Browsing by Author "Fallon, SJ"
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- ItemA 1,500 year south Australian rainfall record based on speleothem hydrological proxies(AMOS National Conference, 2013-02-11) McDonald, J; Drysdale, RN; Hua, Q; Hodge, E; Treble, PC; Greig, A; Fallon, SJ; Lee, S; Hellstrom, JCCave drip water studies at Wombeyan Caves (34°19’S, 149°59’E) demonstrated a marked hydrochemical response to wet/dry phases (McDonald Et al. 2004; 2007). Geochemical Variations in three 20th Century coeval active Speleothems were able to be linked to the instrumental record. Subsequently geochemical relationships were investigated in a long record speleothem(WM7) which grew deeper within the same cave system. Obtaining a robust chronology proved to be challenging, due to the young age of the speleothem and very low uranium concentrations (~10 ppb) the use of U‚Aeseries disequilibrium dating was ineffective to produce a robust chronology. Chronology for WM7 was based on a dense sequence of DCF corrected ages using three different age-‐depth models: Clam (Classical method), and Bacon and OxCal (Bayesian statistical approach) (Hua et al. 2012).The new chronology indicated that WM7 began growth around 4400 cal BP(171 mm). However, since sampling from 0-‐50mm was most intensive, the model is based on this part of the stalagmite and indicates that the top 50 mm of WM7 grew during the past 1360 and 1740 years. An aridity index based on Sr,P, Y, La, and Ba shows that over the last 1,500 years several sustained episodes of wet/arid and otherwise variable phases have occurred. Two sustained wet phases ~ 700-‐880 AD and ~ 900-‐ 1250 AD were followed by ~ 400 years of variable wet/dry conditions, although from ~1300 to 1600 AD a drying trend is indicated, but punctuated by several wetter episodes. The last 200 years indicate sustained drying phases. The OE￥13C record is anomalous from ~ 1880 to present and attributed to the stalagmite’s recording of increasing contribution of fossil fuel to CO2 concentrations. Within the longer-‐time scale oscillations, higher resolution (~ 2-‐5 years) variability is evident, replicating the trend shown by modern annually resolved stalagmites at this site.
- Item15th International Conference on Accelerator Mass Spectrometry(Australian Nuclear Science and Technology Organisation, 2021-11-15) Bertuch, F; Child, DP; Fink, D; Fülöp, RH; Hotchkis, MAC; Hua, Q; Jacobsen, GE; Jenkinson, A; Levchenko, VA; Simon, KJ; Smith, AM; Wilcken, KM; Williams, AA; Williams, ML; Yang, B; Fallon, SJ; Wallner, TOn behalf of the AMS-15 Organising committee, we would like to thank you for attending the 15th International Conference on Accelerator Mass Spectrometry. Held as an online event for the first time, the 2021 conference attracted over 300 attendees with presentations delivered by colleagues and professionals from around the globe.Applications of AMS to the world’s most pressing problems/questions: A-1 : Earth’s dynamic climate palaeoclimate studies, human impacts on climate, data for climate modelling. A-2 : Water resource sustainability groundwater dating, hydrology, water quality and management A-3 : Living landscapes soil production, carbon storage, erosion, sediment transport, geomorphology. A-4 : Catastrophic natural events volcanoes, cyclones, earthquakes, tsunamis, space weather, mass extinctions. A-5 : Advancing human health metabolic and bio-kinetic studies, bomb-pulse dating, diagnostics and bio-tracing. A-6 : Challenges of the nuclear age nuclear safeguards, nuclear forensics, nuclear waste management, nuclear site monitoring, impacts of nuclear accidents. A-7 :Understanding the human story archaeology, human evolution and migration, history, art and cultural heritage A-8 : Understanding the cosmos fundamental physics, nuclear astrophysics, nuclear physics AMS Research and Development: T-1 : Novel AMS systems, components and techniques T-2 : Suppression of isobars and other interferences T-3 : Ion sourcery T-4 : New AMS isotopes T-5 : Advances in sample preparation T-6 : Data quality and management T-7 : Facility Reports (Poster Presentation only)
