ANSTO :: Browsing by Author "Shulmeister, J"

Browsing by Author "Shulmeister, J"

Now showing 1 - 20 of 35

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.
The chronology of the last deglaciation from two New Zealand valleys and some climatic implications
(18th INQUA Congress, 2011-07-21) Shulmeister, J; Fink, D; Rother, H; Thackray, GD
We present Be-10 and Al-26 chronologies from the paleo-Rakaia glacier and the Clearwater lobe of the Rangitata glacier focussing on the transition from the last glaciation maximum (LGM) to the Holocene. From the Rakaia we demonstrate that the local glacial maximum preceded the global LGM by several thousand years at c. 25 ka. Over the succeeding 12,000 years the glacier retreated only about 10 km and although undated, geomorphic evidence suggests a continued steady retreat after this time. The Clearwater lobe of the Rangitata glacier provides the most detailed LGIT record from any New Zealand glacier because it the valley was protected from significant meltwater flow during the deglaciation. Between 16.4 ka and 13.7 ka the Clearwater ice lobe retreated only 12 km producing 23 closely spaced recessional ice positions. The geomorphology and chronology are categorical in demonstrating that no significant re-advance can have occurred during this period. The inboard termination of the record occurs where the Clearwater valley drops into the main Rangitata Valley and should not be interpreted as the start of the more significant retreat. We highlight that uncertainties in isotope production rates and other elements of cosmogenic age determination (e.g. geomagnetic corrections) means that while we have millenial scale precision on ages during the LGIT, the accuracy of the ages is not as high. Nevertheless, our data clearly demonstrate that the evacuation of ice from these east coast valleys in New Zealand was remarkably slow with glaciers extending to ~60% of their LGM extents at 14 kyr (or younger). There is no evidence for either an early LGIT ice collapse or rapid retreat and consequently no late LGIT major readvance. We contrast our findings with the interpretations of chronologies coming from the Mackenzie Basin and we conclude that the records are compatible, with the chronological differences created by the morphometry of the respective ice catchments.Copyright (c) 2011 INQUA 18
Comment on Barrell et al. “Reconciling the onset of deglaciation in the Upper Rangitata valley, Southern Alps, New Zealand” (Quaternary Science Reviews 203 (2019), 141–150.)
(Elsevier, 2019-09-01) Shulmeister, J; Fink, D; Winkler, S; Thackray, GD; Borsellino, R; Hemmingsen, M; Rittenour, TM
Recently, Barrell et al. (2019) published an article that responded to our article (Shulmeister et al., 2018a) on gradual evacuation of ice from the Upper Rangitata Valley, South Island, New Zealand, during the last glaciation. They base their contrasting interpretation of substantial and rapid ice-lowering of Rangitata glacier shortly after 18 ka on a revision of our 10Be cosmogenic radionuclide (CRN) chronology and by reference to published sources (e.g. Mabin, 1980, 1987). Their interpretation relies on glacial landform features extracted from a geomorphology map of the central Southern Alps by Barrell et al. (2011). Barrell et al. (2019) highlight that rapid ice recession of the Rangitata glacier is compatible to their results from Mackenzie Basin and Rakaia Valley (Putnam et al., 2013a, b). We highlight four points in response to Barrell et al. (2019). © 2019 Elsevier Ltd.
