Environmental Engineering Reference
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trace fossils ( Gong et al., 2007 ), microborings ( Wisshak, 2012 ), drill holes
in prey skeletons ( Schiffbauer et al., 2008 ), subtle bioturbation fabrics and
microburrows in fine-grained sediment ( O'Brien and Pietraszek-Mattner,
1998 ), grain-size differences in burrow walls ( Zorn et al., 2010 ) or other micro-
structural features, and chemical changes related to trace fossils ( Driese and
Foreman, 1991 ). Thomsen and Vorren (1984) used SEM, energy dispersive
X-ray, microprobe, and X-ray diffractometer to study the composition of pyri-
tized Trichichnus -like burrows. An introduction to SEM and related techniques
for geologists is given by Reed (2010) .
3.5 X-ray Radiography
X-ray radiography is an effective technique to reveal internal structures in var-
ious kinds of sediments and rock slabs, especially those taken from core. The
gray-scale images acquired from the core slab reflect primarily sediment den-
sity as a function of lithology, grain size, and cementation, and reveal biotur-
bation and trace fossils in high resolution, which otherwise would be
invisible ( Bouma, 1969; L ¨ wemark, 2007 ). Digital X-ray systems gradually
replace conventional systems working with film and permit a convenient appli-
cation both in the laboratory and in the field ( St-Onge et al., 2007 ).
There are many examples of applications that mainly cover unlithified and
apparently homogeneous Quaternary deposits from shallow-marine to deep-
marine environments ( Bouma, 1964; Howard, 1968; L¨wemark, 2003;
L¨wemark and Sch¨fer, 2003; Werner and Wetzel, 1982; Winn, 2006 ). In con-
trast, X-ray radiography is not fully utilized in the study of bioturbation and trace
fossils in industrial well cores ( Gerard and Bromley, 2008; Pemberton and Gin-
gras, 2005 ). L¨wemark et al. (2006) used the deformation of pyritized trace fossils
as recognized in X-ray radiographs to estimate core shortening in gravity cores.
3.6 Computer-Aided Tomography
Axial tomography (CAT scan) and high-resolution X-ray microcomputed
tomography are relatively young techniques that allow for non-destructive visu-
alization and quantification of sedimentary structures, trace fossils, and orga-
nisms, preferably captured in cored samples ( Dufour et al., 2005; Fu et al.,
1994; St-Onge et al., 2007; Sutton, 2008 ). During the scan process, a series
of X-ray radiographs is captured at constant increments as the sample contin-
uously rotates between the emitter and detector. The different attenuation at
each scanned point (voxel) provides the basis for the reconstruction of two-
dimensional images, which again allow for generating a three-dimensional
image of the burrow or boring inside the sample.
Computer-aided tomography has been applied to quantify the amount of
bioturbation in the scope of hydrocarbon and aquifer characterization
( Cunningham et al., 2009, 2012; Pemberton and Gingras, 2005 ), to study marine
and terrestrial benthic communities ( Dufour et al., 2005; Perez et al., 1999 ), to
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