Geology Reference
In-Depth Information
Basics: Ancient seep and vent carbonates
Beauchamp, B., Bitter, P.H. (eds., 1992): Chemosynthesis:
geological processes and products. - Palaios,
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Beauchamp, B., Savard, M. (1992): Cretaceous chemosyn-
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7
, 434-450
Bitter, P.H.von, Scott, S.D., Schenk, P.E. (1992): Chemosyn-
thesis: an alternative hypothesis for Carboniferous biotas
in bryozoan/microbial mounds, Newfoundland, Canada.
- Palaios,
7
, 466-484
Callender, W.R. (1999): Why did ancient chemosynthetic seep
and vent assemblages occur in shallower water than they
do today? - International Journal of Earth Sciences,
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Campbell, K.A., Bottjer, D.J. (1995): Brachiopods and
chemosymbiotic bivalves in Phanerozoic hydrothermal
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Cavagna, S., Clari, P., Martine, L. (1999): The role of bacte-
ria in the formation of cold seep carbonates: geological
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Clari, P.A., Martire, L. (2000): Cold seep carbonates in the
Tertiary of northwest Italy: evidence of bacterial degra-
dation of methane. - In: Riding, R.E., Awramik, S.M.
(eds.): Microbial sediments. - 261-269, Berlin (Springer)
Gaillard, C., Rio, M., Rolin, Y., Roux, M. (1992): Fossil
chemosynthetic communities related to vents or seeps in
sedimentary basins: the pseudobioherms of southeastern
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mann, J. (2003): The Late Eocene 'Whiskey Creek' meth-
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Hovland, M., Thomsen E. (1997): Cold-water corals - are
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Little, C.T.S., Herrington, R.J., Haymon, R.M., Danelian, T.
(1999): Early Jurassic hydrothermal vent community from
deposits indicate the existence of seep-related microbes
and reveal that anaerobic oxidation of biogenic meth-
ane was an important component in the biogeochemi-
cal cycling of carbon in this ancient seep environment.
16.5.2.2 Early Cretaceous Seep Carbonates in
the Canadian Arctic
An excellent example of ancient of chemosynthetic
cold-seep biota and carbonate mounds was reported
from the Early Cretaceous (Aptian to Albian) of the
Sverdrup Basin (Beauchamp and Savard 1992; Pl. 148).
The circular mounds vary in diameter between 1 and
60 m and in height from 1 to 8 m. They originated in
deep (about 400 m) and cold waters on the sea floor of
a rifting basin. A cold climatic setting is indicated by
glendolite concretions, pebble- and cobble-sized ice-
rafted dropstones and the high paleolatitudinal setting
of the siliciclastic sediments yielding the carbonates.
The seep communities consist of abundant and densely
growing bivalves and serpulid worm tubes, associated
with terebratulid brachiopods. The fossils are enclosed
in an isotopically-light carbonate groundmass which
is volumetrically far more important than the fossils.
The mounds formed by a complex sequence character-
ized by recurrence of fossils and methane-derived car-
bonate phases (micrite, botryoidal calcite/former ara-
gonite, splayed calcite, yellow calcite), interrupted by
episodes of carbonate corrosion and pyrite precipita-
tion. These processes took place in an environment that
shifted back and forth between aerobic, oxidizing, H
2
S-
free conditions and anaerobic, reducing and H
2
S-rich
conditions.
Plate 148 Early Cretaceous ColdSeep Carbonates of the Canadian Arctic
This plate displays microfacies criteria whose combination is diagnostic of seep carbonates. Diagnostic
microfacies criteria are the occurrence of specific bivalves (-> 2) and worms (-> 1, 2), and the complex cemen-
tation pattern (->1, 3).
1
Worm-tube dominated rudstone
. Large and small serpulid worm tubes (black arrows) are cemented by several generations
of methane-derived authigenic carbonates. Marked differences in the composition of the carbonate (micrite, various types
of cements), corrosion features and pyrite precipitation indicate changes in carbonate precipitation and settlement by
specialized chemoautotrophic organisms feeding on bacteria. Note the complex sequences of botryoidal and fibrous
cement. Early Cretaceous (Aptian to Albian): Ellef Ringness Island, Canadian Arctic.
2
Bivalve shells
in methane-derived micrite. The bivalves are lucinids. Numerous fecal pellets demonstrate high biological
activity at seep sites. The ovoid pellets consist of dark micritic material with variable proportions of silt-sized quartz,
foraminifers and bioclastic debris. Same locality as -> 1.
3
Large serpulids
(S) cemented by multiple generations of methane-derived carbonates. Note the distinct difference be-
tween authigenic microcrystalline calcite (M) and other cement types (C). Early Cretaceous (Aptian to Albian): Prince
Patrick Island, Canadian Arctic.
-> 1-3: Courtesy of B. Beauchamp (Calgary)
