Abstract
The Green Bay and Lake Michigan
lobes of the southern Laurentide Ice Sheet completely covered southern
Sheboygan County during the Last Glacial Maximum, approximately 23,000 to
15,000 radiocarbon years ago.
Initially, the two lobes formed one ice sheet over what would develop
into the Kettle Moraine interlobate area during retreat. West of the Kettle Moraine, the Green Bay
lobe deposited the Horicon Member of the Holy Hill Formation. East of the Kettle Moraine, the Lake
Michigan lobe deposited the New Berlin Member of Holy Hill Formation. A minor readvance punctuated the general ice
retreat and deposited the Waubeka Member of the Holy Hill Formation.
Following ice retreat into the Lake
Michigan basin, the Lake Michigan lobe readvanced several more times into
southern Sheboygan County, while the Green Bay lobe never extended that far
south again. A readvance about 14,000
radiocarbon years ago laid down the silty-clayey till of the Oak Creek
Formation. A subsequent retreat north
of the Straits of Mackinaw allowed for the accumulation of reddish brown lake
sediment in Lake Michigan, which gave the younger Kewaunee Formation its
distinctive reddish brown color. The
Lake Michigan lobe retreated and readvanced several times during the next 1,000
years. Previous interpretations have
suggested there were 2, 3 or 4 advances.
I feel there is insufficient evidence to recognize more than 2 pre-Two
Creeks Kewaunee ice readvances, the Ozaukee and Valders.
I interpret much of the diamicton
associated with these advances as melt out till. Basal freeze-on lenses with sharp contacts suggest a sliding bed
on to which super-cooled water froze.
Subsequent stagnation and melt-out caused little distortion to the
entrained sediment. Model results
suggest that clay-rich melt-out till can form without the occurrence of
dewatering structures and that such structures likely indicate the addition of
outside water to the system. A
reconstructed ice surface profile implies thin ice during the later Lake
Michigan lobe readvances with a similar order of magnitude driving stress as
the adjacent Green Bay lobe. The ice
surface reconstruction supports the surge hypothesis for the Kewaunee readvances,
where thin, fast-moving ice would stack stagnant, debris-rich layers of ice to
produce the thick Kewaunee till found near Lake Michigan.
The Lake Michigan lobe formed
drumlins when ice was at its maximum extent by both erosion of the underlying
sediment and folding due to shear and normal forces. As ice retreated, melt water deposited supraglacial gravel in the
Kettle Moraine, where irregular topography produced by differential surface
melting of ice due to varying thickness of debris cover directed melt water and
debris flow. As ice wasted back from
the Kettle Moraine, outwash accumulated over low points in the drumlin
field. The later readvances that
deposited the Waubeka Member, Oak Creek Formation and the Ozaukee Member
terminated at roughly the same position, stacking debris into a moraine not
particularly associated with any one advance.
The last readvance, the Ozaukee, left only a palimpsest cover of till
near its western terminal position.
Closer to Lake Michigan, thick Ozaukee till in ridges indicate the
presence of retreat moraines.
This thesis would not have been completed
without the help of many individuals and organizations. I would first like to thank the U.S.G.S.
EDMAP program for funding this research.
I would also like to thank the Department of Geology and Geophysics,
UW-Madison for an Alumni Grant, which helped stretch my field season. The Wisconsin Geological and Natural History
Survey were indispensable. They
contributed 3 days of free drilling, topographic maps and well logs and also
helped in compiling my final map. The Sheboygan
County Highway Department and the Northern Kettle Moraine State Forest helped
me with access to various areas of southern Sheboygan County. EarthTech consulting firm, STS Consultants
and BT2 Inc. supplied drill hole and geotechnical data.
On a more personal basis, I would like to
thank my family, especially Sarah-Eva Carlson who helped me for a few days in
the field. Brooke Swanson served
several weeks as my unpaid field assistant and consoler, for which I am truly
grateful. I am also appreciative for my
friends who visited me in the field and saved some of my sanity.
On an academic level, the Quats provided
valuable criticism of my ideas. I thank
Bill Batten and Brian Hess for aid in drilling. The Quat lab workers put in long hours to process my many grain
size samples. Peter Grimm helped me in
processing my radiocarbon date. I
received crucial feedback and criticism from Tom Hooyer on my dewatering
models. I am indebted to Lou Maher for
serving on my advisory committee and reading my thesis. Finally, I would like to thank Dave
Mickelson for advising me these past two years, helping me find a project,
funding and summer housing, and keeping my theories in check.
Table of Contents
Page
Abstract
i
Acknowledgments
.. .. iii
Table of
contents
.. iv
List of Figures
and tables...
... vi
Chapter One:
Introduction
1
Location
2
General Geology
... 6
Early Exploration of Glacial
Deposits
.. 10
Methods
13
Chapter Two:
Surficial Materials
. 18
Gray Compact Silty
Till
.... 18
Holy Hill Formation
. 19
New
Berlin Member
. 19
Undifferentiated
Kettle Moraine Deposits
23
Waubeka
Member
. 23
Oak Creek Formation
24
Kewaunee Formation
25
Ozaukee
Member
.. 25
Discussion
of the Kewaunee Formation till units
. 26
Holocene Deposits
36
Chapter
Three: Basal Till Genesis and Bed Conditions
.. 37
Till Description.
