D P Agrawal

Lake Sediments from the Kashmir Himalayas: Inverted 14C Chronology and Its Implications

We have measured 14C, 210Pb and 137Cs profiles in two representative cores from Manasbal Lake, Kashmir, India. The sedimentation rate derived from 210Pb and 137Cs in the upper part of the core is in the range of 3.4 to 5.5 mm yr-1. In contrast, 14C ages show an inversion at depths>20 cm. These results are attributed to the erosion of the ubiquitous 10-20-m-thick loess mantle, based on the similarity of 14C ages of the inversion layer in the sediments and the paleosols present in the catchment area. Frequency-dependent mineral magnetic susceptibility (Xfd), carbon to nitrogen ratios and pigment concentrations in the profile show a significant amount of allochthonous component in the lake deposits and support the conclusion that the 14C dates do not reflect the chronology of the in-situ lake sedimentation but episodic deposition of the surrounding loess. Thus, 14C serves as a useful tracer to understand source components of the sediments.

Sem and other studies on the Saurashtra miliolite rocks

Abstract The miliolite limestones of Saurashtra, western India have been variously ascribed to marine or aeolian agencies of deposition. Fresh results based on field work, microscopic and SEM data ascribe to the inland miliolites an aeolian origin.

Palaeosols within loess; dating palaeoclimatic events in Kashmir.

Loess deposits in India have so far been reported mainly from Kashmir and the Son Valley in Uttar Pradesh. In Pakistan, the Potwar Plateau also has significant thickness of loess deposits. In Kashmir loess forms the topmost mantle of the sedimentary profile which starts at ca 4.Om yr (Kusumgar,1980). The maximum thickness of loess in the Kashmir Valley is ca 25m in the Southwest diminishing to ca 1Om in the Northeast. As loess sits unconformably over the eroded surface of the Upper Karewas, the bottom of the loess profile follows an undulating topography. As none of the lake pollen profiles examined so far go beyond 20,000 BP, the loess profiles assume greater significance as a record of climatic events. Loess is predominantly a silt-sized (5 to 50μm) alkaline, amorphous sediment deposited through aeolian agencies in pen-glacial regions. In cold and arid climate, loess does not weather much. However, during milder climatic ameliorations (interstadials), some incipient pedogenesis does take place; full soil development is the result of generally warmer and humid conditions (interglacials). Due to the porosity and alkalinity of loess, pollen is generally not preserved, necessitating a search for other palaeoclimatic indicators. We have detected nine buried soils (palaeosols) in the Kashmir loess profile. The problem was to date the sequence of palaeosols to determine how many soils exist and how many represent major climatic oscillations. The 14C technique was used for dating and to distinguish soils representing significant climatic warming (interglacial type conditions). For milder climatic variations (interstadial type conditions), mineral magnetic, stable isotopic, and other parameters were used. Figure 1 shows the sites dated and Table 1 shows their 14C dates. Thirty I4C dates were obtained from ca 14 sites that fall into 5 clusters. Table 2 clearly shows that five soils formed during the period covered by the 14C dating range. We will first discuss the climatic sequence derived from the pollen profiles of the main bogs of Kashmir. At Butapathri I and II we observe a distinct climatic amelioration at 18,000 yr BP marked by the partial dominance of the broad-leaved groups such as Ulmus, Alnus, Juglans (Dodia, Agrawal & Vora,1985). A climatic amelioration occurs at Anchar at ca 5000 BP accompanied by an anthropogenic impact on the ecology in the form of Cerealia, Plantago pollen (Dodia, Agrawal & Vora, 1985). In the 14C dates cluster of palaeosols we do get well-developed soils at ca 5000 ± 1000 BP and ca 18,000 ± 1500 BP.

Palaeoclimate, stratigraphy and prehistory in north and west Rajasthan

Quaternary formations in western Rajasthan are of fluvial, locustrinal and aeolian origins. Fossil gravel ridge of Jayal in Nagaur District is one of the earliest quaternary formations so far recorded in the region. A rich lower palaeolithic habitation-cum-workshop site has been discovered in association with the gravel ridge. Multiple evidence for climatic change in the area during the quaternary period is discussed.

Cist burials of the Kumaun Himalayas

In the Kumaun region of Uttar Pradesh, India, on the southern slopes of the Himalaya are cist burials, as well as megalithic monuments. Radiocarbon dates from the cists now hint at their going back to the 3rd millennium BC, and linguistic affinities would associate them with early Indo-European migrations into the western and central Himalaya regions.

The Neogene/Quaternary boundary in India: A review

The Neogene/Quaternary boundary has been variously defined in different continents. A global review of the problem shows that only the Olduvai event on the palaeomagnetic timescale may provide an universally acceptable isochronous datum for delineating this boundary. The N/Q boundary in the Siwaliks, Kashmir and the Andamans in India is defined in the light of recent research.

Thermoluminescence dating of pottery from Sringaverapura—A Ramayana site

The first thermoluminescence (TL) dates of pottery from aRamayana associated site are reported. The TL dates for pre-NBPW Black-Slipped Ware levels are 730 and 765 B.C., while radiocarbon date takes the earliest Black Slipped Ware level (for which no TL dates are available) to 905 B.C. (uncorrected). For the OCW level, three TL dates are available which range from 1035 B.C. to 875 B.C. The early NBPW period believed to be associated with theRamayana episode will thus be post-750 B.C.

Palaeoclimatic inferences from the behaviour of radiocarbon dates of carbonates from Sand Dunes of Rajasthan

Radiocarbon dates on pedogenic CaCO3, accumulated at various depths in a stabilised dune at Budha Pushkar, Rajasthan, show inversion with respect to ‘stratigraphy’. Occurrence of younger carbonates overlain by older ones at various levels, is interpreted in terms of a shift in climatic conditions causing pedogenic carbonates to be leached to greater depths. Based on this model, several wetter regions during the last 6000 years have been identified. The most significant shift from a dry to a wet phase seems to have taken place between 5000 and 4500 years ago. Conclusions drawn from this study is in agreement with that based on pollen data and extends this method as a potential palaeoclimatic indicator.

The ambient environment of the Gangetic sediments of chalcolithic period

There is considerable controversy regarding the mode of deposition of the OCP culture-associated sediments in the Gangetic valley and their ecological implications. SEM and sedimentologic studies show a fluvial mode of deposition of sediments originally derived from a glacial environment.