1. Use of Planktonic/Benthic Foraminiferal Ratios to Quantify Water Depth and Dissolution during the PETM from the Cambrian-Dorchester Core
Nicole Flynn
Senior Thesis: The Pennsylvania State University
Advisor: Timothy Bralower

2. Introduction: Paleocene Eocene Thermal Maximum (PETM)
Massive input
of isotopically depleted carbon
Methane clathrates in marine sediments on continental coasts
(Dickens et al., 1995)
3-4 permil negative shift in carbon isotope values
(Pagani et al., 2006; McInerney and Wing, 2011)
Oceanic temperature increase
Bottom waters: 4-5°C
(Kennett and Stott, 1991; Bralower et al., 1995)
Tropical surface waters: 5°C
High latitude surface waters: 9°C
(see compilation of Dunkley Jones et al., 2013)
The Paleocene Eocene Thermal Maximum is a global warming event from about 55 million years ago lasting approximately 170,000 years. This event has been extensively studied as it provides an excellent analog to understand global warming and the effects of massive carbon input to the ocean and atmosphere. This period is characteristic of a massive input of carbon 13 depleted carbon, possibly from methane hydrates in marine sediments on continental coasts, which led to a 3 to 4 negative shift in carbon isotope values. This input of carbon caused ocean temperatures to rise. Bottom waters increased by 4 to 5 degrees celsius, tropical waters increased by approximately 5 degrees celsius, and high latitude surface waters by about 9 degrees.

3. Introduction: Paleocene Eocene Thermal Maximum
Changes in carbon cycling, marine and terrestrial environments/ecosystems
Shoaling
(e. g., Colosimo et al., 2006, Petrizzo et l., 2007)
Lysocline
Depth where rate of calcite dissolution dramatically increases
Calcite Compensation Depth (CCD)
Depth where rate of calcite accumulation equals rate of calcite dissolution
Ocean acidification
(Doney, SC et at., 2009)
Decreased pH
Dissolution and reduced calcification of foraminifera
Carbon input and subsequent temperature rise led to many changes in both marine and terrestrial environments and ecosystems. When CO2 is dissolved in the ocean, it may react with water to form carbonic acid, which dissociates into carbonate and hydrogen. This decreases the pH of the ocean, increasing the requirement of carbonate ions to reach saturation, and thus increasing dissolution in calcifying organisms such as foraminifera. Increased saturation can lead to a rise, or shoaling, of the lysocline and calcite compensation depth, or CCD. The lysocline is depth where rate of calcite dissolution dramatically increases. The CCD is the depth where the rate of carbonate accumulation equals the rate of carbonate dissolution. Therefore, no calcite is deposited below the calcite compensation depth. Ocean acidification, as well as calcite compensation depth shoaling of up to 2 km, has been documented during the PETM.

4. Introduction: Sea Level
Sea level rise documented during PETM
(Zachos et al., 2005) (e.g., Sluijs et al., 2006, Sluijs et al., 2011)
Warming temperatures during PETM
Limited ice sheets
Minor rise due to melting of ice sheets
Thermal expansion
Increase in energy
Increase in bond length
Increase in volume
Sea level rise has also been documented during the PETM. There was limited ice during the period, so warming temperatures led to only minor melting of ice. Therefore, sea level rise was mainly due to thermal expansion. Thermal expansion occurs when an increase in energy, such as heat, excites atoms and leads to an increase in bond length, and a subsequent increase in volume.

5. Introduction: Foraminifera
Single-celled animals
Form test of CaCO3
Carbon isotope excursion from composition
Approximately 270,000 species (Haynes, 1981)
Benthic Planktonic
These environmental changes had a profound impact on foraminifera. Foraminfera are single-celled animals which form a test of calcium carbonate. This test is a good record of the environmental conditions at the time, and the carbon isotope excursion can be determined from the composition. Overall, there are approximately 270,000 species of foraminifera. The majority of species are benthic and live on the sea floor. There are also planktonic species which have evolved to float freely in the water column.

6. Introduction: Foraminifera Extinction
Benthic Foraminifera
Largest extinction in last 90 million years
50% species extinction
(e.g. Scheibner, 2005; Alegret, 2009).
Planktonic Foraminifera
Diversification
(Kelly et al., 1996)
Environmental changes during the PETM, including lowered oxygen levels in oceanic deep waters, led to the largest extinction of benthic foraminifera in the last 90 million years. Interestingly, planktonic foraminifera experienced a diversification.

7. Introduction: Cambrian-Dorchester (Cam-Dor)
August 2009
Dorchester County, Maryland
Coordinates: 38°N, 70°W
For my senior thesis, I studied the Cambrian-Dorchester, or Cam-Dor, core. The Cam-Dor core was drilled in August 2009 from the Dorchester County, Maryland airport. This google map image shows the location of the core, indicated by the red star, at approximately 38 degrees north and 70 degrees west.

