Document Type
Thesis
Abstract
The Civil War submarine H. L. Hunley, the world’s first successful military submarine which sank in Charleston harbor in 1864, contains biologically mediated iron concretions called rusticles. These rusticle have similar internal morphology to rusticles from other shipwrecks including a central water conduit, sacs, ducts, side channels, accreted sediment, and fibrillar bundles. Petrographic work shows that these rusticle are stratified, having an inner dense region with little accreted sediment, a porous middle region with some sediment accreted, and an outer region composed dominantly of sediment. Energy Dispersive Spectroscopy revealed that the amount of sediment could also be tracked through elemental chemistry. The elemental chemistry of these rusticles was then compared to rusticles from other shipwrecks and found to contain more elements such as silicon, aluminum, calcium, and oxygen that are linked to the presence of sediment in the rusticles. These elements increase from the interior to exterior while the amount of iron and magnesium decrease. The elemental chemistry of the samples was then compared between rusticles and was found to show trends in elements linked to the sediment. The three regions observed were hard to characterize as to their mineralogy through thin sections. Through Infrared spectroscopy, X-ray powder diffraction, and Méssbauer spectroscopy different minerals were found in the different regions of the rusticles. Hematite and or feroxhydrite were found in the rusticles interior, while the middle region contained a magnetic fraction that is most likely magnetite, and the outer region was dominantly composed of ylepidocrocite. On an Eh/pH diagram these minerals form between -4 and 4 E [V] and in a pH range of 7 to 12. The presence of hematite in the innermost region may indicate an oxidizing environment during the initial formation of the rusticles formation, a trend towards a reducing environment is revealed by the presence of magnetite in the middle region. A change in the environment is supported by the elemental chemistry with less bonded oxygen in this region. Rusticle # 6514 indicates through its morphology which was found to be denser, its large proportion of bonded oxygen, and the presence of hematite in this region that it experienced an earlier or faster period of growth in the initial presence of an oxidizing environment dissimilar to those found in the other rusticles. Rusticle #6514 may have been close to the initial hull breach. Future work on these rusticles may better define the trends in electrochemistry in the Hunley after it sank.
Date Awarded
2007
Department
Geology
Advisor 1
M. Scott Harris
Advisor 2
Heather MacDonald
Recommended Citation
Lunze, Jason L., "The Distribution, Morphology, and Chronology of Rusticle Growth on the Confederate Submarine H. L. Hunley" (2007). Geology Senior Theses. William & Mary. Paper 179.
https://scholarworks.wm.edu/geologyseniors/179
