late cretaceous (santonian-maastrichtian) integrated coccolith-globotruncanid biostratigraphy of...

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Late Cretaceous (Santonian-Maastrichtian) Integrated Coccolith-GlobotruncanidBiostratigraphy of Pelagic Limestones from the Accretionary Prism of Manipur,Northeastern IndiaAuthor(s): Prithiraj Chungkham and Syed A. JafarSource: Micropaleontology, Vol. 44, No. 1 (Spring, 1998), pp. 69-83Published by: The Micropaleontology Project, Inc.Stable URL: http://www.jstor.org/stable/1486085 .

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Late Cretaceous (Santonian - Maastrichtian) integrated Coccolith - Globotruncanid biostratigraphy of pelagic limestones from the accretionary prism of Manipur,

northeastern India

Prithiraj Chungkhaml and Syed A. Jafar2 Centre of Advanced Study in Geology, Panjab University Chandigarh-160014, India

2Birbal Sahni Institute of Palaeobotany, 53 University Road Lucknow-226007, India

ABSTRACT: Employing special preparation techniques, a rich and moderately preserved assemblage of planktonic foraminifera and coccoliths is documented from pelagic limestones of Melange Zone of Manipur ophiolite belt around Ukhrul area in northeastern India. Integrated biostratigraphy of five exotic limestone blocks encompassing a Late Santonian / Early Campanian to Late Maastrichtian time slice is established; the low-latitude calcareous plankton zones of deep-sea facies identified in such a convergent plate margin terrain, are correlated with published new biostratigraphic, geomagnetic and absolute time scale data. Initial rifting and birth of the Indo-Myanmar ocean took place prior to Latest Santonian / Earliest Campanian and suturing was initiated by Latest Maastrichtian, as suggested by our study.

INTRODUCTION

Along the eastern border between India and Myanmar, the ophiolites and the associated suite of rocks are exposed in thickly forested hills of Nagaland and Manipur (text-fig. 1); these represent a part of northerly extension of Sunda Arch- Trench System linking the Alpine-Himalaya and the Andaman-Nicobar Islands (Ranga Rao 1983; Acharyya et al. 1986, 1989). Rock units exposed in the Nagaland-Manipur hills can be broadly grouped from west to east, representing various stages of basin evolution and orogeny into the following:

Facies Molasse Flysch Olistostromal deposits Ophiolite suite

Metamorphic

Lithounits Barail Group Disang Formation Melange Zone Oceanic Pelagic Sediments, Nagaland Ophiolite/Manipur Ophiolite Naga Metamorphic Complex

Structurally, each of these units is overthrust by the next from the east and folded all together. The flyschoid Disang Forma- tion gradually merges into the post-orogenic mollassic Barail Group of rocks towards the west. In the northern part of Ma- nipur ophiolite belt in the Ukhrul district, the Melange Zone occurs along linear zones within the flyschoid shales of Disang Formation (text-fig. 1). The Melange Zone is characterised by the occurrence of exotic blocks of varying size (a few centime- tres to tens of meters) composed of micritic limestone, marl, sandstone, basic rocks and conglomerate embedded in matrix of flyschoid rocks. The olistolithic blocks of pelagic limestones and chert could be hitherto dated as Late Cretaceous (Late San- tonian to Late Maastrichtian) (Acharyya et al. 1986; Mitra et al. 1986, Chungkham 1996 and Chungkham and Caron 1996). Generally, the microfossil assemblages recovered from pelagic limestone blocks are comprised of coccoliths, planktonic foraminifera (plates 1-4), benthic foraminifera, radiolaria, ostra-

codes and a few shark placoid scales. Only selected index species of coccoliths and planktonic foraminifera are documented in the present work. Since high resolution age determi- nation by using calcareous planktonic microfossils is crucial for understanding the basin evolution involving rifting, disruption and suturing events of ocean-floor in this arch-trench system, the objectives of the present work are: 1. To study the taxonomy and distribution of planktonic foraminifera and coccoliths, for constructing an integrated biostratigraphy based on the examination of the same sample. 2. To correlate the integrated biozonation with more recently published geomagnetic and absolute time scales for transoce- anic correlations. 3. To contribute to the dating of the basin evolution.

MATERIAL AND METHODS

120 samples were collected by one of us (P. Chungkham) from three main areas namely, Kangkhui, Hundung and Lambui. Five sections from five exotic blocks were studied specifically, Kangkhui, Hundung North Upper Band, Hundung North Lower Band, Hundung South and Mova (text-figs. 1-4). The Kangkhui section lying close to the ophiolite suite, served as the type for local intrabasinal correlations. Only limited number of samples taken from control points were analysed for the integrated coccolith-globotruncanid study. It is well known that olistolithic pelagic limestone blocks are found in chaotic disposition within a highly sheared matrix, thus hampering the sampling in strict stratigraphic order and regular interval. Considering heavy vegetation cover, the positions of sections were clearly marked on each block by driving iron nails.

Planktonic foraminifera

The limestones were processed with a modified maceration technique earlier developed by Zolnaj (1979). 300 to 500 specimens from each sample were picked from 60 to 100 mesh size (ASTM) fractions and studied in detail under a normal binocu-

micropaleontology, vol. 44, no. 1, pp. 69-83, text-figures 1-4, plates 1-4, 1998 69



Prithiraj Chungkham and Sved A. Jafar: Late Cretaceous integrated Coccolith-Globotruncanid biostratigraphv, northeastern India

2505 '

9420- 94 25

LEGEND 0

2.5 5 Km LEGEND I I I

.F- BARAIL GROUP (molasse) , DISANG FORMATION (flysch) OCEANIC PELAGIC SEDIMENTS OPHIOLITE SUITE (U. Eocene to Oligocene) (? U. Cretaceous- U. Eocene) (U. Cretaceous)

.--- MELANGE ZONE (matrix, Mid. Eocene)

- exotic block of limestone i exotic block of chert E, exotic block of sandstone (U. Cretaceous)

3 exotic block of ophiolite [| |exotic block of conglomerate | TECTONIC CONTACT * TOWN

H1= HUNDUNG SOUTH H2= HUNDUNG NORTH UPPER BAND H3= HUNDUNG NORTH LOWER BAND M= MOVA K= KANGKHUI

TEXT-FIGURE 1 Geological sketch map of the area around Hundung, Ukhrul (after Khan and Gupta, 1990).

lar microscope. All the important taxa were studied under the Scanning Electron Microscope (model JEOL JSM-840 A) at the Institut de Gdologie, Universitd de Fribourg, Switzerland. Char- acteristic foraminiferal assemblages were studied in thin sections for some selected samples in conjunction with the study of picked specimens. Slides and picked specimens including SEM negatives are stored at Centre of Advanced Study in Geology, Panjab University, Chandigarh, India, under numbers: VPL/P1 -VPL/P26.

