*4.1. Lithological Description, Time Stratigraphic Framework, and Sedimentation Rates*

Lithologically, the study core contains a distinct organic-rich dark interval, divided into two separate sub-units (S1a and S1b respectively), representing the regional expression of the most recent sapropel S1 [87,88] (Figure 2a). From the bottom up to 87.5 cm, light gray clay can be observed (Munsell soil color 5Y 7/1). The following 24 cm are of gray color (5Y 5/1) and correspond to the lower sub-unit (S1a) of the sapropel. Between 63.5 cm and 52 cm light gray clay (5Y 7/1) can be observed, indicative of the sapropel interruption (S1i). From 52 cm to 40 cm mud of gray color (5Y 5/2) characterizes the upper sapropel sub-unit (S1b). The clay continues up to 13.5 cm with a light gray clay (5Y 7/1) color. From this point to the top of the core watery clay of light-yellow color (5Y 7/4) can be observed (Figure 2a).

δ δ **Figure 2.** (**a**) Lithologic log of core KIM-2A along with the total organic carbon (TOC) concentration and δ <sup>18</sup>O*G. ruber* and δ <sup>13</sup>C*G. ruber* isotope values; (**b**) time stratigraphic framework of the study core; blue triangles represent AMS <sup>14</sup>C datings, whereas red dots represent control points and bio-litho-stratigraphic horizons used as stratigraphic markers. The errors of AMS <sup>14</sup>C datings are also shown.

Chronology adopted in this study for core KIM-2A derived from a polynomial fit through the five AMS <sup>14</sup>C datings mentioned above, and the time markers correlative to the start and end of sapropel deposition, as well as the planktonic foraminiferal biozone Ia/Ib, Ib/Ic, Ic/II and II/III boundaries of [84] in the Mediterranean Sea (Table 1). The resulting age model is illustrated in Figure 2b and is consistent with the multi-proxy chronological framework of [37] for the Aegean sediment cores, thus supporting the robustness of our chronology. For the ages of the onset and termination of sapropel deposition, we have used the relevant ages from the nearby core NS-14 [7,16,17]. Additional control points related to the planktonic foraminiferal biozone boundaries were used for the age model construction, since they are useful chronologic standards for dating late Quaternary sequences in the central and eastern Mediterranean (including the Aegean Sea; [6,7,52,89] due to their Mediterranean-wide applicability and synchroneity [90–92].

Based on the relative abundances of the planktonic foraminifera species (Figure 3) the interval between 196 cm and 153 cm is characterized by the dominance of *N. pachyderma*, *T. quinqueloba*, *G. scitula* and *G. glutinata* with additional components the species *G. ruber* f. alba and *G. bulloides*. This glacial fauna corresponds to assemblage III and it has been recognized throughout the Mediterranean Sea (e.g., [6,52]). The interval between 153 cm and 109 cm corresponds to assemblage II and is characterized by high relative abundances of Neogloboquadrinids and *G. glutinata* and the presence of and *G. inflata*. In the lower part of this interval *G. ruber* f. rosea appears for the first time. Subzone Ic (109–40 cm) was identified by the warm subtropical species (*G. ruber* f. rosea, *G. siphonifera* gr. and *O. universa*). In addition it includes abundant *G. bulloides* and *G. rubescens* specimens. The sharp increase in the abundance of *G. inflata* at 41.5 cm is inferred to mark the onset of the Ib subzone. The Ia/Ib boundary (at 20 cm) is marked by the decrease of the latter species along with the decrease in the *N. pachyderma* abundance. In this core the Bioevent "Start of δ <sup>18</sup>Oruber depletion T1a" of [52], was also detected at 159 cm. δ

**Figure 3.** Frequency curves of the most indicative planktonic foraminiferal species in core KIM-2A. The dashed blue lines represent the Ia/Ib, Ib/Ic, Ic/II and II/III boundaries, whereas the gray bands the sapropel S1 sublayers respectively. X axes scales are of 80% and 20% corresponding to the high and low frequency abundances respectively.

According to our proposed age model (Figure 2b), the sedimentary horizons sampled in this study span the interval from the late glacial period, and the subsequent transition (Termination 1; T1) to the middle Holocene (Northgrippian stage) (i.e., ~5–22 ka BP). The average sedimentation rate is 11.86 cm/ka, and is in good agreement to those reported in the marginal Aegean basin [4,7,13,52]. These sedimentation rates were derived from the age model, assuming that the sediment accumulation has been moderately consistent throughout each interval. In particular, the average sedimentation rates are 8.10 cm/ka for the late glacial, 10.30 cm/ka for the Termination T1, and 16.46 cm/ka for the Holocene.
