CHAPTER II

REVIEW OF PREVIOUS WORK REVIEW OF PREVIOUS WORK

A. STRATIGRAPHY

The Danish ship *Galathea* during her roxmd the world scientific cruise visited in 1840.

Based on this visit. Rink, a member of this cruise,

published his geological observations in 1847* He classi­

fied the roclcs of Nicobar Islands into three major units in ascending order as follows s 1. The Brown Coal Forma­

tion (found in Katchal and some southern Nicobar Islcinds), 2* Igneous rocks s serpentine and gabbro, and 3. Older

Alluviizm (exposed on central and northern Islands of Nicobar)•

Though the islands were under the control of British regime, the second scientific expq,dition was undertaken by

the Austrian in 1857 in the ship 'Novara*® Hochstetter

(1866),‘ the leader of this scientific cruise, ptiblished

his observations on the stratigraphy of Nicobar group of

islands* Ho opined that the Brovm Coal Formation and the Older Alluvium proposed by Rink (1847) are only the facies variations of one and the same formation* He replaced the term 'Older Alluvium' and introduced the term 'Mari' at its place accortsnodating both the Brown Coal Formation and

the Older Alluvium*

Ball (1870) studied for the first time rocks of

both the Andaman and Nicobar Islands and c"»rrelated the Brovm Coal Pormatlon with sandstone shales alternations

near Port Blai.r, Like Hochstetter (1866), he also rejected the term 'Older Alluvium* and preferred to call them as the

Nicobar Clay Formation*

Mallet (1884) accompanied with captain Hobday

visited Barren and Narcondam Islands of Volcanic Origin* Mallet studied the geology of these islands and prepared

a large scale geological map# while captain Hobday

studied the topography of these volcanic islands®^

Oldham (1885) resurveyed the rocks of Andaman

Islands proposing two distinct series for sedimentary formations besides treating separately the intrusives and

metamorphics* His basal series was the Series having Eocene age while the younger upper sedimentary was

named as Archipelago Series assigning the Miocene age to

ito He then correlated the Brown Coal Formation with the Port Blair Series and the Nicobar Clay with the Archi­ pelago Series.

During the field season 1904-05# Tipper explored the Northern and visited Nicobar Islands for a brief period* He could not visit Middle Andaman due to ferocious Jarwa tribe inhabiting L.-.sre* As a result. Tipper®s paper (1911) is entirely devoted to the geology of Andaman Islands. He proposed 'six formations

in the Andaman as follows i 8

Recent and sub-Recent Raised beaches and coral reefs# etco

Miocene Clays of Ritchie* s Archi­ pelago

Miocene (Burdigalian) Poramihiferal limestone, shell marls of Paget Island.

Eocene (Lower Lutetian) Conglomerates of the Nojrth and Middle Islands#' sand­ stones of the South Islands*

Cretaceous Serpentine Series Pre-Tertiary In part Lower Cretaceous* Scattered exposures of quartzites# jaspers and porcellanic limestones*

On the basis of fossil contents and lithology he compared these formations with some of the known forma­ tions like Laki# Gaj, etc. Further# he replaced the term

'Archipelago Series* by the ’Archipelago Group*• Besides

stratigraphical and geological aspects# Tipper covered other interesting aspects like structure# recent sea level changes and rocks of economic importance* Thus# Tipper* s paper is one of the comprehensive papers on the geology of the Andaman Islands*

Gee (1926) accepted the classification proposed by

Oldham (1885) and Tipper (1911) with irtinor changes* He subdivided Archipelago Series into a Lower series of grey and greenish clays# argillaceous sandstones vrith shelly limestones and occasional conglomerate# and an upper more recent subdivision of very loosly consolidated saidstones containing fossils* Like Tipper (1911)# Gee also recog­ 9

nised the Older Sedimentaries and considered them to be of

Cretaceous aga* On the Wilson Island# Gae noted a Lepido- cyclinO. limestone boulder and assigned a Mid-Tertiary age to it.