Coccoliths

Due to heavy overgrowth of calcite in the micritic fraction of the pelagic limestones, the coccoliths cannot be isolated by routine methods for light- or electron microscopy. A special needle drill technique was devised to extract finely powdered material from the same limestone pieces already studied for planktonic foraminifera; investment of long working hours proved fruitful in yielding marker coccolith species. Each globotruncanid- bearing sample was carefully drilled with a sharp needle to re- lease a small amount of powdered material which was dispersed in neutral-distilled water, and later routine smear slides were prepared in two sets representing coarse and fine fractions of each sample. Coccoliths were photographed by using 12.5x oculars and a I 00x oil immersion objective under a Leitz Polar-

izing microscope by employing crossed-polarized illumination. Several samples showed fragmentation of large coccoliths and moderate to heavy overgrowth of calcite. Dark coloured limestones with an argillaceous component showed better preservation of coccoliths than the light coloured limestones. Slides and negatives of the photodocumented specimens are stored in the Museum of the Birbal Sahni Institute of Palaeobotany, Lucknow, India, under numbers: 11461-11489.

TAXONOMIC NOTES

Planktonic foraminifera

Only 9 key species are described here, arranged in alphabetic order by generic names. The classification proposed by Loeblich and Tappan (1988) is followed here, except for the genus Dicarinella and the species Globotruncanita calcarata for which the classification proposed by Caron (1985) is followed.

Abathomphalus mayaroensis (Bolli) Plate 1, figures 1, 2

Globotruncana mayaroensis BOLLI 1951, pp. 190, 198, pl. 35, figs. 10- 12.

Abathomphalus mavaroensis (Bolli). - BOLLI, LOEBLICH and TAP- PAN 1957, p. 43, pl. 11, figs. la-c.

70

94?15'



Micropaleontology, vol. 44, no. 1, 1998

U)

i U) 0 0 z z 4 z U)

-,o, LU -C 49 0

18 J ? , tD ' ,11,

? Nb '

~ o:~ ~ ~ CI L/ 18 7 - b t h

S 0** * !* KS1-KS3! M. murus x x x x x x x x

A. mayaroensis Mm.

* KS4 x x x x x x x

A.m

~G. gansa~seri .~ A. cymbiformis . G. gansseri !

* 'KS5 x x'x x x x x x

G.g. _ ... G. aegyptiaca Q.t..,

4 -.-...- " Q.t ----., Q.g., .... .... .. ... . B .p . 5i G.a.

G. havanensis .. --. - -

.-...-.-- "- 4... -- .....0. trifidum E.e.,--

G.c. Ra.

G. calcarata ______ ? ~~~~~~~~Q.t. __ _... ,.._

............................... . Q gothicum . . ... . . ... "G.c. *'!KS6 . .. . x,-- x-x-

- x x x x-x-x- . ,< Q-g . ..-.....

G. ventricosa 1 ....... ... iC. aculeus . .... ..

? KS7 Kx x x x x' x x ............ 4 ....... ............ C.a ..............a. G.v.

* KS B. parca ? KS8 i

- E. eximius

* KS9 Da. M. furcatus

KSIO i

D.a. 2m. ........ ..

0

: a ~1 18~~~~~S

'. t ar I f

1 8 U ~ . It 0

r~~~ i ~ .i=1 A

Q t

co, . 0.

K KK

K K

Mi. ~ ~ ~ ~ ~ ^

*..^-B.p..,~~~~~~~~~~~~~~~~~~~~~~~~~- -X ..B.. .... . ......

x _ x x x x x ~i~~~i:i

M -. il;.:-

L.c.

R.a., . L.g., xx x X x X ^. x x x __~__~ ~ X B . X ........ i;'l:' . ........... Z.s. K:K?KKK i K?K;

K K K K. K K K

*-- = First appearance

TEXT-FIGURE 2 Integrated biostratigraphy of selected nannofossils and planktonic foraminifera from the Kangkhui section.

Remarks: A. mayaroensis differs from other globotruncanids in having two keels composed of radially arranged rugosities, equally developed on all chambers, separated by a wide imper- forate peripheral band. Keel band typically widest at the middle part of each chamber. A. mayaroensis is common in the upper part of the Kangkhui (text-fig. 2) and the Mova (text-fig. 3) sections. It ranges throughout the A. mayaroensis Zone (Late Maastrichtian). The report of A. mayaroensis from Miria Marl of Carnarvon basin by Mcgowran (1968) was the only record from the Indo-Pacific region. Recent reports from Miria Marl (Shafik, 1990) and from south and eastern Indian basins (Govindan 1972; Pandey and Rao 1976) remain uncertain due to lack of photodocumentation. Recently, A. mayaroensis was reported from southern Kerguelen Plateau, South Pacific Ocean (Quilty 1992).

Contusotruncana contusa (Cushman) Plate 1, figures 3a-c

Pulvinulina area Cushman var. contusa CUSHMAN 1926, p.23. No type figure given.

Contusotruncana contusa (Cushman). - LOEBLICH and TAPPAN 1988, p. 468, pl. 503, figs. 1-3.

Remarks: Many intermediate forms between C. fornicata Plum- mer (1931) - C contusa are observed in our material. C. contusa is distinguished from other Contusotruncana in having a strongly convex, conical in shape, spiral side. It ranges from lower part of G. gansserina Zone to A. mayaroensis Zone (Late Maastrichtian). C. contusa is well documented from Indian basins.

