Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Master of Science

Program

Geology

Supervisor

Longstaffe, Fred

Abstract

The paleolimnology of North America’s Lake Huron is described using lead-210 dating, mineralogy, magnetic susceptibility, total organic carbon (TOC), total nitrogen (TN), carbon:nitrogen (C/N) ratio, grain size, and the δ13COM and δ15NTN of organic matter. Sediment cores from Lake Huron’s 6 depositional basins and Georgian Bay span the Medieval Warm Period, Little Ice Age, and Canadian-European settlement. The main organic matter source is lacustrine algae, as indicated by δ13COM, δ15NTN and C/N. Prior to the 19th century, primary production changes are reflected only by small variations in TOC and TN. A gradual increase in δ15NTN (~1.1 ‰) suggests an increase in primary production since the start of the Industrial Revolution, likely due to warming and rising nutrient input. Deforestation, primarily during the 19th century, contributed to a rise in TOC in the Huron basin. Further land clearance likely caused a prominent increase in magnetic susceptibility during the early- to mid-20th century.

Summary for Lay Audience

The environmental history of Lake Huron and Georgian Bay was reconstructed by measuring different components preserved in sediment cores. The sediment cores were collected from 7 different locations in the lake. The sediment records periods of natural climate change, including the Medieval Warm Period and the Little Ice Age. The impact of human activity since the Industrial Revolution is also recorded in the sediment. The main contributor of organic matter in the sediment is algae, which was indicated by the isotope composition and the ratio of carbon to nitrogen. Increasing temperature and rising nutrient input since the Industrial Revolution likely increased the quantity of algae being produced. Deforestation, primarily during the 19th century, contributed to a rise in organic carbon. Further land clearance due to human settlement and urbanization caused a significant increase in material, including magnetic minerals, entering Lake Huron during the early- to mid-20th century.

Available for download on Sunday, May 01, 2022

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