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.