71

KANGKHUI SECTION

PLANKTONIC FORAMINIFERAL

ZONES (Robaazynskald and

Caron, 1995) 0 > U-JL I

LITHOLOGY

Sample no.

CALCAREOUS NANNOFOSSIL .

Z Z ZONES Z (Stradner and 4 >

Steinrnetz, 1984) Z L

at_

4

LU

U-

i 4.

0

IL)

0

2- n- . LU c

I- ' E ()

(0 _

LI

s;

U 0

I-. LU C.)

z cr

O z

fl.. 2

n[ o

'

0

tu LU a. a [

55 0 z U)

G. elevata

D. asymetrica

= Last occurrence

1 ? L-~~~~~~~~~~~~~~~~~ I

I

[

>

,



Prithiraj Chungkham and Syed A. Jafar: Late Cretaceous integrated Coccolith-Globotruncanid biostratigraphy, northeastern India

MOVA SECTION HUNDUNG SOUTH SECTION

HUNDUNG NORTH UPPER BAND HUNDUNG NORTH LOWER BAND

LUi It i s

0 Li.

0

0

z PLANKTONIC -w ' CALCAREOUS

FORAMINIFERAL 'r NANNOFOSSIL O ZONES LrrITHOLOGY ZONES Z=

(Robaszynski and 0> (Stradner and < > Caron,1995) u.

Sample Stelnmetz, 1984) ZU No.

a cU a a. a-

0

. . aOl 0'

maa a ce u o,ic!a

a! a 'Cl S C

. :

z F A. mayaroensis 0 1- ~- . . . ... - ..... U,

0 . gansseri

:::i:i::::: . : ::M. murus :

? ::::.::::r.:.'..-- : '

~M.m.. '

* MC3S1 x x x x x X

A.m .*MC3SB X: X X.XX XX

--..- ~ A.cymbiformis $ ' ' ; -. . .

G'. * MC3S15 '~'x x x x XX . ;x

? .'.1

....

X XX X X Xx

XiXi: x x x x xx

ill XX ... x . :illii X:X',X X: ''TX-~ ~X XT

G. gansseri :::- * H1CI3 0i.cmbiormis - XX x x X x

= .......~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~... . .. OZ o

3 "**: m d S7<-E.e.. x x x 'x *

x x x x ^;i x x x x~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~4 m x':% G.calcarata Ggc. -""*:mciS8R^a.'---- HlClS- - - - X x xXX XX XX

H 1 C 1 S2 A. cymbiformis X XX XX X X XX XX

G.aeflyptiaca- "*"H2C1S5" """"""''''''''''"''- Og"" 'x" -J_ i -" x x -

U) G. gans3_r

SH1CIS1S7E X XXX X X XX X X X X' X

0 z

G. alarta G.c. -- SHlCiSa X XX XXXXX-X-

U.I

G. aegyptiaca S H--I---- ...S. .X. .

O z G.havanensis--Ga Q. trifidum . . E.- - - - -a.....

U ? * H2C1S3 a t M X X

o ? G.calcarata G cH2C1S7 - X X X X *H2C1S8R X'XXXX: XXX X X X X

X !,- : Hundung North ̀1 -, .: ,..*.:r*!:.!::::*:*~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~~~~~~~~... ... .. :'....! .: ..i....:..i....^^

: -. .:l !: --- - N i U Lower Band -*- -. .

e H3C1S41XXXX X XXX X X X X X X X X

G. aegyptiaca X

0 ? H2ClS2 X!;:i!J X :

o Z 4 . .....

4G.a'

0 G z U G havanensis -- *-i_..-.... ._ . -..i:l . - - - -... . ., G. havanensis 0. trifidum H3C1S7. E.e.. X X X XX X XXXX X 'X::i X X X-Ee

. . G.calcarata H2m C - X-1S' .a .

o -

3 S'X'X'X^x''X'X x 'x'xX ~x'X '::x XXX

.... ...... ..-: ~~~~~~~~~~~~~. ................ I H u d n N ':rthi .. ...-_. .L..............

0 ~ ~ G~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~.haaesso ......... .... N..;.M..........

a~~~~~~~~~ .a: E~~~~~~~~~ 3LS 7 0. trifidum

2M. - H3ClS7: _ E.e., XXXXXXXXXX XXX X X X 0 0 G. calcarata .!R.a.-......

:~ ~ ~ ~ ~ ~~~~~~~~~~~~~~~~~~~~~~~~~ o_ H3ClS9'; x X X X X X X X X X X X X ''' X

TEXT-FIGURE 3 Integrated biostratigraphy of selected nannofossils and planktonic foraminifera from the four exotic limestone blocks; Mova Section, Hundung South Section, Hundung North Upper Band and Hundung North Lower Band. The smaller dots in the sample position represent samples collected in the field but not plotted.

Dicarinella asymetrica (Sigal) Plate 3, figures 1, 2

Globotruncana asymetrica SIGAL 1952, p. 35, fig. 35. Dicarinella asymetrica (Sigal). - ROBASZYNSKI AND CARON

1979, p. 61, pl. 51, figs. 1-2, pl. 52, figs. 1-2.

Remarks: D. asymetrica is distinguised from other globotruncanids in having two closely spaced keels with prolongation of the second keel surrounding the umbilicus and in having a umbilical-extraumbilical primary aperture. Poorly preserved specimens of D. asymetrica are common in the basal part of the Kangkhui section (text-fig. 2). It ranges throughout the D. asymetrica Zone (Late Santonian to Early Campanian).

Gansserina gansseri (Bolli) Plate 1, figures 4a-c

Globotruncana gansseri BOLLI 1951, p. 196, pl. 35, figs. 1-3. Gansserina gansseri (Bolli). - ROBASZYNSKI ET AL. 1984, pp.

294-6, pl. 52, figs. 1-5, pl. 53, figs. 1-5.

Remarks: G. gansseri is characterised by a planoconvex profile, with inflated chambers, surface covered with thick pustules on the umbilical side. It is very common in the upper part of Kang- khui (text-fig. 2), Hundung South and Mova sections (text-fig. 3). G. gansseri ranges from G. gansseri Zone to A. mayaroensis Zone (Late Campanian to Late Maastrichtian). It is well documented from Indian Basin.

