Varved lake sediments serve as a crucial archive for high-resolution paleoclimate and paleoenvironmental research. Owing to their interannual to even seasonal temporal resolution, they provide a high-precision chronological framework for climate reconstruction. Investigating the formation mechanism of varves is essential for understanding their depositional processes and for accurately interpreting the climatic and environmental information they record. This study focuses on the laminated sediments of Rena Co in the central Tibetan Plateau. By integratingS₂₁₀^Pb/₁₃₇^{Cs dating} with varve counting results, it confirms that these laminations are varves. Based on microscopic observations of varve thin sections, micro-X-ray fluorescence (μ-XRF) elemental mapping of varve thin sections, X-ray diffraction (XRD) analysis of core sediments, and scanning electron microscopy (SEM) observations of surface microtextures on coarse-grained particles, we systematically analyzed the structural, compositional, and morphological characteristics of the varves from Rena Co, and further explored their formation processes and underlying mechanisms. The results indicate that the varves of Rena Co consist of alternating light and dark layers. The light-colored layers form during summer and are mainly composed of fine-grained, Ca-rich authigenic carbonate (such as aragonite), together with abundant cladoceran fragments remains. In contrast, the dark-colored layers develop during winter following lake ice formation and comprise fine-grained, Fe-rich clay minerals that slowly settle beneath the ice, along with coarse-grained, Si-rich aeolian materials (e.g., quartz and feldspar) that accumulate on the ice surface and are subsequently deposited on the lakebed during ice melt.