Kioto Limestone Fm
Type Locality and Naming
Many authors prefer to use "the long-established and widely known name Kioto Limestone (Hayden, 1908). … The platform limestones of the central Himalaya, including S. Tibet (Jadoul et al., 1998), are in fact undoubtedly part of the Kioto Group (Baud et al., 1982; Jadoul et al., 1990), which characterizes with similar facies all Tethys Himalayan regions."
Synonym: Jomoson Fm (Gradstein et al., 1991, after exposures at town of Jomoson, Thakkhola valley north of Anapurna, south of Tibet). "The term Jomosom Limestone has been introduced
by Bodenhausen et al. (1964) and subsequently adopted by several research teams in central Nepal (e.g. Bordet et al., 1967; Bassoullet and Mouterde, 1977; Gradstein et al., 1989)."
Lithology and Thickness
Platform limestone, up to 350 m thick. "In the basal 50 m of the Kioto Limestone Fm, metric intervals of up to upper medium-grained, cross-laminated hybrid quartzarenites are still
commonly interbedded with the mudstone/wackestone or bioclastic to oolitic packstone/grainstone.
Relationships and Distribution
Lower contact
Overlies Thini Fm (Zhamure Sandstone Fm of Garzanti, 1999)
Upper contact
Underlies Bagung Fm (Laptal Fm of Garzanti, 1999)
Regional extent
In many sections of the central Himalaya the base of the Kioto Limestone is markedly younger than in the N.W. Himalaya, and the unit here seemingly corresponds broadly only to the Lithiothis-bearing Tagling Limestone of the Spiti-Zanskar Synclinorium (Stoliczka, 1866; Jadoul et al., 1990), the underlying Megalodon-bearing Para Limestone Fm being locally replaced by the Zhamure Sandstone Fm.
GeoJSON
Fossils
In several central Himalaya localities, "the basal interval is reported to contain middle Liassic foraminifera (including Agerina martana and Haurania sp. or Orbitopsella praecursor ) from Thakkhola (Bordet et al., 1971, p. 143) to Manang (Fuchs et al., 1988, Figs. 8 and 9) and S. Tibet (Jadoul et al., 1998)." The formation "generally lacks the Megalodon-bearing intervals typical of the Para Limestone Fm of the Spiti-Zanskar Synclinorium. Triassic Megalodon beds have been reported only from Manang (Fuchs et al., 1988), while Liassic "Megalodon-Lithiotis shell beds'' were observed in Dolpo (Fuchs, 1977, Fig. 26). The top of the Kioto Limestone yielded benthic foraminifers of early Dogger age all along the Himalayas."
Age
Depositional setting
Additional Information
"Carbonate sedimentation thus did not become wide- spread until the middle Liassic, when the northern Indian margin straddled the Southern Tropic arid belt (Dercourt et al., 1993; Ogg and von Rad, 1994). Dark- grey marly intervals containing quartzose silt occur in the upper Liassic (Toarcian?) part of the unit from Zanskar (lithozone f of Jadoul et al., 1990) to S. Tibet (base of K2 member of Jadoul et al., 1998) but have not been reported from Nepal so far. All along the Tethys Himalaya, accumulation rates progressively decreased from over 50 m/Myr in the Late Triassic to less than 10 m/Myr in the earliest Dogger (Jadoul et al., 1990, 1998), reflecting reduced thermal subsidence and out-building of the Tethys Himalayan continental terrace during the mature passive margin stage."