The first chopper in Asian late Pliocene silts, Masol, Northwestern India : bio-lithostratigraphy, magnetostratigraphy and dating evidences. I
Abstract
The field works conducted since 2009 in the sub-Himalayan palaeontological Quranwala zone at Masol, Siwaliks, Northwestern India, has enabled us to collect fossil bones with cut marks and stone tools in quartzite (Human origins in the Indian sub-continent, dir. A. Dambricourt Malassé, Palevol, 2016, 15, 3-4: 279-452). The layers composed of sands and silts are visible on and around the dome of an anticline tilted by the tectonics and gullied by the monsoon rainfall. The fossil assemblage known since the 1960s is characteristic of the late Upper Pliocene in Northwestern India (e.g. Hipparion-Equus, Stegodon-Elephas, Merycopotamus) and the paleontological deposits are clearly below the Gauss-Matuyama Reversal (> 2.588 Ma, in Ranga Rao 1993). Our field works have recorded 12 localities in the deepest fossiliferous layers where cut marks are in association with other bones and artifacts: choppers, flakes, anvils, hammerstones and rare cores. These artifacts have been collected only on the fossiliferous layers (40 meters thick), while erosion affects all the cliffs (170 meters thick). We have checked the normal polarity. The first tool in situ has been excavated in 2017 at Masol 1 on the summit of the anticline, this locality, 450 m long x 50 m width, had provided 387 fossils and 23 artifacts. The new artifact was 50 meters far from cut-marks and in the same silty horizon. These silts referenced c3 in our lithostratigraphic log are 3 meters thick. An excavation was carried out mainly to study the mineralogy and verify the homogeneity of the silts. The mineralogical analyses confirm the lack of disturbance or secondary deposits while the paleomagnetism of the silts c3 measured in the vicinity of the excavation, put in light an excursion dated between 2.62 Ma and 2.95 Ma (Chapon Sao et al. submitted). The dating of Masol 1 is in progress by Electron Spin Resonance. The tool is a split quartzite pebble, obtained by the bipolar-on-anvil technique, then shaped by removals from its edge. The result is a unifacial chopper (91 x 75 x 30 mm). The industry of the fossiliferous localities is very homogeneous and does not match neither with the Middle Pleistocene Soanian known in the Siwaliks nor with the Oldowan known in Africa at the very beginning of the Pleistocene. On the other hand, a comparison with the lithic assemblages described at this same period in China, allows us to conclude to a great similarity between the Masol and the Longgupo industries.