Estuarine Foraminifera from the Gulf of Cambay

0016-7622/2012-80-1-65/$ 1.00 © GEOL. SOC. INDIA

JOURNAL GEOLOGICAL SOCIETY OF INDIAVol.80, July 2012, pp.65-74

Estuarine Foraminifera from the Gulf of Cambay

ANUPAM GHOSH

Center of Advanced Study, Department of Geological Sciences, Jadavpur University, Kolkata – 700032Email: [email protected]

Abstract: A low diversity, epifaunal to infaunal Foraminiferal assemblage widely distributed in sand flats, mud flats andmarshes along the coastal tracts of the Gulf of Cambay. It is dominated by the species of Ammonia, Rotalidium,Murrayinella, Haynesina, Quinqueloculina, Nonionella, Florilus, Elphidium, Trochammina and Miliammina. A triserialplanktonic foraminifer Gallitellia vivans, an indicator of stressed and upwelling areas, is also characteristically presentin the sediments of the estuaries. The paper discusses the systematics and distribution of the Foraminiferal species in themacrotidal estuaries of the Gulf of Cambay.

Keywords: Estuarine foraminifera, Mangrove, Holocene, Gulf of Cambay

The eastern margin of the embayment is defined by a coastalplain flanked by macro-tidal estuaries of the Narmada, Taptiand Mahi rivers. The coastal sand and mud flats are fringedby mangroves on their landward side. The mouths of theseestuaries are characterized by extensive sand banks that areexposed during the low tide and shift from season to season.The rivers also contain many sand banks with shallowchannels in between them. There are also series of submergedsand bars running parallel to the coastline at the mouth ofthe gulf (Malacca bank). A variety of modern depositionalsystems along the embayment has been observed thatincludes estuaries, intertidal flat, fluvial, coastal plain, tidalinlet, mangroves, mouth bars and tidal bars.

Tides in the gulf are semi-diurnal with a spring tide rangeof up to 11 m (Unnikrishnan et al. 1999). The tidal range inthe Gulf of Cambay is the highest in the waters surroundingIndia. Close to the mouths of the larger river complexestidal bars occur within the river channels as the powerfultidal currents running up to 6 knots redistribute sand in themouth of the estuaries (Nayak and Shetye, 2003). No largewaves on the sea surface are observed in this region. Thesalinity in the interior of the gulf near the mouths of themajor rivers ranges from 24.9 ‰ to 27.6 ‰ with an averagevalue of 26.1 ‰ (Rao et al. 1971).

The annual sediment load of the major rivers Narmadaand Tapti are 35.5 x 109 kg and 28.9 x 109 kg respectively,with an average yearly deposition of sediments to a thicknessof 0.03 m at Gulf of Cambay (Chandramohan et al. 2001).But, the particle fluxes are high during both the SW and NEmonsoons in the Arabian Sea. Also the region ischaracterized by upwelling activities (Sharma, 1978). The

INTRODUCTION

The study of modern Foraminifera and their distributionin the estuaries of the Gulf of Cambay is largely overlooked,although there are reports of Foraminifera from the outergulf and the west coast of India (Rao, 1970 a, b; Gajbhiye,1981; Varshney, 1981; Setty, 1984; Nigam, 1984; Nigamand Khare, 1995). The reported foraminifera are typicallyshallow water epifaunal taxa (top 1cm layer). The samplingstrategy of taking top 1 cm samples may under representthe population or diversity of foraminifera. Hence, verticaldistribution within sediments along with lateral distributionis necessary to document the total foraminiferal assemblagesof an area. In view of this, Ghosh et al. (2009) studied bothepifaunal and infaunal Foraminifera of Tapti estuary todistinguish high and low marsh environments. The estuariesin the Gulf of Cambay are also flanked by coastal sand,mudflats and mangroves. The region is environmentallydynamic having a high tidal range, high rainfall and highannual sediment load of a number of rivers debouchingsediments into the gulf. The present study reports theforaminiferal assemblage of this distinctive estuarineembayment on the west coast of India.

ENVIRONMENTAL SETTINGS

The Gulf of Cambay is a macro-tidal estuarineembayment that extends for over 250km in a roughly north-south direction between 21° N and 22° N latitude. It narrowsdramatically in width from about 70 km at the entrance ofthe embayment in the south to a few km at its northernextremity with an average depth of 18-27 m (Rao et al. 1971).

