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GEOLOGIC FIELD REPORT
ESS 510: Field Methods in Applied Geology II
Sunday the 15th
to Monday the 23rd
of June 2014
Masters...
Kathy Troost, Senior Lecturer and Professor
Eric Knoedler, Teacher Assistant
Contributors (in alphabetical order): Robert ...
TABLE OF CONTENTS
i
1.0 INTRODUCTION ……………………………………………………………… 1
1.1 Course Mechanics (Cannata, Conrado)
1.2 Site Descripti...
TABLE OF CONTENTS
ii
Geomorphology (Cannata, Wilson, Twomey)
Provenance (Pivaroff-Ward)
4.3 Brown Property (Cannata, Wilso...
ESS 510 INTRODUCTION Robert Cannata
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ESS 510 METHODS Robert Cannata
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ESS 510 GEOLOGIC, GEOMORPHIC AND TECTONIC SETTINGS Robert Cannata
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ESS 510 GEOLOGIC, GEOMORPHIC AND TECTONIC SETTINGS Robert Cannata
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ESS 510 GEOLOGIC, GEOMORPHIC AND TECTONIC SETTINGS Robert Cannata
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ESS 510 GEOLOGIC, GEOMORPHIC AND TECTONIC SETTINGS Robert Cannata
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ESS 510 GEOLOGIC, GEOMORPHIC AND TECTONIC SETTINGS Robert Cannata
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ESS 510 GEOLOGIC, GEOMORPHIC AND TECTONIC SETTINGS Robert Cannata
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ESS 510 FINDINGS: VASHON ISLAND Robert Cannata
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ESS 510 FINDINGS: VASHON ISLAND Robert Cannata
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ESS 510 FINDINGS: NORTHEAST OLYMPIC PENINSULA Robert Cannata
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ESS 510 FINDINGS: NORTHEAST OLYMPIC PENINSULA Robert Cannata
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ESS 510 FINDINGS: NORTHEAST OLYMPIC PENINSULA Robert Cannata
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ESS 510 FINDINGS: NORTHEAST OLYMPIC PENINSULA Robert Cannata
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ESS 510 FINDINGS: NORTHEAST OLYMPIC PENINSULA Robert Cannata
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ESS 510 FINDINGS: NORTHEAST OLYMPIC PENINSULA Robert Cannata
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ESS 510 DISCUSSIONS AND CONCLUSIONS Robert Cannata
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ESS 510 REFERENCES Robert Cannata
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ESS 510 TAKE HOME MESSAGES Robert Cannata
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ESS 510 APPENDIX A – FIELD NOTES Robert Cannata
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Field Geology Report_R

  1. 1. GEOLOGIC FIELD REPORT ESS 510: Field Methods in Applied Geology II Sunday the 15th to Monday the 23rd of June 2014 Masters in Earth and Space Sciences Applied Geosciences (MESSAGe) Program University of Washington, Seattle Campus 2nd Generation 2013 to 2014
  2. 2. Kathy Troost, Senior Lecturer and Professor Eric Knoedler, Teacher Assistant Contributors (in alphabetical order): Robert Cannata, Rebekah Cesmat, Evelyn Conrado, Evan Eckles, Jesse Favia, Grayson Fish, Katie Gauglitz, Andrew Gault, Bryan Holmes, John Manke, Hannah Marshburn, Kendra Pivaroff-Ward, Andrew Spickert, Kristina Sumner, Jeff Tinklepaugh, Niall Twomey, Bart Weitering and Farin Wilson.
  3. 3. TABLE OF CONTENTS i 1.0 INTRODUCTION ……………………………………………………………… 1 1.1 Course Mechanics (Cannata, Conrado) 1.2 Site Descriptions Van Os Feeder Bluff and Beach (Cannata) Sandford Point Fault Area (Cannata) Brown Property (Cannata, Favia) Discovery Bay Tidal Flats (Cannata, Conrado) Dungeness Bluff and Beach West (Cannata, Conrado) Sequim Bay State Park (Cannata, Conrado) 2.0 METHODS ……………………………………………………………………… 7 2.1 Optically Stimulated Luminescence (Gauglitz) 2.2 Radiocarbon Dating (Gauglitz) 2.3 Drilling and Coring (Favia, Gauglitz) 2.4 Discontinuity Mapping (Favia) 2.5 Provenance Determination (Favia, Spickert) Differentiating Glacial from Non-Glacial Deposits 2.6 Soil Classification (Favia) 2.7 Test Pit Observations (Favia) 2.8 Global Positioning System (Weitering) 3.0 GEOLOGIC, GEOMORPHIC AND TECTONIC SETTING ……………… 22 3.1 Vashon and Maury Islands Area (Gault) 3.2 Sequim Area (Holmes) 4.0 FINDINGS: VASHON AND MAURY ISLANDS …………………………… 28 4.1 Van Os Feeder Bluff (Favia) 4.2 Sandford Point Structure (Cesmat) Seepage (Spickert)
  4. 4. TABLE OF CONTENTS ii Geomorphology (Cannata, Wilson, Twomey) Provenance (Pivaroff-Ward) 4.3 Brown Property (Cannata, Wilson) 5.0 FINDINGS: NORTHEAST OLYMPIC PENINSULA ………………………… 44 5.1 Discovery Bay (Gault, Manke) 5.2 Dungeness Bluff West (Conrado, Fish) 5.3 Sequim Bay State Park (Conrado, Fish) 6.0 DISCUSSIONS AND CONCLUSIONS ……………………………………… 52 6.1 Bluff Retreat Comparison (Cannata) 6.2 Sediment Transport Comparison (Cannata) 6.3 Provenance Comparison (Cannata) 6.4 Sandford Point Housing (Cannata) 6.5 Sandford Point Tectonics (Cannata) 6.6 Tsunami Sands at Discovery Bay (Cannata) 7.0 REFERENCES ………………………………………………………………… 64 8.0 TAKE HOME MESSAGES …………………………………………………… 67 APPENDIX A: Logbook Field Notes ………………………………………………… 68 APPENDIX B: Data Sheets …………………………………………………………… 91 Pebble Counts (Sumner) Discovery Bay Core Logs (Cannata, Favia, Gault, Manke) Brown Property Core Log (Cannata,Cesmat, Tinkleplaugh, Weitering,Wilson) APPENDIX C: Field Course Critique ………………………………………………… 117
  5. 5. ESS 510 INTRODUCTION Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 1 of 118 1.0 INTRODUCTION 1.1 Course Mechanics Field Methods in Applied Geology II was an intensive, nine-day field course that commenced Sunday the 15th and concluded Monday the 23rd of June 2014. It was held in two coastal settings within the Puget Sound Lowlands and on the Strait of Juan de Fuca. The first location, Camp Sealth on Vashon Island, served as base camp from June 15th through June 19th . The second location, Ramblewood Environmental Learning Center (ELC) in Sequim Bay State Park, was our base camp from June 19th through June 23rd . We used the University of Washington fleet service vehicles to relocate between these sites and for daily transportation from base camp to field localities. We conducted our daily activities first as a single large group, and then broke off into smaller groups of four to six people and sometimes as pairs depending on the scope of responsibilities and constraints of the locality. This course introduced advanced field techniques and skills for problem solving in applied geology with an emphasis on the interactions between humanity (land use and infrastructure) and the natural landscape of the Pacific Northwest. The main course objectives centered on coastal and hillslope geomorphology and included the following: 1) To map coastal deposits (beach and bluffs), and measure sections of coastal exposures by establishing survey monitoring points; 2) To understand the distribution of coastal deposits, and prepare beach and bluff profiles; 3) To map hillslope morphology and landslide features, and practice recognizing and distinguishing landforms and deposits of both glacial and interglacial periods; 4) To prepare samples for geochronological analyses, conduct our own interpretive provenance analyses, and describe unconsolidated materials using the Unified Soils Classification System (USCS); and 5) To measure geologic materials’ textures, fabrics and discontinuities, and conduct particle size and cobble count analyses.
  6. 6. ESS 510 INTRODUCTION Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 2 of 118 We used a variety of tools and equipment (described in section 2. Methods) to attain these objectives, and ultimately produced a collaborative report describing our field observations and measurements, from which we interpreted and used to base our conclusions.
  7. 7. ESS 510 INTRODUCTION Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 3 of 118 1.2 Summary Description of Sites Visited Van Os Feeder Bluff and Beach, Maury Island FIGURE 1. View of Van Os bluff looking west (Cannata). We arrived early Monday morning (07/16) at the Kimble property, 23010 60th Place SW, Vashon, WA 98070, with a guest investigator Eric Cheney (UW) to access the Van Os coastal bluffs 0.5 km east along the shore (47°23’59.668” N and 122°24’07.910” W). After arriving at the locality, we broke up into smaller groups of four, and assessed 4 sections marked by Kathy Troost and Eric Knoedler along an approximately 1000-foot stretch of the bluff-beach system. Our task was to establish baseline measuring points for long-term monitoring of the bluff-beach system with focus on the erosion potential from bluff retreat and its impact to marine sediment transport within the littoral drift cell operating on this locality. To accomplish this task, we endeavored to 1) measure and characterize the topographic, geologic, structural, and geomorphic nature of the bluff-beach system, 2) sample geologic units for provenance analysis, 3) conduct Wolman cobble counts of the beach for grain-size analysis, and 4) map the spatial distribution of beach sediment to assess littoral transport regime. We also conducted Optically Stimulated Luminescence (OSL) sampling.
  8. 8. ESS 510 INTRODUCTION Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 4 of 118 Sandford Point Fault Area, Vashon Island FIGURE 2. View of Sandford Point beach and bluff system looking south down Colvos Passage (Cannata). We studied the Sandford Point locality on two separate occasions, all day Tuesday (07/17) and half of Wednesday (07/18) as a result on constraints from tidal change and responsibilities to other tasks at the Brown Property. We arrived early morning on Tuesday at the access point (dead end of 146th Ave SW) with guest investigator Eric Cheney (UW) first to conduct a reconnaissance walk as an entire group of approximately 0.75 km of shoreline and coastal bluff exposures N-NE of the access way. Afterward, we strategized as an entire group and divided into 4 smaller groups, each with a concentration on one specific sub-discipline of geology: water seepage (hydrology), structural geology, geomorphology and landslide failures, and geologic materials.
