Walker J. Facies models, Canada, 1992

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Teredolites

ichnofacies

The Teredolites ichnofacies consists

of a characteristic assemblage of

bor-

ings in woody (xylic) substrates. These

differ from

lithic substrates in three

main ways (Bromley et al., 1984);

they may be flexible instead of rigid, 2)

they are composed of combustible

material instead of mineral matter, and

they are readily biodegradable.

Woodgrounds may appear in fresh-

water settings such as logjams in

fluvial cutoffs, and freshwater ichno-

coenoses consist principally of isopod

and allied borings. Because wood sub-

strates can be moved by currents, it is

important to determine whether the

borings are autochthonous (Arua,

1989) or allochthonous (Dewey and

Keady, 1987). Only the autochthonous

forms are true members of the

Teredolites

ichnofacies. These assem-

blages may also be important in

defining sequence and parasequence

boundaries.

The traces are characterized by

sparse to profuse clavate (club-shaped)

borings, 2) dense excavations, but

without interpenetrating borings, 3)

walls ornamented with the texture of

the host substrate

(e.g., tree ring im-

pressions),

stumpy to elongate sub-

cylindrical, subparallel excavations in

marine or marginal marine settings, 5)

shallower, sparse to profuse nonclavate

etchings (isopod borings) in freshwater

settings.

EVALUATION OF

THE

NINE RECURRING

ICHNOFACIES MODELS

These archetypal models, particularly

the marine ones, have proven to be

valuable in characterizing general envi-

ronmental conditions. In many cases,

physical sedimentary structures cannot

be used to distinguish environments

for example, the structures of fluvial

point bars may be very similar to those

of estuarine point bars. However, the

two settings can easily be distin-

guished because the biogenic sedi-

mentary structures are very different.

Perhaps the most misunderstood

aspect of these recurrent ichnofacies

their use in paleobathymetry.

Although some workers have been

complacent regarding this aspect of

environmental reconstruction (as dis-

cussed by Frey et

a/.,

1990), other ich-

nologists have long and persistently

4. TRACE FOSSILS

emphasized that local sets of environ-

mental factors are most important in

controlling the distribution of

trace-

makers, whether or not these parame-

ters occur at specific water depths. For

instance, many estuarine point bars

exhibit a high-energy, channelward

side typified by a

Skolithos association

and a low-energy

bankward side

typified by a Cruziana association

(Howard and Frey, 1985). The respec-

tive associations occur in close prox-

imity, at the same stratigraphic or

bathymetric level.

However, many environmental pa-

rameters do tend to change progres-

sively with water depth and distance

from shore

(e.g., grain size, energy lev-

els, suspended food, water turbidity),

and these gradients effect corre-

sponding changes in the distribution of

physical and biogenic

sedimentary

structures (Fig. 2). To that extent, trace

fossil associations are indeed useful in

paleobathymetry.

The long temporal duration of most

kinds of trace fossils is very impor-

tant. These basic benthic behavioral

patterns are more nearly like stable

ecologic niches than individualistic

records of particular animal species

(Frey and Seilacher, 1980, p.

202-

203). As long as the functional niche

remains advantageous under given

environmental conditions, many dif-

ferent animal species, over long inter-

vals of geological time, may be

expected to exploit it. Their preserved

traces are strikingly similar and have

equivalent significance. Hence, al-

though we conveniently and infor-

mally speak of the "Skolithos animal"

as the architect for a particular kind of

dwelling structure, numerous different

animal species actually were involved

(i.e., many biological species construct

the same type of burrow). The

longevity of recurrent ichnofacies

thereby exceeds the longevity of re-

current biofacies by a considerable

margin. Such ichnofacies are more

useful as archetypal models not only

for environmental interpretation but

also for comparisons of depositional

environments of widely differing ages.

These recurrent ichnofacies have

been designated as archetypal facies

models, with which particular local

ich-

nofacies can be compared. The arche-

types are intended to supplement, not

supplant, local ichnofacies

designa-

tions, some of which are quite distinc-

tive; corresponding ichnofaunas may

be restricted (Serna,

1986), intergrada-

tional (Marintsch and Finks, 1982), or

diverse (Dam, 1990).

The idealized ichnofacies succession

(Fig. 2) works well in most "normal" situ-

ations (Frey and Pemberton, 1984, their

fig. 5), including salinity gradients

(Bromley and Asgaard, 1991). How-

ever, nearshore assemblages can be

found in offshore sediments, and vice

versa, if the particular sediments accu-

mulated under conditions preferred by

the tracemaking organisms. The basic

controls are not physical constraints

such as water depth, distance from

shore, or some particular tectonic or

physiographic setting. Rather, they

involve substrate consistency, hydraulic

energy, rates of deposition, turbidity,

oxygen and salinity levels, toxic sub-

stances, the quality and quantity of

available food, and the ecologic or

ich-

nologic prowess of tracemakers them-

selves

(Vossler and Pemberton, 1988a).

Finally, the models should not be di-

vorced from associated patterns of

bio-

turbation. Numerous local ichnofacies,

particularly those representing

low-

energy conditions and slow rates of de-

position, are set in a totally bioturbated

texture (Fig. 13). Several generations of

burrows may be discernible via their

cross-cutting relationships, showing that

the same volume of sediment passed

repeatedly through various styles of re-

working. In environmental recon-

struction, such ichnologic fabrics may

be equally as important as the indi-

vidual, named trace fossils (Pemberton

and Frey, 1984; Howard and Frey,

1984).

