The Glory of Regional Silurian Dolostone, Part 38: Bituminous Rock That Isn't (I Think) | Episcopal Cathedral of St. James (1857; partial rebuilding after 1871), Chicago, Illinois, USA
Detail of the base of the belltower on the church's northwestern corner. Note the water table or projecting ledge that deflects dripping water outward and away from the foundation.
To provide context for the photo above, see Part 36 and Part 37.
As glorious as Regional Silurian Dolostone usually is, there are times it doesn't look its best. Or it looks like something it really isn't.
Every source I've found for the St. James exterior stone lists it as Lemont-Joliet Dolostone (LJD), and nothing but. And yet the bituminous blobs on the water table suggest that it might not be Sugar Run Formation rock from the Lower Des Plaines Valley after all, but rather Racine Formation rock from quarries on Chicago's West Side. The Artesian Dolostone produced there was renowned for its asphaltum-spotted appearance.
However, I've come across a surprisingly large number of LJD buildings in the Windy City that in their lower reaches have been splattered in one or two places with roofing tar, sealant, or some other sort of glop that attracts and gets covered with dark soot.
It does seem that black sealant has indeed been applied in the cracks between the lowest ashlar course and the sidewalk. So perhaps someone was just really sloppy with an applicator or tarbrush.
In addition, though, there seems to be some greenish-black biofilm buildup in more recessed portions of the rock. If that's right, it's most likely cyanobacteria, though it could be Chlorophyta (green algae) instead.
This mention of biofilming leads me to reflect that the more I learn about architectural geology, the more I come to realize that the buildings we human beings regard as purely our own domain are in fact scenes of egregious microbial settler colonialism.
If one takes a truly dispassionate view of this situation, it becomes evident that we amazingly ephemeral multicellular creatures exist primarily to give this planet's dominant lifeforms the nooks and crannies and surfaces they need to thrive. We live and work to serve the ancient little ones.
The other photos and descriptions in this series can be found at Glory of Silurian Dolostone album.
And for even more on this architectural and geologically impressive building, immediately and unhesitatingly get a copy (or two or three) of my book, Chicago in Stone and Clay. Here's the publisher's description: www.cornellpress.cornell.edu/book/9781501765063/chicago-i...
The Glory of Regional Silurian Dolostone, Part 38: Bituminous Rock That Isn't (I Think) | Episcopal Cathedral of St. James (1857; partial rebuilding after 1871), Chicago, Illinois, USA
Detail of the base of the belltower on the church's northwestern corner. Note the water table or projecting ledge that deflects dripping water outward and away from the foundation.
To provide context for the photo above, see Part 36 and Part 37.
As glorious as Regional Silurian Dolostone usually is, there are times it doesn't look its best. Or it looks like something it really isn't.
Every source I've found for the St. James exterior stone lists it as Lemont-Joliet Dolostone (LJD), and nothing but. And yet the bituminous blobs on the water table suggest that it might not be Sugar Run Formation rock from the Lower Des Plaines Valley after all, but rather Racine Formation rock from quarries on Chicago's West Side. The Artesian Dolostone produced there was renowned for its asphaltum-spotted appearance.
However, I've come across a surprisingly large number of LJD buildings in the Windy City that in their lower reaches have been splattered in one or two places with roofing tar, sealant, or some other sort of glop that attracts and gets covered with dark soot.
It does seem that black sealant has indeed been applied in the cracks between the lowest ashlar course and the sidewalk. So perhaps someone was just really sloppy with an applicator or tarbrush.
In addition, though, there seems to be some greenish-black biofilm buildup in more recessed portions of the rock. If that's right, it's most likely cyanobacteria, though it could be Chlorophyta (green algae) instead.
This mention of biofilming leads me to reflect that the more I learn about architectural geology, the more I come to realize that the buildings we human beings regard as purely our own domain are in fact scenes of egregious microbial settler colonialism.
If one takes a truly dispassionate view of this situation, it becomes evident that we amazingly ephemeral multicellular creatures exist primarily to give this planet's dominant lifeforms the nooks and crannies and surfaces they need to thrive. We live and work to serve the ancient little ones.
The other photos and descriptions in this series can be found at Glory of Silurian Dolostone album.
And for even more on this architectural and geologically impressive building, immediately and unhesitatingly get a copy (or two or three) of my book, Chicago in Stone and Clay. Here's the publisher's description: www.cornellpress.cornell.edu/book/9781501765063/chicago-i...