Date of Award

Summer 8-1-2023

Degree Type

Masters Thesis

Degree Name

Master of Science (MS)

School

Biological, Environmental, and Earth Sciences

Committee Chair

Dr. Jeremy Deans

Committee Chair School

Biological, Environmental, and Earth Sciences

Committee Member 2

Dr. Alyson Brink

Committee Member 2 School

Biological, Environmental, and Earth Sciences

Committee Member 3

Dr. Franklin Heitmuller

Committee Member 3 School

Biological, Environmental, and Earth Sciences

Abstract

The Dadeville Complex (DC) lies in the Inner Piedmont of eastern Alabama and western Georgia. The DC formed as a volcanic island arc during the Taconic orogeny (Ordovician Period) and was accreted onto Laurentia during the Acadian orogeny (Devonian-Mississippian Periods); however, the mechanism and role of accretion during the Acadian orogeny is not well constrained. Three proposed emplacement mechanisms for the DC include: (1) orogen-perpendicular translation; (2) orogen-parallel translation; (3) orogenic channel flow.

Today, the DC is a major (over 100 kilometers long) allochthonous terrane composed mostly of meta-igneous rocks. This study investigated structural fabrics and kinematic indicators in the Ponders quadrangle in eastern Alabama, which includes the DC and Brevard Zone, one of the largest shear zones in the southern Appalachians, to assess the emplacement models.

Map patterns in the study area indicate two distinct sets of folds in the DC. F1 folds are north or south trending and were created by east-west oriented shortening (D1). F2 folds are east or west trending and were formed by north-south directed shortening (D2). D2 created the shallowly east or west plunging mineral lineations and also refolded F1 to create doubly-plunging hinges. Both deformational events occurred during the Acadian/Neoacadian orogeny at peak amphibolite-facies metamorphism. The DC was accreted onto Laurentia in two stages with distinct shortening directions, potentially due to rotation along the Alabama promontory.

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