Abiotic oil : a dissenting view


Richard Moore



Upwelling of Hot Gas 
Alton Brown 

The Deep, Hot Biosphere . Thomas Gold. 235 pp. Copernicus,
1999. $27.

This book's title is Thomas Gold's hypothesis: that most
subsurface microbial food chains are based on nonbiological
hydrocarbons upwelling from deep in the earth. This hypothesis
is not very well defended. Only two of the chapters discuss
microbial communities, and these chapters really avoid the
topic of subsurface microbial metabolism, the key aspect of
the hypothesis. In fact, this theory is at odds with the
observation that most known deep microbes are found in
fermentative communities that produce hydrocarbons (methane)
rather than consume it.

Despite the title, the real focus of this book is the
deep-earth gas hypothesis. Gold believes that most recoverable
hydrocarbons were derived from space as the earth accreted.
These primordial hydrocarbons, the theory goes, reside in the
lower crust and upper mantle and slowly charge shallower
conventional petroleum accumulations along planes of tectonic
weakness. Because chemicals derived exclusively from bacteria
are found in oil, Gold calls on subsurface microbial
metabolism to contaminate the primordial oil. Most of the book
elaborates and presents supporting evidence for this theory to
a general audience.

Arguments in favor of the deep-earth gas hypothesis sound
quite convincing on the surface to the uninitiated. But those
arguments are deceptive. Well documented and theoretically
justified criticisms of this hypothesis and explanations for
almost all of the proposed inadequacies of the conventional
model for petroleum generation have been published in the past
decade, yet these criticisms and alternate interpretations are
not mentioned or rebutted here. Key issues unexplained in this
book are the occurrence of other chemicals in oils (such as
steroids), indicative of specific eukaryotic sources, carbon
isotopic fractionation patterns observed in normal alkane
species inconsistent with an inorganic origin, and the ability
of the conventional petroleum-generation model to predict
where and how much of a specific oil type will be found in a
geological basin.

I do not recommend this book for either its microbiological or
geological aspects. The exciting and diverse world of
subsurface microbiology is reduced to a pale caricature of
itself. Arguments supporting the deep-earth gas hypothesis may
have been valid 30 years ago, but we now know too much about
the subsurface and about petroleum geochemistry to seriously
consider these ideas in the form in which they are presented
here. Like all evolving scientific theories, the conventional
model of petroleum generation is still subject to modification
in its details. But overall, it is alive and well, and the
criticisms raised here are not likely to substantially change
the model.- Alton Brown, Atlantic Richfield     Company,
Plano, Texas

© Sigma Xi, The Scientific Research Society 


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