<p>Accurate 3D geological modeling of Quaternary deposits is crucial due to their inherently heterogeneous structures, such as clay-silt lenses, channels, and slope deposits. These small- to medium-scale features significantly influence geological engineering and resource evaluation but are challenging to reconstruct with limited borehole data. In this study, a synthetic explicit 3D geological reference model containing typical Quaternary structures was constructed using GOCAD^®. Borehole data were systematically extracted at varying densities using both regular and irregular sampling layouts and used to build implicit models through Leapfrog Geo™ software. Quantitative comparisons between the explicit and implicit models were conducted using Jaccard distance and normalized City-Block Distance metrics. The results demonstrate that as borehole density increases, the accuracy of the implicit models improves significantly, particularly in capturing small-scale structures such as lenses and narrow channels. Meanwhile, the influence of sampling layout remains comparatively minor. The study identifies a critical borehole density threshold required to reliably reconstruct complex geological features, providing quantitative measures for optimizing borehole exploration strategies in Quaternary geological settings.</p>