Reclassification and Correlation of the Glacial Drifts of Northwestern Iowa and Adjacent Areas

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RECLASSIFICATION AND CORRELATION OF THE GLACIAL DRIFTS OF NORTHWESTERN IOWA AND ADJACENT AREAS

fey R o b e rt ? : Ruhe

A d i s s e r t a t i o n s u b m itte d I n p a r t i a l f u l f i l l m e n t o f th e r e q u ir e m e n ts f o r th e d e g re e o f D o c to r o f P h ilo s o p h y I n th e D ep a rtm en t o f G eo lo g y i n th e G ra d u a te C o lle g e o f th e S t a t e U n i v e r s i t y o f Iow a A u g u st, 1950

ProQuest Number: 10612591

All rights reserv ed INFORMATION TO ALL USERS The quality o f this rep ro d u ctio n is d e p e n d e n t u p o n th e quality o f th e c o p y su b m itted . In th e unlikely e v e n t th a t th e a u th o r did n o t s e n d a c o m p le te m anuscript a n d th e re a re missing p a g e s , th e s e will b e n o te d . Also, if m aterial h a d to b e re m o v e d , a n o te will in d ic a te th e d eletio n .

uest ProQ uest 10612591 Published by P roQ uest LLC (2017). C opyright o f th e Dissertation is held by th e Author. All rights reserv ed . This work is p ro te c te d a g a in st u n authorized co p y in g u n d e r Title 17, United S tates C o d e Microform Edition © ProQ uest LLC. ProQ uest LLC. 789 East Eisenhow er Parkway P.O. Box 1346 Ann Arbor, Ml 48106 - 1346

A0&NOWLETCMENT3 T h is d i s s e r t a t i o n I s th e r e s u l t o f a f i e l d s tu d y o f n o r th w e s te r n Iow a an d a d j a c e n t a r e a s s u p p o r te d by fu n d s o f th e Iow e G e o lo g ic a l S u rv e y .

A p p r e c ia tio n i s e x p r e s s e d

to Dr. H. G a rla n d H e rsh e y , D i r e c t o r o f th e Iow a G e o lo g ic a l S u rv e y , who made p o s s i b l e t h e s tu d y , a c t i v e l y p a r t i c i p a t e d i n f i e l d c o n f e r e n c e s i n th e r e g i o n , and c o n s t r u c t i v e l y c r i t i c i s e d th e w ork o f th e w r i t e r i n th e f i e l d and th e r e p o r t o f th e f i e l d s tu d y . Dr. R ic h a r d F. F l i n t , D e p a rtm e n t o f G eo lo g y , Y ale U n i v e r s i t y , an d th e U. S. G e o lo g ic a l S u rv e y , h a s g e n e r o u s ly g iv e n h i s tim e i n f i e l d c o n f e r e n c e s o f c o r r e ­ l a t i o n i n n o r th w e s te r n Iow a, s o u th w e s te r n M in n e so ta , an d S o u th D ak o ta, an d i n d i s c u s s i o n s and c o rre s p o n d e n c e con­ c e r n in g th e p ro b le m s o f th e r e g i o n a l s tu d y .

A s s o c ia ti o n

w ith D r. F l i n t h a s b e e n s t i m u l a t i n g an d b e n e f i c i a l t o th e w r i t e r i n hiB w ork. Dr. Guy D, S m ith , U. S. D ep artm en t o f A g r i c u l t u r e , D iv is io n o f S o i l S u rv e y , B u reau o f P l a n t I n d u s t r y , S o l i s , and A g r i c u l t u r a l E n g in e e r in g , c o n t r i b u t e d many h e l p f u l s u g g e s tio n s c o n c e r n in g i n t e r p r e t a t i o n s o f P l e i s t o c e n e g e o lo g y and s o i l s o f th e r e g io n . D r. H. E. W rig h t, J r . , D ep artm en t o f G eo lo g y ,

ill

U n i v e r s i t y o f M in n e s o ta , an d M ssrs. &. E* A n d erso n , Iow a G e o lo g ic a l S u rv e y , an d W* H. S e h o lte s , B u rea u o f P l a n t I n d u s t r y , S o i l s , and A g r i c u l t u r a l E n g in e e r in g o f f e r e d many c o n s t r u c t i v e c r i t i c i s m s i n th e f ie ld * The w r i t e r w ish e s to e x p r e s s h i s a p p r e c i a t i o n t© th e p e r s o n n e l o f th e many S o i l C o n s e r v a tio n S e r v ic e and A g r i c u l t u r a l A d ju stm e n t A d m in is tr a tio n o f f i c e s who made a v a i l a b l e f o r s tu d y a e r i a l p h o to g ra p h s o f t h e i r a re a s * The w r i t e r i s in d e b te d to D r. A r th u r C. T ro w b rid g e , D ep a rtm en t o f G eo lo g y , S t a t e U n i v e r s i t y o f Iow a, u n d e r whose s u p e r v i s i o n t h i s r e p o r t was w r i t t e n and who c o n t r i b u t e d much o f hi® tim e i n c o n f e r e n c e s an d d i s c u s s i o n s c o n c e r n in g th e p ro b le m s o f th e s tu d y . Dr* T ro w b rid g e* s c r i t i c i s m s an d s u g g e s tio n s h av e b e e n v e r y h e l p f u l to t h e w r i t e r .

iv

C o n te n ts P age in t r o d u c t io n .........................................................................................

i

SUMMARY O f EARLIER W O R K .............................................................

3

B a i n ..............................................................................................

3

Carman and L e v a r e t t . . ....................................................

5

S m ith an d R i e c k e n ..................................................................

9

PRE-WISCONSIN DRIFTS . ...................................................................... N eb rask an D r i f t ............................................................ R e g io n a l d i s t r i b u t i o n

. . .

. •

11 11

................................

11

t o p o g r a p h y ......................................................................

IS

L l t h o l o g y ......................................................................

13

S t r a t i g r a p h y .................................................................

14

A fto n ia n S o i l . ............................................................

16

K ansan D r i f t

16

* ......................................................................

R e g io n a l d i s t r i b u t i o n

..........................................

T o p o g r a p h y ............................................................ S lo p e s an d r e l i e f .............................................. D ra in a g e

...............................................

L l t h o l o g y ...................................................

16 17 17 IB 19

S t r a t i g r a p h y ............................................................ Y arm outh S o i l an d S e d im e n ts L o v e la n d F o rm a tio n

20

.................................

20

.................................................................

22

V

Page THE IOWAN DRIFT R e g io n a l D i s t r i b u t i o n T o p o g rap h y . . . . .

. . . . . . . .

22

. . . . . . . . . . . .

22

........................................................

A bsence o f end m o ra in e G round m o ra in e

........................

..............................................

.

.

23

24

D r a i n a g e ........................... L lth o lo g y

23

2?

......................................................................

28

T i l l ................................

28

S tra tifie d d r if t

....................................................

30

•

30

THE TAZEWELL D R I F T ......................................................................

33

L o e ss

T o pography

................................

35

End m o ra ln e an d m a rg in a l s l o p e ......................

35

S lo p e s and r e l i e f ...................................................

37

D r a i n a g e .......................

39

C om parison o f Iowan a n d T az e w e ll d r i f t r e g io n s . . . . .

........................

D iv e r s io n o f d r a in a g e l i n e s T rib u ta ry p a t te r n

39

. . . .

41

. . . . . . . . .

42

G & lv a-Id a G rove, Iow a a r e a ......................

42

D ra in a g e o f T a z e w e ll d r i f t r e g io n i n M i n n e s o t a ...............................................

49

n Page L lth o lo g y . . . . . . . . . . . . .

.

©1

. ......................................

51

S t r a t i f i e d d r i f t . . . . . . . ........................

54

L o e s s ............................................................

55

T i l l ................................. ....

L o e ss t h i c k n e s s d i s c o n t i n u i t y a lo n g T azew ell-Iow & n c o n t a c t

.

. .

57

S t r a t i g r a p h y ...........................................................................

59

..........................................

60

S h e ld o n s e c t i o n

P e te r s o n s e c t i o n .......................

67

M ill G reek s e c t i o n ....................................................

71

C herokee s e c t i o n ........................................................

72

Summary o f E v id e n c e f o r T a z e w e ll D r i f t . . . . THE OAKY D R IF T ................................................................................ . Summary o f P r e v io u s Work on Dee M oines

Lohe . .

T o p o g r a p h y ..................................... End m o r a i n e ..................................................................

73 75 75 78 78

D is c o n tin u o u s end m o ra in e s o f low r e l i e f ........................... G round m o rain e D ra in a g e L lth o lo g y

81

........................................................

84

......................................................................

84

...................................................

86

T i l l ....................................................................................

86

S t r a t i f i e d d r i f t ........................................................

87

v li

Page L o e ss . . . . . . . . . . . . . . . . . . S t r a t i g r a p h y ...................................... ........

88

........................

93

P ro b lem of th e C o r r e l a t i o n of th e C ary d r i f t .

94

THE MAKKATO D R IF T ...........................................................................

90

I n t e r p r e t a t i o n o f th e M o rain es o f th e Des M oines L o b e ....................................................... . .

90

T o p o g r a p h y ................................................................................

98

End m o r a i n e s .............................................................

98

R e l a t i o n s h i p o f tr e n d s o f M ankato an d C ary end m o ra in e s M ajo r m o r a ln a l

. .....................

98

b e l t s .............................

102

M u ltip le , d is c o n tin u o u s en d m o ra in e s o f low r e l i e f ............................. 105 G round m o r a i n e ..............................................................107 D r a i n a g e ......................................................................108 L lth o lo g y

..........................................................................

109

T i l l ..................................................................................... 109 S tra tifie d d r if t

....................................................

L o e s s ............................ * ...............................

110 Ill

S t r a t i g r a p h y ................................. * .......................................... 112 INTERSTADlAL S O I L ................................................................................ 112 SUMMARY........................................................................................................117 LITERATURE C I T E D .................................................................................121

v iii

Illu s tra tio n s F ig u r e 1

P age

D r i f t and m o ra in e b o u n d a r ie s o f p r e v io u s w o rk e rs I n n o r th w e s te r n I o w a ................

2

4

B a rg ra p h o f t y p i c a l Iow an an d p o s t Iowan l o s e s .....................................................

3

F re q u e n c y c u r v e s o f d r i f t to p o g r a p h ie s

4

G alv a-X d a G ro v e, Iow a a r e a ...........................

5

T e x tu r e s o f t i l l s

6

A t t e r b e r g L im its o f t i l l s

7

B a rg ra p h o f t y p i c a l T a z e w e ll a n d p o s t -

. . . . . . .

34 . . .

40 44

.........................

52

.......................................

53

T a z e w e ll l o e s s .................................................

56

8

B u rle d s o i l o f S h eld o n s e c t i o n ..............................

9

T e x tu re o f Iow an l o e s s o f S h eld o n s e c t i o n

.

65

10

T e x tu re o f Iow an l o e s s o f P e te r s o n s e c t i o n

.

69

11

T a z e w e ll t i l l o v e r Iowan l o e s s , P e te r s o n s e c t i o n ..............................................................

64

70

12

B a rg ra p h s ©f C ary an d M ankato l o e s s e s

. . .

91

13

S o r tin g o f l o e s s e s .........................................................

92

14

B u rie d s o i l o f P Is g a h r o a d s e c t i o n . . . . .

116

15

U pper t o l l b r id g e s e c t i o n , S io u x C ity

116

. . .

ix Plate 1

Page Glacial Drifts of northwestern Iowa and Adjacent A r e a s .....................

XI

Poeket

Loesses of northwestern Iowa and Adjacent Areas . . . . . . . . . . . . .

Pocket

X

Tables fable

Page

1

Oround-Morain© Types

2

Nomenclature of the Wisconsin Loesses

3

Distal and Proximal Slope Belief of

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Cary Bud Moraine.................... 4

79

Distal and Proximal Slope Belief of Altamont Moraine .....................

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1

RECLASSIFICATION AM# CORRELATION OF THE GLACIAL DRIFTS OF NORTHWESTERN IOWA AMD ADJACENT AREAS INTRODUCTION The a r e a her© d e s c r ib e d em b races a p p r o x im a te ly 1 5 ,0 0 0 s q u a re m ile s I n n o r th w e s te r n Iow a, s o u th w e s te r n M in n e so ta , an d e a s t e r n S o u th D a k o ta . A r e s t u d y o f th e a r e a I n n o r th w e s te r n Iow a, l a s t d e s c r ib e d b y G arm anl, was I n i t i a t e d by th e Iowa G e o lo g ic a l 3* Carman, «*. E . , F u r t h e r s t u d i e s on th e P l e i s t o c e n e g e o lo g y o f n o r th w e s te r n Iow a; Iow a G eo l. S u rv e y , v o l . 56, p p . 15*194, 1 9 3 1 . S u rv e y I n 1948.

R e e x a m in a tio n o f th e a r e a was n e c e s s i ­

t a t e d by th e work o f S m ith an d R le c k e n 2 and th e f i e l d s tu d y 2 S m ith , G> P . , and R ie c k e n , F. F . , The Iow an d r i f t b o r d e r o f n o r th w e s te r n Iow a; Am. J o u r . S e i . , v o l . 246, p p . 706*713, 1947. o f R. F. F l i n t o f th e U. S. G e o lo g ic a l S u rv e y I n p r o g r e s s d u r in g th e summers o f 1946 to 1949 i n S o u th D akota. D e t a i l e d f i e l d s tu d y was c o n d u c te d by th e w r i t e r i n Iow a d u r in g th e summers o f 1948 an d 1949. R e e x a m in a tio n o f th e a r e a o f s o u th w e s te r n

s

M in n e s o ta , l a s t d e s c r ib e d b y L e v e r e t t 3 , was a c c o m p lish e d 3 L e v e r s t t , F ra n k , Q u a te rn a ry g e o lo g y o f M in n e so ta an d p a r t s o f a d j a c e n t s t a t e s : if* S. $ e o l . S u rv e y P ro f* P a p e r 161, 1932* d u r in g a p e r i o d o f t h r e e w eeks I n th e summer o f 1949* The n a t u r e o f th e work I n t h i s a r e a was a s tu d y o f th e to p o g r a p h ic an d l l t h o l o g l c r e l a t i o n s h i p s o f th e g l a c i a l d r i f t s n e c e s s a r y f o r th e c o r r e l a t i o n o f th e d r i f t s o f n o r th w e s te r n Iow a an d e a s t e r n S o u th D ak o ta .

The f i e l d

s tu d y I n M in n e so ta was n o t an d was n o t I n te n d e d to b e d e ta ile d . T h re e m a jo r p ro b le m s w ere I n v o lv e d i n t h i s s tu d y : ( l ) th e i d e n t i t y o f th e d r i f t t h a t Carman and L e v e r e t t b e l i e v e d t o be Iow an, (2 ) r e l a t i o n s h i p s o f th e m o r a ln le sy ste m s o f th e d r i f t o f th e Dea M oines lo b e a l l o f w h ich w ere c o n s id e r e d M ankato i n a g e , an d (3 ) c o r r e l a t i o n o f th e d r i f t s o f n o r th w e s te r n Iow a, s o u th w e s te r n M in n e so ta , and th o s e d r i f t s i n th e p r o c e s s o f s tu d y b y F l i n t I n S o u th D ak o ta.

