INTRODUCTION
The River Manjra, the major southerly tributary of the Godavari, is known for the occurrence of fossilized skeletal remains of large and small vertebrates, whose taxonomic diversity is only next to the Narmada valley in central India. It originates in the Ahmednagar District of Maharashtra and after flowing for a distance of about 724 km through the states of Karnataka and Telangana, meets the River Godavari near the village Kandhakurthi in Nizamabad District of state of Telangana, India (Figure 1). In the upper reaches, especially within the vicinity of districts of Beed and Latur, a fossil trove was unearthed some 45 years ago, which emerged as a landmark discovery in revealing the evidence of a rich prehistoric wildlife during the Late Pleistocene period in southeastern Maharashtra (Joshi et al. Reference Joshi, Chitale, Rajaguru, Papu and Badam1981; Sathe Reference Sathe1989). The taphonomic history of the fossil record shows the evidence of various events of accumulation and deposition that range from the drought(s) to fluvial contexts (Sathe Reference Sathe1989, Reference Sathe, Yasuda and Shinde2004). Litho-stratigraphy of the fossil yielding horizons led to the assignment to the Late Pleistocene period (Joshi et al. Reference Joshi, Chitale, Rajaguru, Papu and Badam1981; Sathe Reference Sathe1989). Two of the rich fossil localities viz. Tadula (18º32′50″N, 76º23′E), and Wangdari (18º33′N, 76º24′25″E), located in Beed District of Maharashtra have reported abundant fossilized mollusks in association with vertebrate fossils which based on the lithostratigraphic association with bones and embedded matrix of shells indicated that temporally they shared the same horizon. These shells especially from Tadula and Wangdari were subjected to radiocarbon (14C) dating at the Birbal Sahni Institute of Palaeosciences (formerly Birbal Sahni Institute of Palaeobotany), Lucknow and were dated to 26,820 ± 750 BP and 34,470 ± 2070 BP, respectively, which assign late Pleistocene age to the faunal assemblage in Manjra valley (Sathe Reference Sathe1989).
The recent discovery of a fossil bone bed at Harwadi (18º27′40″N, 76º35′38″E), about 45 km farther downstream of the aforesaid known fossil localities further added new fossil discoveries to that made the detailed examination of the fauna imperative. The undisturbed fossil assemblage with a minimal taphonomic modifications has been very helpful in explaining the environmental setting during the Late Pleistocene period in this region (Sathe Reference Sathe2005, Reference Sathe2015). The homogeneity in the degree of fossilisation, taxonomic diversity and lithostratigraphic contexts has helped in assigning the events of death and burial within the close proximity of Harwadi. This phenomenon is contemporary to the earlier known fossil bearing sites like Dhanegaon, Wangdari, Ganjur, and Tadula. There have been no further dates available and therefore, the earlier dates have remained the point of reference for chronology of this newly discovered fossiliferous horizon in the Manjra valley.
The age of large mammalian fossil yielding deposits in the Upper Manjra valley (Beed and Latur districts), has been dated to the time range between 22,000 to 34,000 years on the basis of conventional 14C dating of molluscan shells. This is the first occasion to have bones directly dated using accelerator mass spectrometry (AMS) dating, which reflects precise chronology of megaherbivores that lived in the valley during the later part of the Pleistocene period in the Manjra valley. The present work has yielded new dates that can contribute to our understanding of the paleoenvironmental conditions, especially when the Terminal Pleistocene landscape was experiencing major climatic shifts prior to the LGM.
Faunal History of the Region
As with most of the fossil discoveries, the prehistoric faunal wealth of the region came to light when the alluvial cliffs were being dug on the banks of river Manjra in District of Beed in Maharashtra by the Irrigation Department of state of Maharashtra in early seventies of the last century. The discovery of the fossil potential prompted a three-year project undertaken by the geologists, prehistorians and a palaeontologist of Deccan College, Pune, who explored the entire Manjra valley from origin to its confluence with Godavari and brought to light in the context of alluvial flood plains several prehistoric sites with late Acheulian, Middle Palaeolithic, and Mesolithic tools but the fossil sites were found to be limited to the District of Beed in Maharashtra state (Joshi et al. Reference Joshi, Chitale, Rajaguru, Papu and Badam1981). Faunally and litho-stratigraphically, there appears a general uniformity in the faunal wealth of Manjra, Godavari and other river valleys of Western India which chronologically fall between 25,000 to about 40,000 years of history of their survival. The fossil record includes about 20 genera and 25 species of large to medium-sized mammals, reptiles, microvertebrates, and mollusks which along with the Early, Middle, and Upper Palaeolithic tools mark the region a conducive landscape for survival of prehistoric man for a continuous occupation from Late Acheulian to the Mesolithic (Tables 1–3).
