Exploring the Baraboo Syncline Region, Part 8: Chocolate Tablets | Devil's Lake State Park, Wisconsin, USA
Looking at a rock outcrop on a wooded slope just about 0.1 mi / 0.16 km southeast of the park’s northern entrance. This locale lies to the southwest of the park road. My stylistically trend-setting headwear provides the scale at this no-hammers site.
Here I’ve continued to walk down the face of the outcrop and am now some distance from the asymmetrical folds shown and described in Part 6.
In this essay I’m building on what I’ve discussed in Part 6 (see the link directly above) and Part 7. If the technical terms used below are perplexing, refer to those posts, where I define them.
This spot in particular really highlights the alternating layers of the upper portion of the Baraboo Quartzite. This famous formation was metamorphosed into its present form around 1.47 Ga ago, in the Mesoproterozoic. Its S0 fabric consists of the deposition strata of:
- what was originally shale and mudstone transformed into phyllite, which is darker and especially favored by the lichens, and
- what originally was quartz sandstone turned into maroon metaquartzite; in this locale it's been deformed into strings of rather quadrangular “chocolate tablet” boudins.
My cap rests directly on the uppermost phyllite layer; its brim touches one of the chocolate tablets. That section of the quartzite has been bulged and stretched by tensional forces, and the more ductile phyllite has molded itself to conform to the puckers and hollows. Close scrutiny reveals a little of the S1 slaty cleavage in the phyllite, but, truth to tell, it’s much more evident in the Part 7 photo.
Main Sources Consulted for This Essay
- Dalziel, I. W. D. and R. H. Dott, Jr. Geology of the Baraboo District, Wisconsin. Information Circular No. 14. Madison, WI: Wisconsin Geological and Natural History Survey, 1970.
- Davis, Richard A. Jr., Robert H. Dott Jr., and Ian W. D. Dalziel, eds. Geology of the Baraboo, Wisconsin, Area. Field Guide 43. Boulder, CO: Geological Society of America, 2016.
To see the other photos and descriptions in this series, visit my Exploring the Baraboo Syncline Region album.
Exploring the Baraboo Syncline Region, Part 8: Chocolate Tablets | Devil's Lake State Park, Wisconsin, USA
Looking at a rock outcrop on a wooded slope just about 0.1 mi / 0.16 km southeast of the park’s northern entrance. This locale lies to the southwest of the park road. My stylistically trend-setting headwear provides the scale at this no-hammers site.
Here I’ve continued to walk down the face of the outcrop and am now some distance from the asymmetrical folds shown and described in Part 6.
In this essay I’m building on what I’ve discussed in Part 6 (see the link directly above) and Part 7. If the technical terms used below are perplexing, refer to those posts, where I define them.
This spot in particular really highlights the alternating layers of the upper portion of the Baraboo Quartzite. This famous formation was metamorphosed into its present form around 1.47 Ga ago, in the Mesoproterozoic. Its S0 fabric consists of the deposition strata of:
- what was originally shale and mudstone transformed into phyllite, which is darker and especially favored by the lichens, and
- what originally was quartz sandstone turned into maroon metaquartzite; in this locale it's been deformed into strings of rather quadrangular “chocolate tablet” boudins.
My cap rests directly on the uppermost phyllite layer; its brim touches one of the chocolate tablets. That section of the quartzite has been bulged and stretched by tensional forces, and the more ductile phyllite has molded itself to conform to the puckers and hollows. Close scrutiny reveals a little of the S1 slaty cleavage in the phyllite, but, truth to tell, it’s much more evident in the Part 7 photo.
Main Sources Consulted for This Essay
- Dalziel, I. W. D. and R. H. Dott, Jr. Geology of the Baraboo District, Wisconsin. Information Circular No. 14. Madison, WI: Wisconsin Geological and Natural History Survey, 1970.
- Davis, Richard A. Jr., Robert H. Dott Jr., and Ian W. D. Dalziel, eds. Geology of the Baraboo, Wisconsin, Area. Field Guide 43. Boulder, CO: Geological Society of America, 2016.
To see the other photos and descriptions in this series, visit my Exploring the Baraboo Syncline Region album.