Greetings,

I am doing some work with gases in the Los Angeles Basin- specifically
looking at 13C isotope ratios of shallow gases from soils in the vicinity of
some of the Los Angeles oil fields.  I have found, quite unexpectedly, that
there is a significant amount of hydrogen in most of our samples collected
from less that 100 ft below surface.  Up to 4% vol., and in most cases
methane is only present at ppm levels.  Has anyone encountered similar gas
systems who could point me toward some appropriate references discussing
origin/migration pathways, etc?

Thanks in advance,
Devon Rowe