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Consequences of sea level and climate changes on themorphodynamics of a tropical coastal lagoon during Holocene:An evolutionary model

D. Padmalal a, K.P.N. Kumaran b,*, K.M. Nair a, Ruta B. Limaye b, S. Vishnu Mohan a,B. Baijulal a, S. Anooja a

aCentre for Earth Science Studies, Thiruvananthapuram 695031, Kerala, Indiab Palynology and Palaeoclimate Laboratory, Palaeobiology Group, Agharkar Research Institute, G.G. Agarkar Road, Pune 411004, Maharashtra, India

a r t i c l e i n f o

Article history:Available online xxx

* Corresponding author.E-mail address: [email protected] (K.P.N. K

1040-6182/$ e see front matter � 2013 Elsevier Ltd ahttp://dx.doi.org/10.1016/j.quaint.2013.12.018

Please cite this article in press as: Padmalacoastal lagoon during Holocene: An evolutio

a b s t r a c t

Vembanad Lagoon is the largest backwater system in the southwestern coast of India, and it is one of thewetlands of international importance, as defined by the Ramsar Convention. The coastal area encom-passing the Vembanad Lagoon comprises a spectrum of barrier islands, ridges and swales, lagoons, andflood plains. The lagoon and its adjoining coastal lands are known for economically viable deposits ofilmenite rich beach placers, lime shells, and high purity silica sands. The sedimentological, palynological,and geochronological studies reveal that the sea level and climate changes have brought significantmodifications in the geomorphic settings of the system. The depositional regimes and the evolutionaryphases showed marked differences in the northern and southern reaches of the Lagoon. The geomor-phological settings, occurrence of a suite of major heavy minerals (sillimanite þ opaque) and predom-inance of marine elements in the palynological assemblage in the southern reach of the lagoon areindicative of barrier spit development, which is further influenced by reworked Neogene sediments withcharacteristic sillimaniteeopaque heavy mineral suite of khondalitic affinity. The northern half evolvedduring the transgressiveeregressive events of EarlyeMiddle Holocene from a sheltered coastal waterbody surrounded by thick coastal vegetation. The opaqueeinosilicate dominant heavy mineral suite inthe northern sector indicates contribution of sediments from charnokitic source rocks in the area northof the Achankovil Shear Zone. The proposed four stage evolutionary model of the Vembanad Lagoonindicates that it evolved from an embayment of the Arabian Sea by the progradation and development ofa barrier spit during transgressiveeregressive cycles under heavy rainfall events of the Holocene.

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1. Introduction

The Indian coastline, stretching over 6500 km, is the sixthlongest in the world and has been subjected to several episodes ofsea level variations that followed the Last Glacial Maximum (LGM).Since the LGM, it has been undergoing physical changes, and thepresent coastal geomorphology has evolved largely in the back-ground of the post-glacial transgression over the pre-existingtopography of the shore, coast and offshore zones (Merh, 1992;Hashimi et al., 1995; Banerjee, 2000; Somayajulu, 2002; Nairet al., 2006). The Holocene sea fluctuated in the course of the last10,000 years, and its oscillations between 3000 and 6000 BP haveleft significant imprints in the sedimentary archives, throwing light

umaran).

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l, D., et al., Consequences ofnary model, Quaternary Inte

on the evolution of the coast. The sea level and climate changeshave strongly influenced the coastal marine processes. Much of thecoastal land and associated landforms around the world have beencarved out during the Late Quaternary and the geomorphic evo-lution has greatly influenced the history of humanity (Woodroffe,2002).

Coastal lagoons are considered to be an important ecosystem inmany low-lying coastlines of continents and constitute 13% of theglobal coastal environment (Bird, 1994; Kjerfve, 1994). Coastal la-goons are highly productive ecosystems, as they contribute to theoverall productivity of coastal waters by supporting a variety ofhabitats, including salt marshes, sea grasses, and mangroves.Several attempts and reviews on this unique ecosystem have addedconsiderable knowledge while appraising their physical andecological dimensions (Roy, 1984, 1994; Carter et al., 1989; Chenget al., 1993; Oliveira and Kjerfve, 1993; Cooper, 1994; Kjerfve,1994; Isla, 1995, 2002; Bird, 2000; Caldara et al., 2002; Davis,

sea level and climate changes on the morphodynamics of a tropicalrnational (2013), http://dx.doi.org/10.1016/j.quaint.2013.12.018

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Fig. 1. Location of the study area and geology of the hinterlands and adjoining regions. Note the khondalitic suite of rocks occurs south of the Achankovil lineament.Source: Soman (2002)

D. Padmalal et al. / Quaternary International xxx (2013) 1e172

2002; Vaz et al., 2002; Suzuki et al., 2002; Serandrei-Barbero et al.,2006; Stutz et al., 2006; Wolanski, 2006; Fontolan et al., 2007;Madricardo et al., 2007; Lloret et al., 2008; Avramidis and Konto-poulos, 2009; Amos et al., 2010; Plecha et al., 2011; Kumaran et al.,2012). Further, lagoons provide a range of natural services thatsociety values considerably (Gönenc and Wolflin, 2005).

The highly developed and evolved coast of southwest India ischaracterized by numerous coastal lagoons of varying size, formingone of the largest wetland systems of its kind. Nearly half of thepopulation of Kerala State depends directly or indirectly on thiswetland or its drainage basins. The wetland system associated withVembanad and its drainage basins covers an area of about16,200 km2, which is 40% of the area of Kerala. Considering thesocio-economic potentials and environmental sensitivity of thiswetland system, the Vembanad Lagoon was included in the list of

Please cite this article in press as: Padmalal, D., et al., Consequences ofcoastal lagoon during Holocene: An evolutionary model, Quaternary Inte

wetlands of international importance, as defined by the RamsarConvention for the conservation and sustainable utilization ofwetlands (Anonymous, 2011). The environmental conditions of thelagoon are in a steady decline due to severe anthropogenicpressures.

The Vembanad Lagoon has undergone considerable geomor-phological and geological changes ever since it formed in responseto sea level oscillations and climatic changes. Most of the coastallandforms have been developed or substantially modified as aresult of the Holocene climatic and sea level changes. Althoughmany studies exist on ecological (Kurien, 1971; Kurien et al., 1975;Kurup, 1982; Menon et al., 2000) hydrographical (Lakshmananet al., 1982; Sankaranarayanan et al., 1986), sedimentological as-pects (Mallik and Suchindan, 1984; Seralathan and Padmalal, 1995)and the landform characteristics (Chattopadhyay, 2002; Nair and


Fig. 2. Landform features of the study area. SKSB (see inset) South Kerala Sedimentary Basin.

D. Padmalal et al. / Quaternary International xxx (2013) 1e17 3

Kumaran, 2006; Narayana and Priju, 2006; Nair, 2007), practicallyno systematic effort has been made to address the morphody-namics and evolutionary aspects of the Vembanad Lagoonwith thehelp of palaeoclimate archives, geochronology and geochemicalsignatures. Therefore, a study has been undertaken to examine theLate Quaternary evolutionary events and coastal processesresponsible for the development of this important partially closedbasin in the southwestern coast of India.

2. Study area

The coastal area hosting the Vembanad wetland system com-prises Cenozoic sediments, especially in the South Kerala Sedi-mentary Basin (SKSB) (Nair et al., 2006; Padmalal et al., 2011). Thiswidest expanse of the SKSB reveals a spectrum of unique landformfeatures that include barrier islands, beach ridges and swales, tidalflats, lagoons, and flood plains. This stretch of the coast containsworkable deposits of many economically important deposits,including heavy mineral placers (ilmenite, sillimanite, zircon,monazite etc), silica sands, and lime shells (Thampi, 1997). The


width of the coastal plains is variable and attains a maximum ofw30 km along 7�400 N, near Cherthala. The expansive lagoons andother backwater bodies receive fresh water from many small rivershaving their origin in theWestern Ghatmountain chain. Among thelagoons, the Vembanad Lagoon extending from Alappuzha in thesouth to Munambam in the north covers an area of over 230 km2.This water body is a part of Vembanad e Kol wetland system. Thelagoon has been heavily reclaimed over the course of the pastcentury with the area reduced to a considerable extent.

The coastal plain topography of the Vembanad Lagoon chosenfor the present study has extremely low relief and is interrupted atcertain places by coastal dunes (Fig. 1). The width of the lagoonvaries from a few hundred meters to about 4.5 km (Maya et al.,2007). The study area and its hinterlands comprise four majorrock units e i) Precambrian crystalline basement rocks, charnock-ites and granite gneisses; ii) Neogene sedimentary rocks; iii) lat-erites; and iv) Quaternary sediments (GSI, 1995). Sedimentaryformations of the coast unconformably overlie the Precambriancrystalline basement. The maximum thickness of the sedimentaryformation is about 700 m. Quaternary sediments record a


Fig. 3. Sediment types (after Picard (1971)) of the borehole cores retrieved from the study area. a e Kalarkod, b e Alappuzha, c eMuhamma, d e Panavally, e � Thannirmukkom, f ePalluruthy, g e Ernakulam, h e Pattanam.


maximum thickness of about 80 m, and the remainder is the Vai-kom, Quilon and Warkalli formations of Neogene. The hinterlandsare composed of Archean crystallines which are traversed by theAchankovil lineament. The area south of the Achankovil lineamentis composed essentially of a khondalitic (garnetesillimanite gneisswith graphite) suite of rocks, and the area north of it is composedmainly of a charnockite suite. Fig. 2 shows the major landformfeatures in the coastal lands of the Vembanad Lagoon.

