Abstract Whole rock Sm–Nd isotope dating of the Garhwal and Bhowali mafic volcanics of the Kumaun Lesser Himalayan sector yield an age of 2.51±0.08 Ga and an initial ϵ Nd=5.1±0.5. This age and initial ϵ Nd are the same as that of the Rampur–Mandi volcanics, which occur to the west in the Lesser Himalayas. In addition to confirming the widespread presence of the Late Archaean crustal elements in the Himalayas, these data constrain the age of the oldest rifting event and deposition of supracrustal sediments in the Himalayas and set at rest the long standing controversy about the age and inter-relationship of these mafic volcanics. Despite their present-day disparate occurrence as a result of the post-eruption deformation, the area covered by these mafic volcanics is large enough to classify them as flood basalts, the Rampur flood basalt (RFB) province. Rift-related volcanism of the same age is known from the contiguous Aravalli region of the NW Indian Shield. The orientation of the rifts in the two regions suggests the possibility of a mantle plume setting for the RFB.