scholarly journals ERRONEOUSLY OLD RADIOCARBON AGES FROM TERRESTRIAL POLLEN CONCENTRATES IN YELLOWSTONE LAKE, WYOMING, USA

Radiocarbon ◽  
2020 ◽  
pp. 1-22
Author(s):  
Christopher M Schiller ◽  
Cathy Whitlock ◽  
Kathryn L Elder ◽  
Nels A Iverson ◽  
Mark B Abbott
Keyword(s):  
Pollen Grains ◽  
Water Interface ◽  
Satisfactory Explanation ◽  
Yellowstone Lake ◽  
Carbon Contamination ◽  
Terrestrial Plant ◽  
Plant Remains ◽  
Sediment Records ◽  
Ams Dating ◽  
Yellowstone Caldera

ABSTRACT Accelerator mass spectrometry (AMS) dating of pollen concentrates is often used in lake sediment records where large, terrestrial plant remains are unavailable. Ages produced from chemically concentrated pollen as well as manually picked Pinaceae grains in Yellowstone Lake (Wyoming) sediments were consistently 1700–4300 cal years older than ages established by terrestrial plant remains, tephrochronology, and the age of the sediment-water interface. Previous studies have successfully utilized the same laboratory space and methods, suggesting the source of old-carbon contamination is specific to these samples. Manually picking pollen grains precludes admixture of non-pollen materials. Furthermore, no clear source of old pollen grains occurs on the deglaciated landscape, making reworking of old pollen grains unlikely. High volumes of CO2 are degassed in the Yellowstone Caldera, potentially introducing old carbon to pollen. While uptake of old CO2 through photosynthesis is minor (F14C approximately 0.99), old-carbon contamination may still take place in the water column or in surficial lake sediments. It remains unclear, however, what mechanism allows for the erroneous ages of highly refractory pollen grains while terrestrial plant remains were unaffected. In the absence of a satisfactory explanation for erroneously old radiocarbon ages from pollen concentrates, we propose steps for further study.

scholarly journals Gas Exchange Rate Measurements in Natural Systems

Radiocarbon ◽  
1980 ◽  
Vol 22 (3) ◽  
pp. 676-683 ◽  
Author(s):  
W S Broecker ◽  
T-H Peng ◽  
G Mathieu ◽  
R Hesslein ◽  
T Torgersen
Keyword(s):  
Exchange Rate ◽  
Wind Speed ◽  
Wind Tunnel ◽  
Sea Water ◽  
Water Interface ◽  
Satisfactory Explanation ◽  
Natural Systems ◽  
Air Water Interface ◽  
Gas Exchange Rate ◽  
Mean Wind Speed

Rates of CO2 exchange across the air-water interface in oceans and lakes measured to date by the L-DGO group are summarized. They range from 3 to 38 moles/m2/yr. The possible causes for this range include the differences in salinity, mean wind speed, and pH. Wind tunnel studies comparing fresh water and sea water are required before a satisfactory explanation can be found.

Accelerator-Mass Spectrometer Ages for Late-Glacial Events at Ballybetagh, Ireland

1989 ◽  
Vol 31 (3) ◽  
pp. 377-380 ◽  
Author(s):  
Les C. Cwynar ◽  
W. A. Watts
Keyword(s):  
Mass Spectrometer ◽  
Organic Material ◽  
Younger Dryas ◽  
Hard Water ◽  
Late Glacial ◽  
Water Effect ◽  
Vegetation Development ◽  
Terrestrial Plant ◽  
Plant Remains ◽  
Accelerator Mass Spectrometer

AbstractAlthough the character of late-glacial vegetation development in Ireland is well known, the dating is weak for a number of reasons. We report six accelerator-mass spectrometer (AMS) 14C dates of hand-picked organic material from Ballybetagh. Several of the dates are based on terrestrial plant remains, thus eliminating the commonly encountered problem associated with Irish sites of errors due to the hard-water effect. The two most significant indicate that (1) the Rumex-Salix zone, which represents the initial establishment of vegetation following deglaciation, began about 12,600 yr B.P. and (2) the classic Younger Dryas began at 10,600 yr B.P., somewhat younger than the traditionally accepted age of 11,000 yr B.P.

scholarly journals 14C AMS Dating of Icelandic Lake Sediments

Radiocarbon ◽  
1997 ◽  
Vol 40 (2) ◽  
pp. 865-872 ◽  
Author(s):  
Árný E. Sveinbjörnsdóttir ◽  
Jan Heinemeier ◽  
Peter Kristensen ◽  
Niels Rud ◽  
Áslaug Geirsdóttir ◽  
...  
Keyword(s):  
Sample Pretreatment ◽  
Bulk Sediment ◽  
Organic Fraction ◽  
Sediment Samples ◽  
Age Diversity ◽  
Plant Remains ◽  
Ams Dating ◽  
Lowermost Part ◽  
Reservoir Age ◽  
Depth Curve

