167 D55. Great Maps and Other Topics in the History of Geology (Posters)

Monday, 23 October 2017
9:00 AM - 6:30 PM
Halls 4EF

DIABASE WEATHERING AND THE INTERPRETATION OF AMERICAN CIVIL WAR COMBAT PHOTOGRAPHY

Paper number: 167-6
Program: Technical Sessions
Time: 9:00 AM – 6:30 PM

Authors

Abstract

Civil War photographers visited the battlefield south of Gettysburg, Pennsylvania, in the days immediately after fighting had ceased and captured some of the most important images of combat fatalities ever produced. These iconic images were shocking to citizens on the home front, and at the same time, they proved immensely popular. To historians, the photographs document the nature of the landscape as well as the dress and physical condition of the soldiers. Unfortunately, the photographers often provided erroneous, vague, or even fraudulent captions and descriptions for their images, much to the confusion of postbellum historians.

A century after these photographs were published, local historian William Frassanito used the geomorphology of the battleground, and specifically the unusual mechanical and chemical weathering patterns, systematic joints, and exfoliation forms of the outcropping diabase to identify the location of many of these photographs. One of his most important contributions concerned Alexander Garner's series of images that included a group of fallen soldiers he captioned "A Harvest of Death". Frassanito's careful analysis of the details of the soldiers' clothing and the relative positioning of their corpses allowed him to demonstrate that the photographs, which were described as having come from various locales around the battlefield, were instead the same group of bodies photographed from different angles. Nevertheless, the true locality of these soldiers proved more elusive – until he studied the diabase boulders. While nearly every feature of the battlefield, including forest cover and land use, had changed in the 100 years after the battle, the slow weathering rate of the durable igneous rocks allowed the historian to utilize them as a geographic tracer across time and to determine the exact position on the battlefield where the men had been killed, and days later photographed. This combination of forensic analysis and geological study also allowed Frassanito to prove that the image many scholars consider the most famous photograph to emerge from the Civil War – Gardner’s “Rocks could not save him at the Battle of Gettysburg” – was, in reality, staged and the dramatically-positioned cadaver had been transported by the photographer and his assistants across Devil’s Den to a more photogenic location.

Geological Society of America Abstracts with Programs. Vol. 49, No. 6

doi: 10.1130/abs/2017AM-300878

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