GSA Annual Meeting in Phoenix, Arizona, USA - 2019

Paper No. 124-3
Presentation Time: 9:00 AM-6:30 PM


CAMPBELL, Mae Kate1, BIERMAN, Paul2, SCHMIDT, Amanda H.3, SIBELLO HERNÁNDEZ, Rita Y.4, GARCÍA MOYA, Alejandro4, CARTAS AGUILA, Hector A.4, BOLAÑOS ALVAREZ, Yoelvis4, GUILLÉN ARRUEBARRENA, Aniel4, DETHIER, David P.5, DIX, Monica3, MASSEY-BIERMAN, Marika Eden6, CORBETT, Lee B.1, CAFFEE, Marc W.7 and ALONSO-HERNÁNDEZ, Carlos4, (1)Department of Geology, The University of Vermont, 180 Colchester Ave., Burlington, VT 05405, (2)Geology Department and Rubenstein School of the Environment and Natural Resources, University of Vermont, Burlington, VT 05405, (3)Geology, Oberlin College, 52 West Lorain Street, Oberlin, OH 44074-1044, (4)Centro de Estudios Ambientales de Cienfuegos, Apartado Postal 5, Cienfuegos, 59350, Cuba, (5)Department of Geosciences, Williams College, Williamstown, MA 01267, (6)Williams College, Center for Environmental Studies/Geosciences, 59 Lab Campus Drive, Thompson Bio, Williamstown, MA 01267, (7)Department of Physics and Astronomy, Purdue University, West Lafayette, IN 47907; Department of Earth, Atmospheric and Planetary Sciences, Purdue University, West Lafayette, IN 47907

The Cuban landscape has been heavily influenced by agriculture for centuries; yet, there are few erosion rate estimates at the drainage basin scale. To understand how erosion has changed over time, we compare background erosion rates from 10Be to recent measurements of sediment yield and dissolved load flux. Such data are critical for understanding how human actions affect mass flux off the landscape, and for guiding future development.

Erosion rates, modeled from in-situ 10Be measured in quartz river sand from 8 basins in central Cuba, range from 1.5 to 70 m/My (mean = 30 m/My). For the same basins, chemical denudation rates calculated using basin-specific precipitation runoff estimates and total dissolved solids measured in stream water range from 28-108 m/My (mean = 59 m/My). Countrywide, data from 32 sediment/flow gauging stations maintained during the peak of Soviet-assisted industrial agriculture suggest suspended sediment yields equivalent to 4.4-128 m/My (mean = 48 m/My). In central Cuba, chemical denudation rates and 10Be background erosion rates are inversely related to slope, possibly because harder igneous/metamorphic rocks compose the highlands while weaker carbonate rocks compose the flatlands. These datasets suggest that more mass is lost by solution than by physical erosion, and that human activity has increased erosion rates compared to background levels. Background erosion rates in Cuba are similar to other tropical landscapes; chemical weathering rates are consistent with other Caribbean islands and high compared to global data.

In 2 basins, erosion rates calculated from duplicate measurements of 10Be (1.5 & 2.6 m/My) and 26Al (1.8 & 3.0 m/My) were ~50X lower than chemical denudation rates (89 & 108 m/My). Both 26Al and 10Be concentrations indicate long term, near-surface (>>100 ky) sediment residence; stream water geochemical data are consistent with the presence of evaporite deposits. We suspect that rapid chemical denudation enriches remaining sediment in quartz, which lingers at or near the surface in these low slope (0.5°) basins. The discrepancy between cosmogenic-based background erosion rates and chemical denudation rates highlights the importance of considering chemical denudation when examining landscape change, particularly in lithologies subject to chemical weathering.