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The Mid-continent Rift of Wisconsin and Michigan


The Mid-Continent Rift of Northwest Wisconsin and the Keweenaw Peninsula of Michigan   



This trip will survey the geology and the mining history of the mid-continent rift outside of Minnesota. Our trip will begin on the north limb of the rift exploring the most southern outcrops of the rift basalts inWisconsin’s Interstate park. At Pattison and Amnicon Falls State parks we will view a rift forming fault, the Douglas fault and three waterfalls. Next, on the Bayfield Peninsula and Apostle Islands we will examine the mid-Proterozoic rift filling sandstones of the Bayfield and Oronto groups.

We will then move to the south limb of the rift. This side of the rift is more steeply dipping and more mineralized than the north side of the rift in Minnesota. The rift on the Keweenaw Peninsula was historically a major copper mining district. We will observe the volcanic rocks of the rift at Copper Falls, the Porcupine mountains, and the Keweenaw Peninsula. We will also examine a gabbro intruded into the volcanic rocks, the Mellen gabbro. On the Keweenaw we will visit a few historic mines. The trip will end with the Copper Country Rock and mineral club annual rock show.

If you might be participating on this trip please send an email indicating your level of interest to to get on the mailing list for further updates. Reservations for overnight lodging are recommended since the trip is during the main tourist season for the region. If you want to participate in the optional prepared mine dump collecting see the following web site and be sure to register soon:


Further details and revisions will be forthcoming by email to those who have replied to the MSN Hotmail address above.


Leader: Randy Strobel


Dates: August 6- 12, 2011. August 13 and 14 are not formally part of the trip.


Trip Fees


There will be no charge from the GSM for the trip. However, participants will be responsible for paying admission charges at each of the venues that we will be visiting. The charges are listed in the agenda below. Please plan on having $8 cash at the Delaware Mine and $12.50 at the Quincy Mine available so that we can write a single check and take advantage of the group rates.



Things to bring you might not have thought of


    • Family radio (FRS) radio tuned to channel 9. Some of these will be available, but bring your own if you have one. We will use these as amplifiers at the stops, to facilitate car caravanning and finding lost cars, and to narrate the roadside geology while traveling.

    • If you bring a rock hammer be sure to bring safety glasses and wear them when you are using it. Steel toed boots are also recommended.

    • Metal detector if you have one. Don’t buy one special for the trip though.

    • At least one change of warm clothes for the underground mine tours. Long pants are usually required. Sandals and open toed boots are not allowed. They also request that you wear boots, steel-toed if you have them.

    • A compass is useful for staying oriented in the field, measuring the strike of rocks, and if it has a clinometer (recommended) the dip.

    • A road map of Wisconsin. We can pick up Michigan road maps at the border crossing into Michigan.


Final Agenda

 Monday August 1

  Organizational meeting   7-9 pm

    • GSM Waivers will be available, and can be signed at this time or later.



Randy Strobel and Joan Furlong's house

54 East Sandra Lee Drive

Saint Paul, MN 55119




Short overview of Midcontinent rift geology


Observation of rocks collected in the field areas we will be visiting


Discussion of logistics


Signing of waivers


Chance to arrange car-pooling


    • If you cannot make this meeting and plan on attending the trip please let Randy Strobel know.


Saturday August 6


    • Meet at 9 am at the Ice Age Interpretive Center, Wisconsin Interstate Park.

      • Skyline Trail (0.2 miles). Contact of Cambrian Franconia formation and Chengwatana basalts.

      • Eagle Peak Trail (0.8 miles). Bedrock island in Cambrian Sea.

    • Summit Rock and Echo Canyon trails at Interstate Park. (0.7 miles). If time permits.

    • Lunch at Lake of the Dalles picnic area

    • Pothole Trail at Interstate Park (0.4 miles)

    • Riverside landing, St. Croix River. (If time permits)


    • Pattison State Park Wisconsin. Two waterfalls including the largest in Wisconsin. Evidence of historic copper exploration. Evidence for the presence of the Douglas fault.  

      • Wisconsin State Park vehicle sticker required ($10.00/car daily or $35.00/car annual).

    • Amnicon Falls State Park Wisconsin. Douglas fault up close at two sites.

    • Overnight




Sunday August 7:


      • Meet at boat dock in Bayfield at 9:00 am.

