Geological Survey Professional Paper 754-A Glacial and Postglacial Geologic History of Isle Royale National Park, Michigan

Cover

Abstract

Introduction

Historical background and acknowledgments

Direction of ice movement

Bedrock geology and its control of preglacial topography

Modification of topography by glacial erosion

Modification of topography by glacial deposition

General distribution of glacial deposits
Drumlins
Ice-margin deposits

Post-Valders lake stages in the Lake Superior basin

Abandoned shorelines on Isle Royale

Significance of ice-margin deposits on Isle Royale

References cited

PLATE

1. Map showing glacial features and abandoned shorelines, Isle Royale National Park, Keweenaw County, Michigan (omitted from the online edition)

FIGURES

1. Map of the Lake Superior region

2. Map of Wisconsin ice retreat from central North America

3. Shaded-relief map of Isle Royale National Park

4. Sketch of the relation between ridge-and-valley topography and tilted lava flows and sedimentary rocks

5—8. Photographs of:

5. Glacial striations

6. Glacially rounded and striated outcrop

7. Spheroidal-weathering zone in a basalt lava flow

8. Granitic erratic near summit of Feldtmann Ridge

9. Stereoscopic pair showing drumlins, ice-margin deposits, and abandoned shorelines west of Siskiwit Bay

10. Map of glacial Lake Duluth and contemporary ice border

11. Diagram of water-level change and suggested intervals of ice retreat for the Lake Superior basin

12. Map of glacial Lake Minong and contemporary North Shore ice border

13. Diagram of chronology of lake-level changes in the Lake Superior basin

14. Diagram of profiles showing former water planes in northwestern Lake Superior basin

15. Diagram of profile across barrier-bar beaches between Rainbow Cove and Feldtmann Lake

16. Sketch of wave-cut shoreline illustrating development of stacks and arches

17. Photograph of Monument Rock, a stack associated with the shoreline of glacial Lake Minong

18. Photograph of wave-cut arch on Amygdaloid Island

19. Map of hypothetical position of glacial ice margin prior to complete retreat of ice from Isle Royale