Amundson Article

8/13/2019 Amundson Article

1/18

Harappa Excavations

1986 199A Multidisciplinary pproach toThird Mill ennium Urbani sm

dited by Richard Meadow

Monographs in World rchaeology No

PR HISTORY PRESS

M ad is on Wis co ns in


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Copyright 99 by the Individual Authors.

Prehistory Press7530 Westward WayMadison, Wisconsin 53717-2009

James A Knight, PublisherCarol J Bracewell, Managing Editor

All Rights ReservedManufactured in the U.S.A.

ISBN 0-9629110-1-1ISSN 1055-2316

Library of Congress Cataloging-in-Publication at a

Harappa excavations 1986-1990 : a multidisciplinary approach to third millennium urbanism /edited by Richard H. Meadow.

p. em. - - Monographs in wor ld archaeology, ISSN 1055-2316 : no. 3)Includes bibliographical references.ISBN 0-9629110-1-1 : 33.001. Harappa Site Pakistan) 2 Excavations Archaeology)- Pakistan. Meadow, Richard H. II Series.05392.2 H3H37 99934 - - dc20 91-39504

CIP

over art: Bowl on Stand H88-1002/192-17 associated with Burial 194ain Harappan Phase Cemetery see Figure 13.18).


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3

Pedology and Late Quaternary

nvironments Surrounding HarappaReview and Synthesis

Ronald mundson and Elise Pend allUniversity of California-Berkeley

A review and synthesis of pertinent pedological geological and paleoenvironmental studies in the vicinity ofHarappa District Sahiwal Punjab, Pakistan suggest that a wealth of research opportunities exists for earth scientistsinterested in contributing to an understanding of the origins and later decline of the Indus civilization.

Harappa lies near the apex of the Holocene alluvial fan of the river Ravi on an alluvial deposit of late Pleistoceneage. Soil patterns around Harappa indicate several periods of river meandering and channel infilling.

Stable isotopes in pedogenic carbonates of a soil buried by early occupation offer potential insights into pre-Harappan environmental conditions. Although carbon isotope ratios are difficult to interpret unambiguously, theysuggest either a very arid sparsely vegetated site matching presumed latest Pleistocene conditions or a nearly pure C4flora indicative of a tropical grassland presumed early Holocene conditions . Oxygen isotope ratios in the carbonateare also difficult to interpret due to a lack of knowledgeof the isotopic composition of present precipitation. Dependingon the temperature at which the carbonates formed the oxygen isotope ratios in the carbonate could indicate that preHarappan conditions were either similar to the present or that a stronger monsoon may haveexisted.

The anc ient city of Harappa like other cities ofthe Indus civilization, should be studied in thecon text o f i ts contemporaneous environment

Butzer 1982 , as well as in relation to conditionswhich preceded its inception an d followed its demise.Environmental an d geologic factors such as climate,vegetation flooding, an d sedimentation to name afew, no t only determine the suitabi li ty of a s it e forhabitation, bu t ca n ultimately help shape the culturewhich evolves Amundson an d Jenny 1991 .

Numerous approaches are becoming available toarchaeologists interested in reconstructing past environments. In this paper we report o n o ur initial pedological work at Harappa an d i ts relat ionship to themore regional conditions in the Punjab. In addit ion,we review some of the important previous studies ofthe climate an d geology of t he region to provide acontext for our work at Harappa an d to provide ageneral overview of much of the area once inhabitedby the peoples of the Indus Valley Civilization.

limate of the Punjab

The presen t day summer monsoon circulation ofPakistan is driven by the relative warmth of the SouthAsian l and mass relat ive to the surrounding oceans COHMAP Members 1988 . Winters are cool to cold,with occasional disturbances or iginating from th eMediterranean Sea. From April to June land masstemperatures increase greatly with maximums of50C o r mor e being recorded in the southern Punjab Pakistan Meteorological Department 1986 . Thesetemperatures set up the Indus low, which is associated with a south-westerly, but dry, monsoon. DuringMay an assoc ia ted low pressure trough developsover the Ganges , which is fed b y moi st a ir from theBay of Bengal. The upward surging, warm moist airof this trough reaches the Punjab in late June or earlyJuly marking th e onset of summer precipitationwhich commonly continues until late August. FromSeptember through November a transit ion from the


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Harappa Excavations 1986 1990: Multidisciplinary pproach

s u m me r m o ns o on to th e cool, dry w i nt e r p e ri o doccurs. At Sahiwal, about 12 km NE of Harappa, themean annual temperature is about 26C an d the meanannual precipitation is about 260 mm, 70 of whichfalls between July an d September Greenman et a1.1967).

The general character o f t he prehistoric climate of

South Asia has been debated fo r many years s eeMeadow 1989 for summary). While some scholars feelthat there ha s been little change in climate since theend of th e Pleistocene, others suggest that it hasvaried great ly from the last glacial maximum (18,000years BP) to t he present. Model calculations for thepast 18,000 years, based on inpu t parameters oforbitally determined insolation, ice-sheet orography,a tmosphe r ic CO 2 concentrations, and sea surfacetemperatures (as well a s o th er inputs , suggest thatduring the late Pleistocene, South Asia wa s colder an dd rie r t ha n t he present , with a grea t ly weakenedsummer monsoon du e to factors such as highly reflect ive ice sheets COHMAP Members 1988). Thisprediction appears to be supported by field evidencein the sediment stratigraphy of several small salt lakesin th e arid to semi-a rid be lt o f weste rn Rajasthan,India (Singh 1971; Singh et al. 1974; Bryson an d Swain1981). Pre-Holocene (> 10,000 years BP) sedimentsconsisting of loosely-packed aeolian sand, indicatethat the lakes were dry an d that the presently stabilized sand dunes were active. Singh et al. (1974) haveinterpreted the pre-Holocene conditions to have beenextremely arid an d possibly windy.