Constraints on ice volume changes of the WAIS and Ross Ice Shelf since the LGM based on cosmogenic exposure ages in the Darwin-Hatherton glacial system of the Transantarctic Mountains
(Copernicus Publications, 2010-05-02) Fink, D; Storey, BC; Hood, D; Joy, K; Shulmeister, J
Quantitative assessment of the spatial and temporal scale of ice volume change of the West Antarctic ice sheet (WAIS) and Ross Ice Shelf since the last glacial maximum (LGM) ~20 ka is essential to accurately predict ice sheet response to current and future climate change. Although global sea level rose by approximately 120 metres since the LGM, the contribution of polar ice sheets is uncertain and the timing of any such contribution is controversial. Mackintosh et al (2007) suggest that sectors of the EAIS, similar to those studied at Framnes Mountains where the ice sheet slowly calves at coastal margins, have made marginal contributions to global sea-level rise between 13 and 7 ka. In contrast, Stone et al (2003) document continuing WAIS decay during the mid-late Holocene, raising the question of what was the response of the WAIS since LGM and into the Holocene. Terrestrial evidence is restricted to sparse coastal oasis and ice free mountains which archive limits of former ice advances. Mountain ranges flanking the Darwin-Hatherton glaciers exhibit well-defined moraines, weathering signatures, boulder rich plateaus and glacial tills, which preserve the evidence of advance and retreat of the ice sheet during previous glacial cycles. Previous studies suggest a WAIS at the LGM in this location to be at least 1,000 meters thicker than today. As part of the New Zealand Latitudinal Gradient Project along the Transantarctic, we collected samples for cosmogenic exposure dating at a) Lake Wellman area bordering the Hatherton Glacier, (b) Roadend Nunatak at the confluence of the Darwin and Hatherton glaciers and (c) Diamond Hill which is positioned at the intersection of the Ross Ice Shelf and Darwin Glacier outlet. While the technique of exposure dating is very successful in mid-latitude alpine glacier systems, it is more challenging in polar ice-sheet regions due to the prevalence of cold-based ice over-riding events and absence of outwash processes which removes glacially transported debris. Our glacial geomorphic survey from ice sheet contact edge (~850 masl) to mountain peak at 1600 masl together with a suite of 10Be and 26Al exposure ages, documents a pre-LGM ice volume at least 800 meters thicker than current ice levels which was established at least 2 million years ago. However a complex history of exposure and re-exposure of the ice free regions in this area is seen in accordance with advance and retreat of the ice sheets that feeds into the Darwin –Hatherton system. A cluster of mid-altitude boulders, located below a prominent moraine feature mapped previously as demarcating the LGM ice advance limits, have exposure ages ranging from 30 to 40 ka. Exposure ages for boulders just above the ice contact range from 1to 19 ka and allow an estimate of inheritance. Hence, we conclude that LGM ice volume was not as large as previously estimated and actually little different from what is observed today. These results raise rather serious questions about the implications of a reduced WAIS at the LGM, its effect on the development of the Ross Ice Shelf, and how the Antarctic ice sheets respond to global warming.
Constraints on ice volume changes of the West Antarctic Ice Sheet and Ross
(12th International Conference on Accelerator Mass Spectrometry (AMS-12), 2012-03-22) Fink, D; Storey, B; Joy, K; Shulmeister, J
the Last Glacial Maximum (~20 ka), marine evidence indicates that the grounding line of the West Antarctic Ice Sheet (WAIS) advanced northwards into the Ross Ice Shelf (RIS), blocking drainage of outlet glaciers through the Transantarctic Mountains (TM) resulting in significant downstream thickening of glacier profiles. The Darwin and Hatherton Glaciers in the TMs provide geological and pedological records of WAIS fluctuations that are interpreted as evidence for a LGM ice volume at least ~800 m thicker than today. Cosmogenic 10Be and 26Al exposure ages at Lake Wellman and Dubris Valley from ice-sheet contact (850 masl) to mountain peak (600 masl) show a WAIS Pleistocene ice thickness some 800 to 400 meters thicker than today. However a cluster of mid-altitude moraine boulders, previously taken to demarcate the LGM advance, have exposure ages ranging from 30 to 40 ka. This suggests that while WAIS expansion during the early Pleistocene was large, its LGM ice volume was not as large as previously estimated and little different from what is observed today (at most 50 m above current ice surface). A second site further north, Diamond Hill, lies at the confluence of the Darwin Glacier and RIS. Two transects were sampled on Diamond Hill that cover an altitude range of 1100 meters. Preliminary 10Be cosmogenic dates show a similar trend to that seen further up glacier in Lake Wellman. For the case of Diamond Hill, the WAIS was approximately 900 meters thicker than the current Rose Ice Shelf configuration at ~1.5Ma and with only minor advances in the last 10ka. As with Lake Wellman no evidence of large scale LGM advances were found. These results raise serious questions about the implications of a reduced West Antarctic ice Sheet at the LGM, and how the Antarctic ice sheets respond to global warming. Copyright (c) 2011 AMS12
Corrigendum to “Evidence for slow late-glacial ice retreat in the upper Rangitata Valley, South Island, New Zealand” [Quat. Sci. Rev. 185 (2018) 102–112]
(Elsevier, 2019-09-01) Shulmeister, J; Fink, D; Winkler, S; Thackray, GD; Borsellino, R; Hemmingsen, M; Rittenour, TM
It has been brought to our attention, following a recent publication by Barrell et al. (2019), that the elevations for 12 of 23 boulders reported in our publication, Shulmeister et al., v185, 102–112 (2018) are incorrect. For these 12 samples, the true elevations are higher and hence all exposure ages based on their respective 10Be concentration measurements require a downward correction of between 10 and 15%. This change in age does not alter our main conclusions but does have some implication for the initiation and pace of deglaciation. © 2019 Elsevier Ltd.