  9. 9. ESS 510 INTRODUCTION Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 5 of 118 Brown Property, Vashon Island Early Wednesday morning (07/18), we arrived at Mike Brown’s residence (21704 141st Ave SW, Vashon, WA 98070) to conduct a subsurface exploration in order to investigate the groundwater changes post-Nisqually earthquake (2001) and hazards associated with westward slope failure. We used the following techniques: hand augering, manual split spoon sampling, and logging a test pit excavated by the property owner. The Brown Property is a 5-acre parcel set back on a plat approximately 300 feet from the crest of a coastal bluff system that faces west and overlooks Colvos Passage. This vegetated bluff system rises an average of 70 m above sea level and slopes steeply west to a beach of mixed sand and gravel. The topography of the property is locally hummocky but broadly flat in its upper east half (around the residential structures), and is cut by a steep-sided valley in the southwest. Discovery Bay, Sequim We arrived early Friday morning (07/20) at the tidal flats of Discovery Bay to meet Carrie Garrison-Laney (UW) and other guest investigators, Liz Nezbit (UW), Ian Miller (WA SeaGrant) and Ron Tagnazaki, to explore the subsurface marsh deposits. After observing a section of sediment along the stream south of the footbridge as a group, we split into teams of six members, each with tools for making measurements and observations of the sample cores. The goals of each team were to identify evidence of tsunami sands, look for any in-place organic material, and to record long core logs well.
  10. 10. ESS 510 INTRODUCTION Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 6 of 118 Dungeness Spit, Sequim FIGURE 3. View of Dungeness Spit looking southwest along the coast (Cannata). We arrived early Saturday morning (07/21) at the Dungeness National Wildlife Refuge to meet Jim Miller (GeoEngineers) to survey and map the coastal deposits of the Dungeness feeder bluffs south of the Spit. The group hiked down to the beach, and spent about one hour on a reconnaissance walk along the bluffs, observing general features and select sites for two transects. Half of our group worked on Transect 1, while the other half worked on Transect 2. Niall Twomey and Robert Cannata did not work on either transect, but employed survey techniques using auto level instrumentation to survey a topographic profile from an anthropogenic benchmark and tie-in Transects 1 and 2 to a stable frame of reference. The main goal was to develop a cross-shore transect measuring the topography and mapping the geology from the shore face to the crest of the bluff.
  11. 11. ESS 510 INTRODUCTION Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 7 of 118 Sequim Bay, Sequim FIGURE 4. View of Sequim State Park beach and bluff system looking west (Cannata). We arrived early Sunday morning (07/22) at Sequim Bay State Park to meet Jim Miller (GeoEngineers) and map exposed bedrock along the bay coast in the context of implications for geotechnical domains. We accessed the bay area by a path from base camp at the Ramblewood ELC. Once we arrived on the beach, we walked east along the beach to observe the nature, structure, geology and vegetation of the bluffs. We divided into teams of two and worked on bluff sections approximately 100 feet long. Teams sketched their section of the bluff, focusing on geologic contacts in context of discontinuities, strength and competency, and other geotechnical properties. We compiled a final sketch to display each team’s section in a continuous profile.
  12. 12. ESS 510 METHODS Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 7 of 118 2.0 METHODS 2.1 Optically Stimulated Luminescence (OSL) Optically stimulated luminescence (OSL) measures doses of ionizing radiation, which serves as a proxy for sediment age. We collected a sample from the Van Os Feeder Bluff on Maury Island to practice proper sampling techniques. While collecting the OSL sample, first cover the sample area with black fabric. We used a black plastic tarp held up by nails to cover the sampling area (Figure 5). Staying underneath the cloth and out of the light, we dug into the desired sample area about 1 foot from the initial exposure. This removes the material that has been exposed to the sun and therefore would underestimate its age. It is very important not to let any light to penetrate the covered area underneath the cloth! Figure 5. We carefully set the staging area for secluded clandestine OSL sampling (Cannata). Marshburn and Gauglitz appear to be ecstatic about OSL sampling, while Grayson is lost in what appears to be deep contemplation. We used a cylindrical sampler to collect a sample and keep it as still as possible. We attached the black cap to one side of the sample cylinder and placed the sharp edge of the sampler on the sample surface. Using a hammer, we pounded the sampling cylinder about 1 foot into the target. When there was about 3 inches of the cylinder still exposed, we scraped out the sand that was not
  13. 13. ESS 510 METHODS Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 8 of 118 in place to use as a control for dating. After scraping, we pounded the cylinder the rest of the way in. Next, whilst remaining underneath the black cloth, we dug around the cylinder to remove the material around it and removed the sampling cylinder from the sediment. While still under the black cloth, we placed a cap on the sharp side of the cylinder and covered the entire sample and cylinder in aluminum foil. Once the foil completely covered the sample, we removed it from underneath the black cloth, placed it in a plastic bag, labeled it, and transported it for analysis. 2.2 Radiocarbon Dating Figure 6. Radiocarbon dating demonstrated by Troost below the base of a Dungeness bluff (Cannata). Radiocarbon dating is another method for dating geologic materials. To sample for radiocarbon dating, one must first find an organic-rich material. Choose a sample that is in place or that seems representative of a deposit. If there is low carbon content in the sample, collect a lot of material. One can pick the carbonaceous components of the material out of the bulk sample in order to obtain the requisite amount of carbon for radiocarbon dating. Using a hammer or other scraping device, obtain chunks of the organic material from the deposit (Figure 6). Radiocarbon dating is very susceptible to carbon contamination from younger carbon sources, so it is
  14. 14. ESS 510 METHODS Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 9 of 118 important to clean the surface of the sample with a knife or similar implement while being careful not to introduce new sources of contamination. We found clasts of organic rich sediment sitting in gravel at both the Van Os Feeder Bluff and Dungeness Spit and sampled organics from both locations. After cleaning the samples’ surfaces with a knife, we placed the samples in a plastic bag and labeled them appropriately. We refrigerated samples to prevent any new organic growth which could occur due to the anoxic environment of the sealed plastic bag. Labs analyze the samples for us using standard radiometric or accelerated mass spectrometry (AMS) techniques. AMS provides a date with a much smaller margin of error; however, it’s also more expensive. When a lab completes sample analysis, the sample will have three ages associated with it: radiometric, corrected, and calibrated. Samples only yield a calibrated age if they are less than 25,000 years old. The calibrated date corrects for 13C / 14C in the atmosphere at the time the material was deposited (which are based on dendrochronologic data). The convention for reporting an age for a sample is: calibrated age +/- error. 2.3 Drilling Mechanical Drilling We observed 3 drilling technologies: direct-push, hollow-stem auger, and sonic drilling, all of which were gracefully demonstrated by Cascade Drilling, Inc. at their Woodinville office (Figure 7). The direct-push GeoProbe drill uses repeated percussive force to advance the drill rod into the ground (Figure 8). In the Pacific Northwest, a typical refusal is achieved between 50 to 100 feet BGS (Cascade Drilling). However, the record for maximum refusal reported in the Fall 2011 Probing Times by GeoProbe Systems is 320.5 feet BGS held by former colleagues of Robert Cannata, Kurt Lyons and Kasey Hedglin at the Otis Air National Guard Base on Cape Cod. They employed a 6620DT rig, drilling into glacial outwash comprising mainly fine sand and silts. This type of drill better suited for drilling through unconsolidated finer-grained soils, like sands and silts, as compared to gravels and cobbles. Direct push drilling can produce a continuous core sample, but it usually displaces and homogenizes the soil sample upon collection. It is ideal for environmental sampling because it can yield discrete groundwater and soil samples and allows installation of small-diameter monitoring wells and piezometers.
  15. 15. ESS 510 METHODS Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 10 of 118 Figure 7. The 3 drilling rigs set up in the Cascade Drilling yard, Woodinville (Cannata). Figure 8. GeoProbe Direct-Push drilling technology (Cannata).
  16. 16. ESS 510 METHODS Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 11 of 118 The second drilling technology was hollow stem augering (Figure 9). This CME 75 model drill uses a diesel engine. An operator spins the auger, causing soil to come up into the center of the rod where he/she collects the sample. The sample will be disturbed. This type of drill can also be used to install a well. The third and largest drill we observed is called a sonic drill (Figure 10). This drill uses mechanical migration, down pressure, and slight rotation to push an auger into the ground. The augers on this drill range from 6 to 12 inches in diameter. The drill can core to a depth of 670 feet and can drill through all materials, including bedrock. Figure 9. Hollow-stem auger drilling technology (Cannata).
  17. 17. ESS 510 METHODS Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 12 of 118 Figure 10. Sonic drilling technology (Cannata).
  18. 18. ESS 510 METHODS Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 13 of 118 Standard Hand Auger Hand auger drilling provides relatively inexpensive and quick information about the shallow subsurface. One individual can transport and operate hand auger equipment with no power required. It is ideal where fiscal, physical, or other restrictions may inhibit mechanical drilling (Figure 11). The necessary materials are: drill log forms, an auger bit, auger rods (enough for desired depth), an auger handle, 2 pipe wrenches, 2 standard wrenches that fit auger rods, a split spoon sampler, a split spoon sampling driver, sample bags, a tape measure, electrical tape, a camera, and halved PVC pipe (Figure 12). Find a suitable drill and record relevant information (GPS coordinates, elevation, and access) on the drilling log form. Assemble the auger bit, one rod, and the auger handle using WD-40 or similar lubricant on all threads to ensure easier disassembly. Begin coring by turning the auger clockwise; the auger is always turned clockwise only, even when retracting the drill, to ensure no part of the drill gets lost down the hole. After coring for approximately 6”, or when the drilled material reaches the upper edge of the auger bit, retract the drill (with core) from the ground. Using the tape measure, determine the total borehole depth. Lay the 6” sample on a suitable, clean, surface for logging (Figure 13). Describe the sample and place approximately ½ to 1 pound of the sample in a sample bag. Label the bag with the approximate depth. Record depth to water (if water table breached). When the driller can no longer progress the auger because the handle has reached the ground, remove the handle using a wrench and add a second rod (using lubricant), reattach the handle and resume drilling. Continue this process until you reach the desired depth or until you can no longer progress the hole.
  19. 19. ESS 510 METHODS Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 14 of 118 Figure 11. Standard hand auger technology; not a standard crew, however (Cannata). Figure 12. Collection of tools, equipment and people needed for successful augering (Cannata).
