The Patonga Claystone, a red bed facies in the Narrabeen Group of the Sydney Basin, is one of the most unfavorable rock units in the basin from a geotechnical point of view. This rock unit is composed of sandstone, siltstone, mudstone and claystone. One of the unfavorable characteristics is the low shear strength, which causes instability of cut slopes; another is its slaking-prone behaviour. Numerous measurements of geotechnical properties, along with extensive mineralogical and geochemical determinations, were carried out to identify cause of this slaking behaviour. Key techniques were the use of quantitative X-ray diffractometry for mineralogical analysis, and the determination of slake durability index and related properties to evaluate the slaking behaviour under both standard and more extended conditions. Standard (two cycle) slake durability test results indicate a range from low to high slake durability index values, with some mudstone samples having very low durability and some sandstones having very high slake durability indices. Jar slake test results indicate that the rock samples break rapidly and/or develop several fractures (Ij = 4) in an as-received state, but degrade to a pile of flakes or mud (Ij = 1) if the samples are oven dried before testing. The results for jar slake testing of oven-dried material are comparable, for individual samples, to those obtained from the more comprehensive slake durability tests. The mineralogy of the samples was evaluated by quantitative X-ray diffraction techniques using the Rietveld-based Siroquant processing system. Comparison to independent chemical data show a generally good level of agreement, suggesting that the mineralogical analysis results are consistent with the chemical composition of the individual rock samples. Good correlations were also obtained between clay mineralogy determined from orientedaggregate XRD analysis of the &lt2 micron fraction and the results from powder diffractometry and Siroquant analysis of the whole-rock samples. Evaluation of the slake durability characteristics and other geotechnical properties in relation to the quantitative mineralogy suggests that quartz and feldspar form a rigid framework in the rocks that resists the disruptive pressures that cause slaking. Expansion of the clay minerals by various processes, including the incorporation of water into the interlayer spaces of illite/smectite as well as changes in pore pressures associated with entry of water into micro-fractures in the clay matrix, are thought to produce the disruptions that cause slaking and degradation. An abundant clay matrix also reduces the strength of the rock materials, probably because of the less rigid nature of the clay minerals relative to the quartz and feldspar particles. As well as the mineralogy, the loss on ignition (LOI) and water absorption percentage were found to provide good indicators of longer-term slaking behaviour. Both properties are also related to the overall clay content. Rock samples with water absorption values of &lt10, 10-15 and &gt15% behave as highly durable, intermediate and less durable materials respectively. Rocks with LOI values of greater than 5% by weight behave as less durable rock materials, at least for the strata encompassed by the present study. The water absorption and LOI values were also used to develop a predictive model of slake durability characteristics for the different rock materials in the Patonga Claystone, providing a relatively simple basis for predicting longer-term stability in a range of geotechnical studies.

The Patonga Claystone, a red bed facies in the Narrabeen Group of the Sydney Basin, is one of the most unfavorable rock units in the basin from a geotechnical point of view. This rock unit is composed of sandstone, siltstone, mudstone and claystone. One of the unfavorable characteristics is the low shear strength, which causes instability of cut slopes; another is its slaking-prone behaviour. Numerous measurements of geotechnical properties, along with extensive mineralogical and geochemical determinations, were carried out to identify cause of this slaking behaviour. Key techniques were the use of quantitative X-ray diffractometry for mineralogical analysis, and the determination of slake durability index and related properties to evaluate the slaking behaviour under both standard and more extended conditions. Standard (two cycle) slake durability test results indicate a range from low to high slake durability index values, with some mudstone samples having very low durability and some sandstones having very high slake durability indices. Jar slake test results indicate that the rock samples break rapidly and/or develop several fractures (Ij = 4) in an as-received state, but degrade to a pile of flakes or mud (Ij = 1) if the samples are oven dried before testing. The results for jar slake testing of oven-dried material are comparable, for individual samples, to those obtained from the more comprehensive slake durability tests. The mineralogy of the samples was evaluated by quantitative X-ray diffraction techniques using the Rietveld-based Siroquant processing system. Comparison to independent chemical data show a generally good level of agreement, suggesting that the mineralogical analysis results are consistent with the chemical composition of the individual rock samples. Good correlations were also obtained between clay mineralogy determined from orientedaggregate XRD analysis of the &lt2 micron fraction and the results from powder diffractometry and Siroquant analysis of the whole-rock samples. Evaluation of the slake durability characteristics and other geotechnical properties in relation to the quantitative mineralogy suggests that quartz and feldspar form a rigid framework in the rocks that resists the disruptive pressures that cause slaking. Expansion of the clay minerals by various processes, including the incorporation of water into the interlayer spaces of illite/smectite as well as changes in pore pressures associated with entry of water into micro-fractures in the clay matrix, are thought to produce the disruptions that cause slaking and degradation. An abundant clay matrix also reduces the strength of the rock materials, probably because of the less rigid nature of the clay minerals relative to the quartz and feldspar particles. As well as the mineralogy, the loss on ignition (LOI) and water absorption percentage were found to provide good indicators of longer-term slaking behaviour. Both properties are also related to the overall clay content. Rock samples with water absorption values of &lt10, 10-15 and &gt15% behave as highly durable, intermediate and less durable materials respectively. Rocks with LOI values of greater than 5% by weight behave as less durable rock materials, at least for the strata encompassed by the present study. The water absorption and LOI values were also used to develop a predictive model of slake durability characteristics for the different rock materials in the Patonga Claystone, providing a relatively simple basis for predicting longer-term stability in a range of geotechnical studies.