PALEOENVIRONMENTAL

SIGNIFICANCE OF ICHNOFOSSILS

The application of ichnology to paleo-

environmental analysis goes far beyond

the mere establishment of general re-

curring ichnofacies. For instance,

shallow water coastal marine environ-

ments (Chapters 9, 10,

12) consist

of many smaller sedimentological

regimes characterized by large fluctua-

tions in many physical and chemical

parameters. In order to comprehend

fully the depositional history of such

regimes, it is necessary to have reliable

means of differentiating subtle changes

in these physical and chemical parame-

ters. Physical sedimentary structures

58 PEMBERTON, MACEACHERN, FREY

definitely help, but biogenic sedimen-

tary structures can better delineate eco-

logical parameters such as oxy-

genation, salinity, and energy levels. An

example is given by

Dijrjes and

Hertweck

(1975), who subdivided the

coastal zone into three major environ-

ments, based primarily on the position

of mean high water, mean low water,

and wave base. Their faunistic investi-

gations also confirmed the importance

of minimum and maximum wave base

as distinct boundaries separating

animal communities (Fig. 5).

ICHNOLOGIC APPLICATIONS

ALLOSTRATIGRAPHY

Allostratigraphy (Chapter

is based

on the recognition of units that can be

defined by their bounding discontinu-

ities. Many discontinuities are marked

by major lithological changes (Figs. 2

and

in Chapter I), but other equally

important discontinuities may have a

very subtle expression. It is here that

trace fossils and trace fossil suites

(along with all other available

sedi-

mentological, stratigraphic and paleon-

Figure

Complex bioturbate textures in

chalk. Textures progress from obscure

background mottling to increasingly sharp,

tological information) can be em-

ployed effectively, both to aid in the

recognition of various types of discon-

tinuities and to assist in their genetic

interpretation.

RECOGNITION AND

INTERPRETATION OF

DISCONTINUITIES USING

ICHNOLOGY

It is a commonly held belief that

sharp breaks in the vertical strati-

graphic record may signify fundamental

changes in the depositional environ-

ment and initiation of new cycles of

sedimentation. However, many facies

contacts are sharp, despite the super-

posed facies being at least somewhat

genetically related. The emplacement

of sandy storm beds in the offshore

transition zone, for example, yields

abrupt basal contacts with the

fair-

weather silty shales, but clearly reflects

a penecontemporaneous relationship.

Despite an erosional relationship, the

absence of a significant temporal break

indicates that such

contacts probably

do not have allostratigraphic signifi-

cance.

In contrast, gradational facies con-

tacts are generally regarded to imply a

more gradual shift in depositional con-

ditions. Nonetheless, intense bur-

rowing, for example, can destroy

erosion surfaces through biogenic ho-

mogenization, making the contact

between two superposed facies

appear to be gradational. The pres-

ence of dispersed pebbles or rip-up

clasts may be the only preserved evi-

dence of such

surface, and such evi-

dence must be sought carefully when

logging core or measuring outcrop

sections. The action of organisms

within the substrate may serve to

either enhance or obscure breaks in

the stratigraphic succession. In this

chapter, we are primarily concerned

with the ichnological characteristics

which serve to enhance the recogni-

tion and interpretation of discontinu-

ities.

lchnology may be employed to

resolve breaks in the section in two

main ways. The first is by recognition

of substrate-controlled ichnofacies,

which mark time gaps between the

original deposition of a unit (with or

without softground burrowing) and later

superimposition of a postdepositional

trace assemblage. The second is

through careful analysis of vertical

ichno-

logic successions analogous to facies

successions (Chapter

1).

Vertical

changes in ichnological character which

may

reflect fundamental changes in de-

positional setting include changes in 1)

interpreted organism

behaviour (e.g.,

feeding strategy, dwelling style), 2) trace

fossil diversity, reflecting environmental

stresses such as decreased salinity, in-

creased water turbidity, and reduced

well-preserved burrows. Cross cutting rela-

tions within these chalks reveal as many as

Figure

Trace fossil association characteristic of the Glossifungites ichnofacies.

tiers of traces. Demopolis Chalk, Upper

1) Thalassinoides or Spongeliornorpha,

Gastrochaenolites or related ichnogenera,

Cretaceous, Alabama. Scale bar

cm.

Skolithos or Trypanites-like structures,

Diplocraterion, 5) Psilonichnus,

Arenicolites,

Adapted from Frey and Bromley l(985.)

Rhizocoralliurn. Modified from Frey and Pemberton (1984).

oxygenation, and 3) ichnofossil abun-

dance. Integrating the data derived from

substrate-controlled ichnofacies with

data from vertical ichnologic successions

provides a powerful tool for the recogni-

tion and interpretation of discontinuities.

Discontinuities

All breaks in the stratigraphic record are

important but may not have allostrati-

graphic importance. Allostratigraphic

4. TRACE FOSSILS

boundaries typically correspond to fun-

damental shifts in the depositional

systems, related to

allocyclic controls.

Such bounding discontinuities are re-

gional in extent and correspond to sig-

nificant temporal breaks, aspects that

require careful stratigraphic,

sedimento-

logical, biostratigraphic, paleomagnetic,

andlor radiometric analysis.

Three major types of discontinuity

commonly regarded to have allostrati-

Trypanites lchnofacies

Not to

scale

Figure

Trace fossil association characteristic of the

Trypanites

ichnofacies.

echinoid

grooves, unnamed,

Rogeralla,

Entobia,

Trypanites,

Gastrochaenolites,

Trypanites,

polychaete boring, unnamed. Adapted from Frey and Pemberton

984).

Figure

Trace fossil association characteristic of the

Teredolites

ichnofacies. Adapted

from Bromley

et a/.

(1 984).

graphic significance will be consid-

ered,

erosional discontinuities,

nondepositional hiatuses,

and 3)

de-

positional discontinuities.

