The Quaternary Stratigraphy and Glacial History of the Duluth
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i . , .. 'Jhi torrtpkiton & this 1}LtStz .suypo-r-tzd 1\an4y fiward . in :his ft'i.ef1tOYE 1 °fo attotJteY ouhiartdt:Jtf:j s:r11ditate sittdt:itt . t}tt Gto 1o,,qB 1)ltpaA1rtt:1tt, 1bttvets1t,,y tf 1rltn1te$ofa1 l)u1uti of Univer o.itv of .Minnesota. Dulutli THE QUATERNARY STRATIGRAPHY AND GLACIAL HISTORY OF THE DULUTH-SUPERIOR AREA A THESIS SUBMITTED TO THE FACULTY OF THE GRADUATE SCHOOL OF THE UNIVERSITY OF MINNESOTA BY PATRICK MICHAEL LANNON IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE NOVEMBER 1986 ABSTRACT Three major lithostratigraphic units of Pleistocene age are exposed in the Duluth - Superior area, all of which are the result of Late-Wisconsin glacial activity. The lowermost unit, a reddish-brown, sandy-textured diamicton (sand/silt/clay ratio: 52/38/10) containing abundant clasts of Precambrian red sandstone, is interpreted to be subglacial till of the Lower Cromwell Formation, which was deposited by the Superior lobe during the St. Croix phase of glaciation approximately 20,000 years B. P. Its main exposure within the study area is at the base of stream valleys and roadside cuts in the southern portion of the Eska Quadrangle. Overlying the Lower Cromwell Formation is a very compact reddish-brown, silt-rich diamicton (sand/silt/clay ratio: 30/43/27_) interpreted to be subglacial till of the Upper Cromwell Formation, which was deposited by the Superior lobe during the Automba phase of glaciation, approximately 14,000-18,000 years B. P. This unit is the dominant stream valley and roadside exposure in the southern portion of the Eska Quadrangle. The Upper Cromwell Formation also contains a supraglacial facies composed of flow tills and outwash s ediments deposited during the i retreat of Automba phase ice. These flow tills have been previously interpreted as subglacial tills associated with a later "Split Rock" advance. This supraglacial facies is the dominant surficial deposit in the northern portion of the Esko Quadrangle. The youngest lithostratigraphic unit grades verticall y from a basal laminated silt and clay into massive r ed clay in its upper portions, and grades laterally into sands and gravels. Topographically, it is confined to elevations below 1115 feet, and is found throughout the southern portion of the Esko Quadrangle and most of the Berea Quadrangle. Based on its areal extent, facies relationships, grain-size trends, stratigraphic relationships, geomorphic expression, sedimentary structures, and engineering properties, the entire unit is interpreted to be glaciolacustrine sediment and is assigned to the Wrenshall Formation. It was deposited in Glacial Lake Duluth approximately 10,000 years B. P. The massive clay facies of this unit is not the equivalent of the Douglas Till Member of the Miller Creek Formation deposited during a late-glacial ice expansion referred to as the "Marquette" phase approximately 9900 years B. P. That advance affected portions of northern Wisconsin and Upper Michigan, but did not reach as far southwest into the Superior Basin as the Duluth - Superior area. ii ACKNOWLEDGEMENTS This study was funded in part by a grant from the Department of Geology, University of Minnesota - Duluth. Many people have assisted with this study, including numerous property owners, geological survey staff members, state department of transportation workers, and various county officials. A special thanks is extended to each one. Assistance in the field was provided in part by Colin Reichhoff, Doug Davis, and John Heine. A special thanks is extended to Beth Moyer of RREM Engineering, Inc. for drafting many of the figures; to Glenn Evavold, for his help in many aspects of this study (and for being a very understanding employer); to Mary Nash and Joan Hendershot of the geology department (who serve as every graduate student's unofficial "secondary advisors"); to the geology department faculty, who were always willing to help in any manner needed, especially Dr. John Green, who reviewed and offered very helpful suggestions for the manuscript; and finally, to my thesis committee members - Dr George Ahlgren (Biology), Dr. Dave Darby, and most of all, to my advisor, Dr. Charlie Matsch. Lastly, I want to thank my parents for all they have done for me. It is to them that I dedicate this thesis. iii TABLE OF CONTENTS ABSTRACT • •••••••••••••••••••••••••••••••••••••••••••.••••••••••• ... i ACKNOWLEDGEMENTS • ••••••••••••••••••••••••••••••••••••••••••••••••••• iii TABLE OF CONTENTS . ....•....••.•••..••.••......•••.•••........••••.••• iv LIST OF ILLUSTRATIONS ..•.•••••••••••••.••••.•••..•.•..•...•.••...•••• vi Figures •• .vi Plates. .vii Tables. .vii INTRODUCTION . ................................................... ........ 