Number of sedimentary samples obtained from different depth were studied using ⁵⁷Fe Mössbauer spectroscopy to identify iron phases in samples. These samples were collected from different test wells drilled in Jaisalmer petroliferous basin and also for each well the samples were collected from different depths. Aim of this study was to identify different iron phases and also to obtain information about crucial Fe²⁺/Fe³⁺ ratio in the organic rich sediments (source rocks). The Fe²⁺/Fe³⁺ ratio seems to be correlated with the environment of deposition in the sediments. The smaller value of Fe²⁺/Fe³⁺ ratio indicate poor reducing condition in the sediments which is not favourable for generation of oil/gas in a basin.