  20. 20. ESS 510 METHODS Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 15 of 118 Figure 13. Emptying and sampling from the auger (Cannata). Split Spoon Hand Augering In addition to coring and recording approximate depths as with the hand auger, one can recover intact core and approximate density or firmness measurements with a split spoon. Begin drilling as with the hand auger. When you reach the desired depth for intact sampling or density/ firmness measurements, assemble the split spoon sampler with the driving handle. Place the coring split spoon in the hole and lift the driving handle to the maximum height. Drop the driving handle; do not push it downwards. Drop the handle repeatedly until the split spoon advances 6” (electrical tape is useful to determine depth progressed by marking the dropping handle or additional rods) and record the number of drops on the log sheet. Continue this process twice more for a total of 18”; you can
  21. 21. ESS 510 METHODS Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 16 of 118 determine the density/firmness of the unit using the last 12” of the unit with corrections specific to the split spoon and drop handle. Carefully remove the split spoon sampler and lay it horizontally on the ground. Remove the upper and lower screw rings and one half of the split spoon sampler. Using a tape measure, determine the borehole depth. Mark the borehole depth on the sample in some manner and photograph the sample. Log the intact core. Carefully remove the 18” sample from the split spoon and place it is the halved PVC pipe. Continue this process (adding rods when necessary) until desired depth or refusal. 2.4 Discontinuity Mapping Discontinuities arise from a variety of geologic factors that affect outcrop integrity, with some common discontinuities resulting from lithology and alteration differences, disconformities, and structural changes. Discontinuities may be diagnostic of important outcrop changes and serve as the basis for discerning domains. Discontinuities exist at several scales in most outcrops, so observations should be made at several scales. One can document differences in geology by defining any number of “domains” which help subsequent identification and description. First, stand far enough back so you can observe the entire outcrop. From here, look for linear to sub-linear features that may define structural or potential lithology changes. Next, look for color changes that may distinguish lithology, alteration, or weathering changes. Then, look for textural changes that may signify weathering, lithology or alteration changes. Once you’ve identified possible discontinuities, examine the units on either side of the potential discontinuity to determine the nature of the differences between units. Describe and document the differences between the units in the geologist field book. To aid in identification and clarity, one should ascribe a number or letter to each domain (e.g. a, b, c or I, II, III). If the potential discontinuity marks notable changes, document and describe the orientation and nature of the discontinuity in the same manner as each unit. The method for documenting small-scale discontinuities should be the same as large-scale discontinuities; however, one should restrict these discontinuities to a single domain. Descriptions should continue at increasingly smaller scales until the geologist has reached the desired mapping resolution.
  22. 22. ESS 510 METHODS Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 17 of 118 2.5 Provenance Determination Provenance can be a diagnostic tool for distinguishing glacial from non-glacial deposits. Since interglacial deposits can be mobilized sediments from prior glaciations, and since glaciations remobilize local geologic units, identifying outliers is important for interpreting provenance. Sand provides the best determination for provenance, so one should use sand samples whenever possible. The only necessary materials are a low-power microscope, a magnet, and your sample. First, view sand samples under the low-powered microscope. Use any available tools, such as the magnet, to determine proportion of quartz; garnet, epidote, and magnetite (GEM) minerals; volcanics; felsic or granitics; lithics and organics. Estimate rough percentages of each mineral type (to within 10%). Compare several samples from each location and determine relative percentages for each provenance. Some rocks and minerals are diagnostic. Greater than 5% volcanics indicates volcanic (non- glacial) origin. GEM minerals indicate metamorphic terrain. Granitics can be diagnostic of many granitic terrains (though not the Olympic Mountains). One can classify granites by constituent minerals, which may be diagnostic of specific areas. Organics are typically indicative of interglacial, fluvial deposits. The physiographic province of the Pacific Northwest is characterized by the Cascade volcanoes, the Columbia River Plateau, the Northern Cascades, and the Olympic Peninsula and other coastal mountains (insert source). Quaternary glacial and interglacial sediments contain signatures from these provinces; these signatures aid in determining the sediment source and the mechanism of sediment transport for a given deposit. The geologic signature of Mt. Rainier and other Cascade Volcanoes include lahar deposits, extrusive igneous rocks, ash, pumice, and tuff. The Northern Cascades have a different signature which includes high grade metamorphic rocks such as gneiss and phyllite. The Northern Cascades, particularly Mt. Baker and Mt. Garibaldi, provide red (ferruginous) chert (source: Jim Miller, oral communication). The provenance of the Olympic Peninsula is characterized by basalt and micaceous greywacke.
  23. 23. ESS 510 METHODS Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 18 of 118 Differentiating Glacial from Non-Glacial Deposits In the Puget Lowland, fluvial sediments from interglacial periods are mixed within glacial sediments from Cordilleran Glaciation. Distinguishing glacial from non-glacial sediments helps geologists determine stratigraphy and physical properties of geologic units. Three excellent indicators that help tell glacial from non-glacial sediments are provenance, deposition and color. Glacial deposits in the Puget Lowland are ice-borne sediments sourced from the north (North Cascades, British Columbia) containing metamorphic minerals and felsic intrusive fragments. These sediments arrive by glacial advance, recession and as relict deposits dropped from glacial ice. Hand sample scale diagnostic advance and regression indicators include: diamict sediments, non-organically derived clays, salt and pepper coloration from the mix of felsic and metamorphic minerals, and rounded clasts. Glacial till indicators include: poor sorting (diamict), rounded clasts (possibly with glacial striations), fine-grained matrix, and matrix supported. Outwash deposits are some of the thickest glacial deposits in the Puget Lowland. Distinguishing the origin of the sand grains is the best manner of determining provenance. Diagnostic minerals for determining glacial origin of sands are GEM minerals, green and/or red coloration, relatively high quartz (~ > 70%) content, low mica content, and low Potassium Feldspar content. Additionally, dark purple to black coloration of beach sands is indicative of GEM minerals, even in hand specimen. Fluvial sediments in the Puget Lowland derive from melting winter snows and alpine glaciers to the east in the Cascade Range. Along with typical stream-borne sediments, mass-wasting such as lahars also form interglacial deposits. Diagnostic fluvial sediment indicators include: smaller structure size (cross-bedding, imbrication), well sorted, clast-supported, composed of upstream bedrock, and organics mixed with volcanics (colorful). Mineralogic indicators of interglacial sediments include: high mica content, larger mica grains, higher Potassium Feldspar content. Lahar indicators include: angular fragments, poor sorting, volcanic fragments, and fine-grained matrix, often clay rich with easily weathered volcanic material (colorful). An important part of interglacial identification is awareness of local geology. Glaciations remobilize local rock types, but also transport non-local rocks. Identifying rocks that do not belong to the local environment is the best way to distinguish between glacial and non-glacial deposits.
  24. 24. ESS 510 METHODS Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 19 of 118 2.6 Soil Classification Describing samples in the field and relating the descriptions to USCS conventions allows understanding of material properties without expensive and time-consuming laboratory testing. Field (visual-manual) descriptions are not a substitute for laboratory classification. One should follow the standard method for field descriptions: ASTM D2488-09a Standard Practice for Description and Identification of Soils (Visual-Manual Procedure). 2.7 Test Pit Observations Test pits provide shallow vertical, but laterally extensive subsurface exposure. Though drilling may provide significant deeper information, test pits are typically less expensive than drilling and can provide shallow surface contextual information that drilling may not. FIGURE 14. On Mike Brown’s property, Troost leads a discussion about the geology of the test pit (Cannata). The necessary materials are: a test pit logging form, several colored pencils and pens, unit description standards, and a camera. One should perform pit observation and description in a similar manner to outcrop descriptions. Because test pits are typically refilled after description, it is important to take special care with documenting and descriptions. One should: photograph test
  25. 25. ESS 510 METHODS Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 20 of 118 pit walls, accurately measure test pit dimensions, map domains, describe units, discontinuities, and soil horizons using the same method for describing outcrops, and create an accurate section profile of each wall of the test pit. Do NOT enter the test pit if greater than 4’ deep (per OSHA standards). 2.8 Geographic Positioning System Prior to the start of this field course, UW’s Department of Earth and Space Sciences purchased two Trimble 7x Geo handheld global positioning systems with centimeter scale accuracy. While Trimble’s data collection software (Terrasync) is very straightforward and user-friendly, its post- processing software (Pathfinder Office) is not. This methods subsection is intended to aid future MESSAGe students with the data flow from the GPS into ArcGIS. The first step is to transfer files from the Trimble unit. Using the USB cable, connect the handheld to a computer that has Pathfinder Office installed (such as the Dell Optiplex 755 in the MESSAGe workroom). Open Pathfinder Office, and then click ‘data transfer’ under the utilities tab. Once you’ve transferred the files to a computer, click ‘open’ under the file tab and select one of the .SSF files. Next, go to ‘differential correction’ under the utility tab. Select a nearby base station (<150 miles) with a good rating (>90). For work in the Puget Lowlands, you’ll most likely want to select the Eatonville station. The differential correction creates .COR files which we now export into ArcGIS. Go to ‘export’ under the utilities tab. Choose the appropriate file and select ‘New ESRI Shapefile’ from the dropdown menu. Set the properties you want; these will appear as attributes in your shapefiles. You might as well check all of them; it’s always better to have too much data than too little. Next you need to define your export projection file under the coordinate system tab. This step is tricky because ArcGIS versions 10.1 and later no longer include coordinate system projection files. That means we have to find or create them ourselves! We collected data in the WGS1984 coordinate system so we created the WGS1984.prj file and placed it on the aforementioned MESSAGe workroom computer. To create another .PRJ file, open Arc and go to the properties of some arbitrary shapefile. Under the coordinate system tab, browse to the file you want and click the ‘add to favorites’ icon. This will create a .PRJ file
  26. 26. ESS 510 METHODS Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 21 of 118 somewhere on the hard drive (the exact location varies by machine). Once you’ve located the .PRJ file, browse to it from the Pathfinder Office window and assign it as the projection file. Alternatively, one can download the .PRJ files directly from the internet (Seilermapsupport, 2012). Lastly, it is very important that you rename each new shapefile before creating the next one (and, of course, it is important that you only rename shapefiles in ArcCatalog)! Pathfinder Office creates one generic file name, so if you don’t rename the files each new one will overwrite the previous one. I advise keeping the names of the respective .SSF, .COR, and .SHP consistent.
