General Features .......................................................12 Interpretation..............................................................15 Lenticular Sandstone Facies ................................. 15 General Features .......................................................15 Sedimentary Structures..............................................15 Bedding..................................................................15 Channel Structures ................................................15 Cross-Bedding .......................................................16 Other Structures.....................................................18 Interpretation..............................................................18 Massive Sandstone Facies.................................... 19 General Features .......................................................19 Sedimentary Structures..............................................19 Bedding..................................................................19 Ripple Marks ..........................................................19 Interpretation..............................................................19 Frontispiece. The Munising formation exposed in the cliffs of Pictured Rocks. Red Siltstone Facies.............................................. 19 The Pre-Jacobsville Erosional Surface ........................20 STATE OF MICHIGAN Paleogeography ...........................................................21 DEPARTMENT OF CONSERVATION Location of the Source Area.................................. 21 GEOLOGICAL SURVEY DIVISION Nature of the Source Area..................................... 23 Publication 51 Age and Correlation .....................................................24 THE CAMBRIAN SANDSTONES Factors Favoring Keweenawan Age ..................... 24 Evidence Opposing Keweenawan Age ................. 25 of Conclusion............................................................. 26 NORTHERN MICHIGAN The Pre-Munising Erosional Surface ...........................26 Surface in Alger County ...............................................26 BY WM. KENNETH HAMBLIN Surface in Dickinson County........................................26 Munising Formation.......................................................28 A dissertation submitted in partial fulfillment of the requirements for the degree of Basal Conglomerate.....................................................29 Doctor of Philosophy in the Composition........................................................... 29 University of Michigan Texture................................................................... 30 1958 Origin ..................................................................... 30 Chapel Rock Member ..................................................31 Composition........................................................... 31 Contents Heavy Minerals...................................................... 32 Texture................................................................... 33 Foreword.......................................................................... 3 Color ...................................................................... 33 Introduction ..................................................................... 4 Sedimentary Structures......................................... 33 Cross-Bedding ...........................................................33 Purpose and Scope of Investigation.............................. 4 Mud Cracks................................................................34 Location ......................................................................... 4 Ripple Marks ..............................................................34 Field Work and Methods................................................ 4 Tracks ........................................................................34 Concretions................................................................35 Acknowledgments ......................................................... 5 Clastic Dikes ..............................................................35 Previous Work ............................................................... 5 Clay Pellets ................................................................36 Physiography................................................................. 7 Contact Between the Chapel Rock and Miner's Highlands of Keweenaw Peninsula .........................8 Castle Members .................................................... 36 Precambrian Highlands............................................8 Paleogeography .................................................... 37 Eastern Lowlands ....................................................8 Analysis of Cross-Bedding .........................................37 Ripple Marks ..............................................................37 Jacobsville Formation .................................................... 9 Shape of the Chapel Rock Member ...........................37 General Description....................................................... 9 Miner's Castle Member ................................................39 Areal Extent .............................................................9 Composition........................................................... 39 Thickness.................................................................9 Heavy Minerals...................................................... 39 Composition ...........................................................10 Texture................................................................... 40 Heavy Minerals ......................................................10 Color ...................................................................... 41 Texture...................................................................11 Sedimentary Structures......................................... 41 Color.......................................................................11 Cross-Bedding ...........................................................41 Description of Facies ................................................... 12 Bedding......................................................................41 Conglomerate Facies.............................................12 Mud Cracks................................................................42 Ripple Marks ..............................................................42 Publication 51 – Page 1 of 55 Concretions ................................................................42 Figure 17. Axial section of fluvial trough cross-bedding. .......18 Paleogeography.....................................................42 Figure 18. Horizontal section of fluvial trough cross- Analysis Of Cross-Bedding.........................................42 bedding. .........................................................................18 Ripple Marks ..............................................................43 Age And Correlation...............................................43 Figure 19. Transverse section of simple trough type cross- bedding. .........................................................................18 Au Train Formation ....................................................... 44 Introduction.................................................................. 44 Figure 20. Massive sandstone facies, Victoria Falls..............18 General Description..................................................... 45 Figure 21. Jacobsville-Precambrian contact, Presque Isle....20 Age And Correlation .................................................... 46 Figure 22. Jacobsville-Keweenawan contact, Sturgeon Structure ........................................................................ 46 Falls. ..............................................................................20 General Attitude Of The Bedding ................................ 46 Figure 23. Details of contact at Sturgeon Falls .....................21 Keweenaw Fault .......................................................... 47 Figure 24. Weathered zone between Jacobsville and Normal Faulting ........................................................... 48 Keweenawan basalts .....................................................21 Minor Thrust Faults...................................................... 48 Figure 25. Weathered zone between Jacobsville and Joints ........................................................................... 48 Precambrian granite.......................................................21 Clastic Dikes................................................................ 49 Figure 26. Block diagram of fluvial trough cross-bedding.....21 Composition ...........................................................50 Figure 27. Relation of fluvial trough cross-bedding to stream Summary Of Geologic History..................................... 51 channel...........................................................................21 Conclusions ................................................................. 52 Figure 28. Relationship between stream pattern and the standard deviation of the direction of stream flow. .........22 Bibliography .................................................................. 53 Figure 29. Cross-bedding directions in the Jacobsville formation. .......................................................................23 Illustrations Figure 30. Isopach map of the Munising formation. ..............23 Figure 31. Gravity anomaly map of Northern Michigan. ........24