The

ero-

sional discontinuities

include lowstand

incised valleys, incised submarine

canyons, regressive surfaces of erosion

(forced regressions, Chapter

12), trans-

gressive surfaces of erosion

(ravine-

ment surfaces), and coplanar surfaces

lowstand erosion and transgressive

ravinement

(E/T

surfaces in the

Cardium Formation,

Plint

et al.,

1986).

Nondepositional hiatuses

correspond

to diastems or nonsequences. They

reflect cessation of deposition, with

minimal or no erosion; they may be

manifest by submarine firmgrounds or

hardgrounds.

Depositional discontinu-

ities

are unusually thin intervals of

slow but continuous accumulation.

They include condensed sections,

which are thin deposits reflecting long

spans of time, such that underlying

facies successions are fundamentally

unrelated to overlying successions.

Marine flooding surfaces can also

be depositional discontinuities, in as

much as they represent abrupt deep-

ening with minimal or no development

of intermediate facies due to insuf-

ficient time for "normal" environmental

response to the changing conditions. It

is emphasized that both condensed

sections and marine flooding surfaces

form important stratigraphic discontinu-

ities, despite the fact that there has

been no actual removal of strata nor

cessation of deposition.

Substrate-controlled ichnofacies

Three substrate-controlled ichnofacies

have been established (Ekdale

et al.,

1984),

Glossifungites

(firmground, Figs.

14,

17A,

B),

Trypanites

(hardground,

Figs. 15,

17C), and

Teredolites

(wood-

ground, Figs. 16, 17D; Table 2). In

clastic settings, most of these trace as-

semblages are associated with erosion-

ally exhumed (dewatered and com-

pacted or cemented) substrates and

therefore correspond to erosional dis-

continuities. Woodgrounds consist of

xylic clasts or interwoven mats of vege-

tation, forming resilient substrates that

are not necessarily erosionally ex-

humed. In carbonate settings,

firm-

ground or hardground surfaces may

occur at the sediment-water interface,

due either to erosional exhumation or

nondepositional breaks with

associ-

60 PEMBERTON, MACEACHERN, FREY

ated submarine cementation (Bromley,

1975). Depositional breaks, in particular

condensed sections, may also be

semilithified or lithified

(Loutit et al.,

1988), presumably at the upper

contact. A condensed section may be

colonized without erosion, and the

upper surface may subsequently form a

downlap surface (Chapter 1). In gen-

eral, however, the recognition of sub-

strate-controlled ichnofacies may be

regarded as equivalent to the recogni-

tion of discontinuities in the strati-

graphic record.

Although certain insect and animal

burrows in the terrestrial realm may be

properly regarded as firmground suites

(Fursich and Mayr, 1981) or more rarely,

hardground suites, they have a low

preservation potential and constitute a

relatively minor component in the geo-

logical record of such associations. The

overwhelming majority of these

firm-

ground assemblage faunas form in

marine or marginal-marine settings. A

discontinuity may be generated in either

subaerial or submarine settings, but col-

onization of the surface may be re-

garded as marine influenced, particularly

in pre-Tertiary rocks. This has important

implications regarding the genetic inter-

pretation of the discontinuity.

The substrate-controlled

ichno-

coenose typically cross cuts a pre-ex-

isting softground suite. It therefore

reflects conditions postdating both

initial deposition of the unit and its

subsequent erosion (Fig. 17). The

suite also corresponds to a hiatus

between the erosion event (which

exhumes the substrate) and deposi-

tion of the overlying unit. During this

time gap, the substrate is colonized by

organisms. By studying

1) the soft-

ground ichnofacies (contemporaneous

with deposition of the unit),

the ich-

nofacies associated with the exhumed

substrate, and

the ichnofacies of the

overlying unit, it is possible to make

some interpretation regarding the origin

of the surface and the

allocyclic or auto-

cyclic mechanisms responsible.

EROSIONAL DISCONTINUITIES

There are numerous examples in the

ancient record of ichnologically demar-

cated erosional discontinuities (Table

2),

many of which have allostratigraphic

significance. These discontinuities in-

clude

lowstand unconformities, trans-

gressive surfaces of erosion, and

amalgamated

lowstand erosion and

transgressive surfaces.

Figure

Substrate-controlled ichnofacies. A) Glossifungites ichnofacies consisting of Skolithos and

?Arenicolites/Diplocraterion

pene-

trating a sideritized shale. The firmground suite cross-cuts offshore shales containing Helminthopsis, Terebellina,

Planolites, and Chondrites.

Pebbly fill has been piped down from the overlying conglomerate. Albian Viking Formation, Gilby A Field, Alberta. B) Glossifungites ichnofa-

cies consisting of Rhizocorallium excavated into offshore shales and cross cutting a resident softground suite of Helminthopsis, Planolites,

Terebellina, Chondrites, and Zoophycos. The firmground suite marks the base of an incised valley fill. Albian Viking Formation, Willesden

Green Field, Alberta.

Trypanites ichnofacies consisting of Trypanites weisei from the SilurianIDevonian disconformity (Bois BlancIBertie

-+-rn

Ontario. D) Teredolites ichnofacies consisting of borings into slightly coalified wood. The medium to coarse sand fill is

-n, Wabasca area, Alberta.

--_.__

2_____.-

Lowstand unconformities

Subaerial exposure and/or erosion pro-

duced during a

lowstand of relative sea

level permits the widespread develop-

ment of dewatered and firm or ce-

mented substrates. Such surfaces may

initially be mantled by a thin veneer of

nonmarine deposits, although their

pre-

servational potential is low. In any case,

unless the exhumed surface is exposed

to marine or marginal marine conditions

prior to final burial, it will not become

colonized by tracemakers of the

Glossifungites, Trypanites

Teredo-

lites

ichnofacies.