The multispecies mammalian fauna in the Manjra valley is an admixture of megafauna that had either Ethiopian or Palaearctic origins as being the descendants of the Siwalik holdovers in the later part of the Pleistocene. However, of all the reported, there are eight genera (mostly artiodactyls) which are endemic to Indian subcontinent and appear to represent their wide home range throughout the Pleistocene (Turvey et al. Reference Turvey, Sathe, Crees, Jukar, Chakraborty and Lister2021). It has been argued that the southward migration of post-Siwalik fauna led to a mosaic of palaeo-communities that thrived throughout Peninsular India until the known episodes of dry and arid phase triggered by the LGM.
Importance of the Site and its Faunal Diversity
Even if the Pleistocene faunal wealth of Peninsular India brings about a tapestry of diverse vertebrate fauna, its distribution and occurrence has been defined by fluvial behaviour and hydrodynamic sorting (Badam et al. Reference Badam, Ganjoo and Salahuddin1986; Badam and Jain Reference Badam and Jain1988; Sathe Reference Sathe1989; Patnaik et al. Reference Patnaik, Chauhan, Rao, Blackwell, Skinner, Sahni, Chauhan and Khan2009). However, the fossil discoveries in the alluvial deposits of the River Manjra at the site of Harwadi provided minimal taphonomic modifications despite fluvial dispersal of the fossil assemblage. The faunal diversity supplying a rich data of palaeo-community is further authenticated by a vast body of evidence related to vegetation, palaeodiet and environment (Sathe Reference Sathe2015; Sathe et al. Reference Sathe, Rai and Agnihotri2018) which has amply shown their role in maintaining the large mammalian population in the vicinity.
The wet land conditions enabled perennial grass cover and galleria forests along the river banks, which is also supported by predominant grazers preferring C4 diet along the forests, interspersed with open grasslands in the region. The presence of an immigrant carnivore (tiger) at Harwadi is a major landmark taxon (Sathe and Chakraborty Reference Sathe and Chakraborty2016), especially given that its arrival in India has been considered to be not older than 12 kyr BP (Mondol 2011). Even if this is accepted, the tiger arriving in Indian Peninsula during the end phase of LGM shows the presence of ecologically supportive corridors in the southeast China, which enabled the movement of large felids into India.
The Indian Peninsula has lost only 9 from a total of 114 modern taxa, namely hippopotamus, two species of elephants, and horse, to environmental change and alleged anthropogenic intervention at the end of the Pleistocene (Jukar et al. Reference Jukar, Lyons, Wagner and Uhen2021; Turvey et al. Reference Turvey, Sathe, Crees, Jukar, Chakraborty and Lister2021; Sathe Reference Sathe and Kamti2022). The African continent, in comparison, showed 24 species and 3 genera disappearing as part of the Late Quaternary extinction window (Faith Reference Faith2014). Southeast Asia lost 2 elephant genera, the orangutan, hyenas, the giant panda, tapirs, rhinoceroses, and the giant Asian ape, due to climatic and the sea level changes (Louys Reference Louys2007). Among all the megaherbivores, hippopotamus disappears practically from all places that shows significant climate change resulting in considerable loss of their habitat and access to perpetual water bodies. This ecological perspective needs to be understood in a chronological frame, especially in context of the rest of the world experiencing major climatic upheaval owing to the onset of aridity and glacial episodes.
There is an important need to focus on obtaining a large body of reliable 14C dates obtained directly on securely identified megafaunal remains in this region of Peninsular India. So far there are majority of 14C dates available on mollusks that are reportedly found in association of fossils or representing the same fossil bed. Relying on these dates requires the assumption that the shells and the megafaunal fossils are contemporary—which may not be the case depending on the taphonomic environment. In addition, studies have shown that the “hardwater” reservoir effect, and diagenesis of the outer layers of the shell can affect the age produced from these samples, rendering them less reliable (Preece et al. Reference Preece, Burleigh, Kerney and Jarzembowski1983; Yates Reference Yates2016; Wright Reference Wright2017).
