Maximum age for a concretion at Green Creek, Ontario L'âge maximal d'une concrétion à Green Creek, Ontario - Érudit
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Géographie physique et Quaternaire
Notes
Maximum age for a concretion at Green Creek, Ontario
L’âge maximal d’une concrétion à Green Creek, Ontario
Nelson R. Gadd
Volume 34, numéro 2, 1980 Résumé de l'article
Un morceau de bois (? Salix sp.), prélevé dans une concrétion calcaire
URI : https://id.erudit.org/iderudit/1000400ar provenant de la terrasse de - 43 m au site de Green Creek, en Ontario, a fourni
DOI : https://doi.org/10.7202/1000400ar un âge radiocarbone de 9 960 ± 820 BP (GSC-2498). Les carbonates de la
concrétion ont fourni un âge apparent de 14 400 ± 250 BP (GSC-2530).
Aller au sommaire du numéro L’âge du bois est un âge maximal pour la mise en place des sédiments
qui entourent le bois ainsi que pour la formation de la concrétion. Le résultat
de la datation sur les carbonates semble anormal. L’âge maximal du
bois, en se basant sur la limite d’erreur, est de 10 789 BP. À ce moment,
Éditeur(s)
la mer de Champlain recouvrait la région jusqu’à au moins 100 m
Les Presses de l’Université de Montréal d’altitude. L’âge réel du bois se rapproche probablement plus
de celui des moules d'eau douce prélevées à - 53 m à Bourget (10 200± 90;
ISSN GSC-1968) ou du bois découvert à ~ 61 m à Hawkesbury (9 860 ± 230; BGS-257).
Les sédiments de la terrasse de ~ 43 m ont probablement été mis en place en
0705-7199 (imprimé) eau douce. La présence d’une flore et d’une faune terrestre et
1492-143X (numérique) d’eau douce, dans diverses concrétions provenant du site de Green
Creek, suggère d’ailleurs une mise en place des sédiments dans un
Découvrir la revue milieu estuarien ou d’eau douce. La présence anormale, semble-t-il,
d’organismes marins, comme les squelettes de poissons, dans les
concrétions est reliée à un processus chimique de la précipitation d’un
ciment calcaire provoqué par la putréfaction de la chair des organismes. Ce
Citer cette note
phénomène pourrait contribuer à la conservation de fossiles fragiles au cours
Gadd, N. R. (1980). Maximum age for a concretion at Green Creek, Ontario. d’un ou même de plusieurs cycles d’érosion. Certains fossiles
Géographie physique et Quaternaire, 34(2), 229–238. retrouvés dans les concrétions du site de Green Creek sont probablement
https://doi.org/10.7202/1000400ar allochthones aux sédiments dans lesquels ils se retrouvent.
Tous droits réservés © Les Presses de l’Université de Montréal, 1980 Ce document est protégé par la loi sur le droit d’auteur. L’utilisation des
services d’Érudit (y compris la reproduction) est assujettie à sa politique
d’utilisation que vous pouvez consulter en ligne.
https://apropos.erudit.org/fr/usagers/politique-dutilisation/
Cet article est diffusé et préservé par Érudit.
Érudit est un consortium interuniversitaire sans but lucratif composé de
l’Université de Montréal, l’Université Laval et l’Université du Québec à
Montréal. Il a pour mission la promotion et la valorisation de la recherche.
https://www.erudit.org/fr/Géogr. phys. Quaf., 1980, vol. XXXIV, n°2, p. 229-238.
Notes
MAXIMUM AGE FOR A CONCRETION
AT GREEN CREEK, ONTARIO
Nelson R. GADD, Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario K 1 A 0 E 8 .
ABSTRACT Wood (?Salix sp.) from a concretionary nodule found at - 43 m a.s.l. at the Green Creek, Ontario, site was dated at
9960 ± 820 BP (GSC-2498). The carbonate concretion has an apparent age of 14400 ± 250 BP (GSC-2530). The wood date is
a maximum age for the enclosing sediment and for its cementation ; the carbonate date appears anomalous.