3. Material and methods

Systematic fieldworkwas carried out in the coastal areas aroundVembanad Lagoon for collection of primary and secondary data onlandform features and other relevant details of the lagoon. A total ofeight borehole cores with lengths of 14e42 m were collected fromthe study area by rotary drilling. The uncontaminated sedimentsamples obtained from modified SPT (Standard Penetration Test)core bits whose inner wall was lined with Teflon were sectioned at10 cm intervals, and subsamples representing each lithounit weresubjected to sedimentological and palynological analyses andgeochronology following standard procedures. The method sug-gested by Lewis (1984) was followed for textural studies of sedi-ment samples. The ternary diagram of Picard (1971) was used forthe classification of sediments. The sand fractionwas sieved at 0.5 Øintervals for investigations on granulometric attributes. The finesand fraction of the sand dominated sediments was separated intoheavy and light minerals using Bromoform techniques and theheavymineral species were identified followingMange andMaurer(1992). The organic carbon and CaCO3 contents were determinedusing the procedures of El Wakeel and Riley (1957) and Jackson(1967), respectively. The samples for recovering palynomorphs


were processed by conventional methods by separating organicwalledmicrofossils from sediments (Traverse, 2007). Pollen, spores,dinoflagellates, non pollen palynomorphs (NPP) and diatoms wereidentified using the available database and published records(Thanikaimoni et al., 1984; Williams and Bujak, 1985;Thanikaimoni, 1987; Nayar, 1990; Tissot et al., 1994; Singh andSharma, 1996; Kumaran, 2001; Limaye, 2004; Limaye et al.,2007). Quantitative analysis and spectra of palynological assem-blages were prepared by using Sigmaplot softwares. Radiocarbon(14C) dates of organic rich sediments at specific levels were deter-mined at Birbal Sahni Institute of Palaeobotany, Lucknow (India).

4. Observations and results

4.1. Sediment architecture

Fig. 3 shows the sediment types of the borehole core sampleschosen for the present study. The samples fall mainly within sand,silty clay, sandy clay, clayey sand, and clayey silt categories. Thedistribution pattern of the ternary plots deviates markedly in thePalluruthy core. Fig. 4 shows locations of the lithologs of variousborehole cores retrieved from the coastal lands of the VembanadLagoon. The co-ordinates and depth of the borehole cores are givenin Table 1. Table 2 gives a brief account of the lithological charac-teristics, palynological/micropalaeontological observations anddepositional environment of the borehole cores. The contents oforganic carbon (C-org) and carbonate carbon (as CaCO3), and heavymineral suites in the sediments are summarised in Tables 3and 4,respectively. Table 5 shows the radiocarbon dates of the sedimentsamples at selected depths of the borehole core. The subsurfacesedimentary architecture showing the dominant sedimentary


Fig. 4. Lithologs of borehole cores retrieved from selected sites in the coastal plains of Vembanad Lagoon along with the Radiocarbon dates at selected intervals.


Please cite this article in press as: Padmalal, D., et al., Consequences of sea level and climate changes on the morphodynamics of a tropicalcoastal lagoon during Holocene: An evolutionary model, Quaternary International (2013), http://dx.doi.org/10.1016/j.quaint.2013.12.018


facies is reconstructed from the observations and results of thepresent study of borehole cores (Fig. 5). The thickness of sedimentsattains its maximum in the southern sector and almost coincideswith the deepest part (Central Depression) of the South KeralaSedimentary Basin (Nair and Rao, 1980; Nair et al., 2006), the on-land extension of the KeralaeKonkan basin. The southern sector(south of Palluruthy) contains Late Pleistocene and Holocene sed-iments, whereas the northern sector is practically devoid of LatePleistocene sediments. The oldest age (20,380 BP) is noted for theKalarkod site at 40m bgl and the youngest is recorded at Palluruthy(3220 BP) at a depth of 6.45 m bgl. As seen from Fig. 5 and Table 5,the Late Quaternary coastal sedimentary environment of the studyarea comprises three distinct sedimentary facies. They are i) Ho-locene sand facies; ii) Holocenemud facies; and iii) Late Pleistocenemud resting over the lateritised Neogene sediments. A briefdescription of the different lithofacies is given below:

Table 1Location of the borehole cores collected from the coastal plains of VembanadLagoon.

Sl. No. Borehole location Latitude Longitude Borehole depth (m)

1 Kalarkod 9�2705500N 76�210E 402 Alappuzha 9�2903000N 76�2005100E 343 Muhamma 9�3601500N 76�2105000E 324 Thannirmukkom 9�4004200N 76�2205700E 145 Panavally 9�4704500N 76�2102800E 426 Palluruthy 9�5401500N 76�1603000E 307 Ernakulam 9�5801600N 76�1701700E 248 Pattanam 10�0900200N 76�1205200E 34

Table 2Details of the borehole cores and depth, lithological characteristics, palynological cexaminations.

Depth (m) Lithological characteristics Palynolo

I) Kalarkod borehole0e25.5 Sand dominant layer intervened at 7e11 m level by 3.6 m thick

silty clay with occasional presence of molluscan shells. Sandsare medium to fine grained and poorly sorted.

High recforaminalgae isplants oforest pflood pl

25.5e42 Greenish grey, carbonaceous clay often with broken andunbroken shells of juvenile forms of pelecypods and gastropods.

Organicpollen oof the liforaminaureumoccurrelittoral b

II) Alappuzha borehole0e23 The borehole core is made up essentially of silt and clay

dominated; organic rich sediments intervened at 0e1.0 m bglbymedium to fine grained sand. The silt and clay rich sedimentsat the top of the borehole core contain broken and unbrokenshells of pelecypods and gastropods.

Good reof BoliviplanktoVeryhacCullenia

III) Muhamma borehole core0e19 Medium to fine grained sand intervened at 3.5e5.5 m level by

silt and clay rich sediments and 12.5e13.0 m level by clayeysands. The entire sequence contains broken and unbroken shellsof pelecypods and gastropods.

Foraminremainscyanoba

19e32 Greyish green silt and clay dominated sediments withoccasional presence of broken and unbroken shells.

Dominastructurand pol

IV) Thannirmukkom borehole core0e12 Light grey; coarse to fine grained sand often with shell dust at

certain levels.Dominastructurdinoflag

12e14 Greyish green silt and clay dominated sediment with fairly highcontent of organic carbon. The sediments are with occasionalpresence of shell dusts.

AbundaCyanoba


4.1.1. Holocene sand faciesStatistical analysis of the upper sand facies (Lewis, 1984)

revealed that the sands are poorly sorted, coarse skewed, me-dium to fine grained quartzose sand whose thickness variesconsiderably along and across the costal lands of the study area.The sand exhibits a few lenticular patches of mud dominatedsediments of varying dimension; the largest one is noticedaround Alappuzha borehole site. Age of the lenticular mud de-posit at Alappuzha varies from 6780 � 160 to 3990 � 150 BP,indicating that the sand in the study area is Middle to Late Ho-locene. The lower part of the mud dominated lenticular body inthe Alappuzha borehole site shows deposition of older reworkedsediments over younger sediments during transgression, afeature also reported from the Kachchh coast by Nigam andChaturvedi (2006). The sand facies shows maximum develop-ment in the region around the ThannirmukkomePanavallyborehole sites. In these areas, the upper part of the sand ismodified into dune complexes whose height reaches 6.0 m abovemean sea level (msl). Whereas the upper part of the sand issugary white in appearance, the lower part is light grey andcontains lamellibranch shells and shell dusts. The sand faciesreaches its minimum thickness near the PalluruthyeErnakulamarea. The sand at 2.0e4.0 m level of the Pattanam borehole corecontains a few archaeologically significant materials: colouredbeads and pottery, brick pieces, and pebbles. The sand in thebottom half of the core shows the presence of shells of Donax,Fusinus, Turbo, Cerithium, Dentalium, Venus, and Meretrix, indi-cating a littoral/near-shore environment of deposition.

ontents, depositional environments inferred from lithological and palynological

gical observations Depositionalenvironment

overy of organic remains -, dinoflagellates andiferal linings; abundance of diatoms; littoral blue-greenrepresented by Rivularia spp., pollen of fresh waterf Liliaceae/Potamogetonaceae are recorded; Beachlant pollen of Pandanus are abundant; Spores of theain ferns and fungi are also common.

Littoral/near shoremarine.

remains abundant e occurrence of inland montanef Cullennia exarillata recorded at certain levels in the topthounit. Marine phytoplankton is represented by a fewiferal linings; spores of the mangrove fern Acrostichumare plenty; bottom part of this lithounit showsnce of the dinoflagellate speciesMultispinula quanta andlue-green alga Rivularia.

Littoral lagoonal withfluctuating salinityconditions

covery of organic matter e juvenile foraminiferal testsna and Pararotalina are common; common microns are represented by Polysphaeridium andhium; a few marine diatoms are also seen; pollen ofpresent; Fresh water alga Botryococcus also seen.

Marine to brackishwater.

iferal linings; dominance of structural terrestrial; fungal complex; dinoflagellates; thecamoeba andcteria.

Marine environmentwith terrestrial inputs.

ted by diatoms and sponge spicules along withal terrestrial remains; fungal complex; Bacteriastrumlen.


ted by juvenile foram tests and foraminiferal linings;al terrestrial remains, pollen; sponge spicules,ellate, and fungal complex.

