till as ‘hardpan’. Unit Qptu is shown only in the cross sections and Figure 1. Whether this till is of northern or Olympics provenance is unknown. Till exposed immediately west of the Lake Wooten quadrangle on the north shore of Hood Canal is Olympics provenance (Robert Logan, Wash. Divn. of Geology and Earth Resources, oral commun., 2008). It projects beneath glacial and nonglacial deposits of the Lake Wooten quadrangle. We suggest that unit Qptu could be Olympics provenance. Both pre-Vashon tills are older than a radiocarbon infinite age from overlying units (Table 1; Logan and Walsh, 2007), but relative ages of the two older tills and correlation with any specific till unit of the Puget Lowland have not been established. Sediments underlying Vashon till (unit Qgt) in the Lake Wooten quadrangle consist of Vashon advance outwash (unit Qga) and a diverse sequence of glacial outwash and interglacial deposits. Vashon advance outwash is often difficult to distinguish from the non-till deposits older than Vashon till. The hillslopes overlooking both sides of Hood Canal consist of a thick sequence of pre-Vashon non-till deposits. Numerous landslides also obscure exposures in this sequence. In the Lake Wooten quadrangle, we map these deposits as pre-Vashon deposits, undifferentiated (unit Qpu). Cross Section B is a schematic representation of this sequence, based largely upon water well log data. Interglacial and nonglacial deposits intercepted in drilling water wells are usually logged as beds of gravel, sand, and clay. Inconsistencies between water well logs and rapid lateral facies changes preclude matching separated stratigraphic units on cross sections, with the exception of clay beds. Well log data is consistent enough to map a clay bed (unit Qpf) separate from pre-Vashon sediments, undifferentiated (unit Qpu) in the southern half of the Mason Lake quadrangle (Derkey and others, 2009). Although that clay bed (unit Qpf , approximate stratigraphic position illustrated in Fig. 1) is too thin to be shown at map scale in the Lake Wooten quadrangle, carbonaceous material from an exposure north of Hood Canal on Stimson Creek (sec. 3, T22N R2W) was found to be radiocarbon infinite (Table 1). Woody debris from pre-Vashon interglacial and nonglacial deposits on the east shore of Harstine Island in the Vaughn quadrangle also yielded a radiocarbon infinite age (Logan and Walsh, 2007). Therefore, the clay bed (unit Qpf in Fig. 1) confirms a pre-Vashon age for interglacial and nonglacial deposits (unit Qpu) in the south-adjacent Mason Lake quadrangle, where the only exposure of unit Qpf large enough to be shown at map scale is in Jarrell Cove State Park on Harstine Island (Derkey and others, 2009). Vashon Glacial Deposits Our mapping of the Lake Wooten quadrangle identified Vashon-age deposits consisting of till (unit Qgt) and outwash and ice contact deposits (units Qgo, Qgos, Qgic, and Qgoe ). Stratigraphic relationships are illustrated in Figure 1 and Cross Sections A and B. Vashon till (unit Qgt), which may be as much as 50 ft thick, is typically poorly sorted with angular sand-size grains. It was compacted by the weight of the overlying glacier and is resistant to erosion relative to the other Quaternary units—only a few streams have cut down through it. Tree roots rarely penetrate the till, and water does not easily move downward through it, resulting in overland flow during periods of high precipitation. Numerous sloughs and ponds have formed in depressions on the till surface. Vegetation flourishes in these depressions, with accompanying accumulation of peat (unit Qp ). LANDSLIDES Numerous landslides have been identified in the Lake Wooten quadrangle. Landslide polygons (Isabelle Sarikhan, Wash. Divn. of Geology and Earth Resources, unpub. data, 2009) were modified using lidar to establish approximate boundaries. Virtually all landslides that have been identified are associated with pre-Vashon deposits, undifferentiated (unit Qpu ). The larger landslide scarps encroach upward into overlying Vashon till (unit Qgt). We suggest that the more permeable outwash and nonglacial deposits in the Lake Wooten quadrangle, when combined with steep slopes, are subject to development of landslides. STRUCTURE The lidar-identified trace of the Catfish Lake scarp of the Tacoma fault (Sherrod and others, 2003, 2004; Nelson and others, 2009) is in the southeast corner of the quadrangle. The fault is a high-angle reverse fault that dips northward at 55 to 60 degrees with ‘up’ on the north side of the fault (Logan and Walsh, 2007). We have extended the trace of the fault westward to Hood Canal, based on exposures in a borrow pit in sec. 22, T22N R2W. We have also noted that lidar imagery shows that the wave-cut beach zone is wider east and north of where our extension of the fault intersects the Hood Canal shoreline. We believe this may be due to relative uplift to the north on the upthrown side of the fault. Although the lidar-identified trace of the fault is not as prominent as in the Mason Lake quadrangle, we suggest that it should be extended to Hood Canal. DESCRIPTION OF MAP UNITS Holocene and Pleistocene Nonglacial Deposits Qa Alluvium (Holocene)—Silt, sand, and gravel deposited by streams; may include some lacustrine deposits and organic materials, such as peat. Qb Beach deposits (Holocene)—Mud, sand, and gravel deposited in the intertidal zone, or residual pebble-cobble gravel and isolated boulders on a wave-cut platform. Qp Peat (Holocene)—Organic-matter-rich sediments deposited in closed