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Reliable AMS ages for Mayan Caches at Copán, Honduras based on spondylus sp. marine shells
No full textCopán, located in western Honduras, is one of the most well-known of all ancient Mayan cities.
Over a century of intensive archaeological research has revealed the development of Copán from
its origins as a small agricultural village, to a major city state, followed by its decline or ‘collapse’
after AD 800. Copán’s chronology relies heavily on changes in ceramics dated by association with
hieroglyphic dates on monuments. There are surprisingly few radiocarbon dates available for a site
with such a long-term history of study and researchers have expressed a general reluctance to use
radiocarbon dating (mainly on charcoal) at Copán because radiocarbon ages are often too old
compared to associated hieroglyphic dates. Dating marine shell offers an alternative approach for
radiocarbon-based chronology building at Copán.
Spondylus sp. or spiny oyster shell is found in offering caches throughout the Copán valley. Caches
are commonly associated with the dedication of buildings, altars and stelae. We have dated cached
Spondylus sp. shells and compared their ages with calendrical dates derived from Maya hieroglyphs
to obtain new information about Classic Maya caching behaviours and the chronology of contact
with exchange partners in coastal areas from where the shell was sourced. A total of 17 Spondylus
sp. shells collected from 9 independently dated contexts were analysed for 14C with AMS to high
precision (0.30-0.35%) using the facilities at ANSTO and Waikato. Most of our AMS dates agreed
well with structural/hieroglyphic dates indicating that Spondylus sp. can be reliably used for dating
contexts. The results also showed there was very little time between death of the shellfish and
placement within caches suggesting that shells may have been acquired for specific
caching/dedication events rather than stored for long periods
Lower Hunter particle characterisation study 2nd progress report (Winter).
Get PDFThe Lower Hunter Particle Characterisation Study was commissioned by the NSW Environment Protection Authority in 2013 to investigate the composition and major sources of particle pollution in the Lower Hunter. The study was conducted by scientists from the former Office of Environment and Heritage (OEH), CSIRO and the Australian Nuclear Science and Technology Organisation (ANSTO), with oversight from the NSW Ministry of Health, and completed in 2016. Focusing on very small particles, invisible to the human eye, which can be inhaled and can pass through the throat and nose and into the lungs, the study aimed to determine the composition and major sources of fine particles (PM2.5) and coarse particles (PM2.5-10). Fine particles were monitored at four sites, including two sites representative of regional population exposures (Newcastle, Beresfield) and two sites near the Port of Newcastle (Mayfield and Stockton). Coarse particles were monitored at Mayfield and Stockton, the two sites near the Port of Newcastle
Lower Hunter particle characterisation study - chemical speciation and positive matrix factorisation factor concentration data set
No full textThe Lower Hunter Particle Characterisation Study was commissioned by the NSW Environment Protection Authority in 2013 to investigate the composition and major sources of particle pollution in the Lower Hunter. The study was conducted by scientists from the former Office of Environment and Heritage (OEH), CSIRO and the Australian Nuclear Science and Technology Organisation (ANSTO), with oversight from the NSW Ministry of Health, and completed in 2016. Focusing on very small particles, invisible to the human eye, which can be inhaled and can pass through the throat and nose and into the lungs, the study aimed to determine the composition and major sources of fine particles (PM2.5) and coarse particles (PM2.5-10). Fine particles were monitored at four sites, including two sites representative of regional population exposures (Newcastle, Beresfield) and two sites near the Port of Newcastle (Mayfield and Stockton). Coarse particles were monitored at Mayfield and Stockton, the two sites near the Port of Newcastle
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
No full textBushfires 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
Geological evidence for the destruction of Shinmachi, Hawaii, by the 1946 Aleutian and 1960 Chile Tsunamis?
