Date of Award
Master of Arts (MA)
The Cretaceous Hell Creek and Paleocene Ludlow Formations of southwestern North Dakota are nonmarine sediments of alluvial origin. The heavy minerals of these formations were specifically studied to determine the source rock types and their provenance, and generally assess the diagenetic processes which affected the heavy minerals.
The heavy minerals include zircon, rutile, tourmaline, garnet, ilmenite, spinel, apatite, epidote, sphene, pyroxene, dolomite, biotite, andalusite, pyrite, monazite, and barite. Most of the heavy minerals have angular shapes, indicating one cycle of erosion and deposition.
The heavy mineral percentages of the concretions and surrounding sediments were compared within and between the Hell Creek and Ludlow Formations using linear discriminant analysis. The comparisons between the heavy mineral percentages of the concretions and surrounding sediments within the Hell Creek and Ludlow Formations showed no significant differences. The comparison of the concretions of the Hell Creek and Ludlow Formations showed no significant difference in the heavy mineral percentages. The heavy minerals in the surrounding sediments of the Hell Creek and Ludlow Formations are significantly different at the .99 confidence level.
The T test was used to compare the mean heavy mineral values of the concretions and surrounding sediments between the Hell Creek and Ludlow Formations. The results of the T-test support the results of the linear discriminant analysis. The comparison of the heavy mineral means of the surrounding sediments, between the Hell Creek and Ludlow Formations shows that tourmaline, rutile, epidote, garnet and zircon are significantly different. In the comparison of the mean heavy mineral values of the concretions between the formations only garnet was significantly different. The difference between the heavy mineral percentages of the concretions and surrounding sediments within each formation has been attributed to the re placement of minerals by calcite within the concretions. The difference between the heavy mineral percentages of the Hell Creek and Ludlow surrounding sediments is probably due to subtle changes in source rock types from the Hell Creek to Ludlow time.
The source rock types associated with the heavy minerals in these two formations are volcanic and intrusive igneous, thermal metamorphic, and reworked sedimentary rocks. The provenance of these sediments is thought to be the Elkhorn Mountains Volcanic Complex and adjacent rocks of western Montana, because of the similar mineralogies and timing (82 myrs to 71 myrs) and volume of volcanic activity in the complex. The comparison of the heavy mineral percentages indicates no major change in provenance from Hell Creek to Ludlow time.
Farris, Robert A., "Heavy minerals of the Cretaceous Hell Creek and Paleocene Ludlow Formations of Slope and Bowman counties, North Dakota" (1984). Theses and Dissertations. 88.