Geoscience Reference
In-Depth Information
Figure 19.5. Cross-bedded late Pleistocene alluvial sands, middle Son Valley, north-
central India.
Middle Palaeolithic stone tool assemblage. The age of this formation is early in the
Upper Pleistocene, when the climate was far wetter than it is today, most likely during
the last interglacial, when regional evidence points to a much stronger monsoon (Juyal
et al.,
2006
; Gibling et al.,
2008
).
A pronounced erosional unconformity separates the Patpara formation from the
overlying Baghor formation, which consists of a lower coarse member about 10 m
thick and an upper fine member also about 10 m thick. The coarse member consists of
cross-bedded medium to coarse sands (
Figure 19.5
) with lenses of sandstone, agate,
chert and chalcedony ranging in size from granules to pebbles and discontinuous
sheets of massive carbonate cemented sands. These latter beds contain well-preserved
fossils of buffalo, hippo, antelope, elephant and tortoise, as well as rolled and abraded
Middle Palaeolithic artefacts. The fine member rests conformably on the lower coarse
member and consists of interbedded clays, silts and fine sands. It attains an elevation
of at least 30 m above low water level and contains fresh Upper Palaeolithic artefacts
in the upper few metres, as well as on the surface. This Upper Pleistocene formation
is now reasonably well-dated using both
14
C and IRSL dating methods (Pal et al.,
2004
; Williams et al.,
2006b
). Deposition of the coarse member began at around
39
3 ka. This interval encompasses the cold, dry
LGM, which was followed by a warmer, wetter climate after about 17-16 ka. The fine
±
9 ka and ended at around 16
±