In the exceptional case of subma-

rine canyons, the erosional disconti-

nuity lies within a marine setting at the

time of its development, and coloniza-

tion of the walls and floor has a much

higher probability than those in terres-

trial valleys. Outcrops of the Lower

Miocene Nihotupu and Tirikohua for-

mations in Northland, New

Zealand,

contain a noteworthy substrate-con-

trolled trace fossil association

(Hayward, 1976; Fig. 18; Table

2).

The

underlying Nihotupu Formation con-

sists of largely unburrowed

mud-

TRACE FOSSILS 6 1

stones, sandstones and subaqueous

mass flow conglomerates (all of vol-

canic origin), together with submarine

piles of pillow lavas. lchnofossils are

rare, but solitary burrows and bur-

rowed horizons, including

Thalas-

sinoides, Planolites,

and

Scalarituba,

occur locally. Sediments of the Niho-

tupu Formation are interpreted to have

been deposited as turbidites at bathyal

water depths (based on faunal con-

tent) within an

interarc basin on the

lower eastern flanks of the west

Northland volcanic arc.

The contact with the overlying

Tirikohua Formation is sharp and ero-

sional, and exhibits visible relief. The

exhumed substrate contains a Glossi-

fungites assemblage of burrows, con-

sisting of

Skolithos

(called

Tigillites

the original author),

Rhizocorallium,

and

Thalassinoides.

Mechanical bor-

ing~ are absent, indicating that the

surface was not lithified at the time of

colonization. Steep trench walls with

small overhangs demonstrate that un-

derlying sediments were stiff and

semi-

consolidated at the time of coloniza-

tion by tracemakers of the

Glossi-

..........................................................................................

...........................................................................................

.........................................................................................

.~.~.~.~.~.~.~.~.~.~.~.~.~.~

............................................................

.........................................................................................

..........................................................................................

.........

......................................................................

........

.........

, ,

Sk0/ithOS

..........................................................................................................................................

.........

.........................................

........

.................................................................................

..................................................................

................

.......................

..................

.........................................................................

....................................

Skolithos

--.

0.0

0.5m

Figure

Submarine canyon wall ichnocoenose at Tirikohua Point, New Zealand. The

Miocene Nihotupu Formation consists of volcanogenic

clastics deposited as turbidites in

bathyal water depths in an inner-arc basin.

submarine canyon is incised into these sedi-

ments as a result

elf

a relative fall in sea level and is marked by a substrate-controlled ichno-

coenose. The presence of the Glossifungites ichnofacies, as well as the steep trench walls

having small overhangs, attest to semiconsolidated underlying sediments at the time of colo-

nization. The Tirikohua Formation corresponds to canyon floor deposits and neritic sediment

gravity flows, which filled the submarine canyon during an ensuing transgression. Modified

after

Hayward

976).

fungites

suite (Fig. 18). The overlying

Tirikohua Formation consists of fairly

coarse-grained volcaniclastics (sand-

stones and conglomerates), deposited

as canyon floor and neritic sediment

gravity flows, similar to proximal

tur-

bidites. The sediments contain a sparse

trace suite consisting of

Planolites,

Scalarituba, Skolithos, Thalassinoides,

and escape traces. Hayward (1976) in-

terpreted the erosional discontinuity as

a submarine canyon, excavated into

bathyal to neritic

interarc sediment

gravity flow deposits due to tectonic

uplift of the basin margin

(e.g., relative

lowering of sea level). Colonization of

the canyon walls by the firmground

tracemakers preceded eventual burial

by canyon floor and neritic turbidite de-

posits of the Tirikohua Formation,

probably corresponding to late stage

relative sea level

lowstand or early

transgressive fill of the submarine

canyon.

Within terrestrial incised valleys,

colonization of the discontinuity may

occur during

lowstand conditions at the

seaward (estuarine) end of the valley.

In this case, the distribution of sub-

strate-controlled ichnofacies can be

used to map the maximum marine limit

within the valley. Alternatively, coloniza-

tion of the valley walls and floor may

not occur until an ensuing transgressive

event. Under these conditions, initial

lowstand deposits are removed during

the transgression, exposing the

uncon-

formity to marginal marine conditions.

Transgressively related estuarine de-

posits are ultimately laid down on the

substrate-controlled trace suite as the

valley fills. Whether a substrate-con-

trolled trace fossil suite at the base of a

valley fill represents the

marginal-

marine portion of the valley during low-

stand or later transgressively related fill

is a problem to be resolved through

stratigraphic, sedimentological, and pa-

leontologic analysis.

Lowstand unconformities

examples from the

Viking Formation

The Lower Cretaceous (Albian) Viking

Formation of Alberta contains an

excellent example of subaerial erosion

(valley incision) and subsequent estu-

arine colonization. The subsurface

Crystal field (Figs. 19,

20)

consists of a

linear sandstone body up to

m thick,

generally interpreted to be some form

PEMBERTON, MACEACHERN, FREY

Table

lchnologically Demarcated Erosional Discontinuity Surfaces. The table outlines outcrop and subsurface examples of substrate-controlled

ichnofacies and the interpreted allostratigraphic significance of the demarcated discontinuity. Most omission suite traces are referable to the

Glossifungites

ichnofacies, but some are referable to the

Trypanites

Teredolites

ichnofacies. WCSB refers to the Western Canada Sedimentary

Basin.

ACE

LOCATION IF OR MAT ION^

PRE-EROSION TRACE

SUITEIEROSION

SURFACE TRACE SUITE

I I I

Ordovician

.................