Cosmogenic 10Be and 26Al exposure ages of moraines in the Rakaia Valley, New Zealand and the nature of the last termination in New Zealand glacial systems
(Elsevier, 2010-09-01) Shulmeister, J; Fink, D; Hyatt, OM; Thackray, GD; Rother, H
New Zealand glaciers reached their last glacial maximum position at or before ~ 25 ka, and, as early as 23 ka, commenced a slow and continual retreat. New cosmogenic exposure ages and field mapping from the Rakaia Valley in the South Island suggest that extensive ice survived well into the latter half of the Last Glacial–Interglacial Transition (18–11 ka), with the post-15 ka period inferred to have near Holocene climate conditions based on ecological proxy data. By as late as ~ 15.5 ka, glacier termini had retreated as little as 5–10 km from glacial maximum positions. Numerous minor ice still-stand positions and oscillations are recognized, but the record specifically excludes evidence for either a major climatic amelioration at ~ 15–16 ka or a significant glacial re-advance during the Antarctic Cold Reversal (ACR) or the Younger Dryas (YD). We conclude that the currently widespread interpretation of an episodic New Zealand glacial record since the LGM is an artifact of valley-dependent retreat processes. Pro-glacial lake formation and local site conditions combined to give an apparent, but misleading, picture of glacial retreat punctuated by major, climatically driven, re-advances. © 2010, Elsevier Ltd.
A cosmogenic nuclide chronology of the last glacial transition in North-West Nelson, New Zealand—new insights in Southern Hemisphere climate forcing during the last deglaciation
(Elsevier, 2005-05-15) Shulmeister, J; Fink, D; Augustinus, PC
We present a new glacial chronology for the last glacial interglacial transition, c. 20 to 10 ka, from the Cobb Valley, NW Nelson, New Zealand, based on a suite of 10Be and 26Al cosmogenic exposure ages. This chronology describes one of the most comprehensive deglaciation sequences from a late Quaternary valley system in the Southern Hemisphere. We chronicle the decay from the last (local) glacial maximum as follows: onset of the last deglaciation that commenced no earlier than 18–19 ka, followed by numerous short-term still-stands and/or minor re-advances over the ensuing 3–4 kyr, and complete evacuation of ice by 14 ka. We find no evidence to indicate a late glacial re-advance commensurate with the Northern Hemisphere Younger Dryas chronozone. The absence of a major glacial re-advance in this valley during the latter stages of the last glacial interglacial transition (LGIT) precludes a thermal decline in excess of about 3 °C and suggests no decline. The absence of late LGIT re-advances in the mountains of North-West Nelson, while deglacial readvances occurred in the main ranges of the Southern Alps can be best explained if westerly wind forcing rather than large-scale thermal decline is the primary control on glacier fluctuations, at least during the deglaciation. These findings challenge models of global climate change predicated on synchrony of millennial-scale glacial transitions due to thermal changes between Northern and Southern Hemispheres. © 2005 Elsevier B.V.