Littoral e marineenvironment.

nce of fungal complex indicating high humid climate;cteria, thecamoeba and dinoflagellates.



Table 2 (continued )

Depth (m) Lithological characteristics Palynological observations Depositionalenvironment

V) Panavally borehole core0e13 Light grey, coarse to fine grained quartzose sand. The top

3.0e5.0 m zone has a coffee brown colouration. The bottom halfof this layer is with shell dusts.

Foram tests and linings are abundant; pteridophytic spores arecommon; presence of Rivularia and dinoflagellates; palm pollenand a few diatoms.

Littoral-marineenvironment.

13e25 Greyish green, silt dominated sequence with clay dominatedinterlayer at 19e20 m level. Shell dusts and broken juvenileshells are occasionally seen.

Foram tests and foraminiferal linings are abundant;Botryococcus; diatoms; dinoflagellates, pteridophytic spores;fungal spores.

Marine environmentswith terrestrial inputsand salinity changes.

25e42 Greyish green, clay dominated sediments with small pockets ofshells and coarse quartzose sand.

Foram tests and linings are common; scales of invertebratesnoticed at certain levels; pteridophytic spores a few; palmpollen at certain depths; diatoms, charcoal and few blue-greenalga (Rivularia) present, sponge spicules, dinoflagellates cyst,etc.

Marine environmentswith terrestrialcontributions.

VI) Palluruthy borehole core0e19 Generally silt and clay dominated, greyish sediments

intercalated at 0e2.0 m and 7.0e9.0 m level by sand dominatedlayer. The silt and clay dominated layer is often with broken andunbroken shells of marine origin.

Foraminiferal linings abundant; pollen; fungal complex;diatoms; structural terrestrial remains; sponge spicule;dinoflagellates and cyanobacteria; microscopic charcoal foundat the upper half of the section.

Marine environment.

19e24 Light grey, medium to fine grained sand broken and unbrokenshells.

Dominance of structural terrestrial remains; microscopiccharcoal; mineral crystal; presence of pollen; fungal complex;Bacteriastrum; foraminiferal linings; dinoflagellates andcyanobacteria.

Brackish water lagoonalenvironment.

24e29 Greyish green, silty clay with pockets of sands and shells. Dominance of structural terrestrial remains; microscopiccharcoal; pollen; fungal complex; diatoms; foraminiferallinings; dinoflagellate; sponge spicules; cyanobacteria andBacteriastrum.

Brackish water lagoonalenvironment.

29e30 Reddish brown, sandy clay (laterised). No recovery of spores and pollen. Sub aerial weatheringand oxidation undertropical climate.

VII) Ernakulam borehole core0e7.5 A composite sequence of sand and silt/ clay alternation. Sand in

this sequence is medium to fine grained andwith low content ofheavy minerals. The layer is greyish green and with broken andunbroken shells.

Very good recovery of organic matter rich palynodebris; marinephytoplankton dominate; pteridophytic and fungal spores arecommon; Cocos pollen seen, mangrove pollen (Rhizophoraceae)and salt glands; Cullenia and Euphorbiaceae (evergreen) pollenat certain level; palynodebris becomes poor at the basal part ofthis section.

Marine to brackishwater environmentwith terrestrial inputs.

7.5e21.5 Greyish green, silt and clay dominated layer with marine/lagoonal shells and shell dusts. The bottom part of the sectionwith spheroids of organic materials indicative of biogenicactivity on the sediments.

Very good organic recovery e marine phytoplanktons(Spiniferites and Polysphaeridium) dominates; mangrove pollen(Rhizophoraceae); salt glands; Cullenia and Euphorbiaceae;reworked Warkalli sediments indicated by Ctenolophoniditespollen.


21.5e23 Greyish white sand dominant layer with reddish brown andyellowish brown patches (laterised).

Organic recovery poor. Continental fresh waterenvironment,sediments indicate postdepositional oxidation.

VIII) Pattanam borehole core0e11 Medium to fine grained sand dominated sediments with

occasional presence of pottery pieces, shards etc., at the top andbroken and unbroken marine shells in the bottom half.

Dominance of structural terrestrial remains; microscopiccharcoal; pollen; fungal complex; spores; diatoms;foraminiferal linings, dinoflagellates, Veryhachium, spongespicules, Bacteriastrum and cyanobacteria; salt gland(Heliospermopsis type) and Glomus spores at 550e750 m bgl.

Marine - littoralenvironment withterrestrial inputs anderosional activities.

11e32 Greyish green-greyish black, silt and clay dominated sedimentswith shells and gastropods. The layer is intervened at 15e17.5 m level by medium grained sand. The clay dominatedsediments at 17.5e32 m level is rich in organic matter.

Dominance of structural terrestrial remains and microscopiccharcoal; pollen, fungal complex, leaf cuticles, spores,dinoflagellates, sponge spicules, insect parts and cyanobacteriaare common; foraminiferal linings at certain levels.


32e34 Light grey, medium to fine grained sand. Structural terrestrial remains and microscopic charcoal. Fresh waterenvironment.

Table 3Organic and inorganic carbon contents.

Borehole core Organic carbon (%) CaCO3 (%)

1 2 3 4 1 2 3 4

Kalarkod 0.96 e 2.66 2.84 5.28 e 6.22 8.32Alappuzha 1.62 e 0.53 2.40 3.93 e 1.00 3.83Muhamma 0.74 e 3.75 2.77 5.28 e 9.25 8.63Thannirmukkom 0.15 2.13 2.31 2.44 0.60 3.15 2.00 2.50Panavally 0.06 2.05 e 2.25 0.62 2.73 e 2.20Palluruthy 0.24 2.65 2.78 3.35 2.50 3.75 4.08 2.75Ernakulam 0.20 1.48 2.51 3.44 0.75 10.80 12.25 5.63Pattanam 0.25 e 1.45 4.67 0.65 e 3.43 1.09

1. Sand dominated sediment 2. Silt dominated sediment 3. Mud dominated sedi-ment 4. Clay dominated sediment.



4.1.2. Holocene mud faciesThe Holocene sand facies is underlined by a greyish black to

greyish green mud dominated facies containing occasional pres-ence of brackish to marine water molluscan shells. The radiocarbondates of this mud dominated facies vary between 9700 � 130 BPand 3220 � 90 BP. The Holocene mud deposit encases manylenticular patches of sand bodies of variable dimensions, especiallyin the northern part of the study area, which is influenced mainlyby the Periyar River and its distributaries. In the southern half of thestudy area near Panavally, the mud dominated deposit is divisibleinto a silt-dominated upper layer and a clay-dominated lower layerwith occasional shell and/or coarse sand pockets. The dominanttype of shells noticed in the Holocene mud facies includes


Table

4Hea

vymineral

contents

inthefinefraction

ofsanddom

inan

tsedim

ents

ofthestudyarea

.

Boreh

ole

THM

(Wt%)

MF(W

t%)

Non

-MF(W

t%)

Non

-MFin

numbe

r%

Ilmen

ite

Silliman

ite

Zircon

Mon

aziteIonosilicates

Garnet

Others

BH.N

o.1(K

alarko

d)

0.69

e12

.33(3.25)

0.35

e0.98

(0.55)

99.02e

99.65(99.29

)9.14

e64

.44(43.10

)25

.27e

54.60(40.47

)0e

3.01

(1.36)

Trace

ee

e

BH.N

o.2(A

lappuzh

a)3.08

e13

.45(8.73)

0.72

e2.15

(1.24)

99.28e

97.85(98.76

)25

e62

.69(50.70

)26

.04e

61.67(38.80

)1.04

e2.94

(1.92)

Trace

Trace

eTrace

BH.N

o.3(M

uham

ma)

0.77

e3.36

(1.73)

0.62

e1.12

(0.89)

98.88e

99.36(99.12

)8.87

e42

.86(28.52

)47

.06e

77.42(61.29

)2.33

e5.65

(3.75)

eTrace

Trace

Trace

BH.N

o.4(Than

nirmukk

om)

0.16

e1.41

(0.58)

0.74

e1.25

(1.01)

98.75e

99.26(99.00

)4.50

e20

.54(11.24

)40

e86

.96(66.21

)1.24

e5.41

(2.86)

Trace

1.86

e27

.33(8.49)

Trace

0e3.41

(1.41)

BH.N

o.5(Pan

avally)

1.23

e5.58

(3.35)

0.48

e1.59

(0.86)

98.41e

99.52(99.14

)17

.04e

41.38(29.81

)55

e74

.07(63.25

)0.92

e4.64

(2.73)

ee

Traces

Traces

BH.N

o.6(Palluruthy)

0.77

e2.46

(1.47)

2.31

e4.10

(2.72)

95.90e

97.69(96.70

)30

.10e

36.25(32.65

)7.20

e10

.50(9.21)

Traces

e33

.25e

40.27(37.88

)e

Trace

BH.N

o.7(Ern

akulam)

0.33

e7.13

(2.99)

12.23e

19.18(15.82

)80

.82e

87.27(84.10

)4.55

e16

.25(7.82)

2.94

e6.25

(4.67)

1.47

e3.82

(2.60)

Trace

63.75e

82.35(74.45

)1.14

e6.87

(3.68)

1.25

e5.34

(3.24)

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gastropods Cerithium, Turritella, Turbo and Nassarius and pelecy-pods Cardita and Venus. The sediments generally show a coarseningupward sequence, indicating a progressively increasing hydrody-namic regime prevailed during the deposition of sediments. Theborehole cores of Palluruthy and Ernakulam areas are composedgenerally of mud dominated facies, and the sand apron in theseareas is comparatively thinner. The Holocene mud facies rests un-conformably over reddish brown lateritised sandy clay of Neogeneage. Well preserved shells of gastropods (Dentalium, Turritella,Turbo and Nerita) and pelecypods (Paphia, Cardita, Arca, Mesodesmaand Donax) are abundant at certain levels of the Holocene mudfacies. The lower part of the deposit, especially in the Ernakulamborehole core, contains organic-rich pellets that appear to haveformed by the activity of burrowing animals such as crabs in theintertidal zones.