JOUR.GEOL.SOC.INDIA, VOL.80, JULY 2012

66 ANUPAM GHOSH

average rainfall is about 100cm per year in the coastal plains(Bepardekar et al. 2004) and almost 85% of it occurs duringthe southwest monsoon period. The study area thusrepresents a macro-tidal estuary in a high monsoon rainfalland has a high sediment discharge.

MATERIALS AND METHODS

Surface samples of 100 cm3 (10 cm X 10 cm X 1 cm)were collected at twenty four stations covering sand flat/sand bar, mud flat and mangrove marshes along the coastaltracts of the gulf (Fig.1). Selected samples were collectedat different depths up to 15 cm from sediment-waterinterface. The samples were stored in buffered formalin andstained with rose Bengal solution at the field site itself. Thesamples were washed through # 230 mesh sieve and driedin oven at 50°C. Foraminifera were examined underStereozoom Binocular Microscope. They were furtherobserved and illustrated under Scanning ElectronMicroscope (JEOL, JSM).

SYSTEMATICS

In the present study, generic classification ofForaminiferida as proposed by Loeblich and Tappan (1964)has been followed. The taxa were identified using the worksof Loeblich and Tappan (1964), Barker (1960), Horton andEdwards (2006), Nomura and Seto (1992, 2002), Kathal(2002) and Akimoto et al. (2002). All the species areillustrated in Plates 1 and 2.

Order: Foraminiferida Eichwald, 1830Suborder: TEXTULARIINA Delage and Hérouard,

1896Superfamily: LITUOLACEA de Blainbille, 1825Family: Trochamminidae Schwager, 1877

Genus: Trochammina Parker & Jones, 1859Trochammina inflata Montagu, 1808

Pl. 1, Figs. 1-2Nautilus inflatus Montagu, 1808, p. 81, pl. 18, fig. 3.Trochammina inflata (Montagu) - Debenay et al. 2005,

Pl. 1, fig. 5.Remarks: This species occurs in high marsh in Tapti and

Narmada estuaries along the eastern margin of the Gulf ofCambay.

Family: Rzehakinadae Cushman 1953

Genus: Miliammina Heron –Allen & Earland 1930Miliammina fusca Brady ,1870

Pl. 1, Fig. 3

Quinqueloculina fusca Brady, 1870, p. 286, pl. 11, figs. 2a-c.

Miliammina fusca (Brady)-Horton and Edwards, 2006,p. 68, Pl.I, figs. 5a-b.Remarks: It occurs commonly in high marsh along the

eastern margin of the Gulf of Cambay. It is mostly confinedto the vegetated marsh of Tapti and Narmada estuariesalthough rare specimens are recorded from the patchymangroves of Daman in outer gulf.

Family: Ataxophragmiidae Schwager, 1877

Genus: Gaudryinella Plummer ,1931Gaudryinella sp.

Pl. 1, Fig. 4Remarks: This species occurs commonly in sand flats,

mud flats and low marsh along the Gulf of Cambay.

Suborder: MILIOLINA Delage and Herouard, 1896Superfamily: MILIOLACEA Ehrenberg, 1839Family: Miliolidae Ehrenberg, 1839

Genus: Quinqueloculina d’Orbigny, 1826Quinqueloculina seminulum (Linnaeus)

Pl. 1, Fig. 5Miliolina seminulum Williamson, 1858, p. 85, pl. 7, figs.

183-185.Quinqueloculina seminulum(Linné) - Nomura and Seto,

1992, Fig. 15, 3a-b.Remarks: This species is recorded from sand flats, mud

flats and low marsh of inner Gulf of Cambay and along theSaurashtra coast.

Quinqueloculina akneriana d’OrbignyPl. 1, Fig. 6

73° E

21° N

72° E

22° N

N

0 60 Km

Gulf of Cambay

Daman

Bhavnagar

Cambay

SuratTapti R

.

Narmada R.

Mahi R.

