JACKSON HOLE, WYO – How many Wyomingites have likely driven right past the big manmade hole near the summit of South Pass without noticing it or certainly without knowing its backstory? It’s right there on State Highway 28, between Farson and the junction with US 287 south of Lander.
The hole is clearly manmade and is now full of water. Most assume it is a reservoir of some kind. Some have perhaps stopped at the roadside sign to learn more about this ‘hole.’ Now, for the rest of the story, attend Chuck Dahl’s presentation on Wyoming’s Atlantic City iron ore mine atop South Pass.
Dahl is a member of Geologists of Jackson Hole. More importantly, Chuck was instrumental in the discovery and development of this mine. There are few people better suited to tell the tale of this hole than Dahl.
Geologists had known for years—as far back as 1911, probably—about the existence of iron deposits in the Goldman Meadows Formation but the interest was primarily gold and silver in the Atlantic City/South Pass region. Miners had the fever.
It wasn’t until the Japanese bombing of Pearl Harbor on December 7, 1941, that the nation would soon be very interested in the Precambrian iron deposits that lay captured for eons in the folded and faulted metasediments and metavolcanics at the southern end of the Wind River Mountains.
As a result of the bombing and the US being thrust into WWII, there was an immediate need for steel. The US government built a fully integrated steel plant at Provo, Utah where all the needed raw materials were located within the state or nearby. The steel plant was operated as a government facility until June 1946 when it was sold to US Steel Corporation.
By the early 1950’s the quality and quantity of the iron ore deposits in Utah were diminishing and there was a need to discover and develop a new iron ore source to supply the plant. In June 1953, US Steel hired Dr. Paul Procter (head of the geology department, Missouri School of Mines) and Chuck Dahl, who was his field assistant, to search for a deposit of taconite iron formation in southern Wyoming.
By August of that year, the pair had worked westward to the south end of the Wind River Mountains. Longtime Jackson resident, Chuck Dahl, will tell the story of the discovery that he was intimately involved with, and the subsequent development and demise of the Atlantic City iron ore mine at South Pass, Wyoming.
From Wikipedia: The Goldman Meadows Formation overlies the Diamond Springs Formation and contains two distinct lithologies: a schist member that includes pelitic schists, quartzites and massive to schistose amphibolites; and iron formation members composed of banded quartz-magnetite-amphibolite iron formation. The iron formation consists of laminated dark gray to black, fine-grained, hard, dense alternating 0.1-to-2-inch-thick (2.5 to 50.8 mm) layers of magnetite and metachert and varying amounts of amphibole. The average iron content in the Atlantic City area is about 33.5% and ranges as high as 56.23%.
Don’t miss this fascinating presentation: “The Discovery, Development, & Demise of Wyoming’s Atlantic City Iron Mine,” presented by Chuck Dahl on Tuesday, January 16, at 6pm, at the Teton County Library.