کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
6428780 | 1634756 | 2014 | 14 صفحه PDF | دانلود رایگان |
- Sedimentary facies associated δ13Corg was observed in the 'boring billion'.
- Stratified water column prevailed from latest Paleo- to Early Meso-proterozoic.
- The chemocline was located in very shallow water.
- Samples below the chemocline at different cratons have unique constant δ13Corg.
The Late Paleoproterozoic to Early Mesoproterozoic (from â¼1700 Ma to â¼1300 Ma) was highlighted by the assembly of the Nuna supercontinent, expansion of euxinic marine environments and apparent stasis in the diversity of eukaryotes. The isotopic composition of carbonate carbon (δ13Ccarb) was surprisingly constant during this interval, but little is known about the secular variation in the organic carbon isotopic composition (δ13Corg). Here we report δ13Corg data from the latest Paleoproterozoic (>1650 Ma) to Early Mesoproterozoic (â¼1300 Ma) succession in North China. The δ13Corg values range from â25â° to â34â°, and are dependent on sedimentary facies. In subtidal and deeper environments δ13Corg values are low and constant, ca. â32â°, but relatively enriched and more variable in shallower intertidal and supratidal environments. We attribute the facies-dependent variation in δ13Corg to the presence of a shallow chemocline. A probable result of a shallow chemocline is that it supported significant contributions of organic matter produced by chemoautotrophic and/or anaerobic photoautotrophic microbes in relatively deep environments from the latest Paleoproterozoic to Early Mesoproterozoic continental shelf of North China.
Journal: Earth and Planetary Science Letters - Volume 400, 15 August 2014, Pages 219-232