Date of Award

1970

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Geology

First Advisor

F.R. Karner

Abstract

Authigenic analcite constitutes up to about 60 percent of a massive, arksosic sandstone exposed on major buttes in the North Dakota Badlands. The analcite constitutes up to about 80 percent of a thin analcimolite bed at the top of the arkose unit. The analcite occurs as spherulites in the interstices of the arkose and as a cement in the analcimolite. Three types of spherulites are recognized: (1) spherulites with an internal radial structure; (2) spherulites with a massive center and a peripheral radial structure; and (3) spherulites lacking an internal radial structure or having a poorly-defined internal structure. The spherulites occur individually and as coalesced masses. Analcite in the arkose and analcimolite is silica-poor.

Detrital minerals associated with the analcite include quartz, Naplagioclase, K-feldspar, and illite. Sericite is associated with analcite in the arkose and may also be authigenic. The analcite is least abundant at the base of the arkose unit and increases upward. The abundances of analcite and the detrital feldspars are inversely related.

Analcite composition, distribution with respect to the feldsparas, presence of sericite, and the absence of a vitroclastic texture, suggests that analcite in the arkose was derived from a post-depositional dissolution of the feldspars. It is proposed that the analcite in the arkose and analcimolite were derived from different, but similar, parent materials.

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