The increased summer, an d decreased winter, insolation proposed for the early Holocene would havegreatly enhanced the summer monsoon of South Asia.The Asian land mass ma y have been 2 to 4C warmerthan present, an d increased summer rainfall, relativeto the p resent , i s predicted to have fallen over SouthAsia. After 6,000 years BP, th e summer insolationappears to have decreased, with the monsoonal windsan d associated rainfall predicted to have declined topresent levels. Singh s interpretations of the lake sediments of western Rajasthan appear to support thesemodel predictions an d also provide a more detailedenv ironmenta l h i sto ry of th e region. Laminated,pollen-bearing, lacustrine sediments accumulatedfrom the early Holocene unti l approximately 3,000years BP, at which time there is possible evidence fordesiccation (Singh 1971). Qualitatively, the pollen inal l th e l acust r ine sed imen t s sugges t s fa r greaterprecipitation t ha n a t the present t ime. Using the lakepollen data in conjunction with statist ical relationships between present-day pollen an d climate, Brysonan d Swain (1981) have estimated that the precipitationof western Rajasthan between 10,000 to ,,3,500 yearsBP may h av e b ee n three t imes that of the p resen t.

Singh (1971) and Singh et a1. (1974) have distinguished several d is ti n ct p o ll e n z o ne s w it h in thsediments, with each zone indicative of changingclimatic (as well as cultural) conditions.

The early Holocene appears to have been an opes teppe rich in grasses, Artemisia and sedges. Aapproximately 7,500 years BP, the appearance of char

coal an d Cerealia-type pollen is believed by thesauthors to s ignal the appearance of early agriculturan d land al terat ion. An apparent increase in mesphytic vegetation between 5,000 to 3,000 years BP winterpreted by Singh (1971) an d Singh et al. (1974) tpossibly represent th e m ois te s t pe ri od of thHolocene. However, the later analysis of the d at a bBryson an d Swain (1981) seems to ind ica te tha t theperiod wa s n o t g re at ly d if fe re nt t ha n those thpreceded it.

A r educ tion in annual precipitation rates woulhave been especially detrimental to the non-riverinsettlements in western Rajasthan, an d the desiccatio

of the lakesat approximately

4,000 to 3,000 yearsB

may correspond to th e disappearance of th e Inducultu re in western Rajasthan Agrawal et a1. 196Singh 1971). However, the influence of such a climatechange on riverine settlements, such as Harappa andMohenjo-daro, is more difficult to assess. (See Misra1984 for a critical assessment of Singh s data).

ology and eomorphologyof the iver avi

Th e present day floodplains of th e Indus rivsystem lie atop a sequence of alluvial deposits manthousands of

feet thick. Therapidly changing

chan els of th e Indus an d it s t r ibutaries at t racted thattention of many of t he e ar ly g e og r ap h er s in thregion (Raverty 1892; Oldham 1874; Oldham 188many of w ho m r ec og ni ze d t he significancearchaeological and historical studies Wood 192Whitehead 1932).

The upper region of the Ravi (as well as other Indutributaries) is entrenched several or more meters intits own, Pleistocene-aged, alluvium (Figure 3.1) (AbuBakr an d Jackson 1964), w hi le i n i ts l ow er reacheprior to entering the Chenab, the older alluviumbu ri ed benea th a l luv ium of Holocene a ge . Th

Pleistocene-aged alluvial terraceswhich

riseprom

nently above th e present f loodpla ins , a re locallreferred to as bar Whitehead 1932; Mian an d Sy1986) an d h av e b ee n recognized since some of thearliest studies as containing prominent concentrt ions of kankar or pedogen ic ca lcium carbona tenodules Wood 1924). h as b ee n recognized ththese geomorphically stable terraces ar e sites fsettlements of g re a t a n ti qu it y Wood 1924


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Pedology and ate ua ternary nvironments Surrounding arappa

LEGEND PLEISTOCENE RIVER TERRACEStiiii i Level or Uplands

mFLOOD PLAINSSubrecen loodplolnLOO PLAINS Recent loodplains A. . To

p A

/\

\

//

\~ ,

f

~ -

-

\

o, 100,

,--- / \--

- ~\I

zoo .. .,

Figure 3.1: Generalized geomorphological ma p of Pakistan showing major cities, site locations, rivers, an dalluvial landforms. Modified from Mian an d Syal 1986 , taken from Pendall an d Amundson 199Oa .

