Banded Iron Formation Field Trip Students in the Field Falls, known as the Niagara of the With interplanetary North, has a number of waterfalls luggage including a spectacular drop of more than 40 meters that has eroded by Jason Huberty through the upper part of the Gun- flint Iron Formation. On our first Twelve astrobiologists from the day in Canada, we surveyed a com- UW-Madison Department of Geol- plete drill core of the Gunflint at the ogy and Geophysics traveled to Ministry of Northern De- northern Minnesota and Thunder velopment and Mines Core Library. Bay, Ontario from May 19-24, 2008 We traveled up section over the for a terrestrial field trip. We set out next two days. Spectacular ribbon to observe the rocks of the Gunflint cherts and stromatolites overlain by Iron Formation in Ontario and the carbonate grainstones are seen in correlative Biwabik Iron Formation the lower units of the Gunflint. The in Minnesota. group especially enjoyed going to The over-arching goal of astrobiol- Hill Street, , Ontario, tsunami deposit. The field XRD suitcase was a big hit wherever we went. Here we analyze the microfossil outcrop at Kakabeka ogy is to understand the origin and clay minerals from devirtified volcanic glass. Falls Provincial Park where in 1954, evolution of life in the universe. Stanley Tyler (UW 1924-1963) first The earth sciences play a major role that sits atop a large anorthosite inclusion. demonstrated the existence of Precambrian because our most accessible natural laborato- In the early 1900s, the company, 3-M, mined life at 1850 Ma (picture, opposite). ries include Earth and Earth-like planets such the anorthosite for abrasives thinking it to Grainstones were a theme of the trip as we as Mars. While Mars was outside of our travel be corundum. This got a big laugh out of the saw in the days to come. Ankeritic grainstones budget, we did field test a suitcase X-ray diffrac- group. Our next stop was Temperance River with silicified stromatolites were well exposed tometer for NASA’s Mars Science Lab mission. State Park—ironic for a group of geologists. at the Current River but buried by black shales We began our trip along the north shore of We walked down to the bottom of the cliffs just a few meters away. We proceeded into examining Keweenawan rocks and saw pahoehoe, a red, oxidized ropy flow Thunder Bay and ate lunch at Hillcrest Park. of the 1100 Ma Midcontinent Rift System. top, very close to the churning spring melt Off the Lake Superior shoreline, we could see At Gooseberry Falls State Park, we looked waters gushing into Lake Superior. the Sleeping Giant Peninsula, one of the seven at amygdaloidal flow tops within the North The group crossed the Canadian border natural wonders of Canada. The peninsula Shore Volcanics. Later, we stopped at Split and camped in Kakabeka Falls Provincial Park is an outcrop of a Keweenawan age diabase Rock Overlook, famous for its lighthouse outside of Thunder Bay, Ontario. Kakabeka sill. We saw many such sills topping the older

Field Trip to Upstate New York Students in the Field Paleo group explores We were especially fortunate to have Tom historical locations Whiteley as our guide for two days. Tom is a in June highly regarded trilobite by Dana Geary specialist and the author of Trilobites of New York. Several paleo students went with my daughters We visited the Upper and me for a week of fossil collecting in upstate Ordovician Beecher New York. We visited the Paleontological Beds, north of Rome, Research Institution’s Museum of the Earth, NY. This outcrop was which we highly recommend to anyone originally discovered in traveling near Ithaca. PRI Director Warren 1892, and is well known Allmon and Education Director Rob Ross both for its exceptional Tom Whiteley and MaryRuth Kotelnicki at the Walcott-Rust Quarry site. accompanied us in the field to see and collect trilobites with soft tissues from several classic Devonian Hamilton Group exquisitely preserved describing trilobite limbs and a trilobite larval sites. by pyrite replacement. Charles Beecher of form from this site. Unfortunately, Beecher Yale University published two papers in 1893 died unexpectedly in 1904 and the exact

