Otolith accumulation rates (OAR) and fish family composition were analyzed throughout core M144 KC5-6, including Myctophidae, Sternoptychidae, Engraulidae, Gadidae, and Gonostomatidae, representing the most common taxa of the otolith record. A total number of 3272 otoliths has been classified. Otolith count and identification was performed on both cores A and B, with lower resolution between 0.5 cm and 151.5 cm, and highest resolution between 152.5 cm and 272.5 cm, using a binocular stereo microscope (magnification 10x – 20x) and a bifurcated illuminator. OAR was estimated by dividing raw otolith counts by dry bulk sediment mass, and further multiplied with sediment accumulation rate and dry bulk density of each sample and multiplied by ten. Identification of otoliths to the lowest taxonomic level is based on an automatic taxon identification software, web database, and otolith catalogs from the Mediterranean region. The predominance of the target families "Myctophidae, Engraulidae, and Sternoptychidae" comprising over 81% of the fossil assemblage, provides a robust dataset for analyzing their population dynamics over the last 11.4 kyr, to describe fish response to changing environmental conditions, before, during and after sapropel S1 deposition, as discussed in Pallacks et al. (in review).

Planktic foraminiferal accumulation rates (PFAR) were analyzed in Kasten Core M144 KC5-6, and a total of 108 samples were taken in a sample resolution of 2–4 cm. Around 250–300 specimens were taken from each sample, based on the >125 µm size fraction. PFAR were calculated based on planktic foraminifera abundance, linear sedimentation rate (LSR), and dry bulk sediment (DBS).

The dataset contains a downcore color scan of Kasten Core M144 KC5-6 for each 1cm. The analysis was performed onboard the R/V Meteor using a A MINOLTA CM-700d hand-held spectrophotometer combined with a CM-A178 target mask (Ø 8 mm, with plate). Color data were reported in the CIELAB space using the Lab* system. To calibrate the spectrophotometer, a Konica Minolta White Calibration Cap CM-A177 and Zero Calibration Box CM-A182 were used. Spectral reflectance was measured over a wavelength spectrum from 400 to 700 nm. Low L* and a* values representing darker, organic rich layers were defined sapropel phases as discussed in Pallacks et al. (in review).

The dataset contains an age-depth model, dry bulk density measurements and sedimentation rates for the Kasten Core M144 KC5-6, collected in the central western Aegean Sea (Eastern Mediterranean). Dry bulk density (DBD) was estimated for every 1cm sample slice, by dividing dry bulk sediment mass by sample volume. Sedimentation rates were calculated for each sample depth through the age-depth model, which is based on radiocarbon dating and Bayesian modelling. Eleven radiocarbon dates (14C) were taken along the 272 cm core, obtained from different depths. Planktic foraminifera (Globigerinoides ruber white) tests, isolated from the 250 to 315 µm fraction, were analysed, by using the accelerator mass spectrometry (AMS) at the NOSAMS facility at Woods Hole Oceanographic Institution. Considering the globally averaged mixed-layer reservoir age of ~400 yr., we calculated the age depth model through Bayesian statistics applying the R-code package rbacon (version 3.1.1) using the calibration curve Marine20 to transform 14C dates to calendar ages.