Narayana Rao (1942) suggested a Late Oligocene or e.n Early Miocene age to the Lepidocyclina limestone# dis­ covered by Gee (1926) on the Wilson Island*

Boileau (1950) suggested the Oligocene age for Archipelago Series of Oldham (1885) « He sxibdivided Archi­ pelago Series into three stages# the Lower Arenaceous

Stage with some limestones and clays? the Middle Argilla­ ceous Stage with sxibordinate sandstones *Diatomites* and the Upper Stage with limestone and sand­ stone* Boileau (op*cit*) first time s3tudied the geology of and named Baratang Formation for the pre-flysch sediments and assigned Juracsic-Cretaceous(?) age for these rocks*

Chandra and Guha (1963), geologists from O.N.G.C. subdivided Archipelago Series into four lithostratigra- phic units in ascending order such as j 1* Strait Sandstone Formation, 2* Round Silt and Chalk Formation, 3* Guitar Liniestone and Calcareous Sandstone Formation# and 4* Long Clay Formation* On the basis of forsminifers and ostracodes they assigned a Lower Miecene age (Burdi- galian) to the Strait Sandstone Formation and Pliocene 10

age to the Guitar Limestone and Calcareous Sandstone Forma­

tion*'

Pawde and Roy (1964) proposed a ne\j classification

for the younger sedimentaries in South Andaman which had

been described under Port Blair Series by Oldham (1885). VJithout assigning any specific name, they have preferred

dividing the rocks on the basis of lithological diversi­ ties into three divisions assigning them an age ranging

from Cretaceous to Recent. They assigned Eocene (Kirthar)

age to conglomerates# grit with calc-lutites and calc- arenites and Upper Eocene to Oligocene age to graywacks.

Chatterji, A.K* (1964) of the geological survey of studied the foraminifers of the Tertiary formations of the South Andaman# the Archipelago and the Little

Andaman and proposed geological sequence of Andaman Islands as follows :

Recent (& Pleistocene ?) Alluvium terraces# raised beaches# wave-cut platform# coral reefs# calcareous tuffa# and shell-limestones of Island.

(c) Interview I Stage : sandstone-limestone of Interview I# and Chitamale limestone of Little Andaman I , containing Lepidocyclina sumatrensi s and Operculi- noides niasi with many algae 11

(b) Upper Argillaceous zones with sandstones and clays containing rich assemblages of radiolarians and plank- tonic forarainifera like Orbulina universa# 0. bilobata# Globiqerina spp*# Globigerl- neides spp»» etc.

(a) Lower Arenaceous zones Lower^Archipelago with the calcarenite beds of Miocene Series') Little Andaman containing Eulepidina dilatata» Cyclo- clypeus spp»» Miogypsinoides dehaarti/ Orbulina spp./ Giobiqerina spp»# etc. and underlying rich foramini- feral limestones of Havelock Wilson IIs*# western coast of Little Andaman containing Miogypslnoides dehaarti# Mieqypsina irregularis# Cycloclypeus indopaciflcus# S* eidae# C, posteidae# Lepidocycllna martini# L* borneensis# L. dilatataT etc. (?)

(c) Graywacke Stage :

Unfossiliferous graywackes Formerly reported as sand­ stones and shales* The age may range from upper-Middle Eocene to Oligocene (?) (b) Grit Stage : coarse­ Bocene(Port Blair grained grits; may be termed (S« Oligocene ?) Series) as sub-graywackes; contain Assillna papillata# Nummu- lites atacicus# N* sxjb- atacicus# Discocyclina sp.» arid a few gastropods and lamellibranchsa The assemblage confirms a Kiirthar age for these beds* (a) Conalbmerate Stage : boulder of older rocks v/ith fine to coarse-grained matrix containing A*daveisi# confirms the Laki age for 12

this stage. Among the older boulders, a Palaeocene limestone boulder is also met with.

Palaeocene (Ranikot) : This has been noted only as a boulder in Laki Con­ glomerates* This is a hard limestone containing Disti- choplax biserialis and ” Rotalia trochidiformls.

