Major unconformity between two juxtaposed sedimentary belts of the Lesser Himalaya, as revealed from the U–Pb zircon geochronology

Available U–Pb zircon detrital geochronology (DZ) data from the Lesser Himalaya reveals that the sediments within the Inner Lesser Himalaya (iLH) were deposited ~1850 Ma. The Outer Lesser Himalaya (oLH) sedimentary succession was much younger between 950 and 525 Ma; this belt also witnessed younger marine transgressions during the Permian, Jurassic–Cretaceous and Eocene. Thus, the Lesser Himalaya is characterized by two distinct sedimentary belts, which are juxtaposed against each other along the Tons–Daling–Shumar Thrust (TDST), at present. Further, these belts also represent two distinct terranes, delimited by major tectonic boundaries: (i) the Late Paleoproterozoic iLH Terrane bounded by the Vaikrita Thrust (VT)/Main Central Thrust (MCT) in the north and TDST in the south, and (ii) the Neoproterozoic oLH Terrane delimited by the TDST and the Main Boundary Thrust (MBT). The iLH Terrane represents the main magmatic arc and back-arc basin of the Columbia Supercontinental Assembly. The oLH Terrane also indicates the back-arc basin of the Rodinia Supercontinental Assembly during the Neoproterozoic. These terranes record a major stratigraphic break around 1000–800 myr, when the depocenter for sedimentation shifted southwards during the Tonian to the outer parts of the Lesser Himalaya (oLH). Research Highlights Lesser Himalayan U-Pb DZ ages compiled from the NW, Nepal and Eastern Himalaya. Maximum depositional age of the Inner Lesser Himalayan (iLH) belt is around 1850 Ma. Sediments of the oLH belt are much younger between 950 and 525 Ma, and still younger in east. Two LH sedimentary belts are juxtaposed along the Tons–Daling–Shumar Thrust (TDST). Major stratigraphic break between these basins spans around 1000 to 800 myr. Depocenter for sedimentation shifted southwards in outer parts of the Lesser Himalaya.