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Extremely acid Permian lakes and ground waters in North America

Nature

By:
, , , ,
DOI: 10.1038/31917

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Abstract

Evaporites hosted by red beds (red shales and sandstones), some 275-265 million years old, extend over a large area of the North American mid- continent. They were deposited in non-marine saline lakes, pans and mud- flats, settings that are typically assumed to have been alkaline. Here we use laser Raman microprobe analyses of fluid inclusions trapped in halites from these Permian deposits to argue for the existence of highly acidic (pH < 1) lakes and ground waters. These extremely acidic systems may have extended over an area of 200,000 km2. Modern analogues of such systems may be natural acid lake and groundwater systems (pH ~2-4) in southern Australia. Both the ancient and modern acid systems are characterized by closed drainage, arid climate, low acid-neutralizing capacity, and the oxidation of minerals such as pyrite to generate acidity. The discovery of widespread ancient acid lake and groundwater systems demands a re-evaluation of reconstructions of surface conditions of the past, and further investigations of the geochemistry and ecology of acid systems in general.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Extremely acid Permian lakes and ground waters in North America
Series title:
Nature
DOI:
10.1038/31917
Volume
392
Issue:
6679
Year Published:
1998
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Nature
First page:
911
Last page:
914
Number of Pages:
4