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HomeMy WebLinkAboutger_ms2013-03_geol_map_lofall_24k ger_ms2013-03_geol_map_lofall_pamphlet.pdfMap Series 2013-3. Geologic Map of the Lofall 7.5-minute Quadrangle, Jefferson and Kitsap Counties, Washington GEOLOGIC MAP OF THE LOFALL 7.5-MINUTE QUADRANGLE, JEFFERSON AND KITSAP COUNTIES, WASHINGTON by Trevor A. Contreras, Kimberly A. Stone, and Gabriel Legorreta Paulin WASHINGTON DIVISION OF GEOLOGY AND EARTH RESOURCES Map Series 2013-03 October 2013 DISCLAIMER Neither the State of Washington, nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the State of Washington or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the State of Washington or any agency thereof. This map product has been subjected to an iterative internal review process by agency geologists, cartographers, and editors, and meets Map Series standards as defined by Washington Division of Geology and Earth Resources. INDEMNIFICATION Research supported by the U.S. Geological Survey, National Cooperative Geologic Mapping Program, under USGS award number G12AC20234. The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the U.S. Government. WASHINGTON STATE DEPARTMENT OF NATURAL RESOURCES Peter Goldmark—Commissioner of Public Lands DIVISION OF GEOLOGY AND EARTH RESOURCES David K. Norman—State Geologist John P. Bromley—Assistant State Geologist Washington State Department of Natural Resources Division of Geology and Earth Resources Mailing Address: Street Address: MS 47007 Natural Resources Bldg, Rm 148 Olympia, WA 98504-7007 1111 Washington St SE Olympia, WA 98501 Phone: 360-902-1450 Fax: 360-902-1785 E-mail: geology@dnr.wa.gov Website: http://www.dnr.wa.gov/geology Publications List: http://www.dnr.wa.gov/ResearchScience/Topics/Ge ologyPublicationsLibrary/ Pages/pubs.aspx Washington Geology Library Searchable Catalog: http://www.dnr.wa.gov/ResearchScience/Topics/GeologyPublicationsLibrary/ Pages/washbib.aspx Washington State Geologic Information Portal: http://www.dnr.wa.gov/geologyportal Suggested Citation: Contreras, T. A.; Stone, K. A.; Legorreta Paulin, Gabriel, 2013, Geologic map of the Lofall 7.5-minute quadrangle, Jefferson and Kitsap Counties, Washington: Washington Division of Geology and Earth Resources Map Series 2013-03, 1 sheet, scale 1:24,000, 19 p. text. Published in the United States of America © 2013 Washington Division of Geology and Earth Resources Table of Contents Introduction ........................................................ .............................................................................................................................. 1 Geologic Overview .................................................... ....................................................................................................................... 1 Postglacial Landforms ....................................................... ............................................................................................................... 2 Landslides .......................................................................... ....................................................................................................... 2 Nonglacial Sand Deposits .................................................................... ..................................................................................... 3 Structure ..................................................................................................... ...................................................................................... 3 Lofall Fault Zone ............................................................................................ .......................................................................... 3 Kingston Arch ............................................................................................................ ............................................................... 3 Vinland Syncline..................................................................................................................... .................................................. 4 Description of Map Units ......................................................................................................................... ........................................ 4 Quaternary Unconsolidated Deposits ......................................................................................................................... ............... 4 Holocene Nonglacial Deposits .......................................................................................................................................... 4 Holocene to Latest Pleistocene Nonglacial Deposits ........................................................................................................ 5 Pleistocene Glacial and Nonglacial Deposits .................................................................................................................... 5 Vashon Stade of the Fraser Glaciation (MIS 2) ........................................................................................................ 5 Recessional Deposits ................................................................... ...................................................................... 7 Subglacial Deposits of the Fraser Glaciation.................................................................................. ................... 8 Pre-Fraser Glacial and Nonglacial Deposits .............................................................................................................. 8 Pre-Vashon Glacial and Nonglacial Deposits .................................................................................................. 10 Deposits of the Olympia Nonglacial Interval (MIS 3) .................................................................................... 10 Deposits of the Possession Glaciation (MIS 4) ............................................................. .................................. 11 Deposits of the Whidbey Interglaciation (MIS 5) ........................................................................................... 12 Pre-Fraser Deposits, Undivided ...................................................................................................................... 12 Deposits of the Double Bluff Glaciation (MIS 6)............................................................................................ 13 Tertiary Sedimentary and Volcanic Rocks ....................................................... ....................................................................... 13 Acknowledgments ............................................................................................................ .............................................................. 14 References Cited .................................................................................................................... ......................................................... 14 Appendix A. Pollen Data .................................................................................................................. .............................................. 19 FIGURES (on map sheet) Figure 1. Shaded relief map of the Lofall quadrangle region Figure 2. Comparison of geologic time scale, global magnetic polarity, marine oxygen isotope curve and stages, and ages of climatic intervals in the Puget and Fraser Lowlands for the past 800,000 years TABLES (on map sheet) Table 1. Water well code and equivalent Washington State Department of Ecology tag or tracking number Table 2. Age data for Pleistocene nonglacial deposits MAP SHEET Geologic map of the Lofall 7.5-minute quadrangle, Jefferson and Kitsap Counties, Washington iii iv Geologic Map of the Lofall 7.5-minute Quadrangle, Jefferson and Kitsap Counties, Washington by Trevor A. Contreras1, Kimberly A. Stone1, and Gabriel Legorreta Paulin2 1 Washington Division of Geology and Earth Resources MS 47007 Olympia, WA 98504-7007 2 Universidad Nacional Autónoma de México Instituto de Geografía Ciudad Universitaria, Del Coyoacán cp 04510, México, D.F. INTRODUCTION The map area in the western Puget Lowland straddles Hood Canal between Naval Base Kitsap–Bangor and the Hood Canal Bridge. It includes the northern portion of the city of Poulsbo. Most of the map area is covered by nonglacial sediment and sediment left by alpine glaciers of the Olympic Mountains and the Puget lobe of the Cordilleran ice sheet, which advanced from Canada several times during the Pleistocene Epoch. This mapping was undertaken to identify the area’s geologic hazards, including active faults and landslides, and to delineate the glacial stratigraphy and hydrologic characteristics of the area to assist local government and scientists working on the problem of low concentrations of dissolved oxygen in Hood Canal. Segments of the Seattle and Hood Canal faults have been identified nearby (Blakely and others, 2009; Lamb and others, 2012) and the seismically active Kingston arch projects into the quadrangle. How these faults and structures interact is not well understood. To the south of the quadrangle, the Seattle fault zone has been mapped as far west as Hood Canal (Lamb and others, 2012; Contreras and others, 2012c). Geophysical models by Lamb and others (2012) and Blakely and others (2009) suggest that the Seattle fault zone crosses Hood Canal to the southwest of the map area to connect with the Saddle Mountain fault zone, a complex network of faults southwest of Brinnon. Pratt and others (1997) and Brocher and others (2001) map the Seattle basin to the south of the map area and the Port Ludlow uplift beginning near the north end the map area and continuing to the north (Fig. 1 on map sheet). Persistent landslides continue to damage property and infrastructure in the area, particularly near the Hood Canal Bridge. Many of these slides initiate on silts and clays of the Olympia nonglacial interval. Previous workers have mapped the geological units (Birdseye, 1976a,b; Hanson, 1976; Deeter, 1979; Yount and Gower, 1991; Yount and others, 1993), the hydrogeology (Sceva, 1957; Garling and others, 1965; Grimstad and Carson, 1981; Kahle, 1998); sea level during the Holocene (Eronen and others, 1987), and documented the glacial recessional lake history (Bretz, 1913; Thorson, 1989; Haugerud, 2009b). Throughout the text, we refer to significant sites numbered S1 to S3 and indicated by orange diamonds on the map. Water wells or borings whose logs were used for this mapping are depicted as gray circles and labeled W or B with a number. These wells or borings can be cross referenced with the Washington State Department of Ecology (WADOE) well tag, if applicable, in Table 1 on the map sheet. These sites are often connected with additional data found on the map sheet or in the appendix, including radiocarbon (14C) and infrared stimulated luminescence (IRSL) dates (Table 2 on map sheet) and pollen data (Appendix A). GEOLOGIC OVERVIEW Determining the type of bedrock and thickness of glacial sediments beneath the map area is hampered by limited subsurface data and the structural complexity caused by the intersection of the Kingston arch, Seattle basin, and Seattle fault. The only bedrock exposure in the map area is along Squamish Harbor near Shine (sec. 3, T27N R1E). It was mapped by Hanson (1976) and Yount and Gower (1991) as basalt of the Eocene Crescent Formation. Only a few wells and borings in the Shine area encountered this basalt. However, the Union Oil Co. Pope and Talbot No. 1 2 MAP SERIES 2013-03 18-1 well, drilled in 1972 less than 2 mi east of the quadrangle (Fig. 1 on map sheet), intersected the Blakeley Formation (Fulmer, 1975). Geophysical models (Pratt and others, 1997; Brocher and others, 2001; Lamb and others, 2012; Blakely and others, 2009; Haug, 1998) and geophysical data help constrain depth to bedrock and provide insight into faulting in the area. Previous work (Birdseye, 1976a,b,c; Deeter, 1979; Garling and others, 1965; Grimstad and Carson, 1981; Hanson, 1976; Kahle, 