At the time of the upper limit of error for the wood date (10 780 BP) Champlain Sea stood at or above 100 m a.s.l.The true age
of the wood probably is compatible with that of freswhater shells at - 53 m a.s.l. at Bourget, Ontario (10 200 ± 90; GSC-1968),
and of wood at - 61m a.s.l.at Hawkesbury, Ontario (9860 ± 330; BGS-257).Terrace sediments at ~ 43m a.s.l.probably areof fresh-
water origin. Terrestrial and freshwater flora and fauna in earlier collections of concretions from Green Creek also suggest an
estuarine to freswhater environment for the enclosing sediments.
Occurrence of complete skeletons of fish and other vertebrates in concretions is related to chemically induced carbonate
cementation during early stages of putrefaction of soft-bodied animals. This could preserve skeletal remains through several
cycles of erosion. Therefore some concretions carry fossil remains that may be allochtonous to the sediment in which they now
occur.
RÉSUMÉ L'âge maximal d'une concrétion à Green Creek, Ontario. Un morceau de bois (? Salix sp.), prélevé dans une concré-
tion calcaire provenant de laterrasse de - 43m au sitede GreenCreek, enOntario, afourni un âge radiocarbone de 9960 ± 820 BP
(GSC-2498). Les carbonates de la concrétion ont fourni un âge apparent de 14400 ± 250 BP (GSC-2530). L'âge du bois est un
âge maximal pour la mise en place des sédiments qui entourent le bois ainsi que pour la formation de la concrétion. Le résultat
de la datation sur les carbonates semble anormal.
L'âge maximal du bois, en se basant sur la limite d'erreur, est de 10789 BP. À ce moment, la mer de Champlain recouvrait la
région jusqu'à au moins 100 m d'altitude. L'âge réel du bois se rapproche probablement plus de celui des moules d'eau douce
prélevées à- 53 m à Bourget (10 200± 90; GSC-1968) ou du bois découvert à ~ 61 m à Hawkesbury (9 860 ± 230; BGS-257). Les
sédiments de la terrasse de ~ 43 m ont probablement été mis en place en eau douce. La présence d'une flore et d'une faune
terrestre et d'eau douce, dans diverses concrétions provenant du site de Green Creek, suggère d'ailleurs une mise en place des
sédiments dans un milieu estuarien ou d'eau douce.
La présence anormale, semble-t-il, d'organismes marins, comme les squelettes de poissons, dans les concrétions est reliée
à un processus chimique de la précipitation d'un ciment calcaire provoqué par la putréfaction de la chair des organismes. Ce
phénomène pourrait contribuer à la conservation de fossiles fragiles au cours d'un ou même de plusieurs cycles d'érosion.
Certains fossiles retrouvés dans les concrétions du site de Green Creek sont probablement allochthones aux sédiments dans
lesquels ils se retrouvent.
in earlier liter
HISTORICAL BACKGROUND OF GREEN a t u r e ) ( F i 9- 1 )- Hiawatha Park, at the
SODCC.V f m i f D C T i n n c same place, was the terminus of a now long-defunct
CHEEK CONCHETIUNb „.
Ottawa River ferry boat where, it is said, the ferry pilot
Concretionary nodules of laminated sediment have made a small c o m m e r c e from collecting and selling
been collected for more than a century at a site about concretions, getting his best prices for those c o n -
10 km east of the Parliament Buildings of Ottawa, On- taining skeletal remains of fish and other organic
tario, on the south bank of the Ottawa River and in the remains. These popular curios were also the subject of
valley of a small tributary, Green Creek (Green's Creek, n u m e r o u s scientific c o m m e n t s and studies that have230 N. R. GADD
75°30' 74-30'
2- TWINELM -Marine shellsandseaweed -el ~ 100m
GSC-587-Shells(l03.6m) 10620*200
GSC-570-Seaweed(97.9m) I0800±I50
GSC-588-Shells(96.9m) 10 8801160
3- BOURGET- Freshwatershells -el ~ 53m
GSC-1968-Lampsilissp I 0 2 0 0 t 9 0
4 - H AWKSBURY - Woodin sandy gravel - el. ~ 61m
BGS-257- Wood andsilt ballsinsandygravel -
9860±330
5- RUSSELL-Marine shells-el.~70m
GSC -1553- Macomabaltica +Macomacalcarea -
10000 1320
GENERALLOCATION AND FLOW DIRECTION OFMAJORABANDONEDRIVERCHANNELS
SSS:¥:¥:¥:;:;:::;:::::;:;::... WeiI defined : ::::::: : .:.:.:.:. Poorlydefined
10 10 20 30km
75°30 75° 74°30'
FIGURE 1. Location map. Sites of radiocarbon dates re- Cartes de localisation des datations au radiocarbone cités
ferenced in text and pattern of major abandoned river chan- dans le texte et schéma des principaux chenaux fluviatiles
nels. délaissés.
