Ichnology of the Yeoman Formation 1
Rozalia Pak 2 and S. George Pemberton 2
Pak, R. and Pemberton, S.G. (2003): Ichnology of the Yeoman Formation; in Summary of Investigations 2003, Volume 1,
Saskatchewan Geological Survey, Sask. Industry Resources, Misc. Rep. 2003-4.1, CD-ROM, Paper A-3, 16p.
Abstract
The recognition and classification of trace fossils in carbonates of the Upper Ordovician Yeoman Formation in
southeastern Saskatchewan are hindered by the complex diagenetic history of these rocks. Since many primary
characteristics of deposits greatly influence diagenesis, the distinction between sedimentary and diagenetic fabrics
can be difficult. This problem presents itself clearly in an examination of the trace fossils of the Yeoman Formation,
which is characterized by conspicuous dolomite mottling. To date, it remains debatable whether these trace fossils
represent Thalassinoides or sediment dolomitization around smaller, causative burrows. Most ichnological studies
have been performed in clastics or chalks, and the methodology developed for these studies is difficult to apply to
similar research in Paleozoic platform carbonates. The purpose of this paper is to describe the trace fossils of the
Yeoman Formation, and to explore their potential usage in determining changes throughout the deposition of this
thick platform carbonate sequence.
In the examination of the biogenic sedimentary structures of the Yeoman Formation, nine discrete trace fossils are
observed, many being part of composite burrow systems. Except for Trypanites, Trichophycus, and Palaeophycus,
these trace fossils are indicative of feeding activities. Their diversity of form gives the impression of a diverse
benthic fauna, but the relatively uniform diameter of the feeding burrows suggests that a small group of organisms
may have been responsible for the various forms. These burrowing organisms shifted their feeding behaviours in
response to changes in paleoenvironmental conditions, such as water energy, depth, oxygenation, and nutrient
availability. The association of more complex feeding structures with the larger, vegetative-state, disseminated B
Gloeocapsomorpha prisca alginite indicates that harsher conditions, which accompany the algal blooms, forced
infauna to adapt their feeding behaviours.
Keywords: Upper Ordovician, Yeoman Formation, Red River Formation, Asterosoma, Rhizocorallium,
Thalassinoides, Trichophycus, composite burrows, biogenic sedimentary structures.
1. Introduction
The complex diagenetic history of carbonates of the Upper Ordovician Yeoman Formation in southeastern
Saskatchewan hampers the recognition and classification of contained trace fossils. Many primary characteristics of
deposits greatly influence diagenesis, commonly making distinction between sedimentary and diagenetic fabrics
difficult. An example of this problem is presented by the conspicuous dolomite mottling in rocks of the Yeoman
Formation: to date, whether the mottling represents Thalassinoides or sediment dolomitization around smaller,
causative burrows remains debatable. Most ichnological studies have been carried out in clastics or chalks
(Kennedy, 1975), sediments so different from Paleozoic platform carbonates that the methodology established for
them is commonly difficult to apply to the Yeoman strata. This paper describes the trace fossils of the Yeoman
Formation and explores their potential usage in determining changes throughout the deposition of this thick
platform carbonate. Although diverse feeding structures are represented in these sediments, it appears that the
benthic fauna was restricted, but capable of adapting behaviour to changes in sedimentation, water energy,
oxygenation, and nutrient supply.
2. Methods
Cores, thin sections, and UV light petrography were utilized in the stratigraphic, sedimentologic and diagenetic
analysis of the Yeoman Formation. Twenty-three wells (Pak et al., 2001) have been examined from the Midale
(Townships 6 and 7, Range 11W2), Tyvan (Township 13, Range 13W2), and Ceylon (Townships 5 and 6, Range
19-20W2) pools. Core was logged by identifying the biota, ichnology, and textural relationships in the rocks.
Textures were described using Dunham’s (1962) classification scheme with modifications by Embry and Klovan
1
2
This project is funded by Husky Oil Limited.
University of Alberta, Department of Earth and Atmospheric Sciences, Earth Sciences Building, Edmonton AB, T6G 2E3,
E-mail: [email protected].
Saskatchewan Geological Survey
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Summary of Investigations 2003, Volume 1
(1971). Fifteen of the wells were sampled for thin section, burrow fabric, and associated organic analysis. One
hundred and fifteen thin sections were injected with blue epoxy for porosity determination and stained with
Alizarin-Red S (Dickson, 1965) to differentiate calcite from dolomite. Subsequently, samples selected from
different trace fossil associations were prepared for examination of organic matter contained within burrows using
reflected light microscopy. These samples consisted of blocks measuring approximately 2 cm x 2 cm x 2 cm that
were set in an epoxy resin and then polished using increasingly finer grit sizes and finally a slurry of 0.05 µm
alumina suspended in water. A Zeiss Axioplan II microscope equipped with a 100 W UV light source was used for
maceral analysis. Samples were observed under water immersion objectives (40X Apochromat, NA = 1.2;
magnification range 400x to 1000x) using 365 nm excitation and 420 nm barrier-emission filter to optimize imaging
of kukersite microscopic constituents. Digital images were captured using a Zeiss Axiocam system and Zeiss Vision
software.
3. Recognizing and Classifying Trace Fossils in Carbonates Subject to Heavy Diagenesis
Trace fossil classification primarily focuses on morphology. Secondary considerations include such factors as
burrow lining, contrast between the burrow fill and matrix sediment, host sediment characteristics, and the nature of
grain packing. Many trace fossils were originally described in clastic sedimentary rocks, where the original nature
of the grains is much less influenced by recrystallization, replacement, and fabric-destructive diagenesis than in
carbonates, where diagenetic alteration can effectively mask original sedimentary fabrics and primary mineralogy.
Many trace fossils owe their preservation and distinctive features to diagenetic fabrics. Diagenesis, however, serves
to enhance their appearance only to a point, beyond which destructive processes of recrystallization, replacement
and, commonly, extensive dissolution take over, and burrows and all primary features fade from recognition.
Increased burrow densities, the absence of burrow linings and weak contrast between burrow fill and host sediment
can make the discernment of discrete trace fossils difficult (Fürsich, 1975). Preservation is also skewed toward the
latest and deepest “tier” of burrowing, which has the highest preservational potential (Bromley and Ekdale, 1986).
All things considered, the greatest limitation to examining the Yeoman trace fossils is the unavailability of data.
Core description rarely allows a 3D view of trace fossil morphology. Weathered exposures, which have provided
samples for many ichnological studies, are not available so the 3D shapes of the observed biogenic sedimentary
structures must be inferred from repeated patterns and direct observations in core, where the horizontal expression
of individual trace fossils is limited by core diameter. Bedding planes and contacts are rare in the Yeoman
Formation where the overlying and underlying sediments are similar, and it is most commonly only firmground and
hardground surfaces that are recognizable. Bedding plane recognition is also reduced by abundant pressure solution.
Stylolites and solution seams commonly form at contacts between differing substrates, thus preventing the
recognition of interface trace fossils, such as tracks and trails of benthic epifauna.