1 Location ..•............ •••••••••• 1 Field Methods ..••...••• . ...... 3 Laboratory Methods ••.• . ... 3 Bedrock Geology .••.••• • • 4 Previous Work and Problems ••• • • 4 QUATERNARY STRATIGRAPHY AND SED TI1ENTOLOGY ••••.••••••..•......•••••••• 12 Introduction •••••••...•••••••••••••.••••••.••••• • 12 Quaternary Stratigraphy of Northeast Minnesota •• • 12 Till Genesis .••••. • •• 16 Till Units •••••••• . •• 20 Possible Pre-St. Croix Phase Unit. ..20 General Characteristics ••••••••• . .•.... 20 Origin and Regional Correlation • . 22 Lower Cromwell Formation •••••••••• . 24 General Characteristics ....•...••••.....••....••.•.....••..•. 24 Origin and Regional Correlation •••••••••••••••••••••••••••••• 31 Upper Cromwell Formation: Subglacial Facies •••••••••••••••••••• 31 General Characteristics •••.••••. .31 Origin and Regional Correlation. .34 Upper Cromwell Formation: Supraglacial Facies •••••••••••••••••• 35 Site-Specific Characteristics •••••••••••••••••••••••••••••••••• 38 Glaciolacustrine Units ••••••••••••••••••••••.••••••••••••••••.••• 46 Wrenshall Formation: Shallow-Water Facies •••••••••••••••••••••• 46 Wrenshall Formation: Bedded Silt and Clay Facies ••••••••••••••• 55 General Characteristics ..•..•.•..........••.....••.•••.....•• 55 Origin and Regional Correlation •• ............... 57 iv • • • • · • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •••••••••••••••• •Page Wrenshall Formation: "Massive Red Clay" Facies ••••••••••••••••• 60 General Characteristics •••••••••••••••••••••••••••••••••••••• 60 Criteria used to determine the origin of the red clay •••••••• 65 Areal Extent .. ............................................. 66 Facies Relationships and Grain Size Trends ••••••••••••••••• 68 Stratigraphic Relationships ••••••••••• .- •••••••••.•••.•••••• 70 Geomorphic Expression •••••••••••••••••••• .................. 70 Fabric . ..................... 7 3 Sedimentary Structures ••••••• • 76 Fossils .. ................... .78 Engineering Properties (Bulk Density, Consolidation) •• .79 Origin and Regional Correlation •••••• .82 Depositional Model ••••••••••••••••••• . .• 82 Other Quaternary Sediments ••• . ............ 86 Introduction ••••••••••••••• . ....•.....•.•... 8 6 Deposits of the Nickerson Moraine •••••••• . ......... 86 Sublacustrine Outwash •••••••••••••••• . ......... 87 Holocene Alluvium ••••.•••••.••. .......... 88 LATE WISCONSIN AND HISTORY. .89 Introduction . ............................. .89 History of Late-Wisconsin Glaciation ••••. • •• 90 Pre-St. Croix Phase . ................... .90 St. Croix Phase •• • •• 90 Automba Phase ••.• • • 91 Split Rock Phase. • • 93 Nickerson Phase •• ,95 Agassiz Phase •••• • • 95 Problems With the Late-Glacial Sequence of Events •. • . 97 Post-Glacial History •....•...........•.....•........... • •••••• 101 REFERENCES • ••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 10 6 APPENDIX A •••••••••••••••••••••••••••••••••••••••••••••••••••••••••• A-1 APP END IX B . •.••.•..•••••.•••.••••••••.••••••••••.••..••.•.•••.••.••. A-3 v LIST OF ILLUSTRATIONS Figures 1 • Location Map . •..•.•.•..••..•.....•..•••...•.•· •.•..••.•..•..••..•.. 2 2. Bedrock Geology . .................................................. 5 3. Post-Nickerson Ice Margins ••.•••.••••••••••••••••••••••••.•••.••• 11 4. Quaternary Stratigraphy of Northeastern Minnesota .•.•.••.••.•.•.• 14 5. Depositional Model for Multi-layered Sequences .••••••..••.••••••• 21 6. Cobble Lithology of Tills ••.••••••.•.••.•••••••••..••.••••••.•.•• 23 7. Lower Cromwell Formation XRD . ....•...............•............... 27 8. Cromwell Formation Fabric Diagrams ••..•.......••.••...•••••.•..•. 30 9. Upper Cr omwell Formation XRD .•...••..••.•....•••••.••.••••••••••• 33 10. Upper Cromwell Format ion Textural Diagram •.••.••.•.•••••.....•.•. 36 11. Upper Cromwell Formation (Supraglacial Facies) Fabric Diagrams ••• 37 12. Exposure of Till Un i ts in Jay Cooke State Park •••••••.••••••.•.•• 40 13. Supraglacial Ridge-Development Model ••••••••••••••.•••.•.••••..•• 43 14. Exposure of Wrenshall Formation in Jay Cooke State Park •••••••••• 45 15. Cross-bed Measurements from Lagro Pit •••••••••••••••••••••••••••• 49 16. Proctor Stratigraphic Section ••••••••••.•••••••.••••••••••.•••••• 51 17. Proctor Diamicton Fabric Diagram ••••••••••••••••••••••••••••••••• 53 18. Wrenshall Formation Gray Silt XRD •••••••••••••••••••••••••••••••• 58 19. Wrenshall Formation Red Clay Grain-size Curve •••••••••••••••••••• 62 20. Wrenshall Formation Red Clay XRD •••.••••••••••••••••••••••••.•••• 63 21. Facies Assemblage of Zarth (1977) •.••.••••••.•••••••••••••••••••• 69 22. Depositional Model for the Red Clay •••••••••••••••••••••••••••••• 85 23. Sub-lacustrine Moraines in Western Lake Superior •••••••••••••••• 100 vi Figures Page 24. Schematic