depressions; in addition to peat, may contain silt and clay; commonly clogged with aquatic plants, abundant tree snags, stumps, and other woody debris in and adjacent to shallow or seasonal sloughs and ponds. Qaf Alluvial fan (Holocene)—Silt, sand, and gravel deposited where upland streams meet valley floors; generally overlies till (unit Qgt), recessional outwash (unit Qgo ), and alluvium (unit Qa ). Qls Landslide deposits (Holocene and Pleistocene)—Generally loose, jumbled, tan to gray, silty sandy gravel with few to no discernible sedimentary structures; surfaces of landslides are generally undulatory; some occur as large deep-seated slides and others as shallow surface failures or block falls. Almost all occur in Vashon advance outwash (unit Qga ) and pre-Vashon sediments, undifferentiated (unit Qpu ). Deposits of the Vashon Stade of the Fraser Glaciation Qgo Vashon recessional outwash (Pleistocene)—Recessional and proglacial sand and gravel of northern provenance, locally containing silt and clay; stratified; gray, tan, or brown; moderately to well rounded; poorly to moderately sorted; may include ice-contact, stratified drift, and lacustrine deposits. Divided into: Vashon recessional outwash sand and silt (Pleistocene)—Loose sand, silt, and gravel; gray, tan, or brown; clasts moderately to well rounded; generally well sorted; clasts and grains consist of northern-provenance granitic and metamorphic rocks and rock fragments and polycrystalline quartz carried by Vashon meltwater; drains well due to high porosity and permeability; commonly forms thin to thick (25 ft or more) beds deposited in poorly defined ice-contact channels; stratigraphically overlies Vashon till. Qgic Ice-contact deposits (Pleistocene)—Undifferentiated mixture of stagnant ice and dynamic ice deposits; dynamic ice deposits include lodgment till, drumlins, and advance outwash; stagnant ice deposits include ablation till, subglacial water flow deposits (such as eskers), and recessional outwash; also includes irregular blocks of lodgment till and detrital till fragments; till occurrences lack continuity at the ground surface; topography formed by a mix of subglacial, ice-marginal, and recessional processes. Qgoe Vashon recessional outwash, ice-contact deposits (eskers)(Pleistocene)—Sand and gravel; gray, tan, or brown; moderately to well sorted and rounded; stratified; consists of sediment rich in northern-provenance granitic and metamorphic clasts and polycrystalline quartz; high porosity and permeability; deposited by Vashon meltwater in areas occupied by stagnant ice; forms low, elongate sinuous hills in recessional outwash channels; commonly deposited in ravines adjacent to drumlins in Vashon till (unit Qgt). Qgt Vashon till (Pleistocene)—Unstratified to moderately stratified, compact, unsorted mixture of clay, silt, sand, and gravel deposited directly by glacial ice; consists of sediment rich in northern-provenance clasts; gray, tan, or brown; nearly everywhere in sharp contact with underlying units; does not drain well, as permeability and porosity are low; sand and finer grains in matrix are very angular; pebble- to boulder-size clasts are commonly striated and faceted, having angular and (or) rounded edges; boulders are generally disseminated and relatively rare; may contain interbeds of sand and gravel; ground surface for this unit characterized by streamlined drumlins, striations, and flutes that are generally hundreds to thousands of feet long; angular to subrounded glacial erratic boulders consist mostly of plutonic or metamorphic rock; unit may be capped by a few feet of unsorted and stained ablation sand and gravel; locally crosscuts older sediments, forming angular unconformities; drag folding and horizontal shearing may occur at the base of the till or internally between layers of till, especially in thick deposits; unit ranges in thickness from 0 to more than 50 ft. Qga Vashon advance outwash (Pleistocene)—Sand and gravel with lacustrine clay, silt, and sand; gray to light brown; compact; consists of sediment rich in northern-provenance clasts; well rounded and most commonly well sorted; mostly polycrystalline quartz, plutonic, volcanic, and minor metamorphic grains; deposited during Vashon glacial advance; generally more compact than recessional outwash; most easily distinguished from recessional outwash if covered directly by Vashon till; may also contain pre-Vashon sediment at its base. Pre-Vashon Deposits Qpu Pre-Vashon sediments, undifferentiated (Pleistocene)—Composite unit of glacial and nonglacial gravel, sand, silt, and clay beneath Vashon till; consists of sediment rich in northern-provenance clasts; gray to tan; often iron-oxide stained; moderately to well rounded; poorly to moderately well bedded; consists of units not separable at map scale due to poor exposure; may include some Vashon advance outwash; most commonly recognized in water wells in the quadrangle and depicted in cross sections; water well logs, which were used for the cross sections, often distinguish these beds as clay, sand, and gravel. Qpf Pre-Vashon deposits, fine grained (Fig. 1 only)(Pleistocene)—Silty sand and sandy silt with minor clay and some gravel interbeds; gravel clasts are northern-provenance; moderately rounded; laminated to poorly bedded; generally compact, but may be loose; locally to completely iron-oxide stained, with iron-oxide-cemented layers. Qpt Pre-Vashon till (Pleistocene)—Unstratified, compact, unsorted mixture of clay, silt, sand, and gravel deposited directly by glacial ice; gray, tan, or