  27. 27. ESS 510 GEOLOGIC, GEOMORPHIC AND TECTONIC SETTINGS Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 22 of 118 3.0 GEOLOGIC, GEOMORPHIC AND TECTONIC SETTINGS 3.1 Vashon and Maury Islands The channels of Puget Sound surround the elongate, NNE to NE-trending Vashon-Maury Island of King County. The island is located about 20 km southwest of downtown Seattle within the broad, low-lying Puget Lowland physiographic province (Booth, 1991). Vashon and Maury Islands connect through an isthmus that local citizens built in 1913 near the community of Portage. Prior to 1913, the connection between the islands existed only during periods of low tide (John Manke, personal communication, 6/16/2014). The combined surface area of Vashon and Maury Island is about 96 km2 with a maximum elevation over 200m above sea level, making it the largest island in the Puget Sound south of Admiralty Inlet. Steep, variably vegetated bluffs rise to over 100 m above the island shoreline, exposing 80 km of south-central Puget Lowland glacial and non-glacial sediments around the island perimeter. The material exposed in the bluffs is a sequence of consolidated and unconsolidated deposits representing the arrival of the Vashon-age Puget Lobe of the Cordilleran ice sheet (Borden and Troost, 2001). Working upward from the bluff base, low-permeability glaciolacustrine clay and silt deposits are overlain by permeable sand and gravel glacial advance outwash deposits, which are in turn capped by glacial till. The contact between the clay unit and the outwash forms an important structural component of the Island in terms of geomorphology and slope stability, and is important hydrogeologically in producing the aquitard underlying the outwash aquifer. Evidence of ice-contact on the land surface is common throughout Vashon Island as sediments held within melting ice were deposited in localized concentrations, forming a rounded and undulating, hummocky land surface (K. Troost, personal communication). Vashon Island lies within the east-west compressional tectonic regime of the Cascadia subduction zone and the north-south compressional tectonics of the Tacoma fault (TF) (Figure 15). The eastern section of the TF extends through Colvos Passage, across the southern half of Vashon Island, and across Poverty Bay to East Passage near Des Moines, WA (Johnson et al., 2004). The TF is a system of north-dipping faults that are considered backthrusts of the Seattle fault. Backthrusts are rare, thin-skinned crustal shortening events occurring in fold and thrust belts during the propagation of forelands (Heim, 1997). One can see evidence of the TF in the bluffs over Sandford Point in which the older glaciolacustrine deposits have been thrust nearly
  28. 28. ESS 510 GEOLOGIC, GEOMORPHIC AND TECTONIC SETTINGS Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 23 of 118 vertically upward to make a steep contact of apparent southward dip with the younger glacial outwash deposits. Figure 15. Structure contour map showing the altitude of the Vashon advance outwash base, in feet (Booth, 1991). Inset map shows the approximate locations of two Tacoma fault strands affecting Vashon Island (Nelson, et al., 2008). I = Camp Sealth, II = Van Os Feeder Bluff, III = Sandford Point.
  29. 29. ESS 510 GEOLOGIC, GEOMORPHIC AND TECTONIC SETTINGS Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 24 of 118 3.2 Sequim This section will focus on the geologic, geomorphic, and tectonic setting of the Sequim area in the eastern half of Juan de Fuca Strait. This study area is within an active tectonic plate margin known as the Cascadia subduction zone, where the Juan de Fuca plate is subducting beneath the North American plate. The geology of the Sequim area is a glaciated marine and fluvial environment with strong evidence of recent uplift (Figure 16). The stratigraphy is dominated by a complex fill of glacial and interglacial deposits (Johnson et al., 2001). Offshore seismic- reflection profiles show Pleistocene strata bounded by underlying Tertiary basement rock and overlying post-glacial and Holocene deposits (Hewitt and Mosher, 2004). Currently, the eastern Juan de Fuca Strait has a relatively low sediment input with only a few small creeks draining the peninsula, resulting in sediments consisting of reworked shoreline and marine bank deposits (Hewitt and Mosher, 2001). The Sequim area lies on the north shore of the Olympic Peninsula, where evidence of recent continental glaciation is exposed along bluffs and in beach environments. Lobes of continental ice occupied these environments several times during the late Pleistocene. During the Vashon Stage of the Fraser glaciation (15-13 kya), a lobe of the Cordilleran Ice Sheet extended westward from the Puget Lowland into Juan de Fuca Strait (Thorson, 1980). The Juan de Fuca lobe reached the edge of the continental shelf at its peak around ~14 kya, before rapidly retreating back into the Puget lowland and to the Canadian border by ~13 kya (Hewitt and Mosher, 2001). Rapid glacial retreat left behind deposits of ice-contact, glacial-marine sediment, and post-glacial sediments, which experienced marine transgression and regression due to regional isotatic rebound of the crust and global change in mean sea level following deglaciation (Dethier et al., 1995). During glaciation, the crust depressed from the weight of the overlying ice sheet. Once the ice sheet retreated, the land was still depressed and marine water reoccupied the Juan de Fuca Strait (the Everson marine incursion). As the crust isostatically rebounded, local sea level decreased while eustatic sea level began rising due to global deglaciation. An elevation model of the region (Figure 17) shows relatively flat wave-cut surfaces that may indicate temporary marine shorelines at different stages of isostatic rebound and eustasy.
  30. 30. ESS 510 GEOLOGIC, GEOMORPHIC AND TECTONIC SETTINGS Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 25 of 118 Figure 16. Geologic map of the Sequim area produced in ArcGIS (data from WA State DNR).
  31. 31. ESS 510 GEOLOGIC, GEOMORPHIC AND TECTONIC SETTINGS Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 26 of 118 Figure 17. Digital elevation model of the Sequim area, Washington (ArcGIS) Sequim sits at the intersection of the uplifting Olympic Mountains and the east-west trending, active crustal faults of the Puget Lowland (Figure 18). Our study area lies just west of a major north-trending crustal boundary between pre-Tertiary and Tertiary basement rocks to the east and younger Eocene rocks to the west (Johnson et al., 1994). Two major crustal fault systems border the Sequim area to the east: the southern Whidbey Island fault zone (SWIF) and the Hood Canal fault zone (HCF). Offset and deformation of strata at the base of the Quaternary and within the Quaternary are visible in seismic-reflection profiles and provide evidence for Quaternary movement on the SWIF (Johnson et al., 1996). Ice unloading may have induced seismicity and fault movements in the upper crust on a shorter time scale than would normally occur. Tsunamis from both subduction zone and crustal earthquakes pose a major threat to shorelines throughout the Puget lowland (Williams et al., 2005).
  32. 32. ESS 510 GEOLOGIC, GEOMORPHIC AND TECTONIC SETTINGS Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 27 of 118 Figure 18. Structural elements of the Puget Lowland (taken from Johnson et al., 1999) Figure 19. Sketch of littoral sediment transport at the beach below Van Os Feeder Bluff (Cannata).
  33. 33. ESS 510 FINDINGS: VASHON ISLAND Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 28 of 118 4.0 FINDINGS: VASHON ISLAND 4.1 Van Os Feeder Bluff Sediment transport Sediment transport in coastal environments involves the interaction between geologic materials and dynamic surface processes. Drift cells illustrate a complete cycle of sedimentation in coastal systems; the sediment source area, generalized transport pathway, and final sink area. Geologists have mapped drift cells in the Puget Lowlands for several decades to analyze the complex coastal erosion properties of the Puget Lowland region. The Van Os feeder bluffs have complex stratigraphic units containing sands, silts, clays, and different sized gravels. The bluffs supply sediment to the beach via mass wasting where wind and wave action become the primary transport mechanisms. The dominant drift cell is westward with a less dominant eastward component that meet at the cuspate portion of the beach. These drift cells (Figure 19) are likely causing sediment to aggrade in the apparent downdrift beach cusp. In the westward direction, sand content of the beach decreases while the concentration and size of gravels on the beach increases. A natural accumulation of boulders and large cobbles occupies an approximate 100 square meter area in the intertidal zone of the shore face. This lobate deposit resembles and probably acts like an anthropogenic jetty or groin structure (Figure 20). The intertidal zone widens close to this structure. The directions of the drift cell and accumulating cuspate formation suggest that higher-energy flows may transport and deposit cobbles and gravels at the structure; however, the transport mechanism for the boulders remains enigmatic, but is thought to be associated with high-energy sub-glacial processes during the Vashon glaciation (class discussions). The origin of the boulders is most-likely local even given the Vashon-age transport mechanism; although it is not impossible these boulders were transported from elsewhere. The shape of the beach and lack of sand suggest that the beach west of the lag deposit is eroding more quickly than the east. The slope of the beach shallows from west to east. Elevation Profile and Measured Section for Van Os Feeder Bluff Groups established a GPS base station along each section line. Using a Trimble Geo 7x handheld GPS unit, teams established location and elevation data for each base station. From each base
  34. 34. ESS 510 FINDINGS: VASHON ISLAND Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 29 of 118 station, teams used a Laser Rangefinder to determine horizontal and vertical distances to elevation and geology breaks and changes. By plotting these distances on a vertical section map, teams established four elevation profiles with associated measured geologic sections (Figure 21). Provenance Charts for Sandford Point and Van Os Feeder Bluff Groups sampled each distinct geologic unit at each section. At Camp Sealth, we analyzed these samples to determine provenance using the standardized method (Appendix). Pebble Counts for Van Os Beach Along each section, groups chose an area on the beach to perform a Wolman pebble count in order to measure grain size distribution. We used a 1 x 1 meter square sampling area and randomly measured 100 individual grains and classified them with a Gravelometer. Kristina Sumner compiled pebble counts (Appendix B). Figure 20. Jetty-like lag deposit downdrift of the Van Os bluffs (Cannata).
  35. 35. ESS 510 FINDINGS: VASHON ISLAND Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 30 of 118 Figure 21. Section of Transect 4 at Van Os bluffs (Cannata).
  36. 36. ESS 510 FINDINGS: VASHON ISLAND Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 31 of 118 4.2 Sandford Point Structure and Seepage Maps for Sandford Point To assess the stability of the bluff between Sandford Point and Christiansen Cove, we documented hazards, geologic structure, material properties, and groundwater exposure along approximately 0.6 mile beach and bluff reach. We accomplished this task in 1.5 days, and broke up into groups by discipline focus: Structural geology: Cesmat, Conrado, Favia, Gault, Manke, Tinklepaugh. Seepage: Holmes, Marshburn, Spickert, Sumner. Geomorphology: Cannata, Fish, Twomey, Wilson. Provenance: Eckles, Gauglitz, Pivaroff-Ward, Weitering. Along this reach, we established 15 GPS stations (labelled A to M) seaward of key areas of interest (Figure 22). Teams used these GPS locations for reference. Our group activities included observing landslide scars and slumps, measuring strike and dip of bedding, contacts, faults and folds, collecting samples for provenance analysis, and identifying the locations and nature of groundwater seeps.
  37. 37. ESS 510 FINDINGS: VASHON ISLAND Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 32 of 118 Figure 22. Map of Sanford Point with GPS coordinates (Cesmat).
