2005 Salt Lake City Annual Meeting (October 16–19, 2005)

Paper No. 4
Presentation Time: 4:15 PM


BIELER, David B., Department of Geology, Centenary College of Louisiana, Shreveport, LA 71134, dbieler@centenary.edu

Although Powell's biographers have suggested his 1871-72 crew was composed of untested amateurs, original documents by John Steward indicate that Powell's assistant geologist for the 1871 river trip was more than merely competent. Powell credits Steward with several measured sections in the Uintah Mountains report, but Steward's own notes are filled with careful observations and subtle reflections. Three primary documents reveal the source of detailed geologic information that formed the foundation of the Uintah report.

In addition to the Red Canyon and Cataract Canyon sections published in the Unitah Mountain report, Stewards notes contain additional measured sections. An initial measured section in the Green River formation allowed Steward to try to trace key beds through the first part of the river trip. He included a measured section of the flat lying Tertiary/Quaternary rocks in Brown's Park and reflected on possible periglacial and lacustrine origins of the strata. He also recorded measurments of Carboniferous strata in the Split Mountain area. These measured sections are particularly noteworthy for their careful attention to fossil content, with Steward sometimes providing Latin nomenclature.

Steward also struggled with structural analysis of the deformed rocks traversed in the trip. His notes from Cataract Canyon show his insights and flexibility. Steward tried to understand this structure in terms of movements related to volume changes as limestones were replaced by gypsum. He showed an understanding of the weathering products of pyrite to include sulfate in solution, estimated volume changes of replacing calcite with gypsum, and employed the resulting forces as a mechanism to fracture and fold the rocks. (Although he was aware of the presence of halite in the section, it is unlikely that Steward would have known of the effects of salt flow that produced the Paradox folds.)

Steward complained that he and others on the 1871-72 trip had been neglected in the official reports. His primary notes show the extent to which he was justified.