Evidence of Enhanced Winter Precipitation and the Prevalence of a Cool and Dry Climate

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The Holocene

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DOI: 10.1177/0959683607082403

2007 17: 889The HoloceneVandana Prasad, Binita Phartiyal and Anupam Sharma

to late Holocene in mainland Gujarat, Indiavidence of enhanced winter precipitation and the prevalence of a cool and dry climate during the mid

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nental and marine climatic records indicate a dry climatic phase

during the mid to late Holocene in India (Caratini et al., 1991,

1994; Nigam, 1993; Sukumaret al., 1993; Naidu, 1996; Phadtare,2000; Sarkaret al., 2000; Yadava and Ramesh, 2001). However,

because of variation in latitude, altitude and distance from the sea,

the dry and arid phase of the mid Holocene in various basins is not

synchronous (Kale et al., 2003). This dry phase also coincides

with the collapse of many old cultures eg, the Mesopotamian,

Syrian and Indus Valley civilizations. During the late Harappan

phase of the Indus civilization (50003500 yr BP), the western

regions were covered by many flourishing prehistoric settlements

(eg, Mohenjo-Daro, Jalipur, Taxila, Lothal) indicating a moist cli-

mate between 5000 and 3800 yr BP (Possehl, 1993, 1997).

Mainland Gujarat was also a part of the prehistoric settlements, as

is evident from the presence of vast archeological sites. The

Harappan culture was in full bloom during 50003400 yr BP inthis region (Possehl, 1993, 1997). It is considered that the chang-

ing mid-Holocene climate must have played an important role in

the rise and fall of the Harappan phase of the Indus civilization.

Substantial data on the geomorphology, neotectonics, sedimen-

tology and changing sea level has been generated from mainland

Introduction

Monsoon systems are the product of a thermodynamic atmos-pheric circulation, characterized by strong seasonality of wind

direction, temperature and precipitation (Ramage, 1971). The SW

monsoon system is one of the major climatic systems of the world,

having an impact over the Indian, the African subcontinents and

the western part of South East Asia (Overpeck et al., 1996).

Palaeoclimatic studies indicate strong SW monsoonal activity dur-

ing the early Holocene that continued with little variation until the

mid Holocene. Following the early-Holocene monsoon optimum a

progressively weakened monsoon and increased aridity were gen-

erally characteristic of the mid Holocene (Steig, 1999). Global

palaeoclimatic records show weakening of the SW monsoonal

precipitation during 50003500 yr BP and increased aridification

in the Northwest India, Pakistan, Arabia and Sahara regions (Petit-Maire et al., 1995). The weakening of the SW monsoon during the

mid Holocene was much more gradual in comparison with the gla-

cialinterglacial transition (Overpecket al., 1996). Various conti-

Abstract: The Kothiyakhad sedimentary sequence of Mahi estuary in mainland Gujarat, India, contains valuable

information on late- to mid-Holocene climatic conditions as inferred by phytolith, palynofacies, magnetic suscep-

tibility and clay mineralogical studies. Three distinct climatic regimes, ie, Phase I, II and III, were established.

Phase I (3660~3400 yr BP) shows a gradual weakening of SW monsoonal activity, though overlapped by

enhanced western disturbances which led to the development of cool climatic conditions. The coupled effect of

SW monsoon and enhanced winter precipitation produced improved hydrological conditions, which supported the

agrarian society of the Indus Valley civilization until the beginning of Phase II (~3400~3000 yr BP). During

Phase II the SW monsoon was in a state of severe recession, leading to severe drought-like conditions, other than

for a brief but intensely warm and humid pulse recorded at ~3320 yr BP, associated with SW monsoonal activity.

In Phase III (~30002850 yr BP), SW precipitation fluctuated greatly with a considerable increase in warm sum-

mer conditions, similar to present-day conditions. The weak SW monsoonal activity ~3500 yr BP also coincided

with a global cool and arid phase and this probably explains the timing as well as the cause of why the population

of the Indus civilization migrated to more humid areas to sustain their livelihoods.

Key words: Estuarine sediments, palynofacies, phytolith, magnetic susceptibility, clay mineralogy, palaeomon-

soon, Indus Valley civilization, Gujarat, India, Holocene.

