DEPOSITIONAL ENVIRONMENT AND PROVENANCE OF A BOULDER-RICH DIAMICTITE, WITMARSUM, PARANÁ STATE, BRAZIL
The goal of this study is to determine the depositional environment and provenance of this diamictite unit. Images of the outcrop were analyzed to determine the apparent orientation of the boulders with a 3:2 length/width ratio in order to determine mode of transport. Sediment analyses of inter-clast diamictite samples from the outcrop were conducted to determine sand grain lithology and provenance, grain size, roundness, and sphericity.
Results of this research were compared to the results of the analysis of a nearby, presumably correlative, unit (4 m away). Analysis of boulders (greater than 0.2 m in diameter) in this outcrop showed the same orientation as that of the nearby exposure. However, differences were observed. Although the clasts of all sizes in the outcrop studied show no apparent preferred orientation, clasts of all sizes in the nearby exposure do exhibit a preferred orientation that indicates flow. Additionally, sediment analyses show differences in both grain size distribution and provenance between the two exposures. Thus, correlation of the boulder-rich unit between the two exposures is tentative. However, if this unit is the result of a subaqueous debris flow, variations in sedimentary characteristics over a small distance would be expected.
Research for this study was funded by a grant from the N.S.F.-R.E.U Program (NSF-EAR-1262945).