IC14. Geology of the Baraboo District, Wisconsin: A description and ...

Remarks : This is an excellent place for students to study festoon cross
stratification three-dimensionally. Also it is a fine locality
for them to make a paleogeographic interpretation before they
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have seen thenearby quartzite in situ. As at several other
localities, some of the largest quartzite boulders can stimulate
a debate over whether they are, in fact, boulders or the tops
of buried hills. The stratigraphic facing direction criteria
within the boulders (e.g., truncated tops of cross sets) in com-
parison with the main synclinal structure provide a clue.
SUPPLEMENTARY STOP M -- Eastern Closure
Locat ion: *, Sec. 26, T.l2N, R.8E. The top of the eastern extremity of
the Baraboo Ranges above Interstate 90/94.
Access : Continue north on Beich Road from Supplementary Stop L. Turn
right (north) at junction with County W (1.0 mile) and right
again (east) on Rowley Road (after .3 mile). Drive to the end
of Rowley Road (another 1.5 miles). The outcrops at this locality
can be seen-$ mile north of the farmhouse across the field. At
the time of writing, there was an access problem at this locality.
The property was part of an estate being settled and no one lived
there, but the local sheriffwasapt to greet you on your return to
your car! This will hopefully clear up soon, but it is best to
check at the farm 1/3 mile west at the turn to Sky High Campground.
Features to
be Seen: The quartzite can be traced around the east-closing and west-
plunging (20-30°) hinge of the Baraboo Syncline by following the
strike for a few hundred yards to the north and east. Quartzite
cleavage (Sl ' ) is prominent, dipping north at 35-55O rough1 y
parallel to the axial surface of the syncline. Displacements
of the bedding along the cleavage are clearly visible near the
southern edge of the group of outcrops. There seems to be more
than one penetrative quartzite cleavage present, but only one
(identified here as Sll) can be consistently recognized. At
the southern edge of the outcrop, there are potholes on the
surface of the quartzite. One is lined with brown-weathering
arenaceous sediment of lower Paleozoic type, and these are
therefore likely to be Cambrian or Ordovician potholes. Once
again, the present topography is coincident with that of the
Cambrian. Please use restraint with rock hammers.
Remarks : The question of there being more than one cleavage in the quartzite
arises in a number of localities around the syncline (see
'1
STOP 2, Supplementary Stops B and Dl. In some places a second
quartzite cleavagev1 probably is only late-stage local jointing
unusually closely spaced. Elsewhere one may be observing a surface
developed at a particular stage in the fold history due to local
heterogeneities.