Taken together, the above factors not only make it difficult to accurately determine substrate controls, but also
hamper interpretation of the behaviour of the trace producer. Where the contrasting nature of the burrow fill and
matrix determine the feeding behaviour of the trace producing organisms (Kotake, 1989), diagenesis can destroy
this crucial information.
Yeoman trace fossils are classified keeping the foregoing limitations in mind along with the following factors.
Original fabrics are inferred by examining corresponding intervals. The zone least affected by diagenesis is taken to
most closely resemble original fabric and mineralogy. Locally, present-day fabrics proved to be useful, since rocks
of differing original mineralogy and fabrics may have undergone different diagenetic pathways. For example,
increased porosity or crystal size in a burrow fill may be indicative of a syndepositional contrast between the burrow
fill and the host matrix. Comparison with studies of other carbonates, especially age-equivalent rocks, is useful in
noting how other researchers dealt with these complications. Due to these various difficulties, trace fossils are
classified only at a generic level. Details required to identify them at species level are not readily available in this
core study.
Finally, it must be noted that, since freshly slabbed core surfaces and outcrops are not readily available, the more
distinct trace fossils may skew observations concerning trace-fossil assemblages and abundances. Where possible,
the trace-making behaviours are discussed in this paper as they are important in discussing the ecological
implications of trace-fossil associations
4. Palaeophycus and Planolites
These morphologically simple burrow types are discussed together for two reasons. First, they are the most
abundant in the Yeoman, commonly occurring together in all the different fabrics of the formation. Second, the
distinction between these two trace fossils has caused extensive debate even in examination of clastic sedimentary
rocks (Pemberton and Frey, 1982; Keighley and Pickerill, 1995).
Saskatchewan Geological Survey
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Summary of Investigations 2003, Volume 1
a) Description of Ichnogenus Palaeophycus Hall, 1847
Burrow orientation is mainly horizontal with minor subhorizontal to (sub)vertical components (similar vertical,
straight burrows that occur alone are classified as Skolithos). Burrows are straight to curved, and circular to
elliptical in cross-section (Figures 1 and 2). Their diameter is constant along the burrow axis and ranges from less
than 1 mm in some intervals to nearly 5 mm. Burrows are rarely branched, and the type of branching is not
discernible. They have regular, smooth external ornamentation. The organic-rich lining of the burrows appears to
have aided in both their preservation, which is generally good to excellent, and recognition. In intervals dominated
by Planolites and Palaeophycus, burrow linings, which vary in thickness and locally appear annulated, comprise a
variety of macerals (Gloeocapsomorpha prisca; spiny, acanthomorphic acritarchs; Leiosphaeridiai) and zooclasts
(scolecodonts and chitinizoans). In intervals that also contain Asterosoma, Rhizocorallium, and composite burrows,
however, the linings predominantly consist of G. prisca (notably the disseminated B G. prisca maceral variety sensu
Stasiuk and Osadetz, 1990), algal detrinite, and bitumen. Due to the lack of prepared samples, microfossils in the
linings were not closely examined. Palaeophycus generally has a homogeneous internal burrow fill that may be
recrystallized as saddle dolomite or coarser dolomite, or that may be dissolved, leaving the burrow core hollow. The
fill, where unaltered, is similar to the host rock. However, it is rarely nondolomitized. Interestingly, nondolomitized
Palaeophycus occurs in places amidst dolomitized Palaeophycus. Re-burrowing by Planolites is sometimes
observed. Burrow density depends on facies.
b) Discussion
Palaeophycus is distinguished from Planolites primarily by wall linings and the character of the burrow fills.
Although Palaeophycus is found in most of the Yeoman intervals, it is particularly abundant in those rich in
allochems but depleted in dispersed organic
matter/kerogen and mud. Infills of Palaeophycus
represent passive, gravity-induced sedimentation within
open, lined burrows (Pemberton and Frey, 1982),
although this cannot specifically be confirmed for
Yeoman Formation occurrences. Palaeophycus is
generally interpreted as the open dwelling burrows of
suspension feeding or carnivorous animals (Pemberton
and Frey, 1982). The presence of collapse structures and
geopetal fills in the Yeoman burrows supports this
interpretation. The primary objective in constructing
dwelling burrows is protection, so intervals dominated by
domichnia are thought to suggest well illuminated,
shallow-water deposits where predation is greatest. In
modern environments, dwelling burrows are generally
restricted to shallow, well illuminated intervals (Schäfer,
1972). Possible trace makers may be sipunculid,
enteropneust, or polychaete worms. Further examination
of scolecodonts in association with these burrows might
Figure 1 - Palaeophycus (Pa) with thin dolomitic diagenetic help identify the behaviour of the trace-making
haloes (Tri Link Tyvan 21/8-17-13-13W2, 2170.8 m).
organisms, since scolecodont shape reflects feeding
behaviour (e.g., predation vs. scraping). The presence of
scolecodonts is notable and merits further investigation as
scolecodonts, due to their sensitivity to diagenesis, are
rarely found in marine sediments with many trace fossils
(Schäfer, 1972).
c) Description of Ichnogenus Planolites
Nicholson, 1843
Figure 2 - Palaeophycus with dolomitic halo.
Photomicrograph taken under polarized light (Berkley et al
Midale 41/2-10-7-11W2, 2592.9 m).
Saskatchewan Geological Survey
Planolites is generally preserved as horizontal to
subhorizontal, straight to curved (in places, meandering)
intrastratal burrows (Figure 3), which are rarely branched,
but crosscut and interpenetrate each other. Burrows are
smooth walled and homogeneously filled. They rarely
exhibit a meniscus structure and may contain secondary
Planolites of equal or smaller diameter. Burrow diameter
ranges from less than 1 mm (discernible only
microscopically) to almost 10 mm and is unaltered by
branching. Cross-sections are circular to elliptical, the
latter resulting from compactional flattening or oblique
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Summary of Investigations 2003, Volume 1
Figure 3 - Planolites (Pl) with thin diagenetic haloes from a
dolomitized mudstone interval (Husky Ceylon 41/6-5-619W2, 2746.3 m).
sectioning of the burrow. Burrow thickness is generally
constant along the observed burrow length (absolute
lengths of burrows have not been determined). The fill
differs from host rock in that it generally contains less
dispersed organic matter and kerogen, but it may also be
dolomitized, or contain a different dolomite type than that
of the host rock. The fill may contain a contrast in
allochem abundance (greater or smaller) or the burrow
may contain oriented/structured allochems. These last few
criteria generally require thin sections for recognition.
Burrow density is dependent on facies, generally being
higher in muddier substrates.
d) Discussion
Planolites is found in all the Yeoman facies in variable
abundance, and may occur alone or as secondary burrows in Thalassinoides, Asterosoma, Rhizocorallium, or
Trichophycus. It may form monospecific assemblages or be in association with Chondrites. Planolites is
distinguished from Palaeophycus primarily by having unlined walls, and burrow fills that differ from the adjacent
rock in texture fabric, composition, and colour. These fills represent sediment processed by the trace maker,
especially through deposit-feeding activities of mobile endobionts (Pemberton and Frey, 1982). In the Yeoman
specimens, the local development of weak menisci further supports an active back-fill interpretation.