4.1.3. Late Pleistocene mud faciesThe Late Pleistocene mud dominated sediments are similar to

the Holocenemud facies. However, the former can be distinguishedfrom the latter by their high degree of compaction. The LatePleistocene mud dominated sediments rest unconformably overNeogene sediments or Archean crystallines. This lithounit isconfined to the Central Depression (CD) of the South Kerala Sedi-mentary Basin (SKSB) described earlier by Nair et al. (2006). Asediment sample collected from the Kalarkod borehole at a depth of40 m below ground level dated 20380 � 490 BP. The lithounits ofthe Panavally borehole core at 40.8 m bgl and Palluruthy boreholecore at 20.55 m bgl are younger, dated 11010 � 170 BP and10620 � 160 BP respectively.

4.2. Organic carbon and CaCO3

Organic carbon (C-org) and CaCO3 are integral components ofmany coastal sediments of ancient and recent origin. C-org andCaCO3 reach the coastal sediments from autochthonous andallochthonous sources. The relative proportion of their supply is afunction of the characteristics of the catchment in relation to theproductivity of the depositional environment. The C-org and CaCO3contents in the borehole core sediments are given in Table 3. Fig. 6aand b depict the downcore variations of these parameters alongwith the contents of sand, silt and clay in the borehole sediments.The content of C-org and CaCO3 exhibits marked temporal andspatial variations. Among the various sediment types, the sand-dominant sediments in all the borehole cores exhibit substan-tially low contents of C-org compared to the silt and clay dominatedsediments. CaCO3 does not exhibit any such textural dependency,because it reaches sediments through biogenic pathway, especiallycontribution from shell-bearing animals inhabiting the lagoon andnearby areas. Although the content of C-org is generally low in theHolocene sand facies as compared to the mud dominated Holoceneand Late Pleistocene mud dominated sediments, its spatial distri-bution shows a distinct trend. The sand unit of the boreholes fromthe southern end (Kalarkod, Alappuzha and Muhamma) showmarginally higher C-org values than the rest of the regions. This highcontent of C-org in the sand fraction of the Kalarkod (0.96%), Alap-puzha (1.62%) and Muhamma (0.74%) borehole cores might beattributed to the rapid deposition of sand and organic matter-richparticulates in a sheltered environment. The silt, mud, and claydominated sediments display higher enrichment of C-org than sanddominated sediments. Among the clay dominated sediments, theborehole cores from north of Palluruthy exhibit substantially highcontents of C-org compared to the southern counter parts. Thismight be due to the contribution of C-org frommangrove vegetationthat might have flourished in the area during Early-Middle Holo-cene (Kumaran et al., 2013). The CaCO3 content also exhibits


Table 5Radiocarbon dates of selected intervals of boreholes cores retrieved from coastal plains of Vembanad Lagoon

Sl. No Lab No./References Location Depth (m) Material 14C age (yr BP) Calibrated age (cal. BP)one sigma level

1 Nair et al., 2006 Kalarkode 8.45 Sediment 6740 � 120 76102 Nair et al., 2006 Kalarkode 40.00 Sediment 20380 � 490 243103 BS 2392 Alappuzha 2.35 Sediment 3990 � 150 44704 BS 2437 Alappuzha 5.25 Sediment 4840 � 170 55705 BS 2439 Alappuzha 8.25 Sediment 5670 � 140 64906 BS 2440 Alappuzha 10.95 Sediment 6780 � 160 76607 BS 2438 Alappuzha 12.95 Sediment 6630 � 230 75108 BS 2708 Muhamma 3.95 Sediment 6800 � 180 76509 BS 2713 Muhamma 21.45 Sediment 8320 � 110 930010 BS 2714 Muhamma 25.45 Sediment 9700 � 130 1117011 BS 2712 Muhamma 29.45 Sediment 9380 � 110 1067012 BS 2468 Thannirmukkom 13.50 Sediment 8470 � 240 948013 BS 2588 Panavally 15.40 Sediment 5810 � 100 664014 BS 2589 Panavally 31.20 Sediment 9680 � 170 1095015 BS 2591 Panavally 40.80 Sediment 11010 � 170 1300016 BS 2700 Palluruthy 6.45 Sediment 3220 � 90 370017 BS 2702 Palluruthy 14.90 Sediment 6530 � 160 743018 BS 2701 Palluruthy 20.55 Sediment 10620 � 160 1263019 BS 2347 Ernakulam 3.85 Sediment 5680 � 170 650020 BS 2451 Ernakulam 10.05 Sediment 5870 � 160 671021 BS 2467 Ernakulam 13.95 Sediment 5700 � 180 653022 BS 2378 Ernakulam 15.75 Sediment 6530 � 130 743023 BS 2449 Ernakulam 17.95 Sediment 8940 � 150 1000024 BS 2445 Ernakulam 19.45 Sediment 9170 � 200 1034025 BS 2346 Ernakulam 20.25 Sediment 9250 � 170 1048026 BS 2782 Pattanam 10.00 Sediment 5390 � 140 620027 BS 2784 Pattanam 20.00 Sediment 9030 � 100 1021028 BS 2780 Pattanam 27.50 Sediment 9540 � 110 10860

Fig. 5. Late Quaternary sedimentary framework in a coastal section extending from Kalarkod to Pattanam. Note the one-digit corrected radiocarbon dates at different levels.



Fig. 6. a. Downcore variations of organic carbon (C-org) and CaCO3 along with the variations of Sand, Silt and Clay for borehole Kalarkod, Alappuzha, Muhamma and Thannir-mukkom. b. Downcore variations of organic carbon (C-org) and CaCO3 along with the variations of Sand, Silt and Clay for borehole Panavally, Palluruthi, Eranakulam and Pattanam.




manifold enrichment in the sand-dominated sediments, because ofabundance of shell dusts and broken shell pieces within it. In anearlier study, Maya et al. (2007) revealed that the southern part ofthe Vembanad lagoon, especially around Alappuzha, Muhamma,Kalarkod and Kaniyamkulam, contains economically viable occur-rence of subsurface lime shells with 14C dates of 3000e4500 BP, inbedded or lenticular forms. The Middle to Late Holocene wasfavourable for the prolific development of clams such as Villorita sp,which forms the major constituent in the subfossil shell deposit ofthe Vembanad basin. These shells are the major source of CaCO3 inthe sand layers of the southern borehole cores.

4.3. Palynology, non-pollen palynomorphs (NPP) and diatoms

Recovery of palynodebris is relatively high in all the studiedboreholes, except for the cores of southern part of VembanadLagoon which yielded higher proportions of NPP and diatoms.Considering the sea levels, tidal fluctuations and terrestrial input,both the marine and fresh water palynomorphs have been recog-nized in all the subsurface sediments. Qualitative analysis andrelative abundance of the palynological contents and other mi-crofossils have helped in identifying the ecological shifts anddepositional environment at different levels. Based on the accruedpalynological data, it was possible to distinguish different ecolog-ical complexes and palynological suites including the transitionfacies. The palynological features and their ecological and envi-ronmental preferences are briefly discussed to reveal the marineeterrestrial interactions in the depositional regime of the study area.

In the Kalarkod borehole core, only two intervals between 7 mand 11m and 25.5m and 42m have yielded fairly rich palynologicalassemblages. Many species of diatoms, dinoflagellates and acri-tarchs indicating marine, estuarine and brackish water facies havebeen recovered. The high rainfall indicator pollen of Cullenia exar-illata, spores of the freshwater swampy flood plain fern Ceratopteristhalictroides, and pollen of continental plants including Hibiscustiliaceous are some of the significant palynological contents. Exceptfor the uppermost 1 m and the interval of 13 m and 15.5 m, theAlappuzha borehole core has organic rich sediments throughout.The palynological signatures are represented mainly by micro-plankton of Polysphaeridium, Veryhachium, and diatoms. Pollen ofCullenia exarillata and colonies of fresh water alga Botryococcusindicate high rainfall and changes in hydrological regime in thisprofile. The palynological spectrum of Muhamma suggests that theenvironment has been fluctuating considerably during the Holo-cene. The top 5.50 m contains representations of both terrestrialand marine environments. However, a change in facies to 20.40 mincluding marine deposits has been recognised. Dominance ofstructural terrestrial remains until 32.0 m depth indicatesreplacement of marine facies to freshwater terrestrial environmentwith frequent signatures of marine input as revealed by forami-niferal linings, diatoms and Bacteriastrum. The Thannirmukkomborehole has a sand-dominated sequence, and as such the organicrecovery is much less. However, marine signatures include fora-miniferal linings, sponge spicules, and dinoflagellates, along withabundant structural material and pollen indicating strong inputfrom terrestrial sources. Further, the abundance of fungal complexin the older sediments (12e14m) indicates humid climate and highrainfall.

