For the first time, Fe-57 Mossbauer spectroscopic investigation of deep subsurface sediments of Bikaner-Nagaur petroliferous basin (containing heavy viscous oil) is reported. In present investigation Mossbauer study was carried out on the samples of wells Lunkha-1 and Pinodha-1 collected from different depth interval. Our results show that Paleocene sedimentary sequence of this basin have appreciable presence of iron in clay, Jurassic sediments are rich in siderite. Majority of the samples from other formation do not show any Mossbauer signal, indicating very meager presence of iron, beyond the detection limit of Mssbauer Spectroscopy. But few of them indicated presence of iron, out of which many samples exhibit presence of hematite, signature of oxidizing condition in sediments. (C) 2012 Elsevier Ltd. All rights reserved.