      • Anti-nausea medication is recommended if you are prone to seasickness. This should be taken prior to departure.

      • Cruises are weather dependent and occasionally cancel. If weather prevents us from doing the cruise, we will do part of the Monday agenda on Sunday and try again on Monday.

    • Lunch at Big Rock Wayside park

    • Exposures of Proterozoic rift-filling sandstones

      • Chequamagon sandstone at Big Rock Wayside Park

    • Cornucopia beach

      • Flume experiment at well if time permits and we do not have to compete with children on the beach. Bring a small gardening spade if you have one.

    • Lake Superior coast geomorphology

    • Overnight (day two at this site)

      • Recommended camping overnight at Memorial Park in Washburn

      • Numerous motels in Ashland, Washburn, or Bayfield




Monday August 8:



    • Copper Falls State Park Wisconsin. 1.5 mile “Doughboy’s” geology hiking trail.

    • Lunch at Copper Falls State Park


    • Overnight

      • Options for lodging close to the Porkies is either Iron River (lots of motels), Bessemer (two motels) or Wakefield (one odd pink motel), Michigan. The Northwoods motel is recommended




Tuesday August 9:


    • Meet at 9 am at the Presque Isle Falls parking lot. Meet at the parking lot at the end of the South Boundary road, which is northward extension of Gogebic county 519 into the park. Maps will be distributed the day before.

      • Early lunch at picnic ground adjacent to parking lot                                      


    • Overnight

      • Optional evening hike on Overlook Trail or Cloud Peak Trail (3 miles)




Wednesday August 10:


    • Adventure Mine Tour, Ontonagon Michigan

      • Meet at 9 am.

      • Trammer’s Tour ($12.50/person) or Prospector’s Underground Tour. ($23.50/person).  

    • Roadcuts of Copper harbor conglomerate and Portage Lake Volcanics

    • Lunch at Hancock Recreation area

    • Keweenaw Waterway Overlook  


    • Quincy Hill Mine Tour (surface and below ground)

      • Full tour price $15.00/person.

    • Overnight

      • Optional Copper Country Rock and Mineral Club Swap event at 5 pm at Quincy Hill 




Thursday August 11:


    • Meet at Keweenaw National Historical Park headquarters at 9 am or 10 am (will be announced depending on ranger’s availability). Located at Highway 41 and Red Jacket Road in Calumet. A ranger led tour is pending and is likely. The NPS is short staffed right now and waiting to see what happens with the federal debt ceiling. However, we will self guide if it does not work out.


    • Geology/Mining/Historical road tour of Keweenaw peninsula, SW to NE

      • Bumbletown Hill (Portage Lake Volcanics and Allouez gap)

      • Eagle River Waterfalls. Contact of Portage Lake Volcanics with Copper Harbor Conglomerate.

      • Eagle River Beach.  

      • Esprey Park

      • Beach 2 miles south of Copper Harbor. Massive outcrop of Copper Harbor Conglomerate.


    • Overnight



Friday August 12


      • Large boulder of native copper in matrix in parking lot

      • Opportunity to purchase samples of local native copper and copper minerals


    • Road tour of Keweenaw Peninsula continued, NE to SW

      • Jacobsonville sandstone

      • Stamp mill ruins (Tamarack), Quincy smelter ruins (Ripley) and stamp sands (Gay).

      • $8.00/person

    • End of formal trip

      • Optional camping at Hancock city campground

      • Copper Country Rock and Mineral Show is open until 6 pm


Saturday August 13 and Sunday August 14


    • Numerous activities in Houghton/Hancock area sponsored by Copper Country Rock and Mineral Club

      • Free Rock and Mineral Show

      • Open house at Keweenaw Gem and Gift Shop. Free cleaning and cutting of any treasures you have found.

      • Collecting at old mine sites (pre-registration and additional fees required)



Reviews of Midcontinent Rift Geology



These links will provide a broad overview of the geology we will be seeing in the field.,+Michigan



Geological Maps


A single copy of maps 1, 2, and 4 will be used on the trip. An alternate map will be used in place of map 3. You may order your own maps at if you wish for $9/map.



1) Pattison and Amicon falls   available



2) Cornucopia, Bayfield, and Porcupine Mountains west available



3) Porcupine mountains east  out of print



4) Keweenaw available