Prs-Tertiary formations : Basic and ultrabasic (Cretaceous-Jiirassic 7 ) intrusives with radiolarian cherts and metamorphosed sediments like marble, silicified shales# quartzites# porcellanic limestones, etc* Thus, ha subdivided both the Port Elair Series and Archipelago Series into three subdivisions as shown in the table*

Chatterjee, P*K. (1967) of 0*N.G.C* proposed following stratigraphic sequence*

Pleistoceno Swampy mud flats, coral £c Recent rags and raised beaches — -— Unconfonrdty----

Archipelago Long Clay Formation 200 ft* Guitar Limestone Formation 1500 ft. Neogene Group U nconf oirraity (Mio-Pliocene) Round Chalk & Silt Formation 2000 ft. Strait Sandstone Formation 1700 ft* unconfortnity--- - 13

U. Eocene-(?) P©rt Blair Formation Oligocene 2500 ft* Unconformity —

Palaeocene Igneous Series — — Igneous contact

U* Cretaceous- Baratang Formation Palaeocene 4500 fte -- — Unconformity -

Mesozoic Older Sedimentaries (extending Lnto M. Cretaceous ?)

He suggested a phase of igneous activity between the Baratang Formation and Port Blair Formation*

Kairunakaran# Ray and Saha (1968Q,|^the geologists from Geological Survey of India modified the stratigraphy of Andaman Islands in accordance \^»ith the recommendation of the International Commission on Stratigraphic Nomencla­ ture* They proposed following stratigraphic succession

for Andaman and Nicobar Islands*

Age Group Formation Geotectonic ______Units

Recent Beach sand# swampy clay» Alluvial and Deluvial soil and Gravel Bed (30 m) Unconformity Sub- Skytic or Rutland Conglomeratic Recent Pre-Siwalik Shell-limestone (330 m) to movement Pleisto------Unconformity------H

Age Group Formation Geotectonic Units___

5. Jhirkatang Limestone Lower 4, Muralat Chalk Mio- Archipelago 3. Melville Limestone cene Group 2. Round Chalk 5. Semi- (Aqui- ( > 400 m) 1. Strait Shell Sand- Paralic tanian stone Limestone & Cycle Burdigalian) Conglomerate

Helvetic Movement ------Unconformity

Eocene- Andaman Eugeo- Oligo- Flysch synlinal cene ( > 3000 m) cycle Overlap

3. Nanumagarh Grit 3. Epieugeo- ( including Wright synclinal Myo Numulitic cycle Limestone Member)

Eocene Mithakhari 2. Hope Town Conglomerate to Group (with Tugapur Limestone Upper ( > 700 m) Member) Creta­ ceous 1. Lipa Black Shale 2. Euxinic cycle

Non-Disconformity-

Mesozoic Laramide Serpentinites Opholite Ultrabasic & basic Suite Plutonics Movement Basic & Intermediate Volcanics & Agglomerates

Igneous Intrusion & Extrusion-

Older Quartzites, Radiolarian 1. Open sedimenta- Jaspers and Crystalline Oceanic rise Pelagic Limestone cycle 15

They discarded the Baratang Formation and Port Blair Formation from Andaman stratigraphy and introduced the Mithakhari Group and Andaman Plysch respectively for

them*

While working on foraminifers from Car-Nicobar

Islands# Srinivasan and Sharma (1973a) proposed five sub­ divisions of Archipelago Group in ascending order as (1)

Strait Sandstone Formation (2) Nancowry Silty Mudstone

Formation (3) Long Siltstone Formation (4) Sawai Bay

Formation and (5) Malacca Limestone Formation. According to them the Archipelago Group ranges from Early Miocene to Pleistocene*

Srinivasan and Azmi (1976) modified stratigraphic sequence proposed by Srinivasan and Sharma (1973a) for

Andaman and Nicobar Islands by introducing Round Forma­ tion and Inglis Formation in place of Kancowry Silty

Mudstone Formation* They have dropped the term Malacca

Limestone Formation and introduced tvro new terms Guitar Formation and Neill West Coast Formation above the Sawai Bay Formation* They have shown approximate equivalance between the Sawai Bay Formation of Srinivasan and Sharma (1973a) and Guitar Formation, and Neill West Coast Forma­ tion has replaced the Malacca Limestone Formation*

Srinivasan (1977) distingvdshed twenty planktonic

foraminiferal sonas in the Late Cenosoic sequences of 16

Andaman-Nicobar regions* His study revealed that the initial appearance of Globorotalia kucrleri, Orbulina suturalistf Neogloboguadrina acostaensig« Sphaeroidlnella dehlscens and Globorotalia tiruncatulAncides markf! the beginning of Miocene# the base of Middle Miocene# the base of Late Miocene and the base of Pliocene and Pllo- cene-Pleistocene boundary respectivelvo

