Environmental Engineering Reference
In-Depth Information
TABLE 2
Expression of Ichnofacies Found in Fluvial Deposits—Cont'd
Ichnofacies
Description
Included ichnogenera
Implications
Skolithos
Vertical cylindrical burrows and more
rarely Y, or U-shaped vertical burrows.
Other associated trace-fossil types may
include bilobed burrows/trails,
horizontal burrows, simple horizontal
trails, and meniscate burrows. Common
monospecific or low-ichnodiversity
assemblages (maximum 4 trace-fossil
types). Dense ichnofabrics occur,
composed of vertical burrows.
Characteristic: Skolithos,
Polykladichnus, Arenicolites, “escape
traces”
Accessory: Cruziana, Archaeonassa
(
Cross-bedded to planar-laminated
sandstone and ripple cross laminated
sandstone and siltstone. Typically on top
of fluvial channel bars or crevasse splays.
Possible origins are subaerial exposure by
burrowing insects or colonization of
high-energy bars. Also developed on
sandy substrates of crevasse-splay origin.
Aulichnites), Palaeophycus,
Taenidium, Planolites
¼
Grallator
Dominantly bird tracks and bipedal,
tri- to tetradactyl tracks with thick digits
(B 3-4 tk). Other accessory trace-fossil
morphologies are (in order of abundance)
simple horizontal burrows, simple
burrows/trails, arthropod trackways,
bipedal tridactyl tracks with short stout
digits, burrow systems, meniscate
burrows, and a high variety of vertebrate
tracks. Commonly a mixture of tetrapod
tracks and invertebrate traces, where the
former are dominant. Medium-high
diversity ichnofaunas (5-8 trace-fossil
types) with bipedal tridactyl tracks
usually dominant.
Characteristic: Grallator, Anchisauripus,
Kayentapus, Eubrontes, Gruipeda,
Dinehichnus, Avipeda, Fuscinapeda,
Sarjeantopodus, Aquatilavipes,
Ignotormis, Barrosopus, Alaripeda
Accessory: Hadrosauropus, Anomoepus,
Parabrontopodus, Dicynodontipus,
Macrauchenichnus, Characichnos,
Palaeophycus, Planolites, Diplichnites,
Spongeliomorpha, Scoyenia, Taenidium,
Lockeia, Rusophycus
Cross-bedded sandstones, ripple
cross-laminated sandstones and
siltstones, massive to parallel-laminated
mudstones. Typically present on top of
exhumed fluvial bars, sandy crevasse
splays, or floodbasin ponds.
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