Interpenetrations and re-burrowed segments of Planolites are easily confused with true branching, which is
comparatively rare. Petrographic investigation is commonly required for identification, and that is not always
possible. Since the Planolites organism re-burrowed numerous other kinds of pre-existing traces, the latter
presumably contained enhanced nutrient levels such as dispersed organic matter and/or represented an easier path
for new burrowing activities. The first of these two possible causes for Planolites re-burrowing seems to be valid as
the fill of the last tier of burrows has the lowest content of organic matter. Planolites is generally interpreted to
represent deposit-feeding behaviour. Preservation of mucous linings is unlikely in sediments subject to such
extensive diagenesis as in the Yeoman Formation, so some burrows, due to an apparent lack of burrow lining, may
be incorrectly classified as Planolites.
e) Burrow Lining or Diagenetic Halo?
Central to the diagnosis of these forms is the presence or absence of wall linings (Pemberton and Frey, 1982).
Diagenetic haloes can readily be mistaken for linings in a megascopic examination, so thin sections may be required
to differentiate between the two. Burrow lining is indicated by a concentration of organic matter and/or bitumen,
evidence of spreite at burrow walls or, where there is a thick wall, by contrasting abundance of organic matter.
Increased porosity along burrow walls is taken to suggest a dissolved lining or mucous layer. A zone of “arranged”
allochems found around burrows commonly indicates a zone of deformation caused by the organism’s passing
through a semi-consolidated (plastic) substrate, rather than a burrow lining (Rhoads, 1970).
Diagenetic haloes are, in fact, very common in the Yeoman Formation and range from less than 1 mm to greater
than 10 mm in thickness. Most burrowing organisms, when moving through sediment, secrete some mucus or other
residue (Schäfer, 1972; Bromley, 1996). This mucus commonly acts as a catalyst for the formation of diagenetic
haloes. Keighley and Pickerill (1995) suggested that a burrow lining might be inferred if the diagenetic halo extends
from the burrow boundary into both the burrow fill and the host lining. In the Yeoman Formation, this criterion
failed to prove useful, as the fills of both lined and unlined burrows are commonly dolomitized.
f) Determining the Nature of Original Burrow Fill
The secondary ichnotaxobase is the burrow fill. In carbonate sedimentary rocks like those of the Yeoman
Formation, recognition of the burrow fill is problematic because the fill is diagenetically altered (difference of the
inferred burrow fill from the matrix at the time of sedimentation, not their present-day difference, must be used as
the ichnotaxonomic criterion). Where dissolution of the burrow core has occurred or dolomitization and
recrystallization have been fabric destructive, burrow fill can be misinterpreted, leading to incorrect classifications.
This approach to identification is viable only if the burrow fill and matrix presently reflect their primary textural
state.
g) Branching or Crosscutting Burrows?
The crosscutting of burrows can easily be confused with true branching. Evidence to truly distinguish branching
from crosscutting burrows may be enigmatic, and in some cases may not be interpretable (Keighley and Pickerill,
Saskatchewan Geological Survey
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Summary of Investigations 2003, Volume 1
1995). This holds true for the Yeoman Formation, where distinction between abundant Planolites and Chondrites is
often arbitrary.
5. Composite Burrow Systems
In ichnological studies, all biogenic sedimentary structures are commonly classified as discrete trace fossils. As
such, a false impression of a diverse benthic community may result. In many intervals of the Yeoman Formation,
composite burrow systems are identified which reflect a combination of organism behaviours, and classification as a
single burrow type is impossible. Discrete burrows, which in addition to Planolites and Palaeophycus are
commonly part of these systems, will be discussed in subsequent sections.
a) Description of Composite Burrows
These complex biogenic sedimentary structures are simply or multiply lined, anastomosing burrow systems, which
exhibit branching and crosscutting, evidence of U-shaped portions, spreite resulting from shifting of the burrow
system, as well as spreite in the burrow fill (Figures 4 and 5). The fill is generally dolomitized mudstone, so the
contrast between the host sediment and burrow fill may be a result only of diagenesis. The organic-rich linings may
be thin or up to several millimetres thick, and commonly resemble concentric linings of Cylindrichnus concentricus
described by Goldring (1996) and Fürsich (1974b). These linings mainly comprise organic matter that, where nondegraded, is dominantly made up of disseminated A and B G. prisca alginite (sensu Stasiuk and Osadetz, 1990).
Amorphous organic matter and algal detrinite are also common in burrow linings. Macerals and zooplankton seen in
Palaeophycus linings are rarely observed in these burrow linings. Other portions of the burrow systems exhibit
characteristics of Phycodes, Asterosoma, and Rhizocorallium (Figures 4 and 5). The burrow diameters of the
original and later burrows are similar and do not change with branching. Rarely, a larger diameter Planolites
crosscuts a smaller, lined burrow.
b) Discussion
The concentric linings are believed to have originated by the construction of a multi-layered wall whereby the
organism added successive walls pushing early-formed layers outwards (Aller and Yingst, 1978, in Goldring, 1996).
Of Goldring’s three hypotheses for formation of concentrically lined burrows, Aller and Yingst’s method seems
most applicable here because the material that lines the burrows is mostly planktonic, appears to have been
introduced into the burrow, and is absent from the matrix sediment. These complex feeding systems may have
initially served as the dwelling burrows of filter-feeding
or carnivorous organisms. Once the environmental
conditions changed, e.g., possibly less nutrient availability
in the water column, these organisms altered their
behaviour to exploit organic matter and organic detritus
they had used earlier to line their burrows. The last tier of
Planolites and/or Chondrites indicates deposit-feeding
activities. Because organisms are known to change their
feeding patterns diurnally and seasonally (Schäfer, 1972;
Hummel, 1985), other changes in environment are not
necessarily responsible for changes in feeding behaviour.
Figure 4 - Horizontal section through composite burrows in
the Yeoman Formation. Note repeated reworking of
sediment (Husky Ceylon 41/10-18-5-20W2, 2771.5 m).
Consistent burrow diameter throughout these systems
suggests that all the tiers of these burrows were created by
the same or similar organisms (Figure 5). Consequently,
although diverse feeding patterns are preserved, these
systems may have been produced by a single or small
group of organisms. The inference that the suspensionfeeding components of these composite burrows and other
suspension-feeding burrows described from the Yeoman
Formation were formed by a single species is consistent
with Turpaeva’s hypotheses (1957 in Walker, 1972)
concerning trophic relationships of benthic fauna. Based
on an examination of feeding ecology of modern benthic
animals, she believed that one trophic group that contains
the most prevalent species generally dominates a
community. This, she inferred, is characteristic of a stable
community in which the organisms attain a
noncompetitive feeding arrangement. These composite
burrows, which generally occur in intervals believed to
Saskatchewan Geological Survey
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Summary of Investigations 2003, Volume 1
coincide with G. prisca algal blooms (Kent and Haidl,
1999), presumably resulted from a species of polychaete
dominantly consuming this algal microfossil by a
suspension-feeding mechanism. When conditions for
successful filter feeding were interrupted, this worm-type
organism might have adapted to a deposit-feeding
behaviour that exploited the same algal microfossil that
was readily available in the sediment.
