Studies involving water temperature, water composition, hydrogen ion concentration, oxidation-reduction potentials, oxygen content, fauna and flora were made of Lakes Nicaragua and Managua that lie within a graben in the volcanic region of western Nicaragua. Bottom sediments in these lakes consist of organic diatomaceous volcanic silts and clays in which quartz, plagioclase, montmorillonite and volcanic glass are principal constituents. Conclusions based on these studies are that no definite evidence of a former marine connection is furnished by the sediments and that the lakes may have been fresh-water for all or nearly all of their history. Despite the presence of sharks and certain marine or brackish-water types of invertebrates, a fresh-water history of the lakes seems more probable than origin as a marine embayment.

First Page Preview

First page PDF preview
You do not currently have access to this article.