In the Panavally borehole core, the top sand-dominated unit hadrelatively poor recovery of palynodebris. Of the 42.0 m long core ofPanavally, the top 13.0 m is essentially sand-dominated, andorganic recovery is relatively scarce. Silt and clay-dominated bot-tom sediments (13e42 m) have yielded palynomorphs represent-ing marine, brackish, and terrestrial environments. The upper sandunit yielded juvenile foram tests, foraminiferal linings,


dinoflagellates, and a few diatoms. However, terrestrial input intothe marine facies has been noted in the form of pteridophyticspores, and palm pollen. Three intervals of sand sequences alter-nating with silty mud and stiff clay in the Palluruthy borehole coreshow marine as well as terrestrial signatures. Marine elements offoraminiferal linings and dinoflagellates are significant. Fresh waterinput of cyanobacteria is also an important aspect of the palyno-logical spectrum. Organic matter recovery in the Ernakulam bore-hole is much better, with an abundance of palynodebris. Evidenceof mangrove vegetation represented by pollen of Rhizophoraceaehas been found in the upper sequence (0e7.5 m). Terrestrial inputfrom coastal vegetation (palms) and wet evergreen forests (Culleniaand Euphorbiaceae) are also represented. However, the basal partof the section (21.5e23.0 m) has not yielded any organic matter.Although the middle part of the section (7.5e21.5 m) is dominatedby marine phytoplankton (Spiniferites and Polysphaeridium), thisinterval contains signatures of mangroves and wet evergreen for-ests. The Pattanam sediments essentially show marine to brackishwater environments, although the samples yielded abundantstructural terrestrial remains. Only the lowermost part (32e34 m)ismainly representative of a freshwater environment, as it containsaccumulations of structural terrestrial material and microscopiccharcoal. The occurrence and relative abundance of palynomorphs,organic microfossils, and diatoms at different levels of the boreholecores are shown in Table 2. In order to show the representation ofthe different palynological contents and other microfossils in thestratigraphic sequences, palynological profiles of Ernakulam andPanavally are shown in Figs. 7 and 8 respectively. Selected sporesand pollen grains and other microfossils of ecological significanceare represented in Fig. 9.

4.4. Heavy mineralogy

The fine sand fraction of the sand dominant lithounits of theborehole cores was subjected to heavy mineral studies for unrav-elling the depositional environments as well as the provenance ofthe sediments (Table 4). Based on the heavy mineral diversity ofthe sediments, two major sectors are identified in the area in thecoastal stretch between Kalarkod and Pattanam: i) the coast southof Palluruthy, with low content of heavy minerals with dominanceof the sillimaniteeopaque suite; and ii) the coast north of Pal-luruthy characterised by substantially high contents of total heavyminerals with dominance of opaqueeinosilicate (pyroxene andamphiboles) suites. Weight percentages of the total heavy min-erals (THM) in the borehole cores retrieved from the coastalstretch south of Palluruthy (BHC 6) range from 0.58% to 8.73%. Thecontents of magnetic and non-magnetic fractions in the heavymineral residue are 0.55%e1.24% and 98.76%e99.29% respectively.The non-magnetic fraction has ilmenite and sillimanite as themajor minerals and zircon as a minor mineral. Traces of inosilicate(except in BHC 4), garnet, and monazite are also detected in somesamples (Table 4). In BHC 4, the content of inosilicate is substan-tially high because of the closeness of the borehole site to thecharnockitic hinterlands. The northern half of the Vembanad ba-sin, north of Palluruthy (BHC 6) records substantially high contentsof total heavy minerals (2.99%e11.22%; av. 7.11%). The magneticfraction in the heavy mineral residue is many-fold higher than thatof the southern sector. The weight percentages of magnetic andnon-magnetic fractions in the heavy mineral residue of thenorthern Vembanad Lagoon are 15.82%e27.52% and 72.45%e84.10%, respectively. Inosilicate and ilmenite are the major min-erals in the heavy mineral residue. The minor minerals recorded inthe northern parts of the Vembanad Lagoon include sillimaniteand zircon. Garnet and monazite occur in traces in the heavymineral residue.


Fig. 7. Pollen, spores and NPP spectrum of Ernakulam borehole core (Kerala) India.


5. Discussion

The coast in southwest India is endowed with an interlacingnetwork of backwater bodies (locally known as kayals) anddrainage channels, many of them evolved during the Holocene(Joseph and Thrivikramaji, 2002). The backwater bodies are eitherestuaries or lagoons which are open to the sea seasonally orperennially, separated by spits and bars. These wetlands play a

Fig. 8. Pollen, spores and NPP spectrum of


pivotal role in the socio-economic and environmental scenarios ofthe region and therefore, their conservation is essential for thesustenance of the people in the area. Among thesewater bodies, theVembanad Lagoon is the largest one on the entire southwesterncoast of India. The basin area of the lagoon covers almost 40% thetotal area of the densely populated Kerala State. Previously, therewas no conceptual model or hypothesis to explain how the Vem-banad Lagoon has evolved in the recent past. The few existing

Panavally borehole core (Kerala), India.


Fig. 9. Selected pollen, spores and other microfossils of specific ecological environmental conditions. (All photomicrographs are enlarged ca. 500� except fungal remains, which are,enlarged ca. 1000� unless otherwise specified). 1. Rhizophora sp, pollenmass (Mangrove facies). 2. Sonneratia alba (Mangrove facies). 3. Bruguiera sp. (Mangrove facies). 4. Acrostichumaureum (Mangrove associate). 5. Thespesia sp. (Mangrove associate). 6. Malvaceae pollen (Coastal plant). 7. Euphorbiaceae pollen (Hinterland). 8. Chenopodiaceae pollen (Aridityindicator). 9 & 27. Heliospermopsis sp. (Salt glands of Mangroves) 10 & 11. Ceratopteris thalictroides (Freshwater flood plain indicator). 12. Gleichenia sp (Humid phase). 13 & 14. Culleniaexarillata (Heavy rainfall indicator). 15. Lirasporites sp (Fungal spore). 16. Exesisporites sp. (Fungal spore). 17. Callimothallus sp (Fungal fruiting body). 18. Plochmopeltinites cooksonii(Fungal fruiting body). 19.Kutchiathyrites eccentricus (Fungal fruiting body). 20. Gleotrichia sp (Cyanobacteria). 21. Rivularia sp (Cyanobacteria). 22.Multispinula quanta (Dinoflagellate,marine facies). 23, 24, 26. Spiniferites sp. (Dinoflagellate,marine facies). 25. Thecamoeba sp. (Acidic, pollution and stress conditions). 28, 29. Foraminiferal linings (Marine environment).



conceptual models (Roy, 1984; Kjerfve and Margill, 1989; Ward andAshley, 1989; Nicholls, 1991; Umitsu et al., 2001) deal mainly withinfilling process of vertical changes in morphology and sedimen-tation and the degree of water exchange with the adjacent coastalareas, and as such they can not be applied uniformly. This is becauselagoons exhibit different morphologies and form under a variety ofenvironmental conditions and geomorphologic settings, whichdetermine not only the principal morphodynamic process but alsothe evolutionary path which a lagoon follows. Although 17 note-worthy lagoons exist along the Indian coasts, only the Chilka,Pulicat and Iskapalli lagoons of the east coast have been addressedto some extent in terms of coastal dynamics (Venkatarathnam,1970; Banerjee, 1993; Vaz and Banerjee, 1997; Seetharamaiahet al., 2005; Panda et al., 2013). However, the coastal lagoonsalong west coast of India have not received much attention withrespect to their antiquity and morphodynamics of the recent past.Recently, attempts have been initiated to address the evolution ofthe wetland systems of southwest India in relation to sea level andclimate changes (Padmalal et al., 2011). There has been little inte-gration of physical evolution with biological changes in lagoondevelopment along the west coast of India. Although the process offormation of the Vembanad Lagoon dates to Early Miocene, thepresent geomorphic configuration is the outcome of the interplayof Late Quaternary climatic and sea level changes, especially duringthe later phases of the Last Glacial Maximum (LGM). The subsurfacedata of the boreholes provided sufficient lithological and biologicalinformation to distinguish facies changeswithin a geochronologicalframework while addressing the evolution of the VembanadLagoon.

The marine transgression in the beginning of Holocene has hada profound impact on the antiquity and evolution of the Vembanadlagoon. The presence of a marine embayment and altitude of thelocation almost equal to the ambient sea level facilitated theearliest marine influence during the Early Holocene (9.5e8.0 kaBP). Although sedimentation appears to have kept pace with rise insea level, it did not result in open marine conditions in this waterbody, as the mixing of marine waters and the heavy influx of freshwater brought in by the Achankovil, Pamba, Manimala, Meenachil,Muvattupuzha, Periyar and Chalakudy rivers controlled the ecologyof the lagoon. High rainfall from 10.0 to 5.5 ka BP is responsible forthe high rate of sediment and organic matter accumulation in thecoastal lands of southwest India (Nair et al., 2010; Padmalal et al.,2011). The Holocene epoch started with an episode of heavy pre-cipitation, continuing almost until w5.5 ka BP (Prell and Kutzbach,1987; Kale, 2005). This period is often referred to as the HoloceneClimatic Optimum, and the final phase of it coincided with sea levelrise of 3e4 mwith respect to the present level (Mathur et al., 2004;Nair, 2007). Altered landscape, low salinity, and ecological shiftsmade the coastal plains a very good habitat for mangroves andother coastal vegetation. The palynological spectra and pollen sig-natures of mangroves reveal that the environmental conditionshave been conducive for luxuriant mangrove cover in the coastalplains around the Vembanad Lagoon between 6250 and 3880 BP.Such mangrove development seems to be of global significance, asMid-Holocene establishment of mangroves has been recordedelsewhere when the sea level was stabilized during this period(Kumaran et al., 2013). The altered and modified landscape alongwith ecological shifts, as evident in the sedimentary archives andpalynological assemblage, reflect the direct consequences of thegeological events of the Holocene Climatic Optimum.

