geologic map of the maltby 7.5-minute quadrangle ... 2—fraser glaciation mis 4—possession...
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MIS 2—FRASERGLACIATION
MIS 4—POSSESSIONGLACIATION
MIS 5 AND EARLIERINTERVALS
MIS 3—OLYMPIA NONGLACIAL INTERVAL
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ATER
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CRETACEOUS
JURASSIC
11.700 ±0.099 ka
33.9 ±0.1 Ma
43.4 ±0.4 Ma(this study)
23.03 ±0.05 Ma
27.8 ±0.4 Ma(this study)
145.5 ±4.0 Ma170–74 Ma
CORRELATION OF MAP UNITS
NONGLACIAL UNITS GLACIAL AND NONGLACIAL UNITS, UNDIVIDED
GLACIAL UNITS
PERIODS AND EPOCHS BASED ON USGS FACT SHEET 2010-3059
Vashon ice arrival in map area—likely between 18 and 17.5 ka (Polenz and
others, 2015)
contact not observed
Vashon ice retreat from map area—likely between 16 and 15 ka (Polenz and
others, 2015)
UNCONFORMITY
36–47 Ma(Dragovich and others, 2013)
(Tabor and others, 1993)(Dragovich and others, 2014a)
UNCONFORMITY
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2
1
COMPOSITECOLUMNAR SECTION 1
near High Bridge(sec. 34, T28N R6E)
COMPOSITECOLUMNAR SECTION 2
SR 2(sec. 23, T27N R6E)
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covered
10-28D: >43,500 yrs BP (elev. 21 ft) (Dragovich and others, 2010a,b)
GD7: 67,100 ±3,700 yr (IRSL)62,000 ±3,720 yr (OSL)(elev. 26 ft)
(elev. 81 ft)
GD9: 53,030 ±4,510 yr (IRSL)52,120 ±3,910 yr (OSL)
(elev. 95 ft)
GD8: 34,890 ±2,790 yr (IRSL)27,430 ±2,750 yr (OSL)
(elev. 115 ft)GD5: 28,140–27,810 yr BP
GD10: 21,700 ±1,520 (IRSL)20,890 ±1,775 (OSL)(elev. 133 ft)
(elev. 141 ft)GD1: 21,885–21,615 yr BP
unconformity
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elev. 40 ft
elev. 100 ft
90 ft
GD12: 32,220 ±2,090 yr (IRSL)(elev. 55 ft)
GD3: 27,410–27,140 yr BP(elev. 73 ft)(Snohomish quadrangle)
Snoqualmie River (active channel)
40 ft
83 ft
150 ft
173 ft
elev. 20 ft
elev. 210 ft
25 ft
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CROSS SECTION EXPLANATION
W43
Geologic units too thin to show as polygons at the scale of the cross section.
Bedding form lines—solid where accurate; long dashed where inferred
Water well or boring
Qa
GP1
A A cross section A
Southern Whidbey Island fault
geophysical lineament
Fiddlers Bluff anticline1 mGal interval5 mGal interval
Bouguer anomaly contours
A
A
MALTBY QUADRANGLEMALTBY QUADRANGLE
Seattle Basin
Everett Basin
-95
-90
-85
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-70
-65
-60-55
-50
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GEOPHYSICAL LINEAMENT B
GEOPHYSICAL LINEAMENT A
SB
EB
SBEB
0 2 4 mi
52.5
-276.9-255.3-237.1-225.0-211.6-197.5-186.7-174.3-155.5-133.4-103.4
-4.140.793.3
Magneticanomalies(nanoteslas)
Figure M2. Reduced-to-pole aeromagnetic anomaly imagery is from Richard Blakely (USGS, written commun., 2016). Isostatic gravity anomaly contours are from this study. The Maltby quadrangle boundary is shown in red. Faults within the quadrangle boundary correspond to the Grace and Cottage Lake lineaments of Sherrod and others (2008). The Fiddlers Bluff anticline and geophysical lineaments are from this study (see pamphlet, Geophysical Observations).
