scholarly journals Preliminary Results for the Extraction and Measurement of Cosmogenic in Situ 14C from Quartz

Radiocarbon ◽  
2004 ◽  
Vol 46 (1) ◽  
pp. 201-206 ◽  
Author(s):  
P Naysmith ◽  
G T Cook ◽  
W M Phillips ◽  
N A Lifton ◽  
R Anderson
Keyword(s):  
Vacuum System ◽  
Quartz Sample ◽  
Erosion Rates ◽  
The Past ◽  
Cosmogenic Nuclide ◽  
Lithium Metaborate ◽  
University Of Arizona ◽  
Efficient Extraction ◽  
The University

Radiocarbon is produced within minerals at the earth's surface (in situ production) by a number of spallation reactions. Its relatively short half-life of 5730 yr provides us with a unique cosmogenic nuclide tool for the measurement of rapid erosion rates (>10−3 cm yr−1) and events occurring over the past 25 kyr. At SUERC, we have designed and built a vacuum system to extract 14C from quartz which is based on a system developed at the University of Arizona. This system uses resistance heating of samples to a temperature of approximately 1100° in the presence of lithium metaborate (LiBO2) to dissolve the quartz and liberate any carbon present. During extraction, the carbon is oxidized to CO2 in an O2 atmosphere so that it may be collected cryogenically. The CO2 is subsequently purified and converted to graphite for accelerator mass spectrometry (AMS) measurement. One of the biggest problems in measuring in situ 14C is establishing a low and reproducible system blank and efficient extraction of the in situ 14C component. Here, we present initial data for 14C-free CO2, derived from geological carbonate and added to the vacuum system to determine the system blank. Shielded quartz samples (which should be 14C free) and a surface quartz sample routinely analyzed at the University of Arizona were also analyzed at SUERC, and the data compared with values derived from the University of Arizona system.

scholarly journals Update on the Performance of the SUERC In Situ Cosmogenic 14C Extraction Line

Radiocarbon ◽  
2010 ◽  
Vol 52 (3) ◽  
pp. 1288-1294 ◽  
Author(s):  
R H Fülöp ◽  
P Naysmith ◽  
G T Cook ◽  
D Fabel ◽  
S Xu ◽  
...  
Keyword(s):  
Extraction System ◽  
Quartz Sample ◽  
Gas Cleaning ◽  
Preliminary Results ◽  
University Of Arizona ◽  
Average System ◽  
The University ◽  
Combustion Technique ◽  
Continuous Running

In this paper, we describe improvements to the in situ cosmogenic radiocarbon extraction system at SUERC made since 2004, highlighting the factors that potentially control the reduction of analytical variability. We also present new results on system blanks and of measurements of in situ14C in shielded quartz and a surface quartz sample used at the University of Arizona as an in situ14C standard (PP-4). The SUERC in situ14C extraction system was built in 2001 and is based on a combustion technique following the design of the extraction system at the University of Arizona. Our preliminary results suggest that the continuous running of the extraction system and the monitoring of gas collecting time and of the temperature of the cryogenic traps used in the gas cleaning steps are key to maintaining low and stable system blanks. Our latest average system blank is 2.02 ± 0.23 x 10514C atoms. This is consistent with those recently published by the University of Arizona and ETH in situ14C labs. Measurements of in situ14C concentrations in sample PP-4 yield an average of 3.82 ± 0.23 x 105 atoms g–1 quartz, again consistent with published values.

scholarly journals Denudation rates derived from spatially-averaged cosmogenic nuclide analysis in Nelson/Tasman catchments, South Island, New Zealand

2021 ◽  
Author(s):  
◽  
Abby Jade Burdis
Keyword(s):  
New Zealand ◽  
Dynamic Environment ◽  
Low Frequency ◽  
Short Term ◽  
Erosion Rates ◽  
Cosmogenic Nuclide ◽  
Denudation Rates ◽  
Conventional Methods

