Timing of Deposition of Foreland Basin Sediments, Central Andes, Bolivia
Nick Perez
The goal of this study was to determine the timing of deposition of foreland basin sediments from the Chaco Basin in Bolivia using magnetostratigraphy. I went to the field for two weeks near Villamontes, Bolivia in August of 2008 with my supervisor Dr. Brian Horton to collect samples for paleomagnetic analysis. This study is important because a detailed sedimentation history of a foreland basin in this part of the Andes has never been completed. With the most detailed chronostratigraphy of the Chaco basin yet, we hope to add to our understanding of the role of tectonics and climate in orogenic belts.
Previous workers have noted that there must be an increase in sedimentation rate, however this is the first study from this area to document the precise timing and magnitude of this increase in sediment accumulation. The results from our study show a strong pulse of sedimentation into the basin at ~7.5 Ma. This has been correlated temporally with the potential rapid uplift of the Central Andes and the possible onset of the South American monsoon, either of which may be the cause for the increase in rate. While this work does not determine what caused the increase in sedimentation rate, it does provide the foundation for future studies in the area. Our study, as well as future ones, will help improve our understanding of the complex interactions between climate, tectonics and sedimentation.