25th International Meeting on Organic Geochemistry IMOG 2011

P-484
Coupling of Miocene-Pliocene (7-5 Ma) African climate, surface
ocean temperature and marine organic carbon burial: highresolution,
multi-proxy records from the eastern equatorial
Atlantic (ODP 959)
Thomas Wagner, Olubunmi Eniola, Erin McClymont
Newcastle University, Newcastle upon Tyne, United Kingdom (corresponding
author:thomas.wagner@ncl.ac.uk)
The late Miocene to early Pliocene was a period of
major climate transition with events that impacted on
large-scale ocean and atmospheric circulation and
consequently global climate. Tectonic events such as
the Tibetan and Himalaya uplift and the closing of
ocean gateways are proposed to have caused a long
term cooling trend and a principal change in
vegetation in the low latitudes, including a general
shift from C3 vegetation to C4 vegetation in Africa
around 8-6 Ma 1 . Large-scale hydrological changes
are also recorded by carbon isotopic ratios in
carbonates and soil organic matter 2 .
With regard to the tropical Atlantic corridor the
establishment of modern type atmospheric and ocean
circulation at about 4.4-4.3 Ma 3 has been proposed.
Further studies on ODP 959 off tropical West Africa 4
showed that the late Miocene to early Pliocene
climate records were modulated by cyclic high
amplitude swings in TOC which were linked to the
evolution of African trade winds, continental upwelling
and eustatic sea level fluctuations. For these
sediments Norris 3 inferred cooling of surface waters
by 2-3°C (6.7-5.9 Ma) and proposed the onset of
modern type climate ocean dynamics ~4.4 Ma.
Here, we take these previous studies further and
present new complementary high-resolution (2.5 cm,
~2.5-5 kyr) records of sea-surface temperatures
(SSTs, alkenone derived U K 37‘), supply of terrestrial
organic matter (leaf wax lipids) and organic carbon
burial (TOC) for ODP Site 959. The complementary
new data provide, in combination with detailed
frequency analyses, new insights into the causal
relationships and trends between African climate,
marine response, and links with high latitude climate
forcing during the critical time interval 7-5 Ma. All
geochemical records show distinct high frequency
(millennial time scale) fluctuations that argue for a
highly dynamic and sensitive response of the tropical
Atlantic to African climate and orbital forcing. TOC is
low (in general