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doi:10.2204/iodp.proc.320321.207.2013
Data report: Monte Carlo correlation of sediment records from core and downhole log measurements
at Sites U1337 and U1338 (IODP Expedition 321)1
Alberto Malinverno2
Abstract
Site-to-site lithostratigraphic correlations are vital to building a composite record of equatorial Pacific sediment and constructing a common timescale. The work described here is aimed at establishing a detailed lithostratigraphic correlation between Sites U1337 and U1338 (Integrated Ocean Drilling Program Expedition 321) on the basis of high-resolution bulk density measurements from cores and downhole logs. Using both core and log measurements best constrains site-to-site correlations, but these two data types are measured on different depth scales. Reconciling these different depth scales requires a detailed correlation to precisely align the high-resolution core and log records at each site.
This study uses an automated Monte Carlo algorithm to align core and log records at the same site and to determine site-to-site correlations. The distinguishing feature of the method is that it does not produce a single optimal correlation, but rather a sample of possible correlations that give a good match. The average of the samples gives the best correlation, and their variability measures the uncertainty inherent to the correlation.
The Monte Carlo method is first applied to correlate core splice and downhole log data at each site, so that the data can be referred to the same depth scale. The resulting correlation is close to a uniform 11%–12% expansion of the composite core depth scale, but local differences up to several meters mean that a detailed correlation is necessary to match small-scale sedimentary features. Once the downhole log data are placed onto the core depth scale, consistent site-to-site correlations between Sites U1337 and U1338 are determined by matching core and log data.
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