scholarly journals High-precision radioisotopic ages for the lower Midian (upper Wordian) Stage of the Tethyan time scale, Shigeyasu Quarry, Yamaguchi Prefecture, Japan

2019 ◽  
Vol 527 ◽  
pp. 133-145 ◽  
Author(s):  
V.I. Davydov ◽  
M.D. Schmitz
Keyword(s):  
High Precision ◽  
Time Scale

scholarly journals High-Precision Bidecadal Calibration of the Radiocarbon Time Scale, 500–2500 BC

Radiocarbon ◽  
1993 ◽  
Vol 35 (1) ◽  
pp. 25-33 ◽  
Author(s):  
Gordon W. Pearson ◽  
Minze Stuiver
Keyword(s):  
High Precision ◽  
Time Scale ◽  
Count Rate ◽  
Basic Information ◽  
Data Set ◽  
Sole Purpose ◽  
Radon Decay

The sole purpose of this paper is to present a previously published 14C data set to which minor corrections have been applied. All basic information previously given is still applicable (Pearson & Stuiver 1986). The corrections are needed because 14C count-rate influences (radon decay in Seattle, a re-evaluation of the corrections applied for efficiency variation with time previously unrecognized in Belfast) had to be accounted for in more detail. Information on the radon correction is given in Stuiver and Becker (1993). The Belfast corrections were necessary because the original correction for efficiency variations with time was calculated using two suspect standards (these were shown to be suspect by recent observations) that overweighted the correction. A re-evaluation (Pearson & Qua 1993) now shows it to be almost insignificant, and the corrected dates (using the new correction) became older by about 16 years.

scholarly journals High-Precision Calibration of the Radiocarbon Time Scale, 3930–3230 Cal BC

Radiocarbon ◽  
1986 ◽  
Vol 28 (2B) ◽  
pp. 939-941 ◽  
Author(s):  
AFM de Jong ◽  
Bernd Becker ◽  
WG Mook
Keyword(s):  
River Basin ◽  
High Precision ◽  
Tree Rings ◽  
Time Scale ◽  
Danube River ◽  
The South ◽  
The Danube River ◽  
Danube River Basin

This paper contains 14C results obtained by the special high-precision proportional gas counter, designed by Tans and Mook (1978), on tree rings from the South German oak chronologies: Donau 7, 3, 10, and 12, originating from the Danube River basin (48° 24’ N, 10° 5’ E).

Chronometric calibration of mid-Ordovician to Tournaisian conodont zones: a compilation from recent graphic-correlation and isotope studies

1992 ◽  
Vol 129 (6) ◽  
pp. 709-721 ◽  
Author(s):  
Barry G. Fordham
Keyword(s):  
High Resolution ◽  
High Precision ◽  
Time Scale ◽  
Lower Devonian ◽  
New South ◽  
Upper Ordovician ◽  
South Wales ◽  
Isotope Studies ◽  
Stratotype Section ◽  
Upper Silurian

AbstractThree available graphic-correlation analyses are used to calibrate mid-Palaeozoic conodont zonations: Sweet's scheme for the mid- to Upper Ordovician; Kleffner's for the mid- to Upper Silurian; and Murphy & Berry's for the lower and middle Lower Devonian. The scheme of Sweet is scaled by applying the high-precision U-Pb zircon date of Tucker and others for the Rocklandian and linked with that of Kleffner by scaling the graptolite sequence of the Ordovician-Silurian global stratotype section to fit two similarly derived dates from this sequence. The top of Kleffner's scheme, all of Murphy & Berry's, as well as standard zones to the Frasnian are calibrated by using tie-points of the latest Cambridge-BP time-scale (GTS 89). However, the recent microbeam zircon date by Claoué-Long and others for the Hasselbachtal Devonian-Carboniferous auxiliary stratotype is used to calibrate the standard Famennian zones. Also the similarly derived but preliminary determination reported by Roberts and others from the Isismurra Formation of New South Wales is tentatively taken as the top of the Tournaisian and so used to calibrate Tournaisian zones. Despite the considerable extrapolation required to compile these schemes and their inherent errors, the resultant time-scale closely agrees with other dates of Tucker and others from the Llanvirn as well as the GTS 89 Homerian-Gorstian tie-point. This suggests that stratigraphic methods can be usefully applied to geochronometry. The Llandovery appears to have lasted longer (16 m. y.) than usually envisaged and the Ordovician-Silurian boundary may need to be lowered to approximately 443.5 Ma. Certainly, chrons varied widely in duration and further stratigraphic studies to estimate their relative durations as well as high-resolution dating for their calibration will be crucial to more accurate biochronometries.

