Publikationsdatum:
2018-08-10
Beschreibung:
During the 2007–2008 austral spring
season, the ANDRILL (Antarctic Drilling
project) Southern McMurdo Sound Project
recovered an 1138-m-long core, representing
the last 20 m.y. of glacial history. An extensive
downhole logging program was successfully
carried out. Due to drill hole conditions, logs
were collected in several passes from the total
depth at 1138.54 m below seafl oor (mbsf) to
230 mbsf. After data correction, several statistical
methods, such as factor analysis, cluster
analysis, box-and-whisker diagrams, and
cross-plots, were applied. The aim of these
analyses was to use detailed interpretation
of the downhole logs to obtain a description
of the lithologies and their specifi c physical
properties that is independent of the core
descriptions.
The sediments were grouped into the three
main facies, diamictite, mudstone and/or
siltstone, and sandstone, and the physical
properties of each were determined. Notable
fi ndings include the high natural radioactivity
values in sandstone and the high and low
magnetic susceptibility values in mudstone
and/or siltstone and in sandstone. A modifi
ed lithology cluster column was produced
on the basis of the downhole logs and statistical
analyses. It was possible to use the
uranium content in the downhole logs to
determine hiatuses and thus more accurately
place the estimated hiatuses. Using analyses
from current literature (geochemistry, clasts,
and clay minerals) in combination with the
downhole logs (cluster analysis), the depths
225 mbsf, 650 mbsf, 775 mbsf, and 900 mbsf
were identifi ed as boundaries of change in
sediment composition, provenance, and/or
environmental conditions. The main use of log
interpretation is the exact defi nition of lithological
boundaries and the modifi cation of
the paleoenvironmental interpretation.
Repository-Name:
EPIC Alfred Wegener Institut
Materialart:
Article
,
isiRev
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