Sampling stations

LEGEND

Fig.1. Map showing the sampling stations along the Cambay coast


ESTUARINE FORAMINIFERA FROM THE GULF OF CAMBAY 67

Plate 1. 1&2- Trochammina inflata (S & U); 3- Miliammina fusca (Si); 4- Guadryinella sp. (Si); 5- Quinqueloculina seminulum (Si); 6-Quinqueloculina akneriana (Si); 7- Miliolinella oceanica (Si); 8-Triloculina sp. (Si); 9- Spiroloculina planulata (Si); 10- Rosalinabradyi (U); 11- Cymbaloporetta cf C. bradyi (U); 12- Cancris oblongus (S); 13- Poroeponides lateralis (U); 14- Hopkinsina pacifica(Si); 15 - Brizalina canvallaria (Si); 16 - Bolivina subexcavata (Si); 17- Bulimina sp. (Si); 18- Uvigerina sp. (Si); 19- Dentalina sp. (Si);20- Lagena striata (Si). Legends: S – Spiral view; U – Umbilical view and Si – Side view.

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68 ANUPAM GHOSH

Quinqueloculina akneriana d’Orbigny, 1846, p. 290, pl. 18,figs. 16-20.

Quinqueloculina akneriana (d’Orbigny)- Akimoto et al.,2002, p. 8, Pl. 13, figs. 2a-c.Remarks: This species occurs in intertidal flats of both

sides of the Gulf of Cambay.

Genus: Miliolinella Wiesner, 1931Miliolinella oceanica (Cushman)

Pl. 1, Fig. 7Triloculina oceanica Cushman, 1932, p. 54, pl. 12, figs,

3a-c.Miliolinella oceanica (Cushman) - Akimoto et al., 2002,

p. 9, Pl. 19, figs. 2a-d.Remarks: This species occurs commonly in sand flats,

mud flats and low marsh of the inner gulf.

Genus: Triloculina d’ Orbigny, 1826Triloculina sp.

Pl. 1, Fig. 8Remarks: This species occurs commonly in sand flats,

mud flats and low marsh.

Family: Spiroloculinidae Wiesner, 1920

Genus: Spiroloculina d’ Orbigny, 1826Spiroloculina planulata Cushman, 1929

Pl. 1, Fig. 9Spiroloculina planulata Cushman, p. 41, pl. 8, figs. 2-5.Spiroloculina planulata (Cushman) - Kathal, 2002, p. 123,

Fig. 3, 5a-b.Remarks: This species occurs commonly in sand flats,

mud flats and low marsh of the inner gulf. It has beenreported from offshore Gulf of Cambay.

Suborder: ROTALIINA Delage and Hérouard, 1896Superfamily: NODOSARIACEA Ehrenberg, 1838Family: Nodosariidae Ehrenberg, 1838

Genus: Dentalina Risso 1826Dentalina sp.Pl. 1, Fig. 19

Remarks: Rare occurrences of this species are observedin the intertidal flats.

Genus: Lagena Walker & Jacob, 1798Lagena striata d’Orbigny

Pl. 1, Fig. 20Oolina striata d’Orbigny, 1839, p. 21, pl. 5, fig. 12.Lagena striata (d’Orbigny) – Rao, 1970, p. 16, Pl. IV, fig. 39.

Remarks: This species occurs rarely in tidal flats andalso reported from the offshore gulf.

Lagena laevis Montagu, 1803Pl. 2, Fig. 1

Lagena laevis (Montagu) - Debenay et al., 2001, Pl. 3, fig. 2.Remarks: This species occurs rarely in tidal flats and

also reported from the offshore gulf.

Superfamily: BULIMINACEA Jones 1875Family: Buliminidae Jones 1875

Genus: Bulimina d’Orbigny, 1826Bulimina sp.Pl. 1, Fig. 17

Remarks: Infrequent occurrence of this species is foundin mud flats and low marsh of the Gulf of Cambay.

Family: Uvigerininae Haeckel 1894

Genus: Uvigerina d’Orbigny, 1826Uvigerina sp.Pl. 1, Fig. 18

Remarks: This species occurs occasionally in mud flats,low marsh and tidal channels.

Superfamily: BOLIVINACEA Glaessner 1937Family: Bolivinidae Glaessner 1937

Genus: Brizalina Costa 1856Brizalina canvallaria

Pl. 1, Fig. 15Bolivina canvallaria Millett, 1900, p. 544, pl. 4, fig. 6.Brizalina canvallaria (Millett) - Akimoto et al., 2002,

p. 15, Pl. 40, figs. 3a-c.Remarks: This species occurs commonly in mud flats

and low marsh.