72

LU

LU C'

LU

In

Co

3 u}

0 'U 0

n- 0 :5

I

............ .. ..... ......... ....... ................. ..,.....----....... ......? .:'. ':' ':'.' :: .2: ? : :; :~ ; r? :>::.???:? :.:?:.?:..- :.:: :i.'.

. . .. . ., . . .. . .: ... " . - i'/-- '" . . . . . . ~ ............. .... . ...................................................................... ? ? :.'....." : ....... :::" ::".:: :.'' .

ova Section:~B~~! ~ I~EI?i?




PLANKTONIC CALCAREOUS FORAMINIFERA NANNOFOSSIL KANGKUI HUNDUNG HUNDUNG HUNDUNG MOVA

ZONES ZONES SECTION NORTH NORTH SOUTH SECTION UPPER BAND LOWER BAND SECTION (Robaszynski and (Stradner and (KS) UPPER BAND LOWER BAND (Hi (MC3S)

Caron, 1995) Steinmetz, 1984) (2 ) (3 ) (HCS)

M. murus l

A. mayaroensis

I 1 i : A.cymbiformis

I ! /,ni G. gansseri V

I J G. aegyptiaca /%\/ /{ N

G. havanensis 0. trifidum . :. I

R. calcarata

0. gothicum

G. ventricosa i C. aculeus

B. parca l l

G. elevata E. eximius I |I

*, a.s ::,c M c:.ctu I

D. asymetrica M. furcatus [ i 2m.

_-_-- ____ ___ _____________ ____

TEXT-FIGURE 4 Correlation and chronostratigraphy of the five exotic limestone blocks. Magnetostratigraphy and absolute ages of the stage boundaries after Gradstein et al. (1994). Shaded portion of the sections were not sampled or were nonfossiliferous.

Globotruncana ventricosa White Plate 2, figures 3-4

Globotruncana canaliculata (Reuss) var. ventricosa WHITE 1928, p. 284, pl. 38, figs. 5a-c.

Remarks: G. ventricosa is easily recognised by its planoconvex profile, with a flat spiral side and strongly convex umbilical side. Two keels on all the chambers are widely spaced and keel band runs parallel to the coiling axis. It ranges from G. ventricosa Zone to A. mayaroensis Zone (Early Campanian to Late Maastrichtian). Wonders (1992) extended the range of G. ventricosa as far as the Lower Santonian in the Exmouth Plateau, Northwest shelf of Australia. However, in our material G. ventricosa is never found occurring with the Late Santonian assem-

blage of Dicarinella asymetrica and Marginotruncana. Thus the value of G. ventricosa as a marker for the Early Campanian (Wonders 1980; Caron 1985) for the Western Tethys can well be extended to the Eastern Tethys.

Globotruncanita calcarata (Cushman) Plate 2, figures 1-2

Globotruncana calcarata CUSHMAN 1927, p. 115, pl. 23, figs. 10 a-b. Globotruncanita calcarata (Cushman). - ROBASZYNSKI ET AL.

1984, p. 224, pl. 25, figs. 1-3.

Remarks: G. calcarata is readily recognised by its tubulospine at junctures of the chambers. Many intermediate forms between G. calcarata and G. subspinosa are observed in our materials.

73




G. calcarata ranges throughout the G. calcarata Zone (Late Campanian).

Globotruncanita elevata (Brotzen) Plate 2, figures 5-7

Rotalia elevata BROTZEN 1934, p. 66, pl. 3, fig. c. Globotruncanita elevata (Brotzen). - ROBASZYNSKI ET AL. 1984,

pp. 228-30, pl. 27, figs. 1-3, pl. 28, figs. 1-3.

Remarks: G. elevata is distinguished from other Globotrun- canita by having a planoconvex profile with a typical central dome and with a strongly convex umbilical side. G. elevata is rare and recorded from the lower part of Kangkhui section, D. asymetrica Zone to G. calcarata Zone (text-fig. 2) and from G. calcarata Zone, Hundung North sections (text-figs. 3). In the Exmouth Plateau, Northwest Shelf of Australia, G. elevata is reported to appear earlier than D. asymetrica (Wonders, 1992).

Hedbergella flandrini Porthault Plate 3, figures 3a-c

Hedbergella flandrini PORTHAULT 1970, pp. 64-5, pl. 10, figs. 1-3.

Remarks: Few specimens of H. flandrini are recorded from D. asymetrica Zone, Kangkhui section (text-figs. 2).

Marginotruncana sinuosa Porthault 1970 Plate 3, figures 4a-c

Marginotruncana sinuosa PORTHAULT 1970, p.81, pl. 11, figs. 12a-b.

Remarks: The genus Marginotruncana is characterised by having a strongly compressed profile and an extraumbilical- umbilical primary aperture. Marginotruncana is reported from various DSDP sites from Indo-pacific regions: Ninetyeast Ridge, Eastern Indian Ocean (Eijden and Smit 1991); Exmouth Plateau, Northwest shelf of Australia (Wonders 1992); South- ern Kerguelen Plateau, South Pacific (Quilty 1992). Margino- truncana spp. are recorded from the D. asymetrica Zone, Kangkhui section (text-fig. 2). The M. sinuosa is distinguished from other Marginotruncana in having a two keels typically forming a sinuous outline.

Other Planktonic foraminifera species recorded

Abathomphalus intermedius (Bolli 1951) Bolli, Loeblich and Tappan 1957

Archaeoglobigerina blowi Pessagno 1967 Contusotruncana fornicata (Plummer 1931) Loeblich and Tap-

pan 1988

Gansserina wiedenmayeri (Gandolfi 1955) Robaszynski et al. 1984

Globigerinelloides prairiehillensis Pessagno 1967 G. volutus (White 1928) Pessagno 1967 Globotruncana aegyptiaca Nakkady 1950 G. arca (Cushman 1926) EL Naggar 1966 G. dupeublei Caron, Gonzalez Donoso, Robaszynski and Won-

ders 1984 G. falsostuarti Sigal 1952 G. linneiana (d'Orbigny 1839) Herm 1965 G. mariei Banner and Blow 1960 G. orientalis EL Naggar 1966 G. pseudoconica Solakius 1982 G. rosetta (Carsey 1926) Robaszynski et al. 1984 Globotruncanella havanensis (Voorwijk 1937) Robaszynski et

al. 1984 G. petaloidea (Gandolfi 1955) Robaszynski et al. 1984 G. pschadae (Keller 1946) Robaszynski et al. 1984 Globotruncanita angulata (Tilev 1951) Robaszynski et al.