brown; consists of sediment rich in northern-provenance granitic and metamorphic clasts; contact with underlying unit not exposed; contains granitic, volcanic, and metamorphic grains with abundant polycrystalline quartz; petrographically indistinguishable from unit Qgt; permeability and porosity are low. Qptu Pre-Vashon till, undifferentiated (cross sections and Fig. 1 only)(Pleistocene)—Compact, unsorted mixture of clay, silt, sand, and gravel; existence determined from water well logs; provenance unknown. GEOLOGIC SYMBOLS Contact—long dashed where approximately located; short dashed where inferred or indefinite Reverse fault, R on upthrown side—long dashed where approximately located Water well—numbers correspond to well numbers on cross sections Age date sample site, radiocarbon (Table 1) ACKNOWLEDGMENTS This project was made possible by the U.S. Geological Survey National Geologic Mapping Program under Cooperative Agreement no. 08HQAG0104 of the STATEMAP program and by the Washington Division of Geology and Earth Resources geologic mapping program. Colleague Michael Polenz was most helpful in answering many questions and making comparisons during his concurrent mapping of adjacent quadrangles. Josh Logan, Heather Littke, and Tim Walsh provided geological insight and assistance during the project. Special thanks to Isabelle Sarikhan for providing the landslide data. REFERENCES Armstrong, J. E.; Crandell, D. R.; Easterbrook, D. J.; Noble, J. B., 1965, Late Pleistocene stratigraphy and chronology in southwestern British Columbia and northwestern Washington: Geological Society of America Bulletin, v. 76, no. 3, p. 321-330. Buchanan-Banks, J. M.; Collins, D. S., 1994, Map showing depth to bedrock of the Tacoma and part of the Centralia 30′ x 60′ quadrangles, Washington: U.S. Geological Survey Miscellaneous Field Studies Map MF-2265, 2 sheets, scale 1:100, 000. Derkey, R. E.; Hehemann, N. J.; Aldritt, Kaitlin, 2009, Geologic map of the Mason Lake 7.5-minute quadrangle, Mason County, Washington: Washington Division of Geology and Earth Resources Open File Report 2009-6, 1 sheet, scale 1:24,000. [http://www.dnr.wa.gov/Publications/ger_ofr2009-6_geol_map_masonlake_24k.pdf] Haeussler, P. J.; Clark, K. P., 2000, Preliminary geologic map of the Wildcat Lake 7.5 quadrangle, Kitsap and Mason Counties, Washington: U.S. Geological Survey Open-File Report 00-356, 1 sheet, scale 1:24,000. [http://pubs.er.usgs.gov/usgspubs/ofr/ofr00356] Logan, R. L.; Walsh, T. J., 2007, Geologic map of the Vaughn 7.5-minute quadrangle, Pierce and Mason Counties, Washington: Washington Division of Geology and Earth Resources Geologic Map GM-65, 1 sheet, scale 1:24,000. [http://www.dnr.wa.gov/Publications/ger_gm65_geol_map_vaughn_24k.pdf] Nelson, A. R.; Personius, S. F.; Sherrod, B. L.; Buck, Jason; Bradley, Lee-Ann; Henley, Gary, II; Liberty, L. M.; Kelsey, H. M.; Witter, R. C.; Koehler, R. D.; Schermer, E. R.; Nemser, E. S.; Cladouhos, T. T., 2009, Field and laboratory data from an earthquake history study of scarps in the hanging wall of the Tacoma fault, Mason and Pierce Counties, Washington: U.S. Geological Survey Scientific Investigations Map SIM-3060, 3 sheets, scale 1:30,000. [http://pubs.usgs.gov/sim/3060/] O’Neal, M. A., 2004, Geologic map of the Lilliwaup and Lake Wooten 7.5-minute quadrangles, Kitsap and Mason Counties, Washington: University of Washington?, 1 sheet, scale 1:24,000. [http://www.hoodcanal.washington.edu/ documents/document.jsp?id=1523] Sherrod, B. L.; Brocher, T. M.; Weaver, C. S.; Bucknam, R. C.; Blakely, R. J.; Kelsey, H. M.; Nelson, A. R.; Haugerud, Ralph, 2004, Holocene fault scarps near Tacoma, Washington, USA: Geology, v. 32, no. 1, p. 9-12. [http://geology. geoscienceworld.org/cgi/content/abstract/32/1/9] Sherrod, B. L.; Nelson, A. R.; Kelsey, H. M.; Brocher, T. M.; Blakely, R. J.; Weaver, C. S.; Rountree, N. K.; Rhea, B. S.; Jackson, B. S., 2003, The Catfish Lake scarp, Allyn, Washington—Preliminary field data and implications for earthquake hazards posed by the Tacoma fault: U.S. Geological Survey Open-File Report 03-0455, 1 sheet, with 12 p. text. [http://pubs.usgs.gov/of/2003/of03-455/] Tabor, R. W.; Cady, W. M., 1978, Geologic map of the Olympic Peninsula, Washington: U.S. Geological Survey Miscellaneous Investigations Series Map I-994, 2 sheets, scale 1:125,000. Walsh, T. J.; Logan, R. L.; Polenz, Michael, 2003, Geologic map of the McNeil Island 7.5-minute quadrangle, Pierce and Thurston Counties, Washington: Washington Division of Geology and Earth Resources Open File Report 2003-22, 1 sheet, scale 1:24,000. [http://www.dnr.wa.gov/Publications/ger_ofr2003-22_geol_map_mcneilisland_ 24k.pdf] Table 1. Radiocarbon date, age control data information, Sample LW 527. Lab uncertainty values are one standard deviation (68% confidence interval) and include random errors that can be estimated by the lab but exclude uncertainties that cannot be detected by the laboratory’s analytical procedures. Analyses were performed by Beta Analytic, Inc. (Miami, Florida). Radiocarbon ages are ‘conventional’, that is, adjusted for measured 13 C/ 12 C ratio. The geologic unit shown in this table is the unit from which the sample was extracted. The sample was collected from an exposure too small to be shown as a polygon at map scale. Elevations are in feet above mean sea level using lidar data. AMS, radiocarbon analysis by atomic mass spectrometry. 527 R R W277 i Qpt Qptu Qa Qb Qaf Qgt Qgo Qga Qp Qpf Qpu Qgos Qls Qgic
Transcript of Open File Report 2009-5. Geologic map of the Lake...
