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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 49 (1965)

Issue: 3. (March)

First Page: 360

Last Page: 360

Title: Origin of Pisolites: ABSTRACT

Author(s): Carroll M. Thomas

Article Type: Meeting abstract


The Permian pisolites of the Guadalupe Mountains of southern New Mexico and west Texas have been widely accepted as being a by-product of algal activity in the shallow lagoonal area behind the platform margin of the Delaware Basin. If this interpretation were correct, one would expect to find smooth pisolite laminations formed by the algae and not the crenulate laminations seen in some of the pisolites. One would also expect to see developed stratification, and interlayering with stromatolites and other algal deposits. Evidence of pisolites being formed by algae somewhere in the world today would be anticipated.

Evidence shows that such conditions are not applicable to the Guadalupe Mountain pisolites. The field relationships suggest that the pisolites developed in porous and permeable calcarenites by a weathering-soils process. The area behind the platform margin was periodically subaerially exposed. The climate was arid with occasional wet periods. The downward migrating surface waters leached calcium carbonate from the upper layers and concentrated it in the lower layers as films or laminae about nuclei. These dense concentrations are the pisolites; they compare very favorable with caliche deposits in the area.

The environment can be completely misinterpreted if the pisolites are thought to have formed in a shallow sea when they actually formed in the soil of an arid climate.

Knowledge concerning the factors which produced the pisolites in the Guadalupe Mountains should be applicable in studies of pisolites elsewhere.

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Copyright 1997 American Association of Petroleum Geologists