appeared in the literature. The age and significance of cept that the clay deposits that enclose the fossils, are,
the concretions and of their contained fossils have therefore, of marine origin.
been the subjects of varied interpretation. It should be noted, however, that after his nota-
In a summary report, LOGAN (1863, p. 916-917) tion of marine species present in the clay, LOGAN
reported : "About the mouth of Green's Creek in Glou- (1863, p. 917) added: "besides which are a species of
cester, a bed in the clay, near highwater mark, abounds freshwater shell, and various land-plants. Among the
in nodular masses, which are strewn along the shore of latter, Dr. Dawson has recognized the following
the Ottawa for two miles to the eastward. These seem species: Drosera rotundifolia, Trifolium repens, Poten-
to have been formed by a process of concretion tilla Norvegica, P. tridentata, P. Canadensis, Arctos-
around various organic remains." Among these re- taphylos uva-ursi, Populus balsamifera, Potamogeton
mains he noted Mallotus villosus, or capeling of the perfoliata, and P. natans; besides grasses, carices,
lower St. Lawrence" and other species of fish and mosses, and algae."
molluscs of the marine environment. Emphasis of HARINGTON (1971, 1972, 1977, 1978 and referen-
marine fossil content of concretions by numerous ces therein) summarized the history and environment
studies and references gives rise to the general con- of Champlain Sea and reviewed the vertebrate fossilsMAXIMUM AGE FOR A CONCRETION 231
found, including fish. Many of the reference specimens the brickyards away from the stream valleys", and
were enclosed in concretions from the Green Creek further : "Where seen in place in the clays the concre-
site. CHAMPAGNE ef al. (1979) reported the occur- tions lie with their longer axis in the direction of the
rence of a deepwater sculpin, Myoxocephalus thomp- planes of bedding. The beds show no evidence of bulg-
soni (Girard), in a Green Creek concretion. The discus- ing or unevenness around the concretions... It is
sion of the significance of this vertebrate "only recod- generally held that calcareous clay concretions..., are
ed from freshwater" in association with other species, found only in the zone of cementation, above the
some clearly freshwater and some clearly marine, general permanent level of the ground water... Hence
from other concretions led the authors to indicate it is probable that the concretions were formed after
some choice as to interpretation of the environment the complete withdrawal of the marine waters and large-
that is represented. Their suggestions range from cata- ly during the time since the establishment of the
strophic drainage of freshwater lakes into the sea, to present drainage."
the alternative that "the "sea" itself may have been
fresh during the final phase...". Further evidence of a
freshwater environment was presented by GRUCHY
(1968) who identified a lake trout Christivomer namaya- OTHER NOTES ON THE ORIGIN OF
cush, that is not anadromous {I.e., does not travel be- CONCRETIONS
tween the sea and freshwater).
Observations on the nature of concretions in St.
DAWSON (1893) noted "upper" (= non-marine?) Lawrence Valley varved clay led the present author
and "lower" (= marine) clays in the St. Lawrence Low- (GADD, 1971, p. 47-48) to the conclusion that ground-
land and apparently used marine fossil content (in pre- water moved horizontally most freely along the coarse-
ference to freshwater and terrestrial forms he also grained (summer) layers of the varves and that the
identified) in the concretions to classify the Green sediments probably were cemented as a result of e-
Creek sediments as "lower" clay. JOHNSTON (1917), vaporation of groundwater at the exposure face. More
however, classified the younger clay at Green Creek recently CARTER ef al. (1977), working in Ireland,
and other similar sediment of the Ottawa region as la- compared the chemistry and mineralogy of concretions
custrine, but ANTEVS (1925, 1939) recognized two clay in varves with those of natural, or uncemented, varves.
