1. Stratigraphic Record of Oceanic Anoxic Events Andrea Ziegler Stratigraphy 12 April 2007

2. Anoxic? Oxygen depletion Multiple reasons: –Stagnation conditions –Density stratification –Organic material input –Strong thermoclines

3. Oceanic Anoxic Events (OAEs) Schlanger and Jenkyns, 1976 –Deep Sea Drilling Project from the Pacific Ocean –Black, carbon-rich shales –Same age as similar sediments from other localities –Represent unusual oceanic conditions

4. Lithographic Characteristics Black shales and mudstones Very thinly laminated Undisturbed Anomalous amounts of organic carbon Other significant isotopic anomalies

5. Causes of OAEs Change in ocean fertility –Increase in organic walled plankton/bacteria Expanded/intensified oxygen minimum zone Enhanced amounts of organic carbon is sediments *This hypothesis requires that there was a major climactic change on the global scale...

6. Possible Igneous Germination? Volcanic eruption –Huge volume of CO 2 released Rise in global temperature Increased weathering rates Increased fluvial nutrient flux Rise in organic productivity Increase in organic carbon burial

7. Mesozoic OAEs The Early Toarcian –183 mya Cenomanian-Turonian –93.5 mya

8. Cenomanian- Turonian OAE Early Toarcian OAE

9. Mesozoic OAEs in the grand scale

10. Specific Characteristics Span less than 0.5 million years (typical for OAEs) Proceeded by regional erosion and upwelling Early Toarcian –More concentrated organic matter –Hydrogen rich Cenomanian-Turonian –Less concentrated organic matter –Hydrogen poor

11. Conclusion Important for many reasons –Scientific: Paleoclimatology Paleontology Evolutionary Biology –Economic Petroleum/Natural Gas reserves