The Holocene 17,7 (2007) pp. 889896

2007 SAGE Publications 10.1177/0959683607082403

*Author for correspondence (e-mail: [email protected])

Evidence of enhanced winterprecipitation and the prevalence of a

cool and dry climate during the mid to

late Holocene in mainland Gujarat, India

Vandana Prasad,* Binita Phartiyal and Anupam Sharma

(Birbal Sahni Institute of Palaeobotany, 53 University Road, Lucknow 226007, UP, India)

Received 17 November 2005; revised manuscript accepted 25 April 2007

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890 The Holocene 17,7 (2007)

Gujarat (Biswas, 1987; Merh and Chamyal, 1997; Maurya et al.,

1997, 2000; Rachna and Chamyal, 1998; Rachna et al., 1998, 1999,

2000). However, data of palaeoenvironmental significance from this

region is rather scanty (Rachna and Chamyal, 1998; Kusumgaret al.,

1998; Rachna et al., 1998). A multiproxy study involving phytoliths,

palynofacies, magnetic susceptibility and clay mineralogy has been

attempted with the aim of reconstructing the palaeoclimatic condi-

tions, based on the Kothyiakhad section, which has been identifiedas a type section by Rachna and Chamyal (1998).

Geomorphology of the study area

Mainland Gujarat is divided into four broad geomorphic zones:

the eastern upland zone, the shallow buried pediment zone, the

alluvial zone and the coastal zone (Maurya et al., 2000). The var-

ious geomorphic features include river cliffs, unpaired valley fill

terraces, modern point bars and mudflats. The rivers flowing in the

area, namely the Narmada, Dhadhar, Mahi and Sabarmati, origi-

nate in the eastern highlands (Deccan Traps and Arravali range)

and drain into the Gulf of Cambay (Chamyal et al., 2003). Well

preserved midlate Holocene sediments are exposed as valley fillterraces along the river channels and in estuarine settings. The

Mahi river arising at Aravalli, flows southwestward and runs for

about 275 km in Gujarat and finally enters an estuarine setting

before joining the Gulf of Cambay. The 2.5 m thick Kothiyakhad

section exposed at Kothiyakhad and Mujpur localities on the

northern and southern banks of the Mahi river, is an unpaired val-

ley fill terrace in the estuarine zone (Figure 1). The region has flat

alluvial plain topography dissected by numerous ravines. We have

also studied 2.0 m thick Bharuch and 7.8 m thick Itola sections

along the Narmada and Dhadhar rivers, respectively, for detailed

lithology for a regional correlation with the Kothyiakhad section

(Figure 2). The Bharuch section lies in the estuarine zone while

the Itola section is a fluvio-lacustrine deposit (Figure 1).

Material and methods

Detailed lithostratigraphy was established with respect to the 2.5 m,

2.0 m and 7.8 m sections at Kothiyakhad, Bharuch and Itola sections,

respectively, representing a large part of mainland Gujarat. This

enabled a regional correlation. The Kothiyakhad section was stud-

ied in detail for phytolith, magnetic susceptibility, palynofacies and

clay mineralogy, based on 14 samples, taken at regular intervals

from the exposed sediment succession consisting of alternating

sand, silts, silty-sand and organic-rich clays (Figure 2).

Phytoliths are amorphous silica particles that precipitate in and

or between the cells of living plant tissue, especially in grasses.Owing to their resistance to decay, fossil phytoliths are now being

increasingly used for the reconstruction of palaeovegetation pat-

terns, especially for deciphering forest/grassland ecotones

(Alexandre et al., 1997; Barboni et al., 1999; Blinnikov et al.,

2002). Deflocculation of sediment was achived by placing 5 g of

sediment sample in a 10% calgon solution overnight. The sus-

pended clay was siphoned out and the residue was washed with

distilled water several times. The sample was then treated with

10% HCl, and heated in a sand bath for 1020 min to remove the

carbonate content from the sediment. The residue was twice

washed using distilled water and dried. The organic content was

removed by heating the residue in 30% H2O2 in a sand bath for

2030 min depending on the richness of organic content of the

sediment. The remaining residue was again twice washed withdistilled water and dried. Phytolith extraction was achieved using

heavy liquid solution of CdI2and KI (specific gravity 2.3) and cen-

trifuged at 1000 r.p.m. for 5 min. This step was repeated until all

the material lighter than 2.3 was recovered. The phytoliths were

washed, dried and weighed. Dried phytoliths were mounted on a

glass slide using Canada balsam. Several slides were also mounted

in immersion oil to view the three-dimensional images of phy-

toliths. Phytolith identification was made under 400 and 1000

magnification on an Olympus BX51 microscope. At least

300400 counts were made from each sample in order to count

200 short cell morphotypes from each sample. The extracted phy-

toliths were counted and classified according to the classification

of Twiss et al. (1969), Twiss (1992) and Mulholland and Rapp(1992). However, multiplicity and redundancy of many phytoliths

morphotypes prevent the attribution of phytoliths to species and

genus (Rovener, 1971; Mulholland, 1989). Hence, in the present

study phytolith assemblages have been used to decipher fluctua-

tion in the past grass vegetation as a result of monsoonal variabil-

ity during the mid- to late-Holocene time interval in this region.

