Dissertation/Thesis Abstract

Optical Inspections and Scanning Electron Microscopy across the Cretaceous-Paleogene Boundary Deposit in Well-Core IPNH No. 2 from LaSalle Parish, Central Louisiana
by Muchiri, Eric, M.S., University of Louisiana at Lafayette, 2018, 98; 10826798
Abstract (Summary)

Much scientific knowledge already exists on the Cretaceous-Paleogene (K/Pg) Boundary Deposit from outcrop and shallow core near to outcrop. The significance of this study is to learn from the only deep-well core on land, from the northern Gulf of Mexico (GoM) known to preserve this deposit. This core was chosen because of its pristine (unweathered) condition. The aim was to characterize the portion of this core which was influenced by the Chicxulub Impact event 65.5 Ma to enhance the scientific knowledge of the K/Pg boundary. I hypothesized that this core represents three lithofacies: 1) pre-impact chalk, 2) mass wasting deposit and fall back material, 3) Midway Shale; and that the mass wasting deposit and fall back material were deposited as a direct result of the impact event. I tested these hypotheses by employing: 1) Macroscopic descriptions, 2) Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS) of selected portions, 3) 10% HCl treatment and microscopic descriptions of the resulting insoluble portions. The findings show that the core can be divided into three main sections in ascending order: 1) a lighter carbonate, 2) a darker carbonate, and 3) a black shale. From optical and SEM analysis, I find that the microfossils and ubiquitous coccoliths found throughout the carbonate sections of this core do not exist in the core above section 2. Section 2 is mostly a Chicxulub Impact induced mass wasting deposit. In order to investigate better the non-carbonate components of the core, representative portions were treated with 10% HCl, an investigative technique not commonly applied to cores of the K/Pg boundary. Under an optical microscope ,10% HCl insoluble portions from the K/Pg boundary reveal no regularly shaped impact spherules. I find no Si-rich spherules and posit that the spherules in this core are almost entirely, Ca-rich.

Indexing (document details)
Advisor: Kinsland, Gary
Commitee: Gottardi, Raphael, Pesacreta, Thomas C.., Schubert, Brian
School: University of Louisiana at Lafayette
Department: Geology
School Location: United States -- Louisiana
Source: MAI 58/05M(E), Masters Abstracts International
Source Type: DISSERTATION
Subjects: Nanoscience, Sedimentary Geology, Geochemistry
Keywords: Bolide impact spherules, Chicxulub Impact, Coccolithophores, Cretaceous-Paleogene (K/Pg) Boundary deposit (KPBD), Justiss LA Central IPNH No. 2, Scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), Target rock, Coccoliths, Heterococcoliths, Louisiana, LaSalle Parish
Publication Number: 10826798
ISBN: 978-1-392-04162-8
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