How do we calibrate shell AMS dates that return as % modern, eg 118.5 +/- 0.41 % with delta R = 84 +/- 57 Southern hemisphere?

[Rach]

Dear Christopher, thanks for your help on my previous question. I have
another one:
How do we calibrate shell AMS dates that return as % modern, eg 118.5
+/- 0.41 % with delta R = 84 +/- 57 Southern hemisphere? As we have
been told we need to apply the marine reservoir correct to the shell
AMS dates before we calibrate with CALIBOMB if we have a % modern
result.

I did this:

Plot()
Curve("Marine04","Marine04.14c")
Delta_R("LocalMarine",84,57)
R_F14C("19373", 118.5, 0.4)
z=20

It returned a median cal of 84 +/- 57 (which is our delta R). Is this
correct? What does 0 on x axis mean? eg does it mean 1950?

Cheers
Rach

[Christopher Ramsey]

Three observations on this.

1. To specify exactly what the code is the {, } and ; symbols are
important so you know what the statements refer to - I think this is:

2. The R_F14C takes F14C not %modern. The latter has various
different definitions, but assuming it was corrected for d13C you just
need to divide by 100 which would make the code:

Plot()
{
Curve("Marine04","Marine04.14c");
Delta_R("LocalMarine",84,57);

R_F14C("19373", 1.185, 0.004)
{
z=20;
};
};

3. The Marine04 curve does not go into the post-bomb period and so
this will not work anyway. The injection of bomb 14C into the oceans
is so complex (see the whole WOCE program) that it is not practical to
use marine material for dating in this period unless you effectively
have a local record of variation over time throughout this period.

Christopher