OSL Ages Research Articles

Quartz-tipped arrows older than 60 ka: further use-trace evidence from Sibudu, KwaZulu-Natal, South Africa

This paper discusses the results of a detailed functional study of 16 microlithic backed tools made on quartz, and newly excavated at Sibudu Cave, KwaZulu-Natal, South Africa. The layers associated with the artefacts have OSL ages of 61.7 ± 1.5 ka, 63.8 ± 2.5 ka and 64.7 ± 1.9 ka and represent the Howiesons Poort Industry at the site. I show that more than 50% of the pieces could hardly have been used in any way other than to tip arrows in a transverse position. This outcome supports previous inferences that some of these small stone tools, and perhaps a bone point from the same context, signify the use of bow and arrow technology during the Middle Stone Age. In addition to transversely hafted arrow tips, there is also evidence that some of the tools could have been hafted diagonally. Such tools could have been used equally successfully as arrow tips or barbs, or as barbs for hand-delivered spears. The variation in hafting configuration for these geometric shapes signifies hunting technologies that were flexible and most likely adapted according to need, preference, season and/or prey type.

Growth by extension, and reworking, of a south‐western Kalahari linear dune

ABSTRACTOptically stimulated luminescence (OSL) dating studies of linear (longitudinal) dunes have been used extensively to elucidate late Quaternary environments and climates in arid or formerly arid regions, yet understanding of the development of such dunes is incomplete. In particular, conflicting opinions have been presented regarding the propensity of linear dunes to migrate laterally, the degree to which they rework their own sediment during accumulation and whether they form primarily by extension, as opposed to lateral sand movement from adjacent interdunes. This study focuses on this last point, although the importance of the other controversies is discussed in context. A simple linear dune in the south‐western Kalahari, which has a prominent termination on a pan (playa) surface, provides an opportunity to directly test hypotheses of dune extension. Chronostratigraphy along a ~600 m transect along the crest of the dune, constrained by 42 OSL ages, reveals that the dune grew by extension on occasions in the late Pleistocene and early Holocene, but has also been subject to reworking along its length, which has continued until recent times. Dune development by extensional growth is suggested to operate under environmental conditions more conducive to net accumulation, whereas reworking is largely independent of conditions throughout the last ~18 ka, and may represent seasonal fluctuations in the position of the dune crest. The relative significance of these two modes of development is suggested to be a key control on the efficacy of linear dunes as archives of environmental and climatic change. Copyright © 2011 John Wiley & Sons, Ltd.

Optically stimulated luminescence and radiocarbon dating of samples from two Palaeolithic sites (Hahwagye-ri and Hwadae-ri) in the middle part of Korean Peninsula

OSL dating on sedimentary quartz grains from two archaeological sites in Korea, called Hahwagye-ri and Hwadae-ri, was undertaken to aid archaeological interpretation for the migratory routes of the Upper Palaeolithic and Mesolithic people in Korea. The Hahwagye-ri site is located on a river terrace of the North Han river at Kangwon prefecture and the Hwadae-ri is located on a river terrace of the Imjin river at Gyeonggi prefecture, both in the central region of Korean Peninsula. From the results of excavation conducted for recent two years, archaeologists strongly suggest that these areas would be an ideal camping place with relatively long-term residence for the Palaeolithic and/or Mesolithic foragers to get food resources by means of collecting, fishing and hunting. In order to check the quartz OSL results on the sediments at those excavation sites, radiocarbon dating was also carried out on a small series of finely layered charcoal samples. The OSL ages obtained showed a good stratigraphic correlation and were found to be in satisfactory agreement with those of the radiocarbon dating, implying that the incomplete bleaching of quartz grains, which is usually observed from fluvially deposited sediments, is not significant for these samples. These consistent ages also suggest that the quartz OSL dating can provide reliable age estimates in case that there are not enough materials suitable for other conventional tools for dating archaeologically important sediment layers. The resultant ages may provide important and useful chronological information for the Upper Palaeolithic and Mesolithic culture in Korean.