Srinivasan (1978) proposed a new chronostrati- graphic divisions of the Andaman and Nicobar Late Cenozoic sediments on the basts of exhaustive fcraminiferal studies and correlated them with the stratigraphic classifications from other regions all over the world. His new strati­ graphic table is as follows *

Series Stage Age

Shompenian Pleistocene Nicobar Taipian Late Pliocene Sawaian Early

Neillian Late Havelockian Middle Ongeian Miocene Archipelago Inglisian Early Jarwaian Andaman!an

After going through the above literature survey, it is evident that very little has been contributed to the 17

stratigraphy of the proper Baratang Island. Mukherjee (1982) treated the geology and stratigraphy of this

island in the paper entitled 'An overviev; of the Palaeo­

gene stratigraphy of the Andaman Island with particular

reference to the Baratang Island*. As this ia the only classification based on the actual studies carried out on Baratang Island, it has been reproduced in the chapter III dealing with geological and stratigraphic obser\^ations

carried out by the author* Mtikherjee clt») classi­

fied the rocks of Baratang Island in four units as follows;

1* Pre Tertiary - Older Sedimentaries,

2. Palaeocene - Baratang Group,

3. Eocene to Upper Oligeocene - Port Blair Group and 4* Lower to Middle Miocene - Archipalago Grou.p»'

B. PALAEONTOLOGY

Schwager (1866) described and illustrated forami-

nifers from the Island collected by . Hochstetter, the geologist on board, during the Novara Expedition of 1857-59. This monographic v/ork is a first detailed accoun’t on palaeontology of Andaman and Nicobar Islands. Passing referenceshave been made to fossil occurrences while describing stratigraphy by Tipper (1911), Gee (1926), Narayana Rao (1942), etc.

Tipper (1911) noted Nummulites and Assilina sp.

from Casuarian Bay and in the conglomerates of North 18

Andaman* He suggested Laki age to the Port Blair Series®

Further, he noticed several other fossils like Trirritalla# lamellibranchs» echinoid spines and a fish tooth from different areas of Andaman Island. Similarly# ill preserved dicotyledonous leaf impressions were noticed by him in the rocks of VJimberleyganj and Baratang Island*

Gee (1926) reported Assilina’granulosa in the Eocene sandstone of Middle Andaman; Nummulites# Nodosaria» Glob.lqerina and Lithothamnlum in limestone of post-Eocene age in the northern part of Middle Andaman; Echinoids and lamellibranchs in the sandstone of Neill Island; lamelli- brenchs and a Dentalium in sandstone of Havelock Island; corals like Torinia* Puscus, Rissoina and lamellibranchs such as Pecten# Venus in the Tertiary rocks of Outram

Island; and Lithothamnium and Lepldocycllna in Mid-Tertiary limestone of Wilson Island.

Narayana Rao (1942) mentioned about the occurrence of Lepidocyclinae^ Operculinoides# Amphisteqlna/ and a few algae in the Lepldocycllna limestone of Andaman Islands* On the basis of these foraminlfers, he suggested a Late Oligocene or an Early Miocene age to these beds.

Those were days# when inpoirtance was given to mega- fossils by leading palaeontologists worldover including India. It took nearly mid of twentieth century, when from

Sawai Bay of Car Nlcobar Island, Jacob and Sastri (1951) 19

listed several species of Tertiary fcrajninifers« In a

series of papers Srinivasan and Sham^-a (1969a, 1969b/ 1973a» 1973b, 1980) initiated the detailed studies on foraminifers from Car-Nicobar’island. In due course of time Srinivasan and his colleagues extended these studies practically covering the entire Andaman and Nicobar Islands arc.

