2010 Michigan Academy of Science - Sedimentary Origin and Geotechnical Properties of Subglacial Till Ottawa County, Michigan
1. Sedimentary Origin and Geotechnical
Properties of Subglacial Till
Ottawa County, Michigan
Patrick M. Colgan and Steve Zdan, Grand Valley
State University, Department of Geology
2. Ottawa County
10 kilometers N
Michigan
Study
Grand site
Rapids
5. 1
Administration
Extension
Lake Ontario
Hall
N
2
500 meters
6. North to South Cross Section across GVSU Campus
diamicton Lake New Ravine
(basal till) Ontario Administration Apartments
Hall Building
Section 2
South Ravine
elevation (ft)
fine silty sand (lacustrine)
clay, silt and fine sand (lacustrine)
diamicton (basal till)? Marshall Sandstone
~ 480-510 feet
S distance (meters) N
vertical exaggeration ~16:1
7. Section 1: Silt-rich diamicton with oxidized vertical joints, striated clasts, high density.
8. Dm
Dms
Sr-Sx
Section 1: Contact between diamicton and sand. Shear zone between.
9. clast of
diamicton
ripples
In silty
sand
Section 1: Clast of reddish diamicton in silty sand.
11. meters C Z S G D
Section 2 – South Ravine
0 Fm-Dm Samples
covered
St-Sr (A)
1 Fl-Fm
7
9
SR2-10 (fine sand)
Sr (A)
St-Sr (A) 6
Fl-Fm 8 100
St-Sr (A) 90
5
2 4 clay silt sand gr 80
Sl 70
% coarser
3
60
Sl 2 50
3 St-Sr (A) 1 40
Dml-Fl 18
30
St-Sr (A) 20
Fl-Fm 10
4 Sr
St-Sr (A) 0
Sr 15 0.0010 0.0100 0.1000 1.0000 10.0000
Fl-Fm 14
12 diameter (mm)
5 St-Sr
Fl-Fm
11
SR2-16 (silty clay)
Sr
6 10
St
100.0
90.0
Sl
80.0
7 70.0
% coarser
60.0
clay silt sand gr 50.0
St-Sr (A) 40.0
8 30.0
20.0
St
inclusions of clasts 10.0
of fines in sand 0.0
9 Dmm
Fm-Fl
16 0.0010 0.0100 0.1000 1.0000 10.0000
17 diameter (mm)
Sr (A)
10 St
12. Morainal bank sedimentation model
rain out of fine
silt and clay
underflows
of sand
(Sx-Sp-Sr)
deposition
debris
of subglacial till (Dm) clay and silt
flows (Dml)
(Fm-Fl)
Adapted from Benn and Evans (1998) after Powell and Domack (1995)
13. 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)
14. 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%
16. Atterberg Limits
60
“U” - Line
50
CH or OH
40
Plasticity Index
CL or OL
“A” - Line
30
20 5
CL or ML 4
MH or OH
6
10
97
11
10
0
0 10 20 30 40 50 60 70 80 90 100
Liquid Limit
Mean Liquid Limit = 27, s.d. 5.5
Plasticity Index = 11.5, s.d. 6.5
17. 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)
18. Clay Clay GVSU
A. GVSU B.
subglacial till lacustrine
(n = 24) (n = 13)
Sand Silt Sand Silt
Clay Clay
C. Oak Creek D. Oak Creek
subglacial till Formation
(n = 405) (n = 937)
Sand Silt Sand Silt
19. 60
“U” - Line
50
CH or OH
40
Plasticity Index
CL or OL
“A” - Line
30
20
CL or ML MH or OH
10
0
0 10 20 30 40 50 60 70 80 90 100
Liquid Limit
20. 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
21. Clay Clay
Facies Subglacial
Means tills
(n = 4) Means
(n = 6)
5
Dm 4 6
Fm
1 2 3
Sr-Sp Fl
Sand Silt Sand Silt
Dm – massive diamicton (basal till) 1 - Ganges Till (MI)
Fm – massive fines (lacustrine) 2 - Glenn Shores Till (MI)
Fl – laminated silt (lacustrine) 3 - Saugatuck Till (Glen Shores MI)
Sr-Sp – sand riplled and planar bedded 4 - Saugatuck Till (GVSU, MI)
5 - Oak Creek Till (WI)
6 - Wadsworth Till (IL)
22. 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 lacustrine
sediments in the Lake Michigan Basin.
• Geotechnical properties also reflect this similarity
of properties over large spatial scales.
23. Acknowledgements
• Thanks to the GVSU geology students in my
GEO380 Special Topics: Engineering Geology
class of Fall 2008.