Date of Award

Spring 2019

Project Type

Thesis

Program or Major

Earth Sciences

Degree Name

Master of Science

First Advisor

William C Clyde

Second Advisor

Tyler R Lyson

Third Advisor

Joel E Johnson

Abstract

The Cretaceous-Paleogene (K-Pg) boundary interval represents one of the most significant periods of biological turnover in Earth history. Earliest Paleocene fossil mammal faunas corresponding to the Puercan North American Land Mammal Age (NALMA) are thought to be highly endemic and potentially diachronous, necessitating precise chronostratigraphic controls at key fossil localities to constrain recovery dynamics following the K-Pg mass extinction. The Laramide synorgenic sediments within the Denver Basin preserve one of the most continuous and fossiliferous records of the K-Pg boundary interval in North America. However, poor exposure in much of the Denver Basin makes it difficult to correlate outcrops via surface exposure. In order to relate fossil localities across the basin, previous studies have relied upon chronostratigraphic methods such as magnetostratigraphy. Here we present a new high-resolution magnetostratigraphy of 10 lithostratigraphic sections spanning the K-Pg boundary interval at Corral Bluffs located east of Colorado Springs in the southern part of the Denver Basin. Fossil localities from Corral Bluffs have yielded limited dinosaur remains, mammal fossils assigned to the Puercan NALMA, and numerous fossil leaf localities. Palynological analysis identifying the K-Pg boundary in three sections and a new 66.253 ± 0.031/0.045/0.084 Ma 206Pb /238U ash date, provide key temporal calibration points. Our paleomagnetic analysis has identified clear polarity reversal boundaries from Chron C30n to Chron C28r across the sections. It is now possible to place the fossil localities at Corral Bluffs within the broader basin-wide chronostratigraphic framework and evaluate them in the context of K-Pg boundary extinction and recovery.

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