Loc no. Age estimate (14C yr B.P.)
13C/12C (o/oo)
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Material dated
Geologic unit Lab no. Elev (ft) Reference Notes
LW 527 >46,000 -28.5 14C AMS wood Qpf Beta 254696 157 this report
Sample collected from 2 to 3 ft thick exposure of unit Qpf adjacent to Stimson Creek; unit too small to be shown at map scale
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Figure 1. Generalized schematic stratigraphy of geologic units in the Lake Wooten quadrangle, exclusive of beach, peat, and alluvial fan deposits.
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© 2009 Washington Division of Geology and Earth Resources
Lambert conformal conic projectionNorth American Datum of 1927; to place on North American Datum of 1983,
move the projection lines approximately 20 meters north and 95 meters east as shown by crosshair corner ticks
Base map from scanned and rectified U.S. Geological Survey Lake Wooten 7.5-minute quadrangle, 1999
Shaded relief generated from a lidar bare-earth digital elevation model (available from Puget Sound Lidar Consortium, http://pugetsoundlidar.ess. washington.edu/); sun azimuth 290°; sun angle 60°; vertical exaggeration 2X
Digital cartography and GIS by Elizabeth E. Thompson, Anne C. Heinitz, and J. Eric Schuster
Editing by Jaretta M. Roloff, Jessica L. Czajkowski, and Karen D. MeyersProduction by Jaretta M. Roloff
This geologic map was funded in part by the U.S. Geological Survey National Cooperative Geologic Mapping Program.
contour interval 20 feet
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http://www.dnr.wa.gov/AboutDNR/Divisions/GER/
WASHINGTON DIVISION OF GEOLOGY AND EARTH RESOURCESOPEN FILE REPORT 2009-5
Lake Wooten 7.5-minute QuadrangleJuly 2009
Geologic Map of the Lake Wooten 7.5-minute Quadrangle,Mason County, Washington
by Robert E. Derkey, Nicholas J. Hehemann, and Katelin Alldritt
July 2009
Suggested citation: Derkey, R. E.; Hehemann, N. J.; Alldritt, Katelin, 2009, Geologic map of the Lake Wooten 7.5-minute quadrangle, Mason County, Washington: Washington Division of Geology and Earth Resources Open File Report 2009-5, 1 sheet, scale 1:24,000. [http://www.dnr.wa.gov/Publications/ger_ ofr2009-5_geol_map_lakewooten_24k.pdf]
Disclaimer: This product is provided ‘as is’ without warranty of any kind, either expressed or implied, including, but not limited to, the implied warranties of merchantability and fitness for a particular use. The Washington Department of Natural Resources and the authors of this product will not be liable to the user of this product for any activity involving the product with respect to the following: (a) lost profits, lost savings, or any other consequential damages; (b) fitness of the product for a particular purpose; or (c) use of the product or results obtained from use of the product. This product is considered to be exempt from the Geologist Licensing Act [RCW 18.220.190 (4)] because it is geological research conducted by the State of Washington, Department of Natural Resources, Division of Geology and Earth Resources.
Cross Sections. Cross sections were constructed based on sparse reliable water well data. Unit Qptu, depicted in the southeastern part of Cross Section A, does not appear in water will logs in the northeastern part of the section. Wells were used to establish the stratigraphy and do not depict a precise depth to unit contacts. The cross sections schematically represent stratigraphy and should not be used to determine depth to a particular stratigraphic unit at any point along their path.
MAJOR FINDINGS
• The Catfish Lake scarp of the Tacoma fault probably extends to the west into the Lake Wooten quadrangle at least as far as Hood Canal.
