The general notion is that the Lesser Himalayan Sequence (LHS) rocks are in the footwall of the Main Central Thrust (MCT), and the Greater Himalayan Sequence (GHS) thrusted over LHS along the MCT. So the key is to find the MCT that separates the LHS from the GHS. In general, the GHS rocks are structurally at a higher position. However, as the Himalaya is the fold-thrust mountain belt, folding and rotation of thrust are not unique. So this further complicated the identification of GHS and LHS rocks.

LHS is mainly composed of greenschist grade metamorphic rocks, whereas high-grade rocks are found in GHS. So we can consider both the structural position and the grade of metamorphism to distinguish the GHS and LHS. This is well established in different sectors of the Himalaya where the major thrust zones are well demarcated. However, In the NW Himalaya, the conflict persists on whether to put the Jutogh formation (Metasediments with high-grade intrusive rocks) in LHS or GHS or the Tethyan Himalayan Sequence (THS). I think this conflict is because of the lack of geochronological evidence for MCT and STD. I am also aware of the isotopic markers that differentiate these three litho-units. However, I am not confident due to my lack of knowledge in geochemistry. Please educate me!

Age data of the rocks are also used to distinguish the litho-units. However, selective dating of rocks might give an erroneous interpretation.

Are there any other criteria that help to distinguish the different litho-tectonic units, LHS, GHC, and THS? Suggestion of published work will be greatly appreciated!