bodies at Green Creek, and elsewhere in Ottawa Valley, Their findings allowed the conclusion that "slow per-
and used the presence of marine species in the concre- colation of groundwater may have assisted the proc-
tions of the "upper" clay to support his concept of two ess" of the formation of nodular concretions. In addi-
separate invasions of the valley by the sea; first Cham- tion, they determined that the carbonate content of
plain Sea, then "Ottawa Sea". Indeed ANTEVS (1925) concretions was about 15% higher than that of un-
introduced the name "Lake Ottawa" for the environ- cemented varves of the same formation.
ment of deposition of sediment identified by Johnston,
BERNER (1969) revealed another aspect of the ori-
and only later (ANTEVS, 1939) changed it in favour of
gin of concretions by observing fish sealed in jars con-
"Ottawa Sea". The present writer (GADD, 1961, 1963,
taining sea water and other solutions over periods of
1971) has challenged the Ottawa Sea concept, and has
only to 205 days. From his study of the chemical re-
supported an interpretation closer to that of JOHN-
actions activated by bacterial decomposition of the
STON (1917). Commenting on previous "unsatisfac-
fish, he suggested "that some ancient CaCÛ3 concre-
tory" reports of sandy beds between two clay beds in
tions, especially those enclosing fossils of soft-bodied
Ottawa Valley, ANTEVS (1962, p. 197) brought his
organisms, may have been formed rapidly after death
conclusions almost full cricle with the statement that
in the form of natural Ca soap (adipocere) which was
his "new interpretation implies that Champlain Sea had
later converted to CaCOa". The experiments showed
only one deep-water stage".
that chemical conditions present were adequate "to
precipitate calcium as CaCÛ3 during the early stages of
The nature and origin of the concretions themselves
decay".
were investigated in a classic paper by KINDLE (1923)
in which he made this significant statement (p. 624): It is not surprising that various authors, dealing with
"The general absence of concretions from the clays cut one or more of the varied characteristics of concre-
by ditches leads to the inference that their develop- tions found at Green Creek, Ontario, should have had
ment is limited to a superficial zone of clay which has a number of different interpretations of their findings.
been exposed for a considerable period in the stream- New information, presented here, may provide a con-
bank sections of the district." JOHNSTON (1917, p. 29), trol over the use of some types of data for the inter-
speaking of the Ottawa Valley concretions, made these pration of the environment of deposition of the sedi-
similar notes: "calcereous concretions... are not known ments themselves and of the cementation of concre-
to occur in the clays exposed in excavations as in tions at Green Creek.232 N. R. GADD
SETTING AND AGE OF THE WOOD-BEARING In 1961, the present writer made a collection of all
CONCRETION concretions from a strip of shore measuring 3 x 30 m
lying between low water level of Ottawa River and the
base of the river bank scarp; their total number was
approximately seven hundred. All were split so as to
The Hiawatha Park collecting ground for the Green
expose the core of the concretion. By far the largest
Creek concretions is located on the shore of Ottawa
number of concretions consisted solely of cemented
River about 10 km east of Ottawa and about 1.5 km
sediment. Fewer than sixty concretions (MAXIMUM AGE FOR A CONCRETION 233
i^H^I
L
^^^X. jatHM
wFJ'lÊ
1' sM "^
jj/y
a^HiV/^"'
y'
r-1 '**-"$ -234 N. R. GADD
age; the entire concretion may have been transported
intact and may be allochthonous to the particular se-
dimentary layer in which it now rests.
If we extend our thinking to the deposits on the
shore of the modern Ottawa River, we can see very
easily that concretions of all types and probably of
several ages, are being buried in present-day sedi-
ments. I assume that none of those concretions has
formed in situ in the modern sediment and that none
can represent the modern environment of the sediment
in which they are being incorporated. Modern drift-
wood, e.g., logs that have espaced from log booms
of the local paper mills, other materials such as mill
and city effluents, and clams living in the river mud, are
the type of fossil that could be considered as repre-
sentative of the modern environment of sedimentation
and of its age; but not the concretions.
In the same way, possibly only the piece of willow(?)
wood from the Green Creek concretion (Fig. 4) may
be representative of the environment and age of the
sediment exposed in the river bank. However, even that
piece of wood may have been recycled a number of
times and cannot necessarily be considered specifical-
ly representative. It provides only a maximum age for
the sediment. Until a younger piece of wood, or other
younger fossil in living position, is found, this one
wood fragment must serve as a reference point.
