Date of Award
Doctor of Philosophy (PhD)
Jeffrey A. Karson
Anisotropy of magnetic susceptibility, Marine magnetics and paleomagnetics, Mid-ocean ridge processes, Oceanic structures, Paleomagnetism applied to geologic processes, Transform faults
Despite vast amounts of data about the ocean floor, very little is known about processes operating at mid-ocean ridge spreading centers and the generation of oceanic lithosphere that covers approximately 2/3 of Earth's surface. In particular, geologist are uncertain about specific details of magmatic and tectonic processes beneath these divergent plate boundaries and how these processes may vary along the spreading axis. Investigations that combine geologic relationships and magnetic properties continue to yield fundamental tools for understanding and constraining seafloor spreading processes. This thesis contains a collection of studies designed to characterize structural geology and magnetic properties of oceanic crust formed in regions with high magma supply. A brief overview is provided in an introduction to three separate chapters that are considered individual contributions. Chapter one presents paleomagnetic and structural data from sheeted dikes that are used in combination with regional geologic relationships to constrain the deformation and tectonic history of oceanic crust exposed at the tip of a propagating rift on the East Pacific Rise. Chapter two describes the magnetic fabrics of sheeted dikes from seafloor exposures that provide evidence for a wide range of magma flow directions beneath fast-spreading ridges with high and relatively continuous magma supply. Chapter three provides paleomagnetic evidence to support structural observations for significant rotations of crustal blocks within a migrating transform fault zone in North Iceland that may exhibit similar kinematics to other oceanic transforms.
Horst, Andrew Jay, "Structure and Accretion at Mid-Ocean Ridges With High Magma Supply: Perspectives From Seafloor Escarpments and Iceland" (2013). Earth & Environmental Sciences - Dissertations. 30.