2010 Michigan Academy of Science - Sedimentary Origin and Geotechnical Properties of Subglacial Till Ottawa County, Michigan

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.