Figure 1 Location and geological map of the study area (modified after Rachna et al., 1998)



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Vandana Prasad et al.: Estuarine evidence of Holocene climatic changes in Gujarat, India 891

Figure 2 Lithology of the sections from A, Kothiyakhad; B, Bharuch; and C, Itola

Magnetic susceptibility () is controlled by the concentration and

the grain-size distribution of ferromagnetic minerals and provides a

valuable tool for precise correlation of sedimentation records(Thomson, 1975; Thompson and Oldfield, 1986; Verosub and

Roberts, 1995). Variation in shows gross changes in the relativeconcentrations of magnetic minerals. It has been used to infer cli-

matic change from marine (Thomson, 1975; Bloemendal et al.,

1988; Bloemendal and Menocal, 1989); loess and palaeosols

(Maher and Thomson, 1992; Verosub et al., 1993) and lacustrine

sequences (Gasse et al., 1994; Williamson et al., 1998; Phartiyal et

al., 2003). Magnetic susceptibility is strongly sensitive to variations

of the local climate and constitutes an accurate proxy record, along

with other parameters. Non-magnetic cubic plastic holders (10

cm3) were used and measurements for were done with a dual-frequency MS2 Bartington susceptibility meter. The values

reported here are the low-frequency measurements (460 Hz).Samples were analysed at the palaeomagnetic laboratory at the

Wadia Institute of Himalayan Geology, Dehradun.

Palynofacies study was applied with a view to monitor proxi-

maldistal relationships in relation to the clastic sediment source.

A palynofacies zonation scheme involving characterization of

various organic matter types, identification of palynomorphs and

their relative proportion, size spectra and preservation state in the

vertical profile have been applied to the characterization of deposi-

tional environment in terms of salinity (freshwater/brackish/marine),redox conditions, productivity and the stability of the water column

(stratified/seasonally stratified/continuous mixed) (Tyson, 1995).

Samples (5 g) were taken and treated with 10% HCl and heated in a

sand bath for 1020 min to remove the carbonate content from the

sediment. After washing with distilled water two to three times,

the sample was treated with 40% HF solution to dissolve the sili-

cates. Minimal oxidizing reagents were used and the samples were

washed thoroughly, centrifuged and the slides were prepared using

polyvinyle alcohol and mounted using Canada Balsam.

Clay minerals are known as palaeoenvironmantal indicators

because they are neoformed and thermodynamically most stable

under surface geological conditions. Generally the clay mineral

assemblage is controlled by the parent material as well as by the cli-mate. Although the technique of using clay minerals in deciphering

palaeoclimate is not yet routinely employed, it has been used

increasingly (Singer, 1980, 1987; Chamley, 1989; Vardachari et

al., 1994; Pal et al., 2000, 2003). Since clays are ubiquitous and

relatively easy to analyse, their use in palaeoenvironmental recon-

struction holds considerable attraction. Clays were separated by



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Unit II (0.91.5 m)Unit II is represented by an organic-rich clay horizon overlying

the 0.25 m sand bed. Phytolith data show an abrupt increase in

saddle, bilobate and cross morphotypes. Trapezoids and rondel

morphotypes occur in low proportions.High magnetic susceptibil-

ity is measured in the basal and middle parts, which gradually

decreases towards the top (Figure 3). The palynofacies of this Unit

shows a large proportion of well-preserved structured organic

matter and amorphous organic matter debris but a considerable

decrease in oxidized black and degraded brown organic matter

content. Freshwater dinoflagellate cysts represented byBosedinia

spp. and acritarchs occur in significant numbers whereas pro-

toperidinoids are present in small numbers and there is a complete

absence of gonyaulacoid dinocyst (Figure 5). The bulk mineralogy

of different samples of the unit is more or less similar to that of

Unit I. The dominant clay minerals are mica/illite and smectite

with very little halloysite.

Unit III (22.5 m)This unit is represented by silty clay and sand horizons of the upper

part of the Kothiyakhad section. Phytolith data show great fluctua-

tion in this unit. Amongst the various phytolith morphotypes, the

saddle type dominates in the phytolith assemblages. Bilobate and

cross type occur in moderate numbers. Comparatively low magneticsusceptibility values are encountered. The proportion of black oxi-

dized debris and degraded brown debris fluctuates. The well pre-

served structured organic matter and amorphous organic matter

content shows a decreasing trend at the base of this unit and increases

in the upper horizons. Pollen grains, freshwater dinoflagellates and

acritarchs occur in moderate numbers. Protoperidinoids are present in

significant numbers. Quartz, feldspar and mica/illite are the major

minerals found in this unit. The clay minerals are illite/mica and

smectite with little vermiculite and palygorskite at the top.