  38. 38. ESS 510 FINDINGS: VASHON ISLAND Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 33 of 118 Structural geology Geologic units at Sandford Point on Vashon Island contain evidence for deformation that is likely related to the Puget Lowland compressional tectonic regime. The Puget Lowland lies within an active compressional regime where active crustal faults displace Quaternary glacial deposits and older Tertiary bedrock. Because the Quaternary deposits at Sandford Point are unconsolidated, deformation within them can be convoluted and difficult to interpret. At Sandford point, bluff faces show evidence for displacements between clay and overlying sand. We made interpretations based on these observations and on existing data from published maps. One can find two types of deformation in Puget Lowland glacial deposits: tectonic deformation from crustal faults and deformation from ice. Distinguishing the two at a small scale (outcrop scale or smaller) can be difficult. At Sandford Point, as stated above, we interpret the deformation to be tectonic. This reasoning is two-fold: the relative sense of motion of the clay with respect to the sand indicates deformation from crustal faults and the presumably large amount of offset is unlikely to occur as a result of ice deformation. The western end of the Tacoma Fault cuts through this region of Vashon Island. The Tacoma Fault is a high angle reverse fault with as much as 10 kilometers of offset (Sherrod et al. 2004). The Tacoma Fault is a north-dipping fault that verges to the south. Structures observable at the outcrop scale include joint sets within the clay, offsets within the sand, and fault planes that displace stratigraphic contacts between the clay and the overlying sand. Joint sets within the clay form a conjugate pair (Figure 23) indicating that during deformation parts of the clay behaved as a brittle material. A π-diagram analysis of fold limb orientations at the northern portion of the study area (Figure 24) yields a fold axis orientation of approximately 160:40 (Figure 25). A fold axis helps determine the compression direction of the tectonic deformation, which is perpendicular to the trend of the fold axis. The northern part of the study area at Sandford Point has a compression direction that is generally northeast- southwest. This is somewhat consistent with published literature where the compression direction is north-south (Sherrod et al. 2004). In order to calculate a more accurate fold axis orientation, more data needs to be collected. Two dominant fault planes are visible along the bluff. The southern fault surface is a zone of deformation that is approximately six feet wide. The deformation zone between the sand and
  39. 39. ESS 510 FINDINGS: VASHON ISLAND Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 34 of 118 clay is marked by oxidation, some brecciated clay, and folding. Folding within the clay and the sand is foot to sub-foot scale. These folds are indicative of plastic-type rheological behavior that occurred during deformation. Because this deformation zone contains both folding and brecciation, one can infer that the material behavior changed during deformation. Figure 23. Joints in the clay unit plotted on a stereonet show that the joints form a conjugate set. Figure 24. Jesse Favia pointing out folds at the north end of Sandford Point
  40. 40. ESS 510 FINDINGS: VASHON ISLAND Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 35 of 118 Figure 25. Pi-diagram of fold limb and hinge line orientations from the northern part of the study area at Sanford Point. Yellow indicates fold axis orientation. The southeastern quadrant contains hingeline orientations and the north eastern. Water Seepage During our time at Sandford Point we observed two major seeps. Both seeps were located in the northernmost portion of the study area. We observed Seep #1 in the fractures in the lower clay unit. In the sand unit above, there was no surface expression of the water. However, wet-soil vegetation on the bluff suggests that water moves somewhat freely throughout the sand unit. Seep #2 was visible on the surface above the clay unit and formed a small stream coming down the bluff-face and continuing across the beach. After further investigation higher on the bluff, we observed that the seep begins almost near the top of the bluff. The water then persists as both surface flow and near-surface groundwater flow. Similar areas of over-saturated ground likely form elsewhere on the bluff during wetter times of the year. Geomorphology Our field reconnaissance at Sandford Point revealed slope failures dominated by mechanisms alternative to the notorious deep-seated rotational failure associated with the infamous contacts between the outwash sands and lacustrine clays along the Puget Sound coast. We expected to see some evidence of shallow or deep-seated rotations in addition to sand colluvium accumulating atop a prominent clay bench.
  41. 41. ESS 510 FINDINGS: VASHON ISLAND Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 36 of 118 Instead, we observed no evidence for rotational or translational failures of the clay formation, nor evidence for significant wave-cut erosion at the bases of the cliffs. We mainly saw both clay and sand bluffs failing as block or slab falls (Figure 26), while colluvium of these materials expressed varied failure types, like debris and mud flows (Figure 27), creep, and translational slides. On exposed surfaces, root growth appeared to be an active force of physical weathering on both the clay and sand units (Figure 28). There were areas of clay, drier and weaker than typically seen, that displayed fissures approximately ½” deep. Figure 26. Farin Wilson standing at Station B pointing out the water seepage and root action working on the clay formation. At her feet are intact cobble and boulder-sized blocks of clay formation that have fallen from in-situ (Cannata).
  42. 42. ESS 510 FINDINGS: VASHON ISLAND Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 37 of 118 Figure 27 (Above). Niall Twomey, Bart Weitering, and Evan Eckles at the base of a debris/mud flow that appeared to be channelized by the surrounding geologic formation (Cannata). Figure 28 (Right). Close up view of the effects of physical weathering (root action) on the sand formation. Note the blocky angular nature of the stable sand face around the area that has failed. This suggests the sand is partially cohesive and must be failing by slab and block fall (Cannata).
  43. 43. ESS 510 FINDINGS: VASHON ISLAND Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 38 of 118 Provenance On June 17, 2014 Katie Gauglitz and Kendra Pivaroff-Ward sampled each unit in the bluffs at Sandford Point at designated reference points marked A through M (Figures 22, 29). They found that there were two dominant units; one was a fine-grained sand with coarse sand and gravel, and the other was a sandy clay with silt and coarse sand and fine gravel dropstones. We analyzed these samples in the laboratory using microscopes to determine the provenance of the units. The results (Appendix B) were inconclusive. It is unclear whether or not the sand unit is continuous throughout the study reach or if multiple sands from various provenances compose what was observed and sampled in the bluffs during our visit. Figure 29. Sandford Point bluff sketch.
  44. 44. ESS 510 FINDINGS: VASHON ISLAND Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 39 of 118 4.3 Brown Property & Hydrologic Conceptual Model The locations of subsurface exploration were in the low- and mid-lying topographic areas of a partially-incised valley and on the upper east half of the property (Figure 30). We divided into 3 teams, each taking a turn at trench logging (excavation), manual augering with a standard auger (southwestern-most borehole in valley), and manual augering with a split-spoon auger (south of residence). Each team mapped the trench and drilled and sampled boreholes according to the Unified Soil Classification System and the Standard Operating Procedures outlined in Methods. We collected digital GPS locations of all subsurface points of exploration, and used an autolevel for measuring relative elevation data. We collared 3 split-spoon boreholes on the southeast part of the property approximately 10 m south of the house, in an area claimbed by the resident to be seasonally dry (denoted on map). Two of the three standard auger boreholes were located in topographic depressions on the southwest portion of the property (lowland area on map). One was collared in a depression that ponded water prior to the 2001 Nisqually Earthquake, while the other borehole was collared against the chain-link property fence that runs west alongside the boundary at the topographical low of the property. For trench logging, we described the walls of a 14.5ft by 2.5ft by 5ft (L x W x D) trench excavated by the property owner in the mid-section of the property. The results of the trench observations are detailed in Figure 31. In addition to our group’s subsurface findings, we compiled well logs from historic drilling activities (Figures 32 and 33) to aid our development of the hydrostratigraphic conceptual model. In this case, a simple conceptual model is illustrated in Figure 34. A shallow (3 feet) veneer of brown loose silty gravelly sands with organics (artificial fill) overlies a mottled grayish brown dense, partially weathered, matrix-supported diamict (glacial till), which is underlain by a gray saturated silty clay (glaciolacustrine). This stratigraphy resembles the typical sequence of glacial advance - glacial till overlying glaciolacustrine deposits - and has implications for the hydrogeologic nature of the site.
  45. 45. ESS 510 FINDINGS: VASHON ISLAND Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 40 of 118 Figure 30. Sketch of property (Cannata, inspired by J.Tinkleplaugh’s drawing). Figure 31. Observation sketch and stratigraphic column (right) of excavation trench (3H: 4V exaggeration; Cannata). Root-like structures are un-weathered centrally along their axes while bound by rust-colored margins that are interpreted as zones of accumulation metal oxides and that represent the advancing weathering zone.
  46. 46. ESS 510 FINDINGS: VASHON ISLAND Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 41 of 118 Figure 32. Oblique Google map with approximated locations of four historical well logs (F.Wilson).
  47. 47. ESS 510 FINDINGS: VASHON ISLAND Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 42 of 118 Figure 33. Summary of Ecology well logs for four past drilling events (four left columns) and two boreholes by UW MESSAGe 2G (two right columns) (F.Wilson). All stratigraphic columns are vertically oriented by surface elevation as measured on the far left axis (elevation in feet above sea level). The scales immediately to the left of the columns denote depth of boring.
  48. 48. ESS 510 FINDINGS: VASHON ISLAND Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 43 of 118 Local topography, stratigraphy, and geologic materials control groundwater flow. The water table in the phreatic zone usually reflects surface topography. Groundwater generally follows the local topography from higher to lower elevations. For this site, the upper east half of the property flows into to the lower elevations of the western half, and then eventually down to sea level at the coast (Figure 34). The local stratigraphy and geologic materials are responsible for heterogeneity and anisotropy of the subsurface, which result in the formation of preferential flow pathways and variations in hydraulic conductivity. Groundwater tends to follow the preferential pathways and areas of relatively higher hydraulic conductivity. The Holocene fill and glacial till are more permeable and hydraulically conductive than the underlying silty clay unit. As a result, groundwater flow may partially deflect at this contact and favor horizontal movement. Figure 34. Hydrogeologic conceptual model with elevation (feet above sea level) versus horizontal distance, and with illustrated stratigraphic findings from hand augering (Cannata, Wilson). The brackets around the geologic contact constrain the possible position range as a result of limited subsurface exploration. Blue line approximates the water table.
  49. 49. ESS 510 FINDINGS: NORTHEAST OLYMPIC PENINSULA Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 44 of 118 5.0 FINDINGS: NORTHEAST OLYMPIC PENINSULA 5.1 Discovery Bay Physical Description The southern tip of Discovery Bay is a broad tidal flat nestled between forested areas of higher relief to the east and west. An abandoned train trestle and the intersection of Highways 20 and 101 bound the tidal flat to the south. The site is part of a restored estuary with a primary goal of improving fish and wildlife habitat. Several creeks intersect dense areas of reed grass in reaches outside the high tide zone, including Salmon Creek, which flows northwest through the estuary into the bay. Within the tidal zone, soft, fine-grained sediments are cut by intertidal streams. Geologic Materials The geologic materials in the study area consist of saturated organic soils with intervals of sandy soil (Figure 35). The organic soils range in character from dark brown to brown and grey, mottled peat, silty peat and clayey peat. We determined this by the behavior of the soil during a Humus Test. Thin layers of sandy soils interbedded within the silty organic soils indicate deposition in a higher energy environment, such as that of a tsunami, than normally exists in the quiet estuarine environment. These sandy layers are greenish grey, contain silt and clay, and range in thickness from <5cm to >10 cm. We encountered them at depths of 0.6m – 1.0 m in the tidal marsh areas on the north side of the train trestle (Figure 36). A more detailed description of the sediment core samples is given in Appendix B.