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E V E R E T T
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CARNATION
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Marysville
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SOUTHERNWHIDBEY ISLAND
FAULT
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Everett
RM
FZ
Seattle
F B A
M A
M S
Snoqualmie River
Skykomish
River
Snohomish River
Duvall
Snohomish
Woodinville
Monroe
Cathcart
WoodsCreek
K I N G S T O N A R C H
GFFZ
Quaternary depositsHolocene nonglacialPleistocene glacialand nonglacial
Pre-Quaternary sedimentary rocks
MioceneOligocene–EoceneEocene, undifferentiated
Eocene Tukwilla Formation
oil and gas wellA
fault, undivided? ?
syncline
geophysicallineament
anticline
fault, reverse
fault / fold queriedwhere questionable
Igneous rocksEocene rhyolite of Hansen Lake
Eocene volcanic rocks of Mount Persis
Eocene Pilchuck stock and Bald Mountain pluton
Metamorphic rocksCretaceous–Jurassic
estern mélange belt
Geologic structures
0 5 10 mi
Figure M1. Regional geologic map of the Maltby quadrangle. Geologic units are from 1:100,000-scale mapping (WADGER, 2016). Locations of the Seattle Fault and Kingston arch are from 1:250,000-scale mapping (WADGER, 2010). Seattle and Everett basins modified from Pratt and others (1997, plate 1) and Dragovich and others (2015, 2016, fig.1). The westernmost extents of the Monroe fault (MF), Monroe anticline (MA), and Monroe syncline (MS) are simplified from Dragovich and others (2015, fig. 10). The Southern Whidbey Island fault zone traces are simplified from Dragovich and others (2002) and Sherrod and others (2008). Geophysical lineaments (green) and the Fiddlers Bluff anticline (FBA) are from this study. Structures east of the quadrangle are simplified from Tabor and others (1993, 2002) and Dragovich and others, (2007, 2009, 2010a, 2011a, 2012, 2013, 2014a, 2015, 2016). RMFZ, Rattlesnake Mountain fault zone; CF, Carnation fault; EFB, Explorer Falls basin; TCFZ, Tokul Creek fault zone; CCFZ, Cherry Creek fault zone; GFFZ, Granite Falls fault zone; PF, Pilchuck fault. Oil and gas exploration wells are from Washington Geological Survey records: A, Alderwood No. 1; SS, Socal-Schroeder No. 1; K, Kingston No. 1; SW, Socal-Whidbey No. 1; S, Snohomish No. 1; SD, Sol Duc Delfel No. 1; U, unnamed.
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FiddlersBluff
Fr y
el a
nd
s
t r ou
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122°07 3047°52 30
50 00
47 30
47°45 00122°07 30 05 00 02 30 122°00 00
47°45 00
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50 00
47 30
T 28 N
T 27 N
R 5 E R 6 E
T 27 N
T 26 N
T 28 N
T 27 N
R 5 E R 6 E
T 27 N
T 26 N
This geologic map was funded in part by the U.S. Geological Survey National Cooperative Geologic Mapping Program
under USGS award number G16AC00286, 2016–2017.
7000 FEET1000 10000 2000 3000 4000 5000 6000
0.5 1 KILOMETER1 0
0.51 0 1 MILE
SCALE 1:24,000
contour interval 20 feet
APPROXIMATE MEANDECLINATION, 2017
MAG
NET
IC N
OR
TH
TRU
E N
OR
TH
16°
Disclaimer: This product is provided ‘as is’ without warranty of any kind, either expressed or implied, including, but not limited to, the implied warranties of merchantability and fitness for a particular use. The Washington Department of Natural Resources and the authors of this product will not be liable to the user of this product for any activity involving the product with respect to the following: (a) lost profits, lost savings, or any other consequential damages; (b) fitness of the product for a particular purpose; or (c) use of the product or results obtained from use of the product. This product is considered to be exempt from the Geologist Licensing Act [RCW 18.220.190 (4)] because it is draft geological research conducted by or for the State of Washington, Department of Natural Resources, Washington Geological Survey.
Research supported by the U.S. Geological Survey, National Cooperative Geologic Mapping Program, under USGS award number G16AC00286. The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the U.S. Government.
Lambert conformal conic projectionNorth American Datum of 1927; to place on North American Datum of
1983, move the projection lines approximately 26 meters north and 92 meters east as shown by crosshair corner ticks
Base map from scanned and rectified U.S. Geological Survey Maltby 7.5-minute quadrangle, 1981—base map modified to reflect mapped lakes.
