Details

Autor(en) / Beteiligte

• OHKOUCHI, Naohiko
• KURODA, Junichiro
• TAIRA, Asahiko

Titel

The origin of Cretaceous black shales: a change in the surface ocean ecosystem and its triggers

Ist Teil von

• Proceedings of the Japan Academy, Series B, 2015/07/10, Vol.91(7), pp.273-291

Ort / Verlag

Japan: The Japan Academy

Erscheinungsjahr

2015

Link zum Volltext

Quelle

Free E-Journal (出版社公開部分のみ）

Beschreibungen/Notizen

• Black shale is dark-colored, organic-rich sediment, and there have been many episodes of black shale deposition over the history of the Earth. Black shales are source rocks for petroleum and natural gas, and thus are both geologically and economically important. Here, we review our recent progress in understanding of the surface ocean ecosystem during periods of carbonaceous sediment deposition, and the factors triggering black shale deposition. The stable nitrogen isotopic composition of geoporphyrins (geological derivatives of chlorophylls) strongly suggests that N2-fixation was a major process for nourishing the photoautotrophs. A symbiotic association between diatoms and cyanobacteria may have been a major primary producer during episodes of black shale deposition. The timing of black shale formation in the Cretaceous is strongly correlated with the emplacement of large igneous provinces such as the Ontong Java Plateau, suggesting that black shale deposition was ultimately induced by massive volcanic events. However, the process that connects these events remains to be solved.