Palaeoenvironmental reconstructionOur results can be used to reveal three episodes of fluctuating cli-

mate in the Kothiyakhad section corresponding to Phase I, Phase

II and Phase III, respectively. The evidence and interpretations for

each of these three phases are summarized as follows.

Phase I (~36603400 yr BP)This phase shows deposition in a high-energy estuarine environ-

ment, as indicated by a larger proportion of coarser material in the

estuarine depocenter. The unsorted terrestrial organic matter and

low occurrences of protoperidinoids and gonyalacoid dinocyst

indicate that depositional sites close to the river mouth experi-

enced little tidal influence. A high percentage of black oxidized

debris and low occurrences of structured organic matter debris

point to oxidizing conditions at the sedimentwater interface. The

presence of Poaceae pollen grains and high susceptibility values indi-

cate the prevalence of arid climatic conditions during this phase.

Presence of smectite along with palygorskite, sepolite calcite/aragonite

and evaporites in the upper part of this Phase also indicate increasingarid conditions. Phytolith mophotypes recovered from this interval are

characteristic of Pooideae and Festucoideae grass subfamilies that

dominated during this interval and are also indicative of cool climatic

conditions perhaps as a result of frequent winter precipitation. How-

ever, extremely low occurrences of phytolith morphotypes belonging

Figure 4 Transmitted light microscopy images of selected phytoliths. All scale bars, 10 m. A, bilobate; BC, saddle; D, collapsed saddle; E,

trapezoid; F, cross; GI, rondel



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894 The Holocene 17,7 (2007)

to the subfamilies Panicoideae and Chloridoideae may be indica-

tive of weak SW monsoonal activity during this phase.

Phase II (~34003000 yr BP)This phase starts with the deposition of sand that is overlain by a dark

grey organic-rich clay sequence in a restricted estuarine setting. The

presence of a large proportion of well preserved structured, as wellas amorphous, organic matter content indicate the prevalence of

reducing conditions at the sedimentwater interface. An increase in

freshwater dinoflagellate and acritarch spp. indicates enhanced

freshwater supply under an estuarine setting that resulted in the

development of stratification of water masses and the establishment

of anoxic conditions at the sedimentwater interface. The formation

of low energy conditions with a stratified water column in the estu-

arine environment favoured the deposition of organic-rich clay dur-

ing this phase. The phytolith data indicate the dominance of a

morphotype belonging to the subfamily Panicoideae, Chloridoideae

grass cover indicating an increase in warm and humid conditions

associated with intense summer monsoon activity during this phase.

Enhanced susceptibility values during this phase can also be

explained by the intense water supply that, in turn, may have brought

more material from the catchment resulting in high values and/orby the in situ formation of ferromagnetic minerals during pedogene-

sis (Evan and Heller, 1994). This is further supported by the presence

of smectite, illite/mica and halloysite clay minerals.

Phase III (30002850 yr BP)This phase marks the return of silty clay and sand sedimentation

in the estuarine system. The lithology of this phase is more or less

similar to that of Phase I, where organic matter distribution indi-

cates a fluctuating anoxic/dysoxic conditions at the depositional

site. The phytolith data indicate fluctuating climatic conditions.

The large proportion of phytolith morphotypes belonging to the

subfamily Chloridoideae and moderate numbers of subfamilyPanicoideae point to a warm and humid climate with considerably

warm summer conditions resulting from fluctuating SW monsoon

activity. This is further supported by the larger proportions of pro-

toperidinoid cysts (heterotrophic dinocysts), indicative of eutroph-

ication conditions associated with an increased supply of nutrients

from the adjacent land mass (Matsuoka, 2001). The decreased

magnetic susceptibility values and reappearance of palygorskite

clay minerals also point towards a warmer but dry climate that can

be considered to be very similar to present day conditions.