Shaded relief generated from a lidar bare-earth digital elevation model (available from the Washington Geological Survey, http://lidarportal.dnr.wa.gov/)
GIS by Mitchell D. Allen and Skyler P. MavorDigital cartography by Daniel E. CoeEditing and production by Jessica L. Czajkowski, Jaretta M. Roloff, and
Daniel E. Coe
WASHINGTON GEOLOGICAL SURVEYMAP SERIES 2017-02
Geologic Map of the Maltby 7.5-minute Quadrangle
Pamphlet accompanies map
Duvall
Maltby
Monroe
Redmond
Bothell
Everett
Cathcart
Snohomish
Woodinville
MALT
BY
MON
ROE
BOTH
ELL
EVER
ETT
KIRK
LAND
REDM
OND
CARN
ATIO
N
SNOH
OMIS
H
LAKE
ROES
IGER
2
405
5
202
9
96
522
203
527
© 2017 Washington Geological Surveyhttp://www.dnr.wa.gov/geology/
Geologic Map of the Maltby 7.5-minute Quadrangle,Snohomish and King Counties, Washington
Mitchell D. Allen, Skyler P. Mavor, Jeffrey H. Tepper, Elizabeth A. Nesbitt,Shannon A. Mahan, Recep Cakir, Bruce A. Stoker, and Megan L. Anderson
October 2017
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MAJOR FINDINGS• Eighteen new geochemical samples and a new ~44 Ma U-Pb date from the volcanic rocks of Mount Persis reflect
signatures of the nascent Cascade arc in the mid-Eocene.
• Refugian-stage foraminiferal and Galvinian-stage molluscan biostratigraphy below a ~28 Ma U-Pb date of interbedded tuff shows that sedimentary rocks are older than previously inferred and record an Eocene or early Oligocene marine transgression.
• Luminescence and finite radiocarbon chronology constrain glacial and nonglacial Quaternary deposits between Marine Isotope Stage 2 (MIS 2), and MIS 4. Results may demark a minimum limiting age for the Possession glaciation.
• A west-northwest tracing bedrock anticline records late Oligocene or younger north-northeast-directed shortening and may connect to other regional structures.
DESCRIPTION OF MAP UNITS(see pamphlet for detailed map unit descriptions)
Quaternary Unconsolidated Deposits
HOLOCENE NONGLACIAL DEPOSITS
Artificial fill—Major road fill placed to elevate the land along road or railways; likely engineered; may include sand, cobbles, pebbles, boulders, silt, clay, organic matter, rip-rap, and concrete, in varied amounts; includes industrial or household waste in landfills.
Modified land—Boulders, cobbles, pebbles, sand, silt, clay, diamicton, and organic matter, in varied amounts; locally derived but redistributed to modify topography; underlying units exposed in some areas.
LATEST PLEISTOCENE TO HOLOCENE NONGLACIAL DEPOSITS
Peat—Organic material and organic-rich sediment; includes peat, gyttja, muck, silt, and clay, with plant or woody debris; rare volcanic ash or pumicite; dark brown or olive-brown; soft; typically wet and may include standing water.
Landslide deposits—Cobbles, pebbles, sand, silt, clay, boulders, and diamicton, in varied amounts; in slide bodies and toes; angular to rounded clasts and grains; unsorted; generally loose, jumbled, and unstratified.
Mass-wasting deposits—Cobbles, pebbles, sand, silt, clay, boulders, and diamicton, in varied amounts; loose; often wet; generally unsorted; shown along potentially or demonstrably unstable slopes; includes colluvium and (or) landslides too small to map separately.
Alluvium—Sand, pebbles, silt, clay, peat, cobbles, and organic material; dark brown to gray; loose; moderately to well sorted; stratified; deposited in flood plains, stream channels, and on terraces.
Alluvial fan deposits—Pebbles, sand, silt, cobbles, and boulders, in varied amounts; typically brown to gray; loose; moderately to poorly sorted; weakly to well stratified; forms gently dipping lobe-shaped surfaces where streams emerge from confining valleys.
PLEISTOCENE GLACIAL AND NONGLACIAL DEPOSITS
Deposits of the Vashon Stade of the Fraser Glaciation
Vashon recessional outwash—Sand and pebble to cobble gravel; some silt and clay; gray to tan where fresh; loose or soft to medium soft; subangular to well-rounded polymict clasts; moderately to well sorted; weakly to well stratified. Locally subdivided into:
Vashon recessional outwash, sand—Sand with silt, rare pebbles, and clay; gray to pale brown where fresh, orange-brown where weathered; sand subangular to subrounded; moderately to well sorted; loose to medium dense; massive to poorly bedded.
