Exploring Late Devonian Mass Extinctions And Ocean Anoxia Events In Understudied Paleoenvironments Of Asia

ASU Author/Contributor (non-ASU co-authors, if there are any, appear on document)
Olivia C. Paschall (Creator)
Appalachian State University (ASU )
Web Site: https://library.appstate.edu/
Sarah Carmichael

Abstract: The Devonian-Carboniferous (D-C) transition (359 Ma) was a period of rapid global faunal changes in conjunction with global cooling and widespread ocean anoxia. The end-Devonian mass extinction is one of the top 10 mass extinctions in Earth’s history, and the associated anoxia and regression is referred to as the Hangenberg Crisis. In many locations, the Hangenberg Crisis is characterized in the rock record by sandstone and black shale deposits. Little is known about the Hangenberg Crisis in Southeast Asia, however. Here we show that the Hangenberg Crisis is recorded within the Pho Han Formation on Cat Ba Island in northeastern Vietnam, and at the Hoshoot Shiveetiin Gol locality in the Hovd Province of southwest Mongolia. Preliminary work in July-August 2018 at the Hoshoot Shiveetiin Gol locality in Mongolia reveals that the Late Devonian shallow marine sequence is relatively continuous and encompasses the entire Late Devonian timescale, including both the Frasnian- Famennian and Devonian-Carboniferous transitions. Although no black shale is present at the locality due to the location’s paleotopography, we interpret a pronounced arkosic sandstone layer to represent the Hangenberg regression event. In contrast, the Cat Ba Island section in Vietnam represents a sediment-starved basinal facies on the South China carbonate platform, where long-term dysoxic/anoxic conditions (as determined by trace element proxies, increased total organic carbon, and framboidal pyrite distributions) persisted. More severe anoxia (approaching euxinia) exists within the Hangenberg Crisis stratigraphic interval. Mercury (Hg) chemostratigraphy reveals a significant enrichment that corresponds to the Hangenberg Crisis and the D-C transition. The Hg is most likely sourced from volcanic emissions, potentially linking the end-Devonian anoxia and mass extinction to large-scale volcanic activity. This is a new and valuable development that is supported by very recent studies in Uzbekistan and Germany and must be investigated further. As both sites represent the two end members of understudied paleoenvironments (compared to sites in Europe and North America, where overlapping signals can be difficult to interpret), they are critical to understanding Late Devonian anoxia and extinction events.

Additional Information

Honors Project
Paschall, O. (2018). Exploring Late Devonian Mass Extinctions And Ocean Anoxia Events In Understudied Paleoenvironments Of Asia. Unpublished Honors Thesis. Appalachian State University, Boone, NC.
Language: English
Date: 2018
Devonian-Carboniferous, Hangenberg Crisis, Hoshoot Shiveetiin Gol, volcanic emissions, Frasnian-Famennian and Devonian-Carboniferous transitions, anoxia

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