Tentative Schedule

• Monday, May 17 - Depart Madison @ 2 p.m. (or people can meet us in Marquette)
  
  
• Monday May 17 - Arrive Marquette @ 8 p.m., (late dinner; motel, Marquette)
  
  
• Tuesday, May 18 - All day in the field (Marquette area); (dinner; presentations, Marquette)
  
  
• Wednesday, May 19 - Half day in the field (Republic). Depart mid-day; return to Madison
  
  
• Wednesday, May 19 - Arrive Madison @ 6 p.m. Conference starts in Madison

Tentative Stops

Day 1:

• Harvey Quarry (keel border fault; Kona stromatolites; Rte. 41, just S of Marquette)
  
  
• Unconformity along lake shore, Rte 41 (Paleozoic sandstone over Menard)
  
  
• Lighthouse Point, Marquette (dikes and greenstone)
  
  
• Wetmore Landing (lakeshore granite exposures, NW of Marquette)
  
  
• Siamo Slate (slate; clastic dikes; west of Marquette)
  
  
• Jasper Knob (folded BIF; Ishpeming)

Day 2:

• Granites and shear zones (en route to Republic)
  
  
• Gneiss and migmatite (near Republic)
  
  
• Transposed high-grade Marquette Supergroup (near Republic)
  
  
• Republic Pit overlook

The purpose of this trip is to illustrate the enigmatic structure of the dome-and-keel terrane within the 2.0 - 1.8 Ga Penokean orogen. In this terrane, "basement" composed of Archean felsic to intermediate crystalline rocks (TTG gneisses, granitoids, and migmatites) occur in dome-shaped bodies which are juxtaposed, along shear zones, against steep-sided troughs containing Paleoproterozoic strata (including BIF). These strata are metamorphosed along the shear zones that form the contact between domes and keels. While the Penokean dome-and-keel province architecturally resembles dome-and-keel provinces of well known Archean granite-greenstone belts, such as the Pilbara of Australia and the Abitibi of Ontario, it differs from them in that the rocks of the Penokean domes are over half-a-billion years older than the rocks of adjacent keel, whereas the greenstones and "granites" of Archean dome-and-keel terrranes are similar in age to each other.

The Penokean dome-and-keel terrane appears to be a consequence of extensional collapse of a Paleoproterozoic collisional orogen. Notably, the architecture of this province differs markedly from that of Cenozoic Cordilleran metamorphic core complexes, even though both developed during extensional tectonics—the differences may reflect long-term secular change in crustal stratigraphy and heat flow. During this field trip, we will examine structural, stratigraphic, and geochronological features of the Penokean dome-and-keel province in the region between Marquette and Republic, in northern Michigan. The field area lies between two sub-parallel sutures (Archean Great Lakes and Penokean Niagara tectonic zones) along the southern edge of the Superior Province of the Canadian Shield.