No full textAround 1900, Japanese workers brought to Big Island, Hawaii, to work on the sugar plantations, established the Shinmachi (`New Town') community on low-lying land on Hilo's waterfront. Although Shinmachi was obliterated by the 1946 Aleutian tsunami, it was rebuilt, only to be totally destroyed again by the 1960 Chile tsunami. Shinmachi was never rebuilt and the site is now part of the Wailoa State Park. Short cores were collected throughout the park in an attempt to recover the geological evidence of these two tsunamis. Two anomalous layers, a lower sand (Unit 1) and an upper fining upward fine sand to silt (Unit 2) intercalated within soil and peat and exhibiting sharp lower and upper contacts, were recorded at only a few locations, probably reflecting, at least partly, the effect of anthropogenic disturbance and a limited amount of accommodation space on recent Holocene lava flows. One core was analysed by ITRAX core scanner equipped with a magnetic susceptibility (MS) meter. Unit 1 exhibits high MS associated with high Fe, Mn and Rb counts, but low Si and K counts, reflecting the volcanic composition of the material, and probably an older flooding event from the river. Unit 2 on the other hand is characterised by a different suite of elements, including Si, K, Ti, Mn, Fe, Ca, Sr, Zr and As. These most likely represent the mineralogical and chemical composition of shallow marine sediments from Hilo Bay and/or brackish sediments from Wailoa River estuary. High concentrations of As in particular have previously been reported in sediments from Hilo Bay and Wailoa River estuary and attributed to the release of arsenic trioxide by a canec manufacturing plant between 1932-1963. In this study, As was absent below Unit 2, and can thus be used as chronological control. Unit 2 therefore most likely represents the 1946 tsunami deposit. There was no clear evidence for the 1960 tsunami, probably reflecting the limited amount of accommodation space in the area
SHCal20 Southern Hemisphere calibration, 0–55,000 Years CAL BP
Get PDFEarly researchers of radiocarbon levels in Southern Hemisphere tree rings identified a variable North-South hemispheric offset, necessitating construction of a separate radiocarbon calibration curve for the South. We present here SHCal20, a revised calibration curve from 0–55,000 cal BP, based upon SHCal13 and fortified by the addition of 14 new tree-ring data sets in the 2140–0, 3520–3453, 3608–3590 and 13,140–11,375 cal BP time intervals. We detail the statistical approaches used for curve construction and present recommendations for the use of the Northern Hemisphere curve (IntCal20), the Southern Hemisphere curve (SHCal20) and suggest where application of an equal mixture of the curves might be more appropriate. Using our Bayesian spline with errors-in-variables methodology, and based upon a comparison of Southern Hemisphere tree-ring data compared with contemporaneous Northern Hemisphere data, we estimate the mean Southern Hemisphere offset to be 36 ± 27 14C yrs older. © 2020 by the Arizona Board of Regents on behalf of the University of Arizona. This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited
Radioactive and stable paleoatmospheric methane isotopes across the last deglaciation and early holocene from Taylor Glacier, Antarctica
No full textMethane (CH4) is an important greenhouse gas with both natural and anthropogenic sources. Understanding how the natural CH4 budget has changed in response to changing climate in the past can provide insights on the sensitivity of the natural CH4 emissions to the current anthropogenic warming. Both radioactive and stable CH4 isotopes (Delta14C-CH4, delta13C-CH4, and deltaD-CH4) from ice cores in Greenland and Antarctica have been used to constrain the past CH4 budget. Among the CH4 isotopes, 14CH4 is unique in its ability to unambiguously distinguish between "old" CH4 sources (e.g. marine clathrate, geologic sources, old permafrost) and "modern" CH4 sources (e.g. tropical and boreal wetlands). During the 2013-2014 and 2014-2015 field seasons at Taylor Glacier, Antarctica, we have successfully extracted 12 large volume ice samples across the Last Deglaciation to early Holocene (20ka-8ka BP). All samples have been successfully measured for CH4 mole fraction ([CH4]), Delta14C-14CH4, delta13C-CH4, and deltaD-CH4. The [CH4], delta13C-CH4, and deltaD-CH4 measurements in our samples are consistent with existing delta13C-CH4, and deltaD-CH4 datasets from other deep cores, confirming the integrity of CH4 in Taylor Glacier ice. Preliminary 14CH4 results across the Oldest Dryas - Bølling (OD-BO) CH4 transition suggest that the 150 ppb [CH4] increase during the transition was caused by increased wetland emissions. Early Holocene and Last Glacial Maximum (LGM) 14C results are still undergoing corrections for in-situ cosmogenic 14C based on 14CO measurements in the same samples. We will present the corrected 14CH4 results from these samples and our preliminary interpretations with regard to the strength of old CH4 sources during the LGM and early Holocene. © 2016 American Geophysical UnionTuesday, 13 December 2016