1998; WADOE, 1978, 1979; Yount and others, 1993) described the Pleistocene stratigraphy in the map area and provided subsurface information relating to groundwater. These authors documented repeated Pleistocene glacial incursions that deposited most of the quadrangle’s unconsolidated sediment, and they attempted to classify and correlate these deposits within the Puget Lowland. Additionally, many workers mapped significant nonglacial deposits in the area. The eastern Olympic Mountains consist of basalt of the Eocene Crescent Formation overlain by sandstone and siltstone of the Eocene–Oligocene Lincoln Creek Formation, while to the north, the North Cascades and British Columbia consist of a variety of volcanic, granitic, and metamorphic rocks. We broadly classify the various drifts as ‘Olympic-sourced’ or ‘northern-sourced’. Olympic-sourced drift contains basalt, sandstone, and rare phyllite (in addition to rare reworked granitic and metamorphic clasts), indicating deposition by alpine glaciers of the Olympic Mountains. Northern-sourced drift generally contains granitic and metamorphic rock clasts, suggesting deposition by the Cordilleran ice sheet, but it also typically contains abundant locally derived basalt clasts. The Cordilleran ice sheet overrode the map area, incorporated sediment shed from the Olympic Mountains, and deposited northernsourced sediment in the Olympic foothills, resulting in occurrences of northern-sourced granitic and metamorphic rocks mingled with the dominantly basalt- and sandstone-rich Olympic-sourced drift. Figure 2 (on map sheet) depicts the glacial history of the Puget Lowland and related Marine Isotope Stages (MIS) using variations in the ratio of 18O/16O, which delineate warm and cool climatic intervals and show the changes in climate over the past 800,000 years. We refer to the various marine isotope stages in our discussion and description of the geologic units. Nonglacial deposits were distinguished primarily by the presence of organic matter and ages coincident with inferred nonglacial intervals (Fig. 2). While some nonglacial units contain alluvium that was likely eroded in part by alpine glaciers, the Puget Lowland was ice-free at the time of their deposition. A modern example of this process is the sediment deposited into Hood Canal by the Dosewallips River, which includes a minor amount of sediment derived from the melting Eel Glacier. While this sediment came from an alpine glacial setting, it is being deposited in the Puget Lowland during a nonglacial interval. POSTGLACIAL LANDFORMS Landslides Historic bluff failures have occurred at Termination Point, and mass wasting was again active there during the winters of 1996 through 1999 (W. Gerstel, Qwg Applied Geology, oral commun., 2012; W. J. Perkens, Shannon and Wilson, unpub. report, 2000). At least one home was moved back from the bluff after the 1996–1997 storms reactivated landslides west of the Hood Canal Bridge. More recent damage to Thorndyke Road occurred between Thorndyke Bay and South Point on what appears to be a large deep-seated slope failure. Bluff failure at Termination Point is likely related to tectonic deformation along potentially tectonically active structures associated with the Kingston arch (see Structure, p. 3). This deformation has tilted the nonglacial deposits (unit Qco) south toward the canal by up to 12 degrees, promoting bluff failure. Birdseye (1976b), Deeter (1979), and WADOE (1979) identified numerous landforms as landslides along the bluffs of Hood Canal. We have mapped five main areas as landslides along the shoreline, based on morphology and signs of instability. Two of these locations don’t seem to be deep-seated landslides, because the midbluff slope break corresponds with recessional lake shorelines at similar elevations and the deposits on these benches aren’t landslide material. Instead they appear to be ice-contact stratified drift, suggesting deposition in an ice-marginal drainage environment. These stratified deposits can be unstable where deposited on less permeable silts. Additionally, the bluff and the deposits on the bench can be periodically unstable. At one location north of Thorndyke Bay, we observed instability of recessional outwash sands and gravels deposited on this mid-slope bench, but the Olympiaage sands, silts, and pebble gravels below are not deformed. Instead, landslides occur above the beach bluff, likely failing on fine-grained deposits of the Olympia nonglacial interval. These benches may be the result of erosion along an ice-marginal drainage or stagnant-ice features such as those found in the southern Hood Canal area (Contreras GEOLOGIC MAP OF THE LOFALL 7.5-MINUTE QUADRANGLE, WASHINGTON 3 and others, 2012a,c). These midslope benches parallel Hood Canal on the west side and ring each moderately sized drainage on both sides of the canal between Lilliwaup and Holly (Contreras and others, 2012c). Additional modification of the topography likely occurred during earthquakes, given proximity to active faults and stratigraphy conducive to liquefaction. Determining the true nature of these landforms is beyond the scope of this mapping. Site-specific analysis is required to adequately assess slope stability. Nonglacial Sand Deposits Extensive sand deposited during the Olympia nonglacial interval (unit Qco), reworked by glacial recessional meltwater and modern stream and beach transport, provide abundant sand to this part of Hood Canal. This sand is easily eroded and transported to beaches and is in stark contrast to material available to the south. Mapping in the Lofall quadrangle, we found extensive shallow sandy beaches not encountered in our previous geologic mapping in the southern Hood Canal area. In many places along the bluffs, this sand with interbedded silt extends from sea level to 300 ft above sea level and was generally mapped as advance deposits of the Vashon glaciation by previous investigators (Deeter, 1979; Kahle, 1998; Yount and others, 1993). (See additional discussion under Qco, p. 8.) STRUCTURE It is difficult to model the interaction of the Seattle, southern Whidbey Island, and Hood Canal fault zones in the quadrangle due to the structural complexity, relatively minor changes in geophysical anomalies, and absence of bedrock exposure. Our map provides additional field evidence for the Lofall fault and Port Ludlow uplift (Brocher and others, 2001) and other structures that appear to deform Pleistocene deposits. We suggest that there is a connection between the Kingston arch (Johnson and others, 1994) and the Lofall fault, based on magnetic anomalies and their proximity to one another. Lofall Fault Zone The Lofall fault as named by Brocher and others (2001) bounds the southern edge of the Port Ludlow uplift—an uplift of unknown origin adjacent to and west of the Kingston arch (Pratt and others, 1997). The Port Ludlow uplift is cored by basalt of the Crescent Formation (Arnold, 1906) and shows up in Brocher’s tomographic model and in gravity and magnetic anomalies. Its southern edge approximately parallels the north shore of Squamish Harbor where we map a fault through Squamish Harbor to the north edge of the map that is likely associated with Brocher and others’ Lofall fault. We mapped this fault based on magnetic anomalies, deformation of Pleistocene deposits, and the apparent offset of basalt, which is exposed at the surface to the north of the fault and drops more than 3,000 to the south in the Seattle basin. Magnetic anomalies suggest that a northwest-trending structure connects the Kingston arch and Lofall fault. We mapped the Lofall fault along this anomaly where basalt is exposed at the surface and observed in subsurface logs. This fault appears to have deformed silts of the Olympia nonglacial interval (unit Qco) at the base of the bluff near Termination Point. These deposits dip south by up to 12 degrees and are raised a minimum of 16 ft above modern sea-level in places (significant site S1, sec. 2, T27N R1E). The silts contain articulated marine shells in growth position from a time when sea level could have been much lower than present (Cutler and others, 2003). (See additional discussion under Qco, p. 10.) We believe the dip of these beds is caused by tectonic deformation and contributes to bluff failure. We map a northwest-trending topographic lineament south of the Kingston arch (sec. 14, T27N R1E) that is parallel with the magnetic anomalies. This topographic lineament coincides with a 1,500-ft portion of the shoreline that protrudes 300 ft into Hood Canal. We do not know what this lineament represents. Brocher and others (2001) observed a N–S-trending structure that bounds the Port Ludlow uplift on the east edge, in both their tomographic model and their magnetic and gravity data. We mapped this structure as an unnamed fault along magnetic anomalies because it appears to offset basalt found at the surface on the west side of the canal and basalt found 3,200 ft below sea level in the Union Oil Co. Pope and Talbot no. 18-1 well. Kingston Arch Two exploration wells were drilled to the east of the map area in 1972 along an east-plunging anticline termed the ‘Kingston arch’. Shallow upper-plate seismicity in the area suggests the structure could be active (Pacific Northwest 4 MAP SERIES 2013-03 Seismic Network, http://www.pnsn.or g/), and Mace and Keranen (2012) found faults cutting postglacial sediment on the northern flank of the Kingston arch to the east of the map area. We mapped the Kingston arch where an apparent anticline crosses seismic line 75 of Dadisman and others (1997). We also extrapolated this structure toward the Pope and Talbot no. 18-1 well to the southeast (see Fig. 1 on map sheet), but we are not confident about the orientation or extension of the arch to the west side of Hood Canal and thus did not map it along the western part of the map area. The seismic and magnetic data north of the Kingston arch suggest structural complexity. We speculate that the arch, the Lofall fault zone, and the unnamed N–S-trending structure of Brocher and others (2001) are connected. Vinland Syncline Along the east shore between Vinland and Lofall, we map a northwest-trending syncline in silts, with limbs dipping up to 8 degrees. The deformed silts likely represent the Whidbey Formation or Possession Drift and could be of glaciotectonic origin. We extend the fold to a syncline we noted in seismic line 75 of Dadisman and others (1997) and depict it in the cross section, but have little additional data about this fold. DESCRIPTION OF MAP UNITS Our map shows deposits generally having a thickness of at least 5 ft, although where stiff, impermeable, or geotechnically significant (for example, till or peat), we locally mapped thinner deposits. In most areas, we relied considerably on geomorphology, field relations, subsurface records, and Landsat satellite images to infer lithology. We used the Udden-Wentworth scale (Pettijohn, 1957) to classify unconsolidated sediments. Our mapping on Naval Base Kitsap–Bangor relied heavily on previous geological mapping included in Kahle (1998) and is poorly constrained because we could not access the area. We changed units based on our nearby mapping and new radiocarbon and IRSL dates, and we refined locations using lidar topographic hillshades. We used the time scale of the U.S. Geological Survey Geologic Names Committee (2010). Most radiocarbon age estimates are stated as conventional carbon-14 ages and include “yr BP” after the date. In places, calibrated dates from other reports are included and “cal yr BP” is noted after the date. A USGS 7.5-minute topographic map of the Lofall quadrangle was used as a base map, but contact locations were generally refined by reference to a LiDAR (light detection and ranging, hereafter lidar) image, aerial photos, and field observations. Quaternary Unconsolidated Deposits HOLOCENE NONGLACIAL DEPOSITS ml Modified land—Clay to boulder gravel and diamicton; locally derived but mixed and reworked by excavation and (or) redistribution that notably modifies topography; shown where fairly extensive, masking