1984 G. conica (White 1928) Robaszynski et al. 1984 G. pettersi (Gandolfi 1955) Robaszynski et al. 1984 G. stuarti (de Lapparent 1918) Robaszynski et al. 1984 G. stuartiformis (Dalbiez 1955) Robaszynski et al. 1984 G. subspinosa (Pessagno 1960) Robaszynski et al. 1984 Gublerina acuta De Klasz 1953 G. cuvillieri Kikoine 1948 Hedbergella holmdelensis Olsson 1964 Heterohelix globulosa (Ehrenberg 1840) Pessagno 1967 H. labellosa Nederbragt 1991 H. punctulata (Cushman 1938) Nederbragt 1989 H. striata (Ehrenberg 1840) Pessagno 1967 Marginotruncana coronata (Bolli 1945) Pessagno 1967 M. marginata (Ruess 1845) Robaszynski and Caron 1979 M. pseudolinneiana Pessagno 1967 M. undulata (Lehmann 1963) Linares 1977 Planoglobulina acervulinoides (Egger 1899) Martin 1972 Pseudoguembelina costulata (Cushman 1938) Nederbragt

1989 P. excolata (Cushman 1926) Nederbragt 1989 P. palpebra Br6nnimann and Brown 1953 Pseudotextularia elegans (Rzehak 1891) Nash 1981 P. intermedia De Klasz 1953 P. nuttalli (Voorwijk 1937) Nederbragt 1989 Rugoglobigerina hexacamerata Bronnimann 1952 R. macrocephala Br6nnimann 1952 R. rugosa (Plummer 1926) Bronnimann 1952 Rugotruncana subpennyi (Gandolfi 1955) Pessagno 1967

PLATE 1 Bar = lOO1m. VPL-P = depository number

1-2 Abathomphalus mayaroensis (Bolli ) Bolli, Loeblich and Tappan. la, dorsal view; lb, ventral view, VPL- P23/13, MC3S8; A. mayaroensis / A. cymbiformis Zone; 2, axial view, VPL-P25/5, MC3S3; A. mayaroensis /A. cymbiformis Zone, Late Maastrichtian.

3a?c Contusotruncana contusa (Cushman) Korchagin. 3a, dorsal view; 3b, axial view; 3c, ventral view, VPL-

P22/8, MC3S4; A. mayaroensis / A. cymbiformis Zone, Late Maastrichtian.

4a-c Gansserina gansseri (Bolli) Robaszynski et al. 4a, dorsal view; 4b, axial view; 4c, ventral view, VPL- P21/10, MC3S3; A. mayaroensis / A. cymbiformis Zone, Late Maastrichtian.

74



Prithiraj Chungkham and Syed A. Jafar

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micropaleontology, vol. 44, no. 1, 1998

Plate I

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Sigalia decoratissima carpatica (Salaj and Samuel 1963) Ned- erbragt 1991

Calcareous nannofossils

List of Coccolith taxa found and considered in the paper are arranged in alphabetical order by generic names.

Arkhangelskiella cymbiformis Vekshina 1959 Plate 4, figures 1, 2

Remarks: Owing to heavy overgrowth distinction between A. cymbiformis and A. specillata Vekshina 1959 is difficult. Earli- est specimens are recorded from Late Campanian, Q. trifidium/ G. calcarata Zone.

Aspidolithusparcus constrictus (Hattner et al. 1980) Perch-Nielsen 1984 Plate 4, figure 3

Remarks: Even heavily overgrown and fragmented specimens could be identified. Earliest specimens are recorded in the better preserved coccolith assemblage of Q. gothicum / G. calcarata Zone of Kangkhui Section (text-fig.2).

Ceratolithoides aculeus (Stradner 1961) Prins and Sissingh 1977 Plate 4, figure 4

Remarks: Earliest specimens matching natural range are recorded from C. aculeus / G. ventricosa Zone of Kangkhui section (text-fig. 2). A large morphologic variability of specimens is documented from flysch derived material of Mud-volcano of Andaman-Nicobar basin (Jafar 1994). Enhanced frequency and large size of this species denotes tropical setting of deposition.

Cretarhabdus crenulatus Bramlette and Martini 1964 Plate 4, figure 5

Remarks: A large morphologic variability occurs, specially in the degree of ellipticity of coccolith and the nature and number of crenulations. Detailed study of this group may reveal distinct low to high latitude distribution of species. Only pieces of fragmented specimens of large C. conicus were observed.

Cribrocorona gallica (Stradner 1963) Perch-Nielsen 1973 Plate 4, figure 6

Cribrosphaerella ehrenbergii (Arkhangelsky 1912) Deflandre 1952 Plate 4, figures 7, 8

Remarks: This species here is rare, while it is rather common in high latitude assemblages (Perch-Nielsen, 1985).

Eiffellithus eximius (Stover 1966) Perch-Nielsen 1968 Plate 4, figure 9

Eiffellithus turriseiffelii (Deflandre and Fert 1954) Reinhardt 1965 Plate 4, figure 10

Lithraphidites carniolensis serratus Shumenko 1970 Plate 4, figure 11

Remarks: Heavily overgrown specimens were frequently seen at Campanian level.

