Geophysical surveys in the Gulf of California provided
the data to construct contour maps of bathymetry, free-air
anomalies and total field magnetic anomalies for the area
north of 27° N. Major faults such as the Ballenas-
Salsipuedes, Tiburón, Guaymas, and the South Cerro Prieto
are clearly observable on these maps.
Spectral analysis, using 2-D Fast Fourier Transform
methods, of the magnetic anomalies north of 29° N,
allowed the identification of at least three distinct
magnetic source horizons. The shallowest depth magnetic
horizon, with an average depth to the top of 3.1 km below
sea level, is interpreted as the top of the magnetic
basement. The intermediate depth magnetic horizon, with
an average depth to the top of 5.3 km below sea level, may
represent either a lithological discontinuity in continental
crust, or a transition zone characterized by the intrusion of
igneous rocks, faulting, and fracturing associated with
rifling processes. Some lineaments observed in the contour
map on this horizon are oriented about 15°
counterclockwise from the expected orientation of faults.
Other lineaments are almost perpendicular to those faults.
The deepest magnetic horizon is not apparent at all
locations.
Computed depths to the bottom of the magnetized
crust average 11.5 km below sea level. The depth to the
bottom of the magnetic crust is interpreted as the depth of
the Curie-point isotherm. Assuming a Curie-point
temperature of 580°C and a thermal conductivity of 2.2
W/m °C, the calculated heat flow averages 114 mW/m².
Using a two-dimensional Maximum Entropy Method
(2DMEM) to obtain the power spectrum of the magnetic
anomalies increased the horizontal spatial resolution of the
depth determinations by a factor of 4. This method when
used to compute the depth to the top of the intermediate
horizon, shows an improvement in the delineation of
structures. However, the other magnetic horizons and the
depth to the bottom of the magnetic crust were not clearly
observable using this technique. / Graduation date: 1988
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/29366 |
| Date | 02 May 1988 |
| Creators | Zamora, Osvaldo Sanchez |
| Contributors | Couch, Richard W. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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