Genus: Bolivina d’Orbigny, 1839Bolivina subexcavata Cushman and Wickenden

Pl. 1, Fig. 16Bolivina subexcavata Cushman and Wickenden, 1929,

p. 9, pl. 4, figs. 4a-b (fide Ellis and Messina, 1940 etseq.)

Bolivina subexcavata (Cushman and Wickenden) - Akimotoet al., 2002, p. 15, Pl. 39, figs. 2a-c.Remarks: This species occurs commonly in mud flats

and low marsh along the Gulf of Cambay.

Superfamily: DISCORBACEA Ehrenberg, 1838Family: Discorbidae Ehrenberg, 1838

Genus: Rosalina d’Orbigny, 1826Rosalina bradyi (Cushman)

Pl. 1, Fig. 10Discorbis globularis var. bradyi.- Cushman, 1915, pt. 5,

p. 12, pl. 8, figs. 1a-c.



Plate 2. 1- Lagena laevis (Si); 2- Elphidium craticulatam (Si); 3- Elphidium crispum (Si); 4- Haynesina depressula (U); 5- Haynesinagermanica (U); 6 & 7- Rotalidium annectens (S & U); 8 & 9- Pararotalia nipponica (S & U); 10 & 11- Ammonia beccarii (S & U); 12& 13- Ammonia tepida (S & U); 14 & 15- Murrayinella minuta (S & U); 16 - Cribroelphidium gerthi (U); 17- Fursenkoina sp. (Si); 18-Florilus grateloupi (Si); 19- Nonionella cf. N. turgida (Si); 20- Gallitellia vivans (Si). Legends: S – Spiral view; U – Umbilical view andSi – Side view.

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70 ANUPAM GHOSH

Rosalina bradyi (Cushman) – Debenay et al. 2005, Pl. 3,fig 22.Remarks: This is the only calcareous species whose

living specimens are recorded commonly in high marsh. Itis very frequent in low marsh.

Genus: Cancris de Montfort, 1808Cancris oblongus (Williamson)

Pl. 1, Fig. 12Rotalina oblonga Williamson, 1848, p. 51, pl. 4, figs. 98-

100.Cancris oblongus (Williamson) – Brady, 1960, Pl. CVI, figs.

4-5.Remarks: Sporadic occurrences of this species are found

in mud flats and low marsh.

Family: Eponididae Hofker, 1951

Genus: Poroeponides Cushman, 1944Poroeponides lateralis (Terquem)

Pl. 1, Fig. 13Rosalina lateralis Terquem, 1878, p. 25, pl. 2, fig. 11.Poroeponides lateralis (Terquem) - Talib and Farooqui,

2007, Pl.I, fig. 18.Remarks: This species is found in tidal flats of Daman

in outer gulf. It has also been reported from Saurashtra coast.

Superfamily: TURRILINACEA Cushman, 1927Family: Tosaiidae Saidova, 1981

Genus: Hopkinsina Howe and Wallace, 1932Hopkinsina pacifica Cushman

Pl. 1, Fig. 14Hopkinsina pacifica Cushman, 1933a, p. 86, pl. 8, figs. 16a-

b.Hopkinsina pacifica (Cushman)- Akimoto et al. 2002,

p. 15, Pl. 43, figs. 1a-c.Remarks: This species occurs in sand flats, mud flats

and low marsh along the Gulf of Cambay.

Superfamily: ROTALIACEA Ehrenberg, 1839Family: Elphidiidae Galloway, 1933

Genus: Elphidium de Montfort, 1808Elphidium craticulatam (Fitchel and Moll)

Pl. 2, Fig. 2Nautilus craticulatus Fitchel and Moll, 1798, p. 51, pl. 5,

figs. h-k.Elphidium craticulatam (Fitchell and Moll) - Talib and

Farooqui, 2007, Pl.I, fig. 24.Remarks: This species occurs commonly in sand flats,

mud flats and low marsh of both inner and outer gulf. It hasalso been reported from Saurashtra coast. The specimens of

this species in outer gulf are much larger than that occurringin the inner gulf.