Manivitella pemmatoidea (Deflandre 1965) Thierstein 1971 Plate 4, figure 12

Micula murus (Martini, 1961) Bukry 1963 Plate 4, figures 13-17

Remarks: Specimens matching the holotype are fairly common in Late Maastrichtian sediments of Europe. In typical specimens observed under the electronmicroscope, one cycle of four elements is reduced, while the opposite cycle of four elements is well developed and distinctly protrudes beyond the cubical outline and arranged in a "Swastika" like pattern (see Perch- Nielsen, 1985 ; Stradner & Steinmetz, 1984 ; Jafar, 1994). Tan- gential orientation of one cycle of elements coupled with slight bending in one plane gives rise to M. praeprinsii n. sp. (holotype fig. 4.7 in Jafar, 1994). Overgrown specimens of M. murus were found only in Kangkhui section (text-fig. 2). Figures 6. 20-21, in Jafar (1994) described as M. murus are variants with multiple reduced cycle of elements on one side. A detailed study of a M. murus suite in low-latitude sections is needed.

Micula praemurus (Bukry 1973) Stradner and Steinmetz 1984 Plate 4, figure 18

Remarks: This is a fairly medium to large cubical species with clean and distinct sutures dividing the four visible elements in a "Swastika" pattern. In contrast the sutures in M. swastika are more complex and wavy. The outline of M. praemurus is square with clean sutures and slightly protruding broad elements (pl.4, fig. 18); in typical M. murus the elements are thinner and distinctly protrude beyond the margin of a squarish outline. Com- parable specimens are known from the older, Late

PLATE 2 Bar = 100m. VPL-P = depository number

1-2 Globotruncanita calcarata (Cushman) Robaszynski et al. la, dorsal view; lb, ventral view, VPL-P7/1, H2C1S3; 2, axial view, VPL-P18/1, H1C1S8; G. calcarata / Q. trifidum Zone, Late Campanian.

34 Globotruncana ventricosa White. 3, dorsal view, VPL-P10/3, H2C1S8; G. calcarata / Q. trifidum Zone, Late Campanian; 4a, axial view; 4b, ventral

view, VPL-P5/5, H2C 1S2; G. aegyptiaca/Q. trifidum Zone, Late Campanian.

5-7 Globotruncanita elevata (Brotzen) Robaszynski et al. 5, dorsal view, VPL-P3/3, H3C1S7; 6, axial view, VPL-P4/7, H3C1S8; 7, ventral view, VPL-P9/8; H2C1S8; G. calcarata/Q. trifidum Zone, Late Cam- panian.

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Micula swastika Stradner & Steinmetz 1984 Plate 4, figures 19, 20

Remarks: Specimens of this species are typically squarish in outline with wavy and complex sutures, otherwise quite similar to that of M. praemurus with simple clean sutures.

Micula sp. Plate 4, figures 21, 22

Remarks: Specimens recognised in our material, Lesser Hima- laya and Andaman-Nicobar basin as Micula sp, (Jafar and Singh, 1992; figs. 59-61; Jafar, 1994; fig. 6.19) are quite distinct. They could be side views of M. murus as suggested by K.v. Salis (pers. commun.). This form ranges from Late Cam- panian to Late Maastrichtian (Q. trifidum to M. murus Zone). Electronmicroscopic study could reveal its proper three dimen- sional morphology.

Parhabdolithus embergeri (Noel 1958) Stradner 1963 Plate 4, figure 23

Prediscosphaera cretacea (Arkhangelsky 1912) Gartner 1968 Plate 4, figure 24

Prediscosphaera sp. Plate 4, figure 25

Quadrum gothicum (Deflandre 1959) Prins and Perch-Nielsen 1977 Plate 4, figsure 26, 27

Remarks: Q. sissinghii Perch-Nielsen (1984) and Q. nitidum (Martini 1961) Prins and Perch-Nielsen (1977) are included in this species. Specimens are similar in appearance to Q. gothicum but those becoming completely dark under crossed ni- cols are referred to as Q. gartneri Prins and Perch-Nielsen (1977) and are recorded as high as Late Campanian Q. trifidum / G. havanensis Zone (pl. 4, fig. 28).

Quadrum trifidum (Stradner 1961) Prins and Perch-Nielsen 1977 Plate 4, figures 29, 30

Remarks: Despite overgrowth, distinct specimens are recorded. Such common occurrence together with other low-latitude rep- resentatives is consistent with published data. Although 3-rayed morphotypes with long arms comparable to Q. sissinghii are

known to co-occur with compact forms displaying outline of an equilateral triangle, the absence of a long armed variety could be of some value and needs further studies. First appearance of this species in G. calcarata Zone is valuable, but the last appearance is rather uncertain, as rare specimens are suspected to lin- ger higher up in section.

Reinhardtites anthophorus (Deflandre 1959) Perch-Nielsen 1968 Plate 4, figure 31

Watznaueria barnesae (Black 1959) Perch-Nielsen 1968 Plate 4, figure 32

Remarks: This is the most common species showing much variation of morphotypes and readily distinguished in heavily overgrown material. Predominance of this species suggests a tropical setting of deposition or simply it may be due to the dis- solution of other species.

Zygodiscus diplogrammus (Deflandre and Fert 1954) Gartner 1968 Plate 4, figure 33

Zygodiscus spiralis Bramlette and Martini 1964 Plate 4, figures 34, 35

Remarks: Occurs sporadically and tiny specimens are prone to overgrowth of calcite. Early appearance is stratigraphically use- ful.

INTEGRATED COCCOLITH-GLOBOTRUNCANID BIOSTRATIGRAPHY

Several coccolith zonation schemes published the for Late Cre- taceous could not be used here (see Shafik 1990), as the key markers were either excluded due to the factors of biogeogra- phy, deep-sea pelagic setting or could not be identified due to heavy calcite overgrowth and/or scarcity of taxa. Checklist oc- currences of important coccolith species are based on several hours of searching of each slide. The coccolith zonation scheme of Stradner and Steinmetz (1984) is adopted with slight modifi- cation (text-figs. 2-4) and integrated with the globotruncanid zonation of Robaszynski and Caron (1995). The tropical deposi- tional setting suggested by the planktonic foraminiferal assemblage and presence of similar marker taxa led to the adoption of the globotruncanid zonation of Robaszynski and Caron (1995). Chronostratigraphic and Magnetostratigraphic calibrations are after Gradstein et al. (1994).