Terrestrial sensitivity to abrupt cooling recorded by aeolian activity in northwest Ohio, USA

Optically stimulated luminescence dated sand dunes and Pleistocene beach ridges in northwest Ohio are used to reconstruct landscape modification more than 5000 yr after deglaciation. Four of the OSL ages (13.3–11.1 ka) cluster around the Younger Dryas cold event, five ages (10.8–8.2 ka) cluster around the Preboreal, one young age (0.9–0.7 ka) records more recent aeolian activity, and one age of 15.1–13.1 ka dates a barrier spit in Lake Warren. In northwest Ohio, both landscape instability recorded by aeolian activity and a vegetation response recorded by pollen are coeval with the Younger Dryas. However, the climate conditions during the Preboreal resulting in aeolian activity are not recorded in the available pollen records. From this, we conclude that aeolian dunes and surfaces susceptible to deflation are sensitive to cooler, drier episodes of climate and can complement pollen data. Younger Dryas and Preboreal aged aeolian activity in northwestern Ohio coincides with aeolian records elsewhere in the Great Lakes region east of the prairie–forest ecotone.

Some aspects of age assessment of Holocene loess colluvium: OSL and 137Cs dating of sediment from Biała agricultural area, South Poland

At the end of the Pleistocene in Central-Eastern Europe, the accumulation of periglacial loess had already finished. From the end of loess accumulation to the establishment of grass cover and forest succession in this area, a phase of active modeling of the land surface by slope processes occurred. Before the beginning of the Holocene, this activity stopped and mollisol and alfisol formation started. These soils are preserved beneath Holocene colluvia. Until the Neolithic age, the area of loess formations in Poland was uninhabited. The extensive Neolithic agriculture locally induced soil erosion, causing slopewash on farmedslopes. The scale of this process and establishing the age of the successive stages of the prehistoric soil erosion in loess deposits in Poland is a key problem in the investigations of the human–environment relationship in prehistory. Chronostratigraphy of the preserved Holocene colluvia is very helpful in the solution of these problems. Optical (OSL) dating was applied in chronostratigraphical analyses. Due to expected partial bleaching during sediment transport, a single-aliquot regenerative dose protocol (SAR) was applied. Insufficient bleaching during transport on the slope is expected to be a serious problem for luminescence dating of loess colluvia, and causes overestimation of the OSL age. Quartz from the study site was suitable for age determination by SAR. The youngest 50-year old colluvia were also studied using the 137Cs method. The reliability of the obtained results is discussed in this paper, as well as the influence of environmental processes and type of the applied methods on chronological assignments. The precise age determination of loess colluvia is important for study of the human impact on the environment. The results of OSL dating show that soil erosion started in the Neolithic, with three phases of soil erosion: Neolithic, Middle Ages, and modern.

Reply to Preusser et al. on Frechen et al. “Late Pleistocene fluvial dynamics in the Hochrhein Valley in the upper Rhine Graben: chronological frame”

The River Rhine provides one of the most detailed late Cenozoic terrestrial records of fluvial activity in Europe triggered by climatic and tectonic activities (Boenigk and Frechen 2006). Frechen et al. (2008, 2010) provided OSLbased chronologies for the late Pleistocene and Holocene fluvial dynamics in the Hochrhein Valley and in the Upper Rhine Graben (URG). The OSL age estimates are in excellent agreement with the stratigraphical concept of sedimentary dynamics in the southern URG (see Frechen et al. 2008, 2010; Lammermann-Barthel et al. 2009). All samples taken from below an event layer (discontinuity) yielded OSL age estimates older than 20 ka and those from above the event layer gave estimates younger than 20 ka. The results are all in stratigraphic order and for the Holocene fluvial sediments in agreement with three radiocarbon ages. The validity of this approach was checked against known age samples from Bremgarten. A comparison between radiocarbon ages of wood and four OSL ages suggested that the OSL ages have a residual (due to insufficient bleaching) of maximum 1–2 ka. This residual value would be insignificant for sediments older than 10 ka. This information made us to decide the application of large aliquots for the fluvial sediments from the Hochrhein and from the URG. The problem of OSL age overestimation in fluvial and glaciofluvial environments is well-known, and we are of course aware of the great potential to overcome the problems of insufficient bleaching by using small aliquots or single grains and by applying statistical approaches. These latter approaches can indeed help improve the numerical dating, as demonstrated for fluvial sediments in the northern URG and the Lower Rhine area by our own group (e.g. Lauer et al. 2010, in press). However, even after applying statistical methods for luminescence dating to glaciofluvial and fluvial sediments, the luminescence age estimates may still be problematic. Overestimates up to 50% and greater were reported by DeLong and Arnold (2007) of single-aliquot measurements when compared to single-grain measurements from samples under 1,000 years old. Negligible differences were found for late Pleistocene samples from various regions and environments (DeLong and Arnold 2007; Porat et al. 2008; Thomas et al. 2005). Furthermore, Mayya et al. (2006) suggested that even for well-bleached samples, a heterogenous distribution of K-feldspar grains in a sample can cause a wide dose scatter. In the comment of Preusser et al., (this issue) the experimental design of Frechen et al. (2010) is questioned owing to the application of large aliquots, which are not sufficient to detect insufficiently bleached samples and thus result in age overestimation, a statement, which is already given in the paper under discussion by Frechen et al. (2010): ‘‘... De values ... from large aliquots ... are not suitable for detecting poor bleaching’’. Preusser et al. (this issue) claim that the application of small aliquots including statistical approaches result in ‘‘better’’ deposition ages for glacial and glaciofluvial sediments and that the OSL age M. Frechen (&) A. Techmer Leibniz Institute for Applied Geophysics (LIAG), Stilleweg 2, 30655 Hannover, Germany e-mail: Manfred.Frechen@liag-hannover.de

