2010 michigan academy of science - sedimentary origin and geotechnical properties of subglacial till...
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Sedimentary Origin and Geotechnical Properties of Subglacial Till Ottawa County, Michigan
Patrick M. Colgan and Steve Zdan, Grand Valley State University, Department of Geology
Michigan
Ottawa County
10 kilometers N
StudysiteGrand
Rapids
endmoraine
GVSUCampus
Saugatuck Fm.
Oak Creek Fm.
500 meters
N
1
Lake OntarioHall
2
AdministrationExtension
fine silty sand (lacustrine)
Marshall Sandstone~ 480-510 feet
clay, silt and fine sand (lacustrine)
Section 2South Ravine
Ravine Apartments
ele
vati
on
(ft
)
distance (meters)S N
LakeOntarioHall
vertical exaggeration ~16:1
North to South Cross Section across GVSU Campus
diamicton (basal till)?
NewAdministrationBuilding
diamicton (basal till)
Section 1: Silt-rich diamicton with oxidized vertical joints, striated clasts, high density.
Dm
Sr-Sx
Dms
Section 1: Contact between diamicton and sand. Shear zone between.
clast ofdiamicton
ripplesIn siltysand
Section 1: Clast of reddish diamicton in silty sand.
Section 1 – Ravine Apartments
SC Z
0
1
2
3
meters G
erosional surface
covered
Fl-Fm
SrSx
Fm-Fl
Sx
Fm-Fl
Dm
Sp-Sr
1
2
3
4
5
67a7b8
9
10
11
12
13
sedimentsamples
sedimentfacies
texture
D1D2
GV-1-2 (diamicton - basal till)
0
10
20
30
40
50
60
70
80
90
100
0.0010 0.0100 0.1000 1.0000 10.0000
diameter (mm)
% c
oars
er
sandsilt grclay
GV-2-1 (sandy silt - glaciolacustrine)
0
10
20
30
40
50
60
70
80
90
100
0.0010 0.0100 0.1000 1.0000 10.0000
diameter (mm)
% c
oars
er
sandsilt grclay
GV-2-13 (clayey silt - glaciolacustrine )
0
10
20
30
40
50
60
70
80
90
100
0.0010 0.0100 0.1000 1.0000 10.0000
diameter (mm)
% c
oars
er
sandsilt grclay
D
Sr
Sr
Sr
Fm-Fl
Fm-Fl
Fm-Fl
S1
S2
S3
S4
S6
S5
clast of Dm
Sp
1
2
3
5
6
7
8
9
10
4
covered
Fm-Dm
inclusions of clasts of fines in sand
Fl-Fm
Fl-Fm
Fl-Fm
Dml-Fl
DmmFm-Fl
Fl-Fm
Fl-Fm
St-Sr (A)
St-Sr (A)
St-Sr
St
Sr (A)
St-Sr (A)
St-Sr (A)
St-Sr (A)
St
St
Sr
Sr
Sr
Sr (A)
St-Sr (A)
Sl
Sl
Sl
Samples
7
6
1
18
15
14
12
11
10
16
17
2
3
4
5
9
8
meters
St-Sr (A)
C Z S G D
0
SR2-10 (fine sand)
0
10
20
30
40
50
60
70
80
90
100
0.0010 0.0100 0.1000 1.0000 10.0000
diameter (mm)
% c
oars
er
sandsiltclay gr
SR2-16 (silty clay)
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
90.0
100.0
0.0010 0.0100 0.1000 1.0000 10.0000
diameter (mm)
% c
oars
er
grsandsiltclay
Section 2 – South Ravine
Adapted from Benn and Evans (1998) after Powell and Domack (1995)
rain out of finesilt and clay
underflowsof sand(Sx-Sp-Sr)
depositionof subglacial till (Dm)
debrisflows (Dml)
clay and silt(Fm-Fl)
Morainal bank sedimentation model
Geotechnical Properties of the Saugatuck Formation at GVSU
• Moisture Content (ASTM D2216-98)
• Texture of matrix (hydrometer & sieve)
• Atterberg Limits (ASTM D4318-05)
– Liquid Limit = % moisture
– Plastic Limit = % moisture
– Plasticity Index = LL - PL
• Shear Strength (Torvane Shear Device)
• Standard Penetration Test (ASTM D1586 - 08a)
Color & Field Moisture Content
• Color – Gray (10YR 5/1) to light yellowish brown (10YR 6/4)
• Field Moisture Content (n =33)
Mean = 17.5 %
Standard deviation = 2.1%
Matrix Texture
• Sand 17.3 % s.d. 5.6%
• Silt 46.1% s.d. 3.5%
• Clay 36.6% s.d. 4.2%
Clay
SiltSand
N = 24
0
10
20
30
40
50
60
0 10 20 30 40 50 60 70 80 90 100
Pla
stic
ity
Ind
ex
Liquid Limit
“U” - Line
“A” - Line
CH or OH
CL or OL
CL or ML
5
46
7911
10
MH or OH
Atterberg Limits
Mean Liquid Limit = 27, s.d. 5.5Plasticity Index = 11.5, s.d. 6.5
Comparison to Oak Creek Fm. (Wisconsin)
• Data from Till Pro 1.0 (Wisconsin Natural History and Geologic Survey)
• Texture and Atterberg Limits
– basal till of Oak Creek Formations (n=405)
– All Oak Creek Formation facies (n = 937)
Clay
SiltSand
Clay
SiltSand
Clay
SiltSand
Clay
SiltSand
Clay
SiltSand
GVSUsubglacial till(n = 24)
Oak CreekFormation(n = 937)
Oak Creeksubglacial till(n = 405)
A.
D.C.
GVSUlacustrine(n = 13)
B.
Pla
stic
ity
Ind
ex
Liquid Limit
“U” - Line
“A” - Line
CH or OH
CL or OL
CL or ML MH or OH
0
10
20
30
40
50
60
0 10 20 30 40 50 60 70 80 90 100
Shear Strength of Subglacial Till
• Pocket Penetrometer (n = 44)
– 63 ± 25 kN/m2
• Shear strength of subglacial till (n = 7)
– 59 ± 8 kN/m2
• Standard Penetration Test (n = 45)
– N value = 21.9 ± 6.5 blows
Note: all errors reported are one sigma uncertainty
Clay
SiltSand
Sr-Sp Fl
DmFm
FaciesMeans(n = 4)
Clay
SiltSand
SubglacialtillsMeans(n = 6)
1 2 3
4
5
6
Dm – massive diamicton (basal till)Fm – massive fines (lacustrine)Fl – laminated silt (lacustrine)Sr-Sp – sand riplled and planar bedded
1 - Ganges Till (MI)2 - Glenn Shores Till (MI)3 - Saugatuck Till (Glen Shores MI)4 - Saugatuck Till (GVSU, MI)5 - Oak Creek Till (WI)6 - Wadsworth Till (IL)
Conclusions
• There is both a genetic and textural connection between basal till and lacustrine sediments in the Saugatuck and Oak Creek Formations. This reflects the lacustrine depositional environment of these facies.
• The physical similarities of the Oak Creek and Saugatuck Formations over 100’s of kilometers reflects subglacial mixing processes of lacustrinesediments in the Lake Michigan Basin.
• Geotechnical properties also reflect this similarity of properties over large spatial scales.
Acknowledgements
• Thanks to the GVSU geology students in my GEO380 Special Topics: Engineering Geology class of Fall 2008.