6. Thalassinoides
The characteristic dolomite mottling common in Lower
Paleozoic platform carbonates has often been interpreted
as large branching burrow networks of either the
ichnogenus Spongeliomorpha or Thalassinoides (Bottjer
et al., 1984; Zenger, 1992, 1996; Myrow, 1995; Zenger
and LeMone, 1995). This interpretation has been
favoured for the dolomite mottling of the Yeoman
Formation (Kendall, 1976, 1977; Canter, 1998; Kissling,
1999), although others believed that the mottling
represents dolomitic haloes, which formed around
Planolites, Palaeophycus, and Chondrites (Carroll, 1978;
Gingras, 2000). These two interpretations have different
implications on the origin of the burrows found in the
dolomite mottles. According to the former model, the
burrows are secondary, but the latter model infers they
are causative burrows, which facilitated dolomitization of
the matrix.
Due to this disparity in views regarding dolomite
mottling, the mottling in the Yeoman Formation required
close examination. According to Kendall (1977), three
features remain in question if the mottles are interpreted
as diagenetic haloes:
Figure 5 - Composite burrows with many Rhizocoralliumlike components. Diameters of various burrow types are
consistent, indicating that the same organism reworked
these sediments. Planolites burrows in matrix are only
faintly visible as their appearance is not enhanced by
bitumen staining. As, Asterosoma; Ch, Chondrites; Pa,
Palaeophycus; Pl, Planolites; Rh, Rhizocorallium; and Si,
Silica nodule (Berkley et al Midale 11/7-3-7-11W2,
2576.8 m).
Saskatchewan Geological Survey
1) The bimodal distribution of mottle diameters (either
uniformity or a wide range of mottle diameters would
be expected if the mottles represent diagenetic
alterations around burrow centres).
2) The otherwise uniformity in the size of dolomite
mottling throughout the thickness of the Yeoman–
lower Red River interval across the whole Williston
Basin (this uniformity suggests a burrow origin).
3) The mottles sometimes lack internal burrows, or they
contain more than one burrow or burrows that are
markedly eccentric (if dolomitization had proceeded
uniformly outward from the burrow centres to
generate cylindrical mottles, the mottles should
always contain centrally located burrows).
Gingras (2000), on the other hand, believed that, since the
dolomite mottles do not exhibit regular sharply
demarcated boundaries and constant burrow diameters
throughout the network, they did not represent biogenic
sedimentary structures. His study, however, focused on
the surface Tyndall Limestone that, although it can be
examined on a larger scale in outcrop, displays some
different sedimentary characteristics than the subsurface
Yeoman Formation.
Thalassinoides-like burrows have been found in many
Ordovician platform carbonates (Sheehan and
Schiefelbein, 1984). Although the biological affinities of
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Summary of Investigations 2003, Volume 1
the organisms responsible for these networks have not yet been discovered, it seems plausible that at least some of
the dolomite mottles in the Yeoman Formation represent Thalassinoides. Lack of Yeoman Formation outcrop
prevents a diagnosis based on plan geometry, i.e., determination of vertical and horizontal extent of these large
characteristically branching networks. The mottle networks found in outcrops of both the Tyndall Limestone and
Lower Yeoman (Red River) Formation (Figures 6 and 7) greatly resemble other recorded Lower Paleozoic
Thalassinoides (Sheehan and Schiefelbein, 1984; Watkins and Coorough, 1997). The proper taphonomic conditions
may not have existed to preserve Thalassinoides in an identifiable form. This, combined with diagenetic destruction
of many primary sedimentary structures, make the determination with absolute certainty of the presence of
Thalassinoides in the Yeoman Formation impossible.
a) Description of Thalassinoides Ehrenberg, 1944
Burrows are preserved intrastratally in vertical section. The orientation of their limbs is vertical and horizontal,
although locally some are inclined, or portions of some are inclined. These burrows exhibit both Y and T-shaped
branching with burrow diameter apparently remaining constant along branches. Burrows are generally straight or
slightly curved. Their cross-section is circular or elliptical. Burrow walls are smooth, regular and unlined, but
stylolites/pressure solution may in places give the appearance of thin organic-rich lining. Burrow fill is
homogeneous, but may contain secondary Planolites and Chondrites. It is commonly dolomitized, occasionally
silicified, and shows contrast in allochem abundance relative to the host rock. Burrow diameter ranges from 5 to
20 mm. Burrow length is indeterminable. The burrow density is variable from few discrete Thalassinoides to
Thalassinoides comprising about 50 percent of the rock volume. Thalassinoides generally has poor preservation or
recognition potential.
b) Collective Indicators of Thalassinoides in the
Yeoman Formation
Although no single criterion in itself can be used to
distinguish diagenetic haloes from burrows, a
combination of criteria points to favouring one
interpretation over another. In intervals where many of
the following criteria are met, mottles are interpreted as
Thalassinoides.
Figure 6 - Thalassinoides (Th) parallel to bedding plane
from outcrop of the lower Red River/Yeoman Formation.
Preferential growth of fungi indicates burrow patterns.
Located near Amisk Lake, Saskatchewan. Pencil 14 cm
long.
Figure 7 - Thalassinoides-like burrows indicated by
differential weathering of these dolomitized sediments and
patterns of fungi growth. Outcrop from western shore of
Amisk Lake, Saskatchewan. Pencil 14 cm long.
Saskatchewan Geological Survey
•
Dolomite mottles contain intraclasts made of the
same material as the matrix. Such occurrences, some
of which appear to represent collapse structures, are
rare. This is probably the best evidence that what are
now mottles were once open burrows. Note that the
walls of these mottles are not sharp (Figure 8).
•
Contrast in fabric, allochem abundance and types,
and abundance of organic matter between mottle and
matrix sediment. Since the dolomitization which
formed the mottling is generally fabric destructive,
an increased abundance or variety of allochems
within the burrow is in itself a valid criterion to
identify the structure as a burrow; however, the
inverse cannot be claimed with such certainty (Figure
9).
•
Absence of causative burrow from mottles over an
interval. Absence is only certain when the burrow is
seen in cross-section. An oblique section may miss
the causative burrow. Although causative burrows
may in places have been obliterated by the
dolomitization that formed the diagenetic mottle,
their widespread presence helps validate the
assumption that, where absent, they never initially
existed.
•
The mottle wall is cut by burrows (i.e., the mottles do
not strictly follow or completely contain smaller
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Summary of Investigations 2003, Volume 1
burrows), or the mottle wall crosscuts another
burrow (Figure 10).
•
Mottles generally have sharp walls; however this
criterion is not always the best (see discussion
below).
•
Large mottles and small Planolites exhibit the
same diagenetic fabrics and the walls of both have
the same “sharpness”.
•
Mottles exhibit Y- and T-branching, characteristic
of Thalassinoides (Figure 11).
•
Mottle diameter appears constant along the burrow
axis throughout an interval.
•
Mottles exhibit mechanical compaction and may in
places be “broken”, squashed, or flattened. The
presence of mechanically compacted mottles
suggests mottle formation occurred prior to
sediment lithification.
