The Ichnofacies Paradigm - Trace Fossils as Indicators of Sedimentary Environments - page 104

TABLE 2 General Characteristics and Environmental Aspects of the Continental

Seilacherian Ichnofacies

Ichnofacies Environmental constraints Settings

Moist to wet, argillaceous to sandy
substrates; sporadically to persistently
exposed. Pore-moisture contents and
temperatures variable. Food present as
surface detritus. Mainly stiffgrounds in
low-energy sites.

Low-energy continental settings
with intermittent subaerial
conditions. Settings are inundated
with freshwater, particularly during
river floods. Environments include
upper point bars, channel banks,
crevasse splays, lake margins and
floodplains adjacent to channels.

Scoyenia

Low-energy, permanently subaqueous
substrates. Sedimentation rates low but
locally variable. Dissolved oxygen and
total dissolved solids vary locally. Food
deposited on or buried in the sediment.
Softgrounds and soupgrounds typical.

Freshwater lakes, shallow lake
margins, glacial lakes, carbonate
lakes and freshwater delta
complexes.

Mermia

Permanently subaerially exposed
continental substrates characterized by
minimal deposition or erosion. Variable
pore moisture contents and
temperatures. Food deposited as
surface detritus or buried in the
sediment. Stiffgrounds to firmgrounds.

Paleosols of herbaceous (grass)
communities. Common to alluvial
floodplains, desiccated floodplains,
crevasse splays, levees,
abandoned point bars and
vegetated eolian environments.

Coprinisphaera

Warm, humid conditions with high water
tables. Abundant plant growth including
flank-buttressed trees.

Paleosols associated with closed
forest ecosystems.

Termitichnus

Warm to cold, arid conditions. Carbonate-rich, well-aerated

paleosols; palustrine settings and
calcretes.

Celliforma

Arid conditions, looseground mobile
substrates.

Eolian dune settings.

Octopodichnus-
Entradichnus

represent, instead, local variations in organism/sediment interactions that can be
accommodated by the established Seilacherian ichnofacies.
The post-depositional “ Arenicolites Ichnofacies” (cf. Bromley and Asgaard,
1991 ), for example, is well preserved in sandstone beds deposited under storm-
related high-energy environments of the lower to middle shoreface. The biotur-
bation is restricted to vertical burrows and is characterized by a low-diversity
assemblage of traces constructed by opportunistic organisms responding to an
open niche. Bromley and Asgaard (1991) concluded that such occurrences in
these storm deposits do not fall within the Skolithos Ichnofacies sensu stricto