High Contribution of Recalcitrant Organic Matter to DOC in a Japanese Oligotrophic Lake Revealed by 14C Measurements

Carbon isotopes (14C and 13C) of dissolved organic carbon (DOC) in a Japanese oligotrophic lake (Lake Towada) were measured to study the origin and cycling of dissolved organic matter (DOM) in Lake Towada. Lake water samples were collected at 3 depths (0, 30, and 80 or 85 m) during 4 months (April, June, August, and October) in 2006. 14C measurements of DOC were performed by accelerator mass spectrometry (AMS) at the National Institute for Environmental Studies (NIES-TERRA) in Japan. Δ14C and δ13C values of DOC in Lake Towada showed light carbon isotopic values ranging from –750 to −514‰ and –29.0 to –27.8‰, respectively. These values are similar to those of humic substances reported. The very low carbon isotopic values of DOC in Lake Towada suggest a very small contribution of DOC derived from fresh phytoplankton to the lake DOC. There is an extremely high linear relationship between the Δ14C and δ13C of DOC in Lake Towada when all data points are plotted (r2 =0.818, p < 0.01), suggesting that the DOC in Lake Towada has 2 specific sources contributing heavy and light carbon isotopes. Although the freshly produced DOC of phytoplankton origin can be decomposed easily, the variation in the autochthonous DOC should influence the carbon isotopic values of DOC in Lake Towada.

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CARBON ISOTOPES, KEROGEN TYPES AND THE PERMIAN-TRIASSIC BOUNDARY IN AUSTRALIA: IMPLICATIONS FOR EXPLORATION

The APPEA Journal ◽

10.1071/aj96028 ◽

1997 ◽

Vol 37 (1) ◽

pp. 472 ◽

Cited By ~ 27

Author(s):

C.B. Foster ◽

G.A. Logan ◽

R.E. Summons ◽

J.D. Gorter ◽

D.S. Edwards

Keyword(s):

Organic Matter ◽

Carbon Isotopes ◽

Secular Change ◽

Simple Relationship ◽

Predictive Tool ◽

Marine Fauna ◽

Isotopic Signatures ◽

Carbon Isotopic ◽

Eastern Australia ◽

Plant Microfossils

A global stratotype section for the boundary between the Permian and Triassic Systems is yet to be agreed internationally. However, in many parts of the world, there is evidence of massive extinction of marine fauna at or near the P-T boundary. In the absence of marine fauna, as is the case in most of Australia, changes in plant microfossils, in carbon isotopic signatures, and radiometric dates using SHRIMP, have been used to mark the boundary. The leading questions which arise from this are whether these events are synchronous and how they affect exploration.In eastern Australia, the top of the coal measures has been used as the top of the Permian, although presently only plant microfossils can be used to determine if the youngest seam is present. This has important economic consequences for determination of volumes of effective source rock and for estimates of coal-bed methane. It has been suggested that changes in the carbon isotopic signatures (δ13C) of either organic matter (δ13Corg) or carbonates (δ13Ccarb) can be used to delimit the P-T boundary. From studies of (δ13Ccarb data, Scholle (1995) concluded that 'the establishment of a secular variation curve which has enough detail and reliability to be used as a chemostratigraphic tool still lies in the future'. We concur, and demonstrate for organic carbon that, while there is evidence for secular change, the 13C signature is complicated and overprinted by contributions from different parent plant types; wood-dominated organics are typically −24 %o, while non-woody matter is significantly lighter (−30 %o). There is no simple relationship of δ13Corg to geological age. The consistency of our data, from both the east and west of Australia, allows us to construct a model to predict probable depositional and organic facies using either carbon isotopes (from kerogen or oil) or quantitative estimates of organic matter from standard palynlogical slides. This offers a novel and usefl predictive tool for hydrocarbon exploration.

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Carbon Isotopic Characteristics of Different Genetic Type Condensates in China

Energy Exploration & Exploitation ◽

10.1260/0144-5987.29.6.699 ◽

2011 ◽

Vol 29 (6) ◽

pp. 699-710 ◽

Cited By ~ 3

Author(s):

Shipeng Huang ◽

Zecheng Wang ◽

Xiaoqi Wu ◽

Fengrong Liao ◽

Jinxing Dai

Keyword(s):

Organic Matter ◽

Isotopic Composition ◽

Carbon Isotopes ◽

Organic Matters ◽

Total Hydrocarbon ◽

Carbon Isotopic ◽

Wide Range ◽

Different Types ◽

Organic Matter Type ◽

Petroliferous Basin

Condensate pools with reservoir ages of Ordovician, Permian, Triassic, Jurassic, Cretaceous, Eogene, and Neogene were found in every giant petroliferous Basin in China. Condensates generated by sapropelic organic matters (sapropelic condensates) are of high- to over-mature stages, while the maturities of those generated by humic organic matters (humic condensates) cover a wide range, from early mature to over-mature. Carbon isotopes of 143 condensate samples were analyzed in this work, and we found that both the organic matter type and the maturity significantly influenced the isotopic composition of the condensates. The total hydrocarbon isotopic values of the humic condensates range from −29.9% to −21.7%, with an average of −26.0% (94 samples), while those sapropelic condensates are lighter generally, covering a range of −33.9% to −26.0% with an average of −29.5% (40 samples). δ13Caromatics value is strongly inheritable to the organic matter type and it combined with the δ13Csaturates value can be used to distinguish condensates of different types. δ13Caromatics value of sapropelic condensate is less than −27.5%, while the δ13Caromatics and the δ13Csaturates values of humic condensate are larger than −27.5% and −29.5%, respectively.

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