3

SUMMARY OF EARLIER WORK

B a in I n 189? B a in 3 r e p o r t e d th e o c c u r r e n c e o f Iowan 3 B a in , H. F., R e l a t i o n s o f th e Wisconsin an d

K ansan d r i f t s h e e t s i n c e n t r a l Iow a and r e l a t e d phenom ena! Iow a Gteol. S u r r e y , v o l . 6 , p . 4 65, p i . 2 8 , 1897. d r i f t i n n o r th w e s te r n Iow a. I s g iv e n i n f i g u r e 1»

L o c a tio n o f B a in f s Iowan l i n e

H ow ever, I n 1898 B a in 4 r e l o c a t e d

4 B a in , H. F . , R e p o rt o f th© a s s i s t a n t s t a t e g e o l o g i s t s Iow a G-eol. S u rv e y , v o l . 8 , p p . 2 5 -2 9 , p i . 3, 1898. th© Iow an d r i f t b o r d e r i n Woodbury C o unty, s o u th o f S io u x C i ty , s o u th e a s tw a r d t o Monona C o u n ty th e n e a s tw a r d a lo n g th© n o r t h e r n t i e r o f to w n sh ip s o f Monona an d C raw fo rd C o u n tie s to C a r r o l l i n C a r r o l l C o u n ty , l o c a t i o n s o f th e s e a r e a s . )

(se e p i. I fo r

Bain® acco m p an ied Todd an d

8 B a in , K. F . , R e p o rt o f th e a s s i s t a n t s t a t e g e o l o g i s t : Iow a C e o l. S u rv e y , v o l . 9 , p p . 2 5 -2 ? , 1899. L e v e r e t t I n th e f i e l d i n n o r th w e s te r n Iow a.

As a r e s u l t

o f th e c o n f e r e n c e , B a in c o n c lu d e d t h a t th e d r i f t d e s ig n a te d Iow an I n 1897 an d 1898 c o u ld n o t be c o r r e c t l y c o n s id e r e d

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a s su c h u n t i l f u r t h e r s tu d y h ad b ee n made.

He s u g g e s te d

t h a t t h i s d r i f t may be an an o m alo u s p h a s e o f th e K ansan. I n an y e v e n t, B a in I n 1899 r e t r a c t e d h i s Iow an c l a s s i ­ f i c a t i o n o f th e d r i f t o f n o r th w e s te r n Iow a. Carman and L e v e r e t t Carman b eg a n h i s o r i g i n a l s tu d y o f th e P l e i s t o ­ ce n e g e o lo g y o f n o r th w e s te r n Iowa i n 1 909.

The worh

c o n s i s t e d o f th e t r a c i n g o f th e m a rg in o f th e Dos M oines lo b e n o rth w a rd from C a r r o l l C ounty, Iowa t o th e M in n e so ta s t a t e l i n e an d a s tu d y o f th e a r e a w e s t o f th e Des M oines lo b e .

D u rin g 1910 and 1911, e v id e n c e , c h i e f l y to p o g r a p h ic ,

was r e c o g n iz e d t h a t I n d i c a t e d th e e x i s t e n c e o f a d r i f t I n te r m e d i a te b e tw e e n K ansan an d W isc o n sin .

However, th e

r e g io n was mapped a s Kansan® I n 1913 f o r t h r e e r e a s o n s : ® Map o f Iowa show ing d r i f t sh eet® : Iowa G eo l. S u rv e y , v o l . 94, p i . 83 , 1913. (1 ) a s u p e r K ansan d r i f t s h e e t c o u ld n o t be d e te rm in e d s tra tig ra p h lc a lly ;

( 2 ) th e to p o g ra p h y d id n o t a f f o r d a

d i s t i n c t b o u n d a ry l i n e ;

(3 ) t h i s a r e a was p r o b a b ly c o r ­

r e l a t i v e o f th e Iowan o f n o r t h e a s t e r n Iow a w hich wag I n v o lv e d a t th e tim e I n a c o n tr o v e r s y a s t o I t s tr u e I d e n t i t y and Carman d id n o t w ant to c o m p lic a te t h a t

problem * I n 1912 L e v e r e t t t r a c e d th e b o r d e r o f a d r i f t s h e e t b etw e en th e K ansan and W isc o n sin d r i f t s o f south* w e s te r n M in n e s o ta .

L e w e r e t t’ s m a rg in J o in e d th e m a rg in

o f Carm an1s I n te r m e d i a te d r i f t ( f i e l d s t u d i e s o f 1 9 1 0 -1 1 ) a t th e M in n e so ta s t a t e l i n e i n e a s t e r n Lyon C ounty, Iow a. I n 1915 Carman mapped t h i s d r i f t i n Iowa a s f a r s o u th a s Sac C o u n ty .

Carman b e l i e v e d t h i s d r i f t t o be Iowan an d so

d e s ig n a te d i t i n a m a n u s c r ip t s u b m itte d i n 1915 to Kay, th e n D i r e c t o r o f th e Iowa G e o lo g ic a l S u rv e y . M in n e s o ta , b e l i e v e d th e d r i f t to be W is c o n sin .

L e v e re tt, in B ecau se o f

t h i s l a c k o f a g re e m e n t th e m a n u s c r ip t o f 1915 was f i l e d and th e c o n c lu s io n t h a t th e d r i f t was K ansan was p u b lis h e d by th e Iowa G e o lo g ic a l S u rv e y .1?

L e v e r s t t and S ard eso n m ain*

7 Carm an, J . E . , The P l e i s t o c e n e g e o lo g y o f n o r th w e s te r n Io w a: Iow a G eo l. S u rv e y , v o l. 96, p p . 255* 4 65, 1 9 1 7 . ta i n e d t h e i r o p in io n and mapped th© a r e a a s W is c o n s in .8 & L e v e r e t t , F ra n k , and E a rd e so n , F. W., S u rfa c e f o r m a tio n s and a g r i c u l t u r a l c o n d i tio n s o f th© s o u th h a l f o f M in n e so ta : M in n e so ta C e o l. S u rv ey B u l l . 1 4 , pp. 61*52, map i n j a c k e t , 1 9 1 9 .

?

I n 1922 L e v e re tt® r e v e r s e d M s o p in io n o f 1919 ® L e v e r e t t , F ra n k , G l a c i a l fo rm atio n ® o f th e C o teau d e s P r a i r i e s ( a b s t r a c t ) : G eo l. Soc. A m erica B u l l . , v o l . 3 3 , p . 1 0 1 , 1 922. t h a t th e in te r m e d ia te d r i f t was W isc o n sin and a g re e d e s s e n t i a l l y w ith Carm an ’b I n t e r p r e t a t i o n o f 1916,

However,

i t m u st be k e p t I n m ind t h a t L e v e r e t t q u e s tio n e d th e d e s i g n a t i o n o f th e Iowan a s a s ta g e a t t h i s tim e and u n t i l 1 9 4 2 1 0 q u e s tio n e d th e c l a s s i f i c a t i o n

o f th e Iowan a s th e

10 L e v e r e t t , F ra n k , Hot® by F ra n k L e v e r e t t : J o u r . Gtool*, v o l . 50 , p . 1 0 0 1 -1 0 0 2 , 1942. e a r l i e s t s u b s ta g e o f th e W is c o n s in . I n 1926 L e v e r e t t , Kay, M acO lIn to ck , and A p fe l fo u n d an e x p o s u re n e a r S h eld o n i n O’B r ie n C ounty, Iow a t h a t th e y I n t e r p r e t e d a s s t r a t i g r a p h i c e v id e n c e o f a d r i f t I n te r m e d i a te b etw e en K ansan an d W isco n sin an d w h ich th e y b e l i e v e d showed t h a t th e L o v ela n d l o e s s I n n o r th ­ w e s te r n Iowa was p re-1 o w an i n a g e . T h is s e c t i o n c o n v in c e d Kay o f th e e x i s te n c e o f an I n te r m e d i a te d r i f t i n n o r th w e s te r n Iow a.

Carman was

r e c a l l e d to th e a r e a f o r r e s t u d y i n 1929, b r o u g h t h i s u n p u b lis h e d m a n u s c r ip t o f 1915 up to d a t e ,

s u b m itte d i t

a f o r p u b l i c a t i o n , and I t was so p u b l i s h e d . 3-1 3-1 Carm an, J . K ., F u r th e r s t u d i e s on th© P l e i s t o c e n e g e o lo g y o f n o r th w e s te r n Xowas Iow a O eol. S u rv e y , v o l . 56, p p . 1 6 -1 9 4 , 1 9 5 1 . C anaan, h o w ev er, i n t h i s p a p e r on n o r th w e s te r n Iow a i n t i m a t e d t h a t h i s Iow an b o r d e r s h o u ld hav e b ee n p r o j e c t e d t o th e B ig S io u x H iv e r.

He h ad d i f f i c u l t y i n

e x p l a i n i n g th e to p o g ra p h y an d l l t h o l o g y o f t h i s r e g io n w e r o f h i s Iow an b o r d e r w h ich d i f f e r e d from th e t y p i c a l Kansan o f s o u th w e s te r n Io w a .18

The r e a s o n in g em ployed was a s

18 Carman, J . F . , o p . c i t . p p . 1 0 8 -1 1 1 .

(F u rth e r S tu d ie s ),

f o llo w s : i f th e a l t i t u d e s o f th e K ansan g u m b o til p l a i n l y 13 Kay, O. F . , an d A p fe l, E. T . , The p r e I l l l n o i a n P l e i s t o c e n e g e o lo g y o f Iow a: low- C e o l. B urvey, v o l . 34, p . 261, 1929. r

r

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- T i m m i- m --------- '~r~— r " - ' 1 f i — ■-■ 1 -

t

o f s o u th w e s te r n Iow a w ere p r o j e c t e d n o rth w a rd , t h i s s u r f a c e w ould b e above a l l th e h ig h p o i n t s o f n o r th w e s te r n Iow a,

th e re fo re ,

p re se n t t i l l

i n o r d e r to have e r o s io n o c c u r to th©

s u r f a c e , u p l i f t i n th e n o r th was p o s t u l a t e d .

P e n e p la n a tlo n was n e c e s s a r y t o re lie f.

However, t h i s

d e v e lo p th e a r e a s o f low

c o n c e p t d id n o t e x p l a in th e

fa c t

t h a t th e t i l l u n d e r c a lc a r e o u s l o e s s i s a l s o c a lc a r e o u s .

9

P e n e p l& n a tio n b a d to p r o g r e s s w ith o u t c o n c u r r e n t w e a th e r in g . Carman c o n c lu d e d t h a t th e o r i g i n o f th e s e a r e a s was n o t u n d e r s to o d . An e x p o s u re o f a l o e s s - m a n t l e d c a lc a r e o u s t i l l l o c a t e d w e st o f h i s Iow an b o r d e r n e a r C h ero k ee was e x p la in e d by C arm an si^ Carman, J . E . , op . c i t .

(F u rth e r S tu d ie s ),

p . 129. An a l t e r n a t i v e i n t e r p r e t a t i o n f o r th e f o r e g o in g e x p o s u re i s to e x te n d th e Iowan w e st o f M ill C reek and L i t t l e S io u x r i v e r and make zones 5 and 4 Iow an t i l l . . . . H ow ever, I f th e Iowan i s e x te n d e d w e s t o f L i t t l e S io u x r i v e r a t C herokee, one c a n n o t s e e why i t sh o u ld n o t e x te n d on w est a c r o s s w e s te r n C herokee and P lym outh c o u n t ie s . . . . B u t Carman d id n o t so e x te n d th e Iowan d r i f t . S m ith and B ieck e n I n 194? Guy P. S m ith , S e n io r S o il S c i e n t i s t , U. S. D ep artm en t o f A g r i c u l t u r e , and F ra n k F. R ie c k e n , R e s e a rc h P r o f e s s o r o f S o i l s , Iowa A g r i c u l t u r a l E x p e rim e n t S t a t i o n , r a d i c a l l y r e v i s e d th e Iowan d r i f t b o r d e r i n n o r th w e s te r n Io w a .IB

R e lo c a tio n o f th e b o r d e r was made

S m ith , G. D ., and R ie c k e n , F. F . , Th© Iowan d r i f t b o r d e r o f n o r th w e s te r n Iow a: Am. d o u r . S c i . , v o l . 245, p p . 7 0 6 -7 1 3 , 1947.

10

n e c e s s a r y by t h e i r s o l i s t u d i e s i n t h a t a r e a . T hese a u t h o r s showed th ro u g h t h r e e l i n e s o f e v id e n c e t h a t th© Iow an d r i f t b o r d e r s h o u ld h av e b een mapped e x te n d in g from C a r r o l l C ounty, Iowa n o rth w e stw a rd t o th e B ig S io u x R iv e r a t th e w e s te rn m a rg in o f P ly m o u th C ounty , Iowa ( f i g . 1 ) .

T h e ir e v id e n c e s w ere: (1 ) th e

a b s e n c e o f b u r le d s o i l s I n to p o g r a p h ic p o s i t i o n s t h a t p r e c lu d e s i g n i f i c a n t e r o s io n ; (£ ) an a b r u p t change I n to p o g ra p h y a lo n g a l i n e n o t p r e v i o u s l y r e c o g n iz e d a s a g l a c i a l b o r d e r ; a n d (3 ) an a p p a r e n t d i s c o n t i n u i t y I n l o e s s t e x t u r e and t h i c k n e s s , whose p r e s e n c e r e q u i r e s a p r e v io u s l y u n re c o g n iz e d s o u r c e o f l o e s s . W S m ith , C. D ., an d R ie c k e n , F. F . , lo o . c i t . , p. 707. The S m ith -R ie e k e n l i n e i s I n a g re e m e n t, w ith th e e x c e p tio n o f d e t a i l , w ith B a in f s l i n e o f 1897.

(See f i g .

1. ) D u rin g th e p a s t two y e a r s two f i e l d c o n f e r e n c e s have b e e n c o n d u c te d a lo n g th© Iowan b o r d e r a s r e v i s e d by S m ith an d R ie c k e n .

I n Ju n e 1948 A. C. T ro w b rid g e ,

8 . D. S m ith , S. E. H a r r i s , J r . ,

and th e w r i t e r t r a c e d th e

b o r d e r from C a r r o l l C o unty, Iow a to th e B ig S io u x R iv e r . I n Ju n e 1949 H. C. H e rsh e y , C. D. S m ith , K. E. A nd erso n ,

11

W. H. S c h o lte s , an d th© w r i t e r t r a c e d th e © a s te rn p o r t i o n o f th© b o r d e r I n C a r r o l l , S ac, an d I d a C o u n tie s .

R. F.

F l i n t J o in e d th© c o n f e r e n c e f o r th e t r a c i n g o f th e w e s te rn p a r t o f th e b o r d e r i n P ly m o u th C o unty.

A ll p a r t i c i p a n t s

o f b o th p a r t i e s c o n c u rre d w ith th© i n t e r p r e t a t i o n s o f S m ith an d R ie c k e n . PRE-WISCONSIN DRIFTS

R e lo c a tio n o f th© Iowan d r i f t b o r d e r i n n o r t h ­ w e s te r n Iow a n e c e s s i t a t e s a new d e l i n e a t i o n o f p r e W isc o n sin d r i f t r e g io n s and a r e c l a s s i f i c a t i o n o f th e h o r iz o n s o f p u b lis h e d P l e i s t o c e n e s e c t i o n s .

The p r e -

W isc o n sin d r i f t s an d l o e s s m a n tle d b y W isc o n sin l o e s s c o n s t i t u t e th e s u r f l e i a l d e p o s i t s to th e s o u th o f th e Iow an d r i f t b o r d e r o f S m ith an d R ie c k e n . N eb rask an D r i f t R e g io n a l d i s t r i b u t i o n Kay and A p f e ll? h av e d e s c r ib e d i n d e t a i l th e IT Kay, CL F . , and A p fe l, F . T .f Th© p r e I l l l n o l a n P l e i s t o c e n e g e o lo g y o f Iow a: Iow a G-eol. S u rv ey , v o l . 34 , p p . 1 3 4 -1 8 1 , p i . I I , 1929. N eb rask a n g l a c i a l s ta g e In Iow a.

The d r i f t h a s b een mapped

12

a lo n g th© b o tto m s an d lo w e r w a lls o f th e v a l l e y s o f th e M is s o u r i, L i t t l e S io u x , M aple, S o ld ie r , i n n o r th w e s te r n Iowa*

and B o y er E lv e r s

P re su m a b ly I n t h e s e a r e a s th e

s tre a m s have s t r i p p e d o f f a l l p o s t- N e b r a s k a n m a te r ia ls * A lth o u g h a d e t a i l e d s tu d y was n o t c o n d u c te d a l l a lo n g th e l e n g t h s o f th e s e p r o j e c t i n g f i n g e r s o f N ebraskan d rift,

s tu d y o f t h e i r n o r t h e r l y p o r t i o n s s u g g e s te d t h a t a

r e v i s i o n o f th e m apping was n e c e s s a r y .

