The Ichnofacies Paradigm - Trace Fossils as Indicators of Sedimentary Environments - page 113

Of these ethological categories, dwelling traces are the most problematic in
that most domiciles are used as a platform for feeding as well. For example, in
the marine realm, domiciles can be used for filter-feeding ( Lingulichnus ,
Siphonichnus , Skolithos ), interface deposit-feeding ( Siphonichnus , Skolithos ,
Arenicolites ), carnivory and predation ( Skolithos , Palaeophycus ), waste stow-
age ( Asterosoma , Zoophycos ; Bromley, 1991; Kotake, 1991, 1992 ), or scaveng-
ing ( Psilonichnus ). In these instances, ichnological analyses depend, in part, on
sedimentological analyses and in establishing the knowledge of how food was
likely distributed in the environment. Deposit-feeding traces generally are
intrastratal in nature, focused within certain sedimentary levels, and show evi-
dence of sediment ingestion or reworking (e.g., Macaronichnus , Phycosiphon ,
Planolites , Scolicia ). As a result, many deposit-feeding trace fossils are easily
identified and interpreted. Grazing traces are associated with the systematic
processing of shallow-sediment tiers (e.g., Nereites , Helminthopsis ), an inter-
pretation supported by modern observations (e.g., Wetzel, 1991, 2002 ) and
computer-generated behavioral evolution models ( Papentin, 1973 ). Finally,
farming traces dominantly comprise complex, permanent architectures that
show no evidence of sediment processing (e.g., Spirorhaphe ; Seilacher, 1977 ).
3. THE SEILACHERIAN ICHNOFACIES
The Seilacherian ichnofacies ( Bromley, 1990, 1996 ) comprise temporally
and spatially recurring, ethologically distinct groupings of trace-fossil suites
(e.g., Buatois andM´ngano, 2011; Frey et al., 1990; Hunt and Lucas, 2007; MacEa-
chern et al., 2007a,b,c, 2010; Pemberton et al., 1992 ). We regard there to be 14 for-
mally defined ichnofacies that adhere to Seilacher's (1953a,b) original approach
(see Tables 1 and 2 ). Five ichnofacies encompass the marine to marginal-marine
softground realm: the Psilonichnus Ichnofacies for high intertidal and supratidal,
predominantly sandy settings ( Fig. 1 ); the Skolithos Ichnofacies for intertidal to shal-
low subtidal, high-energy, sandymarine environments ( Fig. 2 ); the Cruziana Ichno-
facies for shallow subtidal, moderate energy silty to muddy marine settings ( Fig. 3 );
the Zoophycos Ichnofacies for subtidal, low-energy, silty, and muddy marine con-
ditions ( Fig. 4 ); and the Nereites Ichnofacies for subtidal, very low-energy silty to
muddy marine environments characterized by extremely slow deposition ( Fig. 5 ).
Three ichnofacies encompass post-depositional colonization of substrates, generally
regarded as substrate-controlled (omission) ichnofacies: the Glossifungites
Ichnofacies, reflecting colonization of firmground (dewatered and compacted but
unlithified) substrates in marginal-marine and marine settings ( Fig. 6A ); the Trypa-
nites Ichnofacies, associated with lithified (hard) substrates in marine settings
( Fig. 6B ); and the Teredolites Ichnofacies for colonization of xylic (woodground)
substrates in marine and marginal-marine environments ( Fig. 6C and D ). Finally,
six ichnofacies encompass the continental realm: the Scoyenia Ichnofacies associ-
atedwith intermittently subaqueous, softground substrates ( Fig. 7AandB ); the Mer-
mia Ichnofacies for permanently subaqueous freshwater settings ( Fig. 7C ); the