• All glacial till in the quadrangle was initially thought to be only Vashon in age. An interbedded sediment sequence yielded an infinite radiocarbon date, meaning that the till beneath it is pre-Vashon in age.
• Most landslides in the area are rooted in Vashon advance outwash and pre-Vashon fluvial or glaciofluvial deposits.
• Detail was added to the local glacial stratigraphy (O’Neal, 2004).
INTRODUCTION
Most of the land surface of the Lake Wooten quadrangle, located near the center of the Puget Lowland, is covered by a thin veneer of glacial drift of the Vashon Stade of the Fraser Glaciation (Armstrong and others (1965) overlying a sequence of pre-Vashon glacial and nonglacial sediments. The southwest-trending elongate hills that characterize much of the terrain are drumlins sculpted by the Puget lobe of the Vashon continental glacier. Outcrops of pre-Vashon glacial and nonglacial deposits are rarely well exposed in the quadrangle, as they are less resistant to erosion and do not form prominent outcrops. Poorly consolidated pre-Vashon fluvial and glaciofluvial deposits are more permeable than Vashon deposits and have low cohesion. They are the source of numerous landslides in the quadrangle.
The sediments brought by glaciers into the Puget Lowland may be from any of three different source regions. If the predominant rock fragments and grains are from granitic and metamorphic rocks, the probable source is the Coast Range of British Columbia (northern provenance); if the sediments contain andesitic volcanic rock fragments and glass in addition to granitic and metamorphic rock fragments, the probable source is the Cascade Range of Washington (Cascades provenance); and if the predominant rock fragments and grains are from basalt and mafic rocks, the probable source is the Olympic Mountains (Olympics provenance). Thin sections of glacial deposits from the Lake Wooten quadrangle consist of granitic and metamorphic rock fragments and lack andesitic rock fragments and glass, indicating that the deposits are of northern provenance. This differs from deposits in the eastern part of the Puget Lowland, which contain andesitic volcanic rock fragments and glass indicative of Cascades provenance (Walsh and others, 2003).
GEOLOGIC HISTORY
Bedrock does not crop out in the quadrangle; depth to bedrock is more than 500 ft in the eastern part of the quadrangle (Buchanan-Banks and Collins, 1994). Bedrock is believed to be basalt and related rocks of the Crescent Formation, exposed in the Olympic Mountains (Tabor and Cady, 1978) and on Green and Gold Mountains 5 mi north of the quadrangle (Haeussler and Clark, 2000). Our mapping dealt with only the uppermost 200 to 300 ft of the more than 500 ft of glacial and nonglacial deposits exposed or intercepted by water wells in the Lake Wooten quadrangle. This 200- to 300-ft-thick sequence is divided into Vashon and pre-Vashon deposits.
Pre-Vashon Deposits
Sediments deposited prior to the Vashon Stade of the Fraser Glaciation are subdivided into four units: pre-Vashon deposits, undifferentiated (unit Qpu); pre-Vashon deposits, fine grained (unit Qpf, stratigraphic position shown only on Fig. 1); pre-Vashon till (unit Qpt); and pre-Vashon till, undifferentiated (unit Qptu). Pre-Vashon till (unit Qpt) is difficult to distinguish from Vashon till (unit Qgt). The exposure confirmed as pre-Vashon till occurs north of Hood Canal on Stimson Creek (sec. 3, T22N R2W) directly beneath a clay bed from which a radiocarbon infinite date (sample 527) was obtained. Both the exposed clay bed and till bed on Stimson Creek are too small to be shown at map scale. Two larger exposures of pre-Vashon till (unit Qpt) are mapped south of Hood Canal.
A second, presumably older, pre-Vashon till (unit Qptu) occurs in the subsurface near the southeast corner of the Lake Wooten quadrangle. Its existence is inferred based on water well logs—drillers often designate the compacted layers of till as ‘hardpan’. Unit Qptu is shown only in the cross sections and Figure 1. Whether this till is of northern or Olympics provenance is unknown. Till exposed immediately west of the Lake Wooten quadrangle on the north shore of Hood Canal is Olympics provenance (Robert Logan, Wash. Divn. of Geology and Earth Resources, oral commun., 2008). It projects beneath glacial and nonglacial deposits of the Lake Wooten quadrangle. We suggest that unit Qptu could be Olympics provenance. Both pre-Vashon tills are older than a radiocarbon infinite age from overlying units (Table 1; Logan and Walsh, 2007), but relative ages of the two older tills and correlation with any specific till unit of the Puget Lowland have not been established.
Sediments underlying Vashon till (unit Qgt) in the Lake Wooten quadrangle consist of Vashon advance outwash (unit Qga) and a diverse sequence of glacial outwash and interglacial deposits. Vashon advance outwash is often difficult to distinguish from the non-till deposits older than Vashon till. The hillslopes overlooking both sides of Hood Canal consist of a thick sequence of pre-Vashon non-till deposits. Numerous landslides also obscure exposures in this sequence. In the Lake Wooten quadrangle, we map these deposits as pre-Vashon deposits, undifferentiated (unit Qpu). Cross Section B is a schematic representation of this sequence, based largely upon water well log data.