Vashon ice-contact deposits—Diamicton (ablation till, flow till, or melt-out till and supraglacial sediment); includes poorly compacted or patchy lodgment till; pale gray, tan, or brown where fresh, orange-brown where weathered; compaction, sorting, and degree of stratification varied; supraglacial, subglacial, or ice-marginal origin; often associated with hummocky or irregular morphology.
Vashon lodgment till—Diamicton; gray to brown; lightly to unweathered; unsorted; unstratified; compact; stiff to very stiff; gravel to very large boulders angular to subrounded and supported in a matrix of sand, silt, and clay.
Vashon advance outwash, undivided—Sand, pebble to cobble gravel, silt, and clay, in varied amounts; blueish gray, brown, or gray to tan; orange-stained where weathered; compact; sand medium dense to dense; mud medium soft to very stiff; clasts typically rounded and moderately sorted; commonly stratified. Locally subdivided into:
Vashon advance outwash, sand—Sand and sparse gravel; pale gray to pale brown; orange-brown where weathered; loose to dense; clasts subangular to subrounded; well sorted; massive to planar-bedded; local thin, planar silt interbeds.
Vashon advance outwash, silt and clay—Silt and clay with sparse gravel; blue-gray to gray-brown where fresh, dark brown where weathered; stiff to hard; well sorted; locally sandy; mostly glaciolacustrine with dropstones; thinly bedded to laminated with rhythmic bedding.
Pre-Vashon Glacial and Nonglacial Deposits
Deposits of the Olympia nonglacial interval (MIS 2–3), sand and silt—Sand and silt with minor clay and gravel; blue-gray to brown-gray where fresh, orange-brown where oxidized, dark brown where organic-rich; very stiff to hard; moderately to very well sorted; micaceous; medium bedded to laminated.
Deposits of the Olympia nonglacial interval (MIS 2–3), gravel—Pebble and cobble gravel in coarse sand matrix, rare small boulders; gray-brown to dark brown, orange-brown where weathered; matrix- to clast-supported; clasts subrounded to rounded; moderately to well sorted; weakly stratified and imbricated.
Pre-Vashon sand—Medium sand; pale brown to light gray where fresh, orange-brown to gray-brown on weathered faces; medium dense to dense; well sorted; massive or thin to medium planar bedded; discontinuous, thin lens-shaped beds of pebbly sand; centimeter-scale ripple bedforms.
Pre-Vashon till—Diamicton; locally sandy; gray, blue-gray, or brown where fresh, orange brown on weathered faces; massive; compact, locally resembles concrete; local shear fabric; polymict clasts. Mapped based on stratigraphic position; poorly exposed.
Pre-Vashon glacial and nonglacial deposits, undivided—Sand, silt, clay, pebble gravel, diamicton, organic debris, and boulders, in varied amounts; color, weathering, rounding, sorting, and bedding varied; compact.
Tertiary Bedrock
Nearshore sedimentary rocks (Oligocene to late Eocene)—Siltstone to coarse-grained sandstone rare pebble conglomerate; brown or gray to dark gray; orange-brown or tan to dark gray on weathered surfaces with hackly concentric weathering pattern; typically tuffaceous and fossiliferous; well lithified to friable; massive to very thickly planar bedded; rare crossbedding. Locally subdivided into:
Tuff (Oligocene)—Coarse rhyolitic crystal vitric (ash) tuff; white to light gray on fresh faces, tan to gray on weathered surfaces; very strongly lithified; massive with local faint stratification; line and point units only.
Continental sedimentary rocks (early Oligocene to Eocene)—Sandstone and pebble and cobble conglomerate, with minor siltstone and shale; tan to brown or gray-brown when fresh, tan to red-brown where weathered; well indurated but locally friable; clasts subrounded; crossbedded and imbricated; terrestrial plant fossils and thin coal stringers common.
Volcanic rocks of Mount Persis of Tabor and others (1993), undivided (mid- to late Eocene)— Andesite and dacite flows, autoclastic breccia, block-and-ash flows, dikes, rare tuff, and volcaniclastic boulder breccia; gray to dark gray; well indurated; fine to coarse grained; massive; columnar jointed. Locally subdivided into:
Dikes—Andesite and dacite dikes around the flanks of Lord Hill; steeply dipping with various orientations; planar to gently undulating; locally glassy with rare andesite xenoliths.
Puget Group, undivided (Eocene)(cross sections only)—Arkosic sandstone, tuffaceous sandstone, tuff, tuff breccia, andesitic conglomerate, and less common siltstone and coal; not exposed in outcrop; inferred from oil and gas wells west of the map area.
