Variations in structure and tectonics along the Mid-Atlantic Ridge, 23⁰N and 26⁰N
type: CreativeWork
description: The variation in the depth and width of the median valley along the Mid-Atlantic Ridge (MAR) suggests that the formation of ocean crust at slow spreading centers is not a simple two-dimensional process in which crustal accretion occurs uniformly both along the ridge axis and with time. Rather, it has been proposed that the ridge axis can be divided into a number of distinct segments or spreading cells. This thesis investigates the segmentation model by studying the variability in the structure and tectonics within spreading cells at 23°N and 26°N along the MAR. The results support the segmentation model in which accretion varies along the ridge, evolving as independent spreading cells or segments, with different portions of the ridge system being in different stages of volcanic and tectonic evolution. Chapter 2 presents an overview of morphologic and tectonic variations along a 100- km-length of the MAR south of the Kane Fracture Zone (MARK area). Sea MARC.I side scan sonar data and multi-beam Sea Beam bathymetry are used to document the distribution of crustal magmatism and extensional tectonism near 23°N. The data indicate a complex median valley composed by two distinct en echelon spreading cells which overlap in a discordant zone that lacks a well-developed rift valley or neovolcanic zone. The northern cell, immediately south of the fracture zone, is dominated by a large constructional volcanic ridge and is associated with active high-temperature hydrothermal activity. In contrast, the southern cell is characterized by a NNE-trending band of small fissured and faulted volcanos that are built upon relatively old, fissured and sediment-covered lavas; this cell is inferred to be in a predominantly extensional phase with only small, isolated volcanic eruptions. Despite the complexity of the MARK area, volcanic and tectonic activity appears to be confined to the 10-17 km wide inner rift valley. Small-offset normal faulting along near-vertical planes begins within a f…
abstract: The variation in the depth and width of the median valley along the Mid-Atlantic Ridge (MAR) suggests that the formation of ocean crust at slow spreading centers is not a simple two-dimensional process in which crustal accretion occurs uniformly both along the ridge axis and with time. Rather, it has been proposed that the ridge axis can be divided into a number of distinct segments or spreading cells. This thesis investigates the segmentation model by studying the variability in the structure and tectonics within spreading cells at 23°N and 26°N along the MAR. The results support the segmentation model in which accretion varies along the ridge, evolving as independent spreading cells or segments, with different portions of the ridge system being in different stages of volcanic and tectonic evolution. Chapter 2 presents an overview of morphologic and tectonic variations along a 100- km-length of the MAR south of the Kane Fracture Zone (MARK area). Sea MARC.I side scan sonar data and multi-beam Sea Beam bathymetry are used to document the distribution of crustal magmatism and extensional tectonism near 23°N. The data indicate a complex median valley composed by two distinct en echelon spreading cells which overlap in a discordant zone that lacks a well-developed rift valley or neovolcanic zone. The northern cell, immediately south of the fracture zone, is dominated by a large constructional volcanic ridge and is associated with active high-temperature hydrothermal activity. In contrast, the southern cell is characterized by a NNE-trending band of small fissured and faulted volcanos that are built upon relatively old, fissured and sediment-covered lavas; this cell is inferred to be in a predominantly extensional phase with only small, isolated volcanic eruptions. Despite the complexity of the MARK area, volcanic and tectonic activity appears to be confined to the 10-17 km wide inner rift valley. Small-offset normal faulting along near-vertical planes begins within a f…
author: Kong, Laura S. L.
language: en_US
keywords: Sea-floor spreading, Conrad (Ship) Cruise RC25-11, Hudson (Ship) Cruise 85-010
date published: 1990-06
date modified: 2026-07-27T22:05:19Z
provider: Woods Hole Oceanographic Institute
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Massachusetts Institute of Technology and Woods Hole Oceanographic Institution

PropertyValue
property ID: Handle
value: https://hdl.handle.net/1912/5421

PropertyValue
property ID: DOI
value: 10.1575/1912/5421