Methods like fluorine dating are not entirely reliable except that they allow a concept of Late Pleistocene chronology to the fossiliferous beds but not the fauna that lived along the river valleys and its galleria forests. The strength of a chronology heavily depends upon the quality of dates. Therefore, the calibrated AMS dates freshly obtained on the megafauna from the site of Harwadi, using the methods described in the following sections, represent a beginning for the obtainment of direct AMS dates on fossil material—which can help in understanding the ecological proxies for the Terminal Pleistocene palaeoenvironment of the Manjra valley and Peninsular India.
Lithostratigraphy and Depositional Environment
The Quaternary formations in the area have a lateral extension of about 2 km and are confined to broad and shallow valleys cut into lower surfaces. Alluvial deposits are characterized by cut and fill types with thickness ranging from nearly 10 to 12 m. The Older Alluvium is represented by well cemented cross-bedded, poorly sorted, coarse-grained sandstone, and calcareous yellowish brown sandy siltstone, being the representative litho units in the region (Figure 2) The cemented sandy pebbly, poorly sorted, and coarse-grained sandstone has yielded all the fossils and the pattern of fossil scatter and mode of preservation and presentation renders it into the category of a bone bed.
The river Manjra originates in semi-arid plateau landscape at an elevation of 824 masl and flows throughout a similar landscape until its confluence with Godavari after completing a course of 724 km. The total area covered by the course of river Manjra within the district of Latur totals 126 km and the average rainfall is 800 mm, making it a wet land within the semiarid region of its course. Sedimentologically, the clay bands within the bone bed and lenticular patches of fissured clay represent pool phenomena that had adequate surface (channel pools, near channel, and wetlands) as well as groundwater recharging sand beds even in dry hot summers immediately before the LGM. This period also coincides with aggradational phase of river Manjra. Moderate slope of the valley, coupled with weaker currents eventually failed to transport the death assemblage and subsequent burial may have been possible only during the strong monsoonal floods.
The megavertebrate fossils are surface collected as well as excavated from the lithified sandy pebbly gravel or pebbly sandstone overlying cobbly, pebbly conglomerate and were subjected to detailed taphonomic analysis (Sathe Reference Sathe2005, Reference Sathe2015).
Sedimentology of the bone-bearing sandy beds reveals a 9–10 m of vertical section exposed along the left bank of Manjra. The bone-bearing deposit is a pebbly sandstone with reposited pebbles, silt and sand, with clayey bands, overlying well cemented calcareous sandy pebbly cross bedded gravel or pebbly orthoconglomerate above the Deccan Trap basalt. The fossils are found resting at an average dip of 20 degrees with a limited dispersal of the skeletal material, suggesting the moderate channel slope of the river. As the river was in aggradational mode, stream currents were too weak to transport the megavertebrates further downstream. As a result, some of the skeletal elements of hippos, elephants and bovids show a differential subaerial weathering indicating prolonged exposures prior to burial.
Chronological Frame of Fossil Sites in Western Maharashtra with Special Reference to Manjra Valley
One of the first-ever chronological assessments of fossiliferous horizons in Peninsular India dates back to the beginning of the 20th century when Pilgrim (Reference Pilgrim1905) compared the ossiferous gravels and fossils discovered by him at the banks of River Godavari in Nasik District of Maharashtra with that of Narmada valley. Based on litho-stratigraphical and fossil correlations he assigned them to the late Pleistocene period.
Chronology of the Pleistocene fossiliferous horizons in Peninsular India traditionally finds litho-stratigraphical correlations of fossil occurrences, through osteological and morphometric approaches in assigning chronological horizons to type species and methods of absolute and relative dating, which collectively have been helpful in providing a time frame to the fossil record. In many cases, palaeolithic stone artifacts have been reported in association with vertebrate and molluscan fossils which also helps in providing a broad time frame that the typology provides to the lithic assemblage, besides throwing light on the prehistoric man-animal relationships.