underlying geology, and geotechnically significant (>5 ft); excludes roads (except where connected to a larger modified area, such as the Hood Canal Bridge). Qa Alluvium—Sand to cobble gravel, locally includes silt, clay, and peat; typically gray and generally unweathered; loose; clasts subrounded; moderately to well sorted; stratified to massive; includes some lacustrine and beach deposits and may include unrecognized older glacial outwash; consists of reworked glacial and nonglacial deposits. Qb Beach deposits—Sand to boulder gravel with shells and driftwood; gray to brown-gray; clasts moderately to well rounded; may be well sorted; loose; derived from shore bluffs, streams, and underlying deposits. This unit is commonly too small to show at map scale and unrepresented in favor of mapping more geologically significant units. We suggest that the extensive beach deposits in the northern Hood Canal area are a result of easily eroded sand from extensive nonglacial deposits derived from the central Cascades (see additional information under Qco, p. 10). This deposit is probably less than 6,000 years old, based on relative sea level curves of Eronen and others (1987) and Dragovich and others (1994), and suggests aggradation of beach deposits as sea level rose. Qam Relict alluvium and salt-marsh deposits—Silty sand, silt, and pebble to cobble gravel, locally includes silt, clay, peat, and detrital wood; typically tan and generally unweathered; loose; clasts subrounded; GEOLOGIC MAP OF THE LOFALL 7.5-MINUTE QUADRANGLE, WASHINGTON 5 moderately to well sorted; stratified to massively bedded; may include older tide-flat deposits above current salt marsh. This unit is less than 6,000 years old and has been used to study relative sea level (Eronen and others, 1987; GS1, sec. 32, T28N R1W) and tsunami deposits (Bourgeois, 2008) because of its unique location at Shine and extensive peat deposits that have recorded sea level fluctuations, tephra, and pollen during the Holocene. HOLOCENE TO LATEST PLEISTOCENE NONGLACIAL DEPOSITS Qp Peat—Peat, muck, and organic-rich silt and clay; dark brown to black; very soft to medium soft; typically in closed depressions. Unit Qp includes upland wetlands and flat surfaces in closed basins, except where standing water was identified. We mapped some peat on the basis of topography and aerial photos. Unit Qp overlies Vashon Drift and older glacial deposits and typically is Holocene but may include some late Pleistocene deposits. Qls Landslide deposits—Diamicton; loose or soft; clasts subangular to rounded; unsorted to poorly sorted; nonstratified, but may locally retain primary bedding; includes exposures of underlying units in scarp areas. This unit is mapped along shorelines where steep bluffs tend to be unstable. Absence of a mapped slide does not imply absence of landslide hazard; some slides are too small to show at map scale. Where mapped, we had additional evidence to infer landslide movement, other than geomorphology. This often includes historical accounts of movement and damaged infrastructure. An example of this is near Termination Point during 1996–1997 storms, where bluff failure threatened some homes. Many deepseated landslides appear to initiate on fine-grained sand and silts of the Olympia nonglacial interval. We map some landforms that could be ice-marginal drainage channels or shorelines of recessional lakes as landslide deposits, such as the bench north of South Point (secs. 9 and 16, T27N R1E). We are uncertain if they are deep-seated landslides, but other signs of instability encouraged us to map them as such. A similar example is just north of Thorndyke Bay (sec. 19, T27N R1E), where the mid-slope bench is covered with sand and gravel and is unstable. However, the Olympia-age deposits at the base of bluff do not appear disturbed, as would be expected if the landform were a deep-seated landslide. This unit is mostly Holocene but may include some late Pleistocene deposits. Qmw Mass-wasting deposits—Pebble to boulder gravel, sand, and diamicton, with minor sand and gravel beds where modified by stream processes; loose; clasts subrounded; poorly to moderately sorted. Unit Qmw represents colluvium-covered slopes and includes debris fans, alluvial fans, and landslides where lidar shaded-relief maps suggested mass-wasting deposits large enough to show at map scale, but where the landform is not clearly a landslide. Absence of a mapped mass-wasting deposit does not imply absence of slope instability or hazard. This unit is mostly Holocene but may include some late Pleistocene deposits. Qaf Alluvial fan deposits—Sand and gravel and debris-flow diamicton; gray, weathering to brownishorange; loose; clasts subrounded to rounded; typically poorly to moderately sorted; massive to weakly stratified. This unit forms concentric lobes where streams emerge from confining valleys. Debris flows and debris torrents may be a geologic hazard on some alluvial fans. For example, fan aggradation occurred during the December 2007 storms. This aggradation added material to fans in the area, damaged homes and infrastructure, and covered beaches and shellfish beds (Sarikhan and others, 2008). Unit Qaf is predominantly Holocene but likely locally includes some latest Pleistocene recessional deposits of the Fraser glaciation. PLEISTOCENE GLACIAL AND NONGLACIAL DEPOSITS Vashon Stade of the Fraser Glaciation (MIS 2) The Puget lobe of the Cordilleran ice sheet covered the map area between about 17,000 and 15,700 cal yr ago, based on work to the southwest in the Hoodsport quadrangle (Polenz and others, 2012a). The ice filled the Puget Lowland to an elevation of 3,100 ft in the adjacent Brinnon quadrangle (Polenz and others, 2012b) and approximately 2,200 ft in the Eldon quadrangle to the south (Contreras and others, 2012a). Vashon drift in the map area is mostly an 6 MAP SERIES 2013-03 unweathered, discontinuous, thin layer of subglacial melt-out till or ice-contact stratified drift (stagnant-ice) deposits with little lodgment till. Porter and Swanson (1998) suggested that deglaciation occurred prior to 16,420 cal yr BP at Lake Carpenter (~5 mi east of the map area). In the map area, the Puget lobe may have stagnated, causing the ice sheet to abruptly collapse into marine water at the Strait of Juan de Fuca (Ralph Haugerud, USGS, oral commun., 2012). This event was inferred from the lack of recessional moraines in the central Puget Lowland and the prevalence of stagnant-ice features such as eskers and kame and kettle topography. An extensive recessional lake system was first proposed by Bretz (1913), based on the presence of alluvial flats and shorelines formed as recessional meltwater was impounded in front of receding ice. Numerous lakes formed as ice melted from south to north. These lakes were graded to spillways to the south and eventually to the north. By the time parts of the map area were ice free, Lake Russell (named by Bretz) had formed. It was graded to the Black Lake spillway near Olympia. As ice continued to melt and provide additional spillways, Lake Bretz (Waitt and Thorson, 1983) drained to the north at Port Discovery and had progressively lower spillways (Haugerud, 2009b). Bretz noted deposits in Big Valley graded to lowering lake levels and termed this the Poulsbo channel, extending from Poulsbo to Hood Canal. Thorson (1981, 1989) studied the isostatic uplift of the area using recessional lake levels, which are represented by the modern elevations of delta deposits formed in these recessional lakes. Thorson (1989) determined that these deposits were progressively uplifted to the north by isostatic rebound as the Puget lobe melted. He calculated a postglacial isostatic rebound gradient rising to the north at approximately 0.85 m/km (4.5 ft/mi). Within the map area, isostatic rebound is approximately 80 m (260 ft)(Thorson, 1989) of total uplift since deglaciation and less than 30 m (100 ft) since the marine limit (highest relict marine shoreline) was reached, when marine waters entered the Puget Lowland as the ice melted (Dethier and others, 1995). Haugerud (2009b) mapped extensive outwash surfaces graded to various recessional lake levels on the Kitsap Peninsula. In the map area, he mapped outwash flats east and southeast of Breidablick that graded to Lake Russell at about 380 ft elevation. He also mapped recessional delta deposits near Breidablick, locally mined for sand and gravel, as graded to Lake Bretz. Haugerud inferred that (1) outwash channels in Big Valley and around Breidablick were graded to declining levels of Lake Bretz, and (2) the area just to the east of Big Valley was covered in ice at this time, based on the lack of channels to the east, and this ice forced down-cutting and erosion of the channel at Big Valley. Mapping to the southeast on Bainbridge Island (Haugerud, 2005) and in the Suquamish quadrangle (Haugerud and Troost, 2011) depicted recessional sediments that were deposited in marine water at a sea level lower than modern and have since been isostatically uplifted. Haugerud (2009b) also suggested that the recessional delta at Lofall was graded to the marine limit at this time and is now isostatically uplifted. We mapped the Lofall delta near Kitsap Memorial State Park as outwash deposits (unit Qgo), but did not map it specifically as marine deposits because we didn’t find evidence of marine deposition or find it necessary to map this deposit as a separate unit based on the possibility that it was deposited into and graded to marine water. We also acknowledge that the southern boundary of map area intersects the marine limit and that marine emergence gravels are found, but they are not thick or extensive enough to depict at map scale. These emergence gravels are the result of sediment deposited into marine water and later uplifted by isostatic rebound. Polenz and others (2013) found evidence for emergence gravels along Liberty Bay in the Poulsbo quadrangle but were unable to find convincing and extensive deposits to depict at map scale. They suggest that shorelines in the vicinity may represent this marine emergence. Haugerud and Troost (2011) map emergence gravels to the southeast of the map area. We suspect that benches formed within modern drainages are graded to recessional lake levels. Many of these benches have what look like deep-seated landslide morphology. However, we think these landforms are the result of erosion and deposition during ice recession instead of mass wasting. These assertions are based on the following: (1) much of the landscape development occurred as the ice melted at the end of the glaciation, prior to vegetation, and we know that little modification has occurred since, because many surficial glacial landforms are preserved in this portion of the Puget Lowland, and (2) after the meltwaters cut down through existing deposits and recessional lakes covered the area, deposits along their shorelines formed benches at the various elevations. Examples of these deposits are in the unnamed stream drainage west of Breidablick. In the bottom of the drainage, the silts (unit Qcw) appear undisturbed and the bench appears to be graded to an elevation of about 125 ft—an elevation similar to other benches nearby. The materials making up the bench are sands and pebble gravels that do not appear to be colluvium derived from the surrounding drainage walls. If they were, they would be primarily sand and silt fragments. We suggest these benches are not landslides, but actually material that serves to buttress or support the walls of the drainage. GEOLOGIC MAP OF THE LOFALL 7.5-MINUTE QUADRANGLE, WASHINGTON 7 Recessional Deposits Mapped recessional deposits of the Fraser Glaciation are units Qgoaf, Qgo, Qgog, Qgos, Qgic, and Qge. Porter and Carson (1971), Porter and Swanson (1998), and Haugerud (2009a) noted that deglaciation following the Vashon stade in the southern Puget Lowland probably began with stagnation of the ice sheet: ice thinned, stopped moving, and melted in place, leaving behind subglacial drainages and other ice-contact features. We find consistent evidence of