T59 Unconventional Ideas and Outrageous Hypotheses II: In Honor of Warren B. Hamilton

Sunday, 22 September 2019
1:30 PM - 5:30 PM
Room 127ABC, North Building


DO ALL OCEANIC PLATEAUS ERUPT AT SPREADING RIDGES?

Paper number: T59-6
Program: Technical Sessions
Time: 2:50 PM – 3:05 PM


Authors


Abstract

Oceanic plateaus are low-slope basaltic mountains that rise several kilometers above the abyssal plains and have broad areas >~105 km2. A widely-accepted hypothesis is that these large igneous provinces (LIPs) are the oceanic equivalent of continental flood basalts, erupted from the massive head of a nascent mantle plume. The result is thought to be an enormous volcano constructed of a vertical stack of long-runout lava flows. Accumulating evidence indicates that many oceanic plateaus record linear magnetic anomalies, a hallmark of seafloor spreading. Long-runout lava flows would destroy this magnetic character, so these plateaus must be formed via lava flows and intrusions constrained near the spreading ridge axis in a process akin to seafloor spreading, but forming thick crust. A notable example of a plateau with linear magnetic anomalies is Shatsky Rise, which formed during the Late Jurassic and Early Cretaceous at a triple junction with at least two ridges. Virtually the entirety of the plateau, including the large edifices Tamu and Ori massifs, is characterized by linear magnetic anomalies. Despite the fact that common practice is not to interpret magnetic anomalies over oceanic plateaus (lest the anomalies be contaminated by topography), a number of other oceanic plateaus clearly record linear magnetic anomalies plausibly recorded by seafloor spreading. This list includes Rio Grande Rise, Valdivia Bank (a part of Walvis Ridge), and the Azores plateau in the Atlantic Ocean and Joey and Roo Rises in the Indian Ocean. Many others, including the enormous Ontong Java Nui complex (Ontong Java, Manihiki, Hikurangi plateaus), likely formed at spreading ridges. Here I examine the list of oceanic plateau LIPs compiled by Coffin and Eldholm (Reviews of Geophysics, v. 32, 1994, p. 1-36) to see if any were clearly not formed at a spreading ridge. For many, this connection cannot be pinned down, but there is yet no convincing example of one formed off-ridge. The implication is that oceanic plateaus are a product of seafloor spreading.

Geological Society of America Abstracts with Programs. Vol. 51, No. 5

doi: 10.1130/abs/2019AM-335361

© Copyright 2019 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.