Climatologically, the deposition of these fossil and implementiferous gravels correlate with phases of global aridity (Sadakata et al. Reference Sadakata, Maemoku, Rajaguru, Mishra and Fujiwara1995) but episodic aggradational events were favourable for the preservation of lithic and fossil evidence (Rajaguru and Mishra Reference Rajaguru and Mishra1997). The sedimentary constituents of the Late Pleistocene sediments exhibit the high proportions of calcrete within the fine predominantly silt deposits, indicating distinctly arid climate with short spells of semi-arid climate (Deo and Rajaguru Reference Deo, Rajaguru, Paddayya and Sushama2014). However, the occurrence of rich large mammalian fossil yielding localities in the Manjra valley strongly suggest a wet semi-arid phase chronologically falling into the MIS 3 phase. In other words, it is characterized by a wet phase within a prolonged period of aridity. This is sedimentologically indicated by the combination of fine and coarse sediments, sandy pebbly gravels with lenses of silt, seen in association with channel and near channel flood plain deposits.
A number of 14C dates for the Late Pleistocene are available which cluster around 25 ka, 20–18 ka, and even stretch to the threshold of the Holocene to 12–10 ka, as shown in Table 1. However, most of these are on molluscan shells, Ostrich eggshells, volcanic ash, and calcrete. In contrast, very few dates are obtained directly on megafaunal fossil material and are obtained through U-Th series rather than 14C. On the other hand, chemical methods of dating such as Fluorine dating have been used with considerable success in assigning a rough time frame to the events of burial and fossilization.
A vast body of samples of bones from Early Pleistocene (Upper Siwalik fossil from NW India) to the bones of modern mammals (early Holocene) have been evaluated for the presence of fluorine. The value of fluorine has shown a visible correlation with the dates that have been derived on radiocarbon dating. (Kshirsagar Reference Kshirsagar1993; Sathe Reference Sathe2017)
AMS-14C dating of Manjra Valley Samples and its Bearing on the Chronology of Fossil Sites in Peninsular India
The absence of direct dates on megafaunal fossil material also makes it difficult to assign precise dates for disappearance or extinction of many species especially in the context of Late Quaternary extinction in India (Turvey et al. Reference Turvey, Sathe, Crees, Jukar, Chakraborty and Lister2021).
In addition to the “hard water” reservoir effect mentioned above, there is also taphonomic bias in the depositional history of vertebrates, making the mollusks’ precise association with fossils difficult and contested. The present work marks the first time that fossilized bones have been dated directly through AMS, and the values are in close congruity with biostratigraphical, skeletal, and morphological parameters. The dates are a definite indication that the period to which the fauna belonged to was closely approaching the Last Glacial Maximum (LGM). Hence, the palaeoecological inferences drawn using isotope chemistry and histology of calcified tissues provide crucial link to the palaeoenvironmental conditions that prevailed in the Manjra valley in the terminal phase of the late Pleistocene (Sathe Reference Sathe, Pellegrini and Parris2018; Sathe et al. Reference Sathe, Rai and Agnihotri2018). The presence of clay bands within the bone bed and lenticular patches of fissured clay (representing pool phenomena) indicates that climatic conditions in the Upper Pleistocene were also approximately the same, with adequate water to recharge both surface and groundwater features (Kulkarni, pers. comm.).
The occurrence of fossilized partial skeletons and isolated bones and teeth of six incisored hippopotami from the multi-species fossil scatter at Harwadi have provided vital information about the vegetational diversity, further attested by the palynomorphs of diverse plant species (Sathe Reference Sathe2015). The date of disappearance for hippopotami in India is known to coincide with the end of the Pleistocene, due to the extended periods of dry and arid conditions resulting in depletion of permanent water bodies during the LGM. This time period also witnessed the extinction of other large mammalian taxa like Equus namadicus, Stegodon insignis ganesa, Elephas hysudricus, and Palaeoloxodon namadicus from India.
However, it has also been postulated by Jukar et al. (Reference Jukar, Patnaik, Chauhan, Li and Lin2019) that the extinction of large megafauna at the end of the Pleistocene was due to anthropogenic factors rather than purely climatic or environmental, based on the dating of a single Hippotamus canine that yielded a date of 16,000–15,000 BP (Jukar et al. Reference Jukar, Patnaik, Chauhan, Li and Lin2019).
Except a few examples from the Hunsgi-Baichbal valleys (Sathe and Paddayya Reference Sathe and Paddayya2013), the near total absence of human signatures in terms of cut and chopping marks on the fossilized bones from the Pleistocene fossil assemblages in India questions the role of humans as major factor of extinction of Pleistocene mammals in India.