this in the Lofall quadrangle; Polenz and others (2009a,b), Derkey and others (2009), and Contreras and others (2010, 2012a,b) depict stagnant-ice features throughout the area. Previous mapping assumed that the area is covered with Vashon-age lodgment till; however, shaded relief on lidar images and field work show that stagnant-ice deposits are more extensive at the surface than previous mapping suggests. The apparent roughness in topography on and near drumlins coincides with locations of stagnant-ice deposits and lack of lodgment till. We did find areas with mappable thickness of well-developed lodgment till that we mapped as unit Qgt. These deposits are likely younger than 16,420 cal yr BP, based on work by Porter and Swanson (1998) for the ice retreat from the Puget Lowland. Qgo Vashon recessional outwash—Sand and cobble to pebble gravel, pebbly sand, and minor silt; gray, weathering to tan; loose; clasts subangular to rounded; moderately to well sorted; typically crudely stratified; derived from both northern and local sources, including pre-Vashon nonglacial deposits; a few to tens of feet thick. Unit Qgo was deposited by glacial meltwater outwash channels in isolated basins on the fluted upland surface. It is difficult to separate from units Qgic, Qgog, and Qgos, resulting in approximate boundaries between units. Locally divided into: Qgoaf Vashon alluvial fan deposits—Sand and pebble gravel, silt, and cobbles; loose; subrounded; moderately to poorly sorted; stratified; form concentric lobes where outwash streams emerge from confining valleys. The relict fans do not appear to receive sediment and are often incised by modern streams. The unit is mostly mapped along the eastern edge of the map in or near Big Valley. The unit is recognized where lidar reveals dissected relict-fan morphology, often smoothed by recessional lakes. The fans were formed as the glacial ice melted or shortly thereafter, often eroding pre-Vashon nonglacial deposits, specifically sand from unit Qco. Qgog Vashon recessional outwash gravel—Pebble and cobble gravel, sand, and local silt; gray to tan, locally iron-stained to red-brown and yellow, but clasts typically unweathered; clasts moderately to well rounded; moderately to well sorted; loose; typically 10 to 100 ft thick. The unit is mapped in outwash channels graded to recessional Lake Bretz as water drained to the north to Discovery Bay at approximately 200 to 300 ft in elevation. Unit Qgog rests on older nonglacial deposits and includes rip-up clasts of silt and peat eroded from these deposits. It can be differentiated from unit Qgo where recent gravel mining suggests viable deposits, as in the northwest corner of the map area, and extended on the basis of channel morphology. Qgos Vashon recessional outwash sand—Sand, with minor pebble gravel and local silt; gray to tan; loose; clasts moderately to well rounded; moderately to well sorted; typically 5 to 50 ft thick. Mapped in outwash channels graded to recessional Lake Bretz or earlier lakes as water drained to the north into Discovery Bay. It can be differentiated from units Qgo and Qgog where recessional deposits are mostly sand. Haugerud (2009b) mapped this unit as delta fronts near Lofall where it appears to be the sand facies of these deltas. Unit Qgos was deposited by meltwater into recessional lakes or marine waters, then uplifted due to isostatic rebound. We mapped it in the vicinity of Lofall and Shine and in one location on the eastern margin of the map area where extensive fluvial sand deposits were observed but sufficiently higher in elevation than expected from Lake Bretz. Qgic Vashon ice-contact deposits—Diamicton, cobbly pebble gravel, silty sandy till, silty pebble gravel, and pebbly sand, with minor sand and silt; yellow-tan to gray; loose to very dense; clasts subangular to subrounded; variously sorted; massive to well stratified; accompanied by stagnant-ice features, such as kettles, hummocky topography, eskers (separately mapped as unit Qge where distinct), and subglacial or subaerial outwash channels. Unit Qgic ranges in thickness from a few to tens of feet and is mapped over a 8 MAP SERIES 2013-03 large part of the fluted upland surface on both sides of Hood Canal. Where lacking more recognizable stagnant-ice features, unit Qgic is commonly a friable, but compact subglacial melt-out till that appears permeable. It is typically distinguished from lodgment till by its apparent roughness in lidar shaded-relief and its association with other stagnant-ice features. It crudely corresponds with areas mapped by Haugerud (2009b) as pockmarked glaciated surface (his unit gp) on the Kitsap Peninsula. Unit Qgic lies directly on top of older, possibly early Fraser, alpine drift or nonglacial sand and silt deposits of the Olympia nonglacial interval. It rarely is found on recognizable Fraser-age advance glacial deposits, and in this quadrangle does not appear to have a lodgment till beneath as Haugerud (2005) also observed on Bainbridge Island. Though it can be found in fluted drumlins (indicating subglacial emplacement) as a diamicton, it lacks subhorizontal foliation, is permeable, and is less competent than a ‘typical’ subglacial lodgment till. It may be related to tills found by Laprade (2003) in the Seattle area. See additional discussion in Contreras and others (2012b,c). Locally divided into: Qge Vashon esker deposits—Pebble to cobble gravel and sand; tan to brown; loose; clasts moderately to well rounded; typically well sorted; commonly with a thin film of oxidized cement between grains; forms low, elongate, sinuous hills; mapped in areas that were occupied by stagnant ice in the northwest portion of the map. Eskers near Thorndyke Lake appear to be truncated below 260 ft in elevation, likely because they were modified by recessional lakes. Subglacial Deposits of the Fraser Glaciation Qgt Vashon lodgment till—Mixture of clay, sand, and gravel (diamicton) with rare lenses of sand and gravel; gray, weathering to yellow-tan; dense; matrix-supported; unsorted with disseminated cobbles in a siltsand matrix; unstratified; locally contains a friable shear fabric as a result of ice shear. Clast types include both northern- and Olympic-sourced rounded to subangular clasts. Unit Qgt thickness ranges from 1 to 20 ft, but is commonly less than 5 ft. Till is typically found on fluted upland surfaces where drumlins are smooth, wide, and well defined. Unit Qgt is typically covered by 1 to 6 ft of loose ablation till and is generally in a sharp, unconformable contact with underlying units, which are most commonly older nonglacial deposits or early Fraser alpine outwash. Pre-Fraser Glacial and Nonglacial Deposits Prior to the Vashon stade of the Fraser glaciation, both Cordilleran and Olympic-sourced glaciers deposited drift in the Lofall area. During nonglacial intervals, rivers of the Olympic Mountains and the central Cascades aggraded and deposited thick packages of sand, silt, and pebble gravel (locally from the Olympic Mountains). Bretz (1913) believed that nine-tenths of the Pleistocene deposits exposed above sea level in the Puget Lowland are nonglacial deposits. The majority of the deposits found along bluffs in our current mapping area are nonglacial or from older glaciations and are not the result of the Vashon glaciation. The deposits directly below the surface sculpted by the Puget lobe do not appear to be from this ice mass, but from the Olympics and central Cascades during the Olympia nonglacial interval (MIS 3) or older stages. New ages suggest that these older nonglacial sediments dominate the stratigraphy north of the Seattle fault zone along Hood Canal and include deposits of the Whidbey Formation and Olympia nonglacial intervals. Clague (2000) suggested that the most extensive Quaternary stratigraphic units in the Canadian Cordillera were deposited during ice sheet growth because there was an increase in sediment production in the alpine areas. This sediment was flushed from the mountains as alpine glaciers advanced and was deposited by aggrading streams as base level rose. Our dates suggest that the Puget Lowland was filling with sediment during the Olympia nonglacial interval (MIS 3)(Fig. 2), at least 12,000 years before the Puget lobe began advancing from British Columbia (Clague and others, 1980), but while alpine glaciers were active in the mountains surrounding the Puget Lowland. This is based on our youngest radiocarbon date from a well preserved piece of wood in unit Qco at Thorndyke Bay (GD3; sec. 25, T27N R1W). On the Toandos Peninsula in the Seabeck quadrangle to the southwest, radiocarbon dates and stratigraphy suggest that alpine glaciers produced outwash and drift prior to the Puget lobe arriving in the area (Polenz and others, 2013). Additionally Polenz and others mapped multiple glacial drifts, suggesting multiple glaciations recorded in the deposits of the area. GEOLOGIC MAP OF THE LOFALL 7.5-MINUTE QUADRANGLE, WASHINGTON 9 We relied on four finite radiocarbon age estimates taken from the extensive nonglacial deposits of interbedded sand and silt (unit Qco) to interpret much of the Lofall stratigraphy. These ages correlate with MIS 3, falling within the age range of the Olympia nonglacial interval, spanning 60,000 to 15,000 14C yr BP (Troost, 1999). We also collected three luminescence samples, but the results were not available until after most of the mapping was complete, and there is some disagreement between the radiocarbon and luminescence dates. In the end we relied on carbon analyses within the Lofall map area and the Seabeck quadrangle (Polenz and others, 2013) that suggest Olympia ages. The disagreement between dating methods occurred at two locations where four ages were obtained. The samples were thought to be taken from the same material but provided vastly different results, the two carbon samples (GD3, sec. 25, T27N R1W; GD5, sec. 26, T27N R1E) were found to be substantially younger than the luminescence samples (GD4, sec. 26, T27N R1E; GD8, sec. 25, T27N R1W) at both sites. Explanations for the discrepancy include: (1) the samples were taken from different strata at GD4 and GD5 and an unrecognized unconformity exists there; however, we are confident that GD3 and GD8 were taken from the same strata; (2) the carbon samples are contaminated with younger carbon, giving erroneously younger results; and (3) the luminescence samples were not completely reset prior to being deposited. Given the uncertainties, we relied on the stratigraphy, abundant organic material, and radiocarbon results, which suggest these deposits were formed during the Olympia nonglacial interval, although they may be older and belong to the Possession Drift. It is possible the two luminescence dates are correct and the sand deposits we’ve mapped as deposits of the Olympia nonglacial interval (unit Qco) on the east side of Hood Canal are actually the result of the Possession glacial retreat, as they are stratigraphically above Possession Drift. As mapped in this report, deposits of the Olympia nonglacial interval are represented by beds of well-sorted, homogeneous quartz- and potassium-feldspar-rich sand and silts interbedded with pebble gravel and sand from the Olympic Mountains when the Puget Lowland was ice free. The abundant monocrystalline quartz, significant potassium feldspar, and minor hornblende and pyroxene grains in these beds suggest they are equivalent to ancient Snoqualmie and Skykomish River–provenance alluvium (Dragovich, 2007, 2010, 2013) and are not the result of an advancing Cordilleran ice sheet (Joe D. Dragovich, DGER, oral commun., 2013). The sands appear to have been deposited in a lacustrine or marine environment without dropstones. They are often massive, locally crossbedded, and may be analogues to part of Booth’s “great lowland fill” (1994) but are too old to have been deposited in a proglacial lake impounded by the advancing Puget lobe. Had they been deposited into a proglacial lake, they would be younger than the 18.3 ±0.17 ka date that constrains the advance of the Puget lobe into the Georgia depression (Clague and