Table 3.1: Calculated Slopes of some Landforms inthe Vicinity of Harappa.

entrenched approximately 10 m. This b r or terrace,is more steeply dipping than the present Ravi Table3.t and, based on i ts slope, should plunge beneath

the present land surface near the village of Pattoke,approximately 60 km SW of Lahore Figure 3.3 .Major changes in irrigation patterns near Pattokereveal this geomorphic change. The age of the terraceon which Lahore resides is certainly Pleistocene in ageb as ed o n n r development in the soil Mian an dSyal 1986 an d i ts height above the present river Ravi.A more precise assignment of age is no t possible with-ou t detailed fieldwork an d radiometric dating.

The major irrigation canal on the Pleistocene terraceis the Upper Bari Doab canal. For the purposes of thispaper, we will informally name this terrace the UpperBari Doab terrace. On this terrace, distributary channels

Whitehead 1932 suggested that Harappa lies on anold terrace of the Ravi and provided a very generalma p showing the partial extent of this terrace.

Detailed geomorphic studies of the central section ofthe r iver Ravi including th e area around Harappahave no t been made, although a reconnaissance studyof the upper section mainly in India Mahr 1986 an dgeneral studies of it s lower section near t he r iv erChenab Wood 1924; Wilhelmy 1969 have beenpublished. In this paper, we present a preliminary ma pof a port ion of the geomorphology from the Indianborder to the r iver Chenab. The ma p was constructedbased on interpretat ions of t opo graphi c m apspublished by the U.S. Army Corps of Engineers 1955an d Couchman 1936 . Scattered elevation data fromth e maps were used to prepare topographic cross

sections. Th e pattern of irrigation canal systems,which, as Wood 1924 noted, are mainly the controlleddiversions of present rivers into channels that followold beds, was also used to assess landform patterns.

The p re se nt g ra di en t o f t he river Ravi is roughlyl inear f rom th e Indian border to the r iver Chenab Figure 3.2 , with a slope of approximately 29 cm/km Table 3.t . The city of Lahore lies atop an old alluvialdeposit into which the present river Ravi has

Landform

River RaviPleistocene Terrace

Upper Bari DoabChenab River near Multan

Slope m/km

0.2870.340

0.204


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Harappa Excavations 1986 199 : A Multidisciplinary Approach

Ravi R iv er

Pleistocene terrace

Pattoke

Harappa

50 0

60 0

70 0-

-

40 0 L . . - - - - - _ - - L . . _ . . . L . . . - _ . l . . . - - - - - - - - - L _ - - - - - - - I 3 2 1 1

D i s t a n c e f r o m L a h o r e k m

Figure 3.2: Topographic cross-section of th e river Ravi from t he I nd ia n border to itsjunction w it h t he river Chenab. Th e Pleistocene terrace is the Upper Bari Doab terraceillustrated in Figure 3.3.

radiate from the main canals at relatively acute angles.Th e entire canal system terminates abruptly at Pattoke,marking the point where the terrace becomes buried byyounger alluvium.

Just downslope f rom Pattoke, t he lower Bari Doabcanal d ivert s wate r f ro m t he Ravi an d distributes itover a relatively low, narrow terrace to t he s ou th o fth e present Ravi f loodplain. I n t hi s paper, we willinformally call this th e Lower Bari Doab terrace. Th edistributary channels from this canal radiate outwardat greater angles than those of th e Upper Bari Doabterrace. This canal system ends approximately 25 km

SW of Sahiwal (formerly Montgomery), which is nearHarappa. On the south , the terrace an d the irrigationsystem) ends at a prominent escarpment that dropsdown to th e abandoned channel of the river Beas. Onthe north, an escarpment is no t prominently indicatedon topographic maps. Th e s lo pe o f t he terrace is no tknown due to inadequate elevation data on availablemaps. Th e exact a ge of th e terrace is also not known,although generalized geologic (Abu Bakr an d Jackson1964) and geomorphic maps Mian an d Syal 1986)suggest a Pleistocene age. Th e terrace is younger thanthe Upper Bari Doab terrace since its alluvium buriest ha t o f t he o ld er terrace. Whitehead (1932) suggested

that Harappa lies on th e edge of what we call theLower Bari Doab terrace, b ut , a s will e discussed inthe following section, the re lat ionship is n o t u na mbiguous.

To the southwest of Harappa, numerous irrigationcanals branch off mainly to th e south o f t he presentda y river Ravi and extend as fa r a s M ul ta n Figure3.3). These canals appear to outline th e major area ofHolocene deposition by th e Ravi or it s w et alluvial

fan Schumm 1977). At th e present time, th e Ravnear the nor thernmost ex ten t of it s fan. Severauthors, however, have suggested that, as recently1500 AD, the Ravi flowed at the southernmost exto f i ts fan an d e n te re d t he Beas, and ultimatelyChenab, far south of Mult an Wood 1924; Wilhelm1969). Thus, in rough ly th e past 500 yea rs , t he Rha s migrated northward almost 70 km.

Th e rapid an d extreme shifts in river courses onIndo-Gangetic plain ar e well documented (Cole aChitale 1966; Lambrick 1967; Wilhelmy 1969). Raprises in the base of r ive r beds , due to deposition

alluvium, lead to sudden breaks in levees, particularduring flood events. Ne w channels a re then formedadjacent areas of lower e levat ion . Th is p rocess hasbeen termed r iver avuls ion Schumm 1977).