Discussion

The lithological and other geological characteristics of Kothiakhad(Mahi river basin), Bharuch (Narmada river basin) and Itola

(Dhadhar river basin) show that the upper few metres of mid-

Holocene sediments are very similar, indicating a common deposi-

tional regime on both local and regional scales. The present-day

climatic conditions, particularly the monthly precipitation record of

this region, show maximum precipitation during summer months

(JuneSeptember) with almost no rains during the winter months

(DecemberApril). The semi-arid climate favours shrubs and grasses

over a woodland type of vegetation wherein the phytolith study

becomes a more promising palaeoecological tool for continental cli-

mate reconstruction. In addition, the palynofacies, magnetic suscep-

tibility and clay mineralogical parameters provide additional support

for the overall climate interpretations presented here.The multiproxy study carried out on the Kothyiakhad section

reveals considerable fluctuation in SW monsoonal activity during

the mid Holocene. A high percentage of black oxidized debris,

along with low occurrences of structured organic matter debris,

point to the presence of oxidizing conditions during 35003400 yrFigure 5 Palynofacies and clay mineralogy data plotted against the

lithocolumn



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BP. The grass phytolith data indicate a weak SW monsoon but

enhanced winter precipitation, leading to cool conditions in this

region. It is likely that the increased relative proportion of phy-

tolith morphotypes of cool season (C3) grasses over warm season

(C4) vegetation are a result of a greater length of the winter sea-

son during this phase. The sudden dominance of C3 grasses dur-

ing the dry phase of LGM of tropical South Africa has also beenattributed to increased winter rainfall activity (Scott, 2002).

Previous studies of salt lakes Didwana and Lunkaransar in the

Thar desert, Rajasthan area show greatest winter precipitation

between 5500 and 3500 yr BP (Singh, 1971; Swain et al., 1983;

Singh et al., 1990). The possibility of winter precipitation in the

Thar desert was further confirmed by Enzel et al. (1999) indicat-

ing a high water-table and improved hydrological conditions at

Lunkaransar lake after 5500 yr BP, the result of increased winter

rainfall. The high susceptibility values during this time span also

indicate dry conditions with a high rate of erosion in the adjoining

areas. The occurrence of evaporites (mainly gypsum) and second-

ary carbonate minerals further indicates arid climatic conditions

during this phase. The shift in climate, from warm and humid to a

dry phase during the mid to late Holocene, has also been wellrecorded at various locations on the Indian subcontinent (Caratini

et al., 1991, 1994; Nigam, 1993; Sukumar et al., 1993; Naidu,

1996; Phadtare, 2000; Sarkar et al., 2000; Yadava and Ramesh,

2001; Kale et al., 2003). Archaeological records show that the

Indus Valley civilization flourished between 5500 and 4500 yr

BP, which implies that the climatic conditions were favourable.

However, we know that during this time, the SW monsoon was on

the decline. This ambiguity is resolved by our data, which indicate

enhanced winter precipitation during this phase. The coincidence

of enhanced winter precipitation and a weak SW monsoon could

have maintained favourable hydrological conditions and so have

supported the Indus civilization (55004500 yr BP). This is

because winter rainfall has a much larger effect on percolation ofwater to the subsurface because of the reduced evaporative condi-

tions than are associated with increased SW monsoon alone (Enzel

et al., 1999). The net effect of a weaker SW monsoon and

increased winter precipitation made the critical difference

between conditions in the early and middle Holocene and elimi-

nated the drought conditions during the mature phase of the Indus

civilization. However, during the late phase of the Indus civiliza-

tion, the SW monsoonal activity decreased considerably and

almost ceased at 3400 yr BP, which resulted in severe drought

conditions at this time. Higher levels of received solar energy dur-

ing the mid to late Holocene may also have enhanced the interan-

nual variability of the summer monsoon and altered winter airflow

over South Asia, changing total annual precipitation and produc-

ing much drier conditions (Staubwasseret al., 2003).After the cold and dry phase, the SW monsoon regained its strength

~34003000 yr BP as characterized by the expansion of warm and

humid grasses. The increased primary productivity during this phase

also indicates high nutrient discharge in the estuarine system as a result

of greater freshwater runoff from the adjacent landmass. The sedi-

mentation of organic-rich clay under the influence of a warm and

humid climate and enhanced magnetic susceptibility, probably the

result ofin situ formation of ferromagnetic minerals during pedogen-

esis (Evan and Heller, 1994), further supports the conclusion of very

active SW monsoon conditions. The warm and humid pulse ~3320

3000 yr BP has also been recorded in various parts of the Indian penin-

sula (Sarkaret al., 2000; Yadava and Ramesh, 2001).

The phytolith data of ~30002850 yr BP show fluctuation in theSW monsoonal activity during this time. An increase in saddle

type phytolith morphotypes during this phase indicates intense

warm conditions during the summer months. The reappearance of

palygorskite clay minerals indicates the prevalence of arid cli-

matic conditions from 2850 yr BP onwards.