others, 1980). These sands were deposited during the Olympia nonglacial interval and not during the Vashon stade of the Fraser glaciation. Deeter (1979) showed that the now abandoned Kitsap Formation (Garling and others, 1965) was deposited over multiple nonglacial and glacial intervals and included deposits of Whidbey, Possession, and Olympia ages. We suggest there is some evidence for Possession Drift (unit Qgdp) deposited on silt of the Whidbey Formation between elevations of 200 to 275 ft on the Kitsap Peninsula. This drift consists of northern-sourced pebble-gravel diamicton and dropstones on top of silt and appears discontinuous—suggesting erosion prior to deposition of Olympia nonglacial deposits above. A good exposure of this drift near its contact with the Whidbey Formation (unit Qcw) is at significant site S3 (sec. 25, T27N R1E)(elevation 255 ft). The drift included dropstones of various volcanic lithologies and a northern-sourced diamicton we infer to be Possession Drift because it is stratigraphically on top of the Whidbey Formation or advance outwash. The exposure appears to be stratigraphically below deposits we’ve mapped as deposits of the Olympia nonglacial interval to the northeast at age sites GD4 (sec. 26, T27N R1E) and GD5 (sec. 26, T27N R1E), but, as discussed above, could be a part of the Possession Drift. Previous work to the south in the Holly quadrangle (Contreras and others, 2012c) and in the Poulsbo quadrangle (Polenz and others, 2013) found similar stratigraphy at similar elevations. Mapping of Possession Drift in the quadrangle (Easterbrook and others, 1967) is based on one radiocarbon age estimate on marine shells from nonglacial deposits of the Olympia nonglacial interval. The date from the shells could be erroneous, but we believe that the deposits they were found in correlate with other deposits of the Olympia nonglacial interval throughout the map area. The shells found along Squamish Harbor (age site GD2; sec. 2, T27N R1E) were deposited on the drift that we interpret as Possession Drift. We also find this drift on top of silts inferred to be Whidbey Formation on the east side of Hood Canal. Laminated beds of silt, sand, and clay of the Whidbey Formation in the map area below approximately 200 ft in elevation. We based our correlation primarily on OSL and IRSL age estimates to the south in the Holly and Eldon quadrangles (Contreras and others, 2012a,b). No convincing evidence for deposits of the Whidbey Formation exists 10 MAP SERIES 2013-03 on the west side of Hood Canal in the map area; organic matter and shells dated for this study provided ages too young to be considered part of the Whidbey Formation. Pre-Vashon Glacial and Nonglacial Deposits Qpf Pre-Vashon silt—Silt, clay, and some sand and pebble gravel; brown or gray; compact; unstratified to well stratified; generally thought to be glaciolacustrine but may include nonglacial deposits; mapped along the southern map boundary, where Polenz and others (2013) map silt below Vashon till in the Poulsbo quadrangle, but were unable to confidently assign it to Vashon advance deposits or older nonglacial deposits. The unit is likely equivalent to unit Qco or Qcw as mapped in this quadrangle, but without age control. Qpos Pre-Vashon northern-sourced glacial outwash sand—Sand, silt, clay, and pebble gravel; brown or gray; compact; unstratified to well stratified; mapped along the southern map boundary, where Polenz and others (2013) map glacial outwash sand below Vashon till in the Poulsbo quadrangle, but were unable to assign it to Vashon advance deposits or older nonglacial deposits. The unit is likely equivalent in age to unit Qco as mapped in this quadrangle, but without age control. Qpu Undivided Quaternary sediment older than Vashon till—Sandy pebble gravel and sand with mud interbeds; compact; gray, with surficial iron staining and some light-brown mud beds; mapped along the southern quadrangle boundary within Naval Base Kitsap–Bangor (‘Bangor Naval Base’ on map sheet), where Polenz and others (2013) map undifferentiated deposits in the Poulsbo quadrangle. The unit is likely equivalent to unit Qcw or Qgdp as mapped in this quadrangle, but without age control or access to exposures on the base. Deposits of the Olympia Nonglacial Interval (MIS 3) Qco Olympia nonglacial deposits—Sand, silt, pebble gravel, minor organic matter-rich silt and peat, and rare marine shells; tan and gray to light orange and dark brown; medium dense to loose; clasts subangular to subrounded; well stratified and sorted; laminated to very thickly bedded or massive; locally crossbedded and ripple marked. Sand grains are dominated by monocrystalline quartz, plagioclase feldspar, potassium feldspar, minor hornblende, and lithic grains. On the west side of Hood Canal, the unit is interbedded with sand and pebble gravel composed of basalt and sandstone lithic grains derived from the Olympic Mountains. Unit Qco is as much as 280 ft thick and is distributed throughout the map area. On the east side of Hood Canal it is found above approximately 250 ft in elevation; on the west side, down to sea level. The unit was deposited into a lacustrine environment or meandering flood plain that included marine water at least in one location (marine shells at age site GD2; sec. 2, T27N R1E). Rare oxidized ripple marks near the top of the unit (age site GD7; sec. 9, T26N R1E) suggest shallow water deposition. We did not observe gravel facies on the east side of Hood Canal, but suspect they must extend as far east as Bainbridge Island where Deeter (1979) found Olympic-sourced gravels and Haugerud (2005) termed them the University Point beds and assigned them to the Olympia nonglacial interval. Deeter believed that alpine outwash from the Olympics required a glacial setting, but Haugerud thought the radiocarbon dates, good organization of the deposits, and peat suggested slowly aggrading streams. Polenz and others (2013) also found extensive alpine outwash to the south in the Seabeck and Poulsbo quadrangles. The dominant sand facies of this unit contains more potassium feldspar and monocrystalline quartz than would be expected from British Columbia and is petrographically indistinguishable from nonglacial sands observed across several quadrangles on the east side of the Puget Lowland (Dragovich and others, 2007, 2009a,b, 2010, 2011, 2012). The source of these deposits is apparently north Cascades intrusive granitic rock, such as found in the Snoqualmie, Index, and Grotto batholiths (Dragovich, oral commun., 2013). This implies that sediment was transported west across the Puget Lowland and deposited against the base of the Olympic Mountains at the same time as rivers draining the Olympics were depositing alluvium as far east as Bainbridge Island (Deeter, 1979; Haugerud, 2005). To explain the deposition of fluvial and lacustrine deposits above modern sea level, previous workers have suggested that the Puget Lowland became a closed depression once the Puget Lobe crossed the GEOLOGIC MAP OF THE LOFALL 7.5-MINUTE QUADRANGLE, WASHINGTON 11 Strait of Juan de Fuca during the Vashon stade of the Fraser glaciation. This effectively dammed the Puget Lowland, forming a proglacial lake and filling it with silt and sand outwash (Booth, 1994; Booth and Goldstein, 1994). In the map area, our age data suggest that this part of the Puget Lowland was filling with fluvial and lacustrine sediment a minimum of 12,000 years before the Puget lobe blocked the Strait. Without an ice sheet blocking the outlet of the Puget Lowland, we struggle to find the mechanism to form a lacustrine environment when sea level would have been much lower than present. (Cutler and others, 2003). We suggest that alpine glaciers in both the Olympics and Cascades were actively shedding sediment into the Puget Lowland during MIS 3, causing the lowland to aggrade in a lacustrine and lowgradient fluvial environment suggested by the deposits. Alpine outwash could have aggraded to the point that the lowland could vacillate between lacustrine and fluvial systems. We believe it was possible for the ancestral Skagit and Snohomish Rivers to aggrade extensive deltas because the modern basins provide more than half of all annual sediment to the Puget Sound (Czuba and others, 2011), so these rivers could have impounded the outlet to the Strait during MIS 3. Similar aggradation during this nonglacial interval has been reported in British Columbia and the Willamette Valley (Clague and others, 2005; O’Connor and others, 2001). However, sediment discharge from these rivers during MIS 3 is unknown, so suggesting aggradation of these rivers is speculative. Other mechanisms could include the Port Ludlow uplift and Kingston arch blocking access to the Pacific Ocean. Clague (1977) suggested aggradation in the Georgia depression occurred in a short period of time and gave estimates, but they relied on little data. We cannot currently postulate a better mechanism for raising the base level of the Puget Lowland and depositing these sands and silts during this nonglacial interval, but our dates suggest this is what occurred within the map area. Unit Qco was deposited on northern-sourced drift, thought to be Possession Drift, in the vicinity of Squamish Harbor and is covered by Vashon Drift on an erosional unconformity. We did not find extensive Vashon advance deposits, for example, the Esperance Sand Member of Vashon Drift (Newcomb, 1952), on top of this unit. Silt beds at significant site S1 (sec. 2, T27N R1E) dip 12 degrees to the south, which may be the result of deformation along a fault associated with the Kingston arch. The tilting contributes to failure of the bluff at this location. Tectonic uplift may also be partially responsible for the discrepancy in base level between modern sea level and a much lower global sea level during MIS 3 (Dragovich, oral commun., 2013). Clague and others (2005) found Quadra Sand (type locality British Columbia; Clague, 1976, 1977) at elevations above sea level but suggested that glacio-isostatic depression of the crust by the expanding Cordilleran ice sheet was responsible for this apparent high base level. We do not expect depression of the crust this far south during the Olympia nonglacial interval, but the base level could have been higher due to aggradation of rivers in the Puget Lowland. Deposition into a basin with a high base level is supported by other nonglacial deposits found above sea level in nearby quadrangles (Contreras and others, 2012a; Polenz and others, 2012b). Polenz found sediments at the ‘Brinnon delta’ that were deposited in a lacustrine environment and had OSL age estimates indicating Olympia age. Local reports of mastodon remains are from this unit (Carson, 1980). Two pollen samples taken for this study are characteristic of an environment colder and drier than today (Estella B. Leopold, Univ. of Wash., written commun., 2013)(significant sites S1, sec. 2, T27N R1E, and S2, sec. 25, T27N R1W, in Appendix A). This pollen is similar to pollen found at Strawberry Point (Hansen and Easterbrook, 1974) and is consistent with the stratigraphic position, having Possession Drift below. Reports of poor water quality— methane gas and oil—near Four Corners (sec. 26, T27N, R1E) likely stem from organic matter in this unit. Silt at the base of the unit contains articulated marine shells (Clinocardium nuttellii, Nuculana pernula, Macoma moeta) in growth position that are characteristic of shallow, circum-Arctic waters (Elizabeth A. Nesbitt, Burke Museum, written commun., 2012). The shells were dated at 37,840 ±380 yr BP (age site GD2, sec. 2, T27N R1E), which places them in the Olympia nonglacial interval, but the shell date is somewhat questionable due to the possibility of erroneous dates from marine shells (see Table 2 on map sheet). The Olympia nonglacial interval occurred between 15,000 and 60,000 yr BP (Fig. 2). Deposits of the Possession Glaciation (MIS 4) Qgdp Possession Drift—Diamicton and sand to pebble gravel with minor silt; coarsens upward from silt and sand with dropstones to pebble gravel and diamicton; includes