Skip to Main Content
Book Chapter

Gravity Anomalies and Crustal Structure of the Gulf and Peninsular Province of the Californias

By
Richard W. Couch
Richard W. Couch
CONMAR College of Oceanography Oregon State University Corvallis, Oregon, U.S.A.
Search for other works by this author on:
Gordon E. Ness
Gordon E. Ness
CONMAR College of Oceanography Oregon State University Corvallis, Oregon, U.S.A.
Search for other works by this author on:
Osvaldo Sanchez-Zamora
Osvaldo Sanchez-Zamora
CONMAR College of Oceanography Oregon State University Corvallis, Oregon, U.S.A.
Search for other works by this author on:
Gustavo Calderón-Riveroll
Gustavo Calderón-Riveroll
CONMAR College of Oceanography Oregon State University Corvallis, Oregon, U.S.A.
Search for other works by this author on:
Pierre Doguin
Pierre Doguin
CONMAR College of Oceanography Oregon State University Corvallis, Oregon, U.S.A.
Search for other works by this author on:
Thomas Plawman
Thomas Plawman
CONMAR College of Oceanography Oregon State University Corvallis, Oregon, U.S.A.
Search for other works by this author on:
Shane Coperude
Shane Coperude
CONMAR College of Oceanography Oregon State University Corvallis, Oregon, U.S.A.
Search for other works by this author on:
Bruce Huehn
Bruce Huehn
CONMAR College of Oceanography Oregon State University Corvallis, Oregon, U.S.A.
Search for other works by this author on:
William Gumma
William Gumma
CONMAR College of Oceanography Oregon State University Corvallis, Oregon, U.S.A.
Search for other works by this author on:
Published:
January 01, 1991

Abstract

We have prepared gravity anomaly maps of the onshore-offshore region of northwest Mexico and southern Alta California. Plates 3 and 4 of this volume show free-air gravity anomalies at sea and simple Bouguer anomalies on land, contoured at a 10 mGal interval. We present eight modeled geophysical sections which cross the peninsula of Baja California, the Gulf of California, the Salton Trough, the Laguna Salada, and mainland Mexico. Three additional geophysical sections cross the Rivera Fracture Zone. The northern sections show a crust about 12 km thick beneath the outer Continental Borderland. The crustal thickness increases to about 17 km beneath the inner Borderland and reaches about 28 km maximum thickness beneath the northern Peninsular Ranges. The maximum crustal thickness beneath the central and southern Peninsular Ranges is about 22 km. The crust beneath the Salton Trough and the Laguna Salada thins to about 21 km minimum. Beneath the northern Gulf of California the crust thins to 13 km minimum and under the central Gulf it is about 10 km thick. In both the northern and central Gulf the thinnest crust is found near the peninsular coast. Beneath the southern Gulf, the crust is about 8 km thick and is no longer asymmetrical. A low density upper mantle (3.10 to 3.15 gm/cm3) is found beneath the entire Gulf. Its volume increases to the south.

Based on onshore geology, section densities, and the mapped anomalies, we trace Franciscan-like rocks continuously beneath the western margin of the peninsula and borderland. Similarly, Mesozoic metamorphic and batholithic rocks that make up the northern Peninsular Ranges continue under the Tertiary volcanics of the central and southern Peninsular Ranges. High density units (2.82 to 2.90 gm/cm3) are emplaced in the upper crust beneath parts of the borderland and Bahia Sabastiân Vizcaino.

Mapped anomalies show continuations of transform faults beneath the sediment cover on the flanks of the Gulf, and reveal linear basement highs and lows under the west side of the peninsula. Mapped anomalies also emphasize the continuity of basement highs and lows in the borderland.

The ridges and troughs of the Rivera Fracture Zone are reflected in the crustal structure at depth. The crust thins underneath the ridges and thickens beneath the troughs, probably caused by alteration of the crust and upper mantle by faulting and hydrothermal activity.

You do not currently have access to this article.
Don't already have an account? Register

Figures & Tables

Contents

AAPG Memoir

The Gulf and Peninsular Province of the Californias

J. Paul Dauphin
J. Paul Dauphin
Search for other works by this author on:
Bernd R. T. Simoneit
Bernd R. T. Simoneit
Search for other works by this author on:
American Association of Petroleum Geologists
Volume
47
ISBN electronic:
9781629811130
Publication date:
January 01, 1991

GeoRef

References

Related

A comprehensive resource of eBooks for researchers in the Earth Sciences

Close Modal
This Feature Is Available To Subscribers Only

Sign In or Create an Account

Close Modal
Close Modal