. 38
Holy
Hill Formation
.. 38
Kewaunee
Formation
. 40
Discussion
.. 43
Till
Fabrics
. 43
Methods
. 43
Results
51
Fabric
Discussion
53
Discharge and Dewatering
.. 54
Modeled Hydraulic Gradients and
Effective Pressures...
... 60
Model
Discussion..
. 66
Ice Sheet Surface Profile and
Driving Stress
. 68
Genesis and Bed Conditions
Interpretations: Discussion.
.. 73
Chapter Four:
Landform Genesis
.. 76
Drumlins
. 76
Description.
78
Discussion
. 85
Kettle Moraine
Genesis
. 86
Rolling
Till Surface
...
. 86
Moulin
Kames
88
Inner
low area and adjacent ridges
. 94
Hummocks
and Kettles
..
98
Eskers
101
Outwash
Plains and Ice Retreat
101
Discussion
. 102
Landforms
from Ice Margin recession from the Last Glacial Maximum
..
. 103
New
Berlin Member retreat till deposits..
. 103
New
Berlin Member melt water drainage
. 106
Kewaunee
Formation Moraines.
111
Kewaunee
Formation melt water drainage
113
Chapter Five:
Pleistocene History and Late Wisconsin Deglaciation 114
Wisconsin Glaciation
. 114
Last Glacial Maximum
115
Retreat
from the Kettle Moraine
. 119
Waubeka
Readvance
120
Oak Creek Readvance
. 122
Kewaunee Readvance..
123
Late Pleistocene and Holocene Lake
Michigan Lake levels
.. 125
Holocene Drainage
. 128
Future Work
128
References
. 130
Appendix
A
140
Appendix
B
190
List of Figures, Tables and Plates
Figure Page
1.
Ice Margins
3
2.
Map of Sheboygan County
4
3.
Ice Margins and Physiographic regions in Sheboygan County
. 5
4.
Cartoon cross section of Sheboygan County with bedrock..
. 7
5.
Time-Distance Diagram
. 8
6.
Bedrock Topography
. 15
7.
Pit Location
16
8.
Drill Hole Location
17
9.
Ternary Diagram of older till grain size distribution
. 21
10. Ternary Diagrams of Kewaunee till
grain size distribution
.. 27-28
11. Sand content along Lake Michigan of
Kewaunee till
31
12.
Silt content along Lake Michigan of Kewaunee till..
32
13.
Clay content along Lake Michigan of Kewaunee till
.. 33
14.
Photographs of New Berlin till
. 39
15.
Photographs of Kewaunee till contacts
.. 41
16. Photographs of Kewaunee till
inclusions
. 42
17.
Fabric stereograms
46-47
18.
S1 vs. S3 eigenvalue plot
.
48
19. Benn Fabric Diagram
49
20. Modality Fabric
Diagram
..
50
21. Photographs of clast poor New Berlin
till
. 52
22. Cartoon of seepage
55
23. Cartoon of model
concept
60
24. Graphs of Hydraulic Gradient and
Effective Pressure for Model. 63
25. Graph of additional water needed to
form dewatering structures. 66
26. Ozaukee ice surface contour map and
location of profiles
69
27. Ozaukee ice surface
profiles
70
28. Drumlin orientation
.. 77
29. Drumlin orientation distribution
graph
79
30. Photograph of gravel cored drumlin
bedding at Pit 27
.. 81
31. Photograph of drumlin folds at Pit
77
82
32. Photograph of diapir and fold in a
drumlin at Pit 77.
83
33. Cartoon of folds and stress
distribution at drumlin Pit 77
84
34. Kettle Moraine geomorphic
units
88
35.
Topographic map of northern moulin kame field
89
36. Topographic map of inner low area and
southern moulin kames. 91
37. Photographs of exposures in Garriety
Hill, Pit 11
92
38.
Average roundness
.. 94
39. Melt water flow directions in the
Kettle Moraine
98
40. Ice thickness and cross sections of
the Kettle Moraine
99-100
41. Cartoons of the genesis of the Kettle
Moraine through time
104-105
42. Melt water channel
locations
107
43. Topographic map of Mink Creek ice
marginal channel
108
44.
Topographic map of ice dammed lake (Melius Creek Delta)
. . 109
45. Ozaukee recessional
moraines
.. 113
46. Ice margins and associated flow
directions
.. 117-118
47. Lake Michigan Lake
Levels
. 121
48. Topographic maps of Black River and
Barr Creek
.. 126
Tables
1.
Lithostratigraphic units
9
2.
Grains size averages
.. . 20
3.
Pebble fabric statistics
45
4.
Comparison of basal melt rates
.. 59
5.
Driving stresses of ice sheets and modern glaciers
71
Plates
1.
Surficial Map of southern Sheboygan County
2.
Unconsolidated deposits cross sections