F o r exam ple, i n

th e a r e a o f th e b i f u r c a t i n g f i n g e r i n n o r th e r n C herokee C ounty, Iowa th® N eb rask an d r i f t h as been d e l e t e d . p i. I .)

(S ee

M o d if ic a tio n o f th e m apping I n th e I d a G rove,

I d a C ounty, Iow a a r e a was a l s o n e c e s s a r y .

The lo w e r d r i f t

ex p o sed I n th e s e a r e a s i s now b e lie v e d to b e Kansan and i n a l l c a s e s I s m a n tle d by y o u n g er W isco n sin d e p o s i t s .

The

N eb rask an -K an san c o n t a c t o f Kay an d A p fe l h a s b een fo llo w e d i n th e p r e s e n t m apping i n a l l o t h e r a r e a s . T opography The N eb rask a n d r i f t i s m a n tle d In a l l I n t e r f l u v e a r e a s by Kansan d r i f t and o t h e r y o u n g er d e p o s i t s h en ce I t h a s no to p o g r a p h ic e x p r e s s io n .

However, I f th e map o f Kay

and A p fe l i s com pared w ith Lees* to p o g r a p h ic map o f Iow a,I® 18 L e e s , J . K ., A l t i t u d e s In Iow a: Iowa G eo l. S u rv e y , v o l. 32, map I n b a c k , 1927.

13

I t I s a p p a r e n t t h a t t h e s u r f a c e o f th e N eb rask an d r i f t i s assum ed to be a p l a i n s lo p i n g g e n t l y so u th w e stw e rd . R e c e n t stu d y l® h a s shown t h a t l o c a l l y c o n s id e r a b le r e l i e f 19 Ruhe, R. V ., Some n o te s on th e P l e i s t o c e n e g e o lo g y o f S h e lb y C ounty, Iow a: Iowa Acad. S e l. P r o c ., v o l . 55 , p p . 2 8 1 -2 8 6 , 1948. 1 IITL "J

"

" r , i 'r r ............................r

1

1

■

—

............................................

—

...................... .

w K; i

o c c u r s on th e N eb rask an d r i f t s u r f a c e .

The v a l i d i t y o f th e

m apping o f th e N eb rask an -K an san c o n t a c t o f Kay and A p fel I s t h e r e f o r e c o n s id e r e d t o b e q u e s tio n a b l e and r e q u i r e s d e t a i l e d r e s tu d y . L lth o lo g y The l l t h o l o g y o f th e N eb rask an d r i f t h a s b een d e s c r ib e d b y Kay and

Apfel. SO F our p h a s e s w ere r e c o g n iz e d :

20 Kay, &. F . ,

and A p fe l, E, T . , op. o l t . , p p .

1 6 2 -1 7 9 . (1 ) g u m b o til,

(2 ) o x id is e d an d le a c h e d d r i f t ,

(3 ) o x id iz e d

and u n le a c h e d d r i f t , an d (4) u n o x ld lz e d and u n le a c h e d d r i f t , d u m b o til21 i s r e c o g n iz e d a s th e end s ta g e o f t h e w e a th e rin g 21 Kay, 0 . F . , and P e a r c e , J . N ., The o r i g i n o f g u m b o til: J o u r . G eo lo g y , v o l. 28, pp . 8 9 -1 2 5 , 1920.

14

of t i l l ,

L e ig h to n and M & cO llntock^S showed th e r e l a t i o n s h i p

22 L e ig h to n , M. M ., and M a c C lin to c k , P a u l, W eath ered zo n es o f th© d r i f t s h e e t s o f I l l i n o i s : J o u r . G eology, v o l. 38, p p . 2 8 -5 3 , 1030. o f to p o g ra p h y to th e ty p e o f w e a th e re d t i l l d e r iv e d .

Th©

w r i te r 2 3 d e m o n s tra te d t h a t t h e c o n c e p t o f L e ig h to n and 23 Huhe, R. V ., o p . e i t , , p a s s im . M a eC lin to e k I s a p p l i c a b l e to th e N eb rask an d r i f t In s o u th ­ w e s te rn Iow a. The d e g re e o f w e a th e r in g an d th e th ic k n e s s o f th e w e a th e re d son© d e v e lo p e d i n a t i l l a r e Im p o rta n t c r i t e r i a f o r th e d e l i n e a t i o n o f b r e a k s In th e g l a c i a l se q u en ce In n o r th w e s te r n Iow a. tills

a r e c a lc a r e o u s to th© to p .

I n v a r i a b l y th© W isco n sin I f a h ig h ly w e a th e re d

t i l l 1 b fo u n d b u r i e d i n a s e c t i o n o r e x p o se d a t th e s u r f a c e , i t may b e c l a s s i f i e d a s p re -W is c o n s in .

I t can be

d e s ig n a te d N eb rask an o n ly i f o v e r l a i n by a n o th e r d r i f t t h a t h a s a co m p arab le w e a th e re d zone a t i t s

to p .

S tra tig ra p h y I d a d ro v e s e c t i o n . The o n ly e x p o s u re o f t i l l o b s e rv e d in n o r th w e s te r n Iow a o f N eb rask an ag e I s l o c a t e d I n ro a d c u t s i n th© NKi

s e c . 4 and NWJ SWj s e c . 3, T .8 7 N ., R.40W .,

15

I d a C ounty, Iow a.

On th e w e st a id e o f th e ro a d a r e ex p o sed :

4.

Y e llo w ish -b ro w n , le a c h e d , w e l l - s o r t e d l o e s s ( W is c o n s in ). 3. Y e llo w is h -b ro w n , le a c h e d , p e b b ly t i l l (Kansan)# 2. D ark g r a y , le a c h e d , co m p act, p l a s t i c gum boti 1 , w ith s i l i c e o u s p e b b le s ; s e c o n d a ry c a r b o n a te a lo n g J o i n t s (A fto n la n ). 1 . Y e llo w is h - g r a y , c a lc a r e o u s , p e b b ly t i l l ; s e c o n d a ry c a r b o n a te alo n g J o in t s ( N e b ra s k a n ) .

T h ic k n e ss (In c h e s) 24 22 4?

IB

On th e e a s t s id e o f th e ro a d th e fo llo w in g s e c t i o n i s ex p o se d :

8. Y e llo w is h - b u f f , c a lc a r e o u s , w e l l - s o r t e d l o e s s (W is c o n s in ). 5 . G ray , c a lc a r e o u s , w e l l - s o r t e d l o e s s ( W is c o n s in ) . 4 , G ray , le a c h e d , w e l l - s o r t e d l o e s s ( W is c o n s in ) . 3 . R e d d ish -b ro w n , le a c h e d , w e l l s o r t e d , h e a v y - t e x tu r e d l o e s s ( p r o b a b ly L o v e la n d ). 2 . Y e llo w ish -b ro w n , p e b b ly , le a c h e d t i l l (K a n sa n ). X* Y e llo w ish -b ro w n , p e b b ly , c a lc a r e o u s t i l l (K a n sa n ).

T h ic k n e s s ( in c h e s ) 65 18 8 29 24 72

The gumbo t i l o u tc r o p s on th e e a s t s id e o f th e ro a d downs lo p e t o th e s o u th .

These s e c t i o n s a r e l o c a t e d ab o u t

h a l f a m ile s o u t h e a s t o f th e m a rg in o f th e Iowan d r i f t .

16

A ftonl& n S o l i Many o c c u r r e n c e s o f g u m b o til, p e a t , muck, s o i l s , and w e a th e re d sa n d and g r a v e l r e p r e s e n t i n g A fto n ia n tim e have b e e n d e s c r ib e d I n Iow a24# some o f them i n n o r t h 24 Kay, G. F . , and A p fe l, E. T ., o p . c l t . , p p . 182—183. w e s te r n Iow a, b u t th e o n ly one t h a t c a n n o t be o th e rw is e c l a s s i f i e d i s th e gumbo t i l o f th e s e c t i o n d e s c r ib e d on page 16. Kansan D r i f t R e g io n a l d i s t r i b u t i o n A m a jo r r e v i s i o n o f th e r e g i o n a l dls t r l b u t i o n o f Kansan d r i f t i n n o r th w e s te r n Iow a a s mapped by Kay and Graham27 was made n e c e s s r y by th e r e l o c a t i o n o f th e Iowan Kay, 0 . F . , and Graham, J . B ., The I l l i n o i a n and p o s t- X llin o i& n P l e i s t o c e n e g e o lo g y o f lowas Iowa G eo l. S u rv e y , v o l . 38, p . 1 6 , 1 943. d r i f t b o r d e r by S m ith and R ie c k e n . K ansan d r i f t i s shown on p l a t e I .

The d i s t r i b u t i o n o f th e

i

17

T opography The Kansan d r i f t r e g i o n i n Iowa e x h i b i t s two d i s t i n c t ty p e s o f to p o g r a p h i c e x p r e s s io n s © which a r e :

(1)

Kay,

98, Lash^cr*

KAHiSA *A*S* nO£0°

A O tw k

LE1GEND

7 -8 6 N

C a r m a n ' s l o w a n - K a n s a n c o n t a c t , 1931 • • • • *«Sm1 1 h-R i e c k e n l o w a n - K a n s a n c o n t a c t I9 4 7 Outwash-aI Iuviumj t i l t c o n t a c t ooooo|ow an-K ansan c o n ta c t, corrected — °— T a z e w e I I - t f o n t f a n c o n t a c t kansan I n l i e r or r e e n t r a n t • 8 2L B o r i n g ; 8 2 I n c h e s o f l o e s s o v e r c a 1c a r e o u s t i l l B ase map; Iowa Highway Comm., Ida Co. j I owa } I 9 4 4 ; s e a I e, \ i n .= I m i. *

F ig *

4 * G a lv a -Id a

G ro v e,

Iow a

area#

45

to w n sh ip th e a r e a i s m a tu r e ly d i s s e c t e d .

S lo p e s v a r y from

20 t o 40 p e r c e n t and r e l i e f from a p p r o x im a te ly 100 t o 120 fe e t,

T h is ‘‘r o l l e r - c o a s t e r #

ty p e te r m i n a te s a b r u p t l y a t

th e e a s t e r n m arg in o f th e s o u th e rn l o b a t l o n o f th e H o ls te in Iow an d r i f t - l o b e . N o rth o f th e l i n e d e l i n e a t e d a b o v e , th e to p o ­ g ra p h y I s m ore su b d u ed I n th e e a s t - w e s t tr e n d i n g I n t e r f l u v e u p la n d s .

I n th e s e u p la n d area© t h e r e I s no a p p r e c ia b l e

to p o g r a p h ic change from th e u p la n d s h o u ld e r o f M aple E lv e r w estw ard i n t o t h e H o l s t e i n d r i f t lo b e .

Slope© ra n g e fro©

3 to 6 p e r c e n t and r e l i e f from 40 to 60 f e e t . b a s is o f th is

On th e

to p o g ra p h ic e v id e n c e and th e l i t h o l o g y n o te d

above t h i s a r e a ha® b e e n I n c lu d e d by th e w r i t e r i n th e H o l s t e i n Iowan d r l f t - l o b e .

The l i n e o f d e m a rk a tio n i s

th e l o c a l l y r e l o c a t e d Iowan d r i f t b o r d e r . N o rth o f th e e a s t - w e s t c e n t e r l i n e o f s e c . 24, T .8 8 N ., R .40 W. th e to p o g r a p h ie s on th e w e s t an d e a s t s id e s o f M aple R iv e r ©ay b e co m pared.

Th©? u p la n d e a s t o f M aple

R iv e r d i f f e r s s l i g h t l y fro © th e c o r r e s p o n d in g a r e a w e st o f th e r i v e r w here s lo p e s ra n g e up t o 6 p e r c e n t and r e l i e f from 20 to 40 f e e t . d e c id e d ly d i f f e r e n t .

H ow ever, th e v a l l e y s lo p e s a r e The w e st v a l l e y ©lope I s n o tc h e d and

c u t b y e a s t flo w in g t r i b u t a r i e s o f M aple R iv e r t h a t h ead o n ly a few m ile s to th e w e s t i n t h e H o l s t e i n Iow an lo b e .

46

Slope® a lo n g M aple E lv e r an d a lo n g th e t r i b u t a r i e s v r y from 16 t o 40 p e r c e n t and r e l i e f from 60 to 100 f e e t .

The

to p o g ra p h y o f t h i s l o c a l a r e a i s a p se u d o -K an san ty p e ; i t lo o k s l i k e K ansan b u t th e u p la n d s b etw e en th e t r i b u ­ t a r i e s g ra d e i n t o th e H o l s t e i n Iow an d r i f t - l o b e . The u n d le s e o te d e a s t v a l l e y slop© o f M aple R iv e r i s lo n g and g e n t l e from th e u p la n d s h o u ld e r to th e b o tto m ­ la n d .

W est f lo w in g t r i b u t a r i e s o f M aple R iv e r flo w th ro u g h

o u tw a s h -a g g ra d e d , s h a llo w v a l l e y s .

V a lle y s lo p e s a lo n g

M aple R iv e r and I t s t r i b u t a r i e s a r e a p p ro x im a te ly 6 p e r ­ c e n t an d r e l i e f i s 20 t o 40 f e e t . S o u th w ard from th e e a s t - w e s t c e n t e r l i n e o f s e c . 25, T .8 8 R ., R.40W. two d i s t i n c t to p o g r a p h ie s a r e a g a in e v id e n t.

I n th e a r e a s l a b e l l e d K ansan ( f i g . 4) s lo p e s

ra n g e from 20 to 40 p e r c e n t and r e l i e f v a r i e s from 50 to 100 f e e t .

I n th e a r e a s a lo n g B u f f a lo , E lk , an d O d e b o lt

C ree k s s lo p e s ra n g e from 3 t o 6 p e r c e n t and r e l i e f from 20 t o 40 f e e t .

L lth o lo g io d if fe re n c e s a ls o e x i s t .

In

th e K ansan a r e a s l o e s s o f e s tim a te d th ic k n e s s o f 200 o r more In c h e s o c c u r s .

P l o t t e d b o r in g s i n th e o t h e r a r e a s

d e n o te t h e i r l i t h o l o g i e s . A d i s t i n c t change i n tr e n d o f Maple R iv e r v a l l e y 1 b e v i d e n t a t I d a G rove.

Downstream from Id a G rove, Maple

R iv e r flo w s to th e s o u th w e s t and th e r e p a r a l l e l s a l l th e

4?

m a jo r s tre a m s o f n o r th w e s te r n Iow a.

(S e e p i . I . )

However,

u p s tre a m th e v a l l e y trend® a p p r o x im a te ly n o r th and s o u th . The change i n t r e n d a t I d a d ro v e I s n e a r l y a r i g h t a n g le . N o rth o f I d a d ro v e , M aple R iv e r p a r a l l e l s B a t t l e C re e k , th e m a jo r d r a in a g e l i n e o f th e H o l s t e i n Iowan d r i f t - l o b e . (S ee f i g . 4 . )

B a t t l e C reek h e a d s o n ly 11 m ile s n o r th o f

i t s J u n c tu r e w ith M aple R iv e r .

