Mary Immaculate College
Research Showcase
Late Quaternary Investigation of
Planktonic Foraminiferal Assemblages
from the Western Mediterranean Sea
Dr. Angela Hayes, Dr. Teresa Broggy and Prof. Michal Kucera
Research Area: The Mediterranean Sea
The Late Quaternary
Planktonic Foraminifera
(from Coloma et al., 2005)
Non-spinose
Protozoa
Spinose
Biogeographic
Regions
(from Kucera, 2007)
Globorotalia truncatulinoides
Dextral
Sinistral
Transitional
Subtropical
Tropical
Ericson et al., 1954
Genetic Diversity
De Vargas et al. (2001)
Ujiie and Lipps (2009)
Distribution of G.
truncatulinoides
(Type 2)
Pujol and Vergnaud-Grazzini, 1995
Core Locations
Methodology


All samples were dried at 40 °C, disaggregated
in demineralised water and wet sieved through
a 63 µm mesh before drying. Finally, samples
were dry sieved through a 150 µm mesh. Using
a random splitter, were possible, 100
specimens of G. truncatulinoides were counted
to obtain a coiling record for each core.
16 radiocarbon dates
Results
It’s all about the Thermocline!
Assumptions

Occurrence of G. truncatulinoides is governed by the
stability of the water column (mixed or stratified).
Winter convective overturning facilitates the
transference of both nutrients and juvenile
populations of G. truncatulinoides into the surface
waters where maximum abundances of the species
develop.

Observed variation in coiling, appears to be related
to the depth/presence of the thermocline.
Dominant dextral populations tend to coincide with
overall lower abundances of G. truncatulinoides
possibly a residual population associated with
increased stratification of the water column. The
effects of SSTs are a potential secondary factor.
Phase 2:
Characterised by the near absence of G.
truncatulinoides from the faunal record .
The absence of the species is attributed to
enhanced stratification of the water
column. The strong water stratification in
the western Mediterranean Sea at this
time could have developed due to the
Phase 1:
combined result of postglacial sea level
Characterised by low numbers
of G.
rise (and
subsequent reduction in sea
truncatulinoides both coiling
variants
surface
salinities) and increased
exist, but the sinistral variant
dominates
precipitation (and subsequent river
the faunal assemblage. runoff).
Suggests seasonal mixing in the water
column. However, the relatively low
Phase 3:
abundances and the presence of the
Significant increase in the abundances of
dextral coiling variant may imply
G. truncatulinoides corresponding with the
weakened vertical mixing associated with
end of the African Humid Period which
the formation of a shallow thermocline.
marks the transition from a more humid
climate to the semi-arid climate that
exists in the Mediterranean region today.
Modern day hydrographic conditions in
the western Mediterranean Sea support
the development of deep vertical mixing.
Significance of G. truncatulinoides in the
Western Mediterranean Sea
Conclusions

Recolonisation of G. truncatulinoides post
glaciation in the western Mediterranean Sea


The presence and absence of the species during the
Holocene suggests a sequence of hydrological events
associated with sea level rise.
Basin-wide temporal and spatial similarities of
recolonisation
Thank you 