Browsing by Author "Kermode, SJ"

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    ‘Age’, recharge rates and connectivity of groundwater in deeper aquifers of the Sydney Basin
    (Geological Society of Australia, 2014-07-07) Kermode, SJ; Cendón, DI; Hankin, SI; Russell, G
    The Permo-Triassic Sydney Basin covers almost 50 000 km2 and extends from the outer continental shelf inland to the Great Diving Range, from Newcastle in the north to Batemans Bay in the south. Major lithological units broadly include the Permian Coal Measures, the Permo-Triassic Narrabeen Group, the Triassic Hawkesbury Sandstone and the Wianamatta Shale. The Hawkesbury Sandstone is generally made of very thick heavily compacted quartz sands, with minor discontinuous shale units. Its aquifer system is a complex, dual porosity, deep fractured system with three aquifers typically recognised. The shallow and intermediate aquifers contribute to spring and base stream flows as well as groundwater dependent ecosystems, and the deep regional aquifer system. It is this deeper system that is investigated in this study. Groundwater from the Sydney Basin, and in particular Hawkesbury Sandstone aquifers, forms part of emergency supply strategies for coping with future severe droughts, with >5 million people living in the region, in addition to large industrial development. Despite the significance of these resources there are still large gaps in our knowledge of these aquifers including aspects such as age recharge and mixing rates. Filling these knowledge gaps has become even more critical in order to understand impacts of existing and planned coal and coal seam gas (CSG) mining of the underlying Illawarra Coal Measures. Community concerns over risks associated with CSG extraction have reached fever pitch in recent years, and there is public demand for research into these aquifers. Understanding of these systems has been complicated by the poor quality of existing data – commonly relying solely on driller bore-logs, reporting only being carried out for specific mine or extraction activities, and therefore conducted over localised zones, and the lack of communication between companies and agencies with data. Additionally, large variations in hydraulic properties have been noted over localised areas. This study sampled bores along a loosely east–west transect across urban Sydney, targeting the deeper Hawkesbury Sandstone and Narrabeen group aquifers. Very high salinities are recorded by several samples, interpreted to relate to the influence of the overlying Wianamatta Group and Cumberland Basin sediments in those locations. Equally however, this signal may record the impact of interaction with coal seams. Results also show inconsistencies between tritium and radiocarbon groundwater ‘ages’ in multiple locations, suggesting that extensive mixing occurs between aquifers. A relationship between bicarbonate, depth and δ 13C isotopic ratios highlights the influence of methanogenesis for deeper samples and either interaction with localised organic matter or deeper inputs derived from the coal measures. These findings have implications for potential coals seam gas extraction in the region, demonstrating that impacts could be significant in areas of high fracturing and connectivity. This supports previous assessments of groundwater vulnerability and the need for further detailed research. © Geological Society of Australia Inc
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    Another piece of the Southern Hemispheric puzzle: developing a high-resolution climate record for multiple glacial cycles in eastern Australia
    (International Union For Quaternary Research (INQUA), 2015-08-01) Kermode, SJ; Shulmeister, J; Mueller, D; Goralewski, J; Gadd, PS; Chang, J; Heijnis, H; Cohen, TJ
    Understanding likely climate change and subsequent environmental responses is critical to our long term ability to manage and mitigate such changes. Investigations of previous responses to notable (either abrupt or large scale) climate change provides boundary conditions and targets that can be used to both validate and parameterize the climate models used to predict future change. High-resolution records from the Southern Hemisphere lag considerably behind available data from the Northern hemisphere, and are particularly sparse in Australia. Given that most (>80%) of Australia’s population, industry and agriculture lie in the mid-latitudes between Southern Queensland and Tasmania, one might expect that past climate changes from this region are well understood, but this is not the case. Long, high resolution records are needed to address this gap. An 11 m core has been collected from a permanent swamp/lagoon (Mountain Lagoon), in the Blue Mountains west of Sydney, which appears to span at least one complete glacial cycle. This is potentially the most continuous record recovered from this part of SE Australia. Much of the record is at least moderately organic and preliminary sedimentary and Itrax data indicate that significant environmental changes are recorded. Multi-proxy investigations including pollen, diatoms, charcoal and phytoliths are planned and the chronology will be underpinned using OSL and radiocarbon dating. The focus of the investigation will be to develop climatologies for the Sydney region during the last glacial cycle. The Mountain Lagoon project will consequently contribute to understanding how climate systems in SE Australia respond to large scale global change on Milankovitch time scales. By determining the climate response in Australia to these changes we will help predict future response in rainfall and temperature to human-induced and natural climate change.