•
Re-burrowing by Planolites; the re-burrowing of
large burrows by deposit feeders is common,
especially where the fill of the large burrow may
provide a better food source for the later
burrowers (Bromley, 1996).
•
Mottle occurrence in intervals that contain
firmgrounds with Thalassinoides. This is merely
circumstantial evidence – if organisms existed that
were large enough to create Thalassinoides at the
firmground intervals, would they not have existed
before and after?
Figure 8 - Roof collapse as evidence of formerly open
burrow systems. H, molds of halite hopper crystals with void
filling saddle dolomite cement; Pa, Palaeophycus; Pl,
Planolites; and Th, Thalassinoides (Berkley et al Midale
31/11-34-6-11W2, 2606.2 m).
Figure 10 - Thalassinoides (Th) re-burrowed by
Palaeophycus (Pa), with Palaeophycus crosscutting
Thalassinoides wall (Husky Ceylon 41/10-18-5-20W2,
2778.6 m).
Figure 9 - Wackestone fill of Thalassinoides (Th) in a
mudstone matrix (Husky Ceylon 11/5-8-6-19W2, 2713.3 m).
Saskatchewan Geological Survey
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Summary of Investigations 2003, Volume 1
Figure 11 - Thalassinoides (Th) with Y-shaped branching in
the horizontal plane. Re-burrowed by Planolites (Pl). Note
Palaeophycus (Pa) without diagenetic haloes (Husky
Ceylon 11/5-8-6-19W2, 2719.2 m).
One of the criteria noted by Bromley (1996) and cited by
Gingras (2000) to determine if a structure is a burrow or
not is the presence of a regular, sharply demarcated
boundary. Here, this criterion is regarded to be
insufficient evidence for differentiating between a
diagenetic fabric and biogenic sedimentary structures
because many indisputable Planolites have walls that are
not sharp as they have apparently been obscured by
dolomitization. If the dolomitization process can ‘blur’ a
Planolites wall, it should also be able to obscure a
Thalassinoides wall. Furthermore, some of the mottles
containing intraclasts did not have sharp walls. Lack of
burrow wall sharpness may also result from factors other
than diagenetic blurring. If the biogenic sedimentary
structures were formed in a soupy or soft substrate, and
little evidence is preserved to suggest that the precursor
was a coarser grain texture, mechanical compaction of the
mottles can blur the walls of large Planolites or
Thalassinoides. Added evidence in these intervals
indicating that the mottles formed before sediment
lithification is the presence of molds after halite hoppers
that must have developed in a void space or in sediment
soft enough for them to displace material as they grew.
These hopper crystals, now infilled with saddle dolomite
or, less commonly, anhydrite, are frequently (but not
exclusively) found in dolomite mottles that fit the other
criteria for Thalassinoides.
c) Collective Indicators of Diagenetic Haloes in the Yeoman Formation
The following criteria, when found together within an interval, are here taken to collectively favour a diagenetic
halo interpretation.
•
No crosscutting observed between smaller burrows and the dolomite mottles over the interval.
•
Contrast between mottle and matrix at the outer boundary of the halo is gradational petrographically, and in
abundance of allochems and organic matter (Figure 12).
•
Dolomitization of the halo appears fabric destructive, and allochems are faintly preserved or gradually decrease
in abundance towards the causative burrow.
•
Diagenetic front of the dolomite halo terminates against a macrofossil, but in other places continues farther
from the causative burrow.
•
Palaeophycus burrows, when not centrally located
within dolomite mottles, may be causative structures
with diagenetic haloes.
•
Mottles do not exhibit much mechanical compaction
(i.e., no squashed mottles over an interval).
The distinction between Thalassinoides and diagenetic
haloes remains locally uncertain, especially in intervals
that are intensively affected by diagenesis. In nodular
zones and stylo-mottled zones, the 3D configuration is
impossible to determine. Stylolites have further
obliterated the nature of the mottle walls. The origin of
many nodular and rubbly textures in limestones and
dolostones has been attributed to burrowing (Fürsich,
1972), so these textures in the Yeoman may, in places,
have originated as large burrow systems that are now
impossible to distinguish.
Saskatchewan Geological Survey
Figure 12 - Dolomitic diagenetic haloes commonly form
around Palaeophycus and Planolites. Polarized light (Husky
Ceylon 11/5-8-6-19W2, 2710.0 m).
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Summary of Investigations 2003, Volume 1
d) Discussion
Those burrows identifiable with greatest certainty as Thalassinoides generally occur in the same carbonate intervals
that contain kukersites. Thalassinoides is common at the firmground contacts between carbonate and superjacent
kukersite. Many burrows are re-burrowed by Planolites. Some examples of Thalassinoides are found in other
Yeoman intervals. Thalassinoides most likely represents the fodinichnia and domichnia of arthropods or large
worms. Phyllopods were suggested by Bottjer et al. (1984). Thalassinoides burrows are generally interpreted as
dwelling or combined feeding/dwelling structures. The interpretation generally applied to Thalassinoides behaviour
cannot be applied because the arthropods (e.g., shrimps) responsible for making these burrows had not yet evolved
in the Ordovician. Until a possible trace producer is identified, the Lower Paleozoic Thalassinoides may remain an
enigma (Myrow, 1995). No organism has been observed
in any Thalassinoides burrow, and until an example is
found the trace maker cannot be identified with certainty
(it may never be found if the trace was produced by a
soft-bodied organism with very low preservation
potential).
The Lower Paleozoic dolomite mottling with diffuse
dolomite walls may represent burrows formed in
thixotropic sediment. Although the walls of these mottles
resemble diagenetic fronts, they also fit criteria listed by
Rhoads (1970) for burrows formed in a soupy
(thixotropic) substrate. It may be possible that some
unknown animal of Lower Paleozoic age mined the
sediment prior to any dewatering and lithification, and
that the fill of its burrows was more susceptible to
dolomitization. The burrow walls remained blurry due to
lack of substrate consistency.
7. Chondrites
a) Description of Chondrites Sternberg, 1833
Burrows are smooth-walled and are found in vertical and
horizontal section (Figure 13). Branches are subvertical to
horizontal; however, some zones are dominated by
horizontal burrows. Locally, the branching is dendritic,
but generally the orders and nature of branching are
indeterminable. Cross-sections are elliptical to circular
and range from less than 1 mm to 3 mm in diameter. The
internal sediment is homogeneous, and through its
paucity of organic matter/kerogen, generally contrasts
with the matrix sediment (though locally Chondrites has
fill that is richer in organic matter/kerogen than the
matrix, see Figure 14). Preservation of these burrows
ranges from good to poor.