River avulsion has important archaeological signifcance. For example, Alexander sailed his barge tojunction of th e Chenab an d Ravi rivers in 326-325 T he e xa ct l oc at io n o f this event is now difficultassess g iven the dynamic nature of these two rive Wood 1924). As a second example, archaeologicalsites of great antiquity m ay n ot have been preserveon the Holocene fan of the r iver Ravi, to the southwesof Harappa , a s a result of frequent river avulsion asediment deposition.

For Harappa itself, th e dynamics o f t he river Rma y have played a significant role. Although Harappappears to e upslope of the apex of the Ravi s alluvifan, t he r ive r does appear to have migrated signcantly, near H a ra pp a a n d also upstream, withinrelatively narrow valley. Harappa lies some 12sou th of the present Ravi river, but th e modem toan d ancient site ar e located on th e southern bank o


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Figure : A reconnaissance geomorphological m p of a sectionof the river Ravi. The relative agesequence of the alluvial deposits, from oldest to youngest is: Upper Bari Doab terrace, Lower BariDoab terrace, nd Holocene alluvial fan. Both the pper nd Lower Bari Doab terraces rebelieved to be Pleistocene in age.

Lyl/Ql u,

Sco/e in ilo . .f. so 10

,

rlo

loc AIIlJI/iGl

/ 1ulro l

h ~ n o i V l r


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arappa Excavations 1986 199 : Multidisciplinary pproach

conspicuous channel that often carries water duringthe summer monsoon floods. This channel bifurcatesfrom th e Ravi 83 km upstream of Harap pa , nearPattoke, an d rejoins th e r iver approximately 14 kmdownstream from the site. This channel was probablyonce the main course of the Ravi, but the t ime o f i tsabandonment is unknown. An unders tand ing o f the

t iming o f t he se events i s i m po r ta n t for an understanding of the environmental factors which affectedthe people of Harappa.

Soils and eomorphologySurrounding arappa

The topography a round Harappa , with the exception of th e archaeological mound itself, is relativelysubdued. Field work suggests that onlya meter or lessof relief commonly exists between geomorphic unitsof significantly different ages. In some cases, thesetopographic differences have been obscured by agri

cultural activity. Thus, detailed geomorphic mappingis difficult on the basis of surficial features alone.In recent years, the use of soils as an aid in geomor

phic mapping Marchand an d Allwardt 1981; Lettis1985 , particularly in archaeological settings Holliday1990 , has greatly increased. Soil properties are funct ional ly re la ted to a handful of environmental,g eo lo gi ca l J en ny 1941 , and anthropological Amundson and Jenny 1991 factors. Of particularinterest in geomorphic studies is th e chronologicalr elat ionsh ip be tween the age of an alluvial depositan d the propert ies of the soil tha t forms in it.

In 1988, a detailed mapping of th e soils around

Harappa wa s undertaken. This work was supplemented with results of preliminary investigations in1987. Soils were cored to depths of 150 to 300 cm, atapproximately 200 m intervals, along north-southtransects Figure 3.4 . Each 15 cm increment of the soilcore was characterized for Munse ll color, t exture,consistence, and abundance and morphology ofcalcite, gypsum, an d more soluble salts Soil SurveyStaff 1981 . Depth to unwea the red a lluv ium or to awater table wa s also noted . For an additional discussion of th e m et ho ds a nd th e r es ul ts of chemicalanalyses of th e soils, se e Pendall and Amundson 1990a .

Based on their field properties, the 65 soils that wereexamined were grouped in to e igh t mapping units.One additional m a p pi n g u n it wa s also defined toshow the dis tr ibu tion o f t he archaeological moundan d the presently-inhabited Harappa village Figure3.4 . A summary of the typical field propert ies of themajor soil types are given in Table 3.2.

The soil units display two prominent patterns: 1 as inuous east -wes t band to th e north of Harappa

abandoned channel of the river Ravi an d 2 a serof paral lel , semi-ci rcular bands surrounding tarchaeological mound on th e east, south, and weBased on topographic relationships an d soil propeties, the soil units reflect alluvial deposits of differingages that were deposited in meander channels arounHarappa.

A brief description of th e major soil units followFor greater detail, see Pendall an d Amundson 1990The Recent Channel unit Rc, Figure 3.4 is on tlowest-lying portion of th e landscape in tentrenched, abandoned channel of the river Ravi. Thsoil is very weakly developed an d relatively coarstextured Table 3.2 . The Subrecent Channel unitan d Sc/16, Figure 3.4 , which is located at a slighhigher elevation, circles Harappa on the east, soutan d west. The so il is commonly silt loam in textuhas a slightly darkened A horizon, an d wa s foundcontain small pottery fragments in unweathered alvium several meters b el ow t he present surfac

Approximately parallel to the Subrecent Channel unit,bu t located on both sides, is the Sultanpur soil unitan d 16gc, Figure 3.4 which contains weakly-deveoped carbonate nodules i.e., k nk r an d occasionalgypsum nodules. Exhibiting th e same degree of sdevelopment, but greater variability in texture atopography, is the Sultanpur levee complex 17, 17SFigure 3.4 . Also roughly paralle l to th e SubrecenChannel unit, an d found on both sites, are the Gambe 18g, Figure 3.4 and Lyallpur 19, Figure 3.4 sunits. The Gamber soils are relatively well-developedan d contain significant quantities of gypsum nodulThe Lya llpur un it , found main ly to t he w es t of

archaeological mound, contains large an d abundacarbonate nodules. Finally, at the highest elevationth e survey to th e northwest of th e archaeologicalmound, an d underlying it at Cemetery R37, isQadirabad soil unit 20, Figure 3.4 . This soil exhibitsth e greatest degree of development in th e viciniw i th l arge and abundant carbona te nodu les apossible clay accumulation in the B horizon.