M aple R iv e r , h o w ev er, h e a d s

35 m ile s n o r t h o f I d a d ro v e I n n o r t h e a s t e r n C herokee C ounty. I n summary, t h r e e m a jo r a n o m a lie s e x i s t i n t h i s a re a :

(1 ) th e l i t h o l o g y o f th e r e e n t r a n t I s n o t c o m p a tib le

w ith th e l i t h o l o g y o f th e K ansan d r i f t r e g io n , (2 ) th e to p o g r a p h ie s , b o th u p la n d an d v a l l e y s lo p e , on th e w e st and e a s t s id e o f Maple R iv e r a r e n o t c o m p a tib le , and (3 ) M aple R iv e r n o r t h o f Id a 0-rove d o es n o t p a r a l l e l th e tr e n d o f th e o t h e r m a jo r s tre a m s o f th e Iowan d r i f t r e g io n o f n o r th w e s te r n Iow a an d i s o f a g r e a t e r m a g n itu d e o f d ev e lo p m e n t th a n a d j a c e n t p a r a l l e l s tre a m s o f th e H o ls te in Iow an d r i f t - l o b e . On th e b a s i s o f l i t h o l o g y th e r e e n t r a n t a r e a i s r e c l a s s i f i e d a s W isco n sin r a t h e r th a n K ansan.

However,

i f th e d r i f t s on th e e a s t and w e st s i d e s o f M aple R iv e r a r e c o n s id e r e d to b e Iowan th e n th e d i f f e r e n c e s I n to p o ­ g ra p h y , th e change I n t r e n d an d th e stag© o f d ev elo p m en t

48

©f M aple R iv e r a r e d i f f i c u l t ! to e x p l a i n .

I f th e a s s u m p tio n

i s made t h a t Iow an i c e r e c e d e d from t h e w e s te rn m a rg in o f th e H o l s t e i n d rift-* lo b © t o a p o s i t i o n a lo n g th e e a s t s id e o f M aple R iv e r an d became s ta g n a n t th e n why d id n o t th e s m a lle r B u f f a lo , I l k , a n d Ode b o l t lo b e s a l s o show e v id e n c e o f re c e s s io n ,

C om parable l o b a t i o n s o f th e H o l s t e i n lo b e

a n d th e H o l s t e i n lo b e i t s e l f w ould h av e u n d erg o n e co m p le te w a sta g e w h ile th e t h r e e l o b a t i o n s m e n tio n e d above re m a in e d I n p l a c e to em plaoe and d i v e r t th e c o u r s e o f M aple l i v e r a t I d a d ro v e . A more l o g i c a l e x p l a n a t i o n I s t h a t a p o s t-Io w a n i c e m ass ad v a n c e d from th e n o r t h e a s t p r o b a b ly a lo n g th e u p p e r r e a c h e s o f p r e g l a c i a l M aple E lv e r t o th e s it© o f I d a d ro v e .

M aple E lv e r was d i v e r t e d t o I t s p r e s e n t c o u rs e

n o r th o f I d a d r o v e .

M e lt w a te r s o f th e y o u n g er i c e mass

p r o b a b ly u t i l i z e d th e low o f a fo rm e r t r i b u t a r y to th e m ain s tre a m h e n c e th e p a r a l l e l i s m o f u p p e r M aple R iv e r and B a t t l e C reek .

The g r e a t e r s u p p ly o f w a te r e x p l a in s th e

d i f f e r e n c e i n m a g n itu d e b etw een M aple R iv e r an d B a t t l e C reek and th e c o n c e n t r a t i o n o f o u tw ash i n th e M aple E lv e r v a lle y .

Im pingem ent o f th e lc e ~ m a rg in a l s tre a m a g a i n s t

th e w e st v a l l e y s lo p e r e s u l t e d in i t s c u t t i n g and r e s u l t a n t s te e p e n in g .

D e p o s itio n o f d r i f t on th e e a s t s id e o f Maple

R iv e r r e s u l t e d i n c o n s t r u c t i o n o f th e g e n t l y s lo p in g d r i f t

49

v en e er*

S m a lle r l e e lo b e s m ig r a te d a ro u n d K ansan h ig h s ,

c o m p le te ly I s o l a t e d th e i n l l e r b etw een B u f f a lo and E lk G re e k s, and d e p o s ite d c a lc a r e o u s t i l l w ith in h a l f a m ile n o r t h e a s t an d one m ile s o u th e a s t o f I d a G rove, A f t e r d e g la e i& tlo n th e s t e e p e r g r a d i e n t on th e w e st v a l l e y s lo p e o f Maple R iv e r p e r m it te d d i s s e c t i o n to d e v e lo p th e p se u d o -K an san ty p e to p o g ra p h y w h ile th e e a s t v a l l e y s lo p e was o n ly s l i g h t l y m o d ifie d . D ra in a g e o f T a z e w e ll d r i f t r e g io n i n M in n e so ta . T ren d o f th e d r a in a g e l i n e s on th e T a z e w e ll d r i f t i n s o u th w e s te rn M in n e so ta I s s o u th w e s t to w a rd th e B ig S io u x R iv e r .

B ed rock

s t r u c t u r e e x e r t s a d e f i n i t e c o n t r o l on th e d r a in a g e o f t h i s r e g io n , f o r th e T a z e w e ll d r i f t I s s i t u a t e d on th e w e s te rn f l a n k o f th e O o teau d es P r a i r i e s .

Upham4 ^ l o c a t e d th e

43 tlpham, W arren, I n G eology o f M in n e so ta : M in n e so ta G e o l. an d M at. H is to r y S u rv ey , v o l . 1 , p . 520, 1S64. c r e s t o f th e O oteau i n R o b les C ounty, th e n c e n o rth w a rd th ro u g h M urray, P ip e s to n e , an d L in c o ln C o u n tie s , M in n e so ta and n o te d t h a t th e w e s te rn o f th e te r m in a l m o ra in e s o f th e Des M oines lo b e was s i t u a t e d on th e c r e s t .

The te r m in a l

m o ra in e d e s c r ib e d b y Uphara m arks th e I n n e r m arg in o f th e T a z e w e ll d r i f t r e g io n i n s o u th w e s te rn M in n e so ta .

60

Thielhas

d e s c r i b e d th e O oteau d e s P r a i r i e s a s

** T h i e l , 0 . A ., The g e o lo g y an d u n d e rg ro u n d w a te r s o f s o u th e r n M in n e s o ta : M in n e so ta (tool* S u rv ey B u ll. 3 1 , p . 55 , 1 9 4 4 . a l i n e a r u p la n d t h a t e x te n d s from th e n o r t h e a s t e r n p a r t o f S o u th D akota s o u th e a s tw a rd i n t o n o r th w e s te r n Iow a. s t r u c t u r e o f th e O oteau I s n o t known.

T rue

S io u x q u a r t z i t e w hich

c o n s t i t u t e s th e b e d ro c k i s known to r i s e 200 to 500 f e e t above th e s u r ro u n d in g C r e ta c e o u s b e d s .

The im p o rta n c e o f

t h i s f e a t u r e from th e s t a n d p o i n t o f g l a c i a l g e o lo g y h a s lo n g b e e n r e c o g n i s e d .

The r i d g e was o f su c h r e l i e f and

mass t h a t I t was a b le t o s p l i t th e T a z e w e ll and l a t e r W isco n sin I c e s h e e ts an d c a u s e i c e lo b e s to ad v an ce so u th ­ w ard i n t o S o u th D akota a lo n g th e Jam es E lv e r low an d s o u th ­ e a s tw a r d i n t o M in n e so ta and Iow a a lo n g th e M in n e so ta an d Dee M oines E lv e r s lo w . I n s o u th w e s te r n M in n e so ta th e e f f e c t o f th e C oteau on th e Iow an an d T a z e w e ll i c e s h e e ts i s p a r t i c u l a r l y e v i d e n t when one c o n s id e r s th e r e g i o n a l d i s t r i b u t i o n o f th e s e two d r i f t s .

The Iow an i c e was t h i c k enough to r i d e

o v e r th e r i d g e an d c o n s t r u c t th e d r i f t s h e e t o f e a s t e r n S o u th D ak o ta, s o u th w e s te r n M in n e so ta , a n d n o r th w e s te r n Iow a.

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so u th w a rd a n d w estw a rd a s d id th e Xow&n.

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c r e s t o f th e C o te a u d e s P r a i r i e s , h u t extended only a few te n s o f m ile s down th e w e s te r n f la n k . P o s tg la c ia l f lu v ia l a c tiv i ty has re s u lte d in co m p le te d r a in a g e o f t h i s r e g i o n i n s o u th w e s te r n M in n e so ta . S tre am s flo w s o u th w e s te r ly down th e d r i f t * and l o e s s m a n tle d w e s te r n f l a n k o f th e C o teau d es P r a i r i e s . lith o lo g y T ill The T a z e w e ll t i l l p o s s e s s e s th e same c h a r a c t e r ­ i s t i c s a s th e Iowan t i l l d e s c r ib e d on p a g e s 2 8 -3 0 . two t i l l s p o s s e s s a p p r o x im a te ly th e same t e x t u r e . f i g . 5 .)

The (Bee

B o il e n g in e e r in g t e s t s , A tte r b e r g l i m i t s a s

m o d ifie d b y C a s a g ra a d e ,4 8 a l s o f a i l e d to show an y 48 C a sa g ra n d e , A r th u r , R e se a rc h on th e A tte r b e r g l i m i t s o f s o i l s : P u b lic H oads, v o l. 13, n o . 8 , p p . 1 2 1 130, 1 9 3 2 . s ig n if ic a n t d iffe re n c e .

(Bee f i g . 8 . )

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The p e b b le la g - c o n c e n tr a t© o r c a lc a r e o u s

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S tra tifie d d r if t A ll s t r a t i f i e d d r i f t i n th e T az e w e ll r e g io n hag b ee n mapped a s u n d i f f e r e n t i a t e d in co n fo rm an ce t o th e g e n e r a l m apping m ethod i n th e w r i t e r ’ s r e g io n o f study* H ow ever, i n s p e c i f i c a r e a s T a z e w e ll o u tw ash was d i f f e r e n t i ­ a te d .

M aple R iv e r T a l l e y n o r th o f I d a d ro v e , Iow a, M ill

C reek T a l l e y i n O’B r ie n mud C herokee C o u n tie s , Iow a, and O t t e r C reek T a l l e y i n O sc e o la and Lyon C o u n tie s , Iowa c o n t a in u n d o u b te d T a z e w e ll o u tw ash .

T h ese stre a m s do n o t

h e a d I n y o u n g e r d r i f t r e g io n s so t h a t t h e r e h a s b e e n no c o n ta m in a tio n .

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I n n o r th w e s te r n Iowa an d s o u th w e s te rn M in n eso ta c a r r i e d o u tw ash from m ore th a n one o f th e W isc o n sin g l a c i e r s . An I m p o r ta n t c r i t e r i o n f o r th e d e l i n e a t i o n o f th e T a z e w e ll d r i f t r e g io n i s th e m a rg in a l o utw ash p a t t e r n . W ith th e e x c e p tio n o f s m a ll l o c a l a r e a s th e T az ew ell r e g io n from I d a & rove, I d a C ounty, to L i t t l e Rock, Lyon C ounty, Iow a i s m arg in ed b y v a l l e y t r a i n s . I n M in n e so ta w e ll d e f in e d o u tw ash a p ro n s o c c u r a lo n g th e T a z e w e ll b o r d e r i n T ps. 103 and 104 H. a lo n g th e Rook an d M obles C o u n tie s l i n e and I n T p s. 108 and 109 N. I n P ip e s to n e and L in c o ln C o u n tie s a lo n g th e S o u th D akota s ta te lin e .

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P ro p e rtie s ,

in g e n e r a l, o f th e l o e s s

c o v e r in g th e T a z e w e ll d r i f t a r e s i m i l a r i n a l l r e g a r d s t o th e l o e s s o f t h e Iowan r e g io n to th e w e s t.

(Bee p . 3 2 .)

C o lo rs ra n g e fro ® y e llo w t o b u f f to g r a y to brow n.

L eached

l o e s s i n th e zone o f th e modern s o i l p r o f i l e o v e r l i e s a zone o f c a lc a r e o u s c o n c r e tio n s o r n o d u le s .

I n th e w e s te r n

p a r t o f t h e T a z e w e ll r e g io n w here th e l o e s s i s t h i c k e r th e lo w e r zone o f t h e l o e s s i s c a lc a r e o u s , b u t i n th e e a s t e r n p a r t o f th e T a z e w e ll r e g io n i n many p lace® th e t h i n l o e s s I s le a c h e d t o i t s b a s e . I n g e n e r a l th e l o e s s i s w e ll s o r t e d . Tw enty one sa m p les w ere a n a ly z e d m e c h a n ic a lly .

(Bee f i g . 1 3 .) In f if t e e n

sam p les th e m a jo r a iz e - g r a d e i s th e 1 /1 6 - 1 /3 2 ram. g r a d e . I n s i x sam p les th e m a jo r s iz e - g r a d e I s th e 1 /3 2 - 1 /6 4 mm. g rad e.

P r i n c i p a l s u b s i d i a r y grad© I n th e fo rm e r s e r i e s

i s th e 1 /3 2 - 1 /6 4 mm. grad© and i n th e l a t t e r th e 1 /1 6 1 /3 2 mm. g r a d e .

A b a r g r a p h o f a t y p i c a l T az e w e ll l o e s s

sam ple 1® p r e s e n t e d i n f i g u r e ? . C o n ta m in a tio n o f th e T a z e w e ll l o e s s by l a t e r W isc o n sin I n c r e m e n ts I® d e m o n s tra te d by th e m edian d ia m e te r p l a t s on p l a t e I I .

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v a l l e y t r a i n s th e m edian d ia m e te r shows an i n c r e a s e .

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l o e s s o f th e T a z e w e ll r e g io n t h e r e f o r e i s d e s ig n a te d a s T a z e w e ll an d p o s t- T a z e w e ll l o e s s . The T a z e w e ll and p o s t- T a z e w e ll l o e s s v a r i e s i n th ic k n e s s from @0 in c h e s a lo n g th e w e s te r n b o r d e r to 30 in c h e s n e a r th e T a z e w e ll-G a ry b o r d e r to th e e a s t . L o ess th ic k n e s s d i s c o n t i n u i t y a lo n g T az ew ell-Io w an c o n t a c t . The d i s c o n t i n u i t y i n l o e s s th ic k n e s s t h a t o c c u rs a lo n g th e o u t e r m a rg in o f t h e T az e w e ll d r i f t i n n o r th w e s te r n Iowa i s on© o f th e m o st I m p o rta n t c r i t e r i a f o r s e p a r a t i o n o f t h i s d r i f t from th e Iowan to th e w e s t.

The a b r u p t d e c r e a s e o f

one t o two f e e t I n l o e s s t h i c k n e s s from th e Iow an t o th© T a z e w e ll d r i f t r e g io n ( p i . I I ) demands e x p la n a tio n .

The

m ost l o g i c a l e x p l a n a t i o n , w hich i s s u b s t a n t i a t e * by s t r & t i g r a p h i c e v id e n c e , i s t h a t a t t h i s l i n e a p a r t o f th e s o - c a l l e d P e o r ia n l o e s s o f n o r th w e s te r n Iow a46 p a s s e s 46 Kay, Ck F . f and Graham, J . B . , The I l l i n o i a n an d p o e t - I l l i n o i a n P l e i s t o c e n e g e o lo g y o f Iowa! Iow a O eol. S u rv e y , v o l . 38, p . 178, 1943. u n d e r an d a p a r t m a n tle s th e y o u n g er T az ew ell d r i f t . D i s c o n t i n u i t y I n l o e s s th ic k n e s s a lo n g th e T azew ell b o r d e r i s a p p a r e n t in e a s t e r n Lyon C ounty, Iow a, i n T .97N ., S io u x C ounty, Iow a, i n T .9 6 N ., O 'B rie n C ounty, Iow a, an d I n T p s. 90 and 91

C herokee C ounty, tow *.

D e ta ile d

b o r in g was n o t c a r r i e d o u t in th e Iowan an d T a z e w e ll d r i f t r e g io n s i n M in n e s o ta , b u t e x a m in a tio n o f th e p l o t t e d r e ­ c o n n a is s a n c e b o r in g s shows t h a t th e t h i c k n e s s d i s c o n t i n u i t y a l s o h o ld s t r u e a lo n g th e m a rg in o f th e d r i f t i n t h a t a r e a . I n s e v e r a l a r e a s th e d i s c o n t i n u i t y i n l o e s s th ic k n e s s a c r o s s th e o u t e r m arg in o f th e T a z ew ell d r i f t i s n o t a p p a r e n t.

