Chemical weathering can occur on Earth and other rocky planets with liquid water on their surfaces. As the Curiosity Mission has revealed that fluvio-lacustrine depositional environments once prevailed in Gale Crater, investigation of sediment geochemistry to interpret chemical weathering history and the possible influence of climate fluctuation seems feasible on Mars. This study examines the relationship between temperature and the degree of weathering inferred from weathering indices, and applies the suitable weathering indices to a compilation of published datasets from Gale Crater sediment. The selected weathering indices (CIA, CIW, PIA, V, W, and WIP) consistently suggest an increase followed by a more gradual increase and decrease in weathering intensity up-section, which might reflect climate variations. However, diagenetic and/or hydrothermal alteration seem to have overprinted the primary weathering signature. In addition, the differing effectiveness of the ACN-K and M-F-W ternary compositional spaces in discerning small changes in source rock composition and the effects of post-depositional alteration is examined. The result of this study underscores the importance of employing multiple indices and compositional diagrams in future studies to reconstruct environmental conditions and the source-to-sink relationship, given the limited type and amount of data available from Mars sediments.