metamorphic and granitic clasts; light brown to gray; clasts subrounded to rounded; moderately to well sorted and unsorted; moderately 12 MAP SERIES 2013-03 stratified and medium to thickly bedded; very dense and massive. The maximum observed thickness of unit Qgdp is about 250 ft along the eastern border of the map area; otherwise, it is a thin, discontinuous diamicton. The unit is exposed stratigraphically above the nonglacial unit Qcw in a few drainages on the east side of Hood Canal. On the west side of Hood Canal in the vicinity of Squamish Harbor (secs. 2–4, T27N R1E), exceptional exposures at the base of the bluffs are northern-source diamicton, commonly up to 15 ft thick, with laminated marine silts of the Olympia nonglacial interval (unit Qco) or recessional outwash deposited on top. While lacking obvious shells, the unit’s texture and hackly fracture pattern may indicate marine water deposition similar to Possession glaciomarine drift to the east in the Port Gamble quadrangle (Brett Cox, USGS, oral commun., 2013). As mapped, unit Qgdp may include unrecognized older or younger drift east of Big Valley (secs. 2 and 11, T26N R1E) because no age control is available. We assumed the few exposures of northern-sourced drift along the west shore of Hood Canal, found under deposits of the Olympia nonglacial interval, were Possession Drift. We infer the age for this unit from multiple radiocarbon dates that are less than 37,840 yr BP found above it (date sites GD2, sec. 2, T27N R1E; GD3, sec. 25, T27N R1W; GD5, sec. 26, T27N R1E). However, there could be an unrecognized erosional unconformity between the dated material and the diamict, making the diamict much older than Possession age. From Breidablick southwest to the southern map boundary, poor exposure and access make the unit as mapped, largely inferred. The age range for Possession Drift is thought to be 60 to 80 ka (Easterbrook and others, 1967). Deposits of the Whidbey Interglaciation (MIS 5) Qcw Whidbey Formation—Silt, clay, and sand; light gray to light brown; dense and stiff; clasts typically subangular to subrounded; well stratified and well sorted; thinly laminated to very thickly bedded. Some portions of the unit contain preserved organic materials recorded in well reports. Unit Qcw appears to have an average thickness of about 250 ft, with a maximum of about 325 ft, and extend to approximately 100 ft below sea level. This unit is found along the eastern shores of Hood Canal between Lofall and the southern map boundary. It appears to represent nonglacial prodelta deposits that received sand, silt, and clay from deltas to the north and east. Contact relations are unclear, but well reports and rare exposures suggest that thin, discontinuous, oxidized northern-sourced glacial drift is present above this unit; we assume this is Possession Drift (MIS 4). The base of this unit is not well exposed in the map area. However, exposures along the bluffs north of Vinland (sec. 28, T27N R1E) suggest deposition directly on northern-sourced drift inferred to be Double Bluff Drift (MIS 6) or older (unit Qpd). We cannot explain the apparent high base level needed to deposit these nonglacial sediments at elevations as much as 200 ft above modern sea level, but suggest that tectonic uplift or aggradation during nonglacial intervals may be responsible. Unit Qcw is a poor aquifer; water wells are typically drilled through it and developed in older outwash below. Laminated clay in unit Qcw makes it a hydrologic barrier, causing springs at the top of the unit. Silts and clays along Big Valley are probably Whidbey Formation. Sparse age data from unit Qco imply the relative age, but we have no direct age estimates for this unit from within the map area. We rely on luminescence age estimates from nearby quadrangles to infer the age of this unit; they range between 82.5 ±3.89 ka and 134 ±9.74 ka (Contreras and others, 2012a,c). These dates correspond with dates provided in Easterbrook (1994) for the Whidbey Formation (Easterbrook and others, 1967) less than 10 mi to the northeast of the map area. Pre-Fraser Deposits, Undivided Qc Pre-Double Bluff nonglacial deposits, undivided (cross section only)—Predominantly silty clay, sand, and gravel with minor peat and wood; brown-gray and blue-gray; very dense and hard. The few wells that penetrated this unit encountered sand and silt with organic matter, suggestive of nonglacial strata. Unit Qc is less than 100 ft thick in the area of the cross section. It is stratigraphically below units we map as Double Bluff Drift (Easterbrook and others, 1967). This unit could be as young as the Hamm Creek interglaciation (MIS 7)(Troost and others, 2008) or much older; we have no age control. GEOLOGIC MAP OF THE LOFALL 7.5-MINUTE QUADRANGLE, WASHINGTON 13 Qpd Pre-Fraser glacial drift, undivided—Till and minor sandy pebble to cobble gravel; gray; compact; clasts subangular to subrounded; moderately sorted and stratified to unsorted and unstratified; includes metamorphic and granitic clasts, indicating a northern source. The unit may reflect multiple glacial advances. Unit Qpd is found on the eastern side of Hood Canal between Lofall and Vinland (sec. 28, T27N R1E) where it includes northern-source diamict of unknown age. In the cross section, it is depicted as glacial drift older than Double Bluff Drift. It could be significantly older (Birdseye and Carson, 1989), but we have no age control. This unit closely resembles unit Qgdd mapped in nearby quadrangles (Contreras and others, 2012a,c), but exposures did not allow us to confidently differentiate it from Possession, Double Bluff, or older glacial deposits. Deposits of the Double Bluff Glaciation (MIS 6) Qgdd Double Bluff Drift (cross section only)—Diamicton; gray to blue gray; very dense. The few wells that penetrated this unit encountered diamicton suggestive of significant glacial strata. Unit Qgdd as depicted in the cross section is as much as 100 ft thick. It is found stratigraphically above and below units we map as nonglacial deposits. We infer that this unit is overlain by the Whidbey Formation (unit Qcw) and deposited on nonglacial deposits of unknown age (unit Qc). Unit Qgdd is inferred to have been deposited during MIS 6 but without age control. We tentatively correlate it with the Double Bluff Drift on Whidbey Island (Easterbrook and others, 1967). Tertiary Sedimentary and Volcanic Rocks In 1972, two oil wells were drilled to the east of the map area along a structural uplift termed the Kingston arch (Johnson and others, 1994). The Union Oil Co. Pope and Talbot No. 18-1 well was drilled less than 2 mi east of the map boundary (see Fig. 1 on map sheet) and the Mobil Oil Corporation Kingston No. 1 well was drilled less than 6 mi east. The Pope and Talbot No. 18-1 encountered sedimentary rocks at approximately 1,350 ft below ground surface and the Kingston No. 1 at 1,720 ft. The Kingston No. 1 has been studied more than the Pope and Talbot well, so we rely primarily on information from the Kingston well (Rau and Johnson, 1999) to characterize sedimentary rocks depicted in the cross section. Based on field notes of Howard Gower, Brocher and Ruebel (1998) thought the sedimentary rocks in the Pope and Talbot well were likely Blakeley Formation, but provided few additional details. Rau and Johnson suggested that the upper part of the Blakeley Formation was eroded off the Kingston arch because they did not find evidence for the upper Blakeley Formation in the well, and exposures on Bainbridge Island and seismic interpretations supported this. We were unable to determine from the literature much about the formations encountered in the Pope and Talbot well, so we are unsure if the sedimentary rocks here were also eroded. Hanson (1976) mapped the basalt near Shine as the Crescent Formation. Yount and Gower (1991) mapped bedrock near the Hood Canal Bridge as lower Eocene Crescent Formation and the sedimentary rocks from the Kingston well as “undifferentiated marine and nonmarine sedimentary rocks (upper Eocene and Oligocene), Blakeley Formation and Blakely Harbor Formation”. We relied on Yount and Gower’s work and depict these rocks in the cross section as “undifferentiated marine and nonmarine siltstone” because we had little additional information on these rocks and they are not exposed in the map area. We relied on Hanson and Yount and Gower for the one small exposure of basalt near Shine and mapped it as basalt of the Crescent Formation. …Em Undifferentiated marine and nonmarine siltstone and sandstone (upper Eocene to lower Oligocene) (cross section only)—Marine siltstone and sandstone; light gray to gray and gray-brown. These sedimentary rocks were reported from the Union Oil Co. Pope and Talbot well No. 18-1 drilled in 1972. Evc Crescent Formation (early to middle Eocene)—Basalt; dark gray to greenish black; commonly includes amygdules of zeolite, opaque minerals, and chlorite-group minerals. Unit Evc is found in an isolated outcrop along the shore of Squamish Harbor near Shine and in water wells and borings as far east as the Hood Canal Bridge. Magnetic anomalies, seismicity, and tilted Olympia-age silts suggest that a fault associated with the Kingston arch brings Crescent basalt to the surface here. We tentatively assign this exposure to the Upper Crescent Formation (Cady and others, 1972; Arnold, 1906). 14 MAP SERIES 2013-03 ACKNOWLEDGMENTS This report was funded in part by the U.S. Geological Survey National Cooperative Geologic Mapping Program under award no. G12AC20234. Special thanks to Pope Resources and Zimmer Quarry for access to property. Additional thanks to Randall Vance Conger-Best for his help with petrology, compiling subsurface information, and assisting with write up; Bill Lingley (Leslie Geological Services) and Thomas Pratt (USGS) for help interpreting seismic lines; Elizabeth Nesbitt (Burke Museum, Univ. of Wash.) for identifying marine shells; Estella Leopold (Univ. of Wash.) for identifying and interpreting pollen data; Bob Carson (Whitman College) for sharing his field notes and knowledge of the area and for his help in editing this work; Shannon Mahan (USGS) for luminescence analysis; Ralph Haugerud (USGS) for sharing his knowledge of the area and the deglaciation of the Puget Lowland; Wendy Gerstel (Qwg Applied Geology) for discussions about shoreline processes and landslides; Andy Lamb (Boise State Univ.) for sharing various geophysical data; Rick Blakely (USGS) for magnetic data; Eric Dingeldein and the Wash. Dept. of Transportation for access to geotechnical records; Ana Shafer (Wash. Dept. of Natural Resources) for landslide data. Thanks also to Wash. Div. of Geology and Earth Resources staff Tim Walsh, Joe Dragovich, and Jessica Czajkowski for constructive discussions of the geology and reviewing the map and text; Bryan Garcia, Rian Skov, Coire McCabe, and Carrie Gillum for field and boat help; Recep Cakir for geophysical soundings; Lee Walkling and Stephanie Earls for library support; Eric Schuster and Anne Olson for cartographic expertise; and Jari Roloff, Meredith Payne, and Jessica Czajkowski for editing the map and pamphlet; and Michael Polenz and Gary Petro for sharing their observations, ideas, and perspective on geology in the adjacent quadrangles. We thank countless landowners for sharing local knowledge and permitting us to map on their land. REFERENCES CITED Arnold, Ralph, 1906, Geological reconnaissance of the coast of the Olympic Peninsula, Washington: Geological Society of America Bulletin, v. 17, p. 451-468. Birdseye, R. 