The signatures of palynological assemblages, other organic-walled microfossils (NPP) and diatoms observed in the clayesiltdominated sequences indicate environmental conditions andecological shifts (Figs. 7 and 8; Table 2). The palynological and NPPsuites reflect pulses of ecological facies, wherein the terrestrial


source is indicated by the pollen of evergreen plants of Culleniaexarillata and members of Euphorbiaceae, and the marine affinityby dinoflagellates and foraminiferal linings. Erosion of sedimentsand accumulation of organic matter in all the clayesilt dominatedsequences is indicated by the spores of Glomus sp. The mangrovefacies is shown by pollen of Rhizophoraceae and salt glands ofHeliospermopsis, while the transitional fresh water flood plainsfacies is distinguished by the spores of Ceratopteris thalictroides(Figs. 7 and 8). However, the sediment and organic supply to thelagoon towards the later part of the Middle Holocene since 5.5 kaBP have been restricted, linked to a gradual reduction in the rainfall.The progressively reduced river water influx into the lagoon, risingsea level, and the longshore currents are responsible for thedevelopment of barrier sand bodies between the lagoon and thesea. Such an environmental setting is attributed to a palaeoclimaticcondition accompanied by reduction in rainfall since w5.5 ka BP.Although there is no consensus on the exact timing on the initiationof this climatic spell, lines of evidence show that the dry spell wasinitiated just after 5260 � 120 BP in southern Kerala (Nair et al.,2010).

The interactions of sea level changes and the palaeoclimaticevents had significant impact on the hydrological regimes andsediment accumulation pattern and the subsequent evolution ofthe Vembanad Lagoon. The high rainfall, rising sea level, and thenortherly currents of the EarlyeMiddle Holocene have hadconsiderable roles in the accretion and development of spits in thenearshore region. The large southern half of the Pre-VembanadLagoon evolved from an embayment of the Arabian Sea due toprolongation of a series of barrier spits (Fig. 10). This is not onlyevident from the sandy apron over the Late PleistoceneeHolocenesilt and clay dominated sediments (Fig. 5), but also from thepeculiar suite of heavy minerals dominated by opaques and silli-manite in the coastal area south of Panavally. The host khondalitesthat provide sillimanite in the sandy sediments are confined to thehinterlands south of Achankovil Shear Zone (Fig. 1). The presence ofsillimanite in the sediments of the Panavally borehole (BHC 5) orslightly north of it, and the absence of almandine garnet, reiteratesthe fact that the Neogene sediments in the uplifted block south ofKarunagappally form a major source of sillimaniteeopaque suite ofheavy minerals (Anooja et al., 2013). The almandine garnets, whichare comparatively less stable under tropical weathering, are ex-pected to be removed completely during weathering/chemicalalteration under sub-aerial exposure. A greater part of the detritalquartz and small amounts of heavy minerals are transportednorthwards by the currents, leaving the bulk of the heavy mineralconcentrates in the coarser size grades in the southern beachplacers. Such a process of segregation of heavy minerals was alsoearlier observed by Babu and Thrivikramji (1993). In contrast, theopaqueeinosilicate suite of heavy minerals in the northern half ofthe Vembanad coast north of Palluruthy evolved from the char-nockite suite of rocks in the hinterlands (Ravindrakumar andSreejith, 2010). However, the anomalous occurrence of inosilicatein the Thannirmukkom borehole in the southern sector might beattributed to the closeness of the location to the eastern char-nockite provenance, as the strand plain here is wider and almostnear the eastern charnockite province. Further, the area might havebeen influenced by sediments brought in from the Meenachil River,draining charnockite dominant hinterlands.

The Vembanad Lagoon has evolved in its present form duringHolocene. Prior to the beginning of Holocene, there existed anexpansive embayment referred to here as the Pre-Vembanad basin.The rising sea level coupled with northward drifting littoral cur-rents in the EarlyeMiddle Holocene were responsible for the pro-gradation and development of sand barriers across the embayment(Fig. 10a). An abundant supply of sediments in the Early Holocene


Fig.

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resulted in construction of the barrier system, whereas reducedsupply caused breaching of the barrier spit into barrier islands(Carter et al., 1989; Vaz et al., 2002). The open lagoon setting of theMiddle Holocene Vembanad Lagoon (Fig. 10b), similar to the oneillustrated by Nichols and Allen (1981), transformed the systeminto a partly closed lagoon with limited inleteoutlet systems in theregressive phase of the Late Holocene (Fig. 10bec). The subsequentdevelopment of barrier beaches and constant supply of sedimentsbrought in by the littoral drift and also the anthropogenic activitiesin the last few decades played a major role in shaping the Vem-banad Lagoon in its present form (Fig. 10d). A major part of theVembanad Lagoon was silted up in the Late Holocene. The lagoonwas separated from the sea by a barrier spit, the breaching of whichinto barrier islands allowed free communication between the seaand the lagoon. With the fall in sea level, this barrier systembecame much more continuous, and the most direct consequencewas a change in the ecology of the lagoon. The sandy mud sub-strates with brackish to near e fresh water condition transformedthe ecological milieu, suitable for the proliferation of molluscs suchas Villorita sp. The shell deposits such as those encountered inKaniyamkulam near Kalarkod dated 3.4 ka BP (Maya et al., 2007)indicate this specialized ecology. Rajendran et al. (1989) have re-ported a date of 3.1 ka BP for the shell bed in the lagoon atMuhamma,w4 km north of Alappuzha. Even these specialized andaerially restricted environments did not last long. In all probability,the localised depressions containing the shells were completelydried, leaving the thin sediment layer overlying the shell bed tosub-aerial exposure and oxidation. The yellow clay/sand acted as atracer bed for the occurrence of shell beds below (Murthy, 1976).The signatures preserved in the marine as well as the terrestrialarchives have found to be valuable for decoding the developmentand evolution of thewetland system associatedwith the VembanadLagoon.

6. Conclusions

The subsurface sedimentary architecture, geomorphology of theVembanad coast, and the chronology of samples from southern tothe northern part indicate that the present day lagoon has evolvedfrom an embayment of the Arabian Sea that existed prior to theHolocene. Although the process of lagoon development was initi-ated by natural events of pre-Holocene, sea level and climatechanges and anthropogenic activity have transformed it consider-ably during the Holocene. The analytical results of the boreholecores reveal the dynamics and development of the coastline sincethe Early Holocene. Sediment supply and sea level fluctuations havebeen the dominant factors responsible for the development ofvarious geomorphic features along the coastal plain of centralKerala. The different units detected by means of sedimentologicaland mineralogical approaches and by the analysis of the palae-ontological and palynological data preserved in the deposits havebeen found to be useful for developing a four-phase model for theevolution of Vembanad Lagoon during the Holocene. The presenceof a marine embayment and altitude of the location almost equal tothe ambient sea level facilitated the earliest marine influenceduring the Early Holocene (9.5e8.0 ka BP). The subsequent for-mation of sand barrier spits across the pre-Holocene embaymentpaved the way for development of the Vembanad Lagoon, thelargest wetland system in southwestern India. Development andprogradation of a sand barrier spit had a direct effect on the coast,as it changed from an open marine condition of the transgressivephase to brackish environment prior to sea-level stabilisationduring the Middle and Late Holocene, later leading to lagoon for-mation. The concomitant barrier spit growth more or less joinedwith the coastline eventually led to a partially closed lagoon during



a stillstand phase. The process of formation of this sand barrier spitand its subsequent development across the embayment probablyaccelerated when the sea level stabilized at the present level. Thus,the altered and modified landscape along with ecological shifts, asevident in the sedimentary archives and palynological assemblageof the coastal plains of Vembanad Lagoon, reflect the direct con-sequences of the geological processes of the Holocene.

Acknowledgements

The authors thank the Director, Centre for Earth Science Studies(CESS), Thiruvananthapuram and Agharkar Research Institute, Punefor extending facilities, encouragement and support. KPNK, KMNand DP thank the Council of Scientific and Industrial Research, NewDelhi and Kerala State Council for Science, Technology and Envi-ronment, Thiruvananthapuram for providing financial support inthe form of sponsored Research projects [24(0275)/05/EMR-II] and[56/2007/KSCSTE] respectively. RBL acknowledges financial sup-port of XVIII e INQUA Congress (2011), Bern, Council of Scientificand Industrial Research (CSIR) and the Indian National ScienceAcademy, New Delhi and the conveners of 46th Session under CMP“Late Quaternary records of coastal evolution” for accepting thepresentation of this paper at INQUA-2011. KPNK and RBLacknowledge the CSIR for ES and SRA awards respectively. Thesuggestions of one of the anonymous reviewers and Prof. R.K.Sukhtankar have been found to be very useful while revising theMS.

References

Amos, C.L., Umgiesser, G., Tosi, L., Townend, I.H., 2010. The coastal morphodynamicsof Venice lagoon, Italy: an introduction. Continental Shelf Research 30, 837e846.