Sil-Dev

unconformity

.................

Jurassic

(Pliensbachian

.................

Cretaceous

(L.

Albian)

..................

Cretacwus

(U.

Albian)

Cretaceous

(U.

Albian)

Cretaceous

(U.

Albian)

Cretaceous

(U.

Albian)

..................

Cretaceous

(Cenomanian)

Michigan

Basin

U.S.A.

Ontario

Canada

East

Greenland

................

WCSB

B.C.

Glenwood Fm

(subsurface)

..................

Bertiemois

Blanc Fm

contact

(outcrap)

...................

Kap Stewart/

Neill

Klinter

Fm contact

(outcrop)

...................

Gethind

Bluesky Fm

contact

(subsurface)

.................

WCSB

Jofh Field

Alberta

................

WCSB

Kaybob Field

Alberta

.................

Viking Fm

(subsurface)

.................

Viking Fm

(subsurface)

Cretacwus

(Turonian)

..........................................

Bertie Fm dolomites with

Thalassinoides.

Dark,

phosphatic silt-bearing

shale; no visible trace fossils.

Karsted surface bored by tracemakers of

the

Trypanires

assemblage, consisting of

Trypanites weisei

Garirochaenolites.

Glossifwrgites

assemblage consisting of

robust

Thalassinoides.

Unburrowed and rooted deltaplain

sandstones and coals.

WCSB Viking Fm Intensely burrowed muddy

Glossifungites

assemblage consisting of

Crystal Field (subsurface) sandstone with

Helminthopsis, Diplocraterion

shafts.

Alberta

Terebellina, Chondrites, Planolites

Asterosoma

rare

Zoophycos.

.........................................................................................

Glossifungites

assemblage consisting of

abundant

Diplocraterion parallelum.

Pebble lag is present.

Unburrowed, finely laminated and

rooted mudstones and

coals

(Gething Fm).

(subsurface)

Terebellina, Asterosoma

dispersed pebbles.

Planolites.

...........................................................................................

Glossifungites

assemblage consisting of

Skolithos

and

Thalassinoides

with

associated pebble lag.

Cretaceous

(Maastrichtian

WCSB Dunvegan Fm

Jayar Field (subsurface)

Alberta

..................

cretaceous-

Tertiary

contact

.................

........................................

Silty shales

distal storm sands

with

Planolites, Hehinthopsis,

Chondrites, Terebellina,

rare

Zoophycos, Asterosoma

Rhizocorallium.

........................................

Intensely burrowed sandy shale

with

Teichichnus, Helminthopsis,

Planolites, Zoophycos, Chondrites

Asterosoma,Terebellina

rare

Rosselia

Rhizocorallium.

Largely unbumwed and locally

rooted mudstones

shallow water

(lacustrine?) and deltaplain settings

.................................................

Glossifungites

assemblage consisting of

Skolithos, ?Arenicolites/Diplocraterion

and

Thalassinoides

with associated

pebble lag.

Glossifungites

assemblage consisting of

Thalassinoides

systems.

Pembina Fie1

Alberta

Drumheller

Alberta

wcsB

..................................................

Glossifungites

assemblage consisting of

Thalarsinoides

and

Skolithos

with

associated rip-up

clasts and pebbles.

...................

................................................

Cardium Fm

(subsurface)

Horseshoe

Canyon Fm

(outcrop)

Tertiarv

~irilc~hu~~~

-Nhotupu

Largely unburrowed

thin

bedded

]

~lo~mi~ygit~s

i~~~~-~~ed

----LA_

..-_

Silty shales with

Helminthopsis,

Planolites, Chondrites, Terebellina

and rare

Zoophycos,

reflecting a

distal

Cruziana

ichnofacies.

...........................................................................................................

Alabama

U.S.A.

Glossifungites

ichnofacies consisting of

Thalassinoides.

Unburrowed and rooted shales and

coals formed

within

a backbanier

setting.

Teredolites

assemblage consisting of

abundant

Diplocraterion parallelurn

subtending into a backbamer coal.

...........................................................................................................................

Prarie Bluff1 Burrowed (ichnogenera not

Clayton Fm disclosed) fossiliferous chalk

(cf

Frey and Bromley,

1985).

............................................................................................................................

Vertical

Thalassinoides paradoxicus

Spongeliomorpha

system of the

Glossifungites

assemblage.

TRACE

FOSSILS

Table

cont'd.

POST-EROSION TRACE SUITE

Inttnsely burrowed coarsening-upward cycle

of sandstone

shale

with

a shallow water

suite of

Teichichnus, Asterosoma, Planolites,

small

Terebellina

rare

Chondrites.

Oriskany sandstone of the Bois Blanc Fm is

unburrowed.

Poorly-sorted, medium to very coarse, massive

to cross-bedded sandstone

with

Diplocraterion,

Ophiomorpha, Gyrochorte, Monocraterion

Rhizocoralliwn.

Bar margin: intensely burrowed shaly sands

with

Rosselia, Helminthopsist Asterosoma,

Pdaeophycur. Teichichnus, Planolites

Terebellina.

Brackish pro-delta: interbedded

sands

shales with

Teichichnus, Planolites

Palaeophycus.

Sparsely burrowed, cross-bedded pebbly and

coarse sandstone with

ripup clasts. Mud

drapes

contain

Planolites.

Trough and low angle parallel laminated

sandstone containing

Arenicolites, Skolithos,

Ophiomorpha, Teichichnus,

Palaeophycus,

Helminthopsis, Chondrites, Rosselia,

Planolites, Terebellina

and

Asterosomo,

reflecting a middle shoreface setting.