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J., 1971, Problems of interpreting radiocarbon dates from dead-ice terrain, with an example from the Puget Lowland of Washington: Quaternary Research, v. 1, no. 3, p. 410-414. Porter, S. C.; Swanson, T. W., 1998, Radiocarbon age constraints on rates of advance and retreat of the Puget lobe of the Cordilleran ice sheet during the last glaciation: Quaternary Research, v. 50, no. 3, p. 205-213. Pratt, T. L.; Johnson, S. Y.; Potter, C. J.; Stephenson, W. J.; Finn, C. A., 1997, Seismic reflection images beneath Puget Sound, western Washington State—The Puget Lowland thrust sheet hypothesis: Journal of Geophysical Research, v. 102, no. B12, p. 27,469-27,489. Rau, W. W.; Johnson, S. Y., 1999, Well stratigraphy and correlations, western Washington and northwestern Oregon: U.S. Geological Survey Geologic Investigations Series Map I-2621, 3 sheets, with 31 p. text. [http://pubs.er.usgs.gov/publication/i2621] 18 MAP SERIES 2013-03 Sarikhan, I. Y.; Stanton, K. D.; Contreras, T. A.; Polenz, Michael; Powell, Jack; Walsh, T. J.; Logan, R. L., 2008, Landslide reconnaissance following the storm event of December 1–3, 2007, in western Washington: Washington Division of Geology and Earth Resources Open File Report 2008-5, 16 p. [http://www.dnr.wa.gov/ResearchScience/Topics/GeologicHazards Mapping/Pages/landslides_dec07storm.aspx] Sceva, J. E., 1957, Geology and ground-water resources of Kitsap County, Washington: U.S. Geological Survey Water-Supply Paper 1413, 178 p., 3 plates. [http://pubs.er.usgs.gov/usgspubs/wsp/wsp1413] Thorson, R. M., 1981, Isostatic effects of the last glaciation in the Puget Lowland, Washington: U.S. Geological Survey OpenFile Report 81-370, 100 p., 1 plate. [http://pubs.er.usgs.gov/publication/ofr81370] Thorson, R. M., 1989, Glacio-isostatic response of the Puget Sound area, Washington: Geological Society of America Bulletin, v. 101, no. 9, p. 1163-1174. Troost, K. G., 1999, The Olympia nonglacial interval in the southcentral Puget Lowland, Washington: University of Washington Master of Science thesis, 123 p. Troost, K. G.; Booth, D. B., 2008, Geology of Seattle and the Seattle area, Washington. In Baum, R. L.; Godt, J. W.; Highland, L. M., editors, Landslides and engineering geology of the Seattle, Washington, area: Geological Society of America Reviews in Engineering Geology XX, p. 1-35. [http://www.wou.edu/las/physci/taylor/g473/seismic_hazards/troost_booth_2008_geo_ seattle.pdf] U.S. Geological Survey Geologic Names Committee, 2010, Divisions of geologic time—Major chronostratigraphic and geochronologic units: U.S. Geological Survey Fact Sheet 2010-3059, 2 p. [http://pubs.usgs.gov/fs/2010/3059/] Waitt, R. B., Jr.; Thorson, R. M., 1983, The Cordilleran ice sheet in Washington, Idaho, and Montana. In Porter, S. C., editor, The late Pleistocene; Volume 1 of Wright, H. E., Jr., editor, Late-Quaternary environments of the United States: University of Minnesota Press, p. 53-70. Washington Department of Ecology, 1978, Coastal zone atlas of Washington; volume 11, Jefferson County: Washington Department of Ecology, 1 v., maps, scale 1:24,000. Washington Department of Ecology, 1979, Coastal zone atlas of Washington; volume 10, Kitsap County: Washington Department of Ecology, 1 v., maps, scale 1:24,000. Yount, J. C.; Gower, H. D., 1991, Bedrock geologic map of the Seattle 30′ by 60′ quadrangle, Washington: U.S. Geological Survey Open-File Report 91-147, 37 p., 4 plates. [http://pubs.er.usgs.gov/publication/ofr91147] Yount, J. C.; Minard, J. P.; Dembroff, G. R., 1993, Geologic map of surficial deposits in the Seattle 30′ x 60′ quadrangle, Washington: U.S. Geological Survey Open-File Report 93-233, 2 sheets, scale 1:100,000. [http://ngmdb.usgs.gov/ Prodesc/proddesc_12654.htm] GEOLOGIC MAP OF THE LOFALL 7.5-MINUTE QUADRANGLE, WASHINGTON 19 Appendix A. Pollen Data Analysis of two pollen samples depicted on the map as significant sites S1and S2. Counted and analyzed by Estella Leopold from the University of Washington. Significant site S1 S2 Sample no. 15-K-211-A 46-K2-622 Latitude and longitude (decimal degrees) 47.865702 –122.643428 47.807797 –122.744730 elevation 9 ft 9 ft Radiocarbon age (conventional radiocarbon age) 37,840 ±380 yr BP 25,850 ±120 yr BP Identified pollen species Abies (fir) X 7 Acer 1 Alnus X 1 Artemisia 1 Asteraceae 2 Betula X charcoal X Chenopodiaceae 2 fern spores X 5 herb pollen Larix 3 Picea X 16 Pines X Pinus 6 Poaceae 2 Populus 2 Pseudotsuga X Selaginella cf densa 7 Tsuga 2 Tsuga heterophylla X Tsuga cf canadensis non-tree pollen 18 Interpretation Mixed conifer forest with climate similar to today or a dry environment based on abundance of pine. Forest perhaps had frequent fires. Mixed conifer forest… maybe a cooler setting (no Pseudotsuga) because this time frame may not have been a true warm period. Lots of non-tree pollen. Surprised at the dry-loving flora. Not necessarily a forest setting. Lots of herbs, fern spores, small plants. Might be open vegetation, somewhat dry. Transitional toward glaciation. Diversity may support prior to full glacial. ger_ms2013-03_geol_map_lofall_24k.pdfMap Series 2013-3. Geologic Map of the Lofall 7.5-minute Quadrangle, Jefferson and Kitsap Counties, Washington ? ? ? ? ??? Qgic Qgo Qgos Qam Qa Qb Qaf Qp Qge QgogQgt Evc ml Qpd Qpf Qls Qmw Qgoaf Qgdd Qpu Qgdp Qcw …Em Qco Qpos UNCONFORMITY EOCENE TERTIARY PLEISTOCENE QUATERNARY HOLOCENE CORRELATION OF MAP UNITS NONGLACIAL UNITS GLACIAL AND NONGLACIAL UNITS, UNDIVIDED GLACIAL UNITS FRASER GLACIATION POSSESSION GLACIATION WHIDBEY INTERGLACIAL DOUBLE BLUFF GLACIATION OLYMPIA NONGLACIAL INTERVAL ? ? BLAKELEY FORMATION(?) CRESCENT FORMATION (?) OLIGOCENE ? ? ? ? ? Qc Table 2. Age-control data for Pleistocene nonglacial sediments. Analytical methods used are 14C, radiocarbon analysis; AMS, radiocarbon analysis by atomic mass spectrometry; and IRSL, infrared stimulated luminescence. Radiocarbon age estimates are presented as ‘conventional radiocarbon age’ with quoted errors representing one relative standard deviation (68% probability). Age estimates stated in ka are in calendar years before 1950 divided by 1,000 with two standard deviations of uncertainty (2σ = 95% confidence interval). Direct AMS samples were calculated using Calib online [http://calib.qub.ac.uk/calib/]. Uncertainty statements reflect random and lab errors; errors from unrecognized sample characteristics or flawed methodological assumptions are unknown. Elevations are estimated using Puget Sound Lidar Consortium lidar grid elevations projected to State Plane South, NAD 83 HARN, supplemented by elevation estimates on bluffs. Age site Site name Analytical method Age estimate (14C yr BP or ka) 13C/12C (o/oo) Material dated Geologic unit Lab no. Elev. (ft) Notes 2 GD2 AMS1 37,840 ±380 yr BP (39.45–40.42 ka) –0.9 shell Qco  Beta 338311 8 Marine shells from silt at base of bluff. Results do not include local reservoir correction. 6 GD6 AMS2 9,924 ±41 yr BP (11.231–11.6 ka) –20.3 charcoal – – –  D-AMS 1549 160 Charcoal in terrace sand. May be recording forest fire. 3 GD3 AMS1 25,850 ±120 yr BP (28.46–28.96 ka) –22.7 wood Qco  Beta 339711 9 Well preserved wood fragments along Thorndyke Bay near GD8. 5 GD5 AMS2 37,139 ±278 yr BP (41.487–42.428 ka) –34.5 charcoal Qco  D-AMS 1749 275 Detrital carbon in well sorted sands mapped as Qco and thought to be the same material as sampled for GD4. 4 GD4 IRSL3 75.12 ±3.7 ka – – – feldspar grains Qco  Lofall-2 275 IRSL sample of feldspar grains from unit Qco.Thought to be taken from same material as GD5. 7 GD7 IRSL3 73.15 ±4.3 ka – – – feldspar grains Qco  Lofall-1 270 IRSL sample of feldspar grains from unit Qco. 8 GD8 IRSL3 47.22 ±9.56 ka – – – feldspar grains Qco  Lofall-3 9 IRSL sample of feldspar grains from unit Qco taken from the same material and near GD3. 1 Analysis by Beta Analytic (Beta) 2 Analysis by DirectAMS (D-AMS) 3 Analysis by Shannon Mahan, USGS Geotechnical Boring Site Type Site Location Site Information B1 WSDOT geotechnical boring sec. 2, T27N R1E 104/1-99 (highway/boring-year) B2 WSDOT geotechnical boring sec. 14, T27N R1E 3/2-99 (highway/boring-year) B3 WSDOT geotechnical boring sec. 10, T26N R1E 3/1-01 (highway/boring-year ) Well Site Type Site Location Site Information W1 water well sec. 34, T28N R1E WADOE internal no. 48488 W2 water well sec. 1, T27N R1W WADOE well tag BAT986 W3 water well sec. 7, T27N R1E WADOE well tag BAT984 W4 water well sec. 12, T27N R1W WADOE well tag BAT985 W5 water well sec. 9, T27N R1E WADOE well tag ACQ536 W6 water well sec. 14, T27N R1E WADOE well tag AES273 W7 water well sec. 23, T27N R1E WADOE well tag ALS596 W8 water well sec. 23, T27N R1E WADOE well tag AES206 W9 water well sec. 23, T27N R1E WADOE well tag AKB784 W10 water well sec. 27, T27N R1E WADOE well tag AAA103 W11 water well sec. 25, T27N R1W WADOE well tag ALS571 W12 water well sec. 34, T27N R1E WADOE well tag AES393 W13 water well sec. 4, T26N R1E WADOE well tag AAA105 W14 water well sec. 4, T26N R1E WADOE internal no. 62283 W15 water well sec. 2, T26N R1E WADOE well tag AAC682 W16 water well sec. 9, T26N R1E WADOE well tag AES019 W17 water well sec. 11, T26N R1E WADOE well tag AES488 W18 water well sec. 8, T26N R1E Navy Base TH3 (Robinson Noble, Inc.) W19 water well sec. 10, T26N R1E WADOE well tag AAA104 W20 water well sec. 17, T26N R1E Navy Base TH10 (Robinson Noble, Inc.) W21 water well sec. 16, T26N R1E WADOE well tag ACG506 Table 1. List of well and geotechnical boring sites for the Lofall quadrangle. WADOE, Washington State Department of Ecology; WSDOT, Washington State Department of Transportation. Possession glaciation (80–60 ka) Fraser glaciation (30–10 ka) Double Bluff glaciation (190–125 ka) Defiance glaciation (280–215 ka) Whidbey interglaciation (125–80 ka) Hamm Creek interglaciation (215–190 ka) Olympia nonglacial interval (60–15 ka) Holocene Pleistocene Subchron Polarity Age (ka) Lowland Climatic Intervals 0 Brunhes Laschamp Blake Biwa I/Jamaica Biwa II/Levantine Biwa III Emperor Big Lost Delta Central Puget Lowland Stratigraphic Column Unidentified glacial and interglacial intervals Matuyama 5 7 9 11 13 15 17 19 21 100 200 300 400 500 600 700 800 Sumas stade (11.5–10 ka) Everson interstade (13–11.5 ka) Vashon stade (15–13 ka) Lawton Clay Esperance Sand (advance outwash) Vashon Till Port Moody interstade (23–21 ka) Coquitlam stade (BC) (30–25 ka) MiddleLate ReversedNormalPolarity: MISO(‰)18δ -3-2-1 0 Figure 2. Comparison of geologic time scale, global magnetic polarity, marine oxygen isotope curve and stages (MIS), and ages of climatic intervals in the Puget and Fraser Lowlands [modified from fig. 6 of Troost and Booth, 2008]. Data sources are explained in Troost and Booth (2008). Age ranges for the Olympia nonglacial interval, Vashon stade, and Everson interstade were modified by Polenz and others, 2013 and 2012b. We note that the exact time boundaries between the Olympia nonglacial interval, Vashon stade, and the Everson interstade in the Puget Lowland remain enigmatic. D A B O B BAY FA U L T ZON E HOOD CANAL HOOD CANAL Pope & Talbot no. 18-1 well Kingston no. 1 well Pope & Talbot no. 18-1 well Kingston no. 1 well LOFALL FAULT ZONE SEATTLE FAULT ZONE DABOB BAY FAULT ZONE KINGSTON ARCH PORT LUDLOW UPLIFT SOUTHERN WHIDBEY ISLAND FAULT ZONE Holly Bremerton Bainbridge IslandSilverdale Poulsbo Hansville Quilcene Breidablick Kingston Eglon Dyes Inlet Liberty Bay Port Madison Port Madison PUGET SOUND SEATTLE BASIN SEATTLE UPLIFT SEATTLE UPLIFT Seabeck Brinnon Dabob Bay CANAL D i s c o v e r y B a y VI NL A N D SY NCLINE LOFALL QUADRANGLE HOOD FAULT? Winslow Port Gamble Port Ludlow Bangor Port Orchard Figure 1. Shaded relief map of the Lofall quadrangle (red polygon) region. Faults in and adjacent to the quadrangle are shown as indicated by current field investigations (Contreras and others, 2013; Polenz and others, 2013), while regional faults were redrawn from previous investigations (Lamb and others, 2012; Blakely and others, 2009; active faults layer of the Washington Interactive Geologic Map, accessed May 2013 on the Washington State Geologic Information Portal at http://www.dnr.wa.gov/geologyportal). Geophysical studies (Pratt and others, 1997) provided the information on uplifts and basins outlined by green dashed lines. 