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.