The CREp program and the ICE-D production rate calibration database: A fully parameterizable and updated online tool to compute cosmic-ray exposure ages

TLDR: The Octave/Matlab software for cosmogenic exposure dating has been described in this paper, where the authors present the CREp program and the ICE-D production rate online database.

About: This article is published in Quaternary Geochronology.The article was published on 2017-03-01 and is currently open access. It has received 139 citations till now.

Figures

Table 2 Geomagnetic reconstructions used in the scaling models of the CREp program.

Fig. 2. Global map showing the distribution of the calibration sites for 3He and 10Be production rates that are loaded from ICE-D to the CREp program. Contours of the “regions” defined in the present version of CREp are also drawn.

Table 5 Global SLHL P10 dataset computed with 12 scaling procedures (n ¼ 31). Data from (Balco et al., 2009; Borchers et al., 2016; Briner et al., 2007, 2012; Claude et al., 2014; Farber et al., 2005; Fenton et al., 2011; Goehring et al., 2012; Kaplan et al., 2011; Kelly et al., 2015; Lifton et al., 2015; Martin et al., 2015; Nishiizumi et al., 1989; Phillips et al., 2016; Putnam et al., 2010; Young et al., 2013).

Fig. 5. A) Probability density plot of SLHL 10Be production rates from the ICE-D database. Plots of the global SLHL P10 calibration dataset against B) latitude, C) altitude and D) exposure age. These SLHL PR data are computed using the LSD-ERA-Lift scaling procedure.

Fig. 4. A) Probability density plot of SLHL 3He production rates from the ICE-D database. Plots of the global SLHL P3 calibration dataset against B) latitude, C) altitude and D) exposure age. These SLHL PR data are computed using the LSD-ERA-Lift scaling procedure.

Fig. 3. Flow chart showing the raw data processing to compute a SLHL production rate from each calibration site.

Frequently asked questions

Q1. What contributions have the authors mentioned in the paper "The crep program and the ice-d production rate calibration database: a fully parameterizable and updated online tool to compute cosmic- ray exposure ages" ?

This study describes the CREp program ( http: //crep. crpg. cnrs-nancy. fr ) and the ICE-D production rate online database ( http: //calibration. ice-d. org ). A stand-alone version of the CREp code is also released with the present article. For the important choice of the production rate, CREp is linked to a database of production rate calibration data that is part of the ICE-D ( Informal Cosmogenic-nuclide Exposure-age Database ) project ( http: //calibration. ice-d. org ). This database includes published empirical calibration rate studies that are publicly available at present, comprising those of the CRONUS-Earth and CRONUS-EU projects, as well as studies from other projects. In the present study, the efficacy of the different scaling models has also been evaluated looking at the statistical dispersion of the computed Sea Level High Latitude ( SLHL ) production rates. If a regional production rate is picked, these uncertainties are potentially lower. 

Q2. What have the authors stated for future works in "The crep program and the ice-d production rate calibration database: a fully parameterizable and updated online tool to compute cosmic- ray exposure ages" ?

New geomagnetic and atmospheric databases with improved accuracy will probably be added in the future. Since the authors designed the online calculator CREp and the ICE-D database to be constantly upgraded with the latest updates of cosmogenic nuclide systematics, they will greatly appreciate future readers ' suggestions. 

Q3. What is the process of calculating the production rate of a cosmogenic nuclide?

As production rates vary with latitude, altitude, and also with time due to temporal fluctuations in the atmospheric density and the Earth's magnetic field, a complicated scaling procedure is necessary to obtain the appropriate production rate for dating. 

Q4. What is the typical method of calculating the production rate of a cosmogenic nucli?

The usual method consists of, first, converting the reference production rate at a calibration site into a Sea Level High Latitude (SLHL) rate, corrected for the past geomagnetic activity over the calibration time period. 

Q5. What is the reason why the LSD model is prone to overestimate the production rate?

Neutron-monitor based models (Desilets and Zreda, 2003; Desilets et al., 2006; Dunai, 2001; Lifton et al., 2005) are prone to overestimate the altitude dependence of cosmogenic-nuclide production while the older Lal-Stone model turned out to be robust and in good agreement with the LSDmodel. 

Q6. What is the way to scale the cosmic-ray flux?

The authors thus use this as a first order indicator of the scaling ability to take into account the spatial and temporal variability of the cosmic-ray flux: the lower MSWD, the better the scaling procedure is. 

Q7. What is the way to improve CREp?

In this regard, a great improvement to CREp would be to add a time variable atmospheric pressure field, that could be, for example, derived from global circulation models (e.g. Staiger et al., 2007). 

Q8. What is the effect of the exclusion of outliers?

given the number of calibration sites in the existing dataset (31 calibration sites for 10Be and 23 sites for 3He), the exclusion of outliers should not have a big effect.