An age model is born...

Finally with the calibrated age we created an age model for one of the cores (HOLCAR03).

The deepest sample we dated was more than 40 ka (thousand) years old. As the core is almost 2 m long, we will have to use a different method to date the lowest part of it. Probably we'll use the oxygen isotopic composition of multiple samples of planktic foraminifera to create a curve that can be correlated with other paleorecords that have been dated using the U/Th series in coral samples. This way we'll be able to assigned dates to those sediments older than 60 ka.

Calibration

For the AMS 14C analyses, our samples were sent to the NationalIsotope Centre of the Institute of Geological and Nuclear Sciences Ltd (GNSScience) in New Zealand.

The resulting dates correspond uncalibrated years Before Present (BP). An uncalibrated BP date cannot be used directly as a calendar date, because the level of atmospheric 14C has not been constant during the past 60000 years, as the level of 14C is affected by variations in the cosmic ray intensity due to variations in the Earth's magnetosphere.

To calibrate our dates we used the software CalibRev 6.0 (Stuiverand Reimer, 1993) choosing the MARINE09 calibration data set. We also have to determine a reservoir age, this means to establish how old was the carbon of the water before it was integrated in the carbonate that formed the shells of the foraminifera. We choose a 400 years reservoir age and we keep it constant along the entire core.