- ItemThe effects of diet and beauty products on the uptake and storage of 14C in hair and nails: ramifications for the application of bomb pulse dating to forensic anthropological casework(Elsevier BV, 2023-08) Johnstone-Belford, EC.; Jacobsen, GE; Fallon, SJ; Dipnall, JF; Blau, S.Radiocarbon dating is a useful tool in the examination of unknown human remains. Recent studies have shown that the analysis of hair and nail samples can provide a highly accurate estimation of the year of death (YOD). However, little research has examined factors that may influence the uptake and storage of 14C in these tissues, such as diet, or the use of beauty products. This study measured the level of 14C in human hair and nail samples collected from living individuals to determine whether diet, and the use of hair dye or nail polish, has a significant impact on the estimation of YOD. The results of this study showed that diet did not appear to impact the radiocarbon content in human hair and nail, and thus should not be considered a limitation when analysing samples obtained from unidentified human remains. The use of nail polish, and in the majority of cases, hair dye, did not significantly impact the 14C concentration in nails and hair. While the results of this study are preliminary, they suggest that in most cases, both hair and nail can be successfully analysed using radiocarbon dating to estimate an individual’s YOD. However, best practice should involve the analysis of multiple tissue types, to minimise any error that may be introduced as a result of the decedent’s use of beauty products. © Crown Copyright 2023, Published by Elsevier B.V
- ItemIODP Expedition 325 to the Great Barrier Reef: unlocking the history of reef growth and demise since the Last Glacial Maximum(Australian Geosciences Council, 2012-08-05) Webster, JM; Braga, JC; Humblet, M; Potts, DC; Iryu, Y; Hinestrosa, G; Bourillot, R; Seard, C; Camoin, G; Yokayama, Y; Thomas, AL; Thompson, B; Esat, TM; Fallon, SJ; Dutton, APredicting how the Great Barrier Reef (GBR) will respond to future global climate changes and over what time frame is crucial. Fossil reefs record critical data on geomorphic and ecological consequences of both long-term and abrupt centennial-millennial scale environmental changes. The Integrated Ocean Drilling Program (IODP) Exp. 325 investigated a succession of submerged fossil reefs on the shelf edge of the GBR to establish the course of sea-level change, define sea-surface temperature variations but also analyse the impact of these environmental changes on reef growth since the Last Glacial Maximum (LGM). Thirty-four boreholes were cored from 17 sites along four transects at three locations (Hydrographers Passage, Noggin Pass and Ribbon Reef) in water depths between 42 to 167 m. These cores record responses of the GBR to past environmental stresses similar to current scenarios of future climate change (i.e. changing sea-levels, SST’s, water quality). Initial lithologic, biologic and chronologic data document an active coral reef system that grew, drowned and backstepped up-slope as sea level rose since the LGM. We present an overview of the main Exp. 325 results, including a synthesis of the dating, paleoclimate and reef response team’s findings, in the context of the available site survey data (bathymetry, seismic, seabed imagery). Finally, we discuss the broader implications of these data for understanding how the geometry, composition and development of the GBR responded to repeated and major environmental disturbances since the LGM.
