From Ooids to Extinction: Developing Physical Paleoenvironmental Proxies for Understanding Earth History

Abstract

The stratigraphic record harbors environmental signals from Earth's past, albeit distorted by the inevitable noise and disruptions of time. Deciphering these signals is crucial as they hold insights into past geological processes, environmental conditions, and the evolution of Earth's climate system. These signals are documented in both the physical and chemical composition of the rocks in the stratigraphic record. This dissertation aims to refine strategies for extracting valuable information from the physical components of the stratigraphic record, integrating these observations with geochemical data, to enable a more comprehensive understanding of Earth's past and its implications for the present and future. Chapter two presents a method that uses the Grinding Imaging and Reconstruction Instrument (GIRI) in conjunction with computer vision and 3D reconstructions to precisely and accurately measure granular objects embedded in rocks, with a specific focus on ooids. After describing the methodology, we demonstrate through three vignettes how improved measurements enhance environmental interpretations, estimates of geochemical parameters, and understanding of ooid growth. Chapter three presents surprising findings from 3D reconstructions of ooid growth laminations: ooids undergo less abrasion than previously believed. This finding highlights the significant influence of chemical conditions on ooid formation. With an improved understanding of ooid formation, we gain insights into long-standing questions about the location of ooid formation (the oolite problem), reconsider the conditions leading to the formation of giant ooids, and propose a model that establishes a connection between ooid abundance, seawater chemistry, and shallow water platform area during the Phanerozoic.

Chapter four integrates sedimentological observations, radiometric ages, and drone-derived astrochronology to constrain the position of the K--Pg boundary in the Potosi Basin of Bolivia. This study significantly narrows the search window for the K--Pg boundary, maps its occurrence across the Bolivian Altiplano, and indentifies the locations and environments of newly discovered fossil localities from the K--Pg of Bolivia.