Uranium-thorium isotope systematics of cold-seep carbonate and their constraints on geological methane leakage activities

Tubes suspected to be those of vestimentiferan worms are abundant in carbonate boulders at one locality in the lower Oligocene part of the Lincoln Creek Formation along the Canyon River, Grays Harbor County, Washington. The largest tubes exhibit the same general orientation and are arranged in clusters. The tube walls are preserved as aragonite that is, in some cases, replaced by silica. The original tube walls either had a high carbonate content or were indurated very early by aragonite mineralization of the organic wall. The carbonate cements around, on, and inside of the tubes were precipitated due to the microbial oxidation of hydrocarbons at a cold-seep. After lithification, the carbonate fragmented as it slid or slumped, along with other sedimentary debris, downslope into deeper waters. This is one of the few reports of an ancient cold-seep chemosynthetic community dominated by tube worms, and the third report of an allochthonous cold-seep carbonate within a deep-water depositional setting.

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U–Th stratigraphy of a cold seep carbonate crust

Chemical Geology ◽

10.1016/j.chemgeo.2008.11.020 ◽

2009 ◽

Vol 260 (1-2) ◽

pp. 47-56 ◽

Cited By ~ 93

Author(s):

G. Bayon ◽

G.M. Henderson ◽

M. Bohn

Keyword(s):

Cold Seep ◽

Carbonate Crust ◽

Seep Carbonate

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Uranium/thorium dating of late pleistocene peat deposits in NW Europe, uranium/thorium isotope systematics and open-system behaviour of peat layers

Chemical Geology Isotope Geoscience section ◽

10.1016/0168-9622(92)90009-y ◽

1992 ◽

Vol 94 (3) ◽

pp. 161-171 ◽

Cited By ~ 11

Author(s):

H. Heijnis ◽

J. van der Plicht

Keyword(s):

Late Pleistocene ◽

Open System ◽

System Behaviour ◽

Peat Deposits ◽

Thorium Isotope ◽

Isotope Systematics ◽

Nw Europe

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A new occurrence of the Early Jurassic brachiopod Anarhynchia from the Canadian Cordillera confirms its membership in chemosynthesis-based ecosystems

Canadian Journal of Earth Sciences ◽

10.1139/cjes-2017-0179 ◽

2017 ◽

Vol 54 (12) ◽

pp. 1179-1193 ◽

Cited By ~ 1

Author(s):

József Pálfy ◽

Zsófia Kovács ◽

Gregory D. Price ◽

Attila Vörös ◽

Gary G. Johannson

Keyword(s):

Carbon Isotopic Composition ◽

Early Jurassic ◽

Cold Seep ◽

Cold Seeps ◽

Carbonate Sediments ◽

Microbial Oxidation ◽

Carbonate Cement ◽

Carbon Isotopic ◽

Oxidation Of Methane ◽

Seep Carbonate

Cold seeps, where seepage of hydrocarbon-rich fluids occurs in the sea floor, are sites that harbor highly specialized ecosystems associated with distinctive carbonate sediments. Although their Mesozoic record is scarce and patchy, it commonly includes dimerelloid rhynchonellide brachiopods. Here we report a monospecific assemblage of Anarhynchia from a limestone boulder of early Pliensbachian (Early Jurassic) age in the Inklin Formation of the Whitehorse Trough in the Stikine terrane, from a locality at Atlin Lake in northern British Columbia. Specimens are among the largest known Mesozoic brachiopods, up to 9 cm in length, and described here as Anarhynchia smithi n. sp. Early precipitated carbonate cement phases of the limestone have carbon isotopic composition highly depleted in 13C, indicative of the influence of microbial oxidation of methane derived from a cold seep. Carbonate petrography of the banded-fibrous cement and other characteristic components supports this paleoenvironmental inference. Volcanogenic detrital grains in the matrix are indistinguishable from those in the sandstone layers in the siliciclastic sequence, suggesting that the seep carbonate is broadly coeval with the enclosing conglomerate. The new record extends the geographic range and species-level diversity of the genus, but supports its endemism to the East Pacific and membership in chemosynthesis-based ecosystems. The distribution of three distinct but congeneric species suggests that allopatric speciation occurred at separate sites along the active margin of western North America and Anarhynchia was restricted to seep and vent habitats in the Early Jurassic.

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