The Sivalik Hills are a mountain range of the outer Himalayas that stretches over about 2,400 km (1,500 mi) from the Indus River eastwards close to the Brahmaputra River, spanning the northern parts of the Indian subcontinent. It is 10–50 km (6.2–31.1 mi) wide with an average elevation of 1,500–2,000 m (4,900–6,600 ft). Between the Teesta and Raidāk Rivers in Assam is a gap of about 90 km (56 mi).[3]
They are well known for their Neogene and Pleistocene aged vertebrate fossils.[4]
View of the Sivalik hills from Sukhna lake at dawn
Geologically, the Sivalik Hills belong to the Tertiarydeposits of the outer Himalayas.[5] They are chiefly composed of sandstone and conglomerate rock formations, which are the solidified detritus of the Himalayas[5] to their north; they are poorly consolidated. The sedimentary rocks comprising the hills are believed to be 16–5.2 million years old.[6]
They are bounded on the south by a fault system called the Main Frontal Thrust, with steeper slopes on that side. Below this, the coarse alluvial Bhabar zone makes the transition to the nearly level plains. Rainfall, especially during the summer monsoon, percolates into the Bhabar, then is forced to the surface by finer alluvial layers below it in a zone of springs and marshes along the northern edge of the Terai or plains.[7]
The Sivalik Hills are well known for fossils of vertebrates, spanning from the Early Miocene, until the Middle Pleistocene, around 18 million to 600,000 years ago.[8][9]
Remains of the Lower-Middle PaleolithicSoanian culture dating to around 500,000 to 125,000 years Before Present were found in the Sivalik region.[13] Contemporary to the Acheulean, the Soanian culture is named after the Soan Valley in the Sivalik Hills of Pakistan. The Soanian archaeological culture is found across Sivalik region in present-day India, Nepal and Pakistan.[2]
^Kaur, A. P. (2022). "New fossil mammalian assemblages and first record of ostrich from the Pinjore (Pinjor) formation (2.58–0.63 Ma) of Siwalik Hills near Chandigarh, northern India". Quaternary Science Reviews. 293: 107694. doi:10.1016/j.quascirev.2022.107694.
^Mani, M.S. (2012). Ecology and Biogeography in India. Springer Science & Business Media. p. 690.
^Nanda, A.C. (2002). "Upper Siwalik mammalian faunas of India and associated events". Journal of Asian Earth Sciences. 21 (1): 47–58. doi:10.1016/S1367-9120(02)00013-5.
^Patnaik, R. (2013). "Indian Neogene Siwalik Mammalian Biostratigraphy. An Overview". Fossil Mammals of Asia. New York Chichester, West Sussex: Columbia University Press. doi:10.7312/wang15012-017.
^Kelley, J. (1988). "A new large species of Sivapithecus from the Siwaliks of Pakistan". Journal of Human Evolution. 17 (3): 305–324. doi:10.1016/0047-2484(88)90073-5.
^Lycett, S. J. (2007). "Is the Soanian techno-complex a Mode 1 or Mode 3 phenomenon? A morphometric assessment". Journal of Archaeological Science. 34 (9): 1434–1440. doi:10.1016/j.jas.2006.11.001.