0 4 2 mi Qpu Qpd Qpd Qc Qgdd Qgdd Qgdd Qcw Qcw Qcw Qgdp Qgdp Qgdp Qgo Qco Qco Qco Qco Qgt …Em Qc Qc Qgic Qgic Qgic Qa QgoQgo Qgo Qgoaf Qgos Qp ml Qgos Beach Drive NE Rhododendron Lane NW Wagorn Road NW Rhododendron Lane NW Clear Creek Road NE Lofall Road NW Finn Hill Road Rhododendron Lane NW Pioneer Way NW NW Pioneer Hill Road NW Rude Road 500 -1500 -1000 -500 0 -1000 -500 0 -1500 500 W21 W7 W9 W10 W12 W19 W16 A′A NORTHSOUTH Elevation (feet) 4x vertical exaggeration Elevation (feet) Qp Hood Canal creek Kingston arch Vinland syncline W10 Water well or boring Geologic unit in cross section too thin to show at scale. Black tick marks separate units. Geologic Symbols in Cross Section D U D U D U D U ?? ? ? ? ? ? ? GD2 GD6 GD4 GD7 GD3 GD5 GD1 GD8 8 3 11 2 4 12 3 11 18 13 7 20 5 7 W21 W10 S2 W13 W9 W1 B3 W17 W8 S3 W5 W11 W15 W2 W6 W3 W7 W4 W12 S1 W20 W19 W18 W14 B1 W16 B2 Qgdp Qgdp Qgdp Qgdp Qa Qa Qa Qa Qa Qa Qa Qa Qa Qa Evc Qam Qam Qam Qam Qaf Qaf Qaf Qb Qb Qb Qb Qb Qb Qb Qb Qb Qco Qco Qco Qco Qco Qco Qco Qco Qco Qco Qco Qco Qco Qco Qco Qco Qco Qco Qco Qco Qco Qco Qco Qco Qco Qco Qco Qco Qco Qco Qco Qco Qco QcoQc w Qcw Qcw Qcw Qcw Qcw Qc Qcw Qgdp Qgdp Qgdp Qgdp Qgdp Qgdp Qgdp Qgdp Qgdp Qgdp Qgdp Qgdp Qgdp Qgdp Qgdp Qgdp Qgdp Qgdp QgdpQgd p Qge Qge Qge Qge Qgic QgicQgic Qgic Qgic Qgic Qgic Qgic Qgic Qgic Qgic Qgic Qgic Qgic Qgic Qgic Qgic Qgic Qgic Qgic Qgic Qgic Qgic Qgic Qgic Qgic Qgic Qgic QgicQgic Qgic Qgic Qgic Qgic Qgic Qgic Qgic QgicQgic Qgic Qgoaf Qgoaf Qgoaf Qgoaf Qgoaf Qgoaf Qgoaf Qgoaf Qgoaf Qgoaf Qgoaf Qgoaf Qgoaf Qgog Qgog Qgog Qgog Qgog Qgog Qgog Qgog Qgos Qgos Qgos Qgos Qgoaf Qgoaf Qgos Qgos Qgos Qgos Qgt Qgt Qgt Qgt Qgt Qgt Qgt Qls Qls Qls Qgdp Qgdp Qls Qls Qls Qls Qls Qls Qls Qls Qls Qls Qls Qls Qls Qmw Qmw Qmw Qmw Qp Qp Qp Qp Qp Qp Qp Qp Qp Qp Qp Qp Qp Qp Qp Qp Qp Qpd Qpf Qpf Qpos Qpos Qpos?Q pu QpuQpu Qmw ml ml ml ml ml Qgo Qgo Qgo Qgo Qgo Qgo Qgo Qgo Qgo Qgo Qgo Qgo Qgo Qgo Qgo Qgo Qgo Qgo Qgo Qgo Qgo Qgo Qgo Qgo Qgo Qgo Qgo Qgo Qgo Qgo Qgo Qgo Qgo Qgo Qgo Qgo Qgo Qgo Qcw Qcw Qls Qb Qco Qco Qgic Qgic Qco Qb Qco Qa Qgo Qgo Qco Qa Qgt Qcw Qa Qgdp Qgdp Qgic Qgic Qpd Qco Qgic KINGSTON ARCH A A′ Bangor Naval Base se ismic line 93 s e ism ic line 75 s e i s m i c line 98 l i n e 97 seism ic seis m i c li n e 98 s ei smic 95 se is m i c li n e 76 seism ic lin e 94 l i n e Hood Canal Bridge 122°37′30″ 47°52′30″ 122°45′ 47°52′30″ R 1 W R 1 E T 28 N T 27 N 47′30″ 47′30″ 40′ 40′ 50′ 122°37′30″ 47°45′ 120°45′ 47°45′ 42′30″ 50′ 42′30″R 1 W R 1 E T 28 N T 27 N T 28 N T 27 N T 28 N T 27 N 104 19 3 307 305 QUILCENE LOFALL SEABECK POULSBO CENTER PORT LUDLOW HANSVILLE PORT GAMBLE SUQUAMISH KITSAP CO. ISLAND CO. Seabeck Bangor Poulsbo Suquamish Port Gamble Hansville Port Ludlow JEFFERSON CO. Quilcene Lofall Silverdale 7000 FEET1000 10000 2000 3000 4000 5000 6000 0.5 1 KILOMETER1 0 0.51 0 1 MILE SCALE 1:24,000 Geologic Map of the Lofall 7.5-minute Quadrangle, Jefferson and Kitsap Counties, Washington by Trevor A. Contreras, Kimberly A. Stone, and Gabriel Legorreta Paulin October 2013 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 or for the State of Washington, Department of Natural Resources, Division of Geology and Earth Resources. © 2013 Washington Division of Geology and Earth Resources depth contours in feet—datum is mean lower low water 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 Lofall 7.5-minute quadrangle, 1973 Shaded relief generated from a lidar bare-earth digital elevation model (available from Puget Sound Lidar Consortium, http://pugetsoundlidar.ess.washington.edu/); sun azimuth 310°; sun angle 50°; vertical exaggeration 1x GIS by Trevor A. Contreras and Kimberly A. Stone Digital cartography and GIS by Ian J. Hubert, Anne C. Olson, and J. Eric Schuster Editing and production by Jaretta M. Roloff and Jessica L. Czajkowski 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, 2013 MAGNETIC NORTH TRUE NORTH 16.5° WASHINGTON DIVISION OF GEOLOGY AND EARTH RESOURCES MAP SERIES 2013-03 Lofall 7.5-minute Quadrangle October 2013 Pamphlet accompanies map http://www.dnr.wa.gov/geology/ Research supported by the U.S. Geological Survey, National Cooperative Geologic Mapping Program, under USGS award number G12AC20234. The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the U.S. Government. VINLAND SYNCLINE MAJOR FINDINGS • Radiocarbon and luminescence age estimates suggest that deposits of the Olympia nonglacial interval dominate the stratigraphy in the area and include sand from the central Cascade Range. • Extensive sand deposits from the Olympia nonglacial interval are the source of material for nearshore habitat in this part of Hood Canal, in contrast to the material available in the southern Hood Canal. • Movement along the Lofall fault may have lifted deposits of the Olympia nonglacial interval near the Hood Canal Bridge. This tilting contributes to bluff failure in the vicinity. DESCRIPTION OF MAP UNITS (See pamphlet for complete descriptions of map units) Quaternary Unconsolidated Deposits HOLOCENE NONGLACIAL DEPOSITS ml Modified land—Clay to boulder gravel and diamicton; locally derived but mixed and reworked by excavation and (or) redistribution that notably modifies topography. Qa Alluvium—Sand to cobble gravel; loose; gray, generally unweathered; clasts subrounded; moderately to well sorted. Qb Beach deposits—Sand to boulder gravel with shells and driftwood; loose; gray to brown-gray; clasts moderately to well rounded; may be well sorted; derived from shore bluffs, streams, and underlying deposits. Qam Relict alluvium and salt-marsh deposits—Silty sand, silt, and pebble to cobble gravel, locally includes silt, clay, peat, and detrital wood; loose; typically tan and generally unweathered; clasts subrounded; moderately to well sorted; stratified to massively bedded. This unit is less than 6,000 years old. HOLOCENE TO LATEST PLEISTOCENE NONGLACIAL DEPOSITS Qp Peat—Organic-rich sediment, including silt and clay; very soft to medium soft; dark-brown to black; typically in closed depressions. Qls Landslide deposits—Diamicton; loose or soft; clasts subangular to subrounded; unsorted to moderately sorted; nonstratified. Not all landslides are shown, and absence of a mapped slide does not imply absence of hazard. Qmw Mass-wasting deposits—Diamicton; loose; clasts subrounded; unsorted to poorly sorted; includes colluvium, debris fans, alluvial fans, and landslides mapped where topography suggests mass-wasting deposits. Qaf Alluvial fan deposits—Debris-flow diamicton and alluvial sand and gravel; loose; gray; clasts subrounded to rounded; forms concentric lobes where streams emerge from confining valleys. PLEISTOCENE GLACIAL AND NONGLACIAL DEPOSITS Vashon Stade of the Fraser Glaciation (MIS 2) Recessional deposits Qgo Vashon recessional outwash—Sand and cobble to pebble gravel; loose; gray, weathering to tan; clasts subangular to rounded; moderately to well sorted; represents fluvial deposition by Vashon meltwater. Locally divided into: Qgoaf Vashon alluvial fan deposits—Sand and pebble gravel, silt, and cobbles; loose; subrounded; moderately to poorly sorted; stratified; forms concentric lobes where outwash streams emerged from confining valleys. Qgog Vashon recessional outwash gravel—Pebble and cobble gravel and sand; gray to tan, unweathered; loose; clasts moderately to well rounded; moderately to well sorted; mapped in outwash channels graded to recessional Lake Bretz. Qgos Vashon recessional outwash sand—Sand; gray to tan; loose; clasts moderately to well rounded; moderately to well sorted; mapped in outwash channels graded to recessional Lake Bretz. Qgic Vashon ice-contact deposits—Diamicton, cobbly pebble gravel, and subglacial melt-out till; yellow-tan to gray; loose to dense; clasts subangular to subrounded; variously sorted; massive to well stratified; till is friable and permeable. Locally divided into: Qge Vashon esker deposits—Gravel and sand; tan to brown; loose; clasts moderately to well rounded; well-sorted; forms low, elongate, sinuous hills. Subglacial deposits of the Fraser glaciation Qgt Vashon lodgment till—Mixture of clay, sand, and gravel (diamicton); gray; compact; clasts subangular to rounded; unsorted and unstratified. Pre-Fraser Glacial and Nonglacial Deposits Pre-Vashon glacial and nonglacial deposits Qpf Pre-Vashon silt—Silt, clay, and some sand and pebble gravel; brown or gray; compact; unstratified to well stratified; generally thought to be glaciolacustrine, but may include nonglacial deposits. Qpos Pre-Vashon northern-sourced glacial outwash sand—Sand, silt, clay, and pebble gravel; brown or gray; compact; unstratified to well stratified. Qpu Undivided Quaternary sediment older than Vashon till—Sandy pebble gravel and sand with mud interbeds; gray, with surficial iron staining and some light-brown mud beds; compact. Deposits of the Olympia nonglacial interval (MIS 3) Qco Olympia nonglacial deposits—Sand and silt; tan and gray; medium dense to loose; clasts subangular to subrounded; laminated to very thickly bedded or massive and well stratified and sorted; locally crossbedded and with ripplemarks. Represents distal Olympic and Cascade alpine outwash deposited in a floodplain or lacustrine environment, when the Puget Lowland was ice free. Deposits of the Possession glaciation (MIS 4) Qgdp Possession Drift—Diamicton and outwash; light brown to gray; very dense and massive; clasts subrounded to rounded; moderately to well sorted and unsorted; moderately stratified and medium to thickly bedded. Deposits of the Whidbey interglaciation (MIS 5) Qcw Whidbey Formation—Silt, clay, and sand; light gray; dense and stiff; clasts subrounded; well stratified and well sorted; thinly laminated to very thickly bedded. Represents calm-water deposition during nonglacial times. Pre-Fraser deposits, undivided Pre-Fraser nonglacial deposits—Predominantly silty clay, sand, and gravel; brown-gray and blue-gray; very dense and hard. The few wells that penetrated this unit encountered sand and silt with organics, suggestive of nonglacial strata. Qpd Pre-Fraser glacial drift—Till and minor sandy pebble to cobble gravel; gray; compact; clasts subangular to subrounded; moderately sorted and stratified to unsorted and unstratified. The unit may reflect multiple glacial advances. Deposits of the Double Bluff glaciation (MIS 6) Qgdd Double Bluff Drift (cross section only)—Diamicton; gray to blue gray; very dense. The few wells that penetrated this unit encountered diamicton suggestive of significant glacial strata. Tertiary Sedimentary and Volcanic Rocks …Em Undifferentiated marine and nonmarine siltstone and sandstone (upper Eocene to lower Oligocene)(cross section only)—Marine siltstone and sandstone; light gray to gray and gray-brown. These sedimentary rocks were reported from the Union Oil Co. Pope and Talbot well No. 18-1 drilled in 1972. Evc Crescent Formation (early to middle Eocene)—Basalt; dark gray to greenish black; Unit Evc is found in an isolated outcrop along the shore of Squamish Harbor near Shine and in water wells and borings as far east as the Hood Canal Bridge. GEOLOGIC SYMBOLS Contact—Identity and existence certain; solid where location accurate; long dashed where approximate; short dashed where inferred High-angle dip-slip fault—Identity or existence questionable, location concealed; relative movement shown by U and D Anticline—Identity or existence questionable; location concealed Syncline—Identity and existence questionable; short dashed where location inferred; dotted where concealed Lineament—Identity and existence certain; location accurate Cross section line Strand line (former shoreline)—Identity and existence certain; location accurate Geophysical data collection line—Location accurate Landslide scarp—Hachures on downslope side Bedding in unconsolidated sedimentary deposits—Showing strike and dip Foreset bedding in unconsolidated sedimentary deposits—Showing strike and dip Horizontal bedding Age sample, radiocarbon (14C) Age sample, infrared stimulated luminescence (IRSL) Water well or geotechnical boring Significant site Geologic unit too small to show as a polygon at map scale D U ? A′A 14 29 W3 S1 GD7 GD2 ?? Qgdp 55 35 20 0 15 6 42 0 40 15 100 0 4 10 0 0 7 20 0 0 0 7 60 0 10 0 100 0 5 10 20 5 30 30 0 5 30 30 30 0 25 10 70 0 35 50 40 0 25 25 0 5 20 30 100 0 0 0 35 0 0 10 100 0 7 15 75 0 18 18 0 0 0 50 50 0 10 15 10 0 15 5 5 5 0 10 0 5 10 5 5 0 5 7 7 0 5 5 20 0 0 30 70 5 …Em Qco Qc Qgog Qgos Evc Qa Qaf Qpf Qcw Qgdd Qgdp Qge Qgic Qgo Qgt Qls Qmw Qp Qpd ml Qpos Qam Qb Qgoaf Qpu