8. ~753-749 ft. ~749-732 ft. Heavily bioturbated, glauconitic sand
The section of the core we sampled spans from to ft. This shows the bottom of the core, which contains heavily bioturbated, glauconitic sand. The contact was placed around ft, which is indicated in this image with a red star.
Heavily bioturbated, glauconitic sand
Paleocene- Aquia Formation glauconitic quartz sand
Eocene- Marlboro Clay Formation kaolinite rich clays

9. Clay, very fine sand, quartz with minor glauconite
~ ft.
~ ft.
The core transitions from glauconitic sand to clay with very fine sand, quartz, and just minor glauconite. The section of the core which I study in my senior thesis spans from to ft, so I will be studying the environmental changes after the onset of the PETM.
Clay, very fine sand, quartz with minor glauconite

10. Clay, faint bedding and bioturbation, sparse benthics
~ ft.
~ ft.
Further up in the core, faint bedding is apparent with bioturbation and sparse benthics.
Clay, faint bedding and bioturbation, sparse benthics

11. Sandy clay, heavily bioturbated, echinoid spines, oyster shell bed
~ ft.
~ ft.
The top of the core contains sandy clay, with heavy bioturbation, echinoid spines, and oyster shell beds.
Sandy clay, heavily bioturbated, echinoid spines, oyster shell bed

12. Introduction: Cam-Dor Cont.
Planktonic-Benthic ratios
Sea level
Fragmentation
Dissolution and turbulence
Quartz, pyrite, glauconite
Environmental changes
In this study, I look at planktonic/benthic ratios to quantify sea level, fragmentation to study dissolution and turbulence in the environment, and quartz, pyrite, and glauconite percentages to study environmental changes.

13. Introduction: Hypotheses
1. There will be an increase in P/B ratio following the Paleocene-Eocene boundary after the onset of the PETM 2. a. Deep ocean acidification will lead to increased fragmentation in both benthic and planktonic foraminifera, with particularly more fragmentation in planktonics at the base b. Turbulent shelf environment will lead to increased fragmentation in both planktonic and benthic foraminifera at the top 3. Quartz and glauconite percentages will increase with decreasing core depth and pyrite percentages will decrease with decreasing depth due to falling sea levels
I have three hypotheses. First, I hypothesize that there will be an increase in P/B ratio following the Paleocene-Eocene contact after the onset of the PETM due to an increase in sea level from thermal expansion and minor melting of ice. Second, oceanic acidification and a turbulent shelf environment will lead to increased fragmentation in both planktonic and benthic foraminifera. Finally, quartz and glauconite percentages will increase with decreasing core depth and pyrite percentages will decrease with decreasing depth due to falling sea levels

14. Methods: Retrieval 156 samples from Cam-Dor core
Distance between samples varied based on proximity to contact
Closer together if closer to contact
Stored in sealed plastic bags
To begin this project, 156 samples were collected from the Cam-Dor core. The distances between the samples varied based on proximity to the contact. Samples were taken closer together the closer they were to the contact. Samples were stored in sealed plastic bags and returned to Penn State.

15. Methods: Washing Process
75 washed purification
Sieved into 3 fractions: µm µm
>250 µm
µm fraction analyzed
75 of the 156 samples were washed to purify the foraminifera and separate from the clay and mineral particles. The washed samples were sieved into three fractions: micrometers, micrometers, and greater than 250 micrometers. The micrometer fraction was further analyzed.

16. Methods: Analysis and Identification
100 counts
Planktonic
Fragmented planktonic
Benthic
Fragmented
benthic
Percentages of
Pyrite
Glauconite
Quartz
The analysis involved doing 100 counts of planktonic and benthic foraminifera. This was done using 4 categories: planktonic, fragmented planktonic, benthic, and fragmented benthic. Therefore, benthics, planktics, fragmented benthics, and fragmented planktics were counted until the total reached This was done three times for each sample and the average was taken to insure accuracy. From these counts, both P/B ratio and percent fragmentation could be calculated. In addition, 100 counts were doe of glauconite, pyrite, and quartz, and percents of each were calculated.

17. Very little in five samples from:
ft.
Small decrease in two samples:
ft.
725.2 ft.

18. Missing from: 732.55 to 730.85 ft. Increase from: 730.35 to 722.5 ft.
Average: 1.6
Decrease from:
719.5 to
ft.
Average: 0.7
This is a plot of planktonic/benthic foraminifera ratio. The values on the right hand side are depth in feet, decreasing from bottom to top, and the values across the top are p/b ratio, decreasing from left to right. First of all, there a samples left out of the P/B ratio from To There were only a couple planktonic and benthic forams present in these samples, which is not enough to accurately calculate P/B ratio. There was not sufficient preservation during this interval, which is indication of a possible dissolution zone due to increased oceanic acidification. Next, there is a notable increase in P/B ratio following the contact from about 730 feet to 720 feet, indicating rising sea level during deposition. There is then an obvious decrease in P/B ratio from about 720 feet to the top of the core, indicating a decrease in sea level.

