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@ARTICLE{Horsfield:57359,
author = {Horsfield, B. and Schenk, H. J. and Zink, K. and Ondrak, R.
and Dieckmann, V. and Kallmeyer, J. and Mangelsdorf, K. and
di Primio, R. and Wilkes, H. and Parkes, R. J. and Fry, J.
and Cragg, B.},
title = {{L}iving microbial ecosystems within the active zone of
catagenesis: implications for feeding the deep biosphere},
journal = {Earth and planetary science letters},
volume = {246},
issn = {0012-821X},
address = {Amsterdam [u.a.]},
publisher = {Elsevier},
reportid = {PreJuSER-57359},
year = {2006},
note = {Record converted from VDB: 12.11.2012},
abstract = {Earth's largest reactive carbon pool, marine sedimentary
organic matter, becomes increasingly recalcitrant during
burial, making it almost inaccessible as a substrate for
microorganisms, and thereby limiting metabolic activity in
the deep biosphere. Because elevated temperature acting over
geological time leads to the massive thermal breakdown of
the organic matter into volatiles, including petroleum, the
question arises whether microorganisms can directly utilize
these maturation products as a substrate. While migrated
thermogenic fluids are known to sustain microbial consortia
in shallow sediments, an in situ coupling of abiotic
generation and microbial utilization has not been
demonstrated. Here we show, using a combination of basin
modelling, kinetic modelling, geomicrobiology and
biogeochemistry, that microorganisms inhabit the active
generation zone in the Nankai Trough, offshore Japan. Three
sites from ODP Leg 190 have been evaluated, namely 1173,
1174 and 1177, drilled in nearly undeformed Quaternary and
Tertiary sedimentary sequences seaward of the Nankai Trough
itself. Paleotemperatures were reconstructed based on
subsidence profiles, compaction modelling, present-day heat
flow, downhole temperature measurements and organic maturity
parameters. Today's heat flow distribution can be considered
mainly conductive, and is extremely high in places, reaching
180 mW/m(2). The kinetic parameters describing total
hydrocarbon generation, determined by laboratory pyrolysis
experiments, were utilized by the model in order to predict
the timing of generation in time and space. The model
predicts that the onset of present day generation lies
between 300 and 500 m below sea floor (5100-5300 m below
mean sea level), depending on well location. In the case of
Site 1174, $5-10\%$ conversion has taken place by a present
day temperature of ca. 85 degrees C. Predictions were
largely validated by on-site hydrocarbon gas measurements.
Viable organisms in the same depth range have been proven
using C-14-radiolabelled substrates for methanogenesis,
bacterial cell counts and intact phospholipids. Altogether,
these results point to an overlap of abiotic thermal
degradation reactions going on in the same part of the
sedimentary column as where a deep biosphere exists. The
organic matter preserved in Nankai Trough sediments is of
the type that generates putative feedstocks for microbial
activity, namely oxygenated compounds and hydrocarbons.
Furthermore, the rates of thermal degradation calculated
from the kinetic model closely resemble rates of respiration
and electron donor consumption independently measured in
other deep biosphere environments. We deduce that
abiotically driven degradation reactions have provided
substrates for microbial activity in deep sediments at this
convergent continental margin. (c) 2006 Elsevier B.V. All
rights reserved.},
keywords = {J (WoSType)},
cin = {ICG-V},
ddc = {550},
cid = {I:(DE-Juel1)VDB51},
pnm = {Geosysteme - Erde im Wandel},
pid = {G:(DE-Juel1)FUEK405},
shelfmark = {Geochemistry $\&$ Geophysics},
typ = {PUB:(DE-HGF)16},
UT = {WOS:000239200800005},
doi = {10.1016/j.epsl.2006.03.040},
url = {https://juser.fz-juelich.de/record/57359},
}