Monday, May 28, 2018

Pictures At An Exhibition 4

Today I’m returning to my Pictures At An Exhibition. In case you haven’t read part 1, here’s the link

This time we’ve moved on to the late Silurian, specifically in Chicago in Cook County Illinois about 425 million years ago. It’s only fitting that the paintings depict one of the few faunas known from the area of the museum itself, and the very brief Silurian period is well-represented in the Field Museum’s fossils. Indeed, the fossil collection began with mostly local geology from this period, and until 1990 there was a hall of Paleozoic fossils and dioramas in the museum.  As of now, they still have a corner in the Evolving Planet exhibit. Above the fossils of the Chicago region and a diorama of a Silurian reef is Charles Knight’s depiction of the city to which he dedicated this work of art. 

Like the previous Ordovician mural, this depicts a coastline, with both land and sea depicted and no animals seen swimming.  However, as the Ordovician mural, marine animals are nevertheless present. In this case, it’s the coral reefs. Despite the massive extinction event that began the Silurian and the three minor extinctions that followed, the last two during the Ludlow epoch, corals still prevailed.  In these extinctions, the temperature dropped, and with it the sea level. This is depicted in the mural as the reefs protrude from the surface, exposed to the air.

This may be the most colorful of the Paleozoic murals-the corals are maroon and white, with drifts of algae and seaweed adding green to the bright blue ocean. My knowledge of corals is limited, so I cannot comment on which species are being represented.  The background has rock formations, sea, and a cloudy sky, with a peninsula on the horizon, much like the Ordovician mural. The geological evidence does suggest that Chicago was a tropical bay with a coral reef, so this depiction is still accurate. 

It is interesting that in the Paleozoic murals, the coast is depicted and not marine ecosystems. It’s not a question of knowledge-by 1930 the fossils of the Midwest marine faunas were well-known and catalogued. It’s not a question of ability-Knight repeatedly depicted these faunas in other murals for New York and National Geographic.  It might have been time constraints-on the other hand, he had the time to depict the sea creatures of the Ordovician and the coral reefs of the Silurian. It could simply be a creative choice-there are no underwater scenes at all in this series, and he wanted thematic continuity to match stylistic and palette continuity.

One more note- the Silurian seen here represents the Thorton Quarry Reef site, dating to the Niagara formation in the late Silurian.  This quarry has provided a great deal of stone for the local area, and so local collectors have found thousands of specimens from this region, including the aforementioned collection in the Field Museum.  For more on the reef, the Milwaukee Public Museum has a website on it:

I apologize for the short essay-it comes down to my ignorance of the subject matter.

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