F o r ex m ap le, a t r a v e r s e a c r o s s M ill C reek

on th e O’B ria n -C h e ro k e e C o u n tie s l i n e I n Iowa i l l u s t r a t e s th is fa c t.

{See p i . I I . )

L o ess th ic k n e s s i n th e Iow an

r e g io n w e st o f M ill C reek I s a p p r o x im a te ly 80 I n c h e s .

In

th e T a z e w e ll r e g io n e a s t o f M ill G reek th e t h i c k n e s s I s a l s o 80 in c h e s . a lo n g t h i s l i n e

Mote a l s o th e e v e n ly s p a c e d i s o p l e t h s to th e w e st an d e a s t .

The r e a s o n f o r t h i s

a p p a r e n t c o n f o r m ity i s t h a t th e M ill C reek v a l l e y t r a i n s e rv e d a s a l o c a l s o u rc e f o r l o e s s i n t h i s a r e a . o b s e r v a tio n o f t h e g r a v e l s , s a n d s , and s i l t s

F ie ld

i n th e

t e r r a c e s a lo n g M ill C reek a f f i r m s t h i s c o n c lu s io n . The l o e s s - d r i f t r e l a t i o n s h i p s a lo n g th e T a z e w e ll b o r d e r i n n o r th w e s te r n Iow a a r e s i m i l a r to th o s e d e s c r ib e d by L e ig h to n 4,7 I n I l l i n o i s .

He r e p o r te d t h a t a p a r t o f th e

417 L e ig h to n , M. M., The P e o r la n l o e s s and th e c l & s s l f I c a t l o n o f th e g l a c i a l d r i f t s h e e ts o f th e M i s s i s s i p p i V a lle y ; J o u r . G eology, v o l. 39, p p . 4 5 -5 3 , 1 931.

69

P e o r ia n l o e s s l a y belo w a n d a p a r t upon a d r i f t -

At th a t

tim e th e d r i f t b etw e en th e l o e s s e s was c o n s id e r e d E a r ly W isc o n sin .

I n 1933 L e ig h to a 4 8 a p p l i e d th e s p e c i f i c name

48 L e ig h to n , M. M ., The nam ing o f th e sub­ d i v i s i o n s o f t h e W isc o n sin g l a c i a l a g e : S c ie n c e , new s e r . , v o l. 7 7 , p . XS8, 1933. T a z e w e ll to th e d r i f t -

F u r t h e r c l a r i f i c a t i o n o f th e

r e l a t i o n s h i p o f th e P e o r ia n l o e s s to th e W isco n sin d r i f t s was p r e s e n t e d b y Kay an d L e ig h to n - ^ who d e s c r ib e d a 4^ Kay, 6 . F -, and L e ig h to n , M. M ., E ld o ra n ©pooh o f th e P l e i s t o c e n e p e r io d : ® eo l. S oe. A m erica B u l l - , v o l44, p p . 669—6 7 4 , 1933s l i g h t l y w e a th e re d l o e s s (Io w an ) u n d e r th e T azew ell d r i f t and a n o t h e r l o e s s (T a z e w e ll) o v e r th e d r i f t . The n o r th w e s te r n Iow a r e g io n d i f f e r s from th e a r e a i n I l l i n o i s I n t h a t th e Iowan t i l l

i s n o t known to

o c c u r in I l l i n o i s . S tra tig ra p h y S e v e r a l ro a d cut© i n th e r e g io n o f th e T a z e w e ll d r i f t show th e s t r a t i g r a p h i o s u p e r p o s i t i o n o f th e T az e w e ll d r i f t on th e t h i n l y l o e s s - o r a llu v iu m - m a n tle d Iow an d r i f t . R e c e n tly i n t e r p r e t e d w e ll r e c o r d s from th e T a z e w e ll r e g io n

60

on f i l e a t th e Iowa G e o lo g ic a l Survey c o n firm th e f i e l d I n t e r p r e t a t i o n ® o f th e w r i t e r ,

C a r lto n C o n d it c o l l e c t e d

th e sa m p les o f th e w e ll c u t t i n g s .

C o r n e lia Cameron s t u d i e d

and I n t e r p r e t e d th e sa m p les i n th e la b o r a to r y * S h eld o n s e c t i o n A r o a d c u t l o c a t e d on© m ile s o u th e a s t o f S h e ld o n ,

a t th e h a l f s e c t i o n l i n e b etw een s e c s . 4 and

9,

T .9 6 N ., R .42W ., C#B r ie n C ounty, Iowa h a s b een d e s c r ib e d in

th e l i t e r a t u r e b y s e v e r a l a u t h o r s . 80

Kay a c c e p te d

th is

80 Kay, (K P ., an d A p fe l, E. T ., The p re ~ I l l l n o i a n P l e i s t o c e n e g e o lo g y o f Iow a: Iow a G eo l. S u rv ey , vo l* 34, p p . 278^279, 1929. Carman, J . E . , o p . c i t . ( F u r t h e r S t u d i e s ) , p . 61. L e v e r e t t , F ra n k , Q u a te rn a ry g e o lo g y o f M in n e so ta a n d p a r t s o f a d j a c e n t s t a t e s : U. S. G eo l. S urvey P r o f . P a p e r 161, p . 36 , 1932. Kay, Gk F . , an d Graham, J . B ., op. c i t . # p . 69, 122. s e c t i o n a s th e e t r a t l g r a p h i c e v id e n c e o f an Iowan t i l l i n n o r th w e s te r n Iow a an d t h a t th e L o v elan d l o e s s i s pre~Iow & n. The w r i t e r e x p o sed th e m a t e r i a l s In t h i s s e c t i o n a t I n t e r v a l e a lo n g th e l e n g t h o f th e r o a d c u t on th e s o u th eld© o f th e r o a d .

B ase p o i n t f o r l o c a t i o n o f tr e n c h e s In

th e c u t i s th e t r e e a t th e I n t e r s e c t i o n o f th e fe n c e l i n e and th e w est edge o f th e f a r m e r 's la n e .

61

Thickness (Inches) E x p o su re Ho. I s 36 f e e t w e s t 4 . B o u ld e ry , c a l c a r e o u s , y e llo w g r a y t i l l ; f r i a b l e , c a lc a r e o u s to s u rfa c e . 3 . C a lc a r e o u s , g r a y l o e s s ; p low ed i n t o b a s e o f o v e r ly in g t i l l , s e c o n d a ry c a r b o n a te s t r e a k s ; no d is tu rb a n c e a t b ase o f lo e s s . 2 . B la c k o r g a n ic so m o f b u r l e d s o il p r o f ile ; s il t y - c l a y te x tu re , m a tr ix le a c h e d , s e c o n d a ry c a r b o n a te a lo n g f r a c t u r e s . 1 . Brown, le a c h e d , s i l t y - c l a y ; s e c o n d a ry c a r b o n a te a lo n g fra c tu re s .

26 13

2

3

E x p o su re Ho. 2: 60 f e e t w e s t 4 . B o u ld e ry , c a lc a r e o u s , g r a y t i l l . 3 . G ray , c a lc a r e o u s l o e s s ; plow ed i n t o b a s e o f o v e r ly in g t i l l ; s e c o n d a ry c a r b o n a te ; t h i n y e llo w sa n d l e n s 2 in c h e s above b a s e ; no d is tu rb a n c e e v id e n t a t base o f lo e s s . 2 . B la c k , le a c h e d o r g a n ic zone o f b u r le d s o i l p r o f i l e ; s e c o n d a ry c a r b o n a te a lo n g f r a c t u r e s . 1 . Brown, le a c h e d , com pact, s i l t y c l a y ; s e c o n d a ry c a r b o n a te a lo n g J o in ts .

24 14

1 4

E x p o su re Ho. 35 65 f e e t w e s t 7 . P e b b ly , c a lc a r e o u s , g r a y t i l l ; s e c o n d a ry c a r b o n a te c o n c r e t i o n s . 6 . G ray , c a lc a r e o u s l o e s s ; se c o n d a ry c a r b o n a te ; d is c o n tin u o u s san d s t r i n g e r s a t b a s e ; plow ed i n t o b a s e o f o v e r ly in g t i l l ; no d i s ­ tu r b a n c e a t b a s e o f l o e s s . 5 . B la c k o r g a n ic zone b u r le d s o i l p r o f i l e ; m a tr ix le a c h e d , s e c o n d a ry c a r b o n a te a lo n g f r a c t u r e s .

20 9

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62

Thickness {inches) 4.

Brown, le a c h e d , s i l t y c la y ; s e c o n d a ry c a r b o n a te a lo n g J o i n t s I n u p p e r 7 in c h e s ; h o r i z o n t a l b ed d e d s t r u c t u r e . 3 . B o rin g s brow n, le a c h e d s i l t y c l a y . 2 . B o rin g s brow n, c a lc a r e o u s , s i l t y c la y . 1 . B o rin g s co m p act, brow n, c a lc a r e o u s c l a y ; p e b b le s a t to p o f h o r iz o n d o m in a n tly lim e s to n e , a few s i l i c e o u s p e b b le s .

IS

30 18 24

E x p o su re Bo. 4s 90 f e e t w e s t 4.

d r a y t o b u f f , c a lc a r e o u s , s i l t y p e b b ly t i l l ; a p p e a r s to be m ix tu re o f t i l l a n d u n d e r ly in g lo e s s . 3 . O ray, c a lc a r e o u s l o e s s ; plow ed i n t o b a s e o f o v e r ly in g t i l l ; no d is t u r b a n c e a t b a s e . 2 . B la c k , le a c h e d o r g a n ic zone o f b u r ie d s o i l p r o f i l e ; s e c o n d a ry c a r b o n a te . 1 . Brown, le a c h e d , s i l t y c la y ; se c o n d a ry c a r b o n a te .

32

13 2 3

E x p o su re Ho. 5s 136 f e e t w e st 4.

Brown to b u f f , le a c h e d , w e l l s o rte d lo e s s . 3 . B u f f , b o u ld e r y , c a lc a r e o u s t i l l . 2 . B u ff to g r a y , c a lc a r e o u s l o e s s ; m ixed w ith o v e r ly in g t i l l ; s e c o n d a ry c a r b o n a te . 1 . B la c k , le a c h e d o r g a n ic zone o f b u rie d s o i l p r o f i l e .

27 7 9 2

I n a l l p r e v io u s d e s c r i p t i o n s o f t h i s s e c t i o n th e t h i n u n d is t u r b e d o r g a n ic zone o f th e b u r le d s o i l p r o f i l e h as b e e n e i t h e r o v e rlo o k e d o r ig n o r e d .

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c a n n o t a g r e e w ith t h i s i n t e r p r e t a t i o n f o r l i t h o l e g l e and s t r a t l g r a p h l e b r e a k s below th e t i l l a r e n o t e x p l a in e d . The s u r f a c e s lo p e I n th e ro a d c u t v a r i e s from one t o t h r e e p e r c e n t b u t th e o r g a n ic zone I n th e b u r le d s o il p ro file i s e s s e n tia lly f l a t .

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o r g a n ic s o i l o f th e b u r l e d s o i l p r o f i l e I s i n p la c e th ro u g h o u t th e o u t an d h a s n o t b een d i s t u r b e d .

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o f th e s o i l b y th e o v e r r i d i n g i c e t h a t d e p o s ite d th e t i l l I n th e s e c t i o n was a p p a r e n t l y p r e v e n te d b y th e c a lc a r e o u s l o e s s t h a t m a n tle s th e s o i l . how ev er, I s d i s t u r b e d .

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l o e s s a r e u n le a c h e d .

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n o ii- c a lc a r e o u s m a t e r i a l I s p r e c lu d e d b y t h i s e v id e n c e o f w e a th e r in g I n p l a c e .

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w e a th e r in g i n th e s e h o r iz o n s im p lie s t h a t a r e l a t i v e l y o l d e r se d im e n t i s o v e r l a i n b y y o u n g er m a t e r i a l s . The b u r l e d s o i l and s i l t y c l a y o f th e S h eld o n s e c t i o n i s p re -Io w a n i n a g e .

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w e a th e r in g e v i d e n t In th e Iowan and p o s t-Io w a n l o e s s I s i n th e s u r f a c e s o i l p r o f i l e .

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s o i l p r o f i l e d e v e lo p e d b etw een th e Iowan l o e s s and T a z e w e ll l o e s s o r l a t e r l o e s s e s t h a t c o n s t i t u t e th e Iowan an d p o s t low an l o e s s o f th e Iowan d r i f t r e g io n . The I n te r b e d d e d c a lc a r e o u s l o e s s i n th e s e c t i o n may be r e g a r d e d a s e i t h e r p r o g l a c i a l o r p r e g l a c i a l I f o n ly th e r e l a t i o n s h i p to i t s o v e r ly in g t i l l

i s c o n s id e r e d .

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c o n t i n u i t y I n t h i s a r e a (10 to SO In c h e s ) m ust be c o n s id e r e d .

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67

4. 3. 2. 1.

T a z e w e ll and p o s t- T a z e w e ll l o e s s . T a z e w e ll t i l l . Iow an l o e s s . P re -Io w a n s i l t y c l a y .

Iow an t i l l i s n o t p r e s e n t I n th e s e c t i o n a n d a p p a r e n t l y was n o t d e p o s ite d I n t h i s l o c a l a r e a .

E r o s io n o f th e t i l l I s

p r e c lu d e d b y th e u n d is t u r b e d n a t u r e o f th e o r g a n ic zone o f th e s o i l p r o f i l e o f th e p re -Io w a n s i l t y c l a y , th e h o r iz o n upon w hich th e t i l l sh o u ld h av e b e e n d e p o s ite d . The g e n e r a l d e s ig n a ti o n o f p re -Io w a n i s u s e d f o r th e s i l t y c l a y b e c a u s e I t i s n o t p o s s i b l e t o p la c e i t d e f i n i t e l y i n th e P l e i s t o c e n e se q u e n c e . P e te r s o n s e c t i o n I n a ro a d c u t a lo n g S t a t e Highway 10 i n th e NW c o r . s e c . 36, T .94M ., R.38W ., C la y C o u n ty , Iowa a p p r o x i­ m a te ly one m ile e a s t o f P e te r s o n th e f o llo w in g s e c t i o n i s exposed:

6.

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(S e e f i g . 1 0 ,)

M ixing o f T a z e w e ll t i l l an d Iowan

l o e s s c a u s e d by th e o v e r r i d i n g o f th e l o e s s b y T a z e w e ll i c e I s I n d i c a t e d by th e n a tu r e o f th e m a t e r i a l o f zone 3 . The p o c k e t - f i l l o c c u rre n c e o f th© b u r le d l o e s s on th© u n d e r ly in g t i l l th© w r i t e r b e l i e v e s to b© r e q u i s i t e f o r p r e s e r v a t i o n o f th© Iowan l o e s s i n th e T a z e w e ll r e g io n o f n o r th w e s te r n Iow a.

P r i o r to th e ad v an ce o f T az e w e ll

i c e th e l o e s s m a n tle on th e Iowan d r i f t i n t h i s r e g io n was p r o b a b ly one to tw o f e e t t h i c k .

O v e r r id in g by th e T a z e w e ll

I c e u n d o u b te d ly w ould o b l i t e r a t e su c h a t h i n d e p o s i t e x c e p t i n l o e s s - f i l l e d low s on th e Iow an s u r f a c e . I n th e P e te r s o n s e c t i o n no e v id e n c e o f l e a c h i n g i s fo u n d e x c e p t In th e modern s u r f a c e s o i l p r o f i l e .

The

l a c k o f a s u b s u r f a c e le a c h e d zone i s c h a r a c t e r i s t i c o f th e W isc o n sin se o u e n c e i n th® Iowan and T az ew ell r e g io n s i n n o r th w e s te r n Iow a.