  50. 50. ESS 510 FINDINGS: NORTHEAST OLYMPIC PENINSULA Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 45 of 118 Figure 35. Tsunami sand layer in the bank of Salmon Creek, which cuts through the salt marsh at the head of Discovery Bay (Ian Miller) Figure 36. Core sites in the Discovery Bay marsh on 20 June 2014 (Ian Miller)
  51. 51. ESS 510 FINDINGS: NORTHEAST OLYMPIC PENINSULA Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 46 of 118 Figure 37a. Measured section of reference point 1 Figure 37b. Measured section of reference point 2
  52. 52. ESS 510 FINDINGS: NORTHEAST OLYMPIC PENINSULA Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 47 of 118 5.2 Dungeness Bluff Physical Description The bluffs we studied are located within the Dungeness Recreation Area and National Wildlife Refuge of Clallam County. We separated into two groups and examined two sections of bluff to the west of the beach entrance (Figure 37). To the east of the entrance, a 6.5 mile long spit extends northeast into the Strait of Juan de Fuca. The bluffs to the west of the entrance were roughly 120 feet tall with sparse vegetation on the slopes. There were signs at intervals along the base of the bluffs warning visitors to stay off the slopes. The three main units present at each outcrop are sandy gravel, lenticular sand and gravel, and a fine-grained layer. Geologic Materials Sandy Gravel The bottom unit consists of sub-rounded gravels and a dark gray fine- to medium-grained sand matrix. It is mostly covered at beach elevation. We observed that the material was dense and moist, likely due to exposure to high tides. The presence of greywacke indicates that the gravels derive from the Olympic Mountain Range. We estimated the unit to be at least several feet thick, although our observation point was limited by the base of the bluff. Lenticular Sand and Gravel The sand displays many cross bedding relationships with thick lenses of sand and gravel. This unit is up to 50 feet thick in areas and was often covered by sandy colluvium. Sand and gravels from the unit appear to have northern provenance, suggesting glacial transport. The unit’s thickness and provenance suggest that this deposit is glacial outwash. Fine Grained Unit We measured the silt and clay unit to be approximately 10 feet thick. It was dark gray, very stiff and massive at beach level. We observed another exposure approximately 75 feet up the bluff with sand and gravel; it appeared that the sand was differentially eroding from the unit. These sediments were likely deposited in lacustrine environments, possibly from pro-glacial lakes. Bluff Retreat and Sediment Transport
  53. 53. ESS 510 FINDINGS: NORTHEAST OLYMPIC PENINSULA Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 48 of 118 There are three main modes of bluff retreat at Dungeness Bluff: dry ravel, small scale mud flows, and block topple. During the time of our visit, dry ravel appeared to be to dominant mode of bluff retreat. We observed colluvial fans at many points along the base of the bluff as well as small dry flows of sand and gravel (Figure 38). Shallow incisions were present on some portions of the site, indicating water-aided sediment transport off of the bluff. Gravels were the most evident within the cut channels, showing that the sandy matrix of the gravel lenses were preferentially eroded during times of precipitation. Figure 38. Dry ravel, colluvial fans on the bluff face at reference point 2 (Weitering) Given that the Dungeness Spit has been built up to the northeast, it stands to reason that the alongshore drift is transporting sediments to the northeast. This process of bluff erosion provides a constant source of new sediments which reinforce the spit.
  54. 54. ESS 510 FINDINGS: NORTHEAST OLYMPIC PENINSULA Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 49 of 118 5.3 Sequim Bay State Park Physical Description We studied beach bluffs within Sequim Bay State Park to analyze the geologic composition and strength of the bluffs. Our class split up into pairs and mapped 100 foot sections of the bluff. The bluff ranged from about 15 to 30 feet high. A stream bisects the bluff. It has varying degrees of vegetation. Fallen trees were present on the beach. Most logs were still perpendicular to the slope, suggesting minimal wave action within Sequim Bay. A restroom inland from the beach closed in 2008 because soil creep and weak geologic materials threatened the building’s foundation. The slope consists of two main units: till and a younger weathered sedimentary unit (Figure 39). Geologic Materials Till The till layer is approximately 5 feet thick. It’s a dense gray diamict with well-rounded gravel and cobbles of northern provenance. Tree roots extensively bioturbated the top of the unit, and the lower part of the unit is oxidized. We interpret this unit as till for several reasons: the glacial history of the area, the northern sourced sediments within the unit, and its high density. Some larger intact blocks of this unit can be seen slumping down on to the lower unit. Fine Grained Sandstone The Oligocene Makkah Formation, in the Twin Rivers Group, is grey fine-grained sandstone variably weathered to a reddish-brown color. Exposures of this unit are greater than 20 feet thick in areas, but outcrops on the beach indicate that the unit extends below beach level. Most of the unit is heavily fractured and blocky. This fracture texture likely allowed water to infiltrate through most of the rock, which expedited weathering on the exposed face. According to the International Society of Rock Mechanics’ (ISRM) guide to state of weathering, most of this unit would be considered moderately (III) to highly (IV) weathered. We classified the strength of this section as R1 or very weak rock by the IRSM’s guidelines for describing rock strength. The highly weathered nature of the country rock made it difficult to discern consistent strike and dip of discontinuities.
  55. 55. ESS 510 FINDINGS: NORTHEAST OLYMPIC PENINSULA Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 50 of 118 Further north, the fine-grained sandstone bedrock was light gray in color and contained two discrete layers of large carbonate concretions. Several joints cross-cut the outcrop with major sets striking 50, 70, 305, 350 degrees and dipping 48S, 78N, 31W, 48W, respectively. They have 1 to 3 cm spacing, very low to medium persistence, 1 to 2 termination, and R3 strength. The bedrock weathers flaky and blocky in particular sections. Some areas of the bedrock experience more oxidation than others due to seepage coming from the top of the bluff. The areas affected by the seepage are slightly less indurated and discolored than the rest of the rock. The rock is grade II: slightly weathered and has rock strength R2: weak (ISRM). It has low hardness (LH) based on the FHWA, 2002b guidelines. The concretions are much harder than the parent rock (R4 strength). As the bluff retreats and the parent rock erodes, the concretions fall out onto the beach, leaving oval shaped cavities in the outcrop. Bluff Retreat and Sediment Transport Upslope evidence, such as the defunct restroom and crooked trees, suggest soil creep processes occur in the Sequim Bay area. This process appears to be gradual with occasional small landslide events. The beach bluff expresses this through the undermining of the relatively intact till layer by removal of the underlying weathered sedimentary unit. Evidence of undermining is exists in small colluvial fans collecting on the beach that appear to derive from the lower sandstone unit. Considering the high degree of fracturing and oxidized state of the sandstone unit, it is likely that water can travel through the unit with relative ease. Water increases the pore pressure within the unit, destabilizing the slope and cause small translational slides. We observed a tension crack roughly 330 feet northwest of the Sequim Bay moorage dock, parallel to a 3 to 4 foot high scarp above a slumped section of the bluff. This feature suggests that the slope can fail by translational movements. Sediment transport is minimal within Sequim Bay. Observations of fallen trees resting perpendicular to the bluff are consistent with the minimal wave action in the sheltered bay. Most of the sediment transport in this research area appears to be centered around the stream running northeast into the bay. This stream has deposited sediment around its mouth, creating a fan that extends 75 feet into the bay.
  56. 56. ESS 510 FINDINGS: NORTHEAST OLYMPIC PENINSULA Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 51 of 118 Figure 39. Sequim Bay State Park bluff sketch
  57. 57. ESS 510 DISCUSSIONS AND CONCLUSIONS Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 52 of 118 6.0 DISCUSSIONS AND CONCLUSION 6.1 Bluff Retreat Comparison Describe the similarities and differences between the style of bluff retreat for Vashon Island and the bluffs on the Strait. Why might they be different or similar? Johannessen and MacLennan (2007) present a robust synopsis of Puget Sound beach and bluff processes in Technical Report 04 prepared in support of the Puget Sound Nearshore Partnership. Conceptually, they categorize the overall processes affecting bluff systems by first-order factors such as climate and sea-level rise, and then by second-order, site-specific factors. For this discussion, I examine the 4 localities in context of selected second-order factors both quantitatively and qualitatively (where possible). All the second-order factors they present include: 1) Bluff characteristics a. Composition b. Resistance c. Permeability d. Slope structure e. Bluff weakness 2) Local topography (i.e. upland relief) a. Slope’s landslide history 3) Hydrodynamics 4) Natural protection offered by the beach (narrow vs. broad, reflective vs. dissipative) 5) Management practices Because the above factors can have spatiotemporal variability across individual bluff systems, so too can bluff retreat and erosion drivers. For this reason, the erosion drivers can often be difficult to differentiate, so it is helpful to think about them as grouped by marine, subaerial and anthro- induced processes. In doing this, we can better examine the superimposed nature of erosion drivers and how they affect the retreat of a bluff system. Table 1 presents a relatively comprehensive summary of the second-order factors at play on the bluff systems at the 4 localities. I sourced these observations and information from the group
  58. 58. ESS 510 DISCUSSIONS AND CONCLUSIONS Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 53 of 118 report, my field logbook, and memory. I interpreted these data and designated a qualitative color- scheme that corresponds to their significance to bluff stability and erosion susceptibility. This color-scheme is based on my subjective interpretation of each parameter in relation to the bluff system. This qualitative metric is gradational. It starts with green highlighting that indicates the factor most-likely favors slope stability and therefore reduces erosion susceptibility. It then grades into orange highlighting indicating the factor is an intermediary between promotion and reduction of erosion susceptibility. The last metric is red highlighting and indicates that the present circumstances most-likely favor slope instability, which therefore increases erosion susceptibility. The Dungeness bluff system is most likely undergoing the most rapid and intense bluff retreat with the highest erosion rates relative to the other systems. Given the circumstances, its geographic location, orientation, high-degree of exposure to the marine environment, geologic composition, and other characteristics, it is reasonable to argue that the Dungeness bluffs exhibit an extreme case of bluff retreat. The next highest bluff retreat rate most likely occurs at the Van Os bluff system. Here, a combination of the fetch distance (open all the way north to Whidbey Island and further) and marine exposure, orientation (although not ideal for conveyance of winter storm energy but still considerable), and the poorly consolidated nature of the bluff geology itself contribute to erosion. Despite partial vegetation cover and the dissipative effects of the cobble and boulder lag deposit beach-ward of the slopes, these bluffs still exhibit moderate retreat as compared to the others. The last two bluff systems at Sequim Bay and Sandford Point arguably have the lowest relative retreat rates for similar reasons. Sandford Point has higher relief at approximately 50 meters whereas Sequim Bay is only approximately 10 meters above the shore. Despite these upland reliefs, these two systems share the following characteristics that promote slope stability and that I attribute to their lower relative retreat rates: the fact that these units are either consolidated or lithified, and the fact that the slope is heavily to moderately vegetated; limited exposure, fetch, and non-ideal orientation; and a broad shoreface that dissipates incoming wave attack. Also, I noticed an important observation that colluvium-buttressed slopes occurred at 3 out of the 4 bluff systems with Sequim Bay State Park being the outlier. Colluvium-buttressing plays an important role in support of the slope toe while forming a protective barrier against wave attack
  59. 59. ESS 510 DISCUSSIONS AND CONCLUSIONS Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 54 of 118 from the marine environment (Johannessen and MacLennan, 2007). The most-likely reason for this lack of colluvium base is due to the lack of sediment supply above and along this beach.
