Date of Award

Spring 4-25-2014

Degree Type

Thesis

Degree Name

MS Biology

Department

Biology

Advisor

Michael Zavada, Ph.D

Committee Member

Rhonda Quinn, Ph.D

Committee Member

Angela Klaus, Ph.D

Committee Member

Allan Blake, Ph.D

Committee Member

Jane Ko, Ph.D

Keywords

Miocene, Llanos Basin, Colombia, Marine Incursions

Abstract

The distal Llanos foreland basin was influenced by subsidence events since the Cretaceous until the Pliocene. Although this area has been extensively explored and is considered a potential oil reservoir, few studies of its stratigraphy and depositional environments have been conducted. This basin exhibits a geological section of Miocene age and the core Saltarin-1A, analyzed in this study, is the first and most complete drilling coreof this section with 680 meters. It represents to Carbonera, Leon and Guayabo Formations. Based on palynological data, this work has as its main aims to review the biostratigraphy, to identify the depositional environments, including those produced by marine incursions and to understand the history of the vegetation of the basin. A total of 115 palynological samples was counted, with a minimum of 300 palynomorphs per slide when possible. The core was dated from 22 to 5 My based on the graphic correlation and Maximum likelihood methods. Carbonera and the base of Leon Fms were deposited during the lower Miocene, Leon and Guayabo Fms (units 1, 2 and 3), during the middle Miocene, and the top of Guayabo Fm (units 4, 5) during the upper Miocene. In addition, three mayor marine incursions were detected during Miocene. Coeval marine transgressions have been also documented in the Central Llanos Foothills, Caribbean and Amazonia during the lower and middle Miocene. During the upper Miocene, the palynological composition indicates a change in the rate of sedimentation and in the drainage of the basin indicating possible formation of the Orinoco river. At this time the pollen showed and increase in the open vegetation. These data support previous works, which indicate an increase in the rates of deformation of the basin as well as erosion at the end of the Miocene. Finally, the palynoflora suggests the presence of a wet forest during the Miocene instead of the biomes that characterize the basin nowadays. These new data are important to understand the evolution of the Llanos Basin in relation with Andean uplift and the evolution of the Neotropics.

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