Anonymous, 2011. The List of Wetlands of International Importance. Available at:http://www.ramsar.org/sitelist.pdf (accessed 09 07 13.).

Anooja, S., Padmalal, D., Maya, K., Vishnu Mohan, S., Baburaj, B., 2013. Heavymineral contents and provenance of Late Quaternary sediments of southernKerala, Southwest India. Indian Journal of Geo-Marine Sciences 42, 749e757.

Avramidis, P., Kontopoulos, N., 2009. Holocene evolution and sedimentation rate ofAlikes lagoon, Zakynthos island, Western Greece: preliminary results. eEarth 4,23e29.

Babu, D.S.S., Thrivikramji, K.P., 1993. Palaeogeographic interpretation of Keralabeach placers, southwest coast of India. Indian Journal of Marine Science 22,203e208.

Bird, E.C.F., 1994. Physical setting and geomorphology of coastal lagoons. In:Kjerfve, B.J. (Ed.), Coastal Lagoon Processes. Elsevier, Amsterdam, pp. 9e39.

Bird, E.C.F., 2000. Coastal Geomorphology: an Introduction. John Wiley & Sons,Chichester, 322 pp.

Banerjee, P.K., 1993. Imprints of Late Quaternary climatic and sea level changes onEast and South Indian coast. Geo-Marine Letters 13, 56e60.

Banerjee, P.K., 2000. Holocene and Late Pleistocene sea level fluctuations along theeast coast of India. Marine Geology 167, 243e260.

Caldara, M., Pennetta, L., Simone, O., 2002. Holocene evolution of the Salpi Lagoon(Puglia, Italy). Journal of Coastal Research (Special Issue 36), 124e133.

Carter, R.W.G., Forbes, D.L., Jennings, S.C., Orford, J.D., Show, J., Taylor, R.E., 1989.Barrier and lagoon coast evolution under differing relative sea-level regimes:examples from Ireland and Nova Scotia. Marine Geology 88, 221e242.

Chattopadhyay, S., 2002. Emergence of Kerala coastal plane: a geomorphic analysis.In: Tandon, S.K., Thakur, B. (Eds.), Revenue Advances in Geomorphology, Qua-ternary Geology and Environmental Geo Sciences: Indian Case Studies. ManishaPublications, New Delhi, pp. 287e298.

Cheng, R.T., Casulli, V., Gartner, J.W., 1993. Tidal, residual, intertidal mudflat (TRIM)model and its applications to San Francisco Bay, California. Estuarine Coastaland Shelf Science 36, 235e280.

Cooper, J.A.J., 1994. Lagoons and microtidal coasts. In: Carter, R.W.G.,Woodroffe, C.D. (Eds.), Coastal Evolution: Late Quaternary Shoreline Morpho-dynamics. Cambridge University Press, Cambridge, pp. 219e265.

Davis, R.A., 2002. Coastal Lagoons. Coastal Zones and Estuaries. UNESCO e EOLSS.Sample Chapter. Available at: http://www.eolss.net/Eolss-sampleAll Chapter.aspx (accessed on 11.07.13.).

El Wakeel, S.K., Riley, J.P., 1957. The determination of organic carbon in marinemuds. Journal du conseil international pour l’exploration de la mer 22, 180e183.

Fontolan, G., Pillon, S., delli Quadri, F., Bezzi, A., 2007. Sediment storage at tidalinlets in northern Adriatic lagoons: ebb-tidal delta morphodynamics,


conservation and sand use strategies. Estuarine, Coastal and Shelf Science 75,261e277.

GSI, 1995. Geological and Mineralogical Map of Kerala. Geological Survey of India,Calcutta.

Gönenc, I.E., Wolflin, J.P., 2005. Coastal Lagoons: Ecosystem Processes and Model-ling for Sustainable Use and Development. CRC Press, Boca Raton, Florida, USA.

Hashimi, N.H., Nigam, R., Nair, R.R., Rajagopalan, G., 1995. Holocene sea level fluc-tuations on Western Indian Continental Margin: an update. Journal ofGeological Society of India 46, 157e162.

Isla, F.I., 1995. Coastal lagoons. In: Perillo, G.M.E. (Ed.), Geomorphology and Sedi-mentology of Estuaries, Developments in sedimentology, vol. 53. Elsevier,Amsterdam, pp. 241e272.

Isla, F.I., 2002. Coastal Lagoons. Coastal Zones and Estuaries. UNESCO e EOLSS.Sample Chapter. Available at: http://www.eolss.net/Eolss-sampleAllChapter.aspx (accessed 10.07.13.).

Jackson, M.L., 1967. Soil Chemical Analysis. Prentice-Hall of India Private Limited,New Delhi.

Joseph, S., Thrivikramaji, K.P., 2002. Kayals of Kerala coastal land and implications toQuaternary sea level changes. Memoir Geological Society of India 49, 51e64.

Kale, V.S., 2005. Late Quaternary climate changes: the Indian science. Key NoteAddress. In: Proceedings of the 18th Convention of the IGI and NationalSeminar on Quaternary Climate Changes and Land Forms, pp. 15e28.

Kjerfve, B., 1994. Coastal Lagoon Processes. Elsevier, Amsterdam, The Netherlands.Kjerfve, B., Margill, K.E., 1989. Geographic and hydrodynamic characteristics of

shallow coastal lagoons. Marine Geology 88, 187e199.Kumaran, K.P.N., 2001. Report on Palynological Analysis of Subsurface Samples of

Quaternary Sea Level Oscillations, Geological and Geomorphological Evolutionof South Kerala Sedimentary Basin (DST Project ESS/23/VES/006/98) 22 pp.

Kumaran, K.P.N., Limaye, Ruta B., Padmalal, D., 2012. India’s fragile coast withspecial reference to Late Quaternary environmental dynamics. Proceedings ofthe Indian National Science Academy 78 (3), 343e352.

Kumaran, K.P.N., Limaye, R.B., Padmalal, D., 2013. Mangrove responses to climatechange along the southwestern coast of India during Holocene: evidence frompalynology and geochronology. In: Sundaresan, J., et al. (Eds.), Climate Changeand Island and Coastal Vulnerability. Springer, Capital Publishing Company,pp. 217e238. http://dx.doi.org/10.1007/978-94-007-6016-5_15.

Kurien, C.V., 1971. Ecology of benthos in a tropical estuary. Proceedings of IndianNational Science Academy 38, 158e163.

Kurien, C.V., Damodaran, R., Antony, A., 1975. Bottom fauna of Vembanad Lake.Bulletin of Department of Marine Sciences 4, 987e994.

Kurup, M.B., 1982. Studies in the Systematics and Biology of the Fishes of VembanadLake (PhD thesis). Cochin University of Sciences and Technology, Kochi.

Lakshmanan, P.T., Shyanamma, C.S., Balachand, A.N., Kurup, P.G., Nambisan, P.N.K.,1982. Distribution and seasonal variations of temperature and salinity in Cochinbackwaters. Indian Journal of Marine Sciences 16, 99e102.

Lewis, D.W., 1984. Practical Sedimentology. Hutchinson Ross Publishing Company,Pennsylvania.

Limaye, R.B., 2004. Contribution to Palaeopalynology and Palaeoecology of theCoastal Deposits of Maharashtra, India (PhD thesis). University of Pune, Pune.

Limaye, R.B., Kumaran, K.P.N., Nair, K.M., Padmalal, D., 2007. Non-pollen paly-nomorphs (NPP) as potential palaeoenvironmental indicators in the late qua-ternary sediments of west coast of India. Current Science 92 (10), 1370e1382.

Lloret, J., Marín, A., Marín-Guirao, L., 2008. Is coastal lagoon eutrophication likely tobe aggravated by global climate change? Estuarine Coastal and Shelf Science 78(2), 403e412.

Madricardo, F., Donnici, S., Buogo, S., Cavicchia, P., Lezziero, A., de Carli, F.,Boccardi, E., 2007. Palaeoenvironment reconstruction in the Lagoon of Venicethrough wide-area acoustic surveys and core sampling. Estuarine Coastal andShelf Science 75, 205e213.

Mallik, T.K., Suchindan, G.K., 1984. Some sedimentological aspects of VembanadLake, Kerala, West coast of India. Indian Journal of Marine Science 13, 159e163.

Mange, M.A., Maurer, H.F.W., 1992. Heavy Minerals in Colour. Chapman and Hall,New York.

Mathur, U.B., Pandey, D.K., Bahadur, T., 2004. Falling Late Holocene sea level alongIndian coast. Current Science 87, 439e440.

Maya, K., Babu, K.N., Padmalal, D., Sreebha, S., 2007. Occurrence and Mining ofLimeshell Resources of Vembanad Lake, Kerala. Centre for Earth Science Studies,Thiruvananthapuram, India, 66 pp.

Menon, N.N., Balchand, A.N., Menon, N.R., 2000. Hydrobiology of the Cochinbackwater system e a review. Hydrobiologia 430, 149e183.

Merh, S.S., 1992. Quaternary sea level changes along Indian coasts. Proceedings ofIndian National Science Academy 58 (5), 461e472.

Murthy, Y.G.K., 1976. A review of the Tertiary and Quaternary formations of Kerala esome suggestions. Records of Geological Survey of India 112 (5), 2e8.

Nair, K.K., 2007. Quaternary Geology and Geomorphology of the Coastal Plains ofKerala. Geological Survey of India. Special publications, 73 pp.