scholarly journals Calibration of the Radiocarbon Time Scale for the Southern Hemisphere: Ad 1850–950

Radiocarbon ◽  
2002 ◽  
Vol 44 (3) ◽  
pp. 641-651 ◽  
Author(s):  
F G McCormac ◽  
P J Reimer ◽  
A G Hogg ◽  
T F G Higham ◽  
M G L Baillie ◽  
...  
Keyword(s):  
South Africa ◽  
New Zealand ◽  
Southern Hemisphere ◽  
High Precision ◽  
Time Scale ◽  
Calibration Data ◽  
Data Set ◽  
Calibration Data Set ◽  
Consequent Effect

We have conducted a series of radiocarbon measurements on decadal samples of dendrochronologically dated wood from both hemispheres, spanning 1000 years (McCormac et al. 1998; Hogg et al. this issue). Using the data presented in Hogg et al., we show that during the period AD 950–1850 the 14C offset between the hemispheres is not constant, but varies periodically (∼130 yr periodicity) with amplitudes varying between 1 and 10% (i.e. 8–80 yr), with a consequent effect on the 14C calibration of material from the Southern Hemisphere. A large increase in the offset occurs between AD 1245 and 1355. In this paper, we present a Southern Hemisphere high-precision calibration data set (SHCal02) that comprises measurements from New Zealand, Chile, and South Africa. This data, and a new value of 41 ± 14 yr for correction of the IntCal98 data for the period outside the range given here, is proposed for use in calibrating Southern Hemisphere 14C dates.

scholarly journals A REFINING METHOD OF NON-LINEAR REGIONAL TM MODEL BASED ON RANDOM FOREST

2020 ◽  
Vol XLII-3/W10 ◽  
pp. 1169-1174
Author(s):  
Q. T. Wan ◽  
L. L. Liu ◽  
L. K. Huang ◽  
W. Zhou ◽  
Y. Z. Yang ◽  
...  
Keyword(s):  
Water Vapor ◽  
Random Forest ◽  
Surface Temperature ◽  
High Precision ◽  
Time Scale ◽  
Coastal Areas ◽  
Eastern Coast ◽  
Observation Data ◽  
Improvement Effect ◽  
Tm Model

Abstract. Weighted mean temperature (Tm) is a critical parameters in GNSS technology to retrieve precipitable water vaper (PWV). By obtaining high-precision Tm, it can provide an important reference data source for regional strong convective weather and large-scale climate anomalies. The high-precision Tm of most areas can be obtained by using the BEVIS model and the surface temperature (Ts). The eastern coastal areas of China are affected by the monsoon climate, which makes the applicability of the method in this area to be improved. The research shows that the Tm which calculated by Fourier series analysis (FTm model) has better applicability in the region than the BEVIS model. However, the method has a single modeling factor, and the precision improvement effect in some area is not obvious. By using the observation data of 13 radiosonde stations in the eastern coastal areas of China from 2010 to 2015. Tm which calculated by numerical integration is used as the reference of the true value. Four of the observation data are selected by the method of random forest (RF). The eigenvalues include the pressure、surface temperature、water vapor pressure and specific humidity are used as input factors. The prediction corrections are added to the deviation of FTm model, and a new Tm is applied to the eastern coast of China which called RFF Tm. Taking the observation data from 2010 to 2014 as the training database, the research area is divided into three areas from south to north according to the latitude. The prediction results of different time scales are studied by the clamping criterion, and then the prediction of random forest is discussed. The correction effect is adaptable in the eastern coast areas of China. The results show that: (1) The RFF Tm model refinement method based on random forest has better adaptability in eastern coastal areas of China, and the applicability of first area is more stable with the prediction time scale than the FTm model. (2) On the time scale with a forecast period of one year, MAE and RMS are 4.7 and 4.6 in third area, 3.2 and 3.8 in second area, and 2.6 and 2.5 in first area. (3) The improvement effect of random forests in the eastern coastal areas of China gradually increases with the prediction period becoming shorter. The predicted deviation values of the eastern coast areas of China reach a steady state when the period is one month. The correction deviations is within 1.5K. The correction range of the third area is better than the second area and first area, which makes up for the shortcomings of the FTm model with low precision in the region. It can be used as a new multi-factor prediction and correction Tm model for GNSS remote sensing water vapor in the eastern coastal areas of China.

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