Elphidium crispum (Linnaeus)Pl. 2, Fig. 3

Nautilus crispus Linnaeus, 1758, p. 709Elphidium crispum (Linnaeus) – Nomura and Seto, 1992,

Fig. 16, 1.Remarks: This species occurs commonly in sand flats,

mud flats and low marsh of both inner and outer gulf. Thespecimens of this species in outer gulf are much larger thanthat occurring in the inner gulf. It has also been reportedfrom Saurashtra coast.

Genus: Haynesina Banner & Culver, 1978Haynesina germanica Ehrenberg, 1840

Pl. 2, Fig. 5Nonionina germanica Ehrenberg, 1840a, p. 23 [figured in

Ehrenberg, 1840b, pl. 2, figs. 1a-g].Haynesina germanica Banner and Culver, 1978, p. 191, pl.

4, figs. 1-6, pl. 5, figs. 1-8, pl. 6, figs. 1-7, pl. 7, figs. 1-6, pl. 8, figs. 1-10, pl. 9, figs. 1-11, 15, 18.Remarks: This species is found only in the estuaries. It

has not been reported earlier for the offshore Gulf of Cambay.It also occurs in the exposed Pleistocene-Holocene sectionsof Narmada and Mahi rivers.

Haynesina depressula Walker& Jacob, 1798Pl. 2, Fig. 4

Nautilus depressulus Walker and Jacob, 1798, p. 641,pl. 14, fig. 33.

Haynesina depressula (Walker and Jacob)- Banner andCulver, 1978, p. 198, Pl. 10, figs. 1-8.Remarks: This species occurs less commonly than

Haynesina germanica in the estuarine environments of theGulf of Cambay.

Genus: Cribroelphidium, Cushman and Brönnimann, 1948Cribroelphidium gerthi Van Voorthuysen, 1957

Pl. 2, Fig. 16Cribroelphidium gerthi (Van Voorthuysen) - Debenay et al.,

2001, Pl. 6, fig. 15.Remarks: This species occurs occasionally in mud flats

and low marsh.

Family: Rotaliidae, Ehrenberg, 1839Genus: Rotalidium Asano, 1936

Rotalidium annectens (Parker and Jones)Pl. 2, Figs. 6-7

Rotalia beccarii (Linné) var. annectens.-Parker and Jones,1865, p. 381-422, pl. 19, figs. 11a-c



Cavarotalia annectens (Parker and Jones) - Kathal, p. 147,Fig. 7, 5a-c.Remarks: This species occurs in open marine

environments of Daman and Saurashtra coast. It was referredto Cavarotalia by earlier workers. Loeblich and Tappan(1988) have considered Cavarotalia as a junior synonymof Rotalidium.

Genus: Pararotalia Y. Le Calvez, 1949Pararotalia nipponica (Asano)

Pl. 2, Figs. 8-9Rotalia nipponica(Asano), 1936, v. 43, no. 515, p. 614, pl.

31, figs. 2a-c.Pararotalia nipponica (Asano) –Nomura and Seto, 1992,

Fig. 14, 9a-b.Remarks: This species occurs occasionally in sand flats

of outer gulf. It is also reported from Saurashtra coast.

Genus: Ammonia Brünnich, 1972Ammonia beccarii (Linne)

Pl. 2, Figs. 10-11Nautilus beccarii (Linné), Syst. Nat., Ed. 10, vol. 1, p. 710.Ammonia beccarii (Linné)-Nomura and Seto, 2002, Pl. 1,

11a-c; 12a-c.Remarks: It occurs abundantly in sand flats, mud flats

and low marsh of both outer and inner gulf. The specimensof inner gulf are distinctly smaller in comparision to thoseof the outer gulf. It also occurs in the exposed Pleistocene-Holocene sections along the Narmada and Mahi rivers.

Ammonia tepida (Cushman)Pl. 2, Figs. 12-13

Rotalia beccarii (Linné) var. tepida-Cushman, 1926,Carnegie Inst., publ. 344, p. 79, pl. 1, fig. 9.