PARTICLE

SIZE?01AM--MM

69

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20

30

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PERCENT BY WEIGHT

Fig* 10* T e x tu r e o f Iow an I de s s o f P e te r s o n s e c t i o n

70

F ig . 1 1 . T a z e w e ll t i l l o v e r Iow an l o e s s , P e te r s o n s e c t i o n .

71

M ill G reek s e c t i o n k react c u t on th e s o u th slop© o f a d e e p , n arro w

r a v i n e n e a r M ill C reek , In th e wc BS| s e c . 19 , T .9 3 N ., B.40W ., C herokee C ounty, Iow a was d e s c r ib e d b y Carman i n 1931.83.

V e g e ta tio n and slum p o b s c u re th e r e l a t i o n s h i p s 81 Carman, J . E ., op. c i t .

(F u rth e r S tu d ie s ),

p . 50. d e s c r ib e d b y Carman, b u t th e v a r i o u s u n i t s c a n be l o c a t e d b y d ig g in g and b o r in g .

4 . Brown to b u f f , le a c h e d l o e s s . 3 . X ello w to brow n, c a lc a r e o u s , b o u ld e r y t i l l . 2 . G-ray, san d y , com pact, e a l c a r e o u s , f o s s i l i f e r o u s c la y . 1 . X ello w , c a lc a r e o u s , com pact t i l l ; g r a d e s to g ra y un­ o x id iz e d t i l l i n e x p o s u re s i n r a v in e down to M ill C reek .

T h ic k n e s s ( in c h e s ) 48 90 84 36

The t i l l o f zone 1 i s ex p o sed a t i n t e r v a l s on th© s lo p e s o f th e r a v in e from th e ro a d to M ill C reek . th e t i l l

T h ic k n e s s o f

lg 45 f e e t . Carm an’ s i n t e r p r e t a t i o n o f t h i s s e c t i o n w as: 4. 3. 2. 1.

P e o r la n l o e s s . Iowan t i l l . L o v e la n d s i l t s . K ansan t i l l .

The w r i t e r d is a g re e ® .

The s u r f a c e o f th e zone 2 h a s a

slop© o f o n ly one to two p e r c e n t and e v i d e n t l y h a s n o t b een ero d ed .

I f t h i s w ere L o v e la n d , i t sh o u ld be le a c h e d to a

c o n s id e r a b le d e p th b u t i t i s c a lc a r e o u s t o th e to p . s u r f a c e o f zone 1 a l s o h a s a s l i g h t s lo p e .

The

I f zone 1 w ere

K ansan, a le a c h e d zone s h o u ld o c c u r a t t h e to p o f th e t i l l . The g e n t l e s lo p e p r e c l u d e s e r o s i o n n e c e s s a r y to rem ove th e le a c h e d zo n e. The s e d im e n ts i n th© s e c t i o n r e p r e s e n t r e l a t i v e l y young, u n w e a th e re d h o r iz o n s a n d a r e r e c l a s s i f i e d : 4. 3. 2. 1.

T a z e w e ll an d p o s t- T a z e w e ll l o e s s . T a z e w e ll t i l l . Iowan s a n d y - c la y . Iow an t i l l . C herokee s e c t i o n

Carman^S d e s c r ib e d a s e r i e s o f ro a d o u ts a lo n g 82 Carman, J . S . , op. c i t . p p . 51, 62, 1 9 3 1 .

( F u r th e r S t u d i e s ) ,

S t a t e Highway 5 on th e e a s t v a l l e y s lo p e o f th e L i t t l e S io u x R iv e r j u s t e a s t o f C h ero k ee, Iow a.

These c u ts were

s t u d i e d b y C anaan an d Kay in 1927 and b y Kay i n 1 9 2 8 .8 3 88 Kay, 9 . F . , an d A o fe l, K. T .,o p . c i t . , p p . 1 5 9 , 1 60. The s e c t i o n was I n t e r p r e t e d a s f o llo w s :

6. 5. 4. 3. 2. 1.

P e o r ia n l o e s s . Iow an t i l l and g r a v e l s . L o v e la n d s l i t s . K ansan t i l l . N eb rask a n g u m b o tll. N eb rask a n t i l l .

The c u te a r e now so h e a v i l y c o v e re d by v e g e t a t i o n t h a t th e y a r e d i f f i c u l t to s tu d y . h o r iz o n s can b e d e l i n e a t e d .

However, th e v a r io u s

A ll h o r iz o n s b etw e en th e

g u m b o til and th e m odern s o i l p r o f i l e in th e s u r f a c e l o e s s i n th e h ig h c u t a re c a lc a r e o u s th r o u g h o u t.

S lo p e s o f th e

c o n t a c t s b e tw e e n h o r iz o n s a r e s l i g h t and a s i n th e M ill G reek s e c t i o n p r e c lu d e e r o s io n n e c e s s a r y t o s t r i p le a c h e d zo n e s t h a t s h o u ld o c c u r on th e t i l l I d e n t i f i e d a s K ansan and th e s i l t s

i d e n t i f i e d a s L o v e la n d .

T h e r e f o re ,

th e

w r i t e r b e l i e v e s t h a t th e w hole s e c t i o n s h o u ld be r a i s e d one l e v e l i n th e s t r a t i g r a p h i c seq u en ce and th e s e r i e s o f c u t s s h o u ld b® i n t e r p r e t e d as f o llo w s : 6. 5. 4, 3. 2. 1.

T a z e w e ll and p o s t- T a z e w e ll l o e s s . T a z e w e ll t i l l and g r a v e l s . Iow an s i l t s . Iow an t i l l , K ansan g u m b o til. Kansan t i l l .

Summary o f E v id e n c e f o r T a z e w e ll D r i f t T hree l i n e s o f e v id e n c e , to p o g r a p h ic , l i t h o l o g i c , and f l t r a t i g r a p h i o ,

d i s t i n g u i s h a T a z e w e ll d r i f t in n o r th ­

w e s te r n Iow a and s o u th w e s te rn M in n e so ta .

74

to p o g r a p h ic e v id e n c e i n c l u d e s a d is c o n tin u o u s en d m o rain e o r a c h a r a c t e r i s t i c m a rg in a l s lo p e a t o r n e a r th e w e s t b o r d e r o f th e d r i f t s h e e t , s lo p e s and r e l i e f more su b d u ed th a n on th e a d j a c e n t Iowan d r i f t ,

d iv e rs io n o f

d r a in a g e l i n e s a lo n g th e o u t e r m a rg in o f th e T a z e w e ll d rift,

an d a c h a r a c t e r i s t i c m a rg in a l t r i b u t a r y d r a in a g e

p a tte rn . I d t h o l o g l c e v id e n c e in c lu d e s a d i s c o n t i n u i t y i n s u r f a c e l o e s s t h i c k n e s s and th e p r e s e n c e o f m a rg in a l o u t w ash a t th e Iow & n-T azew ell b o r d e r . S tr a tlg r a p h l © e v id e n c e I s p r e s e n te d by f o u r s e c t i o n s t h a t show a c a lc a r e o u s l o e s s o r a c a lc a r e o u s , f o s s i l i f e r o u s , a l l u v i a l m a t e r i a l o c c u p y in g a s t r & t i g r a p h i e p o s i t i o n s e p a r a t i n g tw o c a lc a r e o u s t i l l s , Io w an .

th e T a z e w e ll and

W ell r e c o r d s on f i l e a t th e Iowa G e o lo g ic a l S urvey

g iv e f u r t h e r c o n f ir m a tio n o f t h i s s t r a t i g r a p h i c i n t e r p r e ­ ta tio n . I n many r e s p e c t s th e T a z ew ell d r i f t i n t h i s r e g i o n i s r e c o g n iz e d on th e same b a s i s a s In th e ty p e T a z e w e ll a r e a i n I l l i n o i s .

7S

THU CARY DRIFT Summary o f P r e v io u s Work on Beg M oines Lobe C a rm a n ^ i n h i a r e p o r t o f 1917 p r e s e n te d th e 54 Carman, J . I . , The P l e i s t o c e n e g e o lo g y o f n o r th w e s te r n lo w ai Iow a G e o l. S u rv e y , v o l . 26, p p . 2 5 2 293, 1 9 1 7 .

f i r s t d e t a i l e d t r a c i n g o f th e m arg in o f th e W isco n sin d r i f t (D es M oines lo b e ) i n n o r th w e s te r n Iow a.

S u b se q u e n t

r e p o r t s on th e P l e i s t o c e n e g e o lo g y o f th e s t a t e p u b lis h e d b y th e Iow a G e o lo g ic a l S u rv ey p r i o r t o 1941^® a c c e p te d 56 Kay, G. F . , and A p fe l, E. T . , The p r e I l l l n o i a n P l e i s t o c e n e g e o lo g y o f Iow a: Iow a G eo l. S u rv ey , v o l . 34, p i . 2, 1929. Carman, J . E«t F u r th e r s t u d i e s on th e P l e i s t o c e n e g e o lo g y o f n o r th w e s te r n Iow a: Iow a G eo l. S u rv ey , v o l . 35, p i . 1 , 1931. Carm an*s W isc o n sin b o r d e r .

The W isco n sin d r i f t o f low®

was r e c l a s s i f i e d a s M ankato b y L e ig h to n In 19335^ an d d r i f t L e ig h to n , M. M., The nam ing o f th e su b ­ d i v i s i o n s o f th e W isc o n sin g l a c i a l a g e : S c ie n c e , new s e r . , v o l. 77, p . 168, 1933. o f th e Bes M oines lo b e h a s b een a c c e p te d a s M ankato I n

76

&g©57 sine© t h a t tim e . W to y , 0 . F ., a n 0 M i l l e r , P . T . , The P l e i s t o ­ c e n e g ra v e l® o f Iow a: Iowa G e o l. S u rv ey , v o l. 37, p . 12 , 1941 * t o y , 0 . F . # an d Graham, *T. B ., The X l l l n o i a n and p o s t - I l l i n o l a n P l e i s t o c e n e g e o lo g y o f Iow a: Iow a G e o l. S u rv e y , v o l . 3 8 , p . 1 0 , 1945. F l i n t , H. F . , an d o t h e r s , G l a c i a l map o f N o rth A m erica: G e o l. S ee. A m erica S p e c ia l P a p e r 60, 1946.

L e v e r e tt^ S t r a c e d th e m a rg in o f th e Des M oines L e v e r e t t , F ra n k , Q u a te rn a ry g e o lo g y o f M in n e so ta an d p a r t s o f a d j a c e n t s t a t e s : U. S. G eo l. S u rv ey P r o f . P a c e r 1 6 1 , pt>. 30 , 5 6 -6 1 , 6 7 -7 1 , p i s . 2 , 3, 1 932. lo b e In e a s t e r n S outh D ak o ta, s o u th w e s te rn M in n e so ta , and n o r th w e s te r n Iow a.

Th© end m o rain e a t t h e m arg in o f th©

lo b e was named th e Bemis m o rain e and th e a d j a c e n t I n n e r m a jo r end m o rain e was d e s ig n a te d th e A ltam o n t m o ra in e . D u rin g th® p a s t two f i e l d season© th e w r i t e r t r a c e d th e s e tw o m o ra ln io b e l t s from n o r th e r n C a r r o l l C o unty , Iow a n o rth w e s tw a rd i n to e a s t e r n S o u th D ak o ta. Th© m a rg in o f th© Des M oines lo b e was mapped a c c u r a t e l y by Carman and L e v e r e t t , an d th e p r e v io u s m apping o f th e A lta m o n t m o ra in e i n s o u th w e s te r n M in n eso ta r e q u ir e d v e ry little

re v is io n .

However, i n Iowa th e m apping o f th©

A lta m o n t m o ra in e h a s b ee n r e v i s e d .

(Compare p i . I w ith

7?

f i g . 7 o f L ev erett® ® and f i g . 86 o f Kay an d Graham.®0 ) L e v e r e t t , F ra n k , o p . c i t .

( P r o f . P a p e r 1 6 1 ),

p . 30 . Kay, G. F . , an d Graham, J . B ., op . c i t . , p . 239. The d r i f t o f th e Bemis m o rain e from th e m a rg in o f th e Dess M oines lo b e t o th e to e o f th e d i s t a l s lo p e o f th e A ltam o n t m o rain e i n n o r th w e s te r n Iowa and s o u th ­ w e s te r n M in n e so ta i s h e r e r e c l a s s i f i e d a s th e C ary d r i f t , t h e d r i f t from th e m a rg in o f th e A lta m o n t m o rain e t o th e e a s tw a r d an d n o rth w a rd to th e l i m i t o f s tu d y re m a in s d e s ig n a te d as th e M ankato d r i f t . The u s e o f th e te rm C ary r e q u i r e s q u a l i f i c a t i o n . R e g io n a l c o r r e l a t i o n o f t h i s d r i f t o f n o r th w e s te r n Iowa w ith th e ty p e a r e a o f th e C ary I n I l l i n o i s o r th© n e a r e s t r e c o g n iz e d C ary o f e a s t - c e n t r a l M in n e so ta h a s n o t b ee n e s ta b lis h e d .

However, fo u r d r i f t s o f th e W isco n sin s ta g e

h av e b e e n r e c o g n iz e d In th e r e g io n o f s tu d y .

The d r i f t o f

n o r th w e s te r n Iow a t h a t i s b e lie v e d to be C ary o c c u p ie s th e s t r a t l g r & p h l c p o s i t i o n o f th e Cary o f th e s ta n d a r d seq u en ce o f th e W isc o n sin s t a g e .

78

to p o g ra p h y End m o rain e th e o u t e r m a rg in ©£_ th e C ary d r i f t i n n o r t h ­ w e s te r n Iow a a n d s o u th w e s te r n M in n e so ta i s d i s t i n c t l y m arked b y an en d m o ra in e ,

th e d i f f e r e n c e b etw een th e

to p o g r a p h ie s o f th e Tazewell and C ary d r i f t r e g io n s p e r m its a c c u r a t e l o c a t i o n o f th e C ary d r i f t b o r d e r .

Im m e d ia te ly

w e s t a n d s o u th o f t h i s l i n e th e lo e s s - m a n tle d T az e w e ll d r i f t i s e s s e n t i a l l y f l a t t o s l i g h t l y u n d u la tin g w h erea s th e c r e s t o f th e C ary end m o rain e i s hummocky to knobby. B e l i e f b etw een th e lo e s s - m a n tle d T a z e w e ll g ro u n d m o ra in e and th e c r e s t o f th e C ary en d m o rain e r a n g e s from 30 t o 60 f e e t .

R e l i e f on th© i n n e r slop© o f th e o u te rm o s t

en d m o ra in e I n n o r th w e s te r n Iowa a l s o ra n g e s from 30 t o 60 f e e t .

However, I n M urray, P ip e s to n e , an d L in c o ln

C o u n tie s , M in n e so ta p ro x im a l slop© r e l i e f v a r i e s from 180 t o 200 f e e t j d i s t a l slop© r e l i e f i s co m p arab le to th e v a l u e s I n Iow a,

E xam ples a r e p r e s e n te d i n t a b l e 3 .

The d i f f e r e n c e i n r e l i e f on th© o u t e r an d I n n e r s lo p e s o f th e C ary en d m o rain e i n s o u th w e s te rn M in n e so ta e m p h a siz e s th e e f f e c t o f th e C o teau d ee P r a i r i e s on d r i f t c o n s t r u c t i o n In th is a re a .

The i c e a p p a r e n t l y rod© up th e r a t h e r s te e p

e a s t e r n s lo p e o f th© C o teau a n d d e v e lo p e d th e end m o rain e

79

T ab le 3 . D i s t a l a n d P ro x im a l S lo p e R e l i e f on C ary End M oraine L o c a tio n

W l i n e s e c . 1 2 , 9 6 -3 6 , C la y C o ., Iow a W l i n e s e e s . 1 an d 12, 9 8 -3 6 , s e c s . 24 and 26, 9 9 -3 8 D ic k in s o n C o ., Iow a S l i n e s e e . 16 , 9 8 -3 6 , D ic k in s o n C o ., Iow a S l i n e s e c . 28, 9 8 -3 6 , D ic k in s o n C o ., Iow a S l i n e s e c . 33, 1 0 0 -4 1 , O sc e o la C o ., Iow a S l i n e ©ec. 8 , 1 0 6 -4 3 , M urray C o ., M in n e so ta

D is ta l S lo p e

P ro x im a l S lo p e

T fe e i) 56

( fe e t)

00

45

40

30

35 60 40

150

100 to 200 f e e t above th e a d j a c e n t g ro u n d m o rain e t o th e e a s t.

