An Overview
Major: Geoscience
Academic Affiliation: Florida International University
Biography
Gaby was born and raised in Miami, Florida surrounded by palm trees and dreaming of volcanoes. Her love for mineralogy and crystallography led her to pursue a major in Geoscience at Florida International University.
Abstract
Investigation of paleolake environment in the Late Miocene, Nebraska
Fresh water diatom deposits of grasslands may hold the key to understanding the connection between diatom evolution, development of grasslands and global climate. While the interaction between these parameters hinges on the silica cycle, the interactions have yet to be adequately explored, particularly in the Late Miocene. For this study, we investigated a core section from the Ogallala Formation, representing 10.6 feet of paleolake sediment. The objective of the study was to 1) Estimate the period of time that the paleolake existed. 2) Examine changes in stratigraphic markers, the planktonic taxa Strelnikoviella and Aulacoseira and the benthic taxa Tetracyclus and Surirella, to determine the ecologic setting. 3) Examine phytoliths and volcanic ash to determine the regional sources of silica to the lake. The core was divided into 22 sections and sub samples were digested using nitric acid. Four replicate, quantitative slides were created and a light microscope was used to determine total diatom valves, volcanic ash, phytoliths and stratigraphic marker species per mg of dry weight sediment. Sedimentation rates of modern lakes were used to estimate a sedimentation rate for the paleolake. The paleolake was determined to be comparable to modern lakes with low to moderate productivity levels, making the estimate of the core’s age to be 5,000-10,000 years old. The ecologic setting changed throughout the core from a turbid, shallow environment to one with more transparent waters. No phytoliths were recorded inthe core section, but volcanic ash was present throughout and increased dramatically at the top of the section, perhaps causing the lake to fill and terminate the lake’s existence.