## 5 Discussion
### Overdispersion Analysis
#### 5.1.3 Burial Ages  
For sample Mero-7, most individual \(D_{e}s\) are within the 95% c.i. of the estimated CAM (Figure 3), providing a low \(OD\) value (13%). This is the sample with the lowest percentage (<10%) of aliquots rejected by trespassing saturation threshold (\(D_{e}>200\)Gy), although the calculated \(D_{e}\) from CAM, including or excluding these aliquots, are very similar [11]. Considering that there is no evidence of incomplete bleaching, the estimated burial age of 99 \(\pm\) 22 ka for this sample (Table 1) is assumed as reliable. This result is helpful in checking the other OSL ages based on their stratigraphic correlation (see relative heights in Figure 1), with the oldest deposits corresponding to those at the highest relative heights. Relative heights are measured with respect to the main channel of the Mero River. In cases where the paleochannel remains covered under the sea waters and its sediments, the geometrical calculation of the angle (\(\alpha\)) and the height (sin \(\alpha\)) between two outcrops of the same deposit (e.g., Mero-2 and Mero-3 in Figure 5a,b) is carried out [11]. This more logical estimate also coincides with the slope (tg \(\alpha\)) from the drainage divide to the bottom of the ria, adding the thickness of the sedimentary cover [54,55]. For the deposits located in the innermost area of the Ria de Coruna, the Mero-7 sample (99 \(\pm\) 22 ky) is located at +50 m (relative heights for all of them). Samples Mero-8 (85 \(\pm\) 12 ky) and Mero-5 (77 \(\pm\) 11 ky) are located at a +40 m, and Mero-1 (65 \(\pm\) 13 ky) is located at +30 m. In the outermost area of the ria, Mero-3 deposit (95 \(\pm\) 19 ky) is located at +100 m, while the correlative deposit of Mero-2 (59 \(\pm\) 8 ky) is located at +60 m (Figure 5a). All samples show chronological coherence. Mero-4 deposit (105 \(\pm\) 24 ky), located at +60 m, is correlative to another outcrop (Mero-x, undated) located at +120 m, probably older (Figure 5a). These ages fit the depositional age established for other continental deposits preserved on the Galician coast (Table 2). Such is the case of the alluvial deposits dated by OSL at the mouth of the Ulla River [2] (Figures 1 and 6), as well as the lower terrace levels of the Rio Mino (Figures 1 and 6), with minimum ages estimated by OSL and IRSL [1]; these latter data are also consistent with the different terrace levels dated by cosmogenic  
Figure 5: (a) Chronology of alluvial sediments from lower Mero River and relative heights from the main paleochannel. (b) Alluvial deposits from Peninsula de Sada tributaries (Mero4–Merox and Mero3–Mero2), with a sea level of \(-\)40 m below present sea level (bpsl), 110 ky ago. Mero-x: undated sample (most probably older than 120 ky) at 120 m (relative height). The triangles show the slope (tangent line) between samples and the bottom of the Ria de Coruna (then emerged) and represented by the hypothetical Mero river palaeo-channel. Elevation model and bathymetry from [53]. nuclides over 650 ky [1]. Finally, all these ages were also coherent with the coastal fluvial deposits dated by OSL on the north coast of Portugal [56,57] (Table 3). Within a palaeoclimatic context, these alluvial deposits were formed at the beginning of the marine regression of the Last Glacial episode (Upper Pleistocene). Throughout this \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Location** & **Formation** & **Age (ka)** & **Technique** & **Reference** \\ \hline Lower Mero River & & & & \\ (A Corüña, Galicia) & Alluvial & 128-51 & OSL & (this paper) \\ \hline Lower Ulla River & & & & \\ (Pontevedra, Galicia) & Alluvial & 92-37 & OSL & [2] \\ \hline Lower Mino River & & & & \\ (Pontevedra, Galicia) & Fluvial terraces & 57-27 & OSL & [1] \\ \hline Lower Neiva River & & & & \\ (North Portugal) & Fluvial & 90-40 & OSL & [56,57] \\ \hline \hline \end{tabular}
\end{table} 
Table 3: OSL and IRSL age ranges for coastal fluvial sediments on NW Iberian. Figure 6: Chronology of alluvial deposits in the lower Mero River and global climate record for the last 120 ky.