Wood vs. carbonate date: Other publications (e.g.,
HILLAIRE-MARCEL, 1977) have used radiocarbon age
of carbonate concretions to represent the age of the
sediment in which they are found, but this requires a
FIGURE 4. Green Creek concretion containing piece of Wil- selective measurement on chemical rather than me-
low (ident. ? Salix sp. by R. J. Mott): a) concretion split to
chanical deposits. Total carbonate analyses may be
show wood (now destroyed) in place; b) concretion reas-
sembled to show discovery aspect. Dimensions of concretion, exptected to reflect the age of local bedrock. HILLAI-
max. width 5 cm, max. length 7.5 cm (original concretion ap- RE-MARCEL (1979, e.g., p. 220-221) states that car-
prox. 9 cm). bonate granules in both glaciolacustrine and marine
Morceau de bois (? Salix sp. identifié par R. J. Mott): a) sediments in the St. Lawrence Lowland are derived
concrétion sectionnée afin de montrer le morceau de bois from local bedrock sources: "les fractions carbonatées
(détruit depuis) dans saposition originelle;b) assemblage des des sédiments paraissent indubitablement héritées des
deux sections afin d'en montrer l'aspect au moment de la socles locaux." This is reflected in the similarity be-
découverte: Dimensions: 5 cm de largeur maximale, 7,5 cm tween the 1 3 C/ 1 2 C and 1 8 0 / 1 6 0 ratios of the sediments
de longueur maximale (9 cm environ pour la concrétion and of the local Paleozoic or Precambrian rocks.
originelle).
The dates obtained on wood and carbonate material
One might believe that skeletal remains of vertebrate of the concretion shown in Figure 4 are widely diver-
fish and land animals would represent the environment gent. That the carbonate (GSC-2530) was older than
of deposition, simply because it is difficult to conceive the wood (GSC-2498) was in some degree predictable.
of animal skeletal remains being transported intact Carbonate material in the sediment probably includes
through even one cycle of erosion. However, rapid ce- granules of both Paleozoic and Precambrian carbonate
mentation during decay of soft-bodied organisms, as rocks (cf. HILLAIRE-MARCEL, 1979, op. cit.); these
indicated by BERNER (1968, op. cit.) may provide the contaminate any contemporaneously precipitated car-
necessary resistance to erosion. Even though Haring- bonate. Groundwater that percolated through the sedi-
ton (personal communication) indicates that numerous ment and that probably added as much as 15% of the
concretionary specimens show marine molluscs in an datable carbonate of the concretion (cf. CARTER ef al.,
apparent living relationship with fish skeletons and 1977) would be the only other source of carbonate
that, therefore these animals in life were of the same contemporaneous with the deposition of the sedimentMAXIMUM AGE FOR A CONCRETION 235
TABLE I
Offaiva Valley Dates Compared with Green Creek Concretion
13
Sample Material Laboratory Uncorrected 8 C Corrected Sample Counter Pressure Counting Comments
Elevation Dated Dating ,4
C Age (%o) ' 4 C Age Weight (|) (atm.) Time
(m a.s.l.) Number (g) (days)
Twin Elm Shells GSC-587 10620 ± 2 0 0 — 61.0 30% leach;
-104 m Macoma sample mixed
balthica with dead gas
for counting
(some gas lost)
- 98m Seaweed GSC-570 10 800 ± 150 44.3 NaOH treatment
mainly burned omitted
Laminaria
- 97m Shells GSC-588 10 880 ± 160 68.5 20% leach
Macoma
balthica
Russell Shells GSC-1553 10000± 320 11.5 10% leach;
- 70m Macoma sample mixed
balthica & with dead gas
Macoma for counting
calcarea
Hawkesbury Wood BGS-257 9860 ± 330 4.3 No
- 60m (unident.) pretreatment
Bourget Shells GSC-1968 10 200 ± 90 46.1 20% leach
- 53m Lampsilis
sp.