Ammonia tepida (Cushman)-Nomura and Seto, 1992,Fig.14, 8a-c.Remarks: This species occurs abundantly in sand flats,

mud flats and low marsh of the inner and outer gulf. It alsooccurs in the exposed Pleistocene-Holocene sections alongthe Narmada and Mahi rivers.

Genus: Pararotalia Y. Le Calvez, 1949Murrayinella minuta (Takayanagi)

Pl. 2, Figs. 14-15Rotalia?minuta Takayanagi, 1955, p. 52 figs. 29a-c.Murrayinella minuta (Takayanagi)- Nomura and Seto, 2002,

Pl 1, fig 19.Remarks: This species occurs characteristically and

abundantly in mud flats, low marsh and sand flats of theinner gulf. Rare specimens of this species are found in

Daman intertidal flats in outer gulf. This is possibly the firstrecord of Murrayinella from Indian coast.

Superfamily: FURSENKOINACEA Loeblich andTappan, 1961

Family: Fursenkoinidae Loeblich and Tappan, 1961

Genus: Fursenkoina Loeblich and tappan, 1961Pl. 2, Fig. 17

Remarks: This species occurs occasionally in mud flatsand low marsh.

Superfamily: ORBITOIDACEA Schwager, 1876Family: Cymbaloporidae Cushman, 1927

Genus: Cymbaloporetta Cushman, 1928Cymbaloporetta cf. C. bradyi

Pl. 1, Fig. 11Rosalina squammosa d’ Orbigny in De la Sagra, 1839,

*1611, p. 91.Cymbaloporetta cf. C. bradyi (Cushman) - Nomura and Seto,

1992, Fig. 16, 8a-b.Remarks: Rare occurrence of this species is found in

mud flats and low marsh of inner gulf.

Superfamily: CASSIDULINACEA d’Orbigny, 1839Family: NONIONIDAE schultze, 1854

Genus: Florilus De Montfort, 1854Florilus grateloupi (d’ Orbigny)

Pl. 2, Fig. 18Nonionina grateloupi.-d’ Orbigny, 1826, p.294Florilus grateloupi (d’ Orbigny)-Kathal, 2002, p. 141, Fig.

6, 9a-b.Remarks: This species occurs commonly to abundantly

in sand flats, mud flats and low marsh of both inner andouter gulf.

Genus: Nonoinella, Cushman, 1926Nonionella cf. N. turgida (Williamson)

Pl. 2, Fig. 19Rotalia turgida. – Williamson, 1858, p. 50, pl. 4, figs. 95-97.Nonionella turgida (Brady) – Kathal, 2002, p. 142, Fig. 6,

10a-c.Remarks: Low abundance of this species is recorded

from mud flats and low marsh.

Superfamily: HETEROHELICICEA Cushman, 1927Family: Guembelitriidae Montanaro Gallitelli, 1957

Genus: Gallitellia Loeblich and Tappan, 1986Gallitellia vivans (Cushman)

Pl. 2, Fig. 20Guembelitria? vivans Cushman, 1934


72 ANUPAM GHOSH

Gallitellia vivans (Cushman) - Kroon and Nederbragt, 1990,p. 31, Pl.I, figs. 1-10.Remarks: This species is confined to the finest fraction

of the washed residue (63-125 ì). It occurs in goodabundance in the present day tidal flats and estuarinesediments, likely to have been swept by high tides in thisregion. It also occurs at certain specific stratigraphic intervalsin the Pleistocene-Holocene sections. This species isrecorded for the first time from this region.

DISCUSSION

Analysis of foraminiferal distribution indicates thatbenthic foraminifera are widely distributed in sand flats, mudflats and mangroves along the coastal areas of the Gulf ofCambay from Daman (in the south) to Cambay (in north).The calcareous taxa in the assemblage are dominated byAmmonia beccarii, Ammonia tepida, Murrayinella minuta,Haynesina germanica, Haynesina depressula, Rosalinabradyi, Quinqueloculina seminulum and Quinqueloculinaakneriana, The agglutinated species are represented byTrochammina inflata, Gaudryinella sp. and Miliamminafusca. Planktonic foraminifera Gallitellia vivans and someGobigerines are carried into the estuaries by tidal currents.