Sandstones,

interbedded sands and shales, and

shales with

Teichichnus, Ophiomorpha,

Palaeophycus, Diplocraterion, Terebellina,

Planolites, Skolithos, Asterosoma

Rosselia.

Pebbly shale. intensely burrowed, with

Helminrhopsis, Zoophycos

and

Chondrites,

grading into less burrowed sandstone

shale

with

Asterosoma, Planolites

and

Chondrites.

Medium grained sandstones, intensely

burrowed, with

Ophiomorpha

(transgressive

sheet sand), passing into marine shales with

Zoophycos, Planolites

and

Chondrites.

Largely unbunowed conglomerate, overlain by

marine shale with dispersed pebbles; shales

contain

Helrninthopsis, Planolites, Chondrites,

Terebellina

and

Zoophycos.

Low angle parallel laminated

(HCS

and SCS)

sandstone with

Ophiomorpha, Rhizocordlim,

Teichichnus, Conichnus, Skolithos

Rosselia

in a storm-dominated lower shoreface setting.

Sandy

glauwnitic marls with reworked

Cretaceous fossils, thoroughly

burrowed;

nplete with

Thalassinoides suevicus.

Coarse-grained volcanogenic sandstone

(Tirikohua Fm)

similar

to proximal turbidites;

sparse suite of

Skolithos, Planolites,

Scalarituba, Thalassinoides

and escape traces.

INTERPRETATION OF SURFACE

Lower facies reflects a condensed section

(R.

Dott Jr.,

Nadon and

Rodrigues

Miranda, pers. comm., 1991). possibly

with

submarine

cementation.

shallowing event, probably accompanied by erosion

(rip-up

clasts within burrow fill) may indicate lowered relative sea level.

................................................................................................................................................

Bede Fm reflects final stages of marine regression. Diswnformity at top

represents shallowing and subaerial exposure. Transgression permitted

wlonisation and boring of

ElfT

surface, followed by Oriskany sandstone

deposition

(Pemberton

et al.,

1980).

................................................................................................................................................

The contact

intcrpxcted

a transgressive omission surface

flravinement), separating Sinemurian deltaplain deposits from overlying

barred shoreline sediments (Dam, 1990).

...............................................................................................................................................

Subaerial exposure and progradation of coal-bearing deltaplain sediments,

followed by transgressive ravinement (amalgamated

E/r

surface).

Colonisation of the erosion surface preceded main transgressive lag

deposition. Overlying facies reflect

prograding bar margin or brackish

water pro-delta deposits of the next progradational cycle (Oppelt. 1988).

................................................................................................................................................

Erosion surface cut into offshore deposits during lowstand of relative sea

level, sharply overlain by middle or lower shoreface sandstones. Reflects

basinward shift of

lowstand shoreface or

final

shoreface position due to

transgressive shoreface retreat (Downing and Walker, 1988).

................................................................................................................................................

Surface is an erosional unwnforrnity (generated by lowstand of relative

sea level) incised into underlying

offshorelinner shelf deposits.

Roximally. an

abmpt basinward shift of the shoreline ("fod

regression") resulted in deposition of directly overlying middle shoreface

deposits. Distally, shoreface

progradation produced a coarsening-upward

lower to middle shoreface cycle.

................................................................................................................................................

The surface is interpreted to reflect an incised valley. generated during a.

lowstand of relative sea level. The surface is incised into underlying shelf

to lower shoreface deposits. Overlying valley fill is part of an estuarine

tidal-channel complex

(Reinson

et d.,

1988).

................................................................................................................................................

The surface is interpreted to reflect transgressive ravinement associated

with continued (stepwise?) Colorado Sea advance. Underlying

transgressively reworked deposits reflect slightly more proximal

conditions

than

the immediately overlying sediments.

................................................................................................................................................

Deltaplain facies capped by subaerial exposure surface, reflecting a

lowstand of relative sea level. Transgressive surface of erosion was cut,

and reworking of underlying facies produced an overlying transgressive

sheet sand, passing into marine shale (Bhattacharya and

Walker. 1991).

................................................................................................................................................

'Ihe

surface may reflect erosion due to a lowstand of relative sea level

followed by shoreface progradation

(Plint

et al..

1988) or nwinement

(initial transgression) followed by stillstand shoreface progradation.

capped by shales of aresumed transgression

(cf.

Walker. 1990).

...............................................................................................................................................

The erosion surface is interpreted to reflect transgressive ravinement,

separating

backbanier deposits from overlying prograding storm-

dominated shoreface deposits (Saunders and Pemberton, 1986).

................................................................................................................................................

Prarie Bluff Chalk was subaerially exposed and locally incised by valleys

during a

lowstand of relative

sea

level. Subsequent transgression with

ravinement permitted colonisation of the

J2/T

surface (Savrda, 1991).

................................................................................................................................................

The surface reflects submarine canyon incision into deep water clastics in

response to tectonic uplift of an inter-arc basin margin. Canyon walls are

intensely burrowed by the

Glossificngites

suite. The surface is overlain by

canyon floor sediment gravity flow deposits

(Hayward, 1976).

PEMBERTON, MACEACHERN, FREY

LITHOLOG SYMBOLS

LITHOLOGIC ACCESSORIES ICHNOLOGIC SYMBOLS

......

Sand Laminae

k k

root traces Zoophycos

----

---

Shale or Mud Laminae

Diplocraterion

Rhizocorallium

Carbonaceous Mud Laminae

Arenicolites Rosselia

Coal Laminae

Skolithos

Jhalassinddes

-----

Carbonaceous Detritus

Ophiomorpha Cylindrichnus

Pebbles or Granules

Macaronichnus

Chondrites

--I.

