Do the large carbon isotopic excursions in terrestrial organic matter across Paleocene–Eocene boundary in India indicate intensification of tropical precipitation?

Subsurface mixing of seawater and terrestrial-borne meteoric waters on carbonate landscapes creates karst subterranean estuaries, an area of the coastal aquifer with poorly understood carbon cycling, ecosystem functioning, and impact on submarine groundwater discharge. Caves in karst platforms facilitate water and material exchange between the marine and terrestrial environments, and their internal sedimentation patterns document long-term environmental change. Sediment records from a flooded coastal cave in Cozumel Island (Mexico) document decreasing terrestrial organic matter (OM) deposition within the karst subterranean estuary over the last ∼1,000 years, with older sediment likely exported out of the cave by intense storm events. While stable carbon isotopic values (δ13Corg ranging from −22.5 to −27.1‰) and C:N ratios (ranging from 9.9 to 18.9) indicate that mangrove and other terrestrial detritus surrounding an inland sinkhole are the primarily sedimentary OM supply, an upcore decrease in bulk OM and enrichment of δ13Corg values are observed. These patterns suggest that a reduction in the local mangrove habitat decreased the terrestrial particulate OM input to the cave over time. The benthic foraminiferal community in basal core sediment have higher proportions of infaunal taxa (i.e., Bolivina) and Ammonia, and assemblages shift to increased miliolids and less infaunal taxa at the core-top sediment. The combined results suggest that a decrease in terrestrial OM through time had a concomitant impact on benthic meiofaunal habitats, potentially by impacting dissolved oxygen availability at the microhabitat scale or resource partitioning by foraminifera. The evidence presented here indicates that landscape and watershed level changes can impact ecosystem functioning within adjacent subterranean estuaries.

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GEOCHEMICAL AND COMPOUND SPECIFIC CARBON ISOTOPIC CHARACTERISATION OF FLUID INCLUSION OILS FROM THE OFFSHORE PERTH BASIN,WESTERN AUSTRALIA: IMPLICATIONS FOR RECOGNISING EFFECTIVE OIL SOURCE ROCKS

The APPEA Journal ◽

10.1071/aj03008 ◽

2004 ◽

Vol 44 (1) ◽

pp. 223 ◽

Cited By ~ 4

Author(s):

H. Volk ◽

S.C. George ◽

C.J. Boreham ◽

R.H. Kempton

Keyword(s):

Organic Matter ◽

Fluid Inclusion ◽

Source Rock ◽

Early Cretaceous ◽

Source Rocks ◽

Molecular Evidence ◽

Terrestrial Organic Matter ◽

Carbon Isotopic ◽

Oil Source ◽

Coal Measures

The molecular composition of fluid inclusion (FI) oils from Leander Reef–1, Houtman–1 and Gage Roads–2 provide evidence of the origin of palaeo-oil accumulations in the offshore Perth Basin. These data are complemented by compound specific isotope (CSI) profiles of n-alkanes for the Leander Reef–1 and Houtman–1 samples, which were acquired on purified n-alkane fractions gained by micro-fractionation of lean FI oil samples, showing the technical feasibility of this technique. The Leander Reef–1 FI oil from the top Carynginia Formation shares many biomarker similarities with oils from the Dongara and Yardarino oilfields, which have been correlated with the Early Triassic Kockatea Shale. The heavier isotopic values for the C15-C25 n-alkanes in the Leander Reef–1 FI oil indicate, however, that it is a mixture, and suggest that the main part of this oil (~90%) was sourced from the more terrestrial and isotopically heavier Early Permian Carynginia Formation or Irwin River Coal Measures. This insight would have been precluded when looking at molecular evidence alone. The Houtman–1 FI oil from the top Cattamarra Coal Measures (Middle Jurassic) was sourced from a clay-rich, low sulphur source rock with a significant input of terrestrial organic matter, deposited under oxic to sub-oxic conditions. Biomarkers suggest sourcing from a more prokaryotic-dominated facies than for the other FI oils, possibly a saline lagoon. The Houtman–1 FI oil δ13C CSI n-alkane data are similar to those acquired on the Walyering–2 oil. Possible lacustrine sources may exist in the Early Jurassic Eneabba Formation and are present in the Late Jurassic Yarragadee Formation. The low maturity Gage Roads–2 FI oil from the Carnac Formation (Early Cretaceous) was derived from a strongly terrestrial, non-marine source rock containing a high proportion of Araucariacean-type conifer organic matter. It has some geochemical differences to the presently reservoired oil in Gage Roads–1, and was probably sourced from the Early Cretaceous Parmelia Formation.

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Nitrogen and carbon isotopic composition of marine and terrestrial organic matter in Arctic Ocean sediments:

Deep Sea Research Part I Oceanographic Research Papers ◽

10.1016/s0967-0637(00)00069-8 ◽

2001 ◽

Vol 48 (3) ◽

pp. 789-810 ◽

Cited By ~ 264

Author(s):

Carsten J. Schubert ◽

Stephen E. Calvert

Keyword(s):

Organic Matter ◽

Isotopic Composition ◽

Arctic Ocean ◽

Carbon Isotopic Composition ◽

Terrestrial Organic Matter ◽

Carbon Isotopic

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The Paleozoic to Mesozoic carbon cycle revisited: The carbon isotopic composition of terrestrial organic matter

Geochemistry Geophysics Geosystems ◽

10.1029/2003gc000555 ◽

2003 ◽

Vol 4 (10) ◽

Cited By ~ 33

Author(s):

Harald Strauss ◽

Wolfgang Peters-Kottig

Keyword(s):

Organic Matter ◽

Carbon Cycle ◽

Isotopic Composition ◽

Carbon Isotopic Composition ◽

Terrestrial Organic Matter ◽

Carbon Isotopic

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Origin and Alteration of Organic Matter in Hydrate-Bearing Sediments of the Rio Grande Cone, Brazil: Evidence from Biological, Physical, and Chemical Factors

Radiocarbon ◽

10.1017/rdc.2019.109 ◽

2019 ◽

Vol 62 (1) ◽

pp. 197-206 ◽

Cited By ~ 1

Author(s):

Luiz F Rodrigues ◽

Kita D Macario ◽

Roberto M Anjos ◽

João M M Ketzer ◽

Anderson J Maraschin ◽

...

Keyword(s):

Organic Matter ◽

Organic Carbon ◽

Sediment Cores ◽

Stable Carbon Isotope ◽

Carbon Isotopic Composition ◽

Rio Grande ◽

Terrestrial Organic Matter ◽

Carbon Isotopic ◽

Pelotas Basin ◽

Physical And Chemical

ABSTRACTThe Rio Grande Cone is a major fanlike depositional feature in the continental slope of the Pelotas Basin, Southern Brazil. Two representative sediment cores collected in the Cone area were retrieved using a piston core device. In this work, the organic matter (OM) in the sediments was characterized for a continental vs. marine origin using chemical proxies to help constrain the origin of gas in hydrates. The main contribution of OM was from marine organic carbon based on the stable carbon isotope (δ13C-org) and total organic carbon/total nitrogen ratio (TOC:TN) analyses. In addition, the 14C data showed important information about the origin of the OM and we suggest some factors that could modify the original organic matter and therefore mask the “real” 14C ages: (1) biological activity that could modify the carbon isotopic composition of bulk terrestrial organic matter values, (2) the existence of younger sediments from mass wasting deposits unconformably overlying older sediments, and (3) the deep-sediment-sourced methane contribution due to the input of “old” (>50 ka) organic compounds from migrating fluids.

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