Conclusions

The mainland of Gujarat experienced considerable variation in the

occurrence of monsoonal activity during 36602850 yr BP. It is inter-

preted that the 36603400 yr BP palaeoclimatic records of

Kothiyakhad, correspond to the later phase of the well established

weakening phase of the SW monsoon that commenced from 5500 yrBP. During this period SW monsoon activity declined gradually and

almost ceased around 3400 yr BP. Winter precipitation, because of

more active western disturbances, during 36603400 yr BP was much

more pronounced and extended over larger parts of western India,

though this too declined ~3400 yr BP. This was the time when the

Indus civilization declined drastically in this region. The SW mon-

soon regained its strength with a brief pulse of enhanced precipitation

around 3320 yr BP along with minor subsequent fluctuations.

Further studies in the adjoining areas are currently in progress

with the intention of establishing a more complete record of mid-

Holocene monsoonal variability in the region.

Acknowledgements

Our sincere thanks to Dr N.C. Mehrotra, Director, BSIP, Lucknow

for his encouragement. This work was supported in part under

grant-in-aid project No. SR/S4/ES-49/2003 of the Department of

Science and Technology. Thanks are due to Professor L.S.

Chamyal and his research group for rendering help during field

work. We are grateful to the Department of Geology, Lucknow

University, Lucknow and the Wadia Institute of Himalayan

Geology, Dehradun for laboratory facilities.

References

Alexandre, A., Meunier, J.D., Lzine, A.M., Vincens, A. and

Schwartz, D. 1997: Phytoliths: indicators of grassland dynamics

during the late Holocene in intertropical Africa. Paleogeography,

Palaeoclimatology, Paleoecology 136, 21329.

Barboni, D., Bonnefille, R., Alexandre, A. and Meunier, J.D. 1999:

Phytolith as palaeoenvironmental indicators West Side Middle Awash

Valley, Ethopia. Paleogeography, Palaeoclimatology, Paleoecology

152, 87100.

Biswas, S.K. 1987: Regional tectonic framework, structure and evolution

of western marginal basins of India. Tectonophysics 135, 30727.

Blinnikov, M., Busacca, A. and Whitlock, C. 2002: Reconstruction

of the late Pleistocene grassland of Columbia basin, Washington,

USA, based on phytolith records in loess. Paleogeography,


Bloemendal, J. and Menocal, P.B. 1989: Evidences for a change inperiodicity of tropical climate cycles at 2.4 Myr from whole-core

magnetic susceptibility measurements.Nature 342, 897900.

Bloemendal, J., Lamb, B. and King, J.W. 1988: Paleoenvironmental

implications of rock-magnetic properties of late Quaternary cores

from the eastern equatorial Atlantic.Palaeoceanography 3, 6187.

Caratini, C., Fontugne, M., Pascal, J.P., Tissot, C. and Bentaleb, I.

1991: A major change at ca. 3500 years BP in the vegetation of the

Western Ghats in North Kanara, Karnataka. Current Science 61, 66972.

Caratini, C., Bentaleb, I., Morzadec-Kerfourn, M.T., Pascal, J.P.

and Tissot, C. 1994: A less humid climate since ca. 3500 yr B.P. from

marine cores off Karawar, western India. Paleogeography,


Chamley, H. 1989: Clay sedimentology. Springer, 623 pp.

Chamyal, L.S., Maurya, P.M. and Raj, R. 2003: Fluvial system of dry

lands of western India: a synthesis of Late Quaternary palaeoenvironmen-tal and tectonic changes. Quaternary International104, 6986.

Enzel, Y., Ely, L.L., Ramesh, R., Amit, R., Lazar, B., Rajaguru,

S.N., Baker, V.R. and Sandler, A. 1999: High-resolution Holocene

environmental changes in the Thar desert, North Western India.

Science 284, 12528.



9/9

896 The Holocene 17,7 (2007)

Evan, M.E. and Heller, F. 1994: Magnetic enhancement and palaeo-

climate. Study of a loess/paleosol couplet across the Loess Plateau of

China, Geophysics Journal International117, 25764.

Gasse, F., Cortigo, E., Disner, J.R., Ferry, L., Culbert, E., Kissel,

C., Laggovn-De Jorge, F., Lallier-Vergaes, E., Miskovsky, J.C.,

Ratsimbazafy, B., Ranavio, F., Taieb, M., VanCampo, E. and

Williamson, D. 1994: A 36ka environmental record in the southern

tropics of Lake Tritrivakely (Madagascar). C. R. Acadamy of SciencesParis 318, 151319.

