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| Titel |
Climatic fluctuations during the Holocene based on eastern Mediterranean continental shelf sediment cores |
| VerfasserIn |
Tsofit Mor-Federman, Revital Bookman, Ahuva Almogi-Labin, Barak Herut |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250077534
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| Zusammenfassung |
| Sediments deposited on the south eastern Mediterranean continental shelf are sensitive
recorders of climatic and oceanographic variability affected by the north Atlantic and
indirectly by monsoonal systems. In order to reconstruct the influence of these climatic
systems two cores were taken off shore the southern and central Israeli coast at
water depths of ~35 m. The sediments were characterized by majors and traces
elements, and the sediment provenance was determined using 87Sr/86Sr ratios.
Detrital input from the Nile and local environment was studied using grain size
distribution and sedimentation rates. Water column productivity was inferred by TOC and
δ13Corg.
The cores, dated to 7,630 and 8,440 14C years BP, show two distinct sedimentation
regimes. The early Holocene is characterized by high sedimentation rates (190-140 cm/ka)
that decrease in the last 5,500 years (50-60 cm/ka) in both north and central cores. Coarse
grain size is dominant in the early Holocene, with a decreasing trend in the northern core.
This distribution is probably connected to eustatic sea level rise and recycling of coarse
sediments from the flooded shallow Nile cone. In the late Holocene, as sea level stabilized,
grain size is finer in the south; while to the north, cycles of ~1,500 years in coarse grain size
characterize the period.
Carbonate and organic carbon further present the change along the period. Decrease in
carbonate content and increase in δ13Corg during the late Holocene indicate decrease in
water column productivity. In contradiction, organic carbon is relatively high in the late
Holocene. This is explained by the coarse sediment texture in the early Holocene leading to
better oxidation of buried organic matter.
Strontium isotopes show changes in sediment provenance. In the early Holocene high
87Sr/86Sr values of ~0.71 reflect a dominant signature of the White Nile and the Yellow Nile
and in part the local streams. During the last 5,500 years lower values of ~0.7074 in the
southern core compared to ~0.7080 in the northern core, reflect a strong finger print of
the Blue Nile on the sediments adjacent to the Nile cone that rapidly disappear
northwards.
The changes in the geochemical and sedimentary proxies are connected to Holocene
climatic fluctuations. Change of provenances and decrease of fluvial input to the basin
and in water column productivity around 5,500 years BP occur simultaneously
with changes in the intensity of the monsoonal system over the headwaters of the
Nile. These changes, that are present both at southern and central inner shelf, can
be connected to the end of the African humid period. In the late Holocene, as the
influence of the Nile on the central part of the shelf decreases, the Mediterranean
climate system that originates in the northern hemisphere climate system is more
evident. Cycles of ~1,500 years of coarse sediments probably originating from
erosion in the coastal environment correlate with cold events known as the north
Atlantic Bond cycles. Our results show the potential of shelf sediments to record and
understand the control of climatic global systems on inner shelf sediment records. |
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