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    Debris flow dominated alluvial fans in the Victorian high country indicate that landscape denudation through the Holocene has been dominated by post-bushfire runoff events
    (Australasian Quaternary Association Inc, 2014-06-29) Marren, P; Kermode, SJ; Nyman, P
    Bushfires play a major role in shaping the Australian landscape. Whilst the role of fire in shaping and changing vegetation assemblages is relatively well understood, there is still debate about the significance of fire in driving landscape denudation, relative to other processes, such as major rainfall and flood events. Studies of post-fire landscape impact of recent bushfires indicate that the response is sensitive to the frequency and magnitude of extreme bushfires and intense rainstorms, with the greatest response occurring when storms occur in the post-fire period before vegetation has recovered. Where storm events occur shortly after a major bushfire, hillslope erosion is enhanced, due to debris flows and erosion of both primary hillslope sediment and sediment stored in hillslope channel networks. We excavated nine trenches, in five alluvial fans at the base of hillslopes on the floodplain of the Nariel valley, northeast Victoria. This area was burnt by the 1939 and 2003 bushfires, although some of the fans were unburnt in 2003. The trenches were up to 3.5 m deep, and in four cases intersected the underlying floodplain sediment at the base of the trench, indicating that they provide a full record of sedimentation for that sector of the fan. Fan stratigraphy consisted of sub-horizontal (parallel to the fan surface) units 0.3–0.5 m thick, with occasional units 1–1.2m thick, and cross-cutting channelized units. Debris flow deposits accounted for 80–90 % of the observed sediments, with water-laid gravels and soil units forming the remainder. Most soil layers were burnt, and most (but not all) debris flow units contained charcoal. A typical stratigraphy consisted of 6–8 debris flow units per fan, with four units containing a fire signature or overlying a burnt soil layer. Radiocarbon dating of the fireassociated units is underway: preliminary results will be reported at the AQUA meeting.
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    Determining the impact of the Holocene highstand at the coastal-fluvial interface, Shoalhaven River, south-eastern Australia
    (Wiley Blackwell, 2013-10-01) Kermode, SJ; Gibling, MR; Jones, BG; Cohen, TJ; Price, DM; Daley, JS
    With enhanced rates of sea-level rise predicted for the next century, the upstream extent of sea-level influence across coastal plains is a topic of public importance. Australian coastal rivers provide a testing ground for exploring this issue because the area is tectonically stable, was not glaciated, and experienced a Holocene highstand between 7.4 and 2ka of up to 1.5m above Australian Height Datum (AHD). In the Shoalhaven River of New South Wales, investigation of a confined bedrock reach at Wogamia, 32km inland, has identified a unit of dark, cohesive silt and sand with marine diatoms, shell fragments, and enhanced pyrite content, interpreted as estuarine. The unit is up to 13m thick, thickens downstream, and is overlain by fluvial channel and floodplain deposits. The estuarine unit on-laps a remnant Pleistocene terrace and extends to approximately +2.2m AHD. Optically stimulated luminescence (OSL) and radiocarbon ages suggest that estuarine deposition commenced prior to 7.8kacal bp, predating the highstand by similar to 500years, and that marine influence in the area continued to 5.3 +/- 0.7ka. During this period, a delta probably persisted at Wogamia, where a narrow upstream reach opens out, and subsequently advanced to fill the broad Shoalhaven coastal embayment. Although the effect of sea-level rise depends on many factors, the results suggest that, during a highstand at or above present sea level, a strong marine influence may extend for tens of kilometres inland and penetrate confined bedrock reaches landward of coastal embayments. © 2013, Wiley-Blackwell.