"1990". / Thesis (PhD)--Macquarie University, School of Earth Sciences, 1991. / Bibliography: p. 596-630. / PART 1. INTRODUCTION AND METHODOLOGY -- General introduction -- Methodology -- Classification of ichnofacies and lithofacies as used in the present study -- Definition of trace fossil zones (intervals, subintervals and levels) -- General classification of the palaeoenvironments and summary overview of the stratigraphic and geographic distribution of palaeoenvironments in the study area -- PART 2. SYSTEMATIC ICHNOTAXONOMY -- Large dwelling-burrows -- U-shaped burrows -- Vertical cylindrical burrows -- Thalassinoides, Ophiomorpha, Spongeliomorpha and turn-arounds -- Pellets and ovoid-shaped structures -- Bedding-parallel feeding and/or dwelling structures -- Dendritic feeding-burrows -- Rosette-shaped structures -- Escape-structures -- Tracks, trails and resting-traces -- Body fossils and root-penetration structures -- Miscellaneous traces -- PART 3. SYNTHESIS AND CONCLUSIONS -- Trace fossil assemblages (suites) in intervals IC to IF and their distribution in the study area -- Interpretation of the palaeoenvironmental affinities of the trace fossil zones and depositional setting of the study area -- Palaeogeographic synthesis and conclusions. / The coastal exposures of the Triassic System in the Sydney Northshore area aggregate about 180 m in thickness and comprise the uppermost part of the Narrabeen Group (namely, in ascending stratigraphic order: the Bald Hill Claystone, the Garie Formation, and the Newport Formation, the latter divisible into Lower, Middle and Upper Members) and the overlying Hawkesbury Sandstone. With the exception of mainly allochthonous plant macrofossils and palynomorphs which occur sporadically and with varying abundance in the mudrock facies of these formations, environmentally-diagnostic body fossils are rare, and, where they occur, are nowhere unequivocally indicative of marine affinities. For this reasons, and because of the predominantly fluvial lithofacies characteristics exhibited by these formations throughout much of their stratigraphic extent and especially by their channel-form/channel-like sandstones lithosomes, most previous workers have interpreted these formations to be of fluvial or fluvio-lacustrine origin except possibly for several thin planar-and thinly-bedded fine-grained intervals encompassing the Garie and Newport Formations for which several lines of evidence, including lithofacies, equivocal palaeontological, and ichnological evidence, have prompted several workers to speculate a shallow- marine, possibility coastal lagoonal or estuarine origin. -- Although trace fossils occur in reasonable abundance at various stratigraphic levels within these uppermost Narrabeen Group rocks and particularly within the Newport Formation, they have hitherto received very little systematic study. A comprehensive study of this ichnofauna shows that it is relatively diverse, comprising almost 100 different ichnotaxa (including varietal categories) of predominantly invertebrate origin, and includes several new ichnogenera and ichnospecies among the more notable of which are: two large bioglyph-bearing dwelling-burrows of probable crustacean origin (Turimettichnus conaghani and T. webbyi) and one (Pytiniichnus trifurcatum) made either by a small reptile or an amphibian; a multi-stage spiral star-shaped feeding-trace (Helikospirichnus veeversi), probably made by a worm or worm-like deposit-feeder; several new species and varieties of Rhizocorallium (the first record of this ichnogenus in the Triassic of Australia); a new species and new variety of the saltatorial running vertebrate trackway Moodieichnus (an ichnogenus previously known only from the Late Permian of North America); and a new ichnogenus of vertical/steeply-inclined cylindrical branching dwelling-burrow (Barrenjoeichnus mitchelli). -- An alternating stratigraphic pattern of trace fossil abundance and diversity characterizes the upper Narrabeen Group strata in the Sydney Northshore area, and involves four relatively thin separate assemblage zones of relatively diverse ichnofauna and thicker intervening assemblage zones which lack ichnotaxo-nomic diversity. The assemblage zones of diverse trace fossils contain some elements in common to two or more zones, notably: Thalassinoides, Skolithos, Ophiomorpha, Chondrites, Rhizocorallium Palaeophycus, and Planolites, all of which are known to have unequivocal brackish- to shallow-marine palaeoecological affinities and which globally are characteristic of the Skolithos ichnofacies. Additionally, each of these four diverse assemblage zones is characterized by one or more particular index ichnogen-era which for convenience lend their name(s) to the zones as follows, in ascending