The seasonal distribution of living, epifaunalforaminifera in different sub-environments of Tapti estuaryis highly variable (Fig.2). Highest numbers of livingforaminifera are found in low and middle marsh, followedby mud flat, sand flat and in high marsh environments. Theabundance of foraminifera is an order of magnitude higherin the fair weather months (February and April) than duringthe monsoon times.

The marshy regions in the estuaries have distinctforaminiferal assemblages. The number of foraminifera

decreases notably from the low to the high marsh (Figure 2)indicating the harsh nature of conditions for survival in thehigh marsh. The low marsh zone, extending from the lowesthigh water (neap tide) to mean high water, is characterizedby Ammonia tepida, Murrayinella minuta, Ammoniabeccarii, Quinqueloculina seminulum, Quinqueloculinaakneriana, Haynesina germanica, Haynesina depressula,Cribroelphidium gerthi and Cymbaloporetta cf. C. bradyi.The high marsh zone, extending from highest high water(spring tide) to mean high water, is inhabited mainly byagglutinated taxa Trochammina inflata and Miliamminafusca and hyaline Rosalina bradyi. The uppermost reachesof the high marsh are not inhabited by foraminifera. It maybe mentioned that Trochammina inflata and Miliamminafusca are mostly found in vegetated marsh. The sedimentsof the low marsh and mudflats typically consists ofMurrayinella minuta, Haynesina spp., Ammonia spp.,Quinqueloculina spp., Brizalina canvallaria, Florilus spp.And Uvigerina spp. Reworked foraminifera are verycommon in sand flats and sand bars. Therefore in spite ofhaving a broadly similar foraminiferal assemblage the sandflats/sand bars can be distinguished from the mudflats/lowmarsh by high taphonomic grades of foraminiferal tests.

Live foraminifera are recorded up to a depth of 10 cmbelow the sediment surface (Fig.3). Three profiles areobserved on plotting the infaunal population with respect tothe sediment depth. The epifaunal groups such as Rosalinabradyi, Haynesina germanica and Nonionella cf N. turgidahave maximum population in the topmost interval (Profile1). Shallow infaunal foraminifera such as Elphidium crispumand Ammonia tepida show similar densities in severalsuccessive intervals, having no clear maximum either at thetop or at bottom intervals (Profile 2).The third type (Profile3), observed in Cribroelphidium gerthi, has a down profile

Fig.2. Seasonal distribution of living epifaunal foraminifera in different sub environments of estuaries



maximum around 4 cm, and it is the deepest infaunalforaminifer in the present area.

The diagnostic assemblages of low and high marshesare useful in interpreting sea-level variation and accuratelydefining the highest tide level (Horton and Edwards, 2006).In the study area Trochammina inflate and Miliammina fuscamark the highest high tide level. The estuarine assemblagediffers from the normal marine foraminifera of the west coast(Rao, 1970 a, b; Setty, 1984; Nigam, 1984; Rao andBalasubramanian, 1996; Bepardekar et al. 2004) by themarked absence of Textularia and the presence ofMurrayinella minuta, Haynesina germanica, Haynesinadepressula and Milliammina fusca. The planktonicforaminifer Gallitellia vivans in the estuarine sediments istypical of the Gulf of Cambay. It may be stated that thisspecies is known to occur in embayments, stressed marineenvironments, high run off and up-welling coastal areas(Kroon and Nederbragt, 1990). The strong tidal current in

the Gulf distributes this planktonic foraminifer into theestuaries.

CONCLUSIONS

The Gulf of Cambay is characterized by high sedimentload, high run off and macro-tidal range. This distinctiveenvironmental condition has marked effect on foraminiferalassemblage. The estuaries in the Gulf are distinctlycharacterized by benthic foraminifera Murrayinella andHaynesina and planktonic foraminifer Gallitellia. A fairlylarge proportion of foraminifera of mudflats and mangrovesinfringing the estuaries are infaunal species. Their depthdistribution within the sediments indicates that Ammoniatepida, Nonionella cf. N. turgida, Rosalina bradyi,Haynesina germanica and Elphidium crispum are epifaunalto intermediate infaunal and Cribroelphidium gerthi is a deepinfaunal species.

Fig.3. Depthwise distribution of infaunal Foraminifera in low marsh environment.

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(Received: 5 April 2011; Revised form accepted: 19 May 2011)

Estuarine Foraminifera from the Gulf of Cambay

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