Exploring the Baraboo Syncline Region, Part 1: The Precarious Portal | Devil's Lake State Park, Wisconsin, USA
Taken on the southern end of the park's East Bluff. Facing northwestward.
Precarious and seemingly improbable, this picturesque jumble of jointed bedrock and loosened blocks is the Devil’s Doorway, the park’s iconic landform.
It also makes the perfect portal through which to enter this album. I hope this series will grow to many posts, for I have spent a considerable amount of time in the greater Baraboo Syncline region, and have taken many photos of it in both the film and digital eras. Here I’ve brought my college classes; here I’ve led tours for both adults and young science-camp participants. And here, in the most spiritually and intellectually productive state, I have wandered hither and yon many times, all by myself. It's a wonderful place to repair to, and to repair oneself in, when the rest of the world disappoints.
One of the chief players in this magical region’s drama is the bedrock itself. What you see here is the upper member of the purplish-to-reddish Baraboo Quartzite. Exceedingly hard, it’s just too refractory and unworkable to be used as architectural ashlar. But it has been quarried in huge quantities for boulder-sized riprap and pebble-sized railroad ballast.
Being a metamorphic rock, the Baraboo Quartzite has two benchmark ages: that of its protolith or parent rock, and that of its metamorphism. Its protolith was an exceptionally mature sandstone —that is, one made up of very well-sorted and rounded quartz grains.
It was deposited somewhere between about 1.64 and 1.51 Ga (late Neoproterozoic to early Mesoproterozoic), either at the end of the Mazatzal Orogeny or after it. In any event, later in the Mesoproterozoic it was turned into much tougher metaquartzite, during what some geologists now call the Baraboo Orogeny. That was approximately 1.46 Ga ago.
In this image, a small portion of Devil’s Lake is visible, as is one section of the West Bluff. The entire park is situated on the southern limb of the syncline, which in this neighborhood dips 12 or 13 degrees to the north-northwest.
(Need some help with the geo-jargon? A syncline is a troughlike structure in the Earth’s crust, usually cause by crustal compression. It’s V-shaped in cross section, and its rock units are folded downward in the middle. Their sides, which dip into the trough, are the limbs.
Much farther away, on the other side of the small but lovely city of Baraboo, is the range of hills that is the manifestation of the almost vertically dipping northern limb of the syncline. In cases like this, where the limbs have significantly different dips and form a decidedly lopsided V, their structure is known as an asymmetrical syncline.
Now you’re jargon-empowered for the rest of the series!
To see the other photos and descriptions in this series, visit my Exploring the Baraboo Syncline Region album.
Exploring the Baraboo Syncline Region, Part 1: The Precarious Portal | Devil's Lake State Park, Wisconsin, USA
Taken on the southern end of the park's East Bluff. Facing northwestward.
Precarious and seemingly improbable, this picturesque jumble of jointed bedrock and loosened blocks is the Devil’s Doorway, the park’s iconic landform.
It also makes the perfect portal through which to enter this album. I hope this series will grow to many posts, for I have spent a considerable amount of time in the greater Baraboo Syncline region, and have taken many photos of it in both the film and digital eras. Here I’ve brought my college classes; here I’ve led tours for both adults and young science-camp participants. And here, in the most spiritually and intellectually productive state, I have wandered hither and yon many times, all by myself. It's a wonderful place to repair to, and to repair oneself in, when the rest of the world disappoints.
One of the chief players in this magical region’s drama is the bedrock itself. What you see here is the upper member of the purplish-to-reddish Baraboo Quartzite. Exceedingly hard, it’s just too refractory and unworkable to be used as architectural ashlar. But it has been quarried in huge quantities for boulder-sized riprap and pebble-sized railroad ballast.
Being a metamorphic rock, the Baraboo Quartzite has two benchmark ages: that of its protolith or parent rock, and that of its metamorphism. Its protolith was an exceptionally mature sandstone —that is, one made up of very well-sorted and rounded quartz grains.
It was deposited somewhere between about 1.64 and 1.51 Ga (late Neoproterozoic to early Mesoproterozoic), either at the end of the Mazatzal Orogeny or after it. In any event, later in the Mesoproterozoic it was turned into much tougher metaquartzite, during what some geologists now call the Baraboo Orogeny. That was approximately 1.46 Ga ago.
In this image, a small portion of Devil’s Lake is visible, as is one section of the West Bluff. The entire park is situated on the southern limb of the syncline, which in this neighborhood dips 12 or 13 degrees to the north-northwest.
(Need some help with the geo-jargon? A syncline is a troughlike structure in the Earth’s crust, usually cause by crustal compression. It’s V-shaped in cross section, and its rock units are folded downward in the middle. Their sides, which dip into the trough, are the limbs.
Much farther away, on the other side of the small but lovely city of Baraboo, is the range of hills that is the manifestation of the almost vertically dipping northern limb of the syncline. In cases like this, where the limbs have significantly different dips and form a decidedly lopsided V, their structure is known as an asymmetrical syncline.
Now you’re jargon-empowered for the rest of the series!
To see the other photos and descriptions in this series, visit my Exploring the Baraboo Syncline Region album.