ARCHITECTURAL ELEMENT ANALYSIS OF GLACIATED TERRAINS

Abstract

This thesis investigates how architectural element analysis (AE) can be utilized to deconstruct the sedimentary architecture of glacial sedimentary successions, and its significance for paleoenvironmental reconstruction, understanding depositional histories, and providing insight to the hydrostratigraphy of glaciated terrains. The first component of this thesis explores the applicability of AEA to the local-scale analysis of a till succession exposed in outcrop sections in order to understand the significance of the bounding surface hierarchy and architectural elements in sediments deposited in a subglacial depositional environment. Fieldwork was conducted at two outcrop sites in north-central Illinois, U.S.A., which expose Late Wisconsin-age till of the Tiskilwa Formation, in order to test the local-scale applicability of AEA to the architectural analysis of a subglacial succession (Chapter 2). A major finding of this study was that fifth-order bounding surfaces delineate ‘element associations’ which can be mapped across the local study area, and utilized for detailed paleoenvironmental reconstruction of the ‘subglacial bed mosaic’ and local-scale reconstruction of the depositional history of the till sheet, including periods of separation and reattachment of the ice and its bed. The second part of this research explores AEA at Sólheimajökull (Iceland), specifically to test the validity of AEA for the analysis of glacial successions, and to better understand the environmental significance of unit contacts (bounding surfaces) and sedimentary geometries in a modern glacial landscape. Fieldwork was conducted at Sólheimajökull and basic principles of AEA and landsystems analysis were integrated in order to facilitate delineation of the sedimentary architecture and allostratigraphy of the Sólheimajökull landsystem (Chapter 3). Fifth-order surfaces delineate landsystem tract components, which can be utilized to characterize the heterogeneity and sedimentary architecture, delineate allostratigraphic units, and reconstruct the depositional hist¬ory of the Sólheimajökull landsystem. Data from Sólheimajökull (Chapter 3) and Illinois (Chapter 2) were utilized as a modern and outcrop analogue, respectively, to provide insight to the sedimentary architecture of subsurface Quaternary glacial deposits in Georgetown, southern Ontario (Canada; Chapter 4). Basic concepts of AEA were applied to the analysis of sediments recovered from fully-cored boreholes. A major finding of this study is that AEA can be effectively utilized for delineation of subsurface architectures from the analysis of core, and the hierarchies of bounding surfaces and units of AEA can be utilized to organize the sedimentary heterogeneity into a ‘nested’ architectural framework. The geometry and spatial relationship of architectural units (sixth-order surfaces) and architectural components (fifth-order surfaces) provides insight to the hydrostratigraphy of Georgetown. AEA, as utilized in this thesis, provides a systematic methodology with which to deconstruct glacial successions into their basic architectural building blocks at various scales of resolution. AEA enhances traditional facies models by facilitating site-specific delineation, visualization, and characterisation of the sedimentary geometry of facies associations, which in turn, allows direct comparison of sedimentary architectures at different study sites; this has significant implications for analogue selection for the purpose of reservoir analysis. The architectural framework of glacial deposits and its potential significance to hydrostratigraphic models (as discussed in this thesis) may help to facilitate communication and translation of data between the disciplines of ‘geology’ and ‘hydrogeology’. The results of this project can be utilized as a framework to better understand the sedimentary geometry and hydrostratigraphy of modern and Quaternary glacial deposits in southern Ontario, previously glaciated terrains elsewhere, and other modern glacial landsystems, and provide insight into other applications such as civial engineering projects, aggregate resources, placer mining exploration, and land use planning.