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    Modern depositional processes in a confined bedrock setting: benches of the Shoalhaven river
    (International Association of Geomorphologists, 2013-08-27) Kermode, SJ; Cohen, TC; Reinfelds, IV; Nanson, GC; Jones, BJ
    The lower Shoalhaven River provides an opportunity to examine bench processes in a confined setting. Stratigraphic analysis of trenches and augur holes, ground penetrating radar, Hec-RAS modelling and geochronological techniques combine to identify that benches of multiple levels along Bull Reach are composed of coarse material and have been extensively eroded and reworked by modern events. Kermode et al. (2012) established the long-term polycyclical nature of the higher alluvial surfaces (up to 193 ka in age), and this is contrasted with the youth of the lower inset alluvial surfaces, which are shown to be less than 270 years in age. This study evaluates the relative significance of both flood regime and effects of European settlement on the geomorphic effectiveness of high magnitude events and investigates the characteristics of bench formation in this confined setting. It characterises the nature of depositional events and the relationship between facies at an event scale. Using Hec-RAS modelling, events of different recurrence intervals are compared to explore the relative impact of varying flood magnitudes. The results bring into question the theory that inundation frequencies of these surfaces are constant, or associated with formative processes. © Authors
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    A ramsar-wetland in suburbia: wetland management in an urbanised, industrialised area
    (CSIRO Publishing, 2015-01-01) Kermode, SJ; Heijnis, H; Wong, HKY; Zawadzki, A; Gadd, PS; Permana, A
    Wetlands provide crucial services to support human populations and intrinsic environmental functioning. They are, therefore, recognised at higher-level global conservation treaties down to regional and local environmental management plans. Palaeorecords to understand preimpact conditions and ranges of natural variability are critical, alongside ongoing monitoring of ecosystem health for understanding important wetlands and determining long-term conservation strategies. They also enable effective analysis of human impacts. Towra Point Nature Reserve is an internationally significant wetland complex listed under multiple international conservation agreements, including the 1971 Ramsar Convention. It faces similar challenges to other coastal wetlands globally: sea level rise, changing shoreline conditions, and anthropogenic impacts. Its location within Sydney’s Botany Bay results in high potential for pollutants to enter the wetland complex. This makes ongoing monitoring of the ecosystem critically important. This study has found that arsenic, lead and zinc are relatively elevated in the southern part of the embayment, adjacent to an urban area, where concentrations are near to, or exceeding trigger levels (ANZECC/ARMCANZ 2000). In contrast, in the western part of the embayment contaminant levels are well below trigger values. We propose that these trigger levels should be adopted and incorporated into the Towra Point Plan of Management. © CSIRO 1996-2020
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    Recharge rates and connectivity of grouwater in deeper aquifers of the Sydney Basin
    (Geological Society of Australia, 2014-07-07) Kermode, SJ; Cendón, DI; Hankin, SI; Russell, G
    The Permo-Triassic Sydney Basin covers almost 50 000 km2 and extends from the outer continental shelf inland to the Great Diving Range, from Newcastle in the north to Batemans Bay in the south. Major lithological units broadly include the Permian Coal Measures, the Permo-Triassic Narrabeen Group, the Triassic Hawkesbury Sandstone and the Wianamatta Shale. The Hawkesbury Sandstone is generally made of very thick heavily compacted quartz sands, with minor discontinuous shale units. Its aquifer system is a complex, dual porosity, deep fractured system with three aquifers typically recognised. The shallow and intermediate aquifers contribute to spring and base stream flows as well as groundwater dependent ecosystems, and the deep regional aquifer system. It is this deeper system that is investigated in this study. Groundwater from the Sydney Basin, and in particular Hawkesbury Sandstone aquifers, forms part of emergency supply strategies for coping with future severe droughts, with >5 million people living in the region, in addition to large industrial development. Despite the significance of these resources there are still large gaps in our knowledge of these aquifers including aspects such as age recharge and mixing rates. Filling these knowledge gaps has become even more critical in order to understand impacts of existing and planned coal and coal seam gas (CSG) mining of the underlying Illawarra Coal Measures. Community concerns over risks associated with CSG extraction have reached fever pitch in recent years, and there is public demand for research into these aquifers. Understanding of these systems has been complicated by the poor quality of existing data – commonly relying solely on driller bore-logs, reporting only being carried out for specific mine or extraction activities, and therefore conducted over localised zones, and the lack of communication between companies and agencies with data. Additionally, large variations in hydraulic properties have been noted over localised areas. This study sampled bores along a loosely east–west transect across urban Sydney, targeting the deeper Hawkesbury Sandstone and Narrabeen group aquifers. Very high salinities are recorded by several samples, interpreted to relate to the influence of the overlying Wianamatta Group and Cumberland Basin sediments in those locations. Equally however, this signal may record the impact of interaction with coal seams. Results also show inconsistencies between tritium and radiocarbon groundwater ‘ages’ in multiple locations, suggesting that extensive mixing occurs between aquifers. A relationship between bicarbonate, depth and δ13C isotopic ratios highlights the influence of methanogenesis for deeper samples and either interaction with localised organic matter or deeper inputs derived from the coal measures. These findings have implications for potential coals seam gas extraction in the region, demonstrating that impacts could be significant in areas of high fracturing and connectivity. This supports previous assessments of groundwater vulnerability and the need for further detailed research.
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    Ten trenches:a science-art collaboration
    (MIT Press, 2013-01-02) Cohen, TJ; Cohen, MA; Kermode, SJ; Leggett, M
    Collaborative and cross-disciplinary research by a group of artists and scientists in an Australian rural setting generates data and ideas that form the basis of a wider understanding of the ramifications of global warming and cooling within the local, regional and national community. The work is viewed as an initial educational platform that will allow the public to see and understand the complexities of climate-based research. © 2020 The MIT Press