08:00 - 12:20
Moscone South - Poster Hall PP21A Abrupt Climate Change: Causes, Mechanisms, and Consequences IV Poster
Low dose gamma irradiation does not affect the quality or total ascorbic acid concentration of “sweetheart” passionfruit (passiflora edulis)
Get PDFPassionfruit (Passiflora edulis, Sims, cultivar “Sweetheart”) were subject to gamma irradiation at levels suitable for phytosanitary purposes (0, 150, 400 and 1000 Gy) then stored at 8 °C and assessed for fruit quality and total ascorbic acid concentration after one and fourteen days. Irradiation at any dose (≤1000 Gy) did not affect passionfruit quality (overall fruit quality, colour, firmness, fruit shrivel, stem condition, weight loss, total soluble solids level (TSS), titratable acidity (TA) level, TSS/TA ratio, juice pH and rot development), nor the total ascorbic acid concentration. The length of time in storage affected some fruit quality parameters and total ascorbic acid concentration, with longer storage periods resulting in lower quality fruit and lower total ascorbic acid concentration, irrespective of irradiation. There was no interaction between irradiation treatment and storage time, indicating that irradiation did not influence the effect of storage on passionfruit quality. The results showed that the application of 150, 400 and 1000 Gy gamma irradiation to “Sweetheart” purple passionfruit did not produce any deleterious effects on fruit quality or total ascorbic acid concentration during cold storage, thus supporting the use of low dose irradiation as a phytosanitary treatment against quarantine pests in purple passionfruit. © 2015 MDPI.Open access retrieved from: https://www.mdpi.com/2304-8158/4/3/37
Variation in bird’s originating nitrogen availability limits High Arctic tundra development over last 2000 year (Hornsund, Svalbard)
Get PDFArctic and subarctic regions play important roles in the global carbon balance. However, nitrogen (N) defi-ciency is a major constraint for organic carbon sequestration in the High Arctic. Hence, the identification of therelative contributions from different N-sources is critical for understanding the constraints that limit tundra growth.The stable nitrogen composition of the three main N-sources and numerous plants were analyzed in tentundra types (including those influenced by seabirds) in the Fuglebekken catchment (Hornsund, Svalbard, 77◦N15◦E). The percentage of the total tundra N-pool provided by seabirds’ feces (from planktivorous coloniallybreeding little auks Alle alle), ranged from 0–21% in Patterned-ground tundra to 100% in Ornithocoprophiloustundra. The total N-pool utilized by tundra plants in the studied catchment originated from birds (36%),atmospheric deposition (38%), and N2-fixation (26%). The results clearly show that N-pool in the tundra issignificantly supplemented by nesting seabirds. Thus, if they experienced climate change induced substantialnegative environmental pressure, it would adversely influence the tundra N-budget (Skrzypek et al. 2015).The growth rates and the sediment thickness (<15cm) in different tundra types varied considerably but thetundra age was similar in the whole area, <450 cal BP. The only exception was Ornithocoprophilous bird-N richtundra with very diverse ages ranging from 235 to 2300 cal BP and thickness up to 110 cm. The growth rates forthis tundra (62 cm core, 18 AMS 14C dates) were high (1.5-3.0 mm/yr) between 1568 and 1804 AD and thensubstantially declined for the period between 1804 and 1929 AD (0.2 mm/yr). These findings deliver an additionalargument, that the organic matter accumulation is driven not only directly by climatic conditions but also by birds’contribution to the tundra N-pool. © 2016 Author(s
Time history of a human kidney stone determined by bomb-pulse dating
No full textAn in vivo grown human kidney stone was dated using the atmospheric bomb pulse. The growth period was found to be 17.6 yr for a sample size of 6 mm across. The step dissolution method was used, as one of several possibilities, to produce depositional subsamples. A noticeable dead carbon presence is detected in the modern industrialized diet, and as a consequence in human metabolites. The importance for correction when applying bomb-pulse dating is noted. © 2016 by the Arizona Board of Regents on behalf of the University of Arizon