Green Creek Wood GSC-2498 9980 ± 820 0.6 HC1 and distil-
- 43 m (? Salix led water;
sp.) NaOH omitted ;
sample mixed
with dead gas
for counting
43m Carbonate GSC-2530 14300 ± 250 -20.1 14,400 ± 250 14.1 No pretreat-
concretion ment; sample
mixed with
dead gas for
counting
or with its cementation. It would seem possible, then, gives a hypothetical range of ages for the wood be-
that the groundwater, too, was contamined by old car- tween 10780 and 9140 years BP.
bonate.
Age comparison with other dated deposits : Radio-
Radiocarbon laboratory procedure included acid carbon ages of marine shells and seaweed (ident. as
treatment of the wood sample (See Table I). It is un- mainly Laminaria by ILLMAN ef al. (1970)), at Twin
likely that the wood as dated could have been contami- Elm, Ontario (MOTT, 1968) (GSC-570, -587, -588, Table
nated by older carbonate. The wood is therefore the I) establish that regional sea level (Champlain Sea)
preferred dating material. was at or above 100 m a.s.l. in the potential time
range of 11040 to 10420 yr. BP. RICHARD (1973)
Sedimentary granules and the wood fragment in (GSC- 1553, Table I) records a marine shell date from
Green Creek sediment both are of greater age than the Russell, Ontario, indicating that sea level may have
fluvial sediment they combine to form. Lacking fossils been at about 70 m a.s.l. in the time range 10320 to
that are in living position, the closest approximation of 9680 yr. BP. If we assume the wood grew near the
the time of sedimentation is the age of the younger freshwater fluvial system in which it is found there is
transported material, which in this case is presumed to little possibility that the Green Creek wood sample, col-
be the small piece of willow(?) wood. Because of lected at about 43 m a.s.l., could have a true radio-
the small size of the wood sample there is a wide carbon age in excess of 10000 years. The age of the
margin of error (±820 yr.) in the calculated age that Green Creek sediment, logically, is less than that.236 N. R. GADD
ï '"fr/
• ^fcfcjgjil»»
J0
T^r>
1
J;
plane of the concretion is parallel to the plane of the paper,
therefore fossils shown lie with long axes parallel to the bed-
ding plane.
Grosses concrétions provenant du site de Green Creek
contenant des fossiles et des cailloux: 5a) Hiatella arctica ef
plusieurs granules de roches paléozoïques et précambriennes.
Dimensions maximales de la concrétion: 12 cm de largeur et
FIGURE 5. Large Green Creek concretions containing fossils 18,5 cm de hauteur; 5b) Hiatella arctica, plusieurs granules et
and pebbles: 5a) Hiatella arctica and numerous granules of cailloux. À remarquer un gros caillou de gneiss granitique
both Paleozoic and Precambrian rocks (max. dimensions of précambrien, dans la partie inférieure droite, dont la largeur
concretion: 12 cm wide, 18, 5 cm high; b) Hiatella arctica maximale est de 3 cm. Dimensions maximales: 22 cm de lar-
and numerous granules and pebbles. Large pebble of Precam- geur, 18 cm de hauteur. À noter que dans ces figures le
brian granite gneiss, lower right, is approximately 3 cm in plan de sédimentation concorde avec celui du papier; les fos-
long diameter; maximum dimension of concretion : 22 cm siles visibles ne sont pas en position de vie, l'axe le plus
wide, 18 cm high. Note: in figure 5a and 5b, the bedding long étant parallèle au plan de sédimentation.
The undisturbed marine sediments of Ottawa Val- tion and incised more deeply into the underlying
ley have been extensively eroded by a river channel marine sediment, are younger than those at Bourget
system at least 16 km w i d e at Ottawa (RICHARD ef al., (—53 m) and possibly also younger than those at Haw-
1977) f r o m w h i c h at least 50 m of sediment has been kesbury ( ~ 6 1 m). Therefore, if the presence of Lampsil-
removed in areas adjacent to Ottawa River and its tri- is sp. at Bourget (Table I) indicates a freshwater en-
butaries. Secondary fluvial d e p o s i t s w i t h i n this n o w v i r o n m e n t in the channel system, a younger, lower
largely abandoned fluvial system at elevation ca. 53 m sector of the same system also should have been
have yielded freshwater shells (Lampsilis sp.) at Bour- related to freshwater.