Figure 13 - Chondrites (Ch) in an organic-rich mudstone
(kukersite) (Berkley et al Midale 41/2-10-7-11W2,
2576.5 m).
b) Discussion
Chondrites is common in muddy, organic-rich substrates,
and as secondary burrows of Thalassinoides and
composite burrows systems. It is also common in organicrich kukersites. Chondrites burrows may occur
exclusively with Planolites, or as part of a composite
burrow system. They are generally interpreted as
fodinichnia, but despite their common occurrence in
sediments throughout the Phanerozoic, the trace maker
has not yet been identified. The vertical upper portions,
suggested by Kotake (1991) to be domichnia, are not
observed. Chondrites indicates a lack of oxygenation of
the substrate only when occurring as a monospecific suite
(Bromley and Ekdale, 1984). However, since it
commonly occurs as the deepest tier of trace fossils
(Bromley and Ekdale, 1986), it may appear to be a
Saskatchewan Geological Survey
10
Figure 14 - Chondrites (Ch) with fills rich in organic
matter (dominantly Gloeocapsomorpha prisca alginite) (Tri
Link Tyvan 21/8-17-13-13W2, 2165.0 m; scale bar is 1 cm).
Summary of Investigations 2003, Volume 1
monospecific suite because its high density has obliterated all other burrows. Chondrites is found alone in some, but
not all, kukersites. The trace-making organism may have colonized the substrate after the deposition of the
kukersite, so Chondrites does not necessarily indicate a low-oxygen environment for kukersite deposition.
8. Trichophycus
a) Description of Ichnogenus Trichophycus
Miller and Dyer, 1878
Burrows are found in subhorizontal to horizontal section
(Figure 15). Trichophycus generally occurs as straight
burrows that are circular to elliptical in cross-section and
have diameters which range from one to several
centimetres (one observed chamber had a diameter of
10 cm) and which locally vary along burrow axes. There
is little evidence of branching. Walls are irregular, locally
containing ridges or grooves, which suggest scratchmarks. Stylolites and bitumen concentrated at burrow
walls give the impression of thin organic-rich lining.
Burrow fill is homogeneous, and, partly through having a
higher organic content, distinctly differs from the host
rock. Usually dolomitized, the fill commonly contains
secondary Planolites and Chondrites whose fills have
lower organic contents. Allochems are better preserved
and occur in greater variety than in the host sediment. The
fill is richer in bryozoans, trilobites, and ostracods.
Burrow preservation is excellent due to lithologic contrast
and to high organic content of the fill.
b) Discussion
The contrast between Trichophycus fill and the host
matrix may be due to better preservation in the sheltered
burrow environment. Alternatively, the burrow fills may
represent remnants of an eroded bed. Trichophycus
burrows were interpreted by Seilacher and Crimes (1969)
to be feeding structures of small trilobites. In this study,
trilobites large enough to build Trichophycus of the size
observed in core have not been observed in Yeoman
rocks. These burrows are distinguished from
Thalassinoides by their lack of branching. Furthermore,
their sharp walls and distinctive nature suggest a different
origin than that of Yeoman Formation Thalassinoides.
Figure 15 - Horizontal section through Trichophycus (Tri)
(Berkley et al Midale 11/7-3-7-11W2, 2613.4 m).
9. Skolithos
a) Description of Ichnogenus Skolithos
Haldeman, 1840
Skolithos burrows are vertical or subvertical (Figure 16)
and are intrastratally preserved. Diameters range from 1
to 3 mm. They are generally straight, but are locally
curved. They are several centimetres in length, but their
overall length cannot be ascertained. Two types of
Skolithos are observed. The first is lined by allochems
and is visible only on freshly slabbed surfaces. The
second type is more common and generally more visible
due to organic matter in its fills and linings. Burrow fills
are found to be the same as the host sediment except for
those that are lined with organic matter, which are
commonly dolomitized.
Saskatchewan Geological Survey
Figure 16 - Skolithos (Sk) in the Yeoman Formation
(Berkley et al Midale 41/2-10-7-11W2, 2575.2 m).
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Summary of Investigations 2003, Volume 1
b) Discussion
The presence of Skolithos indicates enough water agitation on a regular basis for filter-feeding organisms to
colonize the substrate. They are rare and are generally found in association with Palaeophycus. They are thought to
be the vertical dwelling tubes of polychaetes; however, vertical-tube components of many other trace fossils may be
mistaken for Skolithos in core analysis.
10. Rhizocorallium
a) Description of Ichnogenus Rhizocorallium Zenker, 1836
Rhizocorallium burrows are preserved intrastratally and occur vertically to horizontally in random orientations
throughout given intervals (Figure 17). The U-shaped burrows show no evidence of branching except where they
are associated with composite burrow systems. Diameters are from 1 to 5 mm, and the lining thickness ranges from
5 µm to several millimetres. The burrow length is indeterminable. Their lining generally has much greater organic
content than the host sediment, and exhibits spreiten. If the organic matter is not degraded, it is dominantly
disseminated A and B G. prisca alginite. The internal sediment of the latest burrow is generally carbonate with low
organic content. The burrow fill may contrast in both
mineralogy and organic content with the host matrix.
Rhizocorallium may contain secondary Planolites or
Chondrites. It is occasionally observed in kukersitic
intervals (Figure 17) where fill is depleted in organic
matter. Burrow density is variable, but these sediments
are never fully bioturbated by Rhizocorallium.
b) Discussion
Rhizocorallium burrows have been interpreted to
represent both suspension- and deposit-feeding activities.
R. jenense, represented by more or less straight, short,
and commonly oblique spreiten burrows, is interpreted as
dwelling burrows of filter feeders (Fürsich, 1974a). The
abundance of G. prisca in burrow linings, combined with
its absence in burrow fills and host matrix, suggests that
the organisms incorporated these maceral varieties into
the burrow lining. This further suggests that
Rhizocorallium was produced by filter-feeding or surface
detritus-feeding behaviour.
11. Asterosoma
a) Description of Ichnogenus Asterosoma von
Otto, 1854
Asterosoma-like structures are found in both horizontal
cut and vertical section. They are preserved intrastratally
(Figure 18). They are commonly associated with
composite burrow systems. Their orientation is horizontal
to subhorizontal; no related vertical shafts are observed.
They are curved, bulbous burrows with lobes. No
evidence of branching is found. Burrow diameter in
cross-section ranges from 1 to 6 mm. It is variable along
the burrow length, which, in turn, is often indeterminable
due to lobe curvature. Walls are annulated, containing
several concentric layers of organic matter. If the organic
matter is not degraded, it is dominantly disseminated A
and B G. prisca alginite. The internal fill usually consists
of low organic content carbonate sediment (Figure 19),
sometimes with meniscate structures. Carbonate fill is
commonly dolomitized, as is the carbonate component of
the burrow lining. Preservation of lobes is good, and the
ability to recognize them is enhanced by their organic
lining.
Saskatchewan Geological Survey
12
Figure 17 - Rhizocorallium (Rh) in organic-rich mudstones
(kukersites) indicative of deposit-feeding behaviours. Some
Asterosoma (As)-like behaviour is also indicated by these
biogenic sedimentary structures. Their fill is devoid of
organic matter. Abundant spreite indicate repeated
reworking and probing of the sediment. Nature of contact
has been destroyed by pressure solution. Palaeophycus (Pa)
in carbonate sediment below contains the same type of
organic matter as that within the matrix of the kukersite
(Husky Ceylon 11/5-8-6-19W2, 2710.0 m).