While reviewing the earlier work on palaeontology, a strict chronological sequence has not been followed here, but for the sake of convenience, a review,has been taken

from the older to younger formations and on different groups•

The work on the Cretaceous foraminifers vas initia­ ted by Guha and Madan Mohan (1965). They discovered benthic and planktonic foraminifers like Textularia,

Robulus, Nodosaria, Gueirsbelina, Bolivina, Globotruncana, Globigerina, etc., from Upper Cretaceous rocks in Chand Bagh Nala and Kadamtala localities of . Pandey and Rao (1976) described foraminifers from the rocks of Baratang Formation (Cretaceous-Eocene) exposed in Middle Andaman Island. The fauna comprises species of Heterohelix, Gublerina, Rucroglobigerlna, Globotruncana, etc., indicating Maestrichtian age and compared the fauna with the foraminiferal' fauna of Meghalaya and East coast. From Maya Bander, VIebi village 20

and Tugapur localities of Middle Andaman, Kumar and

Soodan (1976) described and illustrated Early Palaeocene planktonic foraminifers Globoconusa, Sxibbotinai» and

Globorotalla from the Baratang Formation* They compared

their planktonic foraminifera3»j assemblage with the

Globorotalia uncinata sons of Bolli (1957) from Trinidad. Prom the rocks above the Namunagarh Grit in Nav/ashar of

South Andaman# Gurtiraja and Rao (1976) described Upper

Eocene planktonic foraminifers Asslllna# Biplanispira,

Discocvlinay Ntimmulites and Pellatispira* They suggested

the development of fossiliferous Upper Eocene horizon on

the basis of Pellatispira and Blplanisplra, the characteri­ stic Upper Eocene foraminiferal genera in the Andaman Islands above the Kirthar horizon* They compared their proposed horizon with the Pellatispira-Biplanispira horizon of Saipan Islands of South Pacific*

Srinivasan and Sharma (1980) revised the Car-Nicobar foraminifers described by Schwager (1866)• Benthic fora- rainifers include genera like Alabamina» Ammonia, Anomalina, Astacolus, Bolivlna, Brizallna, Bulimina, Calcarlna# Ciblcides, Dentalina# Elphidi\im» Hofkeruva, Laqena, Nodo- saria, Robulus, etc. x^hile planktonic foraminifers include such as Candeina, Globlger j na# Globlq-erlnoides, Glo^ogua- drina, Globorota.ila, Meoqloboquadriha# Sphaeroidinella, etc. indicating Early to Middle Pliocene age to the rocks of

Car Nicobar island* They have shown that the Car Nicobar 21

Formation is referable to Globorotalla tumida flexu osa zone, Globiqerina nepenthes zone and Globorotalla multl- camerata-Pulleniatina obllcrulloculata (S.S«) zone,

Srinivasan (1969# 1975) described and Illustrated a rich assemblage of foraminifera from Miocene of Little

Andaman# Prom the Hut Bay Formation# he discovered 45 planktonic foraminifera species like Gleborotalia foshi lobata# Globorotalla foshi robusta# Globorotalla mayeri# Globocruadrina dehlscens, Sphaeroidinellopsis semlnulina seminulina# Globiqerina nepenthes, Globiqerina decoraperta/ etc® Hs established tvio planktonic foraminiferal zones# namely* Globorotalla foshi lobata zone and Globorotalla foshi robusta zone, Srinivasan and Singh (1980) described five nev; species of benthic foraminifera from Neogene rocks of Little Andaman* These are Bulimina andamanica (Lower Miocena age)# Cibicides hochstetteri (Lower Miocene)# Pararotalia geel (Middle Miocene)# Fursekonia indica (Middle Miocene)# and Ehrenbergina schwaqerl (Lower Miocene).

Kumar (1967) listed and figured about 28 species of Middle to Upper Miocene planktonic foraminifera from the east and west coast of Interview Island* Some of the important genera are as follov;s : Globoqiiadrlna# Globigsrina# Sphaeroidinella# Globorotalla# Hastlqerlna# Orbulina and Globiqerlnoideso Recently# Sharma and-Ravindra Kumar (1985) discovered 27 planktonic foraminifera of Late 22

Miocene age from a clayey to sandy limestone exposed on

the eastern coast of Interview Island* The asserrf^lage

includes species like Globorotalia plesietumlda# Globi-

aerinoides extremu3» Neogloboguadrina acostaensis and

Globorotalia (Tenuitella) anfracta; and represents the Neillian Stage of Srinivasan (1973).