We report an age-depth profile for the sediments of the Lake Hesrvatn, southern Iceland, based on 14C analyses of the organic fraction of bulk sediment samples, molluscs and foraminifera. Our age-depth curve is supported by the occurrence of the well-dated Vedde ash in the lowermost part of the sediments. Comparison of foraminifera dates with the age of the Vedde ash indicates a reservoir age of ca. 400 yr. The results suggest that the sediments at Hestvatn accumulated in a marine environment until ca. 8700 bp and thereafter in freshwater.Owing to the lack of terrestrial macrofossils and the low concentration of molluscs and foraminifera, we were forced to attempt to date most of the core with the organic fraction of the bulk sediment samples. We found, however, that this fraction is not homogeneous in density or 14C age. We believe that during sample pretreatment we managed to isolate a light organic fraction, which closely represents the true age of the sediment, whereas the denser fraction yields ages that are too high. This age diversity may to some extent be explained by the large drainage area of the lake, from which plant remains of different ages may have been washed into the lake.

scholarly journals Pollen Concentrate Preparation from Highly Organic Holocene Peat and Lake Deposits for AMS Dating

Radiocarbon ◽  
1994 ◽  
Vol 36 (3) ◽  
pp. 407-412 ◽  
Author(s):  
Ffiona Richardson ◽  
Valerie A. Hall
Keyword(s):  
Pollen Grains ◽  
Fossil Pollen ◽  
Volcanic Event ◽  
Physical Chemical ◽  
Peat Deposits ◽  
Ams Dating ◽  
Novel Method ◽  
Lake Deposits ◽  
Concentrate Preparation ◽  
Concentrate Production

Many of the problems inherent with conventional 14C dating of lake and peat deposits are eliminated by AMS dating of pollen concentrates. Published work describes production of pollen concentrates through expulsion of most of the deposit matrix by repeated deflocculation, selective sieving and final retention of the largest subfossil pollen taxa. Less suited to pollen concentrate production are the highly organic peats and lake muds from the British Isles and Europe. In this study we tested the combined effectiveness of physical, chemical and microbiological degradation and elimination techniques for pollen concentrate production on highly organic peats and a lake mud. We also reviewed methods of enhancing concentrations of smaller sub-fossil pollen grains. Here we present a novel method of assessing AMS dating precision of pollen concentrates by comparing their calibrated dates with a volcanic event of known historical age.

Major environmental and ecological shifts in late Holocene marine sediments of the NW Adriatic Sea

2020 ◽  
Author(s):  
Michaela Berensmeier ◽  
Adam Tomašových ◽  
Zuschin Martin
Keyword(s):  
Adriatic Sea ◽  
Surface Mixed Layer ◽  
Sediment Depth ◽  
Terrestrial Plant ◽  
Plant Remains ◽  
Clayey Silt ◽  
Ecological Shifts ◽  
Homogeneous Composition ◽  
Facies Types ◽  
Mollusc Shells

<p><span>Sediments of the NW Adriatic Sea preserve important information about environmental change</span><span>s</span><span> during the Holocene and due to recent anthropogenic impact. This study is bas</span><span><span>ed</span></span><span> on new data of a 3-m-long gravity core taken from 31 m water depth. Large environmental and ecological shifts are indicated by changes in geochemistry (XRF core scanning data, geochemical bulk analyses) and molluscan composition, particularly in the uppermost decimeters.</span></p><p><span><span>Sedimentologically, the record can be divided into 4 facies types: (1) laminated silty sediments with some sands, terrestrial plant remains, and scarce mollusc shells (at 175-300 cm sediment depth), (2) bioturbated silty, fine-sandy sediments with terrestrial plant remains, scarce mollusc shells, and calcirhizomes (70-175 cm), (3) strongly bioturbated, clayey silt with increasing abundance in mollusc shells (20-70 cm), and (4) clayey silt with a peak in molluscan shell abundances and diversity, with abundant bivalves (</span></span><span><span><em>Corbula gibba</em></span></span><span><span>) and gastropods (</span></span><span><span><em>Turritellinella tricarinata<!-- Sicher? Oder Turritella communis? --></em></span></span><span><span>, 0-20 cm).</span></span></p><p><span><span><em>Corbula gibba</em></span></span><span><span> valves were used for C</span></span><span><sup><span>14</span></sup></span><span><span>-calibrated amino acid racemization (AAR) analyses of valves. The resulting shell ages show a bisection in the record: (1) an uppermost, surface-mixed layer with very young shells (median age = 50 years) and (2) an age-homogeneous composition down to 30 cm sediment depth (median age = 3000 years). This downcore shift in age distributions probably indicates that the 20</span></span><span><sup><span>th </span></sup></span><span><span>century shells of </span></span><span><span><em>Corbula gibba </em></span></span><span><span>are not mixed beyond 10 cm. This pattern implies decreasing bioturbation and increasing sedimentation in the study area in the 20</span></span><span><sup><span>th </span></sup></span><span><span>century.</span></span></p>

