Danube Delta Holds Answers to ‘Noah’s Flood’ Debate
- From: Jack Linthicum <jacklinthicum@xxxxxxxxxxxxx>
- Date: Fri, 23 Jan 2009 07:20:54 -0800 (PST)
Pictures as indicated below at the cite. Measurements of core samples
suggest a gradual infilling of the pre-existing "Black Lake" and a
near constant level of the Black Sea after the present levels had been
reached.
Danube Delta Holds Answers to ‘Noah’s Flood’ Debate
Published on 22 January 2009, 15:58
Did a catastrophic flood of biblical proportions drown the shores of
the Black Sea 9,500 years ago, wiping out early Neolithic settlements
around its perimeter? A geologist with the Woods Hole Oceanographic
Institution (WHOI) and two Romanian colleagues report in the January
issue of Quaternary Science Reviews that, if the flood occurred at
all, it was much smaller than previously proposed by other
researchers.
Liviu Giosan at work on a core in WHOI's McLean lab
Enlarge Image
Giosan and his colleagues used cores from the delta of the Danube
River, which empties into the Black Sea, to reconstruct sea level for
the Black Sea as far back as 10,000 years. Their work showed, if the
flood occurred at all, it was much smaller than previously proposed by
other researchers. (Tom Kleindinst, Woods Hole Oceanographic
Institution)
Using sediment cores from the delta of the Danube River, which empties
into the Black Sea, the researchers determined sea level was
approximately 30 meters below present levels—rather than the 80 meters
others hypothesized.
“We don’t see evidence for a catastrophic flood as others have
described,” said Liviu Giosan, a geologist in the WHOI Geology and
Geophysics Department.
Ten thousand years ago, at the end of the last glacial period, the
Black Sea was a lake—cut off from the Sea of Marmara and beyond it the
Mediterranean by the Bosphorus sill. Debate in geological and
archaeological circles has focused on whether, as glaciers melted and
global sea levels began to rise, the Bosphorus sill overflowed
gradually or whether a flood broke through the sill, drowning some
70,000 square kilometers and wiping out early Neolithic civilizations
in the region. In addition to questions about the rate of the flood,
investigators continue to debate the extent of the flood -- a debate
centered around what the level of the Black Sea was 9,500 years ago.
Black Sea 80 m below present sea level
Enlarge Image
Ten thousand years ago, at the end of the last glacial period, the
Black Sea was a lake, cut off from the Sea of Marmara and beyond it
the Mediterranean by the Bosphorus sill. Some researchers estimate
Black Sea level at that time was 80 meters below present day (their
hypothesized extent of the Black Lake at that level is represented by
dark blue water). They claim a flood 9,500 years ago brought sea level
to approximately 30 meters below present levels (the flooded area is
represented by light blue water). Such a flood would have inundated
70,000 square kilometers and wiped out early Neolithic civilizations
in the region. (Jack Cook, Woods Hole Oceanographic Institution)
In the late 1990s, Columbia University researchers Bill Ryan and
Walter Pitman examined the geological evidence and estimated the Black
Sea level at the time of the flood was approximately 80 meters lower
than present day levels. They suggested that the impact of a Black Sea
flood could have forced the movement of early agriculturist groups to
central Europe and established the story of Noah and his ark, as well
as flood myths among other peoples.
Black Sea 30 m below present day levels
Enlarge Image
Giosan and his colleagues estimate that the Black Sea was around 30
meters below present day levels (Black Lake is represented by dark
blue water) before a breach of the Bosporus sill 9,500 years ago
raised levels to a maximum of 20 meters |(the flooded area is
represented by light blue water). Their estimates mean that the
magnitude of the Black Sea flood was 5 or 10 meters but not 50 to 60
meters. (Jack Cook, Woods Hole Oceanographic Institution)
Black Sea Present Day Levels
Enlarge Image
The breach of the Bosporus sill connected the Black Sea to the Sea of
Marmara and the world ocean. As glaciers melted and global sea levels
began to rise, the Black Sea also rose, bringing it to its present day
level. (Jack Cook, Woods Hole Oceanographic Institution)
The source of the uncertainty fueling the Black Sea flood debate is
the difficulty of finding reliable sea level markers to date the
flood. “Sea level is like the Holy Grail,” said Giosan. “You can’t
really talk about a flood if you don’t know the exact levels of the
sea level in both the Black Sea and outside it in the Mediterranean.