Srinivasan and Srivastava (1972a) described a rich

assemblage of 152 benthic and 51 planktonic foraminifera from Lower Pliocene mudstone in the Chowra Island. They suggested the deposition of this mudstone at Lov;er Middle bathyal depth (5000 ft to 8000 ft) on the basis of fora­

minifera like Osangu.laria» Vulvulina# Stilostomella and

Uviqerina. Further, Srinivasan and Srivastava (1972b# 1975) recorded foraminifers from Nancowry, #

Long-Island# Car Nicobar# Chovrra, etc. contributing to the Neogene biostratigraphy of these regions.

Azmi and Srinivasan (1974) described and illustra­ ted Late Miocene-Pliocene planktonic foraminifera from the silty mudstone exposure of Guitar Island. They

recorded planktonic foraminifera like Globorotalia tumida» PXesiotumida» SphaeroidinellOTSsis sul>dehiscens» tTeoglo- boq-uadrina acostaensis and suggested Late Miocene ageo In addition, they also recovered benthic foraminifera like Karreriella bradyi# Osangularia benqalensis and

Cibicides wueljLerstorf*!. 23

Srinivasan and Rajshekhar (1930) studied plank-

tonic and benthic forariiinifera from Early Miocene Archi­

pelago Series and Late Pliocene Nicobar Series of Outram

Island* Prom Archipelago series they described forami- nifera like Catapsvdrax dlsslmilis» Globiqerinoides

^Ifclapet^turda . Globorotalia siakensis» Globocrixadrina altisplra« Buliminella andamanica# Cibicides hochstetteri# Ehrenbergina schwaqerl/ etc® referable to Catapsvdrax

dissimilis zone and represents the Andamanian Stage. Similarly, from Nicobar Series they discovered foraminifers «• such as Globorotalia menardil» G»tumida» Globlgerina bulloides# Globoguadrlna altispira# Sphaeroidenilla dehisGenSi> Ammobacxilites aaql^.tiQanus» Hofkeruva schx^ageri/

Ammonia .sumatrana# Alabamina arehioelagoensis» etc* referable to Globorotalia tosaensis tenultheca sone and represent the Taipian Stage* Srinivasan and Rajshelchar

(1981) described six new species of benthic foraminifers from Late Cenozoic of Ritchie® s Archipelago* These are

Flabellammina pllocenlca (Pliocene of Outram Island)# Praeglobobulimina sastryl (Upper Miocene of Neill Island)# Rectuvigerina oldhami (Lovrer Miocene of Middle Button Island)# Cibicides helferi (Lovjer Miocene of Havelock Island)# Ellipsodimorpha bengalensls (Lower Miocene of Havelock Island) and Alabamina agchipelagoeneis (Upper

Pliocene of Outram Island).

The cvirsory study of foraminifers from the Miocene 24

rocks of Baratang Island has shown several species in common vjith those dencribed from Ritchie's Archipelago and hence same stratigraphic succession can be suggested for these rocks.

Jacob and Shrivastava (1952) recorded radiolarian fauna like Acanthometron» Acanthosphaera» Xiphostvlusy Semantis* Dictyosyrisg etc. from Miocene clays of Cole- brooke Island. They also discovered occurrence of radio­ larian fauna in clays at Neill, Havelock, John Lawrence# Henry Lavrrance and Outram Islands. Jacob (1954) tenta­ tively identified tv;o genera Stylodictya and Dictyomitlia from radiolarian cherts near Brooksabad at Port Blair in association with Pre-Tertiary ultramafic intrusives# and discussed the significance of the association of Ultra- mafics v/ith radiolarian cherts in sedimentary tectonics*

Jafri (1986) found a rich assemblage of 18 indeter­ minable species of hagiastrids in radiolarian chert outcrop# exposed near southwest of Bambooflat in South

Andaman. He suggested an Early Cretaceous age to this chert after comparing the hagiastrids with the North west Pacific DSDP material. He interpreted that presence of hagiastrids bearing cherts as inlier within the country rock of Port Blair Series# indicated a major uplift or tectonic movement in the Andaman-Nicobarr basin during Eocene periods. Srinivasan, L6mbari and Dave (1983) 25 discovered and illustrated a rich and varied assemblage of radiclarian fauna comprising 50 species belonging to the order Spumellaria and Nassellaria in the Early Miocene sequence exposed at Piu Bay, Colebrook Island*

