the upper cretaceous carbonate sequence of ab-deraz formation is well exposed in the kopet- dagh basin. this formation comprises marly limestone and three chalky limestone units. chalky limestone of ab-deraz formation is mainly composed of calcareous dinoflagellate (pithonellid calcispher), cocolithofore and planktonic foraminifera. carbon and oxygen stable isotopes analysis of the third chalky...

land cover change constitutes one of main way of alteration of soil organic matter in both quantitative and qualitative terms. the goal of this study was to compare the carbon stock and the isotopic signature of the organic matter in the soil of areas with different land use, covered with forest and grass (pasture). the study area is located at sorocaba, sp, brazil. using un-deformed soil sampl...

Negative carbon isotope excursions measured in marine and terrestrial substrates indicate large-scale changes in the global carbon cycle, yet terrestrial substrates characteristically record a larger-amplitude carbon isotope excursion than marine substrates for a single event. Here we reconcile this difference by accounting for the fundamental increase in carbon isotope fractionation by land pl...

INTRODUCTION ..................................................................................... 504 ISOTOPE EFFECTS ........................................................................... ’ ....... 504 ISOTOPIC OMPOSITION A D DISCRIMINATION ....................................... 505 Definitions .......................................................................................... 50...

Watershed-scale carbon budgets remain poorly understood, in part due to inadequate simulation tools to assess in-stream carbon fate and transport. A new numerical model termed ISOtope-based FLuvial Organic Carbon (ISOFLOC) is formulated to simulate the fluvial organic carbon budget in watersheds where hydrologic, sediment transport, and biogeochemical processes are coupled to control benthic an...

Estimates of terrestrial carbon isotope discrimination are useful to quantify the terrestrial carbon sink. Carbon isotope discrimination by terrestrial ecosystems may vary on seasonal and interannual time frames, because it is affected by processes (e.g. photosynthesis, stomatal conductance, and respiration) that respond to variable environmental conditions (e.g. air humidity, temperature, ligh...

A 1.5‰ to 2‰ carbon isotope excursion immediately above the clay layer that defines the Cretaceous-Tertiary (K/ T) boundary has been reported in marine sediments world wide. This paper reports a similar 1.5‰ to 2.8‰ carbon isotope excursion recorded by C3 land plants from three temporally-controlled, stratigraphically-constrained terrestrial sections in the Western Interior of North America (Ga...

Fossil-wood carbon-isotope data are presented for the Wessex Formation, a non-marine unit within the Lower Cretaceous (Valanginian–Barremian) Wealden Group of the Isle of Wight and Dorset, southern England. The carbon-isotope values have a range ( C c. 26.6 to 19.8‰) that is consistent with that expected for Mesozoic C3 plants. Consideration of the Isle of Wight fossil-wood carbon-isotope data ...

Carbon isotope fractionation during aerobic mineralization of 1, 2-dichloroethane (1,2-DCA) by Xanthobacter autotrophicus GJ10 was investigated. A strong enrichment of (13)C in residual 1,2-DCA was observed, with a mean fractionation factor alpha +/- standard deviation of 0.968 +/- 0.0013 to 0.973 +/- 0.0015. In addition, a large carbon isotope fractionation between biomass and inorganic carbon...