New optically stimulated luminescence ages provide evidence of MIS3 and MIS2 eolian activity on Black Mesa, northeastern Arizona, USA

Eolian deposition on the semiarid southern Colorado Plateau has been attributed to episodic aridity during the Quaternary Period. However, OSL ages from three topographically controlled (e.g. falling) dunes on Black Mesa in northeastern Arizona indicate that eolian sediments there were deposited in deep tributary valleys as early as 35–30 ka, with most sand deposited before 20 ka. In contrast, the oldest OSL ages for sand sheets fall within the Pleistocene-Holocene climatic transition (~ 12–8 ka). Thus most eolian sediment accumulated on Black Mesa under climatic conditions that were in general cooler, moister, and more variable than today, not more arid, pointing to a considerable increase in sediment supply.

Optical dating of Romanian loess: A comparison between silt-sized and sand-sized quartz

The loess-palaeosol sequence near Mircea Vodă (Dobrogea, SE Romania) is thought to comprise at least five glacial/interglacial cycles. It is considered as one of the most significant records of Late Quaternary environmental and climatic change in the region. Age information for the sequence was previously obtained through time–depth modeling of magnetic susceptibility data and optically stimulated luminescence dating (OSL) of fine silt-sized (4–11 μm) quartz. This study documents the granulometric properties of the sequence, and compares the OSL characteristics and age of fine sand-sized (63–90 μm) quartz to those of silt-sized quartz. OSL signals from both sand and silt-sized quartz are dominated by a thermally-stable fast decaying component. A suite of laboratory test confirms that the single-aliquot regenerative dose (SAR) protocol is suitable for these samples. Each grain-size fraction yields a set of optical ages that is consistent with the stratigraphic position of the samples. The ages obtained using sand-sized grains, however, are up to 70% higher than those obtained using silt-sized quartz. The discrepancy in age results is not understood as, according to procedural tests, the OSL signal from both fractions should be suitable for dating the deposits. As such, it cannot be established whether the uppermost weakly-developed palaeosol was formed during MIS3 or MIS5 and if the rate of loess accumulation varied during the Last Glacial, only by using standard SAR-OSL techniques. Both sets of ages do confirm, however, that the first well-developed palaeosol (S1) is of Last Interglacial age.

3-D geometry and luminescence chronology of Quaternary soft-sediment deformation structures in gravels, northeastern Brazil

This paper reports and describes soft-sediment deformation in gravels and gravelly sediments in Quaternary alluvial deposits of the Potiguar Basin, northeastern Brazil. Deformation structures were measured in terms of geometry, size, and relationship with sedimentary bedding using geological mapping and ground penetrating radar. TL and OSL/IRSL methods following MAR and SAR protocols were used to date sediments and soft-sediment deformation events. Our results indicate that soft-sediment deformation structures are widely distributed in several stratigraphic intervals of alluvial-channel deposits in a low-lying topographic valley. Depending on their geometry and composition, two types of soft-sediment deformation structures occur: pockets and dome-like load structures. These structures resulted from the shaking of sediments with a reverse density gradient system, which caused collapse and realignment of pebbles. These features are similar in morphology and size to modern examples of seismically-induced soft-sediment deformation in coarse sediments. TL and OSL ages indicate that sediment deposition and associated soft-sediment deformation occurred at least six times from ~ 352 ka to ~ 9 ka.