M apping o f th e m arg in o f th e C ary d r i f t i n t h i s a r e a

i n M in n e so ta i s s i m p l i f i e d i f th e m o rain e i s a p p ro a c h e d from th e e a s t . R e l i e f w ith in th e C ary end m o rain e In M urray, P ip e s t o n e , and L in c o ln C o u n tie s , M in n e so ta v a r i e s from 40 to 60 f e e t .

S lo p e s ra n g e from 6 to 16 p e r c e n t and

l o c a l l y from 20 t o 40 p e r c e n t .

From n o r th e r n H obles

C ounty , M in n e so ta so u th w ard to n o r th e r n C a r r o l l C ounty, Iow a r e l i e f v a r i e s w ith in th e end m o rain e from 20 t o 40 fe e t.

S lo p e s ra n g e from 3 to 6 ( l o c a l l y 6 to 1 6 )p e r c e n t .

80

L o c a l r e l i e f may be much g r e a t e r ; e . g . , C cheyeden Mound, l o c a t e d I n th e en d m o rain e on© m ile e a s t o f C cheyeden, O s c e o la C o u n ty , Iow a, r i s e s 150 f e e t above th e s u r r o u n d in g a re a . The O ary end m o ra in e , i n g e n e r a l , i s a somewhat subdued k n o l l an d sag to p o g ra p h y w ith an abundance o f u n d r a in e d d e p r e s s io n s .

However, th© m o r a ln ic to p o g ra p h y i s

much more p ro n o u n c e d th a n i n th e m o rain e a t th e m a rg in o f th e T a z e w e ll d r i f t . th r o u g h o u t i t s

R id g e s in th e C ary end m o rain e

c o u rs e i n Iowa and M in n e so ta can be t r a c e d

a lo n g t h e i r tren d ® f o r a few m ile s to s e v e r a l te n s o f m ile s .

(S ee p i . X ).6 1

61 C r e s t s o f m o ra ln a l r id g e s a r e I n d i c a t e d on p l a t e I b y b lu e l i n e s . R. F. F l i n t I n tr o d u c e d t h i s te c h n iq u e I n h i s m apping o f th e d r i f t s o f S o u th D ak o ta . An i n n e r e n d -m o ra in a l b e l t In th e C ary d r i f t h a s b e e n mapped from s o u th e rn M urray C ounty, M in n eso ta s o u th ­ e a s tw a r d to e a s t e r n C lay C ounty, Iow a.

The m o rain e i s

l o c a t e d from 6 to 12 m ile s to th© e a s t o r n o r th o f th e m a rg in o f th© Cary d r i f t and I s s e p a r a te d from th e o u t e r ­ m ost end m o rain e b y s t r i p s o f g ro u n d m o rain e one to f o u r m ile s I n w id th .

The w e s te rn end m o rain e b i f u r c a t e s n e a r

B ig elo w , N obles C ounty, M in n e so ta , b u t th e two

b ra n c h e s

SI

c o a l e s c e n e a r A lle n d o r f , O s c e o la C o unty, Iow a,

B e lie f

w i t h i n th e i n n e r en d m o rain e v a r i e s from 30 to 30 f e e t and s lo p e s from 3 t o 6 p e r c e n t .

R e l i e f on th e g ro u n d m o rain e

b e tw e e n th e two end m o ra in e s v a r i e s from 5 t o 10 f e e t , an d s lo p e s r a n g e up t o 3 p e r c e n t . The in n e r en d m o rain e p r o b a b ly m arks th e p o s i t i o n o f a h a l t o r a s l i g h t re a d v a n c e d u r in g C ary d e g la c ia tio n .

I n th e h ak e W ilso n , C h a n d le r, H adley a r e a ,

M urray C o u n ty , M in n e so ta th e o u t e r an d i n n e r end m o ra in e s form a l o b a t e p a t t e r n .

T ren d s o f r i d g e s I n th e o u t e r

m o ra in e a t C h a n d le r sw in g to t h e n o r t h e a s t .

To th e n o r th ­

w e s t o f I o n a th e s e t r e n d s tu r n s o u th e a s tw a rd I n t o th e i n n e r e n d - m o r a in a l a r e a .

I n o t h e r w o rd s, tr e n d s o f th e

i n n e r end m o rain e c o a le s c e w ith t r e n d s o f th e o u te r m o ra in e .

T h ere i s no i n d i c a t i o n o f o v e r r i d i n g o r

tru n c a tio n .

A p p a re n tly th e m arg in o f th® Oary i c e

m a in ta in e d i t s p o s i t i o n n o r t h o f C h a n d le r w h ile th e m a rg in t© th e so u th w a rd re c e d e d s e v e r a l m ile s an d became s t a t i o n ­ a r y t h e r e f o r a tim e . D is c o n tin u o u s en d m o ra in e s o f low r e l i e f .

In se v e ra l a re a s

t h e r e a r e d is c o n tin u o u s end m o ra in e s o f low r e l i e f .

T hese

m o ra in e s a r e l o c a t e d a lo n g th e I n n e r m a rg in o f th e e n d m o r a in a l b e l t i n B uena V i s t a C o unty, Iowa an d s o u th e a s t e r n Sac C ounty an d s o u th w e s te rn C alhoun C ounty, Iow a.

(S ee

as p i. i . ) *Ehe p h y s io g r a p h ic e x p r e s s io n o f th e m oraine® o f lo w r e l i e f d if f e r ® d i s t i n c t l y from th e n o rm a l-ty p e G ary en d m o ra in e .

L o c a l r e l i e f b etw een r i d g e s and a d j a c e n t

lo w s v a r i e s fro m 5 t o 10 f e e t .

The r id g e s a r e e lo n g a te

an d p a r a l l e l th e g e n e r a l tr e n d o f th© m o ra in a l b e l t . H ow ever, an i n d i v i d u a l ridg© can be t r a c e d a lo n g i t s f o r o n ly a q u a r t e r o f a mil© to h a l f a m ile . o c c u r in g ro u p s.

tr e n d

The r i d g e s

I n many p l a c e s 10 t o 15 o f th e s e

f e a t u r e s o c c u r I n one s e c t i o n o f la n d .

B ecau se o f t h i s

m u l t i p l i c i t y and th e s c a le em ployed i n m apping, i n d i v i d u a l en d m o ra in e s o f low r e l i e f w ere n o t mapped.

The tr e n d

o f th e p a t t e r n o f a g ro u p , how ever, I s re c o rd e d b y a s h o r t b lu e l i n e i n th e mapped C ary en d m o ra in e .

(Bee p i . I . )

Carman® 2 i n h i e e a r l i e r s tu d y i n n o r th w e s te r n

Carman, J , E . , The P l e i s t o c e n e g e o lo g y o f n o r th w e s te r n Iow a: Iow a G eo l. S u rv ey , v o l . 26, p . 261, 1917. Iowa r e c o g n iz e d th e end m o ra in e s o f low r e l i e f In Buena V i s t a C o unty.

He c o n c lu d e d t h a t many p a tc h e s o f th e

I s o l a t e d te r m i n a l m o rain e c o u ld be a l ig n e d I n b e l t s t h a t m arked s h o r t p e r io d s o f r e s t o f th e ic e m a rg in .

83

dwynn©®*5, more r e c e n t l y and m a in ly on th e b a s i s 0wynne, C. S ., S w e ll and sw ale p a t t e r n o f th e M ankato lo b e o f th e W isc o n sin d r i f t p l a i n i n Iow a: J o u r a e o lo g y , v o l . 50, p p . 2 0 0 -8 0 8 , 1942. o f s tu d y o f a e r i a l p h o to g r a p h s , c o n c lu d e d t h a t th e s e f e a t u r e s a r e s e a s o n a l i n d ev e lo p m e n t and r e l a t e d to i c e re c e s s io n . The w r i t e r a l s o b e l i e v e s t h a t th e m o ra in e s o f low r e l i e f o f t h i s a r e a r e p r e s e n t : (1 ) t i l l d e p o s itio n a t th e m arg in o f a n I c e lo b e , an d (3 ) p a u s e s i n th e g e n e r a l r e t r e a t o f th e m a rg in o f th e I c e m ass.

P a ra l­

l e l i s m o f th© lo w , d is c o n tin u o u s r i d g e s to th e m a jo r m o r a ln a l f e a t u r e s and to e a c h o th e r i n d i c a t e s i c e m a rg in a l d e p o s itio n .

V ery low r e l i e f , d is c o n tin u o u s tr e n d , o f f -

la p p in g o f I n d i v i d u a l r i d g e s , an d m u l t i p l i c i t y o f d i s t r i ­ b u t i o n In a r e a s a s sm a ll a s one sq u a re m ile im p lie s r e l a t i v e l y s h o r t p a u s e s I n th e g e n e r a l r e t r e a t o f an i c e m ass.

I f th e m a rg in o f th e I c e w ere s t a t i o n a r y f o r a

l o n g e r tim e o r I f re a d v a n c e o f any g r e a t m ag n itu d e o f th e m a rg in o f th e i c e h ad o c c u rr e d , to p o g r a p h ic f e a t u r e s more co m p arab le to th e m a jo r f e a t u r e s o f th e C ary end m o rain e s h o u ld hav e b een d e v e lo p e d .

84

G round m o rain e The m oat e x t e n s iv e O ary g ro u n d -m o ra in a l a r e a l a I n s o u th w e s te r n M in n e so ta .

I n M urray an d L in c o ln C o u n tie s ,

M in n e so ta th e end m o rain e r i s e s 150 t o £00 f e e t above th e g ro u n d m o rain e to th e e a s t*

However, th e r e l a t i o n s h i p

b e tw e e n th e C ary g ro u n d m o rain e an d th e en d m o rain e a t th e m a rg in o f th e M ankato d r i f t I s n o t so m arked. G e n tle s lo p e s an d low r e l i e f c h a r a c t e r i s e th e t i l l p l a i n from t h e Iow a s t a t e l i n e th ro u g h s o u th w e s te r n M in n e so ta to th e S o u th D akota s t a t e l i n e .

S lo p e s r a n g e

up to 3 p e r c e n t an d l o c a l u p la n d r e l i e f from 5 t o 10 f e e t . The t i l l p l a i n i s w id e s t, a p p r o x im a te ly 25 m ile s , I n N o b les an d J a c k s o n C o u n tie s , M in n e so ta . I n Iow a g ro u n d m o rain e c o m p ris e s l e s s a r e a o f th e C ary d r i f t r e g io n th a n doe® end m o ra in e .

In g e n e ra l,

th e t i l l p l a i n s a r e I n s t r i p s t h a t v a ry i n w id th from f o u r t o s i x m ile s .

S lo p e s v a ry from 3 to 6 p e r c e n t a n d

l o c a l r e l i e f from 5 t o 10 o r 10 to 26 f e e t . D ra in ag e The C ary d r i f t i s p o o r ly d r a in e d . d e p r e s s io n s a r e a b u n d a n t. t i l l p la in la k e s .

U n d ra in ed

I n M in n e so ta t h e r e a r e many

(See p i . I . )

The u n d r a in e d c o n d i t i o n o f

85

t h e C ary s u r f a c e g e ts i t o f f d i s t i n c t l y from th e T a z e w e ll and Iow an s u r f a c e s to th e w e s t. A g r a p h i c a l c o m p a riso n o f s lo p e p a t t e r n s i n

th e s e o l d e r W isc o n sin d r i f t s and th e y o u n g er C ary d r i f t i s g iv e n i n f i g u r e 3 .

The C ary s u r f a c e h a s a r e l a t i v e l y

g r e a t e r number o f a r e a s w here s lo p e s ra n g e up to 3 p e r c e n t an d a l e s s e r num ber o f a r e a s w here s lo p e s ra n g e from 3 to 6 o r 8 to 16 p e r c e n t . C om parison o f th e s t a g e s o f d r a in a g e d ev elo p m en t i n th e s e t h r e e W isc o n sin d r i f t s shows t h a t a tim e b r e a k o f m ajo r s i g n i f i c a n c e o c c u r r e d b etw een th e r e c e s s io n o f th e T a z e w e ll I c e and th e ad v an ce o f C ary I c e .

The tim e

I n t e r v a l was lo n g enough f o r th e e s ta b lis h m e n t o f d r a in a g e on th e T a z e w e ll t i l l

s u r f a c e w h ereas th e C ary

s u r f a c e I s y o u n g e r and i s p o o r ly d r a in e d . The c r e s t o f th e end m oraine a t th e m arg in o f th e G ary d r i f t ,

w ith th e e x c e p tio n o f th e O sc e o la , D ic k in ­

so n , an d C lay C o u n tie s a r e a s , c o n s t i t u t e s th e M i s s i s s i p p i M ls s o u ri d iv id e I n Iow a.

I n O sc e o la , D ic k in so n , and

O lay C o u n tie s s tr e a m s debouehe fro® th e end m o rain e an d flo w to t h e s o u th e a s t to t h e i r p o i n t s o f J u n c tu r e w ith tittle

S io u x R iv e r w hich flo w s g e n e r a l l y s o u th e a s tw a rd to

th e M is s o u ri R iv e r .

S tream s in a l l o t h e r a r e a s J o in

tr u n k s t h a t flo w s o u th e a s tw a rd to th e M i s s i s s i p p i R iv e r .

@6

I n s o u th w e s te r n M in n e so ta th e same r e l a t i o n s h i p l a t r u e b u t a g a in w ith th e e x c e p tio n o f th e L i t t l e S io u x , Hook, an d L i t t l e Hook HI v e r s and t h e i r t r i b u t a r i e s . L ith o lo g y T ill P h y s i c a l c h a r a c t e r i s t i c s o f t h e G ary t i l l a r e s i m i l a r t o th o s e o f th e Iowan an d T a z ew ell t i l l s . ra n g e from y e llo w t o l i g h t s h a d e s o f brow n. m odern s o i l l a d e v e lo p e d i n th e t i l l ,

C o lo rs

Where th e

th e o o lo r g ra d e s

from brow n b e n e a th th e zone o f o r g a n ic a c c u m u la tio n t o y e llo w i n th© le a c h e d an d u n le a c h e d t i l l o f lo w e r h o r iz o n s . The t e x t u r e o f th e Oary t i l l d o es n o t d i f f e r s i g n i f i c a n t l y from th e o l d e r W isc o n sin t i l l s .

(S ee f i g s . 5 and 6 . )

The C ary t i l l , how ever, d o es d i f f e r from th e Iow an an d T a z e w e ll t i l l s i n t h a t : lo c a lly ;

(1 ) i t h a s b een le a c h e d

(2 ) i t d o e s n o t h av e a d i s t i n c t l a g c o n c e n tr a te

o r p e b b le band a t I t s s u r f a c e ; (3 ) b o u ld e r s a r e ex p o sed on i t s

s u r f a c e , an d (4 ) i t s o v e r ly in g l o e s s i s t h i n and

p a tc h y . Where t h e r e I s l i t t l e o f th e G ary t i l l i s le a c h e d .

o r no l o e s s th e u p p e r p a r t

F o r ex am p le, i n th e SEi NEJ

s e e . 25, T .1 0 4 N ., B.43W ., N o b les C ounty, M in n eso ta a

a?

b o r in g p e n e tr a te d * T h ic k n e s s (In c h e s) 20

3 . Brown, le a c h e d , p o o r ly s o rte d lo e s s . 2 . Y ello w , le a c h e d , p e b b ly , fria b le t i l l . 1 . Y ello w , c a l c a r e o u s , p e b b ly , fria b le t i l l .

