## 4 Results
### Microstructural Analysis  
#### 4.2.1 Laminated Sections  
X-ray radiographs were composed for each core segment individually, and the mean HU value for each slice was extracted through SedCT software [86]. Colorized and grayscale images (Figure 3a) generated through the software reflect the interaction between the beam of gamma rays with the sediment and are highly dependable on the alternating density of non-laminated and laminated deposits. Sections with blue-based colors indicate lower HU values and thus lower density, whereas areas with more yellow/red colors indicate sections of more dense material (Figure 3a). HU values range from 400 to 700 for the laminated sequences and from 900 to 1400 for the non-laminated deposits.  
Since the mineralogical composition does not remain constant in all laminae, minor variations can be expected depending on the HU values; nevertheless, the distinction between the laminated and the non-laminated part can be easily obtained through the 3D model (Figure 3b). A two-scale approach was used for better visualization and distinct laminae counting. In larger-scale images, the mean HU value for all CaCO\({}_{3}\)-rich deposits was obtained by using INOBITEC medical software; thus, these sections (Figure 3b) were separated from the rest of the material. Visualization of the annual layers (curves) was enhanced by just focusing on regions of interest (ROI) (Figure 3c). Thickness/counting of each lamination can be then measured through the same software or by extracting 2D images from each section.  
The uCT data, when compared to the medical CT models, indicate an estimated error in lamination boundaries of around 0.5% since the resolution of both methods exceeds the minimum requirements for lamination distinction. The structural or \"sphere fitting\" thickness model (Figure 4) constructed through CTan plug-in software was compared to the rendered volume, for a more coherent distinction between laminations.  
Figure 3: (**a**) Representative 1 m core section with line scan image, HU color and grayscale model, and HU absolute values. (**b**) Varved section with HU values boundaries as they appear during 3D rendering. Laminated sections are presented with brown color and bulk non-laminated sediment with white color. (**c**) Magnified image of 3 distinct laminations. Calcium-rich laminations are presented with green color.  
The curve cycle in Vouliagmeni lake primarily consists of three distinct layers with variance in mineralogical composition, as indicated by the microscopic analysis. White carbonate laminae consist of aragonite and are deposited in dry summer conditions when evaporation in the lake water is high. Precipitation of coarser crystals, in the gray sublayer (Figure 4), is linked to the beginning of runoff events during autumn, reaching the maximum intensity in the dark, organic-rich laminae deposited during winter months. Minerogenic grains like quartz and calcite, mixed with organic residues, are the main components of the dark laminae. Laminae mineralogical composition and absence/presence of laminae are strongly connected to the precipitation/evaporation regime in the lake; thus, the curves of the Lake Vouliagmeni are characterized as endogenic.  
Figure 4: Representative section (core depth: 190–195.5 cm) of μCT analysis presenting the 3D rendered volume and structural thickness model. XRD results of the 8 samples analyzed were selected from white/calcite and brown/bulk laminations. Seasonal sublayers identified through the microscopic analysis are presented with a simplified stratigraphic column.