 |
| Titel |
The importance of diazotrophic cyanobacteria as primary producers during Cretaceous Oceanic Anoxic Event 2 |
| VerfasserIn |
N. Ohkouchi, Y. Kashiyama, J. Kuroda, N. O. Ogawa, H. Kitazato |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1726-4170
|
| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 3, no. 4 ; Nr. 3, no. 4 (2006-10-26), S.467-478 |
| Datensatznummer |
250001159
|
| Publikation (Nr.) |
 copernicus.org/bg-3-467-2006.pdf |
|
|
|
|
|
| Zusammenfassung |
| In Livello Bonarelli black shale deposited during Cretaceous Oceanic Anoxic
Event 2 (OAE-2, ca. 94 Ma), nitrogen isotopic compositions of bulk sediments
are mostly in a narrow range from –2.7 to –0.7‰. We also determined
molecular distribution and nitrogen isotopic compositions of geoporphyrins
extracted from the black shale. The nitrogen isotopic compositions of
C32 Ni deoxophylloerythroetioporphyrin (DPEP) and total Ni porphyrins
are –3.5 and –3.3‰, respectively, leading us to the estimation that the mean
nitrogen isotopic composition of photoautotrophic cells were around
+1‰
during the formation of Bonarelli black shale. This value is suggestive of
N2-fixation, a dominant process for these photoautotrophs when
assimilating nitrogen. Furthermore, Ni-chelated C32 DPEP, derived
mainly from chlorophyll a had the highest concentration. Based on this
evidence, we conclude that diazotrophic cyanobacteria were major primary
producers during that time. Cyanobacteria may be key photoautotrophs during
the formation of black shale type sediments intermittently observed
throughout the later half of the Earth's history, and hence may have played
a crucial role in the evolution of geochemical cycles even in the later half
of the Earth's history. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|