Interglacial and nonglacial deposits intercepted in drilling water wells are usually logged as beds of gravel, sand, and clay. Inconsistencies between water well logs and rapid lateral facies changes preclude matching separated stratigraphic units on cross sections, with the exception of clay beds. Well log data is consistent enough to map a clay bed (unit Qpf) separate from pre-Vashon sediments, undifferentiated (unit Qpu) in the southern half of the Mason Lake quadrangle (Derkey and others, 2009). Although that clay bed (unit Qpf, approximate stratigraphic position illustrated in Fig. 1) is too thin to be shown at map scale in the Lake Wooten quadrangle, carbonaceous material from an exposure north of Hood Canal on Stimson Creek (sec. 3, T22N R2W) was found to be radiocarbon infinite (Table 1). Woody debris from pre-Vashon interglacial and nonglacial deposits on the east shore of Harstine Island in the Vaughn quadrangle also yielded a radiocarbon infinite age (Logan and Walsh, 2007). Therefore, the clay bed (unit Qpf in Fig. 1) confirms a pre-Vashon age for interglacial and nonglacial deposits (unit Qpu) in the south-adjacent Mason Lake quadrangle, where the only exposure of unit Qpf large enough to be shown at map scale is in Jarrell Cove State Park on Harstine Island (Derkey and others, 2009).
Vashon Glacial Deposits
Our mapping of the Lake Wooten quadrangle identified Vashon-age deposits consisting of till (unit Qgt) and outwash and ice contact deposits (units Qgo, Qgos, Qgic, and Qgoe). Stratigraphic relationships are illustrated in Figure 1 and Cross Sections A and B. Vashon till (unit Qgt), which may be as much as 50 ft thick, is typically poorly sorted with angular sand-size grains. It was compacted by the weight of the overlying glacier and is resistant to erosion relative to the other Quaternary units—only a few streams have cut down through it. Tree roots rarely penetrate the till, and water does not easily move downward through it, resulting in overland flow during periods of high precipitation. Numerous sloughs and ponds have formed in depressions on the till surface. Vegetation flourishes in these depressions, with accompanying accumulation of peat (unit Qp).
LANDSLIDES
Numerous landslides have been identified in the Lake Wooten quadrangle. Landslide polygons (Isabelle Sarikhan, Wash. Divn. of Geology and Earth Resources, unpub. data, 2009) were modified using lidar to establish approximate boundaries. Virtually all landslides that have been identified are associated with pre-Vashon deposits, undifferentiated (unit Qpu). The larger landslide scarps encroach upward into overlying Vashon till (unit Qgt). We suggest that the more permeable outwash and nonglacial deposits in the Lake Wooten quadrangle, when combined with steep slopes, are subject to development of landslides.
STRUCTURE
The lidar-identified trace of the Catfish Lake scarp of the Tacoma fault (Sherrod and others, 2003, 2004; Nelson and others, 2009) is in the southeast corner of the quadrangle. The fault is a high-angle reverse fault that dips northward at 55 to 60 degrees with ‘up’ on the north side of the fault (Logan and Walsh, 2007). We have extended the trace of the fault westward to Hood Canal, based on exposures in a borrow pit in sec. 22, T22N R2W. We have also noted that lidar imagery shows that the wave-cut beach zone is wider east and north of where our extension of the fault intersects the Hood Canal shoreline. We believe this may be due to relative uplift to the north on the upthrown side of the fault. Although the lidar-identified trace of the fault is not as prominent as in the Mason Lake quadrangle, we suggest that it should be extended to Hood Canal.
DESCRIPTION OF MAP UNITS
Holocene and Pleistocene Nonglacial Deposits
Qa Alluvium (Holocene)—Silt, sand, and gravel deposited by streams; may include some lacustrine deposits and organic materials, such as peat.
Qb Beach deposits (Holocene)—Mud, sand, and gravel deposited in the intertidal zone, or residual pebble-cobble gravel and isolated boulders on a wave-cut platform.
Qp Peat (Holocene)—Organic-matter-rich sediments deposited in closed depressions; in addition to peat, may contain silt and clay; commonly clogged with aquatic plants, abundant tree snags, stumps, and other woody debris in and adjacent to shallow or seasonal sloughs and ponds.
Qaf Alluvial fan (Holocene)—Silt, sand, and gravel deposited where upland streams meet valley floors; generally overlies till (unit Qgt), recessional outwash (unit Qgo), and alluvium (unit Qa).
Qls Landslide deposits (Holocene and Pleistocene)—Generally loose, jumbled, tan to gray, silty sandy gravel with few to no discernible sedimentary structures; surfaces of landslides are generally undulatory; some occur as large deep-seated slides and others as shallow surface failures or block falls. Almost all occur in Vashon advance outwash (unit Qga) and pre-Vashon sediments, undifferentiated (unit Qpu).
