Date of Award

Spring 2025

Document Type

Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Ocean & Earth Sciences

Program/Concentration

Oceanography

Committee Director

Nora Noffke

Committee Member

Murray Gingras

Committee Member

Matthew Schmidt

Abstract

Digital outcrop models generated by high-resolution photogrammetric imagery permit investigations into organism-substrate interactions at the centimeter to sub-millimeter scale. This dissertation uses this three-dimensional technology to study two sedimentary successions— the Archaean Dresser Formation and Cretaceous Dakota Sandstone— by capturing images via unmanned aircraft systems and single lens reflex cameras. The ~3.48 Ga Dresser Formation provides evidence for some of the earliest life on Earth in the form of stromatolites and microbially induced sedimentary structures. Aerial imagery of the 3.5 km2 Buick Geoheritage reserve capture the site’s geologic structures and close-range imagery documents stromatolites and several microbially induced sedimentary structures (microbial mat chips and fragments, mat curls, and erosional remnants and pockets).

The Cretaceous (Cenomanian) Dakota Sandstone at the Dinosaur Ridge National Natural Landmark contains some of the most famous dinosaur trackways North America. A process-based ichnologic framework is used to study the distribution of invertebrate trace fossils across paleotopographic highs and lows generated by erosional remnants and pockets within a fossilized supratidal flat. Digital outcrop models of exposures permitted the discovery of 26 new non-avian theropod dinosaur courtship display scrapes (Ostendichnus bilobatus) and the first described horseshoe crab traces and trackways (Crescentichnus and Selenichnites) on 4 additional sedimentary surfaces. For Ostendichnus, a new means to determine the direction the trace maker faced while creating the scrapes is proposed for traces lacking footprints, anterior divergence of claw marks, posterior tapering of troughs and a sand crescent pile of excavated sediment at the posterior of the trace. Analysis of the Dinosaur Ridge sites and of 3 previously known lek sites in western Colorado—Club Gulch (n = 2) and Roubideau Creek— permit insight into the social behavior of the trace making theropods by comparisons to modern avian analogs.

These datasets will enable researchers to perform remote site evaluations, provide outreach and educational materials, and serve as a baseline for resource management and conservation efforts. Future aerial datasets allow monitoring of erosion and vandalism within the geoheritage reserve over time. This study provides valuable insights into the early evolution of life and contributes to our understanding of potential life on other planets.

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DOI

10.25777/a8n7-ye02

ISBN

9798280752481

ORCID

0000-0002-2726-1783

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