My dissertation research consists of two themes: (a) the analysis of Middle
Jurassic - Early Cretaceous marine magnetic anomalies (M-anomalies) in order to
construct a comprehensive geomagnetic polarity timescale and (b) the investigation of
the upper oceanic crustal architecture using downhole geophysical logs. These themes
were chosen to better understand how remotely-sensed geophysical signals elucidate the
formation and evolution of oceanic crust. This revised Pacific-wide MGPTS model
shows significant improvement in its reliability, exhibits global applicability, and
highlights changes in the paleo-Pacific spreading regime. By integrating Atlantic Manomaly
analyses with the new MGPTS model and reviewing previous seismic studies,
we shed new light on the causes of a ubiquitously distributed ?Atlantic anomaly smooth
zone? where little coherency among M5-M15 anomaly sequence is observed. For the
second theme, I analyzed the architecture of 15 m.y. old superfast spreading East Pacific
Rise crust drilled at Ocean Drilling Program Hole 1256D in the eastern Pacific. An intact
upper oceanic crustal section was penetrated at this site to a depth of 1507 mbsf. In situ
crustal architecture was mapped from resistivity imagery (electrofacies by Formation MicroScanner) combined with recovered cores and other logs. Highlights of this
research are: (1) most of the extrusive section consists of massive flows and fragmented
formations including breccias, which has important implications for the magnetic source
layer and pathways of hydrothermal alteration; (2) the dike complex is composed of
sheeted-dikes dipping away from the paleo-spreading axis consistent with submersible
observations at other sites in the eastern Pacific; (3) the crustal construction processess
from ridge axis to abyssal plain during 0-50 kyr time are consistent with previous
seismic reflection studies based on the integration of our stratigraphy model with lava
flow observations from the southern East Pacific Rise.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2009-05-279 |
| Date | 2009 May 1900 |
| Creators | Tominaga, Masako |
| Contributors | Sager, William W. |
| Source Sets | Texas A and M University |
| Language | English |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | application/pdf |
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