Kagbeni Fm

Overlies Dangardzong Fm. "The base of the unit is a sharp unconformity corresponding to a drastic petrographic change from nearly pure quartzose to dominantly basaltic detritus."

Underlies the Muding Fm.

"In the more distal Tangbe area, these coarse-grained continental volcaniclastics seemingly wedge out and are replaced by interbedded sandstones and shelf mudrocks containing benthic foraminifera of Valanginian to Hauterivian age in the lower 170 m."

"Mixing of volcanic and partly recycled quartzose to quartzo-feldspathic continental block detritus characterizes the whole of the Tethys Himalayan succession from S. Tibet, where intraplate volcanism started possibly even earlier than the Jurassic/ Cretaceous boundary (Jadoul et al., 1998), to the Spiti- Zanskar Synclinorium, where it was recorded only at Albian times (Garzanti, 1993a,b). Diachronous effusion of intraplate alkali basalts and more felsic differentiates on the southern margin of Neotethys, in a vast area from offshore S.E. Africa to N.E. India and offshore N.W. Australia (e.g. Vallier, 1974; Baksi et al., 1987; von Rad et al., 1992), is related to a period of extensional tectonism, when deep-seated faults propagated through the continental crust and tapped magma sources in the upper mantle. These tectonic and magmatic events accompanied the successive detachment of India from Africa, Australia and Madagascar, and marked the initial opening of the Indian Ocean and the final disintegration of the Gondwana superplate. Volcaniclastic sedimentation ended synchronously in the late Albian all along the southern margin of Neotethys from Zanskar to Nepal, where the terrigenous Chukh Group was mantled by condensed glauconitic arenites and mudstones yielding planktonic foraminifers of the R. subticinensis Subzone; ``Glauconitic Horizon'' of Premoli Silva et al., 1991)."