stratigraphic order: Turimettichnus-Ophio-morpha assemblage zone; Skolithos-Diplocraterion assemblage zone; Helikospirichnus assemblage zone; and Rhizocorallium-Thalass inoides assemblage zone. The intervening ichnotaxonomically less-diverse and relatively impoverished assemblage zones are not similarly and separately named but are characterized by Barrenjoeichnus mitchelli and some species of Palaeophycus, Planolites and Skolithos as well as various plant-root petrification structures, all of which are here argued to have predominantly non-marine palaeoecological affinities. These latter assemblage zones can be referred to the Scoyenia-Teredolites ichnofacies. This stratigraphic pattern of alternating ichnologi-cally diverse and impoverished assemblage zones confirms the suggestions of previous workers (notably Bunny and Herbert, and Retallack) regarding the presence of brackish-/shallow-marine palaeoenvironmental influence in these Lower and Middle Triassic strata and allow for the first time the stratigraphic resolution of the marine strata into four marine tongues which are here named after their respective type localities. These are, in ascending order: The Turimetta Head Tongue (2 m to 3 m thick; extending from at least the middle part of the Bald Hill Clay-stone almost to the top of this formation); the St. Michaels Cave Tongue (4 m to 5 m thick; encompassing the Garie Formation and the lower part of the lower Member of the Newport Formation); the Bangalley Head Tongue (3 m to 5 m thick; extending from the uppermost part of the Lower Member into the lower part of the Middle Member of the Newport Formation); and the Palm Beach Tongue (3 m to 4 m thick; comprising the uppermost part of the Middle Member of the Newport Formation). The trace fossil assemblages in each of these marine tongues are indicative of a complex of brackish- to very shallow-marine low-energy palaeoenvi-ronments typical of modern coastal lagoons or estuaries and imply the presence of a protecting coeval topographic barrier of some kind to the east or southeast. This lagoon is herein called the Newport (Coastal) Lagoon and its development in the central-eastern part of the Sydney Basin coincides approximately with the geographic and depocentral axis of the basin which trends NW-SE and intersects the present coastline in the Sydney metropolitan area. The non-marine affinities of the impoverished and less-diverse trace fossil assemblages in the intervening and overlying strata are consistent with the fluvial/fluvio-lacustrine environmental interpretations of these thicker and predominantly sandstone-dominant intervals made by many other workers. Palaeocur-rent and petrographic data from these fluvial sediments show that the streams in which they formed debouched episodically into the Newport Lagoon variously from the northwest, west and southwest and were sourced variously from both the craton (Lachlan Fold Belt) to the southwest and the New England Orogen to the northeast. / With the exception of evidence of short-lived brackish-marine conditions at the base of the Narrabeen Group in the northeastern Sydney Basin and in the top of the Ashfield Shale in the Wianamatta Group (above the Hawkesbury Sandstone) in the central part of the basin, the Triassic System of the basin is dominated by fluvial/fluvio-lacustrine sediments and the presently described marine tongues of the Newport Lagoon in the uppermost Narrabeen Group are the only other presently known record of marine conditions during the Triassic history of the basin. The development of the Newport Lagoon in the geographic and depocentral axis of the basin attests to the presence of a mild short-lived marine transgression in the latest Early and early Middle Triassic at the end of a period of declining piedmont clastic alluviation from the coeval New England Orogen to the northeast and immediately prior to the onset of a new phase of fluvial sedimentation sourced from the craton to the southwest and manifested by the deposition of the Middle Triassic Hawkesbury Sandstone. / Mode of access: World Wide Web. / xxxv, 630 p. ill., maps