Kale, V. S., Gupta, A. and Singhvi, A.K. 2003: Late Pliestocene

Holocene paleohydrology of Monsoon Asia. In Gregory, K.J. and

Benito, G., editors, Paleohydrology: understanding global change.

John Wiley and Sons, 21332.

Kusumgar, S., Rachna, R., Chamyal, L.S. and Yadav, M.G. 1998:

Holocene palaeoenvironmental changes in the lower Mahi basin,

Western India.Radiocarbon 40, 81923.

Maher, B.A. and Thompson, R. 1992: Palaeoclimatic significance of

the mineral magnetic record of the Chinese loess and paleosols.

Quaternary Research 37, 15570.

Matsuoka, K. 2001: Further evidence for a marine dinoflagelate cyst

as an indicator of eutrophication in Yokohama Port, Tokyo Bay,

Japan. Comments on the discussion by B. Dale. Science of the Total

Environment264, 22133.Maurya, D.M., Malik, J.N., Rachna, R. and Chamyal, L.S. 1997:

The Holocene valley fill terraces in the Lower Mahi valley, Gujarat.

Current Science 73, 53942.

Maurya, D.M., Rachna, R. and Chamyal, L.S. 2000: History of tec-

tonic evolution of Gujarat alluvial plains, western India, during

Quaternary: a review.Journal Geological Society of India 55, 34363.

Merh, S.S. and Chamyal, L.S. 1997: The Quaternary geology of Gujarat

alluvial plains.Indian National Science Academy Monograph 63, 198.

Mulholland, S.C. 1989: Phytolith shape frequencies in North Dakota

grasses: a comparison to general patterns. Journal of Archeological

Sciences 16, 489511.

Mulholland, S.C. and Rapp, G., Jr 1992: A morphological classifi-

cation of grass silica bodies. In Rapp, G., Jr and Mullholland, S.C.,

editors, Phytolith systematics. Emerging issues. Advances in

Archaeolical and Museum Science 1, 6590.Muller, G. 1967: Sedimentary petrology: I. Methods in sedimentary

petrology. Hafner Publishing, 183 pp.

Naidu, P.D. 1996: Onset of an arid climate at 3.5 ka in the tropics: evi-

dence from monsoon upwelling record. Current Science 71, 71518.

Nigam, R. 1993: Foraminifera and changing pattern of monsoon rain-

fall. Current Science 64, 93537.

Overpeck, J., Anderson, D., Trumbore, S. and Prell, W. 1996: The

Southwest Indian Monsoon over the last 18000 years. Climate

Dynamics 12, 21325.

Pal, D.K., Deshpande, S.B., Velayutham, M., Srivastava, P. and

Durge, S.B. 2000: Climate change and poly-genesis in vertisols of the

Purna valley (Maharashtra) and their management. Soil Science

Research Bulletin 83, National Bureau of Soil Science and Land Use

Planning, 35 pp.

Pal, D.K., Srivastava, P., Durge, S.L. and Bhattacharya, T. 2003:

Role of microtophotography in the formation of sodic soils in the

semi-arid part of the Indogangetic plains, India. Catena 51, 331.

Petit-Marie, N., Sanlaville, P. and Zwongwei, Y. 1995: Occilations

de la limite nord du domain des moussons Africaine, Indienne, et

Asiatique, au cours du dernier cycle climatique. Bulliten Societe

geologique France 66, 21320.

Phadtare, N. 2000: Sharp decrease in summer monsoon strength

40003500 cal yr B.P. in the central higher Himalaya of India based on

pollen evidence from Alpine peat. Quaternary Research 53, 12229.

Phartiyal, B., Appel, E., Blaha, U., Hoffmann, V. and Kotlia, B.S.

2003: Palaeoclimatic significance of magnetic properties from Late

Quaternary lacustrine sediments at Pithoragarh, Kumaun Lesser

Himalaya, India. Quaternary International108, 5162.

Possehl, G.L.1993: The date of Indus urbanization: a proposed

chronology for the pre-urban and urban Harappa phases. In Gail, A.

and Mevisson, G., editors, South Asian Archeology 1991. Steiner

Verlag, 23149.

1997: Climate and eclipse of the ancient cities of the Indus. In

Dalfis, H.N., Kukla, G. and Weiss, H., editors, Third Millennium BC

climate change and Old World collapse. NATO ASI Series I. Springer,

49, 193244.

Rachna, R. and Chamyal, L.S. 1998: Microfauna from a Holocene

valley fill terrace, Lower Mahi Basin, Gujarat. Journal

Paleontological Society India 43, 5567.