Nair, K.M., Kumaran, K.P.N., 2006. Effects of Holocene Climate and Sea LevelChanges on Ecology, Vegetation and Landforms in Coastal Kerala. ProjectCompletion Report Kerala State Council for Science Technology and Environ-ment. Thiruvananthapuram., 41 pp.

Nair, K.M., Rao, M.R., 1980. Stratigraphic Analysis of Kerala Basin. Special publication5. Geological Survey of India, pp. 1e7.

Nair, K.M., Padmalal, D., Kumaran, K.P.N., 2006. Quaternary geology of South Keralasedimentary basin e an outline. Journal of the Geological Society of India 67,165e179.


http://refhub.elsevier.com/S1040-6182(13)00944-0/sref1



http://www.ramsar.org/sitelist.pdf












































http://www.eolss.net/Eolss-sampleAll%20Chapter.aspx

http://www.eolss.net/Eolss-sampleAll%20Chapter.aspx





















http://www.eolss.net/Eolss-sampleAllChapter.aspx

http://www.eolss.net/Eolss-sampleAllChapter.aspx





















http://dx.doi.org/10.1007/978-94-007-6016-5_15


































































Nair, K.M., Padmalal, D., Kumaran, K.P.N., Sreeja, R., Limaye, R.B., Srinivas, R., 2010.Late Quaternary evolution of Ashtamudi e Sasthamkotta lake systems of Kerala,South west India. Journal of Asian Earth Sciences 37, 361e372.

Narayana, A.C., Priju, C.P., 2006. Landform and shoreline changes inferred fromsatellite images along the Central Kerala coast. Journal of the Geological Societyof India 68, 35e49.

Nayar, T.S., 1990. Pollen Flora of Maharashtra State, India. In: International Biosci-ence Series 14. Today & Tomorrow’s Printers and Publishers.

Nichols, M., Allen, G., 1981. Sedimentary Process in Coastal Lagoons. UNESCO,Technical papers in Marine Science 33. In: Coastal Lagoon Research, pp. 27e80.

Nicholls, R.J., 1991. Holocene evolution of the gravel coastline of East Sussex: dis-cussion. Proceedings of the Geologists’ Association 102, 301e306.

Nigam, R., Chaturvedi, S.K., 2006. Do inverted depositional sequences andallochthonous foraminifers in sediments along the coast of Kachchh, NW India,indicate palaeostorm and/or tsunami effect? Geo-Marine Letters 26, 42e50.

Oliveira, A.M., Kjerfve, B., 1993. Environmental responses of a tropical coastal lagoonsystem to hydrological variability: Mundau e Manguaba, Brazil. EstuarineCoastal and Shelf Science 37, 575e591.

Padmalal, D., Kumaran, K.P.N., Nair, K.M., Baijulal, B., Limaye, R.B., Vishnu Mohan, S.,2011. Evolution of the coastal wetland systems of SW India during the Holo-cene: evidence from marine and terrestrial archives of Kollam coast, Kerala.Quaternary International 237, 123e139.

Panda, U.S., Mohanty, P.K., Samal, R.N., 2013. Impact of tidal inlet and its geomor-phological changes on lagoon environment: a numerical model study. EstuarineCoastal and Shelf Science 116, 29e40.

Picard, M.D., 1971. Classification of fine-grained sedimentary rocks. Journal ofSedimentary Petrology 41, 179e195.

Plecha, S., Silva, P.A., Oliveira, A., Dias, J.M., 2011. Evaluation of singlewaves effects onthe morphology evolution of a coastal lagoon inlet. Journal of Coastal Research,1155e1159. Proceedings of the 11th International Coastal Symposium 64.

Prell, W.L., Kutzbach, J.E., 1987. Monsoon variability over the past 150,000 years.Journal of Geophysical Research 92, 8411e8425.

Rajendran, C.P., Rajagopalan, C., Narayanaswami, S., 1989. Quaternary geology ofKerala: evidence from radiocarbon dates. Journal of the Geological Society ofIndia 33, 218e222.

Ravindrakumar, G.R., Sreejith, C., 2010. Relationship between heavy mineral placerdeposits and hinterland rocks of southern Kerala: a new approach for source-to-sink link from the chemistry of garnets. Indian Journal of Geo-Marine Sci-ence 39, 562e571.

Roy, P.S., 1984. New South Wales estuaries: their origin and evolution. In:Thom, B.G. (Ed.), Coastal Geomorphology in Australia. Academic Press, Sydney,pp. 99e121.

Roy, P.S., 1994. Holocene estuary evolutione stratigraphic studies from southeasternAustralia. In:Dalrymple, R.W., Boyd, R., Zaitlin, B.A. (Eds.), Incised-valley Systems:Origin and Sedimentary Sequences. Society of Economic Palaeontologists andMineralogists, Tulsa, OK, pp. 241e263. Special Publication No. 51.

Sankaranarayanan, V.N., Udayavarma, P., Balachandran, K.K., Pylee, A., Jeseph, T.,1986. Estuarine characteristics of the lower reaches of the river Periyar (Cochinbackwaters). Indian Journal of Marine Science 15, 166e170.

Seetharamaiah, J., Farooqui, A., Suryabhagavan, K.V., Nageswara Rao, K., 2005.Evolution of Iskapalli lagoon in Pennar delta region, east coast of India e Asedimentological and palynological approach. Indian Journal of Marine Sciences34, 267e273.


Seralathan, P., Padmalal, D., 1995. Geochemistry of Fe and Mn in the surficial sed-iments of tropical river and estuary, Central Kerala, India e a granulometricapproach. Environmental Geology 254, 270e276.

Serandrei-Barbero, R., Albani, A., Donnici, S., Rizzetto, F., 2006. Past and presentsedimentation rates in the Lagoon of Venice (northern Italy). Estuarine Coastaland Shelf Science 69, 255e269.

Singh, K., Sharma, J., 1996. Diatom and silicoflagellate assemblages from theNeogene sediments of Neill Island, Andaman Sea. In: Pandey, J., Azmi, R.J.,Bhandari, A., Dave, A. (Eds.), Contributions to XV Indian Colloquium onMicropalaeontology and Stratigraphy, Dehra Dun, pp. 695e705.

Soman, K., 2002. Geology of Kerala. Geological Society of India, Bangalore.Somayajulu, B.L.K., 2002. Present and past (Late Quaternary) sea level e available

new information from Indian coastal regions. Memoir Geological Society ofIndia 49, 1e16.

Stutz, S., Prieto, A.R., Isla, F.I., 2006. Holocene evolution of the Mar Chiquita coastallagoon area (Argentina) indicated by pollen analysis. Journal of QuaternaryScience 21 (1), 17e28.

Suzuki, M.S., Figueiredo, R.O., Castro, S.C., Silva, C.F., Pereira, E.A., Silva, J.A.,Aragon, G.T., 2002. Sand bar opening in a coastal lagoon (Lquipari) in theNorthern region of Rio De Janeiro State: hydrological and hydrochemicalchanges. Brazilian Journal of Biology 62, 51e62.

Thampi, P.K., 1997. Mineral resources. In: Thampi, K.B., Nayar, N.M., Nair, C.S. (Eds.),The Natural Resources of Kerala. World Wide Fund for Nature e India, KeralaState Circle, Thiruvananthapuram, pp. 17e25.

Thanikaimoni, G., 1987. Mangrove Palynology. Travaux de la section scientifique etTechnique 24.

Thanikaimoni, G., Caratini, C., Venkatachala, B.S., Ramanujam, C.G.K., Kar, R.K., 1984.Selected tertiary angiosperm pollen from India and their relationship withAfrican tertiary pollen. Travaux de la section scientifique et Technique 19, 1e93.

Tissot, C., Chikhi, H., Nayar, T.S., 1994. Pollen of Wet Evergreen Forests of theWestern Ghats of India. Publications du départment d’écologie, Institut Françaisde Pondicherry.

Traverse, A., 2007. Palaeopalynology, Second ed. Springer, Dordrecht, TheNetherlands.

Umitsu, M., Buman, M., Kawase, K., Woodroffe, C.D., 2001. Holocene palaeoecologyand formation of the Shoalhaven River deltaic e estuarine plains southeastAustralia. The Holocene 11, 407e418.

Vaz, G.G., Banerjee, P.K., 1997. Middle and Late Holocene sea level changes in andaround Pulicat Lagoon, Bay of Bengal, India. Marine Geology 138, 261e271.

Vaz, G.G., Mohapatra, G.P., Hariprasad, M., 2002. Geomorphology and evolution ofBarrier-Lagoon coast in a part of north Andhra Pradesh. Geological Society ofIndia 49, 31e40.

Venkatarathnam, K., 1970. Formation of the barrier spit and other sand ridges nearChilka Lake on the east coast of India. Marine Geology 9, 101e116.

Ward, L.G., Ashley, G.M., 1989. Physical processes and sedimentology of siliclasticdominated lagoonal systems. Marine Geology 88, 181e304.

Williams, G.L., Bujak, J.P., 1985. Mesozoic and Cenozoic dinoflagellates. In:Bolli, H.M., Saunders, J.B., Perch-Nielsen, K. (Eds.), Plankton Stratigraphy.Cambridge University Press, Cambridge, pp. 847e964.

Wolanski, E., 2006. The evolution time scale of micro e tidal estuaries: examplesfrom the Pacific Rim. Estuarine Coastal and Shelf Science 66, 544e549.

Woodroffe, C.D., 2002. Coasts Form, Process and Evolution. Cambridge UniversityPress, UK, p. 623.





















































































































































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