Western mélange belt of Frizzell and others (1987), undivided (Cretaceous to Jurassic)(cross sections only)—Metamorphosed argillite, sandstone, chert, pebble conglomerate, tuff, and intermediate to mafic volcanic flows; less common gabbro, diabase, and tonalite; rare marble and ultramafic rocks; not exposed in outcrop or known from subsurface explorations; inferred from geophysical and regional mapping and susbsurface data.
11
A A
GD1
GD25
G3
W50
S2
CS1
GP7
P1
29
57
59
20
16
0
Inclined bedding—showing strike and dip
Horizontal bedding
Approximate orientation of inclined bedding in unconsolidated deposits or bedrock—showing approximate strike and dip
Inclined bedding, where top direction of beds known from local features—showing strike and dip
Small, minor inclined joint—showing strike and dip
Small, minor inclined fault—showing strike and dip
Inclined generic small, minor fold axial surface—showing strike and dip
Inclined slickenline, groove, or striation on fault surface—showing bearing and plunge
Slickenside—showing strike and dip
Inclined flow direction, including sole mark, tool mark, scour mark, flute mark, groove, or channel in sedimentary materials—showing bearing and plunge
Inclined bedding in unconsolidated sedimentary deposits—showing strike and dip
Inclined foreset bedding in unconsolidated sedimentary deposits—showing strike and dip
Inclined flow bands, lamination, layering, or foliation in igneous rock—showing strike and dip
Age site, fossil
Age site, U-Pb, uranium-lead
Age site, 14C, carbon-14
Age site, luminescence (OSL and (or) IRSL)
Geochemistry sample location
Water well
Significant site
Geologic unit too small to show as a polygon at map scale
Location of columnar section (CS)
Geophysical data collection location
Drill hole or test pit
Pollen sample
?
?
?
??
GEOLOGIC SYMBOLS
Contact—Solid where location accurate; long-dashed where approximate; short-dashed where inferred; dotted where concealed; queried where identity or existence questionable
Gradational contact—Identity or existence questionable; location inferred
Fault, unknown offset—inferred; identity or existence questionable
Anticline—Long-dashed where approximate; short-dashed where inferred; dotted where concealed; queried where identity or existence questionable
Geologic unit too thin to show as a polygon—Solid where location accurate; long-dashed where approximate; short-dashed where inferred; dotted where concealed; queried where identity or existence questionable
Dike—Identity or existence certain; Solid where location accurate; long-dashed where approximate; ; short-dashed where inferred; showing dip value and direction
Cross section line
Fluvial terrace—Identity and existence certain, location accurate; hachures point downslope
Landslide scarp—Solid where identity or existence certain; location accurate; hachures on downslope side
Geophysical lineament
Stream—Perrennial where solid; dotted and dashed where intermittent
…vt?
70
8
09-54Z
GD10
5
73
B10
59
…vt
Eip61
0
20
40
60
80
100
120
140
160
48 52 56 60 64 68 72 76 80
Ba/N
b
SiO2 (weight %)
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
48 52 56 60 64 68 72 76 80
K 2O
(wei
ght %
)
SiO2 (weight %)
0
10
20
30
40
50
60
0200800 4006001000
Sr/Y
Sr (ppm)
10
12
14
16
18
20
22
24
48 52 56 60 64 68 72 76 80
Al2O
3 (w
eigh
t %)
SiO2 (weight %)
North Bend
Snoqualmie
Carnation
Monroe
Maltby Lake Joy
Sultan
Miocene–Recent Cascades
Oligocene Cascades
Abstract—No. 387-4 (304000):
We present a new geologic map of the Maltby 7.5-minute quadrangle at 1:24,000 scale. The densely populated quadrangle located 30 km northeast of Seattle, which has not been mapped in detail since the 1980s, spans the projected intersections of several active regional tectonic structures. We support the map with new field work, lidar, existing subsurface explora-tions, geochemistry, palynology, and U-Pb, luminescence, radiocarbon, and biostratigraphic chronology. We compare mapped geology with new iso-static gravity and existing aeromagnetic data for further observations of structural features in this complex area.