get, Ontario, whose radiocarbon age is 10 200 ± 90
years (GSC-1 968) (GADD, 1976; Table I). (Possible c o n - CONCLUSIONS
t a m i n a t i o n of the freshwater shell carbonate of this
1. The radiocarbon age of a piece of w i l l o w ( ? )
sample w o u l d allow for the sediment to be consider-
w o o d enclosed in a calcareous c o n c r e t i o n at Green
ably y o u n g e r than 10 200 years.) SHARPE (1979, and
Creek, Ontario, establishes the m a x i m u m age of the
oral c o m m u n i c a t i o n , December 1979) reports w o o d
enclosing sediment and of its cementation at 10 780
f r o m fluvial sandy gravel at elevation 61 m near Haw-
to 9 140 years BP (9 960 ± 820; GSC-2 498). Compari-
kesbury, Ontario, w h o s e age is 9860 ± 330 years
son with other dates in the area precludes the possi-
(BGS-257). The concretionary sediments at Green
bility that the true age could exceed 10 000 yrs. BP.
Creek o c c u r in a younger sector of the same channel
system at an elevation of c a . 43 m a.s.l. The Green 2. The anomalous age of 14 400 ± 250 years
Creek sediments, being deposited at the lower eleva- (GSC- 2530) for the concretionary nodule around theMAXIMUM AGE FOR A CONCRETION 237
M
piece of w o o d is related to the presence of carbonate (1962): Transatlantic climatic agreement versus C
granules of Precambrian and Paleozoic age in the sedi- dates, J. Geol., 70, p. 194-295.
ment, and to dissolved material of the same age in the BERNER, R. A. (1968): Calcium carbonate concretions formed
percolating g r o u n d w a t e r that presumably provided by the decomposition of organic matter, Science, 159, p.
the cement. 195-197.
3. It is possible that the majority of fossil f o r m s in CARTER, R. W. G., FISHER, G. C , and ROBERTS, J. C. (1977):
the Green Creek concretions contained in freshwater Carbonate nodules from a pro-glacial lacustrine deposit at
sediment are in fact a l l o c h t h o n o u s , having been ac- Greys Town, County Londonderry, Irish Naturalists' J., 19,
No. 1, p. 4-6.
cumulated in fluvial sediments by erosion of earlier
marine and freshwater sediments. Such a possibility CHAMPAGNE, D. E„ HARINGTON, C. R., and McALLISTER,
w o u l d help to explain the association of marine, fresh- D. E. (1979): Deepwater sculpin, Myxocephalus thompsoni
water and terrestrial life f o r m s in a single sediment (Girard) from a Pleistocene nodule, Green Creek, Ontario,
Canada, Can. J. Earth Sci. vol. 16, No. 8, p. 1621-1628.
whose identification and origin has proven enigmatic
to several authors. DAWSON, J. W. (1893): The Canadian Ice Age, Montreal, Wil-
liam V. Dawson.
4. T o p o g r a p h i c position with respect to dated
freshwater shells indicates c o n t e m p o r a n e o u s or subse- GADD, N. R. (1961): Surficial geology of the Ottawa area,
report of progress, Ottawa, Geol. Surv. Can., Paper 61-19.
quent deposition of the sediments at Green Creek; this
infers freshwater c o n d i t i o n s at the time of burial and (1963): Surficial geology of Ottawa map-area, Ontario
cementation of the wood-bearing c o n c r e t i o n . and Quebec, Ottawa, Geol. Surv. Can., Paper 62-16.
5. The preferred interpretation of the Green Creek (1971): Pleistocene geology of the central St. Lawrence
Lowland, Ottawa, Geol. Surv. Can., Memoir 359.
sediment as being of freshwater fluvial origin precludes
the existence as live animals, d u r i n g d e p o s i t i o n of that — (1976): Surficial geology and landslides of the Thurso-
sediment, of only the strictly marine species. All other Russel map-area, Ontario, Ottawa, Geol. Surv. Can., Paper
materials f o u n d in the c o n c r e t i o n , representing birds, 75-35.
land animals, land and water plants, lake trout, deep — (1977): Offlap sedimentary sequence in Champlain Sea,
water s c u l p i n , capelin in spring spawning conditions, Ontario and Quebec, Ottawa, Geol. Surv. Can., Report of
may be a c c o m m o d a t e d in a fluvial environment drain- Activities, Part A, Paper 77-1A, p. 379-380.
ing to a nearby estuary. The burden of proof lies with GRUCHY, C. G. (1968): Two late Quaternary Salmonidae (Pis-
establishing comptability of the ages of these various ces) from the Ottawa region, Canada, Vestnik Cs. spot
materials with that of the w o o d sample reported in this zool. (Acta soc. zool. Bohemoslov), T. 32, No. 4, p. 337-
paper. 341.