RipUp Clasts

escape trace

Asterosoma

Wood

Fragment

Jerebellina

Planolites

Glauconite

Bergauena

Palaeophycus

Sid

Siderite

Teichichnus

Conichnus

~tk

Lithic

Glossifungites

U\n

Helminthopsis

Pyrite

lchnofacies

SEDIMENTARY STRUCTURES

Trough Cross-Bedding

=sz

Low Angle Curvilinear Lamination

///

Planar Tabular Cross Bedding

Biohrrbated (Mottled)

Combined Flow Ripples

Syneresis Cracks

Oscillation Ripples

Coarsening Upwards

Low Angle Planar Lamination

Fining Upwards

LITHOLOGY

Sandstone Sandy Shale

shat

sanktone

Interbedded Sandstone

- -

Shale

and

Conglomerate

..-

-..

Silty Shale

---

I)(]

~ost ~ore

BURROWABUNDANCE

BEDDING CONTACTS

Abundant

Sharp, Flat common

*sssssSs

Bioturbated

----

Uncommon

Uncertain

sparse

......

YMII~

Gradational

..,.

Scoured, Undulatory

Absent

Figure

Symbols used in strip logs of Figures 20, 22 and 25.

Figure

Strip log of a cored interval of the Viking Formation (Albian) in the Crystal Field,

south-central Alberta (symbols explained in Fig.

19).

Facies interpretations are listed on the

right-hand side of the log; key surfaces are marked on the left. The section shows an incised

valley, excavated into offshore deposits during a relative

lowstand of sea level. The incision

surface is marked by a Glossifungites assemblage consisting of Diplocraterion. The valley fill

is a heterolithic succession of sandstones, interbedded sandstones and shales, and shales

deposited in estuarine to marine settings during a relative rise in sea level. The valley fill is

capped by a transgressive lag, suggesting ravinement, followed by shelfal deposition of

shales.

Bumper

Al.

Crystal

08-26-45-04~5

GRAIN

SIZE

---

TRACE FOSSILS

of estuary filling

(Reinson

et al.,

1988).

Beneath the basal incision of the

valley, the older silty shales contain a

diverse softground

Cruziana

suite of

abundant

Terebellina, Chondrites,

Planolites, Helrninthopsis, Asterosorna,

and rare

Zoophycos

(Fig. 21A). At the

erosional truncation, a large number of

sharp-walled, unlined

Diplocraterion

shafts, constituting the

Glossifungites

assemblage (Fig. 21B), extend down-

ward into the underlying facies and

cross cut the original softground suite.

Elsewhere, the

Glossifungites

suite

consists of firmground

Gastrochae-

nolites.

The overlying estuary-fill facies

consists of a heterolithic association of

sandstones and shales. A low-diversity

suite of

Skolithos

and

Planolites

(Fig.

21C) with associated syneresis cracks

occurs near the base, and reflects

brackish water conditions. This associa-

tion passes into more fully marine

suites, consisting of

Ophiornorpha,

Teichichnus,

small

Rosselia, Astero-

soma, Diplocraterion, Skolithos,

Planolites, Palaeophycus,

and escape

traces. The erosion surface is inter-

preted as an incised valley, excavated

into underlying lower to upper offshore

deposits during a relative lowering of

sea level. The overlying heterolithic

facies succession was interpreted by

Reinson

et a/.

(1988) as multistage

tidal channel-fill within a larger estu-

arine channel-bay complex, which ac-

cumulated in response to an ensuing

period of transgression.

The base of a similar incised valley

in the Viking Formation at Willesden

Green field is also marked by a

Glossifungites

assemblage locally

consisting of

Rhizocoralliurn

(Fig.

17B),

Diplocraterion

and

Thalas-

sinoides.

The Viking Kaybob field in central

Alberta (Fig. 22) produces hydrocar-

bons from a coarsening-upward,

NW-

SE-trending sandstone body. The

sandstone overlies an extensive ero-

sion surface incised into thoroughly

burrowed silty to sandy shales con-

taining a diverse Cruziana assem-

blage of

Teichichnus, Helrninthopsis,

Asterosorna, Terebellina, Planolites,

Zoophycos, Chondrites,

rare

Rosselia,

and

Rhizocoralliurn.

The mixture of

grazing and deposit-feeding traces

suggests offshore shallow-marine de-

position. Cores in proximal positions

(Fig. 22) show the underlying

sandier-

upward offshore facies succession

abruptly truncated by the erosional

discontinuity. The discontinuity is

marked by a

Glossifungites

assem-

blage consisting of robust

Skolithos

and

Thalassinoides,

passively filled

with medium to coarse sand which in-

filtrated the burrows from the overlying

facies. The overlying sandstone is

medium grained and contains

low-

angle parallel lamination and rarer os-

cillation ripples. The trace fossil suite

mainly consists of structures made by

deposit feeders, suspension feeders,

and passive carnivores with less abun-

dant grazing traces, and is manifest by

Skolithos, Ophiornorpha, Bergaueria,

Palaeophycus, Teichichnus,

Aster-

osorna, Rosselia, Planolites, Tere-

bellina, Helrninthopsis,

and

Chon-

Figure 21

Pre-erosion (A), erosion

(B),

and posterosion (C) trace fossil suites, Albian Viking Formation, Crystal Field, Alberta.

A) Pre-erosion softground suite representing a distal

Cruziana

assemblage in intensely burrowed offshore, to lower shoreface silty to sandy

shales. Traces include

Helrninthopsis, Planolites, Thalassinoides, Terebellina, Teichichnus, Rhizocorallium,

and rare

Arenicolites, Skolithos,

and

Palaeophycus.