Guha (1968) described and illustrated from the Miocene Archipelago Series exposed in Interviev/ and Guitar Islands, a rich assemblage of ostracoda fauna v;hich included 32 species shared among 27 genera^ The important genera are Bairdla# Cytherelloidea# Gythero- pteron, Leptocythere, iCrithe, Tribelina, Xestolebris, Caudites# etc* He noted that the most of the species » recorded by him, were earlier recorded from Mio-Plioceae, Pleistocene and Recent of Manila, Malaya, Sumatra, Java and New Zealand#

From the marl of Pliocene age exposed in the v/est coast of Neill Island# Singh ^ al* (1972) and Singh (1976) noticed ostracoda fauna like Bairdia, Krithe, Hermanites, Cytherella, C\>±.heris, Paracythere, etc.

Gee (1926) v?as the first \/ho discovered fossil algal species of the genus Lithot.hamnium as L* nummuli- ticimi and L. suganuni from post-Eocene rocks of ths eastern and northern parts of the Middle Andaman^ He also noticed a fragment of Lithothamnium in foraminiferal limestone at Hut Bay locality of Little Andaman and from Wilson Island in Ritchie's Archipelago. Narayana Rao 26

(1942) only listed the occurrence of Amphlroa oceanica

Coralllna andamanlca from the Lepldocycllna limestone

from the Long Island of Middle Andaman group and considered these beds to be of Late Oligocene or Early Miocene age*

Chatterji and Guiruraja (1972) described and illustrated coralline algae Lithothamnium andamensis^

Lithoporella (Melobesia) melobesioides (Foslie) Foslie, and Distichoplax biserialis from Palaeocene of Cheria Tapu# South Andaman; Lithothamnium wilsonensis# Lithophyllum aff.

L. prelichenoides^ Lithothamnium sp., Corallina roai and 9 Jania sp. (?) from the Lower Miocene of Wilson Island, '' ' " # ■'* Ritchie’s Archipelago and Amphlroa cf. A* prefragllissina and Amphiroa sp. from Lower Miocene of Little Andaman, Again from Miocene rocks of Hiit Bay# Little Andaman Island, Gururaja (1977) recorded a ne\-! alga Neosolenopora ramaraoi.

Kawal Mathur (19B0a) recorded marine alga Audoui- nella membrances from the Baratang Formation exposed in

Middle Andaman at Bakultala. Her subsequent papers (1980b, 1981, 1982) dealt v/ith a Cyanophycean genus Spirulina discovered in the Round Formation exposed in the western coast of Havelock Island, Strait .Sandstone Formation exposed at the South Point, Outram Island and Guitar

Formation exposed at Sir Huge Rose Island* 27

Badve and Kundal (1986) described and illustrated

a rich and varied algal flora in Palaeocene-Eocene sand­ stones exposed at South Creek* They are Cayeuxia anda- manica» Baratanqla densituba^ Permocalcuius sp. cf<. P. irranae^ Etheiia indica# Peyssonnella baratangensis^ Yi' Halimeda chiplonkati and H, _^ha‘kari* They concluded that k the algal flora indicates shallow water depositional condi­ tions for these rocks*

Ghosh and Maitra (1947) described and figured several genera of diatoms sn c h as Navlcula/ Diplonels/ Cymbella# Rephoneis/ Stricta/ Concinodiscus# etc. from the Miocene clays of Car Nicobar Islands* Desikachary and Maheshwari (1958) systematically worked out the fossil diatom flora from Colebrook Island* These include the genera like Rosseiella/ Cosclnodiscus/ Craspedodiscus^ Arachinoidiscusf Rhyphoneis» etc* Mathur (1973) discovered a rich diatom flora comprising genera Actinoptychus/ Asterolampraj Arachnoidlsens» Coscinodiscus» Crammatophora/ Rossiella# Rhaphoneis^ Stlctodlscus and Tricuratium from the Round Formation and Strait Sandstone Formation exposed in the Havelock Island, Ritchie's Archipelago* V/hile working on the Miocene plenktonic foraminifers from Hancowry Formation/ Niccbar "^slands# Srinivasan and Srivastava (1977) recorded the presence.of a new diatom genus Annellus*

Pant and Eadopadhyay (1972), and Mathur (1973b, 7 8

n 1980 c) described calcareous Vlanfoplankton from Chalk Beds of Havelock Island* ?rora the Late Miocene-Early Pliocene mudstone exposed on the north-eastern coast of Neill

Island# Singh and Vimal (1973, 1976) and Singh (1979CL^

noted the presence of n^7.oplankton genus Discoaster.