FORMATION OF MODERN YANGTZE ESTUARY AND SEDIMENTARY ENVIRONMENTAL EVOLUTION SINCE THE LAST DEGLACIATION

The present study measured OSL and 14C ages for late Quaternary sediments in a borehole drilled in the Chongming Island,Yangtze estuary.Lithology,microfossils,and sporopollen were further analyzed to discuss the formation of the modern Yangtze estuary and sedimentary environmental changes since the last deglaciation.The results indicate a lacustrine and marsh environment at the end of mid-Pleistocene.Fluvial facies dominates during late Pleistocene,especially gravel sediments of the riverbed prevailed during the last glaciation.With the sea level rise during the last deglaciation,estuarine and deltaic sedimentary systems developed successively in the study area.The rapid sea level rise during late deglaciation was demonstrated as rich marine microfossils and strong tidal intrusion in the present borehole sediments.Meanwhile,the high sedimentation rate indicates warm and humid monsoon climate and associated plentiful sediment discharge into the estuary during the early Holocene.

Shoreface sand supply and mid- to late Holocene aeolian dune formation on the storm-dominated macrotidal coast of the southern North Sea

Although pulses of coastal dune development in the course of the Holocene have been attributed to variations in the availability of sand, to modulation of sand supply by sea level change, and to changes in wind conditions, identifying the processes driving such pulses has been rather elusive. The shore deposits bordering the tide- and storm wave-dominated southern North Sea evince complex mid- to late Holocene stratigraphy and sediment heterogeneity. These deposits include a unique 7 km-long, 0.3–0.6 km-wide, and up to 7 m-high aeolian sand unit, the Ghyvelde dune, occurring astride the French–Belgian border in an apparently ‘anomalous’ inland location. The dune overlies, and is surrounded by, tidal sandy and muddy deposits incorporating freshwater peat. Data from four mechanical cores and eight auger holes, and three radiocarbon ages and one OSL age suggest that this inland dune was part of an ancestral North Sea sand flat and mudflat environment. Confronting the dune stratigraphy with the prevailing tide- and storm-controlled dynamics of shoreline progradation in this area indicates that dune formation occurred under a pulse of abundant sand supply resulting from the attachment, to a mid-Holocene North Sea tidal-flat shore, of a shoreface tidal bank under repeated storms. This mode of onshore sand supply generates extremely rapid progradation (up to 1 km over a century) of the sand flat shore, the surface of which serves as a large aeolian fetch zone for active backshore dune accumulation, while parts of this surface trap, locally, significant amounts of mud that are subsequently fossilised by aeolian sand. The potential influence of sea level and storminess in modulating the timing of shoreface sand supply and late Holocene coastal dune development in the southern North Sea, reported in studies from other areas, remains to be established.

Spatially variable sedimentary responses to orbitally driven pluvial climate during Marine Oxygen Isotope Stage 5.1, Dakhla Oasis region, Egypt

Pleistocene basinal sediments (PBS) in the Dakhla region of Egypt's hyperarid Western Desert comprise four facies: (A) fluvio-lacustrine, (B) mixed lacustrine/pluvio-eolian, (C) pluvio-eolian, and (D) mixed eolian/pluvio-eolian. Contiguity of basins containing each facies, and their stratigraphic position between two bajada gravel formations, P/B-II and P/B-III, confirm their equivalence. Facies A and B, with lacustrine components, are attributed to orbitally forced poleward incursion of the Intertropical Convergence Zone (ITCZ), resulting in increased summer insolation/temperature/precipitation. Facies C and D, comprising pluvio-eolian and eolian sediments, reflect geologic/topographic influences overprinted on regional 'pluvial' conditions, eliminating lacustrine response. A Th/U age of ∼ 62 ka on lacustrine marl within Facies B is minimal, and an OSL age of 110 ± 18 ka on sediments immediately below Facies B is maximal. Since bajada gravels P/B-III are the youngest Pleistocene formation, they must represent the final strong incursion of the ITCZ into the Dakhla region at MIS 5.1, ∼ 80 ka. Because PBS Facies A pass rapidly up into P/B-III bajada gravels, PBS are assigned to the rising limb of the MIS 5.1 insolation/temperature/precipitation curve, slightly younger than 80 ka.

