Kinematics of the Greater Himalayan sequence, Dhaulagiri Himal ...

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bounded by interpreted upper and lower limits (e.g., Arita 1983; Pêcher 1989; Grasemann et al.
1999; Bhattacharya & Weber 2004; Martin et al. 2005). The upper boundary of the shear zone is
commonly coincident with the Heim & Gansser (1939) defined MCT, while the lower boundary
is placed at the interpreted lower or southern limit of MCT-related strain (Arita 1983; Searle &
Godin 2003; Bhattacharya & Weber 2004).
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In a recent re-examination of the MCT fault conundrum, Searle et al. (2008) recognize a
thick zone of penetrative south-verging deformation extending below the migmatitic portion of
the high-grade slab, and map the MCT at the base of this shear zone. Rocks above their
interpreted MCT are defined as part of the Greater Himalayan sequence and are characterized by
an inverted Tertiary greenschist-to upper amphibolite-grade metamorphic field gradient and
pervasively developed, south-verging ductile deformation (Searle et al. 2008). This contrasts
with rocks below the MCT, which are by definition part of the Lesser Himalayan sequence, and
preserve sedimentary structures such as cross-bedding and ripples, contain abundant detrital
clasts, and are characterized by large-scale south-verging folding, brittle faulting, and multiple
cleavages. This interpretation of the MCT satisfies metamorphic temperature and pressure data
that show little-to-no break across the original Heim and Gansser (1939) discontinuity (e.g.,
Hubbard 1989; Macfarlane 1995; Vannay & Hodges 1996; Fraser et al. 2000; Kohn et al. 2001)
and agrees with studies that have interpreted the contact between the previously defined Greater
Himalayan sequence and Lesser Himalayan sequence as an unconformity (Goscombe et al.
2006; Searle et al. 2006) characterized by an isotopically-defined change in lithology (e.g.,
Martin et al. 2005).
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3. Geology of the Dhaulagiri Himalaya
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