Cosmogenic nuclide exposure age constraints on the glacial history of the Lake Wellman area, Darwin Mountains, Antarctica
(Cambridge University Press, 2010-12) Storey, BC; Fink, D; Hood, D; Joy, K; Shulmeister, J; Riger-Kusk, M; Stevens, MI
We present direct terrestrial evidence of ice volume change of the Darwin and Hatherton glaciers which channel ice from the Transantarctic Mountains into the Ross Ice Shelf. Combining glacial geomorphology with cosmogenic exposure ages from 25 erratics indicates a pre-LGM ice volume at least 600 m thicker than current Hatherton ice elevation was established at least 2.2 million years ago. In particular, five erratics spread across a drift deposit at intermediate elevations located below a prominent moraine feature mapped previously as demarcating the LGM ice advance limits, give a well-constrained single population with mean 10Be age of 37.0 ± 5.5 ka (1σ). At lower elevations of 50–100 m above the surface of Lake Wellman, a further five samples from within a younger drift deposit range in exposure age from 1 to 19 ka. Our preferred age model interpretation, which is partly dependent on the selection of a minimum or maximum age-elevation model, suggests that LGM ice volume was not as large as previously estimated and constrains LGM ice elevation to be within ± 50 m of the modern Hatherton Glacier ice surface, effectively little different from what is observed today. © 2010, Cambridge University Press
Developing an event stratigraphy for Australasian climate change
(American Geophysical Union, 2011-06-03) Shulmeister, J; Turney, CSM; Fink, D; Newnham, RM; Alloway, BV
The last glacial-interglacial transition in the Australasian region has been a focus of intense paleoclimate investigation for the past decade or so. This focus is due to the recognition of the southern midlatitudes as a key region to examine climate connections between the hemispheres during the late Pleistocene. That period, between 30,000 and 8000 years ago, was marked by extreme and rapid climatic change in the North Atlantic region. In particular, the Australasian region may be critical to examining the relative importance of atmospheric energy transfers versus deep ocean circulation effects. In February 2006, 32 members of the Australasian Integration of Ice, Marine and Terrestrial records (INTIMATE) program attended a two-day workshop at the University of Auckland, in New Zealand. ©2006. American Geophysical Union.
Diamond Hill, Darwin Glacier. A proxy for the West Antarctic ice sheet?
(Australasian Quaternary Association, 2010-07-16) Joy, K; Storey, BC; Fink, D; Shulmeister, J
In the Ross Sea embayment during the Last Glacial Maximum (LGM, 18-22ka), the grounding line of the West Antarctic Ice Sheet (WAIS) advanced northwards into the Ross Ice Shelf (RIS). This effectively dammed the drainage of the Transantarctic Mountain outlet glaciers and caused significant downstream thickening of their glacier profiles (Conway et al 1999). The Darwin / Hatherton Glacial System (79.5° S, 158° E) provides a number of sites that contain geological evidence of WAIS fluctuations. Previous geomorphic and pedological studies in the area (Bockheim et al. 1989, Denton & Hughes 2000) have used these sites to constrain the timing and magnitude of the LGM ice sheet advances. As Diamond Hill lies at the confluence of the Darwin Glacier and RIS its glacial geomorphology should reflect the thickening caused by the advancing WAIS. Insitu cosmogenic nuclide dating has being used at sites along the Darwin/Hatherton as a proxy to recreate the timing and magnitude of both WAIS and EAIS advances. By measuring the concentrations of Beryllium-10 and Aluminium-26 in quartz rich lithologies, the time since the deposition of a moraine can be calculated. Early interpretations based on cosmogenic ages from the Lake Wellman area (Fink et al 2009, Storey, et al. 2010) show up to 800 meters of thickened ice approximately 2 million years ago. Moraines previously assumed to be the limit of LGM ice expansion, date to 30-40 ka. This suggests that while early EAIS Quaternary expansion was large; ice volume at the LGM may be little changed from the present. Two transects were sampled on Diamond Hill that cover an altitude range of 1100 meters. Preliminary 10Be cosmogenic dates show a similar trend to that seen further up glacier in Lake Wellman, in the case of Diamond Hill the WAIS was approximately 900 meters thicker than the current Rose Ice Shelf configuration at ~1.5Ma and with only small advances in the last 10ka. As with Lake Wellman no evidence of large scale LGM advances were found.
Diamond Hill, Darwin Glacier. A proxy for the West Antarctic ice sheet?