- ItemMorphology and evolution of drowned carbonate terraces during the last two interglacial cycles, off Hilo, NE Hawaii(Elsevier, 2016-01-01) Puga-Bernabéu, Á; Webster, JM; Braga, JC; Clague, DA; Dutton, A; Eggins, SM; Fallon, SJ; Jacobsen, GE; Paduan, JB; Potts, DCThe eastern side of Hawaii Island is a rapidly subsiding margin dominated by drowned carbonate platforms. We present detailed bathymetric and backscatter data, remotely operated vehicle and submersible observations, sedimentological and 14C accelerator mass spectrometry and U/Th age data from seven submerged terraces (H7, H2a–d, H1a–b) in water depths between 1100 and 25 m off Hilo, north-eastern Hawaii. The main carbonate deposits on these terraces are coral deposits, rhodolith beds, coralline algal mounds, crusts, pavements and tabular sheets. We identified five previously described sedimentary shallow- to deep-water facies and one new facies type that are consistent with reef drowning on a rapidly subsiding margin. We used palaeobathymetric data derived from the sedimentary facies, age versus depth relationships, and published sea-level curves, to estimate a uniform long-term subsidence rate of 2.80 ± 0.36 m/ky for the eastern side of Hawaii over the last 150 ky. Terrace H7 developed about 380 ka based on data from the western side of the island. Active coral growth on terrace H2d occurred during the Marine Isotope Stage (MIS) 6 to 5 transition, and the terrace drowned during the peak of MIS 5e when sea level rose faster than reefs could grow. Favoured by the gentle platform gradient, reefs established progressively landwards with a backstepping pattern during MIS 5e to form the terraces H2c and H2b 122 ka. Final turn-off of shallow water carbonate production on terraces H2b–d coincided with the relative sea-level rise of the interstadial MIS 5a. Bathymetry and submersible data suggest that carbonate sediments on terraces H2a and H1b were deposited over an antecedent topography of local lava deltas emplaced during rising sea levels at ca. 85 and 65 ka, while terrace H1a established on lava delta substrates of the Mauna Loa volcano ca. 11 ka. We conclude that the initiation, growth and drowning of coral-reef terraces off Hilo differ in some ways from the pattern observed in the submerged terraces in the western side of Hawaii and that the platform evolution off Hilo is more strongly influenced by emplacement of offshore lava flows. © 2015, Elsevier B.V
- ItemRadiocarbon surface ocean reservoir ages over the past 6,000 years from Porites microatolls, Christmas (Kiritimati) Island, central Pacific Ocean(Australian Geosciences Council, 2012-08-05) Fink, D; Carilli, JE; McGregor, HV; Woodroffe, CD; Zhao, JX; Fallon, SJWe present radiocarbon reservoir (ΔR) values over the past 5,000 years based on high-precision paired U-series and AMS 14C in modern and fossil Porites coral micro-atolls from Christmas Island (2N, 157W). The data set (n∼25) allows temporal reconstruction of ΔR with ∼250 year spacing. Christmas Island lies within the Equatorial Counter Current and the NINO3.4 region with a climate frequently punctuated by higher precipitation and warmer SSTs during El-Nino. Along its coastal perimeter, and throughout the internal network of tidal flats and lagoons, which in the late Holocene were flourishing reefal environments, fossil and modern microatolls abound. Microatolls are large discoid colonies with horizontal radial growth axes constrained in upwards vertical growth by spring tide low-water level. Consequently, a single microatoll can extend to ∼9 m in diameter representing an exceptional ∼300 years of continuous growth. Sr/Ca and δ18O in modern microatolls faithfully replicate instrumental climate records (SSTs, rainfall). Results from numerous fossil cores (1500–5500 years BP) shows distinct variability in ENSO variance both in frequency and amplitude domains compared to modern microatolls. These fossil populations are used to generate a temporal pattern of ΔR variability. Strict criteria were followed with respect to secondary calcite (via quantitative XRD), unaltered microstructure (via thin sections) and ensuring splits of identical coral chips for dual U-series and AMS 14C. Preliminary results show a ΔR decrease at about 2000 BP. Further analyses of correlations of ΔR deviations from the long term average with changes in regional ocean surface currents and in paleo-ENSO variance are in progress.
- ItemResolving the holocene alluvial record in southeastern Australia using luminescence and radiocarbon techniques.(Wiley-Blackwell, 2010-10) Cheetham, MD; Keene, AF; Erskine, WD; Bush, RT; Fitzsimmons, KE; Jacobsen, GE; Fallon, SJA previous assessment of radiocarbon (14C) dates from alluvial units in southeastern Australia revealed a gap in the geochronological record that coincides with the Holocene climatic optimum. This gap in the alluvial record can be further refined using optically stimulated luminescence (OSL). The chronology of Holocene river terraces on Widden Brook, a sandy alluvial stream in southeastern Australia, was established using 14C and OSL techniques. Combined use of these independent techniques allows for a more rigorous assessment of the alluvial record. The robust chronology, consisting of 38 14C and 11 OSL samples, permitted identification of significant depositional variation within the catchment, resulting from localised geomorphic processes. The three terrace sequences identified yielded distinct chronologies, suggesting alluvial deposition at different times. The sequences exhibited a continuous chronology, which indicated continuous deposition throughout the Holocene. The chronology of terrace sequences within this catchment suggests that terrace formation can be attributed to localised geomorphic processes rather than climatic forcing. © 2010, Wiley-Blackwell.
