Be exposure age calculator MATLAB function reference Version 2

logspace(log10(810000),7,200) gives 200 log-spaced points from 0.8 to 10 Myr. Note that 99% saturation
occurs at 9.97 Myr for 10 Be and 4.69 Myr for 26 Al. This means that the calculation is not strictly accurate for
near-saturated surfaces. Thus, this function is conservative about deciding whether or not an age can be calculated:
measurements that are very close to saturation will probably be reported as saturated. If you are interested in a very
precise evaluation of whether or not a particular measurement is saturated with respect to a particular scaling scheme,
this code is not for you.
2.2. Calculate cutoff rigidity Rc as a function of time
We use the same magnetic field reconstruction for all the time-dependent scaling schemes; however, the different
schemes use different methods for deriving the cutoff rigidity from the magnetic field parameters. From 0-7000 yr BP,
the magnetic field is taken to be the spherical harmonic reconstruction of Korte and Constable. For 7000 - 800,000 BP,
the field is taken to be a geocentric axial dipole with intensity given by Yang at al. (7000 - 11,500 BP) and SINT800
(11,500 - 800,000 BP). Prior to 800,000 BP, the magnetic field is assumed to be a geocentric axial dipole with the
average intensity of the SINT800 record.
The main text of the paper gives additional details about the source of the magnetic field data and the derivatives
thereof.
For the De scaling scheme, for 0-7000 yr BP, cutoff rigidity is directly interpolated for the sample site from the global
grids of cutoff rigidity values obtained by trajectory tracing at 500-year intervals (Lifton and others (in prep) describe
this calculation in more detail) Before 7000 BP, the cutoff rigidity R C is calculated from the geographic latitude of the
sample according to equation (19) of Desilets et al. (2003):
R C =
6∑
i=0
[e i + f i
( M
M 0
)]
θ (i) (5)
where (M/M 0 ) is the ratio of the field intensity at the past time of interest to the present field intensity and θ is the
geographic latitude of the sample. The constants e i and f i are as follows:
i e i f i
0 −4.3077x10 −3 1.4792x10 +1
1 2.4352x10 −2 −6.6799x10 −2
2 −4.6757x10 −3 3.5714x10 −3
3 3.3287x10 −4 2.8005x10 −5
4 −1.0993x10 −5 −2.3902x10 −5
5 1.7037x10 −7 6.6179x10 −7
6 −1.0043x10 −9 −5.2083x10 −9
For the Du scaling scheme, for 0-7000 yr BP, cutoff rigidity is directly interpolated for the sample site from global
grids of cutoff rigidity values that were obtained by applying equation (2) of Dunai (2001) to the horizontal field
intensity and inclination of the Korte and Constable field model, again at 500-year intervals. We thank Nat Lifton for
generating these grids. Before 7000 BP, the cutoff rigidity R C is calculated from the geographic latitude of the sample
according to equation (1) of Dunai (2001):
( ) M
R C = 14.9 [cos(θ)] 4 (6)
M 0
For the Li scaling scheme, for 0-7000 yr BP, cutoff rigidity is directly interpolated for the sample site from the global
grids of cutoff rigidity values obtained by trajectory tracing. Before 7000 BP, the cutoff rigidity R C is calculated from
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