scholarly journals An Improved Method for Extracting, Sorting, and AMS Dating of Pollen Concentrates From Lake Sediment

2021 ◽  
Vol 9 ◽  
Author(s):  
Irene Tunno ◽  
Susan R. H. Zimmerman ◽  
Thomas A. Brown ◽  
Christiane A. Hassel
Keyword(s):  
High Resolution ◽  
Sierra Nevada ◽  
Lake Sediment ◽  
Sediment Cores ◽  
Pollen Grains ◽  
Complete Separation ◽  
Improved Method ◽  
Surface Samples ◽  
Common Technique ◽  
Ams Dating

High-resolution chronologies are crucial for paleoenvironmental reconstructions, and are particularly challenging for lacustrine records of terrestrial paleoclimate. Accelerator Mass Spectrometry (AMS) radiocarbon measurement of terrestrial macrofossils is the most common technique for building age models for lake sediment cores, but relies on the presence of terrestrial macrofossils in sediments. In the absence of sufficient macrofossils, pollen concentrates represent a valuable source of dates for building high-resolution chronologies. However, pollen isolation and dating may present several challenges, as has been reported by different authors in previous work over the last few decades. Here we present an improved method for extracting, purifying and radiocarbon-dating pollen concentrates using flow cytometry to improve the extraction efficiency and the purity of the pollen concentrates. Overall, the nature of the sediments and the abundance of the pollen represent major considerations in obtaining enough pollen grains and, consequently, enough carbon to be dated. Further, the complete separation of pollen from other forms of organic matter is required to ensure the accuracy of the dates. We apply the method to surface samples and sediment cores recovered from two contrasting lake basins on the eastern side of the Sierra Nevada (California), and describe the variations that may be used to optimize pollen preparation from a variety of sediments.

scholarly journals Radiocarbon Anomalies Observed for Plants Growing in Icelandic Geothermal Waters

Radiocarbon ◽  
1992 ◽  
Vol 34 (3) ◽  
pp. 696-703 ◽  
Author(s):  
Árný E. Sveinbjörnsdóttir ◽  
Jan Heinemeier ◽  
Niels Rud ◽  
Sigfús J. Johnsen
Keyword(s):  
Lacustrine Sediments ◽  
Geothermal Water ◽  
Small Samples ◽  
Terrestrial Plants ◽  
Fontinalis Antipyretica ◽  
Geothermal Waters ◽  
Aquatic Moss ◽  
Plant Remains ◽  
Ams Dating ◽  
Apparent Age

We have studied plant remains in thick beds of lacustrine sediments in the upper part of the Markarfljót drainage area in southern Iceland. We collected small samples of plant species from the same horizon and 14C dated them at the Aarhus AMS Dating Laboratory. Terrestrial plants yielded an age of 9 ka BP, whereas aquaic moss (Fontinalis antipyretica Hedw.) yielded the surprisingly old 14C age of 16 ka bp. We believe the age of the terrestrial plants reflects the true age of the sediment. The anomalously old 14C age of the aquatic moss may be an effect of geothermal water on the moss, as the area is known to be geothermally active today. Modern aquatic moss growing in geothermal water showed a similar 14C anomaly, with measured ages ranging from 6 to 8 ka BP, which may be explained by the equally old ages measured for the corresponding water samples. The 14C content of geothermal springs and neighboring rivers in the area ranges from 9 to 50 pMC, equivalent to an apparent age of 20–5.5 ka bp.

scholarly journals Post-glacial inflation-deflation cycles, tilting, and faulting in the Yellowstone Caldera based on Yellowstone Lake shorelines

2002 ◽  
Author(s):  
Kenneth L. Pierce ◽  
Kenneth P. Cannon ◽  
Grant A. Meyer ◽  
Matthew J. Trebesch ◽  
Raymond D. Watts
Keyword(s):  
Yellowstone Lake ◽  
Yellowstone Caldera
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