This dataset contains 6 tables covering all analytical data for samples collected from the Anyue gas field, central Sichuan Basin, China. Table 1 includes major gas species and stable carbon and hydrogen isotopes. Table 2 includes results for methane clumped isotopes and calculated methane formation temperatures of gas samples. Table 3 includes noble gas concentrations. Table 4 includes noble gas isotopic ratios. Table 5 includes parameters used in methane emission model and calculating total volume of methane emission. Table 6 includes gas composition and stable carbon and hydrogen isotope characteristics of major gases produced in the pyrolysis experiments (thermally equilibrated methane between 400~500 in theory) and working reference gas, and their methane clumped isotope values.

Surface waters and shallow groundwater samples were collected by completely filling 30 mL polyethylene bottles, which were then sealed with electrical tape to minimise the risk of evaporative loss. Rainwater samples were integrated samples of total monthly rainfall collected in a specially-adapted rainfall collector following IAEA protocols (IAEA http://www-naweb.iaea.org/napc/ih/documents/userupdate/sampling.pdf [accessed 22 June 2012). Mexico, State of Yucatan. Yaal Chac (lake) (lake centre is Lat: 20.595274 degrees; Long: -89.711301 degrees), Abala Well (Lat: 20.649044 degrees; Long: -89.679814 degrees) and Xanil ha Cave (Lat: 20.650809 degrees; Long: -89.697426 degrees) Rainwater sampler was located adjacent to the lake. Refer to accompanying map for the precise location of the sampling sites.