Geological cross-section of the Siberian sampling
sites showing the variously aged layers, QIV
(7-10 x 103 YBP), QIII (30-40 x 103YBP), QII
(100-120 x 10 3YBP) and N2 (> 0.7 x 106YBP).
The inset photograph shows the ice wedges that
verify the continuously frozen state of the
QIII layer. Samples for methane production
under temperatures equivalent to in situ conditions
were from the zone marked 'a'. Samples from
the brine lenses that were active in glucose
assimilation at in situ temperatures came from
the zone marked 'b'.