(University of Canterbury, 2010-07-05) Joy, K; Storey, BC; Fink, D; Shulmeister, J
In the Ross Sea embayment during the Last Glacial Maximum (LGM, 18-22ka), the grounding line of the West Antarctic Ice Sheet (WAIS) advanced northwards into the Ross Ice Shelf (RIS). This effectively dammed the drainage of the Transantarctic Mountain outlet glaciers and caused significant downstream thickening of their glacier profiles (Conway et al 1999). The Darwin / Hatherton Glacial System (79.5° S, 158° E) provides a number of sites that contain geological evidence of WAIS fluctuations. Previous geomorphic and pedological studies in the area (Bockheim et al. 1989, Denton & Hughes 2000) have used these sites to constrain the timing and magnitude of the LGM ice sheet advances. As Diamond Hill lies at the confluence of the Darwin Glacier and RIS its glacial geomorphology should reflect the thickening caused by the advancing WAIS. Insitu cosmogenic nuclide dating has being used at sites along the Darwin/Hatherton as a proxy to recreate the timing and magnitude of both WAIS and EAIS advances. By measuring the concentrations of Beryllium-10 and Aluminium-26 in quartz rich lithologies, the time since the deposition of a moraine can be calculated. Early interpretations based on cosmogenic ages from the Lake Wellman area (Fink et al 2009, Storey, et al. 2010) show up to 800 meters of thickened ice approximately 2 million years ago. Moraines previously assumed to be the limit of LGM ice expansion, date to 30-40 ka. This suggests that while early EAIS Quaternary expansion was large; ice volume at the LGM may be little changed from the present. Two transects were sampled on Diamond Hill that cover an altitude range of 1100 meters. Preliminary 10Be cosmogenic dates show a similar trend to that seen further up glacier in Lake Wellman, in the case of Diamond Hill the WAIS was approximately 900 meters thicker than the current Rose Ice Shelf configuration at ~1.5Ma and with only small advances in the last 10ka. As with Lake Wellman no evidence of large scale LGM advances were found.
The early rise and late demise of New Zealand’s last glacial maximum
(Proceedings of the National Academy of Sciences of the United States of America, 2014-06-13) Rother, H; Fink, D; Shulmeister, J; Mifsud, C; Evans, M; Pugh, J
Recent debate on records of southern midlatitude glaciation has focused on reconstructing glacier dynamics during the last glacial termination, with different results supporting both in-phase and out-of-phase correlations with Northern Hemisphere glacial signals. A continuing major weakness in this debate is the lack of robust data, particularly from the early and maximum phase of southern midlatitude glaciation (∼30–20 ka), to verify the competing models. Here we present a suite of 58 cosmogenic exposure ages from 17 last-glacial ice limits in the Rangitata Valley of New Zealand, capturing an extensive record of glacial oscillations between 28–16 ka. The sequence shows that the local last glacial maximum in this region occurred shortly before 28 ka, followed by several successively less extensive ice readvances between 26–19 ka. The onset of Termination 1 and the ensuing glacial retreat is preserved in exceptional detail through numerous recessional moraines, indicating that ice retreat between 19–16 ka was very gradual. Extensive valley glaciers survived in the Rangitata catchment until at least 15.8 ka. These findings preclude the previously inferred rapid climate-driven ice retreat in the Southern Alps after the onset of Termination 1. Our record documents an early last glacial maximum, an overall trend of diminishing ice volume in New Zealand between 28–20 ka, and gradual deglaciation until at least 15 ka. © 2014, National Academy of Sciences of the United States of America.
Evaluating δ18O and δ13C variations within a modern Biggenden Banded snail (Figuladra bayensis) shell using radiocarbon dating: application for past climate reconstruction
(Australian Nuclear Science and Technology Organisation, 2021-11-17) Patton, NR; Shulmeister, J; Leng, MJ; Jones, M; Hua, Q; Hughes, CE
Gastropods are utilized to infer paleoclimate variability due to the preservation and incorporation of stable isotopes (δ18O and δ13C) in their aragonite shells. Analyses along the growth axis of larger gastropods have been suggested to contain high-resolution records of local seasonal climate variability and the organism’s biological life cycle. Here a Figuladra bayensis (Biggenden Banded snail) shell was collected shortly after death from Coalstoun Lakes National Park, Queensland, Australia. A total of 200 samples were collected for δ18O and δ13C analyses and an additional 8 radiocarbon dating samples were collected along the growth axis from the apex to the aperture. Results from our work indicates that the Biggenden Banded snail lived ~4.4 years, with evidence of two aestivation (dormant stage) periods during the dry, cool winters. As a result, its growth rate was episodic with the highest rates of ~90 mm/yr occurring shortly after large rain events. The δ18O and δ13C variation in the shell is closely related to total rainfall, diet and physiological changes. To our knowledge this is the highest resolution isotopic and radiocarbon dated study on a modern terrestrial snail, allowing the nuances of the stable isotope record to be more clearly interpreted and therefore used as a palaeoenvironmental proxy. © The Authors
Evidence against early nineteenth century major European induced environmental impacts by illegal settlers in the New England Tablelands, south eastern Australia.