New radiocarbon and luminescence chronology constrains pre-Vashon stra-tigraphy of the Olympia non-glacial interval and may provide a limiting date for the end of the Possession Glaciation. New U-Pb zircon ages for both volcanic (~44 Ma) and sedimentary (~28 Ma) bedrock units are pre-sented. Geochemical analyses of 18 samples of the volcanic rocks of Mount Persis range from andesite to dacite and most have adakite affinities.
Skyler P. Mavor—Washington Geological Survey, Department of Natural Resources; Colorado State UniversityMitchell Allen—Forest Practices Division, Washington Geological Survey, Department of Natural ResourcesJeffrey H. Tepper—University of Puget SoundElizbeth A. Nesbitt—Burke Museum, University of WashingtonShannon A. Mahan—U.S. Geological Survey, Denver Federal CenterRecep Cakir—Washington Geological Survey, Department of Natural ResourcesBruce A. Stoker—Earth SystemsM.L. Anderson—Colorado College
GEOLOGIC MAP OF THE MALTBY 7.5-MINUTE QUADRANGLE,SNOHOMISH AND KING COUNTIES, WASHINGTON
We compare these data with existing analyses of the volcanics and discuss a relation to the earliest stages of subduction-related magmatism as the modern Cascade arc initiated in the Eocene. We refine the stratigraphy of fossiliferous Tertiary sedimentary bedrock with constraints from U-Pb zircon chronology, as well as foraminiferal and molluscan biostratigraphy, and de-scribe an Eocene-Oligocene transition from continental to mid-shelf environ-ments with evidence for diffuse methane seep colonies. Biostratigraphy leads us to infer that most of the exposed sedimentary bedrock predates the Blake-ley Formation type section, in contrast to correlations drawn by previous workers. A major bedrock anticline in the map area reflects Oligocene or later NNE-SSW compression and may be tied to a complex interaction of re-gional structures concealed by Quaternary cover. Detailed mapping is unable to further constrain the surficial trace of the active Southern Whidbey Island Fault zone or Monroe Fault, though geophysical lineaments indicate that strands of these structures extend through the quadrangle and merge with previously mapped faults to the southeast. Our new map concludes a de-cade-long campaign of detailed geologic mapping by the Washington Geo-logical Survey in the eastern Puget Lowland.
direction ofmaximum
shortening
3
Rhythmic, planar-bedded silt and clay of unit Qgaf representing cyclical lacustrine sedimentation.
SiO2
K 2O
45 50 55 60 65 70 750
1
2
3
4
5
6
7
Tholeiite
0.05
0.50
5.00
50.00
Sr K Rb Ba Th Ta Nb Ce P Zr Hf Sm Ti Y Yb
Sam
ple
/MO
RB
…vt)
1.0
10.0
100.0
La Ce Pr Nd Sm E Gd Tb Dy Ho Er Tm Yb L
Sam
ple
/MO
RB
…vt)
A M
F
Tholeiite
40 50 60 70 800
5
10
15
Picr
obas
alt Basalt
BasalticDacite
Rhyolite
TrachyteTrachydacite
Basaltic
basalt
Tephrite
tephrite
Foidite
Ultrabasic Basic rmediate Acid
SiO2
Na 2
2O
Deciduous and coniferous terrestrial plant fossils preserved in a detached boulder of unit …Ec.
Luminescence age site GD8 in a 60 cm (24 in.)-thick interbed of well-sorted, fine to coarse sand, with sparse pebbles concentrated along bedding.
Typical weathered exposure of unit …En siltstone and sandstone at age site GD15.
Clast-supported monomict andesitic boulder breccia of unit Evp exposed along the Snohomish River at site S3.
Geochemistry data illustrating the compositional diversity of the volcanic rocks of Mount Persis , including data from nearby Monroe, Carnation, Sultan, Lake Joy, Snoqualmie, and North Bend quadrangles.
Stereonet of poles to bedding measurements from units …Ec and …En across the Fiddlers Bluff anticline (n=38).U-Pb dating results for site GD28 (left) and GD27 (right).
Download the publication
data-point error ellipses are 2
Intercept at43.47 ±0.15 [±0.16] Ma
MSWD = 1.09
238U / 206Pb
207 P
b / 2
06Pb
42444648
0.04
0.05
0.06
0.07
0.08
130 134 138 142 146 150 154 158
A. Kernel density estimate and histograms(Sample GD27)
Num
ber o
f zirc
on g
rain
s
206Pb/238U age (Ma)
Rel
ativ
e pr
obab
ility
0 20 40 60 80 100 120 140 160 180 2000
9
19
28
38
(n=60)
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