Summary of Investigations 2003, Volume 1
Figure 18 - Asterosoma (As), Palaeophycus (Pa), and
Planolites (Pl). Asterosoma and Palaeophycus contain
abundant organic matter within their linings, but the fill of
Planolites is devoid of organic matter (Tri Link Tyvan 21/817-13-13W2, 2157.4 m).
b) Discussion
In horizontal section, evidence of multiple bulbs is
limited to two. Vertical sections are, however, indicative
of Asterosoma-type behaviour. Generally these are part of
composite burrow systems, which also exhibit other
similar feeding behaviours. Farrow (1966) found that
present-day Asterosoma burrows occur in finer, more
argillaceous sediments deposited farther from the
shoreline. Although he inferred that they might be of
either crustacean or annelid origin, Asterosoma are
generally considered to be the feeding (fodinichnia)
structures of worms. The organism is believed to have
probed repeatedly into the sediment to enlarge the gallery
and work more and more sediment vertically and laterally
(Chamberlain, 1971). Asterosoma found in kukersites is
apparently formed by this mechanism (Figures 17 and
19). However, Asterosoma-like components of composite
burrow systems, where they are not secondary burrows
that exploited the linings of earlier burrows, are thought
to have resulted from waste-stowage type behaviours
(Bromley, 1991; Kotake, 1991).
12. Trypanites
Figure 19 - Asterosoma (As) as a secondary burrow within a
Trypanites (Try) at the hardground base of an organic-rich
mudstone (kukersite). Borings also contain secondary
Planolites (Pl) and lithoclasts (L). Lithoclasts suggest that
the sediment was cemented prior to deposition of the
organic-rich mudstone (Berkley et al Midale 21/11-35-611W2, 2584.8 m; scale bar is 1 cm).
a) Description of Ichnogenus Trypanites Mägdefrau, 1932
Trypanites borings are preserved across stratal contacts (Figures 19 and 20). They are visible as ‘piped’ zones,
introducing sediment from an overlying layer into an underlying layer, most commonly at the base of kukersitic
intervals (Figure 19). They have, however, also been observed at the upper surface of a kukersite bed and between
two adjacent carbonate layers. Their fill therefore contrasts to that of the host rock, so burrows lying between
kukersite and carbonate sediment are the most easily recognized. The internal sediment is homogeneous except for
common secondary burrows of Asterosoma, Planolites, or Chondrites that are evident from the contrastingly lower
organic content of their fill. Trypanites borings have vertical openings and may remain vertical, or curve to a
horizontal chamber. They range in length from one centimetre to indeterminable. The borings are rarely branched
and commonly have lobate or bulbous shapes. Boring diameter, which ranges from a couple of millimetres to more
than one centimetre, generally changes if the burrow is branched. Walls are generally sharp and appear to be
smooth. Preservation is excellent except where stylolites have formed along the hardground and have destroyed the
contact. In such occurrences, a hardground is commonly inferred from the presence of Trypanites in the carbonate
sediment underlying the stylolitic contact.
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Summary of Investigations 2003, Volume 1
b) Discussion
Figure 20 - Trypanites (Try) containing lithoclasts.
Sediment filling the boring is slightly richer in organic
matter (Berkley et al Hume N 41/7-2-9-13W2, 2444.4 m).
Most commonly Trypanites occurs below kukersites, but
burrows have been observed between adjacent carbonate
beds. Where contacts have been destroyed by pressure
solution, their former presence is inferred from borings
found below a thick stylolite, rich in organic matter and
kerogen. Thin sections are commonly required to
differentiate Trypanites from Thalassinoides at a
firmground. Commonly no evidence (e.g., sutured
allochems and cut fabrics) can be found to determine
whether the substrate was cemented or not at the time of
formation of these biogenic sedimentary structures. A
possible hypothesis for the development of these
“borings” is as burrows at omission surfaces. Palmer
(1978) suggested that sediment around burrows became
lithified while the burrows remained open, and the surface
subsequently became a hardground during sediment
bypassing. This hypothesis, suggesting that these are preomission suites burrows (Bromley, 1975), may explain
the presence of Thalassinoides-type burrow morphologies
observed at hardgrounds. Further evidence for this
hypothesis is the absence of encrusting organisms on
many of these hardground surfaces. Sea-floor conditions
at time of cementation were possibly adverse to
encrusting fauna – for example, sea-floor anoxia may
have existed when organic-rich kukersites were deposited
over hardgrounds.
13. Conclusions
Description and classification of trace fossils in the Yeoman Formation are necessary as they are related to the most
conspicuous characteristic of these sediments, namely, the dolomite mottles. Their presence has important
implications on both sedimentology and diagenesis. Detailed examination of the dolomite mottles indicates that
many indeed represent Thalassinoides, but until the trace-making organism is identified, this will remain debatable.
In this examination of the biogenic sedimentary structures of the Yeoman Formation, nine discrete trace fossils have
been observed, many being part of composite burrow systems. Except Trypanites, Trichophycus, and Palaeophycus,
they are indicative of feeding activities. The diversity of forms gives the impression of a diverse benthic fauna. The
relatively uniform diameter of the feeding burrows suggests that a small group of organisms may have been
responsible for the various forms. These burrowing organisms shifted their feeding behaviour in response to
changes in paleoenvironmental conditions, such as water energy, depth, oxygenation, and nutrient availability. The
association of more complex feeding structures with the larger, vegetative-state, disseminated B G. prisca alginite
indicates that harsher conditions, which accompany the algal blooms, forced infauna to adapt their feeding
behaviours.
14. Acknowledgments
Personnel at Saskatchewan Industry and Resources, Subsurface Geological Laboratory in Regina, were of great
assistance in core logging and the collection of samples. I am grateful to Kim Dunn (GSC, Calgary) for preparing
samples for UV microscopy, and to L.D. Stasiuk (GSC Calgary) for help in logging organic matter contained within
burrow linings. Members of the Ichnology Research Group, University of Alberta, are greatly thanked for
discussion of ideas, especially Eric Hanson and Tom Saunders for editing and insightful comments on this paper.
15. References
Bottjer, D.J., Sheehan, P.M., Miller, M.F., Byers, C.W., and Hicks, D.O. (1984): Thalassinoides in the Paleozoic;
Geol. Soc. Amer. Bull., Abstr. with Prog., v16, p451.
Bromley, R.G. (1975): Trace fossils at omission surfaces; in Frey, R.W. (ed.), The Study of Trace Fossils, SpringerVerlag, New York, p399-428.
__________ (1991): Zoophycos: Strip mine, refuse dump, cache or sewage farm?; Lethaia, v24, p460-462.
Saskatchewan Geological Survey
14
Summary of Investigations 2003, Volume 1
__________ (1996): Trace Fossils, Biology and Taphonomy; 2nd Edition, Unwyn Hyman, London, 280p.
Bromley, R.G. and Ekdale, A.A. (1984): Chondrites: Composite ichnofabrics and tiering in burrows; Sci., v123,
p59-65.
__________ (1986): Composite ichnofabrics and tiering in burrows; Geol. Mag., v123, p59-65.
Canter, K.L. (1998): Facies, cyclostratigraphic and secondary diagenetic controls on reservoir distribution,
Ordovician Red River Formation, Midale Field, southern Saskatchewan; in Eighth International Williston Basin
Symposium, Proceedings of a Symposium, Core Workshop Volume 8, Regina, Sask. Geol. Soc./N. Dakota
Geol. Soc./Mont. Geol. Soc., p41-65.
