1. Redox Conditions in the Panthalassa Ocean at the Smithian-Spathian Boundary
Christian Olsen1, Alan Stebbins2, Robyn Hannigan2
1Earth and Environmental Studies, Montclair State University, 2School for the Environment, University of Massachusetts Boston
• Permian-Triassic Extinction1:
• Global warming
• Ocean acidification
• Ocean anoxia and euxinia
• Similar issues today
• 90% marine species extinct
• Smithian-Spathian Boundary1:
• 3 Million years after P-T
extinction
• Global cooling
• Potential for increased
oxygen availability
Introduction Problem & Hypothesis Statement
Problem:
Previous studies on the Sm-Sp boundary have focused on shallow marine
sediments1,2. The problem with these studies is that they examine shallow
coastal seas which are heavily influenced by runoff, isolation from ocean
currents and generally have lower dissolved oxygen levels and higher
temperatures than the open ocean.
Hypothesis:
Since the Jesmond Formation is in the Panthalassa open ocean we expect to
see more of a global signal recorded in the rock record. At Jesmond we expect
to see long-term oxic conditions with rare anoxic events.
Materials & Methods
• Trace element extraction4:
• Measure
• Acetic acid digestion
• ICP-MS measure trace
elements
• Pyrite Morphology2:
• SEM surveys
• No pyrite (oxic)
• Euhedral (oxic➟dysoxic)
• Framboidal (dysoxic➟ euxinic)
• Trace element proxies:
• Ce anomaly (Ce/Ce* < 1 oxic)
• Th/U (Th/U < 1 oxic)
Seawater Signatures and Contamination
• Seawater signatures5:
•Y/Ho > 36
•YbPAAS/NdPAAS > 1
•ΣREE ≈ 0.278
• Non-seawater signatures tend to contain higher whole rock Al contents.
• Non-seawater signatures generally preserve similar redox results except
for Th/U
Trends and Results
Redox Proxy Trend Notes
Th/U Oxic to suboxic Enriched samples may not reflect seawater chemistry
Pyrite Oxic to suboxic Lack of framboidal pyrite suggests no anoxic events
Ce/Ce* Oxic to suboxic Clearest redox trend
Redox Proxies Results
• Suggest primarily oxic conditions
• No large Ce anomaly and absence of framboidal pyrite
suggests no anoxic events
Discussion and Conclusion
 Our data shows a healthy open ocean with oxic conditions suggesting that
dysoxic and anoxic redox conditions in shallow seas are localized to those
environments while the overall marine environment is recovering
 Majority of marine biodiversity are coastal organisms and species diversity
would not fully recover until mid-Triassic7
 Global warming and hot temperatures could lead to more dysoxic events in
the isolated Paleo-Tethys with the larger Panthalssa oceans being more
oxygenated11
 More geochemical research is needed on the Jesmond section and
surviving Panthalassa ocean formations to piece together Sm-Sp
environmental conditions and global trends
Jesmond Formation Data and Shallow Sea Studies
Shallow seas data1,2 Jesmond
Redox conditions: oxic➟anoxic, rare euxinia Oxic➟suboxic
Temperature: Hot then cooling after the
Sm-Sp boundary
Suboxia at Sm-Sp possibly
due to extreme heat
Overall trends: Anoxic events at the
boundary
Oxic to suboxic conditions,
overall healthy ocean
Study Area: Jesmond Formation, a carbonate platform in the
Panthalassa Ocean currently located in British Columbia3.
Euhedral pyrite forms in anoxic sediment porewaters. Left and middle images are euhedral pyrites under
5 μm. Right image is framboidal pyrite. We did not find framboids in the Jesmond samples.
• We determined three trace element patterns to establish whether a sample
is likely to have preserved seawater signatures and thus redox chemistry
• Samples with non-seawater like signatures are less likely to preserve
accurate redox proxies
• We organized samples into confidence levels as shown
• Preserved seawater signatures (green)
• Moderately preserved seawater signatures (yellow)
• Little or no preserved seawater signatures (red)
“Princess” our ICP-MS on which we ran our acid
digested samples to extract trace element
concentrations.
Panthalassa
Ocean
Paleo-tethys
Ocean
Neo-tethys
Ocean
oxic oxic oxic
Sample Y/Ho Ybpaas/Ndpaas ΣREE Confidence
16-9 50.52 1.20 0.34 seawater signiture
9-14 44.29 0.84 0.35 some seawater signiture
17-2 35.00 0.78 0.55 little to no seawater signiture
[1] Zhang, L., et al 2015. Biogeosciences, 12(5), 1597-1613. [2] Sun, Y. D., et al. 2015.
Palaeogeography, Palaeoclimatology, Palaeoecology, 427, 62-78. [3] Johnston, S. T., & Borel, G.
D. 2007. Earth and Planetary Science Letters, 253(3), 415-428. [4 ]Nothdurft, L. D., et al., 2004.
Geochimica et Cosmochimica Acta, 68(2), 263-283. [5] Tostevin, R., et al., 2016. Chemical
Geology, 438, 146-162.
Acknowledgements and References
• Hannigan Lab Group and Dr. Tom Algeo for providing samples
• Environmental Analytical Facility (NSF Award # 09-42371)
• NSF for funding the CREST REU program
Scanning Eelctron Microscope
used to determine pyrite
morphology.