Walking with Elephants: Quantifying the Impact of Megafaunal Tracks from Sedimentary Properties

Brian F. Platt¹ and Stephen T. Hasiotis^2
1Department of Geology, University of Kansas, Lawrence, KS
²Department of Geology and Natural History Museum and Biodiversity Research Center, University of Kansas, Lawrence, KS

The purpose of our research is to use neoichnological experiments with elephants to quantify the relationship between footprint-forming variables, which can be applied to beds containing fossil tracks to interpret original sedimentary properties. We work with one African elephant (Loxodonta africana) and one Asian elephant (Elephas maximus) at the Topeka Zoo, Topeka, Kansas. In each experiment, an elephant is walked through a pit filled with sediment of known grain size. Sediment moisture and density are varied and measured with a nuclear density gage. Elephant weight and walking speed are also measured. We take measurements and make plaster casts of footprints to determine their volumes; we use track volume because it accounts for both track depth and surface area of the foot.

We performed multiple regression analysis to quantify the relationship between such independent variables as sediment grain size, sediment moisture, sediment density, walking speed, and elephant weight and the dependent variable of footprint volume; this yields an equation that can be solved for any one unknown. We found that speed during a constant gait does not significantly influence the dependent variable. Our results also show that sediment density significantly affects footprint volume; vertebrate ichnologists should consider this when interpreting original sedimentary properties from fossil megafaunal footprints.

In a preliminary exercise, we solved the regression equation for moisture content and applied it to a fossil sauropod dinosaur track from a sandstone in the Upper Jurassic Morrison Formation. Percent moisture of the original sand deposit was calculated to be 30%, which is very close to total saturation and consistent with track morphology and preservation.

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas