Validation of deep-sea back (Leiopathes sp.) coral from the Gulf of Mexico and Southeastern United States. Developed a novel dating method using a trace element (iodine) to determine the life spans and growth rates of deep-sea corals. Calculated reservoir ages using the iodine developed chronology and radiocarbon analyses for the Gulf of Mexico and Southeastern United States.

1. GE G Climate Science Lab
Leslye Mitty Mohon
Department of Geography, Texas A&M University
“Validating annual growth bands of deep
sea black corals and calculating
ocean ventilation ages from the Gulf of
Mexico and Southeastern United
States”

2. Outline
• Introduction
• Objective
• Background
• Research Design
• Significance/Conclusion
O&M Building at Texas A&M University

3. Introduction of Deep Sea Corals
• Deep sea corals are only beginning to be used as a paleoclimate archive that can
extend our observation of ocean dynamics and climate well beyond instrumental
records.
• The main methods for radiometric dating are 210Pb, radiocarbon, and Uranium-
Thorium (U/Th)
• Deep sea corals can be found between 30 to 6,000 meters depth
• Can be 500 to 40,000 years old
• Provide habitat for many marine organisms
especially important commercial fish and
endangered species.
• Deep sea black corals grow in a tree-like
fashion and form annual growth rings that
can produce paleoceanographic records.
• Deep sea black corals can be used to
calculate ventilation ages of deep water
masses.
Prouty et al. 2011 and Roark et al. 2006

4. Study Site
• My two study sites are (marked with red “X”) the Gulf of Mexico and
Southeastern United Stated (SEUS).
Druffel et al. 2008

5. Research Question and Corals
By validating independent age and growth rates
estimates of deep sea black corals, what are the
radiocarbon derived ocean ventilation ages in the Gulf
of Mexico and SEUS?

6. Objectives
• Objective 1: Validate the age, life spans, and growth
rates of black corals using visual ring counts and
scanning electron microscope (SEM) analysis (e.g.
Images) and comparing them to radiocarbon ages.

7. Objectives
• Objective 1: Validate the age, life spans, and growth rates of black
corals using visual ring counts and scanning electron microscope (SEM)
analysis (e.g. Images) and comparing them to radiocarbon ages.
• Objective 2: Developing ocean ventilation records
from the Gulf of Mexico and SEUS using radiocarbon
analyses.

8. Objectives
• Objective 1: Validate the age, life spans, and growth rates of
black corals using visual ring counts and scanning electron
microscope (SEM) analysis (e.g. Images) and comparing them to
radiocarbon ages.
• Objective 2: Developing ocean ventilation records from the Gulf
of Mexico and SEUS using radiocarbon analyses.
• Objective 3: Using U/Th dating method as an
independent chronology to validate coral and ocean
ventilation ages

9. Background
Knowns
 Black corals are the longest
living corals.
 Corals produce decadally and
perhaps annually resolved
paleoceanographic records.
 210Pb, Radiocarbon, and U/Th
has been used to calculate
growth rates and ages of
corals.
 Compared to radiocarbon and
210Pb, U/Th dating method is
more accurate and can date
corals up 500,000 years old.
Gaps
 Are growth band annual in black
corals?
 Can Iodine be used to identify
annual growth bands in black
corals?
 What are the growth rates and
ages of black corals?
 What are the ocean ventilation
ages in the GOM and SEUS?
 Lack of knowledge of black corals
from the Gulf of Mexico and SEUS.

10. Background
GAP
Can Iodine be used to
identify annual growth
bands in black corals?
Nowak et al. 2009

11. Research Design
Prouty et al. 2011
Objective 1: Validate the age, life spans, and growth rates of black corals using visual ring counts and scanning electron
microscope (SEM) analysis (e.g. Images) and comparing them to radiocarbon ages

12. Research Design
• By projecting paleo-Δ14C values back in time to their intersection with
atmospheric record, the residence time or ventilation age of deep water masses
may be calculated. This can get complicated by the mixing of multiple water
masses with different convection histories (Hillaire-Marcel and Vernal 2007).
• By developing chronometers, equivalent to radiocarbon as a tracer, it is possible
to reconstruct ventilation ages in different oceans as far back as the Last Glacial
Maximum (Robinson et al. 2005).
Objective 2: Developing ocean ventilation records from the Gulf of Mexico and SEUS using
radiocarbon analyses.

13. Research Design
• U/Th has an advantage over radiocarbon dating besides accuracy.
 U/Th dating can be used to date objects up to 500,000 years old, while 14C is
good for only a few tens of thousands of years at best.
 U/Th can be used as independent chronometer, and pairing the result to
radiocarbon measurement, to reconstruct ventilation histories in different oceans
(Robinson et al. 2005).
• Measuring U/Th is done by calculating an age from the degree to which
equilibrium has been restored between the radioactive isotope thorium-230
and its radioactive parent uranium-234 within a sample.
• The thorium-230 is itself radioactive with a half-life of 75,000 years
Objective 3: Using Uranium-Thorium (U/Th) dating method as an independent chronology to validate coral
and ocean ventilation ages

14. Significance
Value to Society
 Help understand ocean and
atmospheric processes to
possibly make future
climatic predictions.
 Conservation of corals that
provide habitat to
commercially important fish
and endangered species.
 Minimize human impacts
(e.g. bottom trawling and
jewelry trade).
New Information:
 Validating Ages and
growth rates of black
Corals
 Iodine analysis
 U/Th Dating
• Ocean Ventilation Ages…
 How ocean circulations
have changed in the past
 Learn more about biological
processes in the deep
ocean.
 Past CO2 cycling in the
atmosphere and oceans

15. THE END
QUESTIONS OR SUGGERSTIONS?