<p>New Zealand’s tectonically and climatically dynamic environment generates erosion rates that outstrip global averages by up to ten times in some locations. In order to assess recent changes in erosion rate, and also to predict future erosion dynamics, it is important to quantify long-term, background erosion. Current research on erosion in New Zealand predominantly covers short-term (100 yrs) erosion dynamics and Myr dynamics from thermochronological proxy data. Without competent medium-term denudation data for New Zealand, it is uncertain which variables (climate, anthropogenic disturbance of the landscape, tectonic uplift, lithological, or geomorphic characteristics) exert the dominant control on denudation in New Zealand. Spatially-averaged cosmogenic nuclide analysis can effectively offer this information by providing averaged rates of denudation on millennial timescales without the biases and limitations of short-term erosion methods.  Basin-averaged denudation rates were obtained in the Nelson/Tasman region, New Zealand, from analysis of concentrations of meteoric ¹⁰Be in silt and in-situ produced ¹⁰Be in quartz. The measured denudation rates integrate over ~2750 yrs (in-situ) and ~1200 yrs (meteoric). Not only do the ¹⁰Be records produce erosion rates that are remarkably consistent with each other, but they are also independent of topographic metrics. Denudation rates range from ~112 – 298 t km⁻² yr⁻¹, with the exception of one basin which is eroding at 600 - 800 t km⁻² yr⁻¹. The homogeneity of rates and absence of a significant correlation with geomorphic or lithological characteristics could indicate that the Nelson/Tasman landscape is in (or approaching) a topographic steady state.  Millennial term (¹⁰Be-derived) denudation rates are more rapid than those inferred from other conventional methods in the same region (~50 – 200 t km⁻² yr⁻¹). This is likely the result of the significant contribution of low frequency, high magnitude erosive events to overall erosion of the region. Both in-situ and meteoric ¹⁰Be analyses have the potential to provide competent millennial term estimates of natural background rates of erosion. This will allow for the assessment of geomorphic-scale impacts such as topography, tectonics, climate, and lithology on rates of denudation for the country where many conventional methods do not. Cosmogenic nuclides offer the ability to understand the response of the landscape to these factors in order to make confident erosion predictions for the future.</p>

Filtering the Past, Building the Future: A Conference on Archaeology, Tradition, and Politics in the Middle East

2004 ◽  
Vol 38 (2) ◽  
pp. 196-200
Author(s):  
Bradley J. Parker
Keyword(s):  
Middle East ◽  
The United States ◽  
United States Department ◽  
Cultural Groups ◽  
University Of Utah ◽  
Archaeological Data ◽  
The Past ◽  
University Of Arizona ◽  
The Future ◽  
The University

On April 23-24, 2004 the conference “Filtering the Past, Building the Future: Archaeology, Tradition and Politics in the Middle East,” was held in the Tanner Humanities Center at the University of Utah. Funded by a grant from the United States Department of Education with supplemental funds provided by various contributors at the University of Utah, this conference was meant to act as a forum for participants to present and discuss innovative means of understanding the uses of the past and of archaeology in politicized cultural discourse in the Middle East. The conference organizers hold the view that multiple, competing versions of the past are mobilized in service of varying agendas both within and between cultural groups. Participants were invited to discuss theories, explore methods, or present case studies that illustrate the manipulation of archaeological data and practice to promote political goals in the Middle East, and within world communities that interact with and respond to each other on topics that concern the Middle East. The papers presented at this conference are currently being edited and the resulting collection will be submitted to the University of Arizona press in the coming months.

scholarly journals δ13C Variations in C3 Plants Over the Past 50,000 Years

Radiocarbon ◽  
1992 ◽  
Vol 34 (3) ◽  
pp. 783-791 ◽  
Author(s):  
S. W. Leavitt ◽  
S. R. Danzer
Keyword(s):  
Environmental Changes ◽  
Significant Decline ◽  
C3 Plants ◽  
Data Sets ◽  
The Past ◽  
Global Environmental ◽  
University Of Arizona ◽  
Plant Data ◽  
The University ◽  
Global Environmental Changes

We examined three sets of data to determine if there are consistent changes in δ13C of C3 plants through time, under the hypothesis that environmental changes from glacial to postglacial may have caused such isotopic changes over the last 50 ka. The records of δ13C change in all types of plant data from Radiocarbon and from the University of Arizona Radiocarbon Laboratory archives both reveal significant decline of 0.8–1.0‰ in δ13C from pre- to post-10 ka BP averages. The δ13C of wood data alone from Radiocarbon shows a larger significant decline of 3.0‰, and twigs, leaves and Juniperus categories from the Arizona data individually show declines of 0.4–1.44‰. Peat and charcoal from both data sets show no significant mean δ13C differences. A highly constrained set of wood samples from the Great Lakes region spanning the last 12 ka show isotopic changes of ca. 3‰, but most of that variation apparently does not reflect global environmental changes.