Based on topographic re la t ionsh ips and th e sproperties described above an d elsewhere Pendand Amundson 1990a , th e following sequencegeologic events can b e reconstructed for t he a rimmediately surrounding Harappa Table 3.3 . T

survey a rea de linea ted in Figure 3.4 was probablonce filled with an alluvial unit contemporaneousage with the alluvium of the Qadirabad soil unit Figure 3.4 . The exact age of the deposit is not knowal though it is generally believed to be l atePleistocene in age Mian an d SyaI1986 . A 14 : datea carbonate nodule from th e Qadirabad soilCemetery R37 gave an age of 7,08O120 years BP B21520 . Considering that it takes at least several tho


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SOIL M P OF H R PP N V N TYLEGEND

paved rood unpaved rood, cart track soil boundary ....... u stream terrace

. - hili or moundC 0 buildIngs, selliement00 t l mosque I shrine

l:1 benchmarkX soil d es cr ip ti on site

~ t ~ orchard=. . . ; ; conal

_ drain

o old police stationo 1I I I

Scale in Kilometers

IXII

Figure 3.4: Soil map of the region immediately surrounding Harappa. Mapping units are discussed in the text.Abbreviations for mapping units are: C Cg: Cultural material Cultural material with gypsum; Rc: Recent channel;Sc, Sc/16: Subrecent channel Subrecent channel overlying Sultanpur; 16, 16gc: Sultanpur Sultanpur gypsum pluscalcite phase; 17, 17/5: Sultanpur Levee Remnant Complex Sultanpur Levee Remnant Complex shallow over sand;18g: Gamber; 19: Lyllpur; 20: Qadirabad. FromPendall and Amundson 1990a .


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Harappa Excavations 1986 199 : A Multidisciplinary Approach

Table 3.2: Field Descriptions of Typifying Soils of Mapping Units.Effervescence Morphology of CaC03

Depth Munsell of or CaS04 SegregatioMapping Unit Horizon (cm) Color Texture l Carbonates 2 pH3 Abundance an d Siz

Recent Channel Ap 0-19 lOYR4/3 s il es 7.95[Rc.]

C1 19-43 10YR4/3 to si l es 8.004/ 4

C2 43-75 lOYR4/3 sl e n l7.5YR4/4

C3 75-100 lOYR4/2 to sl eo n l2.5Y4/2

Subrecent Ap 0-15 lOYR4/4 sil ev 8.05Channel [Sc.]

C 15-280 10YRS/4 to2.5Y5/4

si l ev 8.15

Sultanpur [16.]

Gamber, gypsumphase [18g.]

ApBwBk1

Bk2BCk1BCk2

Ck

ApBwBy1By2BCy1

BCy2

0-1515-4545-85

85-120120-140140-163

163-1930-15

15-6060-8686-114

114-140

140-150

lOYR4/410YRS/410YRS/4

10YRS/4lOYRS/4lOYRS/4 to2.5Y5/42.5Y5/4lOYR4/4lOYRS/410YRS/47.5YR5/410YR5/4 7.5YR5/4)lOYRS/4

si lsi lsi l

si Isi lsi l

si lsi lsi lsi lsicl

sil( sicl)

si l

evevev

evevev

evevevevese

e

8.05n l

7.90n ln ln l

n l

8.05n l

7.95n l

8.10

n l

f, s CaC03)

f, s m (C aC03)f to c, s m (CaC03)f, s c, m (CaC03)

f, s (CaS04)m, m I (CaS04)f to c, s m (CaS04)

c, m I (CaS04)

180-210

0-20

20-6060-120

120-168

Lyallpur [19.] Ap

BwBkBky1

Bky2

C

10YR4/3

10YR6/42.5Y5/42.5YR5/4lOYRS/4

168-180 2.5Y6/410YRS/42.5Y6/4

si l

si lsi lsi l

si l

si l

es

eseses

es

e

8.35

8.30n l

8.00

n l

n l

f, s m (Ca C03)f, s (CaC03)c, s m (CaC03)c to m, s m (CaC03)

c to m, s m (CaC03)

c, s m (CaC03)

f, s m (Ca C03)

m , s c, m (CaC03)f, s m (Ca C03)

n l

n l

7.70n l

n l

n l

eses

es

eseses

si l

si lsi I

sil ( fewclay films)

si lsi l

0-2020-4545-78

Bt kBCk1

10YR4/4lOYR4/4lOYR4/4 to7.5YR4/4

78-110 7.5YR4/4110-130 7.5YR4/4

10YR6/3BCk2 130-150 lOYR4/3

ApBABk

Qadurabad [20.]

sil=silt loam; sl=sandy loam; sicl=silty clayey loam.2 eo=non-effervescent; e=slightly effervescent; es=strongly effervescent; ev=violently effervescent.3 nd=not determined.4 f=few 2 of surface area); c=common (2-20 ); m = many (>20 ); s=fine mm in diameter); m=medium

(5-15 mm); 1=large (>15mm). ote Only those soils sampled for laboratory analyses are shown. From Pendall an d Amundson (1990a).


