Ferruginous Oolite Fm
Type Locality and Naming
Widespread marker throughout Tethyan Himalaya (Heim and Gansser, 1939; Bassoullet et al., 1986), named for its distinctive lithology.
Synonym: maybe the uppermost part of Tagling Fm (used in Zanskar-Spiti)
Lithology and Thickness
Condensed deposit (5 to 7 m maximum) of dark-red clayey limestone, rich is hematite-oolites (not to be confused with typical calcareous oolites) and phosphate.
Relationships and Distribution
Lower contact
Overlies Bagung Fm. "Base is a major regional unconformity marking a distinct sedimentary change"
Upper contact
Overlain by Danger Fm
Regional extent
"A widespread condensed oolitic ironstone horizon with brachiopod and ammonoid faunas of late Bathonian/early Callovian to middle Callovian age (Jadoul et al., 1985; AlmeÂras et al., 1991, 1996; Cariou et al., 1994, 1996) documents drowning of the Indian margin during a major eustatic rise." It is "only 3 to 10 m thick in Kumaon (Heim and Gansser, 1939) to central Nepal and S. Tibet (Jadoul et al., 1998), [but] the unit is 18 to 33 m thick in the Spiti-Zanskar Synclinorium, where it shows considerable lateral variation but generally consists of two distinct oolitic ironstone layers separated by a shaly to sandy section (Jadoul et al., 1985; Garzanti et al., 1993)." [Note: A condensed iron-oolite clayey limestone also marks the Bathonian-Callovian boundary interval at the proposed Callovian GSSP in Swabia, Germany.]
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Fossils
Age
Depositional setting
Additional Information