Singh and Vimal (1976) gave a systematic descrip­ tion of 17 species of the genus Discoaster* They recog­

nised a biostratigraphic zone Discoaster brouweri -

Discoaster variabilis and correlated it with the Ceratov

lithus rugosus z o n e , NN 13 (Late Miocene-Early Pliocene); proposed by Martini (1970), Pant and Misra (1976) descri­ bed and illustrated 4 species of genus Piscoaster, one species of genus Lithostromation and one species of Silicoflegellate genus Dlstephanus in the Miocene clays of Wilson Island.

While working on radiolarian fauna# Jacob and Shrivastava (1952) mentioned about the occurrence of a silicoflagellate genus Dictyocha in the Tertiary clays of

Colebrook Island. Mathur (1975) noticed occurrence of silicoflagellates in the rocks of Havelock Island. From Early Pliocene of Neill Island, Singh ^ al.(1978) described and illustrated diatom and silicoflagellates. Singh (1979b) listed diatom assen^lage which included genera like Actinocyclus, Coscinodiscus> Diplonels, Rhaphoneis, Thalassiothrix, etc, and silicoflagellates 29

include genera Dlstephanus and Dictyocha frora Early

Pliocene of Neill Island® Mathur and Mathur (1980)

described and figured palynofossils'a^^t nanno- « fossils from Late Oligocene of Andaman Island, Banerjee (1966, 1967) recorded Upper Creta'ceous and Tertiary microflora from Andamin Island*

Karunakaran ^ ^,(1964, 1968^j discussed the

sedimentary environment of the Andaman Plysch. Pandey

(1972) commented on the environment of deposition and geological history of Barcitang Formation, Andaman Islands#

Rodolfo (1969a; 1969b) studied sediments, bathyraetry# marine geology, tectonic history, etc. of Andaman Basin*

Poddar (1954) first time reported the presence of mud of volcanoes in Andaman Islands and examined the ejected material from these mud volcanoes for the search of hydrocarbons. Banerjee (1975) reported six mud volcanoes at Baratang Island, tv;o mud volcanoes each at Middle and North Andaman located v/ithin the country rocks of Baratang Formation which ranges from Upper Cretaceous to Lov^er Eocene. He suggested the mechanism of eruption of these mud volcanoes.

Badve et (1984) studied the foraminiferal fauna from the ejected material from mud-'volcanoes located near Jarv/a Creek, Baratang Island® They recorded a mixture 30

of Upper Cretaceous and Miocene forarniniferal fauna from

these mud volcanoes and suggested that the surface rocks around the mud volcanoes may be Miocene or even younger

than the Miocene* The Upper Cretaceous f orarninif eral

fauna include the species of Heterohelix/ Ven-^.lln.brella^

Globotruncana and Miccene assemblage comprises Globigeri-

noides and Globoguadrinae RaJsheJchar (1985) discovered a

few foriaminiferal genera like Ruqoqlobigerina» Globorotalis/

Neoflabellina.? Dentalinar Nodosaria/ Textularia# Plano- qlobulina» etc* from the same mud volcanoes.

Jafar (1935) discovered' a mixed coccolith taxa belonging to Cretaceous and Palaeogene periods from the ejected material from the two mud volcanoes of Baratang

Island. The Cretaceous taxa include Watznauerla^ Mlcula,

Quadrx3m» Manivitellg.# CribroGorona» etc. iv'hile Palaeogene taxa include Tov/eius, ‘^vclicarqciilithus# Discoaster/ Sphenolithus/ etc. He suggested the presence of more or less uninterrupted marine Carapanien - Danian sequence of rocks containing Cretaceous-Tertiary boundary in Andaman basin on the basis of the characteristic coccoliths taxa.