2

H ow ever, th e t i l l may be c a lc a r e o u s even w here o v e r l a i n b y t h i n l o e s s a s shown b y th e b o r in g I n th e NW-J

se c . 18,

T. 1 0 4 N ., R .41W ., in th e same c o u n ty : T h ic k n e s s ( in c h e s ) 2. Brown, le a c h e d , p o o r ly s o rte d lo e s s , 1 . Y ello w , c a lc a r e o u s , p e b b ly , fria b le t i l l .

26

Where t h e r e I s no l o e s s th e t i l l i s le a c h e d to v a r i a b l e d e p th s d e p e n d e n t upon th e s lo p e p o s i t i o n o f th e m a te ria l.

C la r io n s o i l s ( p a r e n t m a t e r i a l g l a c i a l t i l l )

a r e d e v e lo p e d on s lo p e s o f 2 to IS p e r c e n t and th e t i l l I s le a c h e d t o d e p th s o f 25 to 35 I n c h e s .

S to rd e n s o i l s

a r e fo u n d on s lo p e s o f 8 to 20 p e r c e n t w here l e a c h i n g e x te n d s a few t o s e v e r a l in c h e s b elow th e t i l l s u r f a c e . S tra tifie d d r if t I n g e n e r a l , s t r a t i f i e d d r i f t o f C ary age I s c o n c e n tr a t e d i n w e ll d e f in e d v a l l e y t r a i n s a lo n g th e m a jo r s tre a m s t h a t debouche from th e m a rg in o f th e C ary

88

d r i f t re g io n *

V a lle y t r a i n s a r e w e ll d e v e lo p e d a lo n g

L i t t l e O oheyeden an d O oheyeden R iv e r s an d S to n y C reek i n O s c e o la , D ic k in s o n , a n d C la y C o u n tie s , Iow a.

I n T ps. 96

and 9 7 N ., R. 37W. , C la y C o u n ty , Iowa t h e r e i s an e x t e n s iv e o u t w ash p l a i n t h a t c o n t a i n s , how ever, b o th C ary an d M ankato m a te ria ls .

The L i t t l e S io u x R iv e r abo v e S p en ce r, Iow a

d r a i n s b o th th© C ary an d M ankato d r i f t s .

(S ee p i .

I .)

I n s o u th w e s te r n M in n e so ta d i s t i n c t v a l l e y t r a i n s a l s o h e a d a t th e m a rg in o f th e C ary d r i f t *

In

108

a n d 109K ., R.45W .f P ip e s to n e an d L in c o ln C o u n tie s t h e r e i s a l s o an e x t e n s iv e o u tw ash a p ro n a lo n g th e m a rg in o f th e C ary d r i f t . L o c a lly s t r a t i f i e d d r i f t i s c o n c e n tr a te d i n kam es i n th e en d m o ra in e s o f th© C ary d r i f t .

These h i l l s

o f sa n d an d g r a v e l w ith s te e p s lo p e s o f 16 t o 40 p e r c e n t c o n s t i t u t e p ro m in e n t to p o g r a p h ic f e a t u r e s .

I n many p l a c e s

kam es a r e th e m o st d i s t i n c t i v e f e a t u r e s i n th e end m o ra in e s . L o ess Kay an d Oraham®4 s t a t e d :

**. . . th e M ankato I s

Kay, C. F . , an d Craha®, J . B ., o p . c i t . , p . 206. u n c o v e re d b y l o e s s .

. . .*

The term M ankato I n t h i s

89

q u o t a t i o n a p p l i e d t o th e d r i f t o f th e Bes M oines l o b e . S o i l s c i e n t i s t s c o n c u rre d i n th e b e l i e f t h a t no l o e s s e x i s t s on th e Dee M oines l o b e .

The l a t e s t s o i l a s s o c i a t i o n

map o f Iowa®® shows t h a t th e C la r lo n -W e b s te r a n d S to r d e n P r i n c i p a l S o i l A s s o c ia tio n A re as i n Iow a: Iow a A g rie . E x p e r. S ta . i n c o o p e r a tio n w ith B iv . o f S o i l s Survey* 0 . S. D e p t, o f A g r i o ., 1940. Q Ia rio n -W e b s te r a r e a s c o n s t i t u t e th e w hole o f th e Des M oines lo b e . g la c ia l t i l l .

T h ese s o i l s b y d e f i n i t i o n a r e d e v e lo p e d i n I n c o n t r a d i c t i o n t o th© g e n e r a l b e l i e f o f

th e n o n - o c c u r r e n c e o f l o e s s on th© Des M oines lo b e , th e w r i t e r r e p o r t s t h a t a d is c o n tin u o u s m a n tle o f l o e s s e x i s t s on b o th t h e G ary a n d M ankato d r i f t s . The l o e s s o f th e G ary d r i f t r e g io n i s g e n e r a l l y brow n.

I n m o st l o c a l i t i e s th e modern s o i l p r o f i l e i n ­

c o r p o r a t e s th e e n t i r e th ic k n e s s o f th e l o e s s .

W e a th e rin g

h as n o t p r o g r e s s e d to th e s ta g e w here th r e e h o r iz o n s o f th e p r o f i l e a r e d e t e c t a b l e .

An A-G p r o f i l e u s u a l l y e x i s t s .

No c l a y movement I s o b s e r v a b le .

The h o r iz o n s a r e

d i f f e r e n t i a t e d upon a c o l o r b a s i s . r a n g e s from b ro w n is h b la c k to b la c k .

N o rm ally th© A h o r iz o n B la c k i s th© d o m in en t

c o l o r w here f r e e c a rb o n o c c u rs in ab u n d an ce.

The A

h o r i z o n g r a d e s downward I n to th© 0 h o r iz o n a n d 1© m arked b y a t r a n s i t i o n i n c o l o r from b ro w n ish b la c k o r b la c k t o

90

b row n,

The l o e s s c o n t a in s an ab u n d an ce o f o r g a n ic m a tte r ,

h e n c e th e brow n c o l o r I s c h a r a c t e r i s t i c to t h e b a s e o f th e l o e s s . The l o e s s o v e r th e C ary d r i f t i s g e n e r a l l y le a c h e d .

I n th e many b o r in g s made an d r o a d out© ex am in ed

o n ly one s e c t i o n , L in n O rove, Buena V is ta C ounty, Iow a, showed c a lc a r e o u s l o e s s .

(S ee p i . I I . )

T e x tu r e s o f e i g h t l o e s s sa m p les c o l l e c t e d I n s o u th w e s te r n M in n e so ta an d n o r th w e s te r n Iowa were d e te rm in e d by m e c h a n ic a l a n a l y s i s .

(B ee f i g . 1 2 .)

M edian d ia m e te r s

and c o e f f i c i e n t s o f sorting® ® o f th e sam p les w ere d e te rm in e d T ra s k , P . SL, S tu d ie s o f r e c e n t m arin e s e d im e n ts c o n d u c te d b y th e A m erican P e tro le u m I n s t i t u t e : M at. R e s e a rc h C o u n c il, R e p t. Comm. B e d ., p p . 6 0 -6 7 , 1952. f o r p u r p o s e s o f c o m p a riso n .

T e x tu r e s o f th e sample© ra n g e

from w e ll s o r t e d to p o o r ly s o r t e d .

C o e ffic ie n ts o f s o r tin g

v a r i e d from 1 .2 6 t o 4 .5 8 and m edian d ia m e te rs from 0 .0 1 6 to 0 .0 3 5 mm.

C om parison o f th e s e v a lu e s w ith m edian

d ia m e te r s and c o e f f i c i e n t s o f s o r t i n g o f n in e T a z e w e ll l o e s s sa m p les shows a m arked c o n t r a s t .

(Bee f i g . 1 5 .)

L a b o r a to r y a n a ly s e s s u p p o r t th e c o n c lu s io n drawn i n th e f ie ld th a t:

(1 ) th e T az ew ell l o e s s was d e r iv e d from a

d i s t a n t m a jo r s o u rc e a r e a , an d (2 ) th e l o e s s o f th e C ary d r i f t r e g io n was d e r iv e d from l o c a l so u rc e a r e a s .

The

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93 T & sew ell l o e s s a n a ly s e s show a s m a lle r ra n g e o f m edian d ia m e te r s and c o e f f i c i e n t s o f s o r t i n g , w h ereas th e C ary l o e s s a n a ly s e s I n d i c a t e a w id e r ra n g e o f th e s e v a l u e s . The l o e s s on th e C ary d r i f t o c c u rs a s a d i s ­ c o n tin u o u s m a n tle .

W ith in l o c a l a r e a s o f a s e c t i o n th e

d i s t r i b u t i o n i s p a tc h y .

I n many p la c e s th e l o e s s c a n n o t

be t r a c e d i n s u c c e s s iv e ro a d c u ts s e p a r a t e d by a d i s t a n c e o f no more th a n h a l f a m ile .

B ecau se o f t h i s p a tc h y

d i s t r i b u t i o n a n d th e r e g i o n a l sco p e o f th e f i e l d s tu d y no q u a n t i t a t i v e e s tim a te o f the a r e a l d i s t r i b u t i o n o f th e l o e s s can be made a t t h i s tim e ,

d e ta ile d lo c a l s tu d ie s

w i l l b e n e c e s s a r y t o d e te rm in e t h e p e r c e n ta g e o f th e C ary d r i f t t h a t i s m a n tle d by l o e s s .

P l o t t e d l o c a t i o n s on

p l a t e I I i n d i c a t e th o s e b o r in g s i n w hich l o e s s was fo u n d . T h ic k n e s s o f th e Oary and p o s t- C a r y l o e s s g e n e r a l l y v a r i e s b etw een 24 an d 36 I n c h e s .

{See p i . XX. )

S tra tig ra p h y No s e c t i o n s show ing th e e t r a t l g r a p h i e r e l a t i o n ­ s h ip o f th e C ary d r i f t to th e T azew ell o r o ld e r d r i f t s were fo u n d .

H ow ever, many s e c t i o n s h av e b een d e s c r ib e d i n th e

l i t e r a t u r e and have b een summarized by Kay an d Graham. Kay, G. F . , and Graham, J . B .f o p . c l t . f p p . £ 1 1 -2 1 7 .

94

T h ese s e c t i o n s a r e l o c a t e d I n th e d r i f t r e g io n o f th e Bem ls m o ra in e i n th e s o u th e r n an d s o u th e a s t e r n a r e a s o f th e Des M oines lo b e .

The w r i t e r b e l i e v e s t h a t th e u p p erm o st t i l l

i n e a o h o f th e s e s e c t i o n s t h a t h a s b e e n d e s ig n a te d M ankato s h o u ld b e r e c l a s s i f i e d a s C ary . P ro b le m o f t h e C o r r e l a t i o n o f th e C ary B r l f t I n th e p r e s e n t s t a t u e o f m apping o f th e P l e i s t o ­ c e n e d e p o s i t s o f th e U pper M i s s i s s i p p i R iv e r V a lle y , C ary d r i f t i s r e c o g n iz e d i n © a s t - e e n t r a l M in n e s o ta .6®

The d r i f t

f l i n t , R. F . , and o t h e r s , C l a c i a l map o f N o rth A m ericas U eo l. S oc. A m erica S p e c ia l P a p e r 60, 1945. I n n o r th w e s te r n Iowa th a t i s b e l ie v e d t o b e C ary (Bem ls m oraine) m u st b e t r a c e d a ro u n d th e Bee M oines lo b e and I n to th e a r e a o f r e c o g n iz e d C ary r e d d r i f t I n M in n e so ta . Upham®® b e l ie v e d t h a t th e r e d

[Caryj and b lu e

Upham, W arren, i n C eology o f M innesota? M in n e so ta C e o l. an d N at. H is to r y S u rv ey , v o l. 2, p p . 2 5 5 -2 5 6 , 1888. [d©s M oines lo b e]

t i l l s w ere Mco n tem p o ran eo u s and s i m i l a r

i n t h e i r f o r m a tio n , th e n o r t h e a s t and t h e w e s t p a r t s o f th e s t a t e b e in g c o v e re d by lo b e s o f th e i c e —s h e e t w h ich moved I n d e p e n d e n tly o f e a c h o t h e r .*

95

H ow ever, th e r e l a t i o n s h i p s o f th e Beral® an d A lta ra o n t m o ra in e s an d th e W isc o n sin r e d d r i f t i n t h a t a r e a w ere l a s t s t u d i e d by L e v e r e t t ? 0 , S a rd e so n ? * , an d C o o p e r? -, who b e l ie v e d t h a t th e Bemis m o rain e [ c a r y o f ?0 L e v e r e t t , F ra n k , ©p. © it, ( P r o f , P a p e r 1 6 1 ), p p . 6 1 -6 4 , 7 1 -7 4 , ?1 S a rd e s o n . F. W., i n L e v e r e t t , F ra n k , o p . © it. ( P r o f . P a p e r 1 6 1 ), p p . 7 8 -9 0 . ? 2 C o o p er, w. s . , The h i s t o r y o f th e U pper M i s s i s s i p p i R iv e r I n l a t e W isco n sin and p o s t g l a c i a l tim e : M in n e so ta G e o l. S u rv ey B u l l . 26, p p . 1 5 -1 9 , f i g s . 5 , 6 , 1935. n o r th w e s te r n Iowa] o v e rla p p e d th e W isc o n sin r e d d r i f t [Caaty o f e a s t - c e n t r a l M in n eso ta] i n th e are® o f t h e G ra n ts b u r g s u b - lo b e , and i t

T h is i s th e p ro b lem o f c o r r e l a t i o n ,

can b e s o lv e d o n ly by f u r t h e r f i e l d s tu d y o f th e

Ues M oines lo b e i n Iowa an d M in n e so ta , THE MANKATO DRIFT I n t e r p r e t a t i o n o f th e M o rain es o f th e Des M oines Lobe Kay and Graham?*5 sum m arized t h e i r I n t e r p r e t a t i o n ?3 Kay, G. F . , ©nd Graham, J . B ., The I l l i n o l a n an d p o s t - I l l l n o l a n P l e i s t o c e n e g e o lo g y o f Iow a: Iow a G e o l. b S u rv e y , v o l . 38, p . 942, 1943. o f th e Dee M oines lo b e I n a s ta te m e n t t h a t i s h e r e q u o te d :

96 The q u e s t i o n a s to th e a p p ro x im a te c o n te m p o r a n e ity o f th e s e v a r io u s m o ra in e s o f th e Bes M oines lo b e h a s n e v e r become a n i s s u e due to th e o b v io u s a r r a y o f e v id e n c e p o i n t i n g t o n o rm al s ta g e s i n th e ad v an ce and r e c e s s i o n o f a s i n g l e g l a c i a l m ass. I n m o ra in a l c h a r a c t e r s a s t o m a t e r i a l , to p o g ra p h y , p o s i t i o n , and r e d u c t i o n b y e r o s i o n ; i n a p p e a ra n c e , and r e l a t i o n o f o u tw ash m a t e r i a l s t o d r a in a g e f e a t u r e s ; i n d e g re e o f s u r f a c e t i l l m o d if ic a ti o n b y w e a th e r in g o f th e v a r io u s a r e a s o f th e lo b e ; an d i n p h y s io ­ g r a p h ic a g e o f th e v a r i o u s a r e a s o f th e lo b e , th e s i m i l a r i t i e s a r e so s t r i k i n g an d th e u n i t y o f th e e f f e c t s o f g l a c i a t i o n so a p p a r e n t, t h a t g l a c i a l g e o l o g i s t s h a v e i n g e n e r a l a c c e n te d th e s i n g l e g l a c i e r v ie w o f th e M ankato d r i f t i n Iowa an d I t s m o r a in ic com plex. H ow ever, th e map o f th e m o ra in e s o f th e Des M oines lo b e t h a t th e s e a u t h o r s p r e s e n t e d ^ was b a s e d i n l a r g e p a r t on 7^' Bay, G. P . , an d Graham,