Rachna, R., Maurya, D.M. and Chamyal, L.S. 1998: Late

Quaternary sea level changes in Western India: evidence from Lower

Mahi valley. Current Science 74, 91014. 1999: Tectonic geomorphology of the Mahi river basin, Western

India.Journal Geological Society of India 54, 38798.

Rachna, R., Wadi, M.B., Maurya, D.M. and Chamyal, L.S. 2000:

Paleochannels in the Lower Mahi basin, Gujarat. Man and

Environment25, 1318.

Ramage, C.S. 1971:Monsoon meterology. Acedemic Press.

Rovener, I. 1971: Potential of opal phytoliths for use in paleoecolog-

ical reconstruction. Quaternary Research 1, 34359.

Sarkar, A., Ramesh, R., Somayajulu, B.L.K., Agnihotri, R., Jull,

A.J.T. and Burr, G.S. 2000: High resolution Holocene monsoon

record from the Eastern Arabian sea. Earth and Planetary Science

Letters 177, 20981.

Scott, L. 2002: Grass development under glacial and interglacial

conditions in Southern Africa: review of pollen, phytolith and isotope

evidence.Paleogeography, Palaeoclimatology, Paleoecology 177, 4757.Singer, A. 1980: The palaeoclimate interpretation of clay minerals in

soils and weathering profiles.Earth Science Review 21, 30326.

1987: Palaeoclimatic interpretation of clay minerals in sedi-

ments a review.Earth Science Review 21, 25193.

Singh, G. 1971: The Indus valley culture seen in the context of post-

glacial climatic and ecological studies in Northwest India.Archeology

and Physical Anthropology in Oceanica 6, 177189.

Singh, G., Wasson, R.J. and Agarwal, D.P. 1990: Vegetation and

seasonal climatic changes since the last full glacial in the Thar Desert,

Northwest India.Review of Palaeobotany and Palynology 64, 35158.

Staubwasser, M., Sirocho, F., Grootes, P.M. and Segl, M. 2003:

Climate change at the 4.2 ka BP termination of the Indus valley civi-

lization and Holocene south Asian monsoon variability. Geophysical

Science Letters 30, 14.

Steig, E.J. 1999: Mid Holocene climate change. Science 236, 148587.Sukumar, R., Ramesh, R., Pant, R.K. and Rajagopalan, G. 1993:

A 13C record of late Quaternary climate change from tropical peat inSouthern India.Nature 364, 703706.

Swain, A.M., Kutzbach, J.E. and Hastenrath, S. 1983: Estimates of

Holocene precipitation for Rajasthan, India, based on pollen and lake-

level data. Quaternary Research 19, 117.

Thompson, R. 1975: Magnetic susceptibility of lake sediments.

Limnology and Oceanography 20, 68798.

Thompson, R. and Oldfield, F. 1986: Envirommental magnetism.

Allen Unwin, 227 pp.

Twiss, P.C. 1992: Predicted world distribution of C3 and C4 grass

phytoliths In Rapp, G. and Mulholland, S.C., editors, Phytolith sys-

tematics. Emerging Issues: Advances in Archaeological and Museum

Science 1, 11328.

Twiss, P.C., Suess, E. and Smith, R.M. 1969: Morphological classi-

fication of grass phytoliths. Soil Science Society of America

Proceedings 33, 10915.

Tyson, R.V. 1995: Sedimentary organic matter. Organic facies and

palynofacies. Chapman and Hall, 615 pp.

Vardachari, C., Berman, A.K. and Gosh, K. 1994: Weathering of

silicate by organic acids II. Nature of residual products. Geoderma 61,

25168.

Verosub, K.L. and Roberts, A.P. 1995: Environmental magnetism: past,

present and future.Journal of Geophysical Research 100, 217592.

Verosub, K.L., Fine, P., Singer, M.J. and TenPas, J. 1993: Pedogenesis

and palaeoclimate: interpretation of the magnetic susceptibility record of

Chinese Loess-Palaeosol sequences, Geology 21, 101114.

Williamson, D., Jelinowska, A., Kissel, C., Tucholka, P., Gibert, E.,

Gasse, F., Massault, M.,Taieb, M., Van Campo, E.and

Wieckowski,E. 1998: Mineral magnetic proxies of erosion/oxidation cycles in tropical

marr-lake sediments (Lake Tritivakely, Madagascar): palaeoenvironmen-

tal implications.Earth and Planetary Science Letters 155, 20519.

Yadava, M.G. and Ramesh, R. 2001: Past rainfall and trace element

variation in a tropical speleothem from India. Mausam 52, 30716.

Evidence of Enhanced Winter Precipitation and the Prevalence of a Cool and Dry Climate

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