Carroll, W.K. (1978): Depositional and paragenetic controls on porosity development, Upper Red River Formation,
North Dakota; in The Economic Geology of the Williston Basin, Williston Basin Symposium, Mont. Geol.
Soc., 24th Annual Conference, p79-94.
Chamberlain, C.K. (1971): Morphology and ethology of trace fossils from the Ouachita Mountains, southeast
Oklahoma; J. Paleont., v45, p212-246.
Dickson, J.A.D. (1965): A modified staining technique for carbonates in thin section; Nat., v205, p587.
Dunham, R.J. (1962): Classification of carbonate rocks according to their depositional texture; in Hamm, W.E.
(ed.), Classification of Carbonate Rocks, Amer. Assoc. Petrol. Geol., Denver, p108-121.
Embry, A.F. and Klovan, J.E. (1971): A late Devonian reef tract on northeastern Banks Island, NWT; Bull. Can.
Petrol. Geol., v19, p730-781.
Farrow, G.E. (1966): Bathymetric zonation of Jurassic trace fossils; Palaeogeog., Palaeoclim., Palaeoecol., v2,
p103-151.
Fürsich, F.T. (1972): Thalassinoides and the origin of nodular limestone in the Corallian Beds (Upper Jurassic) of
Southern England; N. Jb. Geol. Paläont. Mh., H.3, p.136-156.
__________ (1974a): Ichnogenus Rhizocorallium; Paläont. Z., v48, ½, Stuttgart, p16-28.
__________ (1974b): Corallian (Upper Jurassic) trace fossils from England and Normandy; Stuttgarter Beiträge zur
Naturkunde B, v13, p1-52.
__________ (1975): Trace fossils as environmental indicators in the Corallian of England and Normandy; Lethaia,
v8, p151-172.
Gingras, M.K. (2000): Applications in ichnology and sedimentology; unpubl. Ph.D. thesis, Univ. Alberta, 245p.
Goldring, R. (1996): The sedimentological significance of concentrically laminated burrows form Lower Cretaceous
CA-bentonites, Oxfordshire; J. Geol. Soc., London, v153, p225-263.
Hummel, H. (1985): Food intake of Macoma balthica (Mollusca) in relation to seasonal changes in its potential
food on a tidal flat in the Dutch Wadden Sea; Nether. J. Sea Resear., v19, p52-76.
Keighley, D.G. and Pickerill, R.K. (1995): “Commentary”, The ichnotaxa Palaeophycus and Planolites: Historical
perspectives and recommendations; Ichnos, v3, p301-309.
Kendall, A.C. (1976): The Ordovician Carbonate Succession (Bighorn Group) of Southeastern Saskatchewan; Sask.
Dep. Miner. Resour., Rep. 180, 186p.
__________ (1977): Origin of dolomite mottling in Ordovician limestones from Saskatchewan and Manitoba; Bull.
Can. Petrol. Geol., v25, p480-504.
Kennedy, W.J. (1975): Trace Fossils in Carbonate Rocks; in Frey, R.W. (ed.), The Study of Trace Fossils, SpringerVerlag, New York, p377-398.
Kent, D.M. and Haidl, F.M. (1999): Depositional environments and reservoir potential of Lower and Middle
Paleozoic rocks of Saskatchewan; Can. Soc. Petrol. Geol., Annual National Conference Short Course Notes,
52p.
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Kissling, D.L. (1999): Life and Death Roles of the Red River Thalassinoides; Amer. Assoc. Petrol. Geol. Bull., v87,
p1184.
Kotake, N. (1989): Paleoecology of the Zoophycos producers; Lethaia, v22, p327-341.
__________ (1991): Packing process for the filling material in Chondrites; Ichnos, v1, p277-285.
Myrow, P.M. (1995): Thalassinoides and the enigma of early Paleozoic open-framework burrow systems; Palaios,
v10, p58-74.
Pak, R., Pemberton, S.G., and Gingras, M.K. (2001): Reservoir characterization of burrow-mottled carbonates: The
Yeoman Formation of southern Saskatchewan – preliminary report; in Summary of Investigations 2001,
Volume 1, Saskatchewan Geological Survey, Sask. Energy Mines, Misc. Rep. 2001-4.1, p10-13.
Palmer, T.J. (1978): Burrows at certain omission surfaces in the Middle Ordovician of the Upper Mississippi
Valley; J. Paleont., v52, p109-117.
Pemberton, S.G. and Frey, R.W. (1982): Trace fossil nomenclature and the Planolites-Palaeophycus dilemma; J.
Paleont., v56, p843-881.
Rhoads, D.C. (1970): Mass properties, stability and ecology of marine muds relating to burrow activity; in Crimes,
T.P. and Harper, J.C. (eds.), Trace Fossils, Geol. J., Spec. Issue No. 3, p137-148.
Schäfer, W. (1972): Ecology and palaeoecology of marine environments (translated from the German: Aktuopaläontologie nach Studien in der Nordsee, by Irmgard Oertel); Oliver and Boyd, Edinburgh, 568p.
Seilacher, A. and Crimes, T.P. (1969): “European” species of trilobite burrows in eastern Newfoundland; in North
Atlantic - Geology and Continental Drift; Amer. Assoc. Petrol. Geol., Mem. 12, p145-148.
Sheehan, P.M. and Schiefelbein, D.R.J. (1984): The trace fossil Thalassinoides from the Upper Ordovician of
Eastern Great Basin: Deep burrowing in the early Paleozoic; J. Paleont., v58, p440-447.
Stasiuk, L.D. and Osadetz, K.G. (1990): The life cycle and phyletic affinity of Gloeocapsomorpha prisca Zalessky
1917 from Ordovician rocks in Canadian Williston Basin; in Current Research, Part D, Geol. Surv. Can., Pap.
89-1D, p123-137.
Walker, K.R. (1972): Trophic Analysis: A method for studying the function of ancient communities; J. Paleont.,
v46, p82-93.
Watkins, R. and Coorough, P.J. (1997): Silurian Thalassinoides in an offshore carbonate community, Wisconsin,
USA; Palaeogeog., Palaeoclim., Palaeoecol., v129, p109-117.
Zenger, D.H. (1992): Burrowing and dolomitization patterns in the Steampoint Member, Bighorn Dolomite (Upper
Ordovician), northwest Wyoming; Contributions to Geology, University of Wyoming, v29, p133-142.
__________ (1996): Dolomitization patterns in widespread “Bighorn Facies” (Upper Ordovician), Western Craton;
Carb. Evap., v11, p219-225.
Zenger, D.H. and LeMone, D.V. (1995): Widespread “Bighorn Facies”, Upper Ordovician, North America; in
Cooper, J.D., Droser, M.L., and Finney, S.C. (eds.), Ordovician Odyssey, short papers for the 7th International
Symposium on the Ordovician System, Soc. Sed. Geol. (Pacific Section), Book 77, p389-392.
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