Mineralogy and Genesis of Ironstone Ooids, Subathu Formation (Eocene) in the Tal Valley, Garhwal Himalaya

The physico-chemical and X-ray diffraction analysis of the oolitic ironstone belonging to the lower part of the Subalhu Formation (Eocene) reveal the presence of major berthierine and chamosite with minor amounts of hematite, limonite and rarely glauconite. Quartz. polycrystalline quartz, siderite and chert are important accessories .

The ironstone ooids having the alternate coalS of berthierine/chamosite and ferric oxide were formed under changing physico-chemical conditions. Mineralized solutions containing iron and silicates replaced the carbonate ooids and other detritus during diagenesis. The ooids were fractured and distorted due to intergranular solution readjustment during compaction and later tectonics.