Given that the date in Jukar et. al. (Reference Jukar, Patnaik, Chauhan, Li and Lin2019) was obtained on a single specimen and not directly on bone collagen, more dating of Hexaprotodon fossils must be carried out from the Indian Subcontinent in order to arrive at a clearer picture of their chronological position, especially with regard to their disappearance or Last Appearance Datum (LAD).
Sample Preparation and Analysis
Bone alteration during burial is the most significant diagenetic process which defines the future survival of the bone in the sedimentary environment. The diagenetic parameters include collagen content, histological integrity, porosity and crystallinity (Hedges Reference Hedges2002). Much collagen loss is correlated with microbial attack in the early stage of diagenesis, which is clearly defined by histological alteration of the fossilized tissue structures (Nielsen-March and Hedges Reference Nielsen-March and Hedges2000).
Besides the bacterial and fungal modes of attack (where the bone may lose even up to 80% of collagen), in warm climates, temperature sensitive collagen loss is inescapable, where hydrolytic mechanisms have an important bearing upon the loss of collagen. Therefore, it has to be borne in mind that the accuracy of a derived date is controlled by the chemical purification, geological provenance and taxonomic identification of the sample. This is evident in the attempt by Jukar et al. (Reference Jukar, Patnaik, Chauhan, Li and Lin2019), where the lack of visible collagen forced the authors to date the organic materials potentially found in the phosphates leached from the sample through HCl treatment as directly dating the collagen was not possible. It is due to the inevitable aspects like contamination, degradation and carbon-exchange issues, that fossil bone is invariably considered as one of the most unreliable materials for 14C dating (Hedges and Klinken Reference Hedges and Van Klinken1992).
In this context, we employed the treatment methods recommended in Cherkinsky (Reference Cherkinsky2009) for dating the bioapatite fraction. A batch of samples was taken from the samples collected from the site of Harwadi, Latur District, Maharashtra, comprising a section of elephant (Elephas sp.) ivory, a hippopotamus (Hexaprotodon palaeindicus) molar, and a section of ischium (pelvic) bone from a large bovine (Table 4).
As per the method described in Cherkinsky (Reference Cherkinsky2009), as a first step, each sample was physically or mechanically cleaned as far as possible, removing all of the surrounding matrix and any visible foreign matter. Following this, the samples were soaked in 1N acetic acid overnight and then cleaned by decantation, discarding all the material that was loosened from the fossil samples. The remaining material was then dried for a similar amount of time and again cleaned manually. The sample was then crushed to coarse fragments approximately <1 mm in size. Crushing to a fine powder was avoided to preserve bioapatite structure as stated above. These crushed samples were sent to Inter University Accelerator Centre (IUAC), New Delhi, and further sample processing was done in their graphitization laboratory of AMS facility. 2 g of sample was taken from each fossil specimen and treated with 1 N acetic acid in a 50 mL centrifuge tube. These centrifuge tubes were kept in a vacuum desiccator and samples were evacuated 10 times in 48 hr up to the point when no effervescence was observed. No effervescence was an indication of complete removal of secondary carbonates. Acetic acid was removed from the samples by cleaning with type 1 water (resistivity 18.2 MΩ-cm) and samples were dried in vacuum using a freeze dryer. 300–400 mg of such cleaned samples was taken in a 12 mL vial, flushed with helium gas for 10 min and then acid hydrolyzed using 1N HCl acid in the carbonate handling system (CHS) that is coupled with automated graphitization equipment (AGE). Samples were completely dissolved in 1N HCl acid at room temperature and no collagen chunk was observed in all these three samples. In the hydrolysis, produced CO2 was trapped in the zeolite trap and graphitized using AGE (Sharma et al. Reference Sharma, Umapathy, Kumar, Ojha, Gargari, Joshi, Chopra and Kanjilal2019). Bioapatite content (carbon percentage) in these samples were varying from 0.17% to 0.24% as shown in Table 4. This content is less than the range (0.4–0.7%) described by Cherkinsky (Reference Cherkinsky2009). According to Cherkinsky (Reference Cherkinsky2009), if bioapatite content is more than (0.4–0.7%) indicates that diagenetic carbonates are not removed completely. In our case bioapatite content was less than the above range, implying that samples were cleaned with acetic acid for longer duration and some of the bioapatite fraction may have also reacted with acetic acid during the cleaning. Produced CO2 in all three samples was sufficient for AMS radiocarbon measurements. 