Genuine absence or non-recognition of several taxa like: Luci- anorhabdus cayeuxii, Calculites obscurus, Ceratolithoides

PLATE 3 Bar = 100um. VPL-P = depository number

1-2 Dicarinella asymetrica (Sigal) Robaszynski and Ca- ron. la, dorsal view; lb, ventral view, VPL-P24/17, KS9; 2, axial view, VPL-P25/2, KS9; D. asymetrica / M. furcatus Zone, Late Santonian.

3a-c Hedbergellaflandrini Porthault. 3a, dorsal view; 3b, axial view; 3c, ventral view, VPL-P24/19, KS9; D. asymetrica /M. furcatus Zone, Late Santonian.

4a-c Marginotruncana sinuosa Porthault. 4a, dorsal view; 4b, axial view; 4c, ventral view, VPL-P8/3, KS9; D. asymetrica /M. furcatus Zone, Late Santonian.

78



Prithiraj Chungkham and Syed A. Jafar Plate 3

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micropaleontology, vol. 44, no. 1, 1998 79



Prithiraj Chungkham and SyedA. Jafar: Late Cretaceous integrated Coccolith-Globotruncanid biostratigraphy, northeastern India

kamptneri, Ceratolithoides verbeekii, Kamptnerius magnificus, Bukryaster hayi, Lithastrinus grillii, Eprolithusfloralis, Trano- lithus phacelosus, Reinhardtites levis, Lithraphidites quadra- tus and Micula prinsii required the usage of the biozonation scheme of Stradner and Steinmetz (1984).

Kangkhui Section

Lying close to the the ophiolite belt (text-figs. 1-2), this contains nannofloras, displaying much fragmentation, etching and calcite overgrowth (pl. 4). Only better preserved specimens per- mitting specific identifications are documented. Samples KS1O, KS9 forming the basal part of the section represent oldest level of all the sections studied and are assigned to D. asymetrica Zone of Latest Santonian to Early Campanian age based on the occurrence of D. asymetrica. The recovered nannoflora suggests an age close to Santonian / Campanian boundary. Watzn-

aueria barnesae is the most dominant species in this and other sections. Samples KS8 and KS7 display poor preservation of coccoliths and did not yield marker A. parcus and the assignment of sample KS 8 to A. parcus lB. parca Zone is indirect and based on placement in G. elevata Zone. Sample KS7 is assigned to C. aculeus Zone based on the presence of nominate marker species. Large and small Micula species occur throughout from the level of sample KSO1 upwards. Comparatively good nannoflora are observed in sample KS6, which is assigned to G. ventricosa / Q. gothicum Zone by the presence of marker coccolith and fair representation of A. parcus constrictus specimens. The latest Campanian / Early Maastrichtian level has not been sampled in Kangkhui section and this gap is covered in Hundung sections (text-fig.4). Sample KS5 is assigned to G. gansseri I A. cymbiformis Zone by the absence of A. parcus, Q. gothicum and Q. trifidum and the presence of A. cymbiformis and G. gansseri.

PLATE 4 All the figures were photographed under crossed-polarized illumination. Magnification X 2200.

1,2 Arkhangelskiella cymbiformis Vekshina. 1, KS5; A. cymbiformis /G. gansseri Zone; 2, H2C1S8; Q. trifidum / G. calcarata Zone.

3 Aspidolithus parcus constrictus (Hattner et al.) Perch-Nielsen. KS6; Q. gothicum/G. calcarata Zone.

4 Ceratolithoides aculeus (Stradner) Prins and Sissingh. KS6; Q. gothicum /G. calcarata Zone.

5 Cretarhabdus crenulatus Bramlette and Martini. KS6; Q. gothicum / G. calcarata Zone.

6 Cribrocorona gallica (Stradner) Perch-Nielsen. MC3S8; A. cymbiformis /A. mayaroensis Zone.

7,8 Cribrosphaerella ehrenbergii (Arkhangelsky) De- flandre. 7, KS6; Q. gothicum /G. calcarata zone; 8, H3C 1S4; Q. trifidum / G. aegyptiaca Zone.

9 Eiffellithus eximius (Stover) Perch-Nielsen. KS9, M. furcatus /D. asymetrica Zone.

10 Eiffellithus turriseiffelii (Deflandre and Fert) Rein- hardt. KS 10; M. furcatus /D. asymetrica Zone.

11 Lithraphidites carniolensis serratus Shumenko. KS6; Q. gothicum / G. calcarata Zone.

12 Manivitella pemmatoidea (Deflandre) Thierstein. KS6; Q. gothicum / G. calcarata Zone.

13-17 Micula murus (Martini) Burky. 13, 14, KS3; 15, 16, KS2; 17, KS1; M. murus/A. mayaroensis Zone.

Fig. 18 Micula praemurus (Bukry) Stradner and Steinmetz. KS4; A. cymbiformis / A. mayaroensis Zone.

19,20 Micula swastika (Prins) Stradner and Steinmetz. 19, KS7; C. aculeus/G. ventricosa Zone; 20, MC3S8; A. cymbiformis /A. mayaroensis Zone.

21,22 Micula sp; 21, KS4; A. cymbiformis /A. mayaroensis Zone; 22, KS3; M. murus /A. mayaroensis Zone.

23 Parhabdolithus embergeri (Noel) Stradner. KS 10; M. furcatus /D. asymetrica Zone.

24 Prediscosphaera cretacea (Arkhangelsky) Gartner. KS6; Q. gothicum / G. calcarata Zone.

25 Prediscosphaera sp. H2C1S8; Q. trifidum / G. calcarata Zone.

26,27 Quadrum gothicum (Deflandre) Prins and Perch- Nielsen. 26, H3C1S9; 27, H2C1S8; Q. trifidum/G. calcarata Zone.

28 Quadrum gartneri Prins and Perch-Nielsen. H 1 C 1 S6; Q. trifidum / G. havanensis Zone.

29,30 Quadrum trifidum (Stradner) Prins and Perch- Nielsen. 29, H2C1S8; Q. trifidum/G. calcarata Zone; 30, H1C1S5; Q. trifidum / G. aegyptiaca Zone.

