0000000000542006
AUTHOR
Dominic Papineau
Biogeochemical Cycling of Nitrogen on the Early Earth
Variations in the nitrogen isotope composition of ancient organic matter and associated sediments provide clues for the early evolution of Earth's atmosphere–ocean–biosphere system. In particular, large isotopic variations have been linked to the protracted oxygenation of Earth's atmosphere during the Precambrian. Important problems being investigated include the nature of the variations observed at specific times in Earth's history and the degree of preservation of ancient nitrogen biogeochemical signatures during diagenesis and metamorphism. Interpreting these records in Archean sedimentary environments and their possible implications for the evolution of Earth's early atmosphere, ocean, …
Interpretation of the nitrogen isotopic composition of Precambrian sedimentary rocks: Assumptions and perspectives
International audience; Nitrogen isotope compositions in sedimentary rocks (d(15)N(sed)) are routinely used for reconstructing Cenozoic N-biogeochemical cycling and are also being increasingly applied to understanding the evolution of ancient environments. Here we review the existing knowledge and rationale behind the use of d(15)N(sed) as a proxy for the Precambrian N-biogeochemical cycle with the aims of (i) identifying the major uncertainties that affect analyses and interpretation of nitrogen isotopes in ancient sedimentary rocks, (ii) developing a framework for interpreting the Precambrian d(15)N(sed) record, (iii) testing this framework against a database of Precambrian d(15)N(sed) va…
Carbon isotope geochemistry and geochronological constraints of the Neoproterozoic Sirohi Group from northwest India
a b s t r a c t The early Neoproterozoic carbonates of the Sirohi Group, northwestern India, were studied for geochronology as well as for oxygen and carbon isotopes across three different sections to understand their relationship with contemporaneous global events. New single zircon Pb-Pb evaporation data con- strain the age of the Sirohi Group between ca. 920 and ca. 820 Ma, though actual span for deposition of the carbonates may be little shorter taking into allowance the time for peneplanation. Narrow range in variation of 18O values is generally observed in the carbonate which is consistent with generally well-preserved original compositions. Two sections (SA and SS) out of the three t…