- ItemRobust chronological reconstruction for young speleothems using radiocarbon(Elsevier Science Ltd, 2012-12-01) Hua, Q; McDonald, J; Redwood, D; Drysdale, RN; Lee, S; Fallon, SJ; Hellstrom, JCWe have studied two young speleothems, SC4 from Smiths Cave (Christmas Island, eastern Indian Ocean) and WM7 from Wollondilly Cave (Wombeyan caves, SE Australia). Attempts to date these speleothems by the Th/U method have proved unsuccessful with some age reversals for SC4 due to multiple sources of non-authigenic Th. This method has also resulted in imprecise ages for WM7 because of low U concentrations (<10 ppb) and consequently very low levels of authigenic Th-230 relative even to the very low levels of detrital Th-230 present. Here, we present an alternative method for reliable dating of these young speleothems using radiocarbon. Approximately 100 carbonate samples from SC4 and WM7 were analysed for C-14 by accelerator mass spectrometry (AMS). The AMS results indicate that bomb C-14 was evident in the youngest parts of both stalagmites. Two different approaches were used to estimate dead carbon fraction (DCF) values for these stalagmites for the pre-bomb period. For SC4, the DCF values were estimated based on the timing of C-14 dates for that period determined by high-resolution delta O-18 recorded in the speleothem, and the timing of the onset of bomb C-14. For WM7, a "maximum" range of pre-bomb DCF was determined. Chronologies of these speleothems were built based on a dense sequence of DCF-corrected ages using three different age-depth models: Clam (Classical method), and Bacon and OxCal (Bayesian statistical approach). Good agreement between these age-depth models were observed indicating that the top 170 mm of SC4 and the top 50 mm of WM7 grew during the past 550-750 years and 1360-1740 years, respectively. © 2012, Elsevier Ltd.
- ItemRobust chronological reconstruction for your speleothems using radiocarbon(18th INQUA Congress, 2011-07-21) Hua, Q; McDonald, J; Redwood, D; Drysdale, RN; Lee, S; Fallon, SJ; Hellstrom, JCU/Th dating method is usually employed to build precise and reliable chronologies for speleothems. However, for some speleothems U-series dates may not be useful. We have studied two young speleothems, SC4 from Smiths Cave (Christmas Island, eastern Indian Ocean and WM7 from Wollondilly Cave (Wombeyan caves, SE Australia), with the aim to get a better understanding of past climate and rainfall variability beyond the instrumental records. Attempts to date SC4 by the U/Th method have proved unsuccessful with some age reversals due to multiple sources of non-authigenic Th. In addition, a sample close to the base of speleothem WM7 dated by U-series resulted in an imprecise age of ~4000 ± 500 cal BP (2?), which is due to the fact WM7 has low uranium concentrations (<10 ppb) and consequently contains very low levels of authigenic 230Th for a good U/Th age determination. In this paper, we investigate the possibility of using radiocarbon for the reconstruction of reliable chronologies for these young speleothems. Approximately 100 carbonate samples from the two stalagmites were analysed for 14C using the AMS facilities at ANSTO and ANU. The AMS results indicated that bomb 14C was evident in the youngest parts of both stalagmites. Dead carbon fraction (DCF) values for these stalagmites for the pre-bomb period were estimated based on the timing of 14C dates for that period determined by high-resolution stable isotopes recorded in the speleothems (?18O for SC4 and ?13C for WM7), and the timing of the onset of bomb 14C. Chronologies of these speleothems were built based on a dense sequence of AMS dates using 3 different age-depth models, OxCal and Bacon (Bayesian statistical approach) and Clam (non-Bayesian statistical model). The result of our radiocarbon-based chronologies and their reliability will be discussed for different DCF values including the mean DCF for the pre-bomb period and for different age-depth models. Copyright (c) 2011 INQUA 18