  60. 60. ESS 510 DISCUSSIONS AND CONCLUSIONS Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 55 of 118 TABLE 1. Summary of bluff characteristics and processes related to bluff retreat with qualitative erosion rates at the 4 field localities. Upland Relief [m] Vegetation Cover Geology and Stratigraphy Aspect [Azim] Exposure & Fetch Slope Failure Mechanisms Beach Type Erosion Drivers Qualitative Bluff Erosion Retreat Van Os (Maury Island) 20 to 30 Moderate (deciduous trees and some brush) Variable (clay to cobble); overall poorly consolidated N Open 58 km to the north sloughing, dry ravel Broad, cobble and boulder lag deposit marine = subaerial = anthro MODERATE Sandford Point (Vashon Island) 50 Heavy (mixed trees and brush) tree fall is usually perpendicular to shore sand < clay; consolidated in places NW Limited by Colvos Passage and aspect variable Broad, some cobble deposits subaerial = anthro > marine LOW Dungeness Coast Bluffs (Strait of Juan de Fuca) 60 to 70 Light to None Variable (clay to cobble); overall poorly consolidated NW Open to Straits de Juan de Fuca sloughing, dry ravel, slumping Narrow (compared to bluff system); no observed lag deposits marine > subaerial > anthro EXTREME Sequim Bay (Strait of Juan de Fuca) 10 Moderate to Heavy (mixed tress and brush) tree fall mainly perpendicular to shore silt < sand; till over lithified bedrock base NE Limited by embayment and aspect slow-weathering bedrock Broad, cobble lag deposits anthro = subaerial > marine LOW Observations Interpretation Location
  61. 61. ESS 510 DISCUSSIONS AND CONCLUSIONS Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 56 of 118 6.2 Sediment Transport Comparison Describe the similarities and differences between beach sediment transport in Puget Sound and on the Strait de Juan de Fuca. Why might they be similar or different? Within the nearshore system, a dynamic exchange occurs between sediment erosion, entrainment, transport, and deposition. Sediment transport within the littoral zone depends primarily on a beach’s exposure to erosion via wind and wave energy, and the availability of sediment sources to feed the nearshore transport system. These components ultimately control the resultant geomorphology of the beach. Because of this formational dynamic and its spatial variability, we observed both similarities and differences in the 4 coastal environments across Puget Sound and the Straits de Juan de Fuca. The sediment transport system at Van Os feeder bluff is unique in its location and orientation within Puget Sound; however, the loose and unconsolidated deposits of its bluffs are similar to the conditions at Dungeness Spit and some parts of Sandford Point. For these reasons, despite its lack of an ideal orientation to the south for the infamous winter wind storms, this beach is open to a substantial fetch to the north, which still fosters a high-energy wave climate on occasion. This wave climate, acting on a bluff of loose and unconsolidated glacial deposits mainly sands, maintains an adequate sediment supply to the nearshore transport system. As a result, the Van Os littoral system is most-likely the second most dynamic and voluminous system in our collective group in terms of sediment erosion, transport and relocation. The sediment transport system at Sandford Point stands apart from the collective group in its relatively well-vegetated bluffs of loose, unconsolidated glacial deposits. This bluff system is rather well-protected from the already-reduced wave and wind climate of the Colvos Passage, which severely reduces the sediment erosion and supply to the littoral transport system, and makes this locality one of the least active transport systems. Sequim Bay is also one of least active transport systems. Effectively, it can be considered an enclosed coastal inlet given its geomorphic configuration, because a barrier beach truncates the majority of the bay’s mouth opening into the Straits de Juan de Fuca, and functions to limit the wave energy into the bay. Further, the bay’s orientation to the north is not ideal for southern wind storms. Johannessen and MacLennan (2007) remark there is no appreciable net shore-drift occurring along rocky shores or in enclosed shorelines. The observed section of Sequim Bay is
  62. 62. ESS 510 DISCUSSIONS AND CONCLUSIONS Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 57 of 118 composed of sandstone bedrock capped by unconsolidated glacial tills. The geologic composition of the bluffs compounded by a reduced wave climate creates an environment that significantly limits the sediment transport system operating within Sequim Bay. In comparison, the sediment transport system operating at Dungeness Spit is a far more high- energy environment and arguably the highest of the collective group, and therefore, most-likely has the greatest capacity for sediment erosion, transport and relocation. Its location and orientation on the Straits provides the ideal scenario for exposure to high-energy storm events. Coupled with the geologic composition of the bluffs, which are rather loose and unconsolidated glacial deposits, make the perfect conditions for voluminous sediment erosion and transport within the nearshore system, even despite a relatively moderate tidal range. Dungeness Spit is probably the most active and dynamic beach system we observed.
  63. 63. ESS 510 DISCUSSIONS AND CONCLUSIONS Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 58 of 118 TABLE 2. Summary of sediment transport system in the littoral zone at 4 field localities. Beach Location Upland Relief [m] Mean Tidal Range [ft] Geologic Composition Beach Type Exposure and Fetch Sediment Source [based on geologic composition] Local Wave Climate Qualifier [based on exposure & fetch] Sediment Transport Qualifier Van Os (Maury Island) 20 to 30 8.071 Variable (clay to cobble; overall poorly consolidated) Broad (cobble and boulder lag deposits) Open (58 km to the north) YES MODERATE MODERATE Sandford Point (Vashon Island) 50 8.071 sand < clay (consolidated in places) Broad (some cobble deposits) Limited (Colvos Passage & aspect) LIMITED MODERATE LOW Dungeness Coast (Strait of Juan de Fuca) 60 to 70 5.342 Variable (clay to cobble; overall poorly consolidated) Narrow (compared to bluff system; no observed lag deposits) Open (58 km to the north) YES HIGH HIGH Sequim Bay (Strait of Juan de Fuca) 10 4.603 silt < sand (till over bedrock) Broad (cobble lag deposits) Limited (embayment & aspect) LIMITED LOW LOW 1 Tacoma, Tide Station # 9446484; 2 Port Townsend, Tide Station # 9444900; 3 Port Angeles Harbor, Tide Station # 9444090 Observation Interpretation
  64. 64. ESS 510 DISCUSSIONS AND CONCLUSIONS Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 59 of 118 6.3 Provenance Comparison Describe the similarities and differences in the provenance of the sand for each site. The provenance of a geologic material describes its origin in geographical space and geological time. This information is helpful to differentiate geologic deposits, especially when other information is limited. In our case, we use provenance studies to distinguish glacial sediments of the Cordilleran Glaciation from non-glacial deposits of interglacial periods. Based on our knowledge of geological history and the geographical distribution of rock lithologies within the local physiographic province, we can rudimentarily associate a given mineralogy with a particular locality and therefore assign a provenance. From this rudimentary association, we can make conclusions about the nature of a deposit and its position within the local stratigraphic sequence. However, our provenance studies should be taken with caution because they lack a credible level of confidence. They would benefit from additional laboratory analyses to provide further evidence to corroborate these findings. We collected sand samples at 4 beach localities. Table 3 organizes the general findings of the 4 provenance studies. From the summarized results, we see that provenance studies can be variable and indeterminate as far as conclusively distinguishing the provenance of a given geologic material. Table 3. Summarized provenance studies of 3 localities. Beach Location Sample 1st dominant lithology 2nd dominant lithology Glacial or Non-glacial Van Os (Maury Island) Section 1 Basalt Andesite Glacial Sandford Point (Vashon Island) variable variable variable variable Transect A Sedimentary Metamorphic Glacial Transect B Granitic Sedimentary Non-glacial Dungeness Coast (Strait of Juan de Fuca)
  65. 65. ESS 510 DISCUSSIONS AND CONCLUSIONS Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 60 of 118 6.4 Residential development at Sandford Point Describe your assessment of the geologic conditions at Sandford Point relative to the high- density housing proposed by King County. Will the residential development be detrimental to the stability of the bluff? What hazards are present that could impact the residents? Should King County allow the development? Regardless of the various hazards present to humanity and the environment, it seems land development is inevitable in the Puget Lowland, especially in coastal areas with scenic vistas. As practicing geologists, we are duty-bound to inform the public of the risks associated with development in such areas of critical geohazards so we can best prepare and be safe in the face of this type of “sustainable” development. The proposed development at Sandford Point, like most of all development on the coastal bluffs in the Puget Lowland, has a mix of positive and negative effects on slope stability. Where possible, geotechnical engineered solutions can be used to either 1) reinforce the positive features of the slopes that naturally decrease risk to public health and safety, or 2) mitigate the increased risk from the negatives presented by the proposed development. With these possibilities in mind, the proposed residential development above the bluffs at Sandford Point could be undertaken if responsible building practices and codes are followed and common sense prevails, while simultaneously even benefiting the public and the environment. The prominent negative features of development on this coastal terrace are associated with the disruption to naturally-occurring processes. For instance, disturbance to vegetation cover, natural groundwater infiltration and surface runoff are in all likelihood to negatively impact the stability of the bluff system by undermining its natural internal cohesion. The presence of buildings and other infrastructure on top of the terrace introduces a loading surcharge to the landform, which imparts an additional overburden pressure on the slope and impacts its overall stability. Luckily, these issues can be addressed with engineered solutions, given the diverse portfolio of modern geotechnical advances. For example, pile installation can be used to redistribute the footing foundation pressures deeper down into the landform. Further, drainage infrastructure can be installed to reduce surface runoff. Through catchment and channelization technology, intercepted precipitation can be redirected to the local municipal water system, discharged to the coast or channeled into the ground as artificial infiltration (depending on what is determined the best
