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Book Chapter

Morphology and Origin of Salt Domes of Isthmus of Tehuantepec1

By
H. Contreras V.
H. Contreras V.
Mexico City, Mexico
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M. Castillón B.
M. Castillón B.
Mexico City, Mexico
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Published:
January 01, 1968

Abstract

The Isthmian Salt basin occupies the whole northern part of the Isthmus of Tehuantepec. Identified strata range from probable Permian to upper Miocene. Post-Miocene deposits unconformably overlie all other strata, but no study has been made of them. The Miocene section has been studied most closely because it contains petroleum-productive sandstones. The minimum thickness of the entire Miocene section is in the western part of the basin, where it is only up to 400 m thick, and the maximum thickness is near Ogarrio field, where more than 5,000 m may be present in synclines.

Petroleum and sulfur exploration have yielded considerable data on the salt in the basin. However, the drilling depths generally are not sufficient to define the flanks of individual domes and salt masses. The salt is distributed in at least five huge masses, ranging in width from 10 to 25 km, and in length from 12 to 30 km. These masses lie within 50 m of the surface, and individual domes rise from the larger masses of salt. Some single domes—not obviously related to salt masses—also are present in the area. Most of the large salt structures, as well as the individual domes, have a cap rock composed mainly of anhydrite and smaller quantities of gypsum. Some of the domes, however, have no cap rock. The thickness of the cap rock is greatly varied, and sulfur is present in the cap rock of some domes.

A palynological study of three salt cores showed that the upper part of the salt is of latest Jurassic or earliest Cretaceous age. The lower age limit is not known, but may be as old as Triassic. The thickness of the salt in the massifs may be more than 5,000 m, but the original depositional thickness is unknown. The salt was put into motion as a result of the isostatic effect of the overlying Upper Cretaceous, Paleocene, and Eocene sediments. However, the thick Oligocene sediments probably constituted the main load which induced upward movement of the salt, especially in the eastern part of the basin where Jurassic folding had little effect.

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Contents

AAPG Memoir

Diapirism and Diapirs: a symposium

Jules Braunstein
Jules Braunstein
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Gerald D. O’Brien
Gerald D. O’Brien
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American Association of Petroleum Geologists
Volume
8
ISBN electronic:
9781629812304
Publication date:
January 01, 1968

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