(Pergamon-Elsevier Science Ltd, 2011-12-01) Woodward, C; Chang, J; Zawadzki, A; Shulmeister, J; Haworth, R; Collecutt, S; Jacobsen, GE
Paleoenvironmental reconstructions from Little Llangothlin Lagoon have been used to argue for early European impact on the eastern Australian landscape. In particular, these studies have argued for European arrival on the New England Tablelands at about 1800 AD, with significant impacts including the clearance of one species of Casuarina before 1820 AD and significant erosion by 1836 AD (Gale et al.. 1995: Gale and Pisanu, 2001; Gale and Haworth, 2002, 2005). We have re-cored the lagoon, dated the cores using (210)Pb and radiocarbon, and counted pollen and other proxies. Our (210)Pb results indicate that (210)Pb background was achieved stratigraphically later than the erosion event and we have three early Holocene radiocarbon ages in the erosion event interval. We conclude that the 'erosion event' predates European settlement. The (210)Pb results indicate much less erosion in response to European settlement than suggested by these earlier studies. We also find no notable decline in Casuarina in the pollen record spanning the time of initial European impact, and in fact we find very little Casuarina in the record. Instead of a Casuarina dominated vegetation we conclude that the area was dominated by open Eucalypt forest prior to European settlement. Rather than changes in the regional vegetation in the early 19th century, we attribute changes in the palynoflora spanning the 'erosion event' to changes within the lake/wetland and in particular to changes in the dominance of different species of Myriophyllum; most likely due to water depth fluctuation. This site has stood out as indicating an earlier European impact than other localities in eastern Australia, beyond the original limits of settlement near Sydney. Our findings suggest that a more traditional interpretation of this site is warranted and that no very early impact is discernable. (C) 2011 Elsevier Ltd. All rights reserved.
Evidence for expanded Middle and Late Pleistocene glacier extent in northwest Nelson, New Zealand.
(Wiley-Blackwell, 2009-12) Thackray, GD; Shulmeister, J; Fink, D
The extent of Late Quaternary glaciation in the northwest Nelson region of New Zealand has traditionally been regarded as minor, with small-scale valley glaciation in confined upland reaches. New geomorphological evidence, including moraines, kame terraces, till-mantled bedrock and outwash terraces, indicate that greatly expanded valley glaciers flowed into the lowland valley system at the mouths of the Cobb-Takaka and Anatoki drainages. The timing for this ice advance into lowland valleys is constrained by lowland landform characteristics and a single cosmogenic exposure age, suggesting Late and Middle Pleistocene ice expansion, respectively. Evidence for expanded upland ice on the Mount Arthur Tableland and adjacent areas includes trimlines, boulder trains and roche moutonées. Two cosmogenic exposure ages on upland bedrock surfaces suggest that major ice expansion occurred during MIS 3 and/or 4, while previously published exposure dating from Cobb Valley suggests large MIS 2 ice expansion as well. The inferred, markedly expanded ice left little or no clear geomorphic imprint on the Cobb–Takaka Gorge, and required temperature depression of 4–6°C with near-modern precipitation levels. © 2009, Wiley-Blackwell.
Evidence for slow late-glacial ice retreat in the upper Rangitata Valley, South Island, New Zealand
(Elsevier, 2018-04-01) Shulmeister, J; Fink, D; Winkler, S; Thackray, GD; Borsellino, R; Hemmingsen, M; Rittenour, TM
A suite of cosmogenic radionuclide ages taken from boulders on lateral and latero-terminal moraines in the Rangitata Valley, eastern South Island, New Zealand demonstrates that relatively thick ice occupied valley reaches inland of the Rangitata Gorge until c. 21 ka. Thereafter ice began to thin, and by c. 17 ka it had retreated 33 km up-valley of the Rangitata Gorge to the Butler-Brabazon Downs, a structurally created basin in the upper Rangitata Valley. Despite its magnitude, this retreat represents a minor ice volume reduction from 21 ka to 17 ka, and numerous lateral moraines preserved suggest a relatively gradual retreat over that 4 ka period. In contrast to records from adjacent valleys, there is no evidence for an ice-collapse at c. 18 ka. We argue that the Rangitata record constitutes a more direct record of glacial response to deglacial climate than other records where glacial dynamics were influenced by proglacial lake development, such as the Rakaia Valley to the North and the major valleys in the Mackenzie Basin to the south-west. Our data supports the concept of a gradual warming during the early deglaciation in the South Island New Zealand. © 2018 Elsevier Ltd.