  66. 66. ESS 510 DISCUSSIONS AND CONCLUSIONS Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 61 of 118 practice for the structural integrity of the hillslope and the health of the environment). However, artificial infiltration would increase the volume of groundwater, and in some cases, where groundwater becomes perched above zones of reduced permeability, a buildup of hydrostatic pressure here has the tendency to reduce effective normal stresses and introduce subsurface instability and circumstances conducive to subsidence, liquefaction or slope failure. The risk of this situation can be reduced through dewatering, groundwater extraction or other drainage methodologies. All things considered, the most prominent negatives of residential development on this plat have to do with the disruption of natural processes, but these can be reduced or avoided through responsible building practices and common sense. However, there is always an element of unpredictability from Nature that no amount of engineering can prepare humanity for and prevent undesirable events. 6.5 Structural geology at Sandford Point Describe the context of the structures at Sandford Point relative to the tectonic regime in the Puget Lowland. The Puget Sound Lowland lies between the Olympic Peninsula on the west and the Cascadia Range on the east. As early as the Eocene period 50 million years ago, the Cascadia subcontinent docked with the North American Plate and the regional tectonics within the Puget Lowland were borne into its present-day compressional regime. Since the Quaternary period, the Lowland interspace has been occupied, abandoned and reoccupied by numerous glaciations. The glacial and interglacial periods witnessed the mechanism responsible for the diversity of deposits found here. Because compressional tectonism has been onset since the Eocene, superposed by glaciotectonism (glacial overloading) in the Quaternary, we expect to find expressions of strain within some of these deposits, especially older and deeper formations. Fortunately with the regional faulting, in some ideal localities these deeper formations can be thrust up and exposed at the surface. This is purportedly the case for some geologic formations at Sandford Point. A few of us observed evidence for thrust faulting and folding in clay and sand deposits in the north end of the Sandford Point reach. We find these structures to be tectonic in origin because of the relative
  67. 67. ESS 510 DISCUSSIONS AND CONCLUSIONS Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 62 of 118 magnitude and direction of offset of the deformation in the clay with respect to the sand unit. We also conducted a pi-diagram analysis on fold limb orientations and concluded our measured compressional direction (northeast-southwest) was somewhat consistent with the publish orientation (north-south by Sherrod et al. 2004). It seems the evidence we gathered and observations we made on the structures expressed in the Sandford Point bluffs coincides sufficiently with the expectations when considering the regional compressional tectonics of the Puget Lowland. 6.6 Tsunami sands at Discovery Bay In the appropriate geologic setting, anomalous sand deposits in tidal marsh environments are sometimes interpreted to have tsunami origins based on the following 6 characteristics summarized by Williams et al. (2005): 1) Anomalous sand sheets drape or truncate the pre-existing ground surface; 2) Deposits rise and thin landward; 3) Sediment textures fine landward; 4) Deposits contain remains of marine organisms; 5) Some deposits are graded or consist of two or more laminae of coarse and fine-grained (or organic-debris rich) sediment; and, 6) Deposits are equivalent in age to tsunami deposits dated elsewhere in the same region. Based on these criteria and the local geologic record, tsunami sand deposits have substantial relevance to humanity primarily because we can use them to measure the magnitude and recurrence of historical tsunamis. This knowledge is valuable information to coastal inhabitants whom live under the shadow of this ever-present geohazard, because it may be used to forecast or predict the timing of tsunamis associated with earthquakes or submarine landslides, much like ash layers and lava flows can be used to forecast volcanic eruptions. At Discovery Bay, my team completed a total of 2 gouge-cores, each advanced a maximum of 3 meters below existing ground surface and with acceptable averaged total recoveries of 93% and 84% (see Appendix A, field pages 37 to 39). We identified a total of 8 sand units (5 in the first core, and 3 and the second core) that could potentially have tsunami origins. Technically speaking, however, it is presumptuous to classify them as tsunami deposits given the dearth of
  68. 68. ESS 510 DISCUSSIONS AND CONCLUSIONS Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 63 of 118 evidence, particularly their lack of correspondence with the criteria above. Determining the spatial extent of these deposits through good-old traditional stratigraphic correlation and conducting microscope analyses for marine diatoms to constrain the origins of these sands would be a good step forward in the process of proving them sourced from tsunamis. Some remaining un-answered questions: How can we infer magnitude of flood volumes from tsunami deposits? How do submarine sills (from glacial deposits in Puget Sound) affect tsunami wave dynamics as they entire the Puget Sound system?
  69. 69. ESS 510 REFERENCES Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 64 of 118 7.0 REFERENCES Booth, D.B., 1991, Geologic Map of Vashon and Maury Islands, King County, Washington: U.S. Department of the Interior, U.S. Geological Survey, p. 1 – 7. Borden, K.R., and Troost K.G., 2001, Late Pleistocene Stratigraphy in the South-Central Puget Lowland, Pierce County, Washington: Washington State Department of Natural Resources, Washington Division of Geology and Earth Resources, Report of Investigations 33, p. 1 – 33. Dethier, D. P., Pessl, F., Keuler, R. F., Balzarini, M. A., and Pevear, D. R., 1995, Late Wisconsinan glaciomarine deposition and isostatic rebound, northern Puget Lowland, Washington: Geological Society of America Bulletin, v. 107, no. 11, p. 1288-1303. Google Earth V.6.2.2.6613. (May 2013). “Mike Brown Property.” 47°24’42.7”N 122°30’56”W. Eye alt 922 feet. DigitalGlobe 2012. http://www.earth.google.com [June 25, 2014] Heim, K., 1997, Structural Geology Notebook – Backthrusts: http://maps.unomaha.edu/Maher/geo330/sandbox/kirk3.html Hewitt, A. T., and Mosher, D. C., 2001, Late Quaternary stratigraphy and seafloor geology of eastern Juan de Fuca Strait, British Columbia and Washington: Marine Geology, v. 177, no. 3, p. 295-316. Johannessen, J. and A. MacLennan, 2007, Beach and bluffs of Puget Sound, Puget Sound Nearshore Partnership Report No. 2007-04: published by Seattle District, U.S. Army Corps of Engineers, Seattle, Washington. Available at www.pugetsoundnearshore.org. Johnson, S.Y., Blakely, R.J., Stephenson, W.J., Dadisman, S.V., and Fisher, M.A., 2004, Active shortening of the Cascadia forearc and implications for seismic hazards of the Puget Lowland: Tectonics, v. 23, p. 1 – 27. Johnson, S. Y., Potter, C. J., and Armentrout, J. M., 1994, Origin and evolution of the Seattle fault and Seattle basin, Washington: Geology, v. 22, no. 1, p. 71-74. Johnson, S. Y., Potter, C. J., Miller, J. J., Armentrout, J. M., Finn, C., and Weaver, C. S., 1996, The southern Whidbey Island fault: an active structure in the Puget Lowland, Washington: Geological Society of America Bulletin, v. 108, no. 3, p. 334-354. Johnson, S. Y., Dadisman, S. V., Childs, J. R., and Stanley, W. D., 1999, Active tectonics of the Seattle fault and central Puget Sound, Washington—Implications for earthquake hazards: Geological Society of America Bulletin, v. 111, no. 7, p. 1042-1053.
  70. 70. ESS 510 REFERENCES Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 65 of 118 King County, 2013. Vashon-Maury Island water resources - A retrospective of contributions and highlights. Prepared by King County Department of Natural Resources and Parks, Water and Land Resources Division, Science and Technical Support Section. Seattle, WA. December. Mosher, D. C., and Hewitt, A. T., 2004, Late Quaternary deglaciation and sea-level history of eastern Juan de Fuca Strait, Cascadia: Quaternary International, v. 121, no. 1, p. 23-39. Nelson, A.R., Personius, S.F., Sherrod, B.L., Buck, J., Bradley, L-A., Healey II, G., Liberty, L.M., Kelsey, H.M., Witter, R.C., Koehler, R.P., Schermer, E.R., Nemsa, E.S., and Cladouhos, T.T., 2008, Field and laboratory data from an earthquake history study of scarps in the hanging wall of the Tacoma fault, Mason and Pierce Counties, Washington: U.S. Geological Survey Scientific Investigation Map 3060, 3 sheets. Porter, S. C., and 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., Potter, C., Stephenson, W., and Finn, C., 1997, Seismic reflection images beneath Puget Sound, western Washington state: The Puget Lowland thrust sheet hypothesis: Journal of Geophysical Research: Solid Earth (1978–2012), v. 102 (B12), p. 27469-27489. Seilermapsupport. "Where to find the Projection files for Coordinate Systems to use for Trimble GPS Pathfinder Office export?". Seiler Instruments, 7 June 2012. Web. 26 June 2014. <http://seilermapsupport.wordpress.com/2012/06/07/where-to-find-the-projection-files- for-coordinate-systems-to-use-for-trimble-gps-pathfinder-office-export/>. Thorson, R. M., 1980, Ice-sheet glaciation of the Puget Lowland, Washington, during the Vashon Stade (late Pleistocene): Quaternary Research, v. 13, no. 3, p. 303-321. 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. Thorson, R. M., 2000, Glacial tectonics: a deeper perspective: Quaternary Science Reviews, v. 19, no. 14, p. 1391-1398. Washington State Department of Ecology Water Resources Program. "Water Well Logs." Department of Ecology Water Resources., 13 Jan. 2013. Web. 25 June 2014.
  71. 71. ESS 510 REFERENCES Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 66 of 118 "Washington State Geologic Infomation Portal." Department of Natural Resources. Washington State DNR, n.d. Web. <http://www.dnr.wa.gov/ResearchScience/Topics/GeosciencesData/Pages/geology_porta l.aspx>. Williams, H. F., Hutchinson, I., and Nelson, A. R., 2005, Multiple sources for late-Holocene tsunamis at Discovery Bay, Washington State, USA: The Holocene, v. 15, no. 1, p. 60- 73.
  72. 72. ESS 510 TAKE HOME MESSAGES Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 67 of 118 8.0 TAKE HOME MESSAGES 1. Overall, the experiences associated with this field course have impacted me personally and professionally in a positive way. With this experience and the past academic year, I have a refreshed confidence as a professional geologist. Undoubtedly, this confidence is attributed to interactions within the 2nd generation cohort. Our lecturers and professors, especially those with whom I’ve worked most closely, are responsible for this personal growth. We have deepened our friendships and professional rapports to a point that I have no reservations about our collective abilities and my own. 2. Greatly improved my scientific writing and comprehension skills in making quality field observations, winnowing the critical ideas of a lecture and discussion into succinct notes, and drawing detailed diagrams or other graphics. 3. GEM = Garnet, Epidote and Magnetite. Never knew this reference before. Also, it was instructive to have some one-on-one time with Troost and Cheney working at mineralogical identification under the microscope. 4. I was the most accurate estimator of distance, after winning the 100 feet pace-out contest. My secret may be in the practice of counting 2 steps as 1 stride length; I measure using strides instead of paces, so my stride is almost exactly 5 feet. Easier math too. 5. Don’t stress out about field activities not going as planned, but instead maximize on the present opportunity.
  73. 73. ESS 510 APPENDIX A – FIELD NOTES Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 68 of 118
  74. 74. ESS 510 APPENDIX A – FIELD NOTES Robert Cannata Field Methods in Applied Geology II Field Geologic Report July 2014 P a g e | 69 of 118

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