Integrative Natural History of Fayette Historic State Park, Part 10: A Beach of Broken Bedrock | Garden Peninsula, on Michigan's Upper Peninsula, USA
Standing along the Big Bay de Noc shoreline, south of the park's ghost-town site. Facing northward.
Here we have an excellent example of the crust of this manic planet being broken down and recycled. This small cliff faces west, and so suffers the full brunt of surf and storm.
Throughout this series I've mentioned the Hendricks Dolomite Formation, both in its dramatic Middle Bluff setting farther north and in its role as an important building material and smelting flux for the Fayette community. It's part of the larger stratigraphic assemblage known as the Burnt Bluff Group, of early-Silurian age.
The next Burnt Bluff Group unit down from the Hendricks is the Byron Formation. While the former was largely deposited in the deeper water of a truly marine setting, the Byron represents tidal-flat beds that were periodically exposed to the open air. This is evidenced by the presence of sedimentary features known as dessication cracks or simply as mud cracks. These are the same polygonal patterns one can find in modern sun-dried mud deposits.
As later photos in this set will show, some of the eroded rock fragments on this beach sport excellently preserved mud cracks. This suggests that the Byron is a portion of the outcrop at right, probably in contact with the overlying Hendricks.
According to one technical paper I've just come across, both the Hendricks and Byron were quarried at Fayette. This source is
Voice, P.J., W. B. Harrison III, and G. M. Grammer. "A Reevaluation of the Burnt Bluff Group (Llandovery, Silurian, Michigan Basin) from Subsurface and Outcrop Data: Development of a Time-transgressive Depositional Model." In Paleozoic Stratigraphy and Resources of the Michigan Basin, Geological Society of America Special Paper 531 (2018): 55–79.
So it does make sense that the Hendricks-Byron boundary is present here, too, only about 525 yd / 480 m farther down the coast from the old Middle Bluff quarry.
Speaking of interesting sedimentary features, nice sets of laminations (narrow layering suggesting cyclical deposition) can been seen on the outcrop, ad especially in the big slump blocks partially embedded in the erosional debris.
If it appears that my two tour participants at left are stepping rather gingerly over the broken-up beach rock, there's a good reason. Some of the pieces were slippery and flaggy; others were blockier and very easy to trip on. It's one of those places where one must keep looking downward despite the magnificent scenery in the distance.
To see the other photos and descriptions in this set, visit my Integrative Natural History of Fayette Historic State Park album.
Integrative Natural History of Fayette Historic State Park, Part 10: A Beach of Broken Bedrock | Garden Peninsula, on Michigan's Upper Peninsula, USA
Standing along the Big Bay de Noc shoreline, south of the park's ghost-town site. Facing northward.
Here we have an excellent example of the crust of this manic planet being broken down and recycled. This small cliff faces west, and so suffers the full brunt of surf and storm.
Throughout this series I've mentioned the Hendricks Dolomite Formation, both in its dramatic Middle Bluff setting farther north and in its role as an important building material and smelting flux for the Fayette community. It's part of the larger stratigraphic assemblage known as the Burnt Bluff Group, of early-Silurian age.
The next Burnt Bluff Group unit down from the Hendricks is the Byron Formation. While the former was largely deposited in the deeper water of a truly marine setting, the Byron represents tidal-flat beds that were periodically exposed to the open air. This is evidenced by the presence of sedimentary features known as dessication cracks or simply as mud cracks. These are the same polygonal patterns one can find in modern sun-dried mud deposits.
As later photos in this set will show, some of the eroded rock fragments on this beach sport excellently preserved mud cracks. This suggests that the Byron is a portion of the outcrop at right, probably in contact with the overlying Hendricks.
According to one technical paper I've just come across, both the Hendricks and Byron were quarried at Fayette. This source is
Voice, P.J., W. B. Harrison III, and G. M. Grammer. "A Reevaluation of the Burnt Bluff Group (Llandovery, Silurian, Michigan Basin) from Subsurface and Outcrop Data: Development of a Time-transgressive Depositional Model." In Paleozoic Stratigraphy and Resources of the Michigan Basin, Geological Society of America Special Paper 531 (2018): 55–79.
So it does make sense that the Hendricks-Byron boundary is present here, too, only about 525 yd / 480 m farther down the coast from the old Middle Bluff quarry.
Speaking of interesting sedimentary features, nice sets of laminations (narrow layering suggesting cyclical deposition) can been seen on the outcrop, ad especially in the big slump blocks partially embedded in the erosional debris.
If it appears that my two tour participants at left are stepping rather gingerly over the broken-up beach rock, there's a good reason. Some of the pieces were slippery and flaggy; others were blockier and very easy to trip on. It's one of those places where one must keep looking downward despite the magnificent scenery in the distance.
To see the other photos and descriptions in this set, visit my Integrative Natural History of Fayette Historic State Park album.