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Considering the complexity of the
EMED, we validate the use of Sr/Ca ratios
as productivity proxy and unravel
the varied processes which may influence
it. We examined the relationship
between the seasonal peaks in export
fluxes and the Sr/Ca ratio in coccoliths
of three upper photic zone coccolithophores
species collected in the traps,
Calcidiscus leptoporus, Helicosphaera
carteri and Emiliania huxleyi. We aimed
at testing whether high export fluxes are
correlated with high Sr/Ca ratios, suggestive
of higher nutrient-stimulated
production, or Sr/Ca ratios are unchanged
during high export periods,
suggestive of increased export efficiency
or scavenging. Periods of enhanced trap
fluxes in March and June result from
surface water blooms recognized in satellite
imagery. An additional peak flux
was found in January, but this peak
represents re-suspended or recycled material
in the water column.
The amplitude of seasonal variations
in the Sr/Ca ratios of the three investigated
species is small in both traps. In
the shallow trap, a decrease in the Sr/Ca
ratio of C. leptoporus occurred synchronously
with minimal fluxes. The other
two species were not measured for this
period. In the deep trap, no such decrease
in Sr/Ca was observed during
minimal fluxes, in either C. leptoporus
or H. carteri, probably due to a long
residence of coccoliths in the water column,
recycling and low export efficiency.
Absolute Sr/Ca ratios for all species
are lower than in other more productive
environments like the Bay of
Bengal, Arabian Sea, or Sargasso Sea.
We conclude that Sr/Ca ratios in coccoliths
of surface sediments in the EMED
reflect mainly spring–summer bloom
conditions averaged over hundreds to
thousands of years.
In addition, the origin of varying calcite
thickness in H. carteri was investigated.
The similarity of average Sr/Ca
ratios in differently-calcified specimens
confirms that coccolith thickness variations
in this species result from primary
biomineralization processes and not
from variable overgrowth by (low Sr)
abiogenic calcite in the water column or
the sediments.
2010010103
横 贯 阿 尔 泰 山 戈 壁 沙 漠 ( 蒙 古 ) 晚 古
新 世 轮 藻 = Charophytes from the Upper
Paleocene of the Trans-Altai Gobi
Desert (Mongolia). ( 英 文 ). Gereltsetseg
L. Paleontological Journal, 2009, 43(6):
699-701 1 图 版 .
Charophyte assemblage is described
from the Naran Member of the Tsagaan
sair section (Upper Paleocene). A new
species, Mesochara cornuta, is described.
2010010104
西 伯 利 亚 二 叠 三 叠 纪 暗 色 玄 武 岩 地 层
中 的 细 菌 化 石 = Fossil bacteria from
the Permotriassic Trappean strata of Siberia.
( 英 文 ). Astafieva M M; Rozanov
A Yu; Sadovnikov G N; Sapova E V.
Paleontological Journal, 2009, 43(8):
896-904 6 图 版 .
The strata of the Permotriassic Trappean
Complex of Siberia (Ilimpeya
River and Kapchan locality) are studied.
The water-lava and water-tuff boundaries
are shown to be promising for bacterial
paleontological studies. The analysis
of fossilized microbial communities
shows that they vary depending on
sedimentation conditions. This example
is important for a better understanding
of the prospects for the study of similar
situations in the Archean and Proterozoic.
2010010105
卡 累 利 阿 太 古 代 的 细 菌 古 生 物 学 研 究
= Bacterial Paleontological study of Archaean
of Karelia. ( 英 文 ). Astafieva M
M; Rozanov A Yu. Paleontological
Journal, 2009, 43(8): 905-910 8 图 版 .
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