The vegetation of the Sydney Basin, Australia, is highly flammable and subject to a wide range of fire regimes. Sclerophyllous shrubs and sedges are common and in some vegetation types up to 70 % of fuel consumed during a fire can be live. Research into fire behaviour and fuel dynamics has been minimal. To address this issue this thesis investigated the principal factor affecting the ease of ignition and rate of combustion of individual fuel particles and fuel beds in bushfires: dead fine fuel moisture (FFM). Two common Sydney Basin vegetation types, eucalypt woodland and heathland, each with a history of problematic fire management, were measured in the field for diurnal fluctuations in FFM following rain, under conditions similar to when prescribed burns are conducted. The FFM components of current operational fire behaviour models were found to be inadequate for predictions of FFM and fire behaviour under these conditions. The equilibrium moisture content (EMC) of five fuel types from the field site was investigated in a laboratory study. An existing function describing EMC as a function of temperature and relative humidity was evaluated and found to be very accurate for these fuels. Two FFM predictive models incorporating this function were evaluated on the field data and the laboratory results were shown to be applicable to the estimation of FFM in the field. One model gave very accurate predictions of FFM below fibre saturation point, but its accuracy was reduced when screen level conditions were used instead of those measured at fuel level. A recent process-based model that accounts for rainfall showed promise for predicting when fuel is < 25 % FFM. Systematic problems with the radiation budget of this model reduced the accuracy of predictions and further refinement is required. Live fine fuel moisture content (LFMC) of common heathland shrubs and sedge was investigated over two years and found to be both seasonal and influenced by phenology. LFMC minima occurred in late winter and spring (August to October), and maxima were in summer (December to February) when new growth was recorded. The dominant near-surface fuel in mature heath was sedge. It was found to have little seasonal variation in its??? percentage dead but the percentage dead maxima occured at the same time as the LFMC minima of shrubs and sedge in both years. Simple instantaneous models for duff moisture content in woodland and heathland and LFMC and the percentage dead sedge in heathland were developed. The information gained by this study will form the basis for future development of fuel moisture models for prescribed burning guidelines and fire spread models specific to the vegetation communities of the Sydney Basin.

The vegetation of the Sydney Basin, Australia, is highly flammable and subject to a wide range of fire regimes. Sclerophyllous shrubs and sedges are common and in some vegetation types up to 70 % of fuel consumed during a fire can be live. Research into fire behaviour and fuel dynamics has been minimal. To address this issue this thesis investigated the principal factor affecting the ease of ignition and rate of combustion of individual fuel particles and fuel beds in bushfires: dead fine fuel moisture (FFM). Two common Sydney Basin vegetation types, eucalypt woodland and heathland, each with a history of problematic fire management, were measured in the field for diurnal fluctuations in FFM following rain, under conditions similar to when prescribed burns are conducted. The FFM components of current operational fire behaviour models were found to be inadequate for predictions of FFM and fire behaviour under these conditions. The equilibrium moisture content (EMC) of five fuel types from the field site was investigated in a laboratory study. An existing function describing EMC as a function of temperature and relative humidity was evaluated and found to be very accurate for these fuels. Two FFM predictive models incorporating this function were evaluated on the field data and the laboratory results were shown to be applicable to the estimation of FFM in the field. One model gave very accurate predictions of FFM below fibre saturation point, but its accuracy was reduced when screen level conditions were used instead of those measured at fuel level. A recent process-based model that accounts for rainfall showed promise for predicting when fuel is < 25 % FFM. Systematic problems with the radiation budget of this model reduced the accuracy of predictions and further refinement is required. Live fine fuel moisture content (LFMC) of common heathland shrubs and sedge was investigated over two years and found to be both seasonal and influenced by phenology. LFMC minima occurred in late winter and spring (August to October), and maxima were in summer (December to February) when new growth was recorded. The dominant near-surface fuel in mature heath was sedge. It was found to have little seasonal variation in its??? percentage dead but the percentage dead maxima occured at the same time as the LFMC minima of shrubs and sedge in both years. Simple instantaneous models for duff moisture content in woodland and heathland and LFMC and the percentage dead sedge in heathland were developed. The information gained by this study will form the basis for future development of fuel moisture models for prescribed burning guidelines and fire spread models specific to the vegetation communities of the Sydney Basin.