Geology of Saipan, Mariana Islands; Part 2, Petrology and soils

Professional Paper 280- B-D
By: , and 



The rocks that comprise the volcanic formations of Saipan are of two principal types: dacites, which are characteristically glassy, and andesites, which are comparatively crystalline. The dacites consist primarily of silicic glass, oligoclase, and silica minerals (quartz, tridymite, cristobalite, chalcedony, and opal). Minor constituents in these rocks are green hornblende, biotite, magnetite, and hematite. The andesites are composed principally of labradorite, hypersthene, augite, and subcalcrc augite. Minor but also characteristic constituents of the andesites are quartz, tridymite, cristobalite, anorthoclase, and accessory magnetite, ilmenite, rutile, and apatite. Nine varieties of dacite and andesite are recognized on the basis of chemical composition, mineralogy, and texture. These are dacite, dacite vitrophyre, dacite perlite, hornblende-bearing dacite porphyry, augite-hypersthene andesite, quartz-bearing augite-hypersthene andesite, quartz-bearing augite-hypersthene andesite porphyry, augite andesite, and hypersthene andesite.

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Additional publication details

Publication type Report
Publication Subtype USGS Numbered Series
Title Geology of Saipan, Mariana Islands; Part 2, Petrology and soils
Series title Professional Paper
Series number 280
Chapter B-D
DOI 10.3133/pp280BD
Year Published 1957
Language English
Publisher U.S. Government Printing Office
Publisher location Washington, D.C.
Description Report: 122 p.; 3 Plates: 27.31 x 35.94 inches or smaller; Chart
First page 127
Last page 207
Country Saipan
Online Only (Y/N) N
Additional Online Files (Y/N) N