Title

Petrography and Sedimentology of the Nauga Tuffs, Campbellrand Subgroup, Griqualand West, South Africa: Implications for Magma Composition, Volcanism, Depositional Mechanisms and Setting

Degree Year

1996

Document Type

Thesis

Degree Name

Bachelor of Arts

Department

Geology

Abstract

The tuffs of South Africa's Nauga Formation are investigated for their petrographic and sedimentological properties. Pyroclasts form the bulk of the Nauga tuffs and include altered vitric clasts, accretionary lapilli and armored lapilli, as well as lithic fragments. Detrital crystals of quartz and K-feldspar are present as well. The Nauga pyroclasts formed via phreatomagmatic eruption processes from magma that was most likely basaltic to intermediate in composition. Eruption occurred at shallow subaqueous vents, while the Nauga tuffs were deposited in a deep water facies, possibly by direct airfall, decelerating subaerial pyroclastic flows, as well as high- and low- concentration turbidity currents. The Prieska facies is interpreted as a basinal paleoenvironment.

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