SYMPOSIUM
Paleoecology
Saturday March 12:
10:20am-11:50am
Back to Concurrent Session
I
ABSTRACTS |
FORAMINIFERA FROM THE CERRO BANDURRIA
AND HORNITOS SECTIONS, MEJILLONES PENINSULA, NORTHERN
CHILE
Powell, J.A.1, S.E. Ishman1, H.G.
Wilke2
1 Department of Geology, Southern
Illinois University, Carbondale, IL 62901
2 Departamento de Ciencias Geológicas, Universidad
Cathólica del Norte, Antofagasta, Chile
A total of 28 marine sediment samples
were collected from the Cerro Bandurria and Hornitos
sections of coastal northern Chile for micropaleontological
analysis. The Neogene sediments at these sections
have had little or no previous biostratigraphic or
paleoenvironmental work. New information is provided
about the age and paleoenvironments of the sections
using foraminiferal data. The samples were processed
for benthic and planktonic foraminifera using standard
techniques. Statistical analyses, using Primer V.5,
of the benthic foraminiferal data was used to identify
biofacies and species assemblages. Planktonic foraminifera
were used for age determination of the sections. Three
benthic foraminiferal species assemblages and three
biofacies were identified at Cerro Bandurria. The
assemblages and biofacies indicate fluctuations in
sea-level suggested as a combination of global sea-level
eustacy and tectonic uplift. Five species assemblages
and four biofacies were identified at Hornitos. Planktonic
foraminifera identified at Hornitos provide an age
estimate of Early to Middle Pliocene (~ 5.1 to 2.8
m.y). The benthic foraminiferal biofacies at Hornitos
indicate a fall and rise in sea-level comparable to
global sea-level curve estimates.
Keywords: Foraminifera, Biofacies,
Northern Chile, Pliocene
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MODERN FORAMINIFERA AND INTERPRETION
OF HOLOCENE CLIMATE VARIABILITY OF THE ANTARCTIC PENINSULA
(Honorable mention!)
Szymcek, P.1, S.E. Ishman1, and S.D.
McCallum2
1Department of Geology, Southern
Illinois University, Carbondale, IL 62901
2Environmental Sciences Division, Oak Ridge National
Laboratory, Oak Ridge, TN 37831
Foraminifera have been widely used
as environmental proxies. The changing climate and
receding ice shelves of the Antarctic Peninsula have
prompted the use of these organisms as paleoecologic
indicators in this region. This study determined the
distribution of modern foraminifera from the Antarctic
Peninsula, and their associations to environmental
conditions. Statistical analyses of foraminiferal
data from sediment samples recovered from the eastern
and western continental margins of the Antarctic Peninsula
were performed upon either agglutinated or calcareous
foraminifera. Results of these analyses yielded statistically
distinct biofacies boundaries for both groups.
The biofacies boundaries of calcareous species show
strong associations with environmental factors, namely
glacial and water mass conditions. Water mass associations
with biofacies distributions include Ice Shelf Water,
Weddell Sea Transition Water, and Circumpolar Deep
Water. Close associations to productivity, current
energy and dissolution of calcium carbonate can also
be identified. Agglutinated biofacies boundaries are
gradational, and more weakly associated with environmental
conditions. This reflects the more general requirements
of agglutinated taxa described in this study.
The correlations between statistically determined
biofacies and environmental conditions show that foraminifera
are useful environmental indicators in this region.
By using surface distributions as analogs, Holocene
sedimentary records were interpreted with greater
insight, allowing aspects of the Antarcitc Peninsula’s
paleohistory to be revealed.
Keywords: Foraminifera, Antarctica,
Paleoecology, Biostatistics.
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SUBFOSSIL
WOOD: PALEO-POTENTIAL IN MIDWESTERN STREAMS
Stambaugh, M.C. and R.P. Guyette
Missouri Tree-Ring Laboratory, Dept.
of Forestry,
University of Missouri-Columbia, Columbia, MO 65211.
In light of climate change, paleo-climatological
data are of high importance. In Midwestern U.S. long-term
climate variability information are spatially and temporally
limited. Low-resolution pollen, speleothem, and archeological
time series provide some of our only Holocene period
climate clues. Temporally, these data are relatively
coarse in resolution (100 to 500 years) and rely on
the accuracy of 14C dating. The needs for long-term
and high-resolution climate variability data are of
particular importance in the Midwest where over 25 billion
dollars in agricultural products are grown annually
to support the global food economy. Dendrochronological
research of sub-fossil wood in Midwestern streams has
potential for providing added spatial coverage and annual
resolution climate information over the last 14000 years.
In this paper we describe the subfossil wood resource
for several Midwestern region streams, present climatological
analyses of a tree-ring record spanning the last 1000
years, and show preliminary results of Holocene climate
variability. The research potential of paleo-botanical
material from streams has been largely overlooked and
shows promise in disciplines spanning ecology, botany,
hydrology and climatology.
Keywords: tree-ring, dendrochronology,
paleoclimate, Holocene |
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MICROTOPOGRAPHIC
VARIATION IN POST-FIRE VEGETATION SUCCESSION OF TWO
ALBERTA BOGS
Benscoter, B.W.1, Vitt, D.H.1, and Wieder,
R.K.2
1Department of Plant Biology, Southern
Illinois University, Carbondale, IL 62901
2Department of Biology, Villanova University, Villanova,
PA 19085
Peatlands are landforms where organic
matter (peat) accumulates due to disproportional rates
of production and decomposition. Fire consumes an estimated
1,850 km2 of peatland annually in western Canada, altering
peatland composition and function. Post-fire vegetation
succession varies microtopographically, resulting in
species composition and peat accumulation differences
between high, dry hummocks and low, wet hollows. To
assess microtopographic vegetation succession variation
in two previously burned, Sphagnum-dominated,
western Canadian bogs, 10-cm diameter cores were collected
30-45 cm in depth from hummocks and hollows, respectively,
from each of 10 plots along a randomized transect. Assessments
of microtopographic variation and time since fire were
conducted at each plot. Cores were frozen and sectioned
at 1-cm intervals for macrofossil analysis. While all
hummocks followed a similar succession pathway from
lichen dominance immediately post-fire to monoculture
Sphagnum fuscum dominance, hollows were more
dynamic and diverse, representing mid-successional vegetation
communities. Hollows were more likely to propagate themselves
post-fire than hummocks, probably due to the greater
susceptibility to combustion in hollows and their early
successional status. Therefore, post-fire vegetation
successional trajectory is a function of the immediate
post-fire conditions, which can affect peatland function
and needs to be taken into account to make accurate
assessments of peatland C balance.
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III
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