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Pedology and ate uaternary nvironments Surrounding arappa

Table 3.3: The Relative an d Estimated Absolute Ages of the Mapping Units.Differentiating Features

RelativeLandform Agel1 Youngest

Ma p UnitsRecentChannel

Carbonate ObservableMorphology 2 B Horizon Landscape Stage Type Posi tionNone None Entrenched

DistributaryChannel

Estimated Age Years BP

2

3

4

5 Oldest

SubrecentChannelSultanpur,Sultanpur gc

Gamber,LyallpurQadirabad

None

I to Early II

Late II toEarly III

None

Bk,Bw

Bk, Bw, By

Bk, Bt

LevelFloodplainLevelFloodplainLevelFloodplainStreamTerraceRemnant

5000-15,000 5

>708090 6

1 Based on soil morphologic features an d landscape position.2 Based on classification by Gile et al. 1966 an d Sehgal an d Stoops 1972 .

3 Last flood of Recent Channel M. Saddiq, personal communication, 1988 .4Approximate date of beginningof Harappan occupation Kenoyer 1987 .5 Based on rates of pedogenic carbonate redistribution Gile an d Grossman 1979 .6 Radiocarbon date of carbonate on the ins ide ofa nodule from Btk horizon Pendall an d Amundson 1990b .

Source: Pendall an d Amundson 1990a .

sands of years to form a carbonate nodule, the 4C agecould easily suggest an early Holocene, or even latestPleistocene, ag e for the deposit . The relationship ofth e deposi t now preserved in small portions underand around th e m ou nd ) to th e alluvium comprisingth e more extensive Lower Bari Doab terrace betweenPattoke an d Sahiwal is no t known with certainty, bu t

they could be the same. More fieldwork an d elevationdata are needed to work this relationship out.During Holocene times, th e river Ravi presumably

when i t occupied the abandoned channel north ofHarappa) meandered around Harappa, entrenchingan d subsequently partially backfilling its channel. Atleas t three m ea nd er u ni ts o f differing a ge s c ou ld b eidentified on the basis of topography an d soil development. The exact timing of these events is not knownwith certainty. The presence of significant carbonatenodu l e deve l opm ent i n th e o l des t m eander un itsuggests that it is at least several thousand years old,while the presence of pottery fragments n the alluvium

o f t he youngest unit suggests it postdates Harappaitself Table 3.3 . t appears that subsequent downcutt in g b y th e Ravi when i t occupied the abandonedchannel) ul t imately bypassed th e m e an d er b e nd saround Harappa, creatinga moredirect route along thenorth of present-day Harappa. Thus, th e soil/geomorphology map Figure 3.4 and th e relative ag eestimates Table 3.3 suggest that Harappa was initiallybuilt on a slightly elevated landscape in a meander

bend of what may have been at least a seasonally activeRavi river channel. It is difficult to determine, withoutmore fieldwork, if the main channel of the Ravi flowedby Harappa dur ing Harappan times. t does appear,however, that th e meander bends around Harappawere essentially a b an d on e d a t s om e t im e af te r theHarappan occupation.

It should be noted that the abandoned channel ofth e Ravi ca n still receive flood waters during th esummer monsoon season an d that even the relativelye leva ted landscape around Harappa c an b e co m einundated by these floods. Th us, b y no means isHarappa entirely removed from the influence of th epresent-day river Ravi.

Stable Isotope Studies oPre arappan o il

As discussed in the previous section, at l ea st a portion o f H ar ap pa w as b ui lt o n a latest Pleistocene or

early Holocene alluvial deposit. Thus, th e soil thatformed in this deposit wa s at least several thousandy ea rs o ld p ri or to burial d ur in g h u ma n occupationan d should h av e h ad sufficient time to chemicallyreflect pre-Harappan environmental conditions.

In recent years, a search for soil propert ies that canbe quantitatively correlated with climatic parametersh as b ee n u nd er wa y. O ne of the m o s t p ro m is i nga ve nu es h as been th e work o n the s tab le ca rbon


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Harappa xcavations 1986 199 : Multidisciplinary pproach

13C/12C) an d oxygen 18 16 isotope ratios in soilcarbonate. A brief review of this work, an d its significance to ou r work at Harappa, is given below.

Isotope ratios in a sample are reported relative tothose in an internationally-accepted standard in thenotation:

0 0) 1000 [ R sample + R standard) -1 ]

where R sample equals the isotope ratio in a samplean d R standard equals the isotope ratio in the standard. The standard for carbon is the Peedee belemnite PDB) an d for oxygen i t is standard mean ocean water SMOW).

C a rb o n i s ot op e r a ti o s Le., Ol3C v al ue s) i n soilc ar bo na te a r e d e te r mi ne d by that o f th e soil CO 2 Cerling 1984). Soil CO 2 is derived from two sources: 1) root respirat ion/ decomposit ion of soil oryanicmatter biological) an d 2) atmospheric CO 2 0 3C -7 0). Isotopically, there are two main types of plants: 1) C3 o13C values -27 0) an d 2) C 4 ol3C values

-14 0) Bender 1968; Smith and Epstein 1971). C 4plants a re ma in ly restricted to th e tropical grasseswhile C3 plants make up th e remaining grasses an dnearly all other plants.

