April 2016 - ECORD Newsletter # 26
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Paul Bridger, Sinéad Lyster and Abigail Hunt*
The discipline of palaeoceanography
provides an insight into past climates
and their applications to modern science.
Oceans are the predominant control
on climate and their associated climate
archives provide the best records of
palaeotemperature. Furthermore, oceans
provide the most extensive records, with
marine sediments documenting climatic
changes up to 200 Ma. They document
a much greater time span in comparison
to other climate archives, such as lake
sediments (<1 Ma), ice cores (<800 Ka),
and tree rings (<10 Ka). Ocean drilling
allows us to access these superior records.
As
geoscience
undergraduates
at
University College London, we have
had the opportunity to study Cenozoic
marine sediments and observe what is
arguably the most studied climatic event
in geological history. We were assigned a
replica of an ocean floor sediment core;
this core was retrieved on ODP Leg 208,
Site 1262 in the South Atlantic Ocean.
The core represents the Paleocene-Eocene
Thermal Maximum, which occurred ~55
Ma, as well as the climatic conditions
prior to, and succeeding, this event.
The
Paleocene-Eocene
Thermal
Maximum, or the PETM, was a
short climate interval whereby global
temperatures greatly increased at both
equatorial and polar latitudes (Zachos
et al., 2001; Zachos et al., 2003). This
climate event was a result of the rapid
release of ~2000 billion metric tons of
carbon into the atmosphere (Zachos et al.,
2005), causing widespread warming. This
carbon was likely released in the form of
methane, and is attributed to the melting
of methane hydrates stored in the ocean
floor (Thomas et al., 2002; Zachos et al.,
2005).
As part of the assignment, we observed
a clay-rich horizon within the core
- as inferred from
the presence of very
fine-grained
red
sediments
(right).
This horizon reflects
the warming-induced
ocean
acidification
that led to increased
carbonate dissolution,
therefore raising the
carbonate compensation
depth (CCD). The
absence of calcareous
nannofossils at this
horizon is in accordance
with a raised CCD.
Underlying the PETM
horizon, a carbonaterich nannofossil ooze
is visible. This same
lithology is repeated
above the horizon,
therefore demonstrating
a return to previous
conditions
following
the climate interval.
Being able to make Undergraduate students at University College London studying
observations
from a replica of an ocean floor sediment core in order to develop
primary data, such past climate interpretation skills (photo Prof. Bridget Wade,
as this core, allowed University College London).
us to develop our
trends facilitating understanding and
interpretative skills. To us as students,
interpretation of modern-day climatic
practicing these skills is more beneficial
patterns.
than studying articles whereby climate
proxy data has already been graphically
For further reading:
depicted and interpreted.
This exercise demonstrated the vast
opportunities that ocean drilling offers
to palaeoceanography. The emergence of
ocean drilling and associated technologies
has greatly advanced scientific research,
permitting access to an ever-expanding
climate archive and allowing scientists to
go further into deep geologic time. As a
result of ocean drilling, the Cenozoic is
the most thoroughly studied period of
geological history, with observed climate
*Department of Earth Sciences, University College London, Gower Street, London, WC1E 6BT, UK
paul.bridger.12@ucl.ac.uk, sinead.lyster.12@ucl.ac.uk, abigail.hunt.12@ucl.ac.uk
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Deep-Time Perspectives on Climate Change:
Marrying the Signal from Computer Models and
Biological Proxies, The Micropalaeontological
Society, Special Publications. The Geological
Society, London. 323-349.
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Program, Initial Reports, vol. 208, Ocean
Drilling Program, College Station, Texas.
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