Geology Reference
In-Depth Information
Table 1. Review of nanofibres in the literature
Authors
Nomenclature
Geological setting
Interpretation/context
Pouget & Rambaud
(1980)
Calcite 'en
bˆtonnets'
Soil with calcareous crust
Mesh of monocrystaline
calcite crystals
Verg`s et al. (1982)
Small needle-shaped
crystals
Calcareous soils
Tangled crystals
Ducloux et al. (1984)
Calcite 'en
bˆtonnets'
Developed on screeslope
Covering larger needle-fibre
calcite crystals
Phillips & Self (1987) Micro-rods
Pedogenic calcrete
Interpreted as calcified
rod-shaped bacteria
Phillips et al. (1987)
Submicron size
rods
Pedogenic calcrete
Interpreted as calcified
rod-shaped bacteria
Jones & Ng (1988)
Needles
Rhizolith from the Pleistocene
Ironshore Formation
Calcified filaments coated
withneedles (i.e.
nanofibres)
Verrecchia &
Verrecchia (1994)
Micro-rods
Quaternary calcretes, Israel
Disordered mesh
Loisy et al. (1999)
Micro-rods
Carbonate paleosol in scree
deposits
Mineralized threadlike and
bacilliform bacteria
Borsato et al. (2000)
Nanofibres
Moonmilk (cave deposits)
Probably abiogenic
precipitation
Benzerara et al.
(2003)
Nanobacteria-like
rods
At the surface of the
Tataouine meteorite
Straight micro-alignment of
nanofibres; possible
organic origin
Cailleau et al. (2005) Micro-rods
Orthox soils
Observed on burnt oxalate
crystals embedded in tree
tissues
Jeong & Chun (2006)
Nanofibre calcite
Aerosols coming from loess
plateau and desert
-
Richter et al. (2008)
Nanofibres
Moonmilk (cave deposits)
-
Note: Review of nanofibres present in soils and caves: nomenclature, occurrence and interpretation in the literature.
Fungal presence and activity
in soil and caves
Fungi are present in large amounts in soils. As an
example, one metre square of fertile soil can
contain a 10 000-km long fungal network (Gobat
et al. 2003). About 80% of land plant species are
colonized by arbuscular mycorrhizal fungi (endo-
mycorrhiza), and around 3% of phanerogam
species are colonized by ectomycorrhizal fungi
(EcM), especially plants with a large distribution
at a global scale (Pinaceae, Fagaceae). In soils, a
vertical distribution can be distinguished regarding
fungal type in terms of their ecology. Organic
layers are mostly colonized by saprophytic fungi,
whereas mineral layers are colonized by EcM
fungi (van Sch
¨
ll et al. 2008). The latter has been
demonstrated as being a significant agent of
mineral weathering of ecosystem-wide importance
(van Sch
¨
ll et al. 2008).
The mycelial network is able to efficiently trans-
locate nutrients in solution from one place to another
(Gobat et al. 2003). Basidiomycetes, and among
them EcM fungi, are able to build structures
named fungal strands that can extend meters away
from the roots (Finlay & S¨derstr¨m 1992; van
Sch¨ ll et al. 2008). Thus, the presence of mycor-
rhized roots, fungal hyphae and strands in deep
mineral layers or in caves is not surprising. Canadell
et al. (1996) showed an average rooting depth of
4.6 m þ/20.5 m, with a maximum depth of 7.0 m
þ/21.2 m for trees. In their review, only the root
itself is taken into account. Considering the mycor-
rhiza, it can considerably extend the root network
(Timonen & Marschner 2006). Observations of
roots at depths below 2-3 m in caves have also
been observed (Canadell et al. 1996). Jasinska
et al. (1996) demonstrated that root mats could be
the sole source of food for faunal communities in
an Australian cave.
Cave geomicrobiology
Caves are nutrient-limited environments due to the
absence of light that prevents primary production
through photosynthesis, contrary to other common
environments on Earth. Thus, in terms of presence
of life, this kind of environment can be considered
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