If the Ol3C value of decomposing plant material isknown, the Ol3C value of soil carbonate can be used todetermine the proportion of CO 2 derived from biological or atmospheric sources. I t ha s been found that theproportion is related to plant density an d soil respiration rates Amundson et al. 1989; Quade et al. 1989)an d that atmospheric CO 2 only makes a significantcontribution to soil CO 2 i n a rid regions Cerling et al.1989). Thus, soil carbonate can be used to distinguish

between semi-arid and t ruly a r id condit ions if th eOl3C of biologically-produced CO 2 is known.In reg ions where tropical grasses are p resent an d

the climate is at least semi-arid, plant cover is usuallydense enough so that atmospheric CO 2 makes on ly asmall contribution to total soil CO 2 Cerling et al.1989). Therefore, in sites where tropical grasslands orsavannas are known to have existed, the Ol3C of soilcarbonate ca n b e us ed to reflect th e relative proportion of C 3 to C 4 plants at the site. This is important toknow i n t ha t th e ~ C ratio is strongly dependent onclimate, particularly temperature Tieszen et al. 1979).

Th e 0 0 value of soil carbonate is determined by

that of th e soil water Cerling 1984), w hi ch i s u lt imately derived from th e precipitation. While factorscontrolling th e 0180 values o f precipitation are verycomplex Gat 1980), i t has b ee n o bs er ve d t ha t it iscommonly correlated to regional temperature Yurtsever 1975). T hu s, t he 0 180 values of s oi lc ar bo na te c an s er ve a s a guide to th e 0 0 value ofpast precipitation as long as poss ible evaporationeffects are considered an d th e effect of soil tempera-

ture is taken into account see Cerling 1984; Quadeal. 1989 for more detailed discussions).

During th e 1987 excavations of Cemetery Rsevera l excellent exposures o f t he Qadirabad Table 3.2) were made. In some locations, the profwas truncated an d buried by several meters of archological material, while in at least on e other loca

the upper horizons of th e profile were found intburied by a few centimeters of archaeological mrial. Because the soil horizons could be traced eathroughout the ceme tery, a complete profilereadily reconstructed.

Calcium carbonate nodules Le., k nk r wcollected in a depth sequence from their uppermoappearance in the profile 120 cm benea th origiland surface) to a depth of almost 400 cm with theof a soil a ug er ). F r om e ac h soil horizon, o r d epinterval, samples of th e bulk soil, th e exter ior ofnodule, an d the interior of th e nodule, were analyisotopically. In addition, sediments from the pres

Ravi floodplain were also analyzed see PendallAmundson 1990b for more details).The results of the carbon isotope analyses are i

trated in Figure 3.5. The carbonate nodules are formfrom th e dissolution of fine-grained carbonate inalluvium an d its subsequent precipitation in noduforms. Th e data i n Figure 3.5 illustrate that the 0values of th e nodules are dist inct from fine-graicarbonate in th e soil or from tha t of fresh river Ralluvium -3.8 0). Recent work ha s shown that pegenic carbonate d oe s n ot inherit its ol3C values froits parent material, bu t instead isotopically reflects thOl3C values of th e soil CO 2 Amundson e t al. 1

Quade et al. 1989). Thus, th e o13

e va lues o f noducan be used to evaluate environmental conditions thaexisted when th e soil formed. A 14C ag e of the inportion of a nodule of th e soil yielded a 14e ag7,080120 years BP Beta 21520). We believe this toa minimum ag e fo r th e soil since i t takes at lseveral thousand years to develop carbonate noduof the size we encountered Sehgal an d Stoops 19Thus, the soil carbonate of the inner portions ofnodu les p robably reflects main ly early Holoceconditions, al though a pre-Holocene a ge is apossible Pendall and Amundson 1990b).

What climatic conditions do th e o l3e values o

carbonate reflect? Since Harappa is presently onarid edge of the semi-arid belt Singh et al. 1974), onquestion might be, were early Holocene conditiosimilar, or possibly more or less arid, than the pre i.e., does the carbona te con ta in significant perceages of atmospheric CO 2 du e to a low plant densiTo evaluate t hi s, w e must k no w w h at th e Ol3biologically produced CO 2 was a t th e ti menodules f or me d. We measured th e o13e values


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Pedology and Late Quaternary Environments Surrounding Harappa

} Akb

} tkb

1 kb} Ckb 1

} C k b

1 50 .5 0. 513

C 0 VS PDB

-1.5

6 Soilo Outer Noduleo Inner Nodule

Auger Samples

6 .

100

15 0

E 200u

s 250

QQ

300

350

4 0 0-2 .5

Figure 3.5: Carbon isotopic composition of carbonate in inner and outer nodule layers an d disseminated in soil. BAkb and Btkb horizons sampled from profile SC3; Bkb, BCkbl, and BCkb2 horizonssampled from profile NCt. From Pendall and Amundson (l990b).

organic mat te r in the Ab hor izons of the Qadirabadsoil. The values ranged from -2 0 to -22 0 indicatingapproximately a 60 C 3 an d 40 C 4 mix of plantsources. If this organic matter is representative of preHarappan vegetation, then the soil carbonates reflectan atmospheric CO 2 contribution of nearly 30 and asoil respiration rate representative of very arid an dsparsely vegetated sites (Figure 3.6).