14C AMS measurement was performed in the XCAMS (The compact 14C accelerator mass spectrometer extended for 10Be and 26Al) at IUAC AMS facility (Sharma et al. Reference Sharma, Umapathy, Kumar, Ojha, Gargari, Joshi, Chopra and Kanjilal2019). Measured results for all the samples were normalized to the standard sample OX II and online delta 13C values were used for the isotopic fractionation corrections. Radiocarbon ages were calibrated using the OxCal 4.4 software with IntCal20 calibration curve (Reimer et al. Reference Reimer, Austin, Bard, Bayliss, Blackwell, Ramsey, Butzin, Cheng, Edwards, Friedrich, Grootes, Guilderson, Hajdas, Heaton, Hogg, Hughen, Kromer, Manning, Muscheler, Palmer, Pearson, van der Plicht, Reimer, Richards, Scott, Southon, Turney, Wacker, Adolphi, Büntgen, Capano, Fahrni, Fogtmann-Schulz, Friedrich, Köhler, Kudsk, Miyake, Olsen, Reinig, Sakamoto, Sookdeo and Talamo2020). Sample ID, pMC values, radiocarbon ages, and corresponding calibrated ages are listed in Table 4. Taking the clue from Cherinsky (Reference Cherkinsky2009) and to cross check the results from bioapatite and collagen fractions, a replicate of one sample collected from the ivory specimen from Harwadi was processed for collagen extraction using the protocol by Longin et al. (Reference Longin1971). However, collagen yield in this replicate sample was too low to perform graphitisation and AMS measurements.
DISCUSSION
The present work has yielded AMS dates on vertebrate fossil material ranging between 23,701 to 26,879 calendar years BC, as seen in Table 4.
These dates are a crucial step in confirming the Late Pleistocene age of the megafaunal assemblage at Harwadi. The presence of these important environmental faunal proxies like tiger, rhinos, hippos, elephants, and horses as well as several forest dwelling and tropical grassland plant species—at the Terminal phase of MIS 3, in the threshold of LGM—point to a stable population in a rich and diverse biological environment, which is far better preserved at sites like Harwadi compared to the rest of Peninsular India. This renders the Manjra valley assemblage as critically important in understanding the chronology of the megafauna of peninsular India in a primary context.
On another note, the material dated in the present study is co-terminous with dates obtained on molluscan shells from the site of Wangdari (Sathe Reference Sathe1989), which is the only Manjra Valley site to have yielded an isolated tooth of Stegodon insignis ganesa. This potentially extends the temporal frame of Stegodon in India a few thousand years further than what has been assumed till date, in the range of 30,000 BP (Mongabay 2021). The dates in the present study therefore could represent a new LAD for Stegodon insignis ganesa in Peninsular India.
CONCLUSION
The extraction of adequate bioapatite fraction from three samples from the Manjra valley enabled direct dating of fossilized bones, rather than associated materials such as molluscan shells, calcrete or volcanic ash, for the first time in the Indian Subcontinent. The method of sample preparation utilized in the present study has also seen success in the dating of similar collagen-deprived specimens from Brazil (Cherkinsky Reference Cherkinsky, Dantas and Cozzuol2013).
Sathe et al. (Reference Sathe, Rai and Agnihotri2018) demonstrated that isotope analyses on Hippopotamus from the Manjra Valley have shown the continuity of a C4 type of landscape, indicating the abundance of grasslands (which is substantiated by palynological evidence from the site of Harwadi). The dates from the present work provide a definite timeframe for these climatic and vegetative conditions, which have hitherto been conjectural due to the lack of precise dates from the sites.
It is in light of these observations that the AMS dates reported by the authors assume great significance in placing the Terminal Pleistocene in Peninsular India into a definite chronological frame, confirming its proximity to MIS 3.
The new dates on these megaherbivores (including environmentally sensitive taxa such as Hexaprotodon) provide a fresh perspective of an ecologically stable landscape during the terminal stages of MIS 3, experiencing dry semi-arid to wet semi-arid phase.
ACKNOWLEDGMENTS
Authors are thankful to IUAC for extending AMS facility for 14C funded by Ministry of Earth Science (MoES), Govt. of India with reference numbers MoES/16/07/11(i)-RDEAS and MoES/P.O.(Seismic)8(09)-Geochron/2012. Authors are grateful to Prof. S.N. Rajaguru of Deccan College, Pune for his valuable input and suggestions on the paper.