19. Slightly more fragmented planktonics than benthics at base
Benthic: blue
to ft: 19.4%
677.2 to ft: 62%
Planktonics: red
Average: 30.3%
Comparison
Slightly more fragmented
planktonics than benthics
at base
This is a plot of the quartz, pyrite, and glauconite percentages as a function of depth. There are elevated quartz and pyrite levels near the contact which show a gradual decrease to the top of the core. There is a lot low levels of glauconite near the contact and an extreme increase in percent glauconite near the top of the core. All of these factors are indication of falling sea level.

20. Quartz: blue Decrease Pyrite: red Decrease Glauconite: green Increase
This is a plot of percent fragmentation of benthic and planktonic foraminifera as a function of depth. There are not clear trends in planktonic foraminifera fragmentation. However, varying levels of fragmentation, as well as an overall moderate rate of preservation and fragmentation, indicate that there was turbulence in the environment during deposition. Benthic foraminifera, on the other, show an increase in fragmentation near the top of the core. Again, this could be due to increased turbulence with decreasing sea levels.

21. Discussion: P/B Ratio Rise in P/B ratio Decrease in P/B ratio
Dissolution zone missing planktonic and benthic foraminifera deep ocean acidification/rising CCD
Rise in P/B ratio
Increase in SL from
Highest P/B ratio: 3.8
79% of foraminifera planktonic
Highest SL at feet
Decrease in P/B ratio
Drop in SL as ocean water temperature decrease after PETM from to
Increase in benthic activity
First of all, it is possible that the dissolution zone was due to ocean acidification and decreased calcification. The rise in P/B ratio, with an average of 1.6 from to 722.5, indicated an increase in SL. The highest P/B ratio is 3.8, which indicates the highest SL occurred at feet. The decrease in P/B ratio, with an average of 0.7 from to feet, indicates a decrease in benthic activity due to a drop in SL as ocean water temperature decreases in recovery from the PETM.

22. Discussion: Fragmentation
Benthic Foraminifera
Planktonic Foraminifera
Bottom- Fragmentation due to dissolution
Top- Turbulence associated with decreasing sea levels
Increased fragmentation in planktonics at bottom due to dissolution
Planktonics more susceptible than benthics
Overall average: 30.3%
Benthic foraminifera dramatically increase from the lower part of the core to the upper. The average benthic fragmentation from to feet is 19.4 and the average from to feet is 62. The extreme increae in fragmentation may be associated with increased turbulence in the environment due to falling sea levels. Planktonic foraminifera, on the other hand, stay relatively constant in terms of percent fragmentation. The average percent is 30.3, which suggests moderate preservation. Planktonics float freely whereas benthics live on the seafloor, so turbulence could affect benthic foraminifera much more than it would for planktonics.

23. Discussion: Quartz, pyrite, glauconite
Disagrees with hypothesis
Due to relative glauconite percentages
Agrees with hypothesis
Decreasing pyrite
Decreasing SL corresponds with decrease in pyrite
Pyrite indicates eutrophication during PETM
Agrees with hypothesis
Return to continental shelf marine depositional environment
Quartz percentages disagree with my hypothesis. Instead of seeing increasing quartz with falling SL, I see increasing quartz. Pyrite, on the other hand, agrees with my hypothesis. Decreasing SL may correspond with decrease in pyrite due to increasing oxygen concentrations. Glauconite percentages also agree with my hypothesis. Increase in glauconite percentage near the top of the core could indicate a return to a continental shelf marine depositional environment.

24. Conclusions Dissolution Sea Level Fall
Massive carbon input lead to ocean acidification or shoaling CCD
Dissolution zone from to feet
Sea Level Fall
Fall in SL due to falling temperatures recovery
Fall in P/B ratio from to feet
Increased glauconite
Sea Level Rise
Rise in SL following the Paleocene-Eocene contact
Rise in P/B ratio from to feet
Increased pyrite- eutrophication
In conclusion, massive carbon input most likely lead to ocean acidification, leading to a dissolution zone from to feet. A rise in P/B ratio from to feet and increasing pyrite percentages indicate a rise in SL following the Paleocene-Eocene contact. Finally, a fall in P/B ratio from to feet an increasing glauconite indicate a fall in SL due to falling temperatures.

25. ? ? ?
Questions? ? ?