Climate, taphonomy, and vertebrate community structure in the John Day Fossil Beds: a GIS-based analysis

Project Abstract

The Eocene–Oligocene transition was a major interval of global cooling, increasing aridity, and ecological reorganization. This study evaluates the relative influence of climatic change and taphonomic processes on vertebrate assemblage composition across the Eocene–Oligocene transition in the John Day Basin, Oregon, using fossil specimens and locality records from the Clarno and John Day formations. Fossil occurrence and specimen data from museum collections were analyzed using Geographic Information Systems (GIS), taphonomic metrics, and ecological classifications. Skeletal elements were categorized by Voorhies transport group, weathering stage, fragmentation, body size, locomotor mode, and dietary ecology. GIS analyses integrated fossil occurrences with topographic, hydrologic, vegetation, and accessibility variables to evaluate spatial patterns in fossil distribution. Preliminary taphonomic analyses indicate differences in skeletal representation between formations, with Clarno assemblages exhibiting lower element diversity and John Day assemblages showing more even representation across skeletal elements. Locomotor guild composition differed significantly between formations (χ² = 47.67, p < 0.001), with cursorial and fossorial taxa occurring exclusively in sampled John Day assemblages and aquatic taxa restricted to Clarno localities, suggesting a shift toward more open and seasonally variable habitats. Dietary guild composition also differed significantly between formations (χ² = 59.96, p < 0.001), and dietary diversity was higher in John Day assemblages (H′ = 1.80) than in Clarno assemblages (H′ = 1.34). Predictive modeling identified spatial clustering of fossil occurrences associated with environmental variables and proximity to roads and trails. These results indicate that climatic reorganization during the Eocene–Oligocene transition coincided with measurable changes in vertebrate community structure, while taphonomic variation influenced patterns of skeletal representation. Integrating GIS-based predictive modeling with quantitative taphonomy improves discrimination between ecological turnover and taphonomic effects and provides a framework for interpreting terrestrial vertebrate fossil assemblages in the John Day Basin and comparable fossil systems.

Conference Name

Society of Vertebrate Paleontology

Conference Details

Society of Vertebrate Paleontology https://vertpaleo.org/2026-annual-meeting/ 

Funding Type

Travel Grant

Academic College

Jesse D. Jones College of Science, Engineering and Technology

Area/Major/Minor

Earth & Environmental Sciences

Degree

Masters Degree

Classification

Graduate

Name

Dr. Katharine Loughney

Academic College

Jesse D. Jones College of Science, Engineering and Technology

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