HARINGTON, C. R. (1971): The Champlain Sea and its verte-
brate fauna. Part 1. The history and environment of the
ACKNOWLEDGEMENTS Champlain Sea, Trailand Landscape, 5, p. 137-141.
I sincerely thank R. J . Mott for identification of the (1972): The Champlain Sea and its vertebrate fauna.
w o o d sample (Fig. 4), C. R. Harington for identification Part II. The vertebrates of the Champlain Sea, 7ra;7 and
of the fish (Fig. 2), D. R. Sharpe and Q. H. J. Gwyn for Landscape, 6, p. 33-39.
discussion and permission to use unpublished informa- (1977): Marine mammals in the Champlain Sea and the
tion about the Hawkesbury site (BGS-257, Table I). W. Great Lakes,Ann. New York Acad. Sci., 288, p. 508-537.
Blake, Jr., C. R. H a r i n g t o n , and J . A. L o w d o n read a first (1978): Quaternary vertebrate faunas of Canada and
draft of the manuscript and offered constructive criti- Alaska and their suggested chronological sequence,
c i s m , most of w h i c h has been a c c o m m o d a t e d in the Syllogeus, Nat. Mus. Nat. Sci., Ottawa, No. 15, p. 1-105.
final draft. The author, of course, takes full responsibil- HILLAIRE-MARCEL, C. (1977): Les isotopes du carbone et de
ity for statements in the published format. In a d d i t i o n I l'oxygène dans les mers post-glaciaires du Québec, Géogr.
thank J.-S. Vincent for greatly improving my résumé in phys. Quat. vol. XXXI, Nos. 1-2, p. 81-106.
French. To critical readers assigned by the j o u r n a l , my (1979): Les mers post-glaciaires du Québec: quelques
sincere thanks for a c o n s c i e n c i o u s appraisal. aspects, Univ. Pierre et Marie Curie, Paris VI; Thèse de
doctorat d'État es sciences naturelles, p. 140 ef seq.; 220-
221.
REFERENCES ILLMAN, W. I., McLACHLAN, J., and EDELSTEIN, T. (1970):
Marine algae of the Champlain Sea episode near Ottawa,
ANTEVS, E. (1925): Retreat of the last ice sheet in eastern Can. J. Earth Sci.,vol. 7, p. 1583-1585.
Canada, Ottawa, Geol. Surv. Can., Memoir 146.
JOHNSTON, W. A. (1917): Pleistocene and Recent deposits in
(1939): Late Quaternary upwarping of northeastern the vicinity of Ottawa, with a description of the soils,
North America,J. Geol., 47, p. 707-720. Ottawa, Geol. Surv. Can., Memoir 101.238 N. R. GADD KINDLE, E. M. (1923): Range and distribution of certain types RICHARD, S. H. (1975) : Surficial geology mapping : Ottawa of Canadian Pleistocene concretions, Bull. Geol. Soc. valley lowlands (Parts of 31 G,B,F), Geo/. Surv. Can., Paper Amer. 34, p. 609-648. 75-1B, p. 113-117. LOGAN, W. E. (1963): Geology of Canada, 1863, Geological RICHARD, S. H., GADD, N. R., and VINCENT, J. S. (1977): Survey of Canada, Report of Progress from its commence- Surficial materials and terrain features, Ottawa-Hull, On- ment to 1863, Montreal, Dawson Brothers. tario and Quebec, Ottawa, Geol. Surv. Can., Map 1425A. MOTT, R. J. (1968): A radiocarbon-dated marine algal bed of SHARPE, D. R. (1979): Quaternary geology of the Merrickvil- the Champlain Sea episode near Ottawa, Ontario, Can. J. le area, southern Ontario, Ontario Min. of Natural Re- Earth Sci. vol. 5, p. 319-324. sources, Ontario Geol. Surv., Report 180, p. 34.
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