31 Reinhardtites anthophorus (Deflandre) Perch- Nielsen. KS9; M. furcatus /D. asymetrica Zone.

32 Watznaueria barnesae (Black) Perch-Nielsen. KS 10; M. furcatus /D. asymetrica Zone.

33 Zygodiscus diplogramus (Deflandre and Fert) Gart- ner. H3C1 S9; Q. trifidum / G. calcarata Zone.

34,35 Zygodiscus spiralis Bramlette and Martini. 34, KS6; Q. gothicum / G. calcarata Zone; 35, H2C 1S8; Q. trifidum / G. calcarata Zone.

80




S


Plate 4

81




Sample KS4 is heavily overgrown containing fairly large M. praemurus but lacking typical M. murus specimens (see taxonomic notes); it is assigned to A. mayaroensis Zone by the presence of marker species. Samples KS1, KS2, KS3 represent roughly same level and contain a variety of Micula species including M. murus, hence assigned to A. mayaroensis /M. murus Zone.

Hundung North Upper Band Section

Sample H2C1S8 to H2C1S3 can be assigned to G. calcarata Zone corresponding to the lower part of Q. trifidum Zone of Late Campanian age (text-fig.3) based on the presence G. calcarata and Q. trifidum. Samples H2ClS1 and H2C1S2 are assigned to G. aegyptiaca Zone corresponding to the upper part of Q. trifidium Zone, by the presence of G. aegyptiaca and absence of G. gansseri.

Hundung North Lower Band Section

The argillaceous component in micritic limestone enhances better preservation of nannoflora in this section encompassing Late Campanian (text-figs. 1, 3). Samples H3ClS9 and H3C1S7 could be assigned to lower part of Q. trifidum Zone, corresponding to the upper part of G. calcarata Zone, by the presence of the both markers species. Several species of Micula are present at this level. Specimens of marker Q. trifidum are of medium size and match the outline of an equilateral triangle. Sam- ple H3C1S4 is assigned to upper part of Q. trifidum / G. aegyptiaca Zone by the presence of marker species and the absence of R. anthophorus and E. eximius.

Hundung South Section

Samples in this section contain fragmented and highly overgrown coccoliths, making age assignment a difficult task involving vigourous searching of material. Samples H1ClS8 and H1C1S7 are assigned to G. calcarata / Q. trifidum Zone of Late Campanian age by the presence of marker species (text-fig. 3). Sample H1ClS6 did not yield Q. trifidum, and the absence of G. calcarata and G. aegyptiaca favours assignment to G. havanensis Zone. Typical specimens of Q. trifidum were found in sample H1ClS5 and coupled with the presence of G. aegyptiaca, assignment to upper part of Q. trifidum and G. aegyptiaca Zones is favoured. Samples H1ClS4, H1ClS3, H1ClS2 and H1C1S1 can be assigned to A. cymbiformis Zone by the absence of A. parcus, Q. gothicum and Q. trifidum. More refined assignment of sample H1ClS4 and H1ClS3 to G. aegyptiaca Zone and H1C1S2 and H1C1Sl to G. gansseri Zone is based on the occurrence of marker foraminifera species.

Mova Section

Samples in this section display high fragmentation and overgrowth of coccoliths. The investigated samples contain a variety of small and large specimens of Micula species, but lacked typical forms of M. murus. The samples are assigned to A. cymbiformis Zone, a more refined assgment to G. gansseri and A. mayaroensis Zones is based on the presence of marker planktonic foraminifera species (text-fig. 3).

RESULTS AND DISCUSSION

Precise biostratigraphy of pelagic limestone blocks imbricated within the offscraped trench fill turbidites (Disang Flysch), suggests not only the timing of initial rifting but also the residence time of the oceanic pelagic facies, that vanished on account of final collision and suturing of continents. Integrated coccolith- globotruncanid biostratigraphy of limestone blocks scattered in

Melange Zone of Nagaland-Manipur hills, demonstrate the presence of calcareous planktonic zones encompassing a Late Santonian / Early Campanian to Late Maastrichtian time slice. Our data suggest that initial rifting and creation of the Indo- Myanmar ocean took place prior to Late Santonian time. The residence time of the pelagic facies was at least from Late San- tonian to Late Maastrichtian. The initiation of the suturing processes (subduction / obduction ) leading to the disruption of the ocean floor took place by Latest Maastrichtian.

CONCLUSIONS

1. Employing special preparation techniques, the coccoliths and planktonic foraminifera are extracted and documented from the scattered exotic blocks of pelagic limestone in ophiolitic melange belt of Nagaland-Manipur.

2. Integrated biostratigraphy of five limestone blocks, employing coccoliths and planktonic foraminifera, reveals the presence of a composite sequence of calcareous plankton zones encompassing Latest Santonian / Earliest Campanian to Late Maa- trichtian time slice.

3. Based on high resolution biostratigraphy of oceanic pelagic limestones, early rifting and suturing events could be deduced for Indo-Mynamar ocean. The initial rifting and creation of Indo-Myanmar ocean took place prior to Late Santonian time. The residence time for the pelagic facies was at least from Late Santonian to Late Maastrichtian. By Latest Maastrichtian the initiation of the subduction / obduction processes took place.

ACKNOWLEDGMENTS

The authors are indebted to the Director, Birbal Sahni Institute of Palaeobotany, Lucknow and the Director, Centre for Ad- vanced Study in Geology, Panjab University Chandigarh, for the kind permission to undertake this collaborative project. We are extremely grateful to Prof. K. v. Salis, Zurich, and Prof. D. Herm, Munich, for critical appraisal of the manuscript. The Di- rector, Institut de Geologie, Universite de Fribourg, Switzer- land, is thanked for hospitality in his institute extended to P. Chungkham for two and half years (October 1993-July 1996). Sincere thanks are also due to Mr. Dewi Cao and Mr. Daniel Cuennet for their help and assistance in taking SEM micro- graphs and photography, respectively. Special thanks are due to Prof. Michele Caron, Fribourg, Prof. Ashok Sahni, Chandigarh and Dr. Jagadish Pandey, Dehradun, for the encouragement and keen interest in this work. P. Chungkham expresses gratitude to the Commission Swiss Government Scholarship, for the grant of a fellowship during this work.

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Manuscript received September 27, 1995 Manuscript accepted October 25, 1996

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