Palaeoecological significance of Late Pleistocene pine macrofossils in the lower Guadalquivir Basin (Doñana natural park, southwestern Spain)

This paper reports on analysis of plant macrofossils in aeolian deposits exposed in El Asperillo cliff in the Province of Huelva. A significant find of a large number of macrofossils of Pinus ( Pinus pinaster Ait. and Pinus nigra Arnold) makes a major contribution to our understanding of the role of Pine in the Upper Pleistocene landscapes of Iberia. P. pinaster Ait. and P. nigra Arnold, are meso-microthermic species and inhabited valleys excavated in aeolian sediments mainly deposited during OIS 4 and OIS 3 (based on OSL and radiocarbon ages). Their presence in these valleys during the last part of OIS4 and OIS 3 reflects a significant fall in temperature during certain periods of these isotopic stages and helps us better understand the response of coastal dynamics to climate change.

Stratigraphic context and direct dating of the Neandertal mandible from Cova del Gegant (Sitges, Barcelona)

Stratigraphic study of the Cova del Gegant’s sedimentary fill revealed different cycles of accumulation of typical interior cave and delta facies. A precise chronology for these deposits, the faunal remains and stone tools contained therein was obtained by radiocarbon, U–Th and OSL. Our results indicate that the Upper Pleistocene archaeological sequence dates between 49.3 ± 1.8 ka BP, the U–Th age of the overlying flowstone, and 60.0 ± 3.9 ka BP, the OSL age of the basal deposits. We have also directly dated the site’s Neandertal mandible to 52.3 ± 2.3 ka by U–Th.

Early Holocene dune activity linked with final destruction of Glacial Lake Minong, eastern Upper Michigan, USA

The early Holocene final drainage of glacial Lake Minong is documented by 21 OSL ages on quartz sand from parabolic dunes and littoral terraces and one radiocarbon age from a lake sediment core adjacent to mapped paleoshorelines in interior eastern Upper Michigan. We employ a simple model wherein lake-level decline exposes unvegetated littoral sediment to deflation, resulting in dune building. Dunes formed subsequent to lake-level decline prior to stabilization by vegetation and provide minimum ages for lake-level decline. Optical ages range from 10.3 to 7.7 ka; 15 ages on dunes adjacent to the lowest Lake Minong shoreline suggest final water-level decline ∼ 9.1 ka. The clustering of optical ages from vertically separated dunes on both sides of the Nadoway–Gros Cap Barrier around 8.8 ka and a basal radiocarbon date behind the barrier (8120 ± 40 14C yr BP [9.1 cal ka BP]) support the hypothesis that the barrier was breached and the final lake-level drop to the Houghton Low occurred coincident with (1) high meltwater flux into the Superior basin and (2) an abrupt, negative shift in oxygen isotope values in Lake Huron.

Late Quaternary floods and droughts in the Nile valley, Sudan: new evidence from optically stimulated luminescence and AMS radiocarbon dating

Our results show that the late Pleistocene Nile in northern Sudan was shifting position and actively aggrading at 145 ± 20 kyr, 83 ± 24 kyr, 32 ± 8 kyr and 20.7 ± 0.2 kyr and indicate, for the first time, a phase of high-energy flow in the White Nile at 27.8 ± 3.2 kyr, with still high but somewhat reduced flow in that river at 13.3 kyr, 10 kyr and 4.8–4.0 kyr. Beach ridges associated with a 386 m strandline of the White Nile have OSL ages of 27.5 ± 2.7 kyr and 14.5 ± 1.6 kyr. The Holocene terraces and former channels of the main Nile have ages of 11 kyr, 6.5–5.0 kyr and 4.8–4.0 kyr, after which there was a general decline in flood discharge. The now arid main Nile valley in northern Sudan was significantly wetter during the early to middle Holocene, with a lake up to 450 km 2 in area, fed by an overflow channel from the early Holocene Nile between 9.5 kyr and 7.5 kyr. Previously stable late Pleistocene dunes were reactivated at intervals during the Holocene, with five samples from the White Nile valley indicating brief phases of Holocene dune activity at 9.9 ± 2.0 kyr, 9.0 ± 2.8 kyr, 6.6 ± 0.9 kyr, 4.8 ± 0.9 kyr and 2.9 ± 0.5 kyr, the earliest of which occurred within periods of generally wetter climate and higher Nile flow. The youngest freshwater shells on the Khor Abu Habl alluvial fan west of the White Nile correspond to a time of regionally wetter climate between 1.7 and 1.0 kyr. Our results suggest that millennial scale climatic instability may have been characteristic of Holocene climates in this region.

