993 resultados para 336.5
Resumo:
Fil: Banzato, Guillermo. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación; Argentina.
Resumo:
Fil: Banzato, Guillermo. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación; Argentina.
Resumo:
Fil: Banzato, Guillermo. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación; Argentina.
Resumo:
By analogy with the present-day ocean, primary productivity of paleoceans can be reconstructed using calculations based on content of organic carbon in sediments and their accumulation rates. Results of calculations based on published data show that primary productivity of organic carbon, mass of phosphorus involved in the process, and content of phosphorus in ocean waters were relatively stable during Cenozoic and Late Mesozoic. Prior to precipitation on the seafloor together with biogenic detritus, dissolved phosphorus could repeatedly be involved in the biogeochemical cycle. Therefore, only less than 0.1% of phosphorus is retained in bottom sediments. Bulk phosphorus accumulation rate in ocean sediments is partly consistent with calculated primary productivity. Some epochs of phosphate accumulation also coincide with maxima of primary productivity and minima of the fossilization coefficient of organic carbon. The latter fact can testify to episodes of acceleration of organic matter mineralization and release of phosphorus from sediments leading to increase in the phosphorus reserve in paleoceans and phosphate accumulation in some places.