14 Department of Geology and Geophysics • University of Wisconsin-Madison Paleoproterozoic strata. Gunflint Iron Formation in Ontario. After a short drive through The Duluth Complex truncated residential Thunder Bay, we came these BIFs and has metamorphosed to a truly one-of-a-kind outcrop—a the Biwabik to pyroxene hornfels. tsunami deposit caused by the We started off at the United Taconite Sudbury meteorite impact. The Pit where we were able to see the Sudbury impact happened 450 Lower Cherty and Lower Slaty mem- miles to the east and 1850 million bers of the Biwabik. We ate lunch years ago. The ensuing basal at Mineview in the Sky and then surge and tsunami ripped up gi- proceeded to Northshore Mining’s ant blocks of iron formation and Peter Mitchell Mine. At this mine, the chopped-off the cabbage heads Upper Cherty and Upper Slaty mem- of stromatolites. These fragments bers of the Biwabik were exposed were then cemented along with and we could see firsthand the countless accretionary lapilli and extensive effects of metamorphism melt globules in this most unusual Kakabeka Falls Provincial Park: Gunflint Microfossils Discovery by the Duluth Gabbro. We ended conglomerate. The date 1850 Ma Outcrop of Tyler and Barghorn. Back: John Valley, Brian Beard, the long day with stromatolites and a is important as it marks the time Andy Czaja, Ian Orland, Clark Johnson, Shanan Peters, Huifang beautiful sunset. of the Sudbury impact, the end Xu, Phil Fralick and Marnie Demand. Front: Rafael Perez, Jason After our week in the Precambrian, Huberty, Amalia Doebbert, Reinhard Kozdon and Dayi Ortiz. of Lake Superior type Protero- it was time to return home and to zoic banded iron formations, and younger rocks. The group was tired in possibly the transition to a sulfidic ocean. At Vermilion district. We saw classic 2700 Ma pil- body but energized in spirit, and it is a fieldtrip a highway outcrop, the group collected our lowed greenstone, the Burntside fault, a splay none will soon forget. We have archived a own samples of the impactite including a very on the eastern end of the Vermilion fault that selection of photos on the Astrobiology home large piece that will be featured in the Geol- extends to North Dakota, amphibolite grade page on the department’s website under the ogy Museum’s new astrobiology display. migmatites, and ate lunch at the International tab “Terrestrial Field Trips” (http://www. On our third day in Canada, we continued Wolf Center. In the afternoon, the group stud- geology.wisc.edu/astrobiology/field_trips/BIF_ up section into the overlying Rove Shale. At ied the spectacularly laminated BIF at Soudan trip08/) and invite you to take the virtual trip an abandoned nickel prospect, we studied Underground Mine State Park and took the with us. Everyone involved with the trip would a large cliff exposure that showed cycles of underground tour of rocks and the massive like to thank the alumni and donors to the prodelta turbidite progradation alternating 10,000 ton MINOS neutrino detector. Student Field Experiences Fund very much for with carbonaceous-pyritic shale representing On the last day of our fieldtrip, we toured making this trip possible and for the continued delta lobe abandonment. Returning to Minne- the Mesabi Iron Range. The Biwabik Iron support of field trips in general. = sota, we examined the Archean geology of the Formation in Minnesota is correlative with the

whereabouts of this important site were lost. cott-Rust quarry while Tom Whiteley searched indefatigably for the examining Walcott’s site for many years until finally rediscovering specimens at the it in 1984. MCZ. One hundred Tom also accompanied our group to the years after the quarry Walcott-Rust Quarry near Trenton Falls, NY. was discovered, Tom This Upper Ordovician locality is also well reopened the site, known for its diverse and well-preserved which continues to trilobites. The locality was discovered in 1870 yield important finds. by 20-year old Charles D. Walcott. Walcott’s Aside from the careful thin-sectioning of specimens from this great fossils, we quarry led to some of the very first identifica- really appreciated the tions of trilobite soft parts, including gills, legs, historical aspects of and antennae. Walcott sold his specimens from the sites we visited. this quarry to the Museum of Comparative Special thanks to Zoology at Harvard University. Louis Agassiz, those who made this the MCZ’s director, later convinced Walcott trip possible through The paleo group at the Beecher Beds: George Rothdrake, Stan to pursue a career in paleontology (leading their donations to Koziarz (landowner), Carrie Levitt, John Koziarz (landowner), Markus Martin (fossil collector), MaryRuth Kotelnicki, Dana Geary, eventually to the discovery of the Burgess the Field Experiences Sarah Bleiweiss, Molly Bleiweiss, Laura Mitchell, Una Farrell (Yale Shale). Tom Whiteley learned about the Wal- Fund. = grad student), Erik Hoffmann, Ellen Whiteley. (Tom Whiteley) http://www.geology.wisc.edu 2008 The Outcrop 15