The last interglacial sea-level high stand on the southern Cape coastline of South Africa

The continental margin of southern South Africa exhibits an array of emergent marginal marine sediments permitting the reconstruction of long-term eustatic sea-level changes. We report a suite of optical luminescence ages and supplementary amino acid racemization data, which provide paleosea-level index points for three sites on this coastline. Deposits in the Swartvlei and Groot Brak estuaries display tidal inlet facies overlain by shoreface or eolian facies. Contemporary facies relations suggest a probable high stand 6.0-8.5 m above modern sea level (amsl). At Cape Agulhas, evidence of a past sea-level high stand comprises a gravel beach (ca. 3.8 m amsl) and an overlying sandy shoreface facies (up to 7.5 m amsl). OSL ages between 138±7 ka and 118±7 ka confirm a last interglacial age for all marginal marine facies. The high stand was followed by a sea-level regression that was associated with the accumulation of eolian dunes dating to between 122±7 ka and 113±6 ka. These data provide the first rigorous numerical age constraints for last interglacial sea-level fluctuations in this region, revealing the timing and elevation of the last interglacial high stand to broadly mirror a number of other far-field locations.

Still Bay and serrated points from Umhlatuzana Rock Shelter, Kwazulu-Natal, South Africa

Umhlatuzana Rock Shelter is a long-sequence Middle and Later Stone Age site in KwaZulu-Natal, South Africa. Jonathan Kaplan excavated the site and analysed the material in the 1980s as a rescue project. For many years thereafter the collection remained untouched, partly because of doubts raised about the stratigraphic integrity of the site. Using single-grain OSL dating we show that post-depositional mixing of sediment was restricted to time-specific, small-scale events. The OSL ages obtained for the Howiesons Poort and pre-Howiesons Poort are comparable to those of other southern African sites with unambiguous Howiesons Poort and Still Bay Industries. Based on morphological and other characteristics, we reason that the Still Bay is represented at Umhlatuzana, and announce the presence of a serrated point assemblage closely associated in time with the Still Bay points.

Palaeoflood Records from Upper Kaveri River, Southern India: Evidence for Discrete Floods During Holocene

Palaeoflood Records from Upper Kaveri River, Southern India: Evidence for Discrete Floods During Holocene A record of six discrete middle Holocene floods has been established based on sedimentological and stratigraphical studies in the upper Kaveri catchment at Siddapur. The flood events are represented by six discrete, sharp-bounded, sand-silt couplets. Texturally and geochemically the suite of couplets is quite distinct from the overlying and underlying structureless fluvial deposits. Based on OSL ages the suite of couplets cover the Holocene from ~8 to ~2 ka. Such evidence is not present or reported from any other river originating in the Western Ghat in the Indian Peninsula. We argue that the six couplets represent short-term, high discharge events or flash floods. The initiation of this phase of flash floods broadly corresponds with the southward migration of ITCZ and a gradual decline in Indian summer monsoon precipitation starting at ~7.8 ka. Comparison of the elevation of the highest couplet with the high flood level (HFL) of the 1961 extraordinary flood on Kaveri demonstrates that the 20th century flood was higher than the mid-Holocene palaeofloods.

Luminescence Dating of the Sediments from a Buried Channel Loop in Fatehabad Area, Haryana: Insight into Vedic Saraswati River and its Environment

Geomorphology and sedimentary composition of an archeologically important palaeochannel segment of the Vedic Saraswati River in northwestern Haryana have been evaluated and its temporal relation with the surrounding upland examined with the help of OSL dating. Sediment composition and OSL ages suggest that the channel received enough water supply between 5.9 and 4.3 ka ago, and even before. Several lakes and ponds had developed during this period in the surrounding areas. It was a wet phase in this area as well as in Rajastahn. After ~4.3 ka, the river got starved of regular water supply, became sluggish and finally dried up. Reduced water supply, indicative of decreased rainfall, occurred between 4.3 and 3.4 ka ago. The environmental history of the channel might have influenced the Harrapan archeology of the area.