Presentation Type

Poster

Start Date

5-8-2024 11:00 AM

End Date

5-8-2024 1:00 PM

Subjects

Geology, Volcanology, Petrology, Igneous Rocks

Advisor

Martin J. Streck

Student Level

Undergraduate

Abstract

The Mahogany Mountain-Three Fingers Rhyolite Field (MM-TFrf) in southeastern Oregon, associated with mid-Miocene rhyolite activity and Columbia River flood basalts, has been the subject of geological scrutiny. Previous studies proposed separate origins for the tuff of Leslie Gulch (LGT) and Spring Creek, but Benson and Mahood (2006) suggested a single ignimbrite event at 15.8 Ma, prompting a reassessment of MM-TFrf's history. This research focuses on LGT, investigating textural disparities between welded and non-welded tuff formations. Petrographic examinations delve into the transformation stages of pyroclastic tuff deposition, revealing the dynamic influences of volcanological and magmatic processes on welded and non-welded tuff development. Using light microscopy, thin sections are meticulously analyzed, with a focus on pyroclastic grain characteristics such as size, vesicularity, and shape. Vesicularity serves as a crucial indicator of eruption dynamics, aiding in the differentiation of pyroclastic clasts. Preliminary findings suggest partially welded ignimbrites contain a higher abundance of visible glass shards. Further investigations aim to elucidate the volcanic dynamics shaping MM-TFrf's history.

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May 8th, 11:00 AM May 8th, 1:00 PM

Textural Investigation into Rapid Welding Transitions in the Tuff of Leslie Gulch along Succor Creek at the Mahogany Mountain-Three Fingers Rhyolite Field, Southeastern Oregon

The Mahogany Mountain-Three Fingers Rhyolite Field (MM-TFrf) in southeastern Oregon, associated with mid-Miocene rhyolite activity and Columbia River flood basalts, has been the subject of geological scrutiny. Previous studies proposed separate origins for the tuff of Leslie Gulch (LGT) and Spring Creek, but Benson and Mahood (2006) suggested a single ignimbrite event at 15.8 Ma, prompting a reassessment of MM-TFrf's history. This research focuses on LGT, investigating textural disparities between welded and non-welded tuff formations. Petrographic examinations delve into the transformation stages of pyroclastic tuff deposition, revealing the dynamic influences of volcanological and magmatic processes on welded and non-welded tuff development. Using light microscopy, thin sections are meticulously analyzed, with a focus on pyroclastic grain characteristics such as size, vesicularity, and shape. Vesicularity serves as a crucial indicator of eruption dynamics, aiding in the differentiation of pyroclastic clasts. Preliminary findings suggest partially welded ignimbrites contain a higher abundance of visible glass shards. Further investigations aim to elucidate the volcanic dynamics shaping MM-TFrf's history.