Deposits of the Vashon Stade of the Fraser Glaciation
Qgo Vashon recessional outwash (Pleistocene)—Recessional and proglacial sand and gravel of northern provenance, locally containing silt and clay; stratified; gray, tan, or brown; moderately to well rounded; poorly to moderately sorted; may include ice-contact, stratified drift, and lacustrine deposits. Divided into:
Qgos Vashon recessional outwash sand and silt (Pleistocene)—Loose sand, silt, and gravel; gray, tan, or brown; clasts moderately to well rounded; generally well sorted; clasts and grains consist of northern-provenance granitic and metamorphic rocks and rock fragments and polycrystalline quartz carried by Vashon meltwater; drains well due to high porosity and permeability; commonly forms thin to thick (25 ft or more) beds deposited in poorly defined ice-contact channels; stratigraphically overlies Vashon till.
Qgic Ice-contact deposits (Pleistocene)—Undifferentiated mixture of stagnant ice and dynamic ice deposits; dynamic ice deposits include lodgment till, drumlins, and advance outwash; stagnant ice deposits include ablation till, subglacial water flow deposits (such as eskers), and recessional outwash; also includes irregular blocks of lodgment till and detrital till fragments; till occurrences lack continuity at the ground surface; topography formed by a mix of subglacial, ice-marginal, and recessional processes.
Qgoe Vashon recessional outwash, ice-contact deposits (eskers)(Pleistocene)—Sand and gravel; gray, tan, or brown; moderately to well sorted and rounded; stratified; consists of sediment rich in northern-provenance granitic and metamorphic clasts and polycrystalline quartz; high porosity and permeability; deposited by Vashon meltwater in areas occupied by stagnant ice; forms low, elongate sinuous hills in recessional outwash channels; commonly deposited in ravines adjacent to drumlins in Vashon till (unit Qgt).
Qgt Vashon till (Pleistocene)—Unstratified to moderately stratified, compact, unsorted mixture of clay, silt, sand, and gravel deposited directly by glacial ice; consists of sediment rich in northern-provenance clasts; gray, tan, or brown; nearly everywhere in sharp contact with underlying units; does not drain well, as permeability and porosity are low; sand and finer grains in matrix are very angular; pebble- to boulder-size clasts are commonly striated and faceted, having angular and (or) rounded edges; boulders are generally disseminated and relatively rare; may contain interbeds of sand and gravel; ground surface for this unit characterized by streamlined drumlins, striations, and flutes that are generally hundreds to thousands of feet long; angular to subrounded glacial erratic boulders consist mostly of plutonic or metamorphic rock; unit may be capped by a few feet of unsorted and stained ablation sand and gravel; locally crosscuts older sediments, forming angular unconformities; drag folding and horizontal shearing may occur at the base of the till or internally between layers of till, especially in thick deposits; unit ranges in thickness from 0 to more than 50 ft.
Qga Vashon advance outwash (Pleistocene)—Sand and gravel with lacustrine clay, silt, and sand; gray to light brown; compact; consists of sediment rich in northern-provenance clasts; well rounded and most commonly well sorted; mostly polycrystalline quartz, plutonic, volcanic, and minor metamorphic grains; deposited during Vashon glacial advance; generally more compact than recessional outwash; most easily distinguished from recessional outwash if covered directly by Vashon till; may also contain pre-Vashon sediment at its base.
Pre-Vashon Deposits
Qpu Pre-Vashon sediments, undifferentiated (Pleistocene)—Composite unit of glacial and nonglacial gravel, sand, silt, and clay beneath Vashon till; consists of sediment rich in northern-provenance clasts; gray to tan; often iron-oxide stained; moderately to well rounded; poorly to moderately well bedded; consists of units not separable at map scale due to poor exposure; may include some Vashon advance outwash; most commonly recognized in water wells in the quadrangle and depicted in cross sections; water well logs, which were used for the cross sections, often distinguish these beds as clay, sand, and gravel.
Qpf Pre-Vashon deposits, fine grained (Fig. 1 only)(Pleistocene)—Silty sand and sandy silt with minor clay and some gravel interbeds; gravel clasts are northern-provenance; moderately rounded; laminated to poorly bedded; generally compact, but may be loose; locally to completely iron-oxide stained, with iron-oxide-cemented layers.
Qpt Pre-Vashon till (Pleistocene)—Unstratified, compact, unsorted mixture of clay, silt, sand, and gravel deposited directly by glacial ice; gray, tan, or brown; consists of sediment rich in northern-provenance granitic and metamorphic clasts; contact with underlying unit not exposed; contains granitic, volcanic, and metamorphic grains with abundant polycrystalline quartz; petrographically indistinguishable from unit Qgt; permeability and porosity are low.
Qptu Pre-Vashon till, undifferentiated (cross sections and Fig. 1 only)(Pleistocene)—Compact, unsorted mixture of clay, silt, sand, and gravel; existence determined from water well logs; provenance unknown.
GEOLOGIC SYMBOLS
Contact—long dashed where approximately located; short dashed where inferred or indefinite
Reverse fault, R on upthrown side—long dashed where approximately located
Water well—numbers correspond to well numbers on cross sections
Age date sample site, radiocarbon (Table 1)
ACKNOWLEDGMENTS
This project was made possible by the U.S. Geological Survey National Geologic Mapping Program under Cooperative Agreement no. 08HQAG0104 of the STATEMAP program and by the Washington Division of Geology and Earth Resources geologic mapping program. Colleague Michael Polenz was most helpful in answering many questions and making comparisons during his concurrent mapping of adjacent quadrangles. Josh Logan, Heather Littke, and Tim Walsh provided geological insight and assistance during the project. Special thanks to Isabelle Sarikhan for providing the landslide data.
