Surface exposure ages from Hjorth Hill, McMurdo Sound, Antarctica

This data base contains information on cosmogenic helium-3 and
beryllium-10 surface exposure dates on Ross Sea Drift moraine boulders
from Hjorth Hill, McMurdo Sound, Antarctica (77 degrees 31' South,
163 degrees 37' East). This study was designed to combine surficial
ages with a Ground Penetrating Radar data set generated by
Dr. M. Prentice at the University of New Hampshire.

Surface exposure dating relies on the build-up of cosmogenic nuclides
in materials exposured to cosmic radiation. Because cosmogenic rays
only penetrate 2 m in rock, freshly eroded glacial debris only begins
accumulating cosmogenic nuclides after deposition from the glacier.
When production rates are known the concentration of cosmogenic
nuclides in moraine boulders can be used to date formation of end
moraines and drift sheets.

The samples were collected by M.D. Kurz and R. Ackert and colleagues
during the 1990 and 1992 field seasons. The samples are archived at
Woods Hole Oceanographic Institution. The ages, provided below in
the table, provide age constraints on this important record of past
fluctuations of the West Antarctic Ice Sheet.

Surface exposure ages from Hjorth Hill
--------------------------------------------3He 10Be
Sample moraine Lithology mineral alt (m) Age (+-1 sig) Age (+-1 sig)
...........................................(kyrs) (kyrs)
GP92-641-2 RS1r basalt olivine 300 40.0 0.8
KBA89-140 RS2 basalt olivine 310 56.7 1.8
KBA89-142 RS2 basalt olivine 310 83.3 2.7
KBA89-143 RS2 granite quartz 310 28.4 0.7 38.1 2.7
KBA89-148 RS2 quartzitequartz 310 47.9 0.6 48.2 0.7
DK92-477-3 W3 basalt olivine 365 21.4 0.8
DK92-477-4-1 W3 basalt cpx 365 40.6 1.2
DK92-477-4-2 W3 basalt cpx 365 29.3 1.7

3He ages calculated using production rate of 121 and 133 at/g/yr
(sealevel, high lat) for olivine and quartz respectively.

10Be ages calculated using production rate of 5.1 at/g/yr

RS1r=Ross Sea Drift recessional moraine
S2= older Ross Sea Drift
W3= Wilson-Piedmont drift