Year

2021

Degree Name

Bachelor of Environmental Science (Honours)

Department

School of Earth, Atmospheric and Life Sciences

Advisor(s)

Dr Lloyd White

Abstract

Throughout history, there has been extensive research performed on the Hawkesbury Sandstone, however, little has been done within academic literature on the fracture networks throughout it, specifically on their influence on groundwater flow and storage. The regional deformation is also believed to be due to basement control, with little research performed on alternate theories of deformation. This study aims to develop a better understanding of the fracture networks in the Hawkesbury Sandstone and how fractures may contribute to the flow pathways between underground and groundwater systems. It also aims to determine the possibility of an alternate theory for regional deformation, in the form of detachment folding. This study was conducted on the Southern Highlands of New South Wales, with a key focus on three rock outcrops at Yanderra. Photogrammetry models were developed which were then uploaded to a 3D geological software program (IPM-MOVE™) for geological interpretation. The established mesh surfaces were interpreted to develop cross-sections and quantitative results, with a particular focus on fracture length and spacing at each outcrop. The acquired fracture measurements, along with three test apertures were used to develop a conceptual model of the porosity and hydraulic conductivity of fracture networks within each outcrop. The calculated porosity of the fractures in the Hawkesbury Sandstone, based on observed fracture length, ranged from 0.001-0.011% with three different apertures, while the conceptual model based on fracture spacing ranged from 0.001-0.022%. The expected hydraulic conductivity of fractures ranged from 0.040 m/day to 15.64 m/day. The depth to detachment was calculated to be approximately 325 metres, which indicates a detachment layer is possibly within the Illawarra Coal Measures. Fractures are a clear host to fluid movement through rock outcrops. Longwall mining can cause movement on existing fractures due to subsidence, and thus, have implications for the movement of groundwater throughout them. This could have the potential to affect recharge within aquifers throughout the Sydney Basin and should be considered in future fracture studies and mining operations.

FoR codes (2008)

040312 Structural Geology

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Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.