REFERENCES
Armstrong, J. E.; Crandell, D. R.; Easterbrook, D. J.; Noble, J. B., 1965, Late Pleistocene stratigraphy and chronology in southwestern British Columbia and northwestern Washington: Geological Society of America Bulletin, v. 76, no. 3, p. 321-330.
Buchanan-Banks, J. M.; Collins, D. S., 1994, Map showing depth to bedrock of the Tacoma and part of the Centralia 30′ x 60′ quadrangles, Washington: U.S. Geological Survey Miscellaneous Field Studies Map MF-2265, 2 sheets, scale 1:100, 000.
Derkey, R. E.; Hehemann, N. J.; Aldritt, Kaitlin, 2009, Geologic map of the Mason Lake 7.5-minute quadrangle, Mason County, Washington: Washington Division of Geology and Earth Resources Open File Report 2009-6, 1 sheet, scale 1:24,000. [http://www.dnr.wa.gov/Publications/ger_ofr2009-6_geol_map_masonlake_24k.pdf]
Haeussler, P. J.; Clark, K. P., 2000, Preliminary geologic map of the Wildcat Lake 7.5 quadrangle, Kitsap and Mason Counties, Washington: U.S. Geological Survey Open-File Report 00-356, 1 sheet, scale 1:24,000. [http://pubs.er.usgs.gov/usgspubs/ofr/ofr00356]
Logan, R. L.; Walsh, T. J., 2007, Geologic map of the Vaughn 7.5-minute quadrangle, Pierce and Mason Counties, Washington: Washington Division of Geology and Earth Resources Geologic Map GM-65, 1 sheet, scale 1:24,000. [http://www.dnr.wa.gov/Publications/ger_gm65_geol_map_vaughn_24k.pdf]
Nelson, A. R.; Personius, S. F.; Sherrod, B. L.; Buck, Jason; Bradley, Lee-Ann; Henley, Gary, II; Liberty, L. M.; Kelsey, H. M.; Witter, R. C.; Koehler, R. D.; Schermer, E. R.; Nemser, E. S.; Cladouhos, T. T., 2009, Field and laboratory data from an earthquake history study of scarps in the hanging wall of the Tacoma fault, Mason and Pierce Counties, Washington: U.S. Geological Survey Scientific Investigations Map SIM-3060, 3 sheets, scale 1:30,000. [http://pubs.usgs.gov/sim/3060/]
O’Neal, M. A., 2004, Geologic map of the Lilliwaup and Lake Wooten 7.5-minute quadrangles, Kitsap and Mason Counties, Washington: University of Washington?, 1 sheet, scale 1:24,000. [http://www.hoodcanal.washington.edu/ documents/document.jsp?id=1523]
Sherrod, B. L.; Brocher, T. M.; Weaver, C. S.; Bucknam, R. C.; Blakely, R. J.; Kelsey, H. M.; Nelson, A. R.; Haugerud, Ralph, 2004, Holocene fault scarps near Tacoma, Washington, USA: Geology, v. 32, no. 1, p. 9-12. [http://geology. geoscienceworld.org/cgi/content/abstract/32/1/9]
Sherrod, B. L.; Nelson, A. R.; Kelsey, H. M.; Brocher, T. M.; Blakely, R. J.; Weaver, C. S.; Rountree, N. K.; Rhea, B. S.; Jackson, B. S., 2003, The Catfish Lake scarp, Allyn, Washington—Preliminary field data and implications for earthquake hazards posed by the Tacoma fault: U.S. Geological Survey Open-File Report 03-0455, 1 sheet, with 12 p. text. [http://pubs.usgs.gov/of/2003/of03-455/]
Tabor, R. W.; Cady, W. M., 1978, Geologic map of the Olympic Peninsula, Washington: U.S. Geological Survey Miscellaneous Investigations Series Map I-994, 2 sheets, scale 1:125,000.
Walsh, T. J.; Logan, R. L.; Polenz, Michael, 2003, Geologic map of the McNeil Island 7.5-minute quadrangle, Pierce and Thurston Counties, Washington: Washington Division of Geology and Earth Resources Open File Report 2003-22, 1 sheet, scale 1:24,000. [http://www.dnr.wa.gov/Publications/ger_ofr2003-22_geol_map_mcneilisland_ 24k.pdf]
Table 1. Radiocarbon date, age control data information, Sample LW 527. Lab uncertainty values are one standard deviation (68% confidence interval) and include random errors that can be estimated by the lab but exclude uncertainties that cannot be detected by the laboratory’s analytical procedures. Analyses were performed by Beta Analytic, Inc. (Miami, Florida). Radiocarbon ages are ‘conventional’, that is, adjusted for measured 13C/12C ratio. The geologic unit shown in this table is the unit from which the sample was extracted. The sample was collected from an exposure too small to be shown as a polygon at map scale. Elevations are in feet above mean sea level using lidar data. AMS, radiocarbon analysis by atomic mass spectrometry.
527
RR
W277
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Qptu
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Qp
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