scholarly journals A Simplified In Situ Cosmogenic 14C Extraction System

Radiocarbon ◽  
2010 ◽  
Vol 52 (3) ◽  
pp. 1236-1243 ◽  
Author(s):  
Jeffrey S Pigati ◽  
Nathaniel A Lifton ◽  
A J Timothy Jull ◽  
Jay Quade
Keyword(s):  
Extraction System ◽  
University Of Arizona ◽  
The University ◽  
New System ◽  
Design Construction

We describe the design, construction, and testing of a new, simplified in situ radiocarbon extraction system at the University of Arizona. Blank levels for the new system are low ((234 ± 11) x 103 atoms (1 σ; n = 7)) and stable. The precision of a given measurement depends on the concentration of 14C, but is typically <5% for concentrations of 100 x 103 atoms g–1 or more. The new system is relatively small and easy to construct, costs significantly less than the original in situ14C extraction system at Arizona, and lends itself to future automation.

The Stratigraphy of Ventana Cave, Arizona

1943 ◽  
Vol 8 (3) ◽  
pp. 218-223 ◽  
Author(s):  
Emil W. Haury
Keyword(s):  
Surface Water ◽  
General Study ◽  
Indian Reservation ◽  
The Past ◽  
South Central ◽  
University Of Arizona ◽  
State Museum ◽  
Key Sites ◽  
The University ◽  
Central Arizona

The Papago Indian Reservation, touching the Mexican border in south-central Arizona, has been the scene of anthropological work by the Department of Anthropology of the University of Arizona and the Arizona State Museum during the past four years. One branch of this general study has been archaeological, consisting of reconnaissance and of excavation in what were considered to be key sites. Beyond Gila Pueblo's limited survey in Papagueria, next to nothing was known about it. The environment is harsh and arid, and scanty surface water limits agricultural possibilities. Yet more than 5000 Papago Indians somehow manage, as they have for centuries, to make a comfortable if simple living in the area. Certainly the life there today is nothing new and it is a fair conclusion that, although inhospitable, the area should furnish a fairly rich archaeological picture. As our work proceeded it became evident that there were ruins in abundance. With few exceptions, these were small and the occupation thinly spread. Occasionally, a large site with sizable trash mounds gave promise of stratigraphy.

Tarsal Coalition: A Review of the Literature and Presentation of 13 Cases

Foot & Ankle ◽  
1988 ◽  
Vol 9 (1) ◽  
pp. 40-44 ◽  
Author(s):  
E.C. Percy ◽  
David L. Mann
Keyword(s):  
Sports Medicine ◽  
Congenital Abnormality ◽  
Health Sciences ◽  
The Other ◽  
Review Of The Literature ◽  
Tarsal Coalition ◽  
Restricted Movement ◽  
The Past ◽  
University Of Arizona ◽  
The University

Tarsal coalition refers to the condition that exists when there is absent or restricted movement between two or more of the bones of the hindfoot. The usual cause of the restricted movement is a congenital abnormality with a fibrous (syndesmosis), cartilagenous (synchondrosis), or bony (synostosis) union between the adjoining involved bones. The commonest site of these congenital anomalous attachments are reported in the literature as being located at the calcaneonavicular, the talocalcaneal, and, less commonly, the talonavicular areas. Limited movement in the hindfoot can also result from trauma, arthritis, tumor, or injury involving those joints in the foot. The congenital form may often go unrecognized until such time as a twist or sprain of the ankle or foot leads to its diagnosis. On the other hand, the condition may go unrecognized as a cause for chronic pain or discomfort in the hindfoot or ankle. In this article, a series of 13 feet in 11 patients with this condition that have been noted in the sports medicine clinic at the University of Arizona Health Sciences Center during the past 8 years is described. A detailed historical, clinical, and biomechanical account is also included.

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