And that’s what we tried to find.”
Scientists examine the geochemistry of sedimentary deposits for
evidence of fresh water fauna and the morphology of features on the
seafloor, trying to infer drowned beaches or wind-generated dunes, but
there are pitfalls associated with these indicators. Sediments are
subject to erosion by waves and currents, and sand deposits formed by
underwater currents can misleadingly be interpreted as dunes or
beaches. “Instead, what we use as indicators of sea level is the level
of the Danube River delta plain, an immense landform that cannot be
mistaken for something else,” Giosan stated.
A delta is formed when a river empties into a body of water. It dumps
sediments and builds a flat plain—the delta—that is within a couple of
meters of the shore and is, therefore, an indicator of sea level. In
2006, a team led by Liviu Giosan showed that contrary to Soviet-era
data suggesting large oscillations of Black Sea level, the development
phases of the Danube delta demonstrate that the level was more or less
as today in the last 6000 years.
To extend their record back in time beyond 6000 years, in 2007, Giosan
and his colleagues drilled a new core to 42 meters depth at the mouth
of the Danube River, the largest river emptying into the Black Sea.
Their goal was to reconstruct the history of that part of the delta—
before and after the flood—through an examination of the sediments. In
analyzing the delta sediment from the new core as well as others taken
in the region, Giosan’s team discovered fresh water deposits of the
newly forming delta dating back approximately 10,000 years,
subsequently overlaid by fine marine sediments, followed by the modern
delta deposits.
“It’s amazing,” said Giosan. “The early delta was forming in a fresh
water lake just a couple of hundred years before the flood. And after
the flood you have these marine deposits overlaying the whole delta
region.”
Using sediment cores to reconstruct the delta with accurate dates is
challenging. To attach a date to the layers of a core, scientists use
radiocarbon dating on the fossil shells of animals found in the core—
for instance, clams or snails. But in energetic areas, waves can erode
sediment on the seabed and heave up older shells, depositing them in
“younger” sediments. To address these concerns, Giosan and his team
used an approach that had not been used before in the Black Sea. They
employed high resolution dating performed at WHOI’s Accelerator Mass
Spectrometer (AMS) facility and only used “articulated” bivalves –
those where both sides of the shell were still attached as they are
when alive. The shells are held together by an organic substance that
degrades easily when they are dead, so the valves usually separate
when the animal dies. When bivalves are found intact, it means they
were not moved by waves and they are likely to be in situ.
Once the researchers dated and reconstructed the delta plain, they
could determine sea level for the Black Sea. They found that the Black
Sea level at the time of the flood was around 30 meters below present
levels. Determining how much water poured over the Bosphorus sill
remains problematic. There is no direct reconstruction of the sea
level for the Marmara, but, according to Giosan, indirect methods put
it at approximately 5 to 10 meters above the Black Sea level at the
time of the flood.
“So if this is true, it means that the magnitude of the Black Sea
flood was 5 or 10 meters but not 50 to 60 meters,” said Giosan.
“Still, having flooded the Black Sea by 5 meters can have important
effects, for example, drowning of the Danube Delta and putting an area
of 2,000 square kilometers of prime agricultural land underwater. This
has important implications for the archaeology and anthropology of
southern Europe, as well as on our understanding of how the unique
environment of the Black Sea formed.”
Funding for this project was provided by the WHOI Coastal Ocean
Institute.
http://insciences.org/article.php?article_id=1640
.
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