GSA Annual Meeting in Denver, Colorado, USA - 2016

Paper No. 237-19
Presentation Time: 9:00 AM-6:30 PM


HARTKE, Samantha1, PUGH, Andrew2, CAMACHO, Daniel3, ANTINAO, José Luis4 and MARTINEZ GUTIERREZ, Genaro3, (1)Department of Geosciences, University of Texas at Dallas, 800 W. Campbell Road, MC17, Richardson, TX 75080, (2)Mackay School of Earth Sciences and Engineering, University of Nevada, Reno, 1664 N. Virginia Street, Reno, NV 89557, (3)Earth Sciences, Universidad Autonoma de Baja California Sur, Carretera al sur km 5.5, La Paz, 23080, Mexico, (4)Division of Earth and Ecosystems Sciences, Desert Research Institute, 2215 Raggio Parkway, Reno, NV 89512,

On the eastern coast of the Baja California Peninsula, marine terraces are incised by numerous arroyos, along which fluvial terraces have developed. Through the NSF-funded Baja Basins REU, fluvial terraces in Arroyo Santa Agueda and Arroyo Boleo of the Santa Rosalia region were mapped and analyzed to better understand regional tectonic geomorphology related to the Pleistocene evolution of the Santa Rosalia Basin. A soil chronosequence in these fluvial terraces will be used to understand this evolution. South of this basin, in Mulege and Bahia Coyote, previous work focused on marine terrace development, but not inland fluvial terraces.

During the initial phase of study, fluvial terraces were mapped using GIS in the field while soil horizons of terraces lining each arroyo were observed, described, and sampled. Soil horizon compositions will be determined by grain size analysis, XRD, and thin section microscopy. Soil development indexes will be assigned to soil profiles characterized in the field following the method outlined by Harden(1982) on the basis of various soil properties. GIS analysis of relative soil development on terraces of varying elevations and locations will allow interpretation of regional tectonics during terrace formation.

We expect to see varying levels of fluvial terrace soil development in Arroyos Santa Agueda and Boleo despite corresponding elevations. Relative rates of terrace uplift compared with terrace development will allow interpretation of differences in tectonic activity in the two catchments which limit the Santa Rosalia basin to the south and north, respectively. The constraints provided by this analysis will generate new insights into development of the Santa Rosalia basin. When combined with absolute geochronology, this will be the first fluvial terrace chronosequence developed for central Baja California, a powerful tool for regional paleoclimate and geochronology studies in the future.

Reference: Harden, J., 1982, Geoderma, vol. 28, pg. 1-28.