Estimation of primary productivity in the Toarcian tethys- A novel approach based on TOC, reduced sulphur and manganese contents

István Vetö, A. Demény, Ede Hertelendi, M. Hetényi

Research output: Contribution to journalArticle

42 Citations (Scopus)

Abstract

About 60 samples from the non-bioturbated Urkut Manganese Ore Formation (Bakony Mountains, Hungary), representing the early Toarcian anoxic event, were studied for: (1) TOC content, Rock-Eval parameters and kerogen δ13C; (2) S content and δ34S and (3) Al, Ca, Mn, Si and Ti contents. Using the example of the formation, a novel approach for estimating palcoproductivity is presented, taking into account reduced sulphur and manganese contents, which reflect the amount of organic carbon lost during early burial. Drastic changes in Mn content (between 0.7% and 37%) during deposition of the formation resulted in very variable early diegenetic processes, with sulphate reduction dominating in low-Mn sediments, and Mn reduction dominating in high-Mn sediments. The amounts of reduced sulphur and manganese allowed calculation of the original organic carbon (TOC(or)) content throughout the formation. Based on stratigraphic variations in chemical composition, changes in the rate of sedimentation were assessed for the three main members of the formation. Next, using the formula describing the relationship between measured productivity, rate of sedimentation and carbon flux reaching the seafloor, developed by Suess (1980), past productivity was calculated. The values obtained, lower than those prevailing in present-day upwelling systems, are probably underestimated because of uncertainties of chronostratigraphic and water-depth data. However, relative differences between productivity values obtained for the three members are considered as realistic and suggest an increase in productivity during deposition of the formation. This increase is not related to stratigraphic variations in Mn content and is accompanied by an increase in the growth of calcareous plankton.

Original languageEnglish
Pages (from-to)355-371
Number of pages17
JournalPalaeogeography, Palaeoclimatology, Palaeoecology
Volume132
Issue number1-4
DOIs
Publication statusPublished - Aug 1997

Fingerprint

Toarcian
Tethys
manganese
primary productivity
sulfur
productivity
carbon
sediments
organic carbon
sedimentation
Hungary
plankton
sulfates
kerogen
uncertainty
carbon flux
rocks
chemical composition
mountains
sediment

Keywords

  • Early diagenesis
  • Hungary
  • Kerogen
  • Manganese
  • Productivity
  • Toarcian

ASJC Scopus subject areas

  • Palaeontology

Cite this

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title = "Estimation of primary productivity in the Toarcian tethys- A novel approach based on TOC, reduced sulphur and manganese contents",
abstract = "About 60 samples from the non-bioturbated Urkut Manganese Ore Formation (Bakony Mountains, Hungary), representing the early Toarcian anoxic event, were studied for: (1) TOC content, Rock-Eval parameters and kerogen δ13C; (2) S content and δ34S and (3) Al, Ca, Mn, Si and Ti contents. Using the example of the formation, a novel approach for estimating palcoproductivity is presented, taking into account reduced sulphur and manganese contents, which reflect the amount of organic carbon lost during early burial. Drastic changes in Mn content (between 0.7{\%} and 37{\%}) during deposition of the formation resulted in very variable early diegenetic processes, with sulphate reduction dominating in low-Mn sediments, and Mn reduction dominating in high-Mn sediments. The amounts of reduced sulphur and manganese allowed calculation of the original organic carbon (TOC(or)) content throughout the formation. Based on stratigraphic variations in chemical composition, changes in the rate of sedimentation were assessed for the three main members of the formation. Next, using the formula describing the relationship between measured productivity, rate of sedimentation and carbon flux reaching the seafloor, developed by Suess (1980), past productivity was calculated. The values obtained, lower than those prevailing in present-day upwelling systems, are probably underestimated because of uncertainties of chronostratigraphic and water-depth data. However, relative differences between productivity values obtained for the three members are considered as realistic and suggest an increase in productivity during deposition of the formation. This increase is not related to stratigraphic variations in Mn content and is accompanied by an increase in the growth of calcareous plankton.",
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AU - Vetö, István

AU - Demény, A.

AU - Hertelendi, Ede

AU - Hetényi, M.

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