Erosion suite, consisting of a

Glossifungites

assemblage of sharp walled, unlined, mud filled

Diplocraterion

shafts,

cross cutting a distal

Cruziana

suite. Contact between the sandstone at the top of the photograph and the sandy shale corresponds to the

base of the incised valley fill. C) posterosion suite consists of a low-diversity assemblage of sparse

Planolites

and rare

Skolithos.

Traces are

developed in wavy bedded oscillation and combined flow ripple laminated fine sandstones and dark shale drapes. Suite reflects a stressed

(brackish?) environment.

PEMBERTON, MACEACHERN, FREY

drites. This sharp-based sandstone is

interpreted to reflect a

storm-domi-

nated lower- to middle-shoreface

setting.

Farther seaward to the northeast, the

same erosion surface lacks a

Glossi-

fungites suite, but is marked by dis-

persed pebbles and medium- to

coarse-sand grains. The erosion

surface is overlain by a gradually coars-

ening upward succession of intensely

burrowed silty and sandy shales con-

taining a diverse

Cruziana suite of

abundant Asterosoma, Terebellina,

Planolites, Zoophycos, Chondrites, and

Helminthopsis; up ward, Teichichnus,

Rosselia, Rhizocorallium, Skolithos,

and Arenicolites are more common, re-

flecting offshore to lower shoreface

progradation. Finally, the sandy shales

grade upward into intensely burrowed

shaly sandstones containing Skolithos,

Arenicolites,

Cylindrichnus, Palaeo-

phycus, Asterosoma, Terebellina,

Chondrites, Planolites, and Helmin-

thopsis, reflecting lower- to middle-

shoreface conditions.

The discontinuity is interpreted to be

a regressive surface of erosion, formed

as a result of a lowering of relative sea

level and incision into the underlying off-

shore shales. In proximal areas, the

erosion surface is abruptly overlain by

incised lower- to middle-shoreface de-

posits. In more basinal settings, the dis-

continuity is overlain by distal equiv-

alents of the incised shoreface, which

prograded basinward and generated a

more gradual coarsening-upward suc-

cession. This relationship defines a

forced regression (Chapter 12;

Plint,

1988; Posamentier and Vail, 1988).

Transgressive surfaces of erosion

(ravinement surfaces) afford the most

elegant mode of developing wide-

spread substrate-controlled

ichnofa-

cies. This is principally because the

exhumed surfaces are generated

within a marine or marginal marine en-

vironment, favouring colonization by

organisms as the surface is cut, and

prior to significant deposition of over-

lying sediment.

Transgressive surfaces of

erosion

example from the

Viking Formation

The Viking Formation can be used

again, this time providing excellent ex-

amples of transgressive surfaces of

erosion. Several such surfaces occur

near the top of the formation. In the

Kaybob field, the

lowstand incised

shoreface setting discussed previously

(Fig. 22) is overlain by pebbly shales

with thin gritty sands, containing a

trace suite of

Terebellina, Helmin-

thopsis, Planolites, Teichichnus,

Chondrites, and Zoophycos. This style

of sedimentation is interrupted by

Glossifungites assemblages

(Sko-

lithos, Arenicolites, Diplocraterion, and

Thalassinoides) that occur at "hidden"

bed junctions, associated with periods

of erosion (ravinement) and stillstand.

These deposits are overlain by indis-

tinctly burrowed marine shales having

thin silty sand stringers and rare

Planolites.

The incised shoreface succession

(Fig. 22) is interpreted to reflect

basin-

ward progradation, following the

forced regression. This was termi-

nated by a relative rise in sea level,

when associated ravinement stripped

off the upper shoreface and coastal

plain facies. Periodic stillstands during

the overall transgression permitted de-

position of the pebbly shale facies,

while resumed transgression gener-

ated erosional discontinuities marked

Glossifungites suites (Fig. 23).

Continued transgression of the Col-

orado sea resulted in deposition of

distal offshore to shelfal shales.

Similar facies successions occur in

other parts of the Viking Formation

(e.g. Joarcam field, Power, 1988;

Joffre field, Downing and Walker,

1 988).

Amalgamated lowstand erosion

and transgressive surfaces

Amalgamated (or coplanar) lowstand

erosion and transgressive surfaces

are commonly colonized by

substrate-

controlled tracemakers. Erosion during

lowstand typically produces wide-

spread firmground, hardground, and

woodground surfaces. The following

transgressive event tends to remove

much of the

lowstand deposits and

exposes the discontinuity to marine or

marginal marine conditions (Chapter

12). Organisms then colonize the re-

exhumed flooded surface. Savrda

(1991) noted that the

lowstand uncon-

formity at the Cretaceous-Tertiary

contact in Alabama contained a sub-

strate-controlled ichnofacies only

where an overlying transgressive sur-

face of erosion was amalgamated with

it. Localities where valley fill deposits

separate the unconformity from the

Union Kaybob

-35-61-20~5

Figure

Strip log of a cored interval of

the Viking Formation (Albian) in the

Kaybob Field in central Alberta (symbols

explained in Fig.

19).

Facies interpret-

ations are shown on the right -hand side of

the log; key surfaces are marked on the

left. The lower half of the section shows

lower- to middle-shoreface deposits

abruptly attenuating offshore sandy shale

deposits. The erosional discontinuity is

marked by a

Glossifungites assemblage

consisting of Skolithos. The shoreface is

interpreted to be a result of "forced regres-

sion", due to a relative lowering of sea

level. The

lowstand shoreface is truncated

by sandy and pebbly shales containing nu-

merous

Glossifungites assemblages de-

veloped at hidden bed junctions. The

overlying assemblage reflects transgres-

sive deposition resulting from ravinementl

stillstand cycles, ultimately being capped by

shelf deposits produced during maximum

marine flooding.