Geochemical investigation of the South Wellesley Island wetlands: insight into wetland development during the Holocene in tropical northern Australia
(Sage, 2016-09-28) Mackenzie, LL; Heijnis, H; Gadd, PS; Moss, PT; Shulmeister, J
The South Wellesley Islands in the Gulf of Carpentaria, northern Australia, were the recent focus of a palynological investigation which found vegetation change during the Holocene was driven by coastal progradation and regional climate. Here, we present new elemental data from x-ray fluorescence core scanning which provides non-destructive, continuous and high resolution analysis from three wetlands across Bentinck Island, the largest of the South Wellesley Islands. Elemental data and grain size analyses are combined with lead-210 (210Pb) and accelerator mass spectrometry (AMS) carbon-14 (14C) dates. An open coastal environment was present 1250 cal. a BP on the south east coast of Bentinck Island, with sediment supply incorporating fluvial deposition and detrital input of titanium and iron from eroding lateritic bedrock. Prograding shorelines, dune development and river diversion formed a series of swales parallel to the coast by ~800 cal. a BP, forming the Marralda wetlands. Wetlands developed at sites on the north and west coasts ~500 and ~450 cal. a BP, respectively. Geochemical and grain size analyses indicate that wetlands formed as accreting tidal mudflats or within inter-dune swales that intercepted groundwater draining to the coastal margins. The timing of wetland initiation indicates localised late-Holocene sea level regression, stabilisation and coastal plain development in the Gulf of Carpentaria. Elemental data provide new records of wetland development across Bentinck Island, highlighting the value of a multi-proxy approach to understanding environmental change during the Holocene in tropical northern Australia. © 2020 by SAGE Publications
Glacial geomorphology and its links to ice sheet thicknesses, Diamond Hill, Transantarctic Mountains.
(GNS Science, 2009-07-03) Joy, K; Storey, BC; Fink, D; Shulmeister, J
An understanding of how the Antarctic continent has reacted to past climates is necessary to accurately predict the response of its ice sheets to current and future climate changes. The thickness and proximity of the peripheral ice to the continental margin are key to the discussion and relate directly to the volume of ice within the East and West Antarctica ice sheets and their melt water contribution to sea level rise since the LGM. The Darwin/Hatherton is an outlet glacial system that drains the East Antarctic Ice Sheet into the Ross Sea through the Transantarctic Mountains. At the confluence of the Darwin Glacier and Ross Ice Shelf, Diamond Hill a relatively ice free area, contains evidence of glacial advances at altitudes up to 850m above the current ice surface. Here both ice sheets have created landforms that will allow a reconstruction of ice thickness. Cosmogenic dating will be used to create a timeline of post-LGM glacial retreat in which the influence of cold based ice must also be evaluated. This work will contribute fundamental data to an important international debate on the scale of the glaciation in the last ice age. It will help validate ice thickness reconstructions for the ice sheets and it may give insight into the timing and nature of Antarctic contributions to global sea-levels.
Holocene ecosystem change in Little Llangothlin Lagoon, Australia: implications for the management of a Ramsar-listed wetland
(Springer Nature, 2016-01-01) Woodward, C; Shulmeister, J; Zawadzki, A; Child, DP; Barry, LA; Hotchkis, MAC
We present new chironomid and stable isotope (δ13C and δ15N) data from Little Llangothlin Lagoon, Australia that provides more detail on changes in this wetland since European settlement ca. 1840 AD. We also examine how the updated Holocene paleoecological record provides insights for management of this Ramsar-listed wetland. The current management strategy for Little Llangothlin is to restore the wetland and catchment to its natural state. This strategy is intended to protect the values that allowed it to be listed as a Ramsar wetland; i.e. its role as a drought refuge for waterbirds and to preserve or enhance threatened ecological communities. There are clear conflicts between the Ramsar listing criteria, management objectives and the management strategy in light of information provided by the palaeoecological record. In particular, restoration of terrestrial ecosystems through reforestation may jeopardise the wetlands role as a drought refuge. Some activities, such as artificial raising of the water level in 1989 are intended to restore, but actually introduced a state that did not exist prior to human settlement. We recommend a more integrated management approach that heeds the information provided by the palaeoecological record and focuses more on maintenance or enhancement of ecosystem services and biodiversity. © 2016, Springer

Browsing by Author "Shulmeister, J"

Results Per Page

Sort Options