Soil organic is very dynamic, an d the present ol3Cv a lu es m ay reflect vegeta t ion al tered b y h um a nac tivity a nd m ay n ot be representative of preHarappan c on di ti on s. T hu s a n a lter na tiv eexplanation, as discussed above, can be made. I f it isassumed that the site wa s always under at least semiarid conditions a nd t ha t it ha d a closed vegetat ivecover, the Ol3C values of the carbonate can be taken asrepresentative of the C 3:C4 plant ratio at the site. Soilcarbonate Ol3C values are about -15 0 greater thanthe p la nt s t ha t p ro du ce C O 2 at a site (Cerl ing et al.1989). Using this relationship, the Ol3C values of thecarbonate illustrated in Figures 3.5 an d 3.6 could beinterpreted as having been formed in a nearly pure C4flora, such as a tropical grassland or savanna.

Unfortunately, with the available data, we can notdistinguish between the two alternatives given above.The limiting factor in the analysis is an inadequateknowledge of the Ol3C of soil organic matter at thetime the carbonate formed. The answer to this may liein the nodules themselves in the form of occ luded

organic matter. Possible future work may be able toisolate this carbon an d solve the dilemma.

The 0 180 values of the carbonate samples are illust ra te d i n Figure 3.7. In contrast to the ol3C values,there is virtually no difference between the isotopiccomposition of the fine-grained carbonate in the bulksoil an d tha t of th e nodules. Th e source of thecarbonate in the alluvium is no t known bu t it ma ycontain significant quantities that were formed in apedogenic environment farther upstream on the Ravi.

The main interest here is whether the 0 180 values ofinnermost nodule samples reflect conditions Significantly different than the present. To evaluate this, the0 18 0 value of present-day precipitation must beknown. Monitor ing stat ions ar e few i n Sou th Asia.Available data suggest that t h e ave rage isotopiccomposition of rainwater in New Delhi is 5.7 0while that of Karachi is -4.1 0 (International AtomicEnergy Agency 1960-1987). At 25C, which is approximately the mean annual temperature of Harappacarbonate forming from these waters should rangebetween 22.8 0 an d 24.4 0 (O Neil et al. 1969). The0180 values of the inner nodules are slightly less thanthat predicted from the present rainfall for Karachia nd N ew Delhi, assuming this temperature. We dono t know if this represents a real difference or if i t isdu e to ou r lack of isotopic data for regional rainfall. I freal th e difference would sugges t slightly coolerconditions than the present or greater rainfall ou t of


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Data generatedby model

l Data from innernodule carbonate

tf:

0.025mmole.m 2. hr 1

o

4 ~ _ ~ - - ~ - . L - ~ _ - - - . L - - - _ - - _ - - _ - - - -

5 .0 4 .0 3 .0 2 .0 1.0 0.0 1 0 2.0 3.0 4. 013 C of Carbonate ( 0 VS. POB

100

. - . . .

Eu

J 200-.Q0

300

24

Figure 3.6: Carbon isotopic compositions of inner nodule carbonate in Qadirabad soil (triangles) compared withvalues calculated by the model of Quade et i (1989). Variables: P = 1 atm, T = 25C, n = 0.4, production Ol3C-21.9 0, atmospher ic 013C = -6.0 0, an d various soil respiration rates. From Pendall an d Amundson (1990b).

100 r r . . .

250

350

..c QQ) 3 00o

l S k b

}SCkb 1

} SCk b 2

6 Soilo Outer Nodule


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Pedology and Late Quaternary nvironments Surrounding arappa

storm fronts that reached Harappa in th e past. Thelatter would certainly seem reasonable based on estimates of early Holocene monsoon intensity for SouthAsia COHMAP Members 1988 . Alternatively, thecarbonates ma y have formed at a higher temperaturethan 25C for example during the warm summermonsoon season . Assuming a soil temperature of30C, carbonate forming from present rainwaterwould range between 21.7 an d 23.3 0 which agreeswell w it h t he m ea su re d v al ue s in Figure 3.7. Westrongly emphasize that a better understanding of theisotopic composition of present rainfall at Harappa isneeded before this issue can be resolved.

Summary

The purpose of this paper was to consolidateprevious climatic an d geologic research pertinent toHarappa in a manner that would provide a frameworkfor ou r recent pedological studies, as well as provideabe tter means of understanding the env ironmen tal

context of Harappa. We think that it would be fair toconclude that a very intriguing, bu t sketchy, picture ofthe environmental an d geological history of Harappaemerges from this exercise. The other point thatemerges is that an array of important problems an dtopics remains to be studied an d understood. It shouldbe apparent to interested earth scientists that a wealthof exciting research problems are available for years tocome the environmental context of Harappa, an d theIndus civilization, is to be understood.

knowledgements

The authors thank Ms. Joan Van Horn for preparingthe manuscript. The research was supported, in part,by a grant from t he U ni ve rs it y o f C a li fo rn iaC om mit te e o n Research and f ro m C al if or ni aAgricultural Experiment Station Hatch funds. LaurieNewman an d Joe Jersak reviewed an earlier version ofthe manuscript.

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