New Ammonoid evidence for theJurassic/Cretaceous boundary in Kachchh Western India, and long...

NEW AMMONOID EVIDENCE FOR THE

JURASSIC/CRETACEOUS BOUNDARY IN KACHCHH

WESTERN INDIA, AND LONG DISTANCE CORRELATION WITH SOUTHERN EUROPE

JAI KRISHNA, DEO BRAT PATHAK & BINDHYACHAL PANDEY

KRISHNA J., PATHAK D.B. & PANDEY B. 1994. New Ammonoid evidence for the Jurassic/Cretaceous boundary in Kachchh, Western India, and long distance correlation with Southern Europe. [Mise en ~vidence par les ammo- no~d~s de la limite Jurassique/Cr~tac~ dans le Kachchh, Ouest de l'Inde et sa correlation ~ grande distance avec le Sud de l'Europe]. GEOBIOS, M,S. 17 : 327-335.

ABSTRACT

The Jurassic/Cretaceous boundary in the ammonoid rich classic Jurassic region of Kachchh could not be precised for well over a century (1871-1991) due to the absence of ammonoids or other guide fossils of the Berriasian. Our present studies now firmly establish the basal Berriasian in Kachchh through close or identical ammonoids Aspi- doceras cf. taverai CHECA, Argentiniceras loncochensis (STEUR), Spiticeras cf. ducale (MATHERON) and Berriasella sp. Relatively, among these, A. taverai CHECA is considered a good marker of the basal Berriasian Jacobi Zone in the Subbetic Spain. Besides precising the Jurassic/Cretaceous boundary in Kachchh, A. cf. taverai CHECA also allows long distance correlation to the precision of a single ammonoid zone across the Tethys between Kachchh (Indo-East-African province) on the south/east margin of the Tethys and Spain (Mediterranean province) on the north/west margin of the Tethys. The episodic presence of the ubiquitous Tethyan Aspidoceras in Kachchh during the Upper Kimmeridgian and basal Berriasian, interestingly, is found to correspond with phases of the eustatic rise of the Vail Cycles LZA 4.6 and LZB 1.4 which in turn suggests significant ammonoid faunal expansion events during the said intervals towards South and East from the Mediterranean to the Indo-East-African province.

KEY-WORDS :ASPIDOCERAS, SPITICERAS, TETHYS, TITHONIAN, BERRIASIAN, EUSTATIC RISE, FAUNAL EXPANSION.

RI~SUMI~

La limite Jurassique/Cr~tac~ clans la classique rdgion de Kachchh, rdputde pour sa richesse en ammonites, n'avait pu ~tre pr~cis~e depuis plus d'un si~cle I i~,ffI-1991) ~ cause de rabsence d'ammonites ou d'autres fossiles indices du Berriasien. Notre prdsente ~tude id~,~./,~:~ fermement le Berriasien basal ~ Kachchh par des ammonites pro- ches ou identifiables aux formes s u i v a n ~ Aspidoceras cf. taverai CHECA, Argentiniceras loncochensis (STEUR), Spiticeras cf. ducale (MATHERON) et Berr~:asella. Parmi celles-ci, A. taverai CHECA est consid~r~e comme un mar- queur relativement bon de la zone ~ Jacobi du Berriasien basal dans la zone subb~tique espagnole. Outre l'int~r~t de pr~ciser la limite Jurassique/Cr~tac~ dans le Kachchh, A. cf. taverai permet une correlation ~ longue distance travers la T~thys ~ la zone d'ammonites p r ~ , entre le Kachchh (province indo-est-africaine) situ~ sur la marge Sud-Est et l 'Espagne (province m~diterran~enne), situ~e sur la marge Nord-Ouest. I1 est int~ressant d'observer que la presence ~pisodique dans la r~gion de Kachchh d'Aspidoceras ubiquistes dans la T~thys pendant te Kimm~- ridgien sup~rieur et le Berriasien basal correspond aux phases d'~l~vation eustatique des cycles LZA 4,6 et LZB 1,4 de Vail, ce qui sugg~re en retour des expansions significatives de faunes d'ammonites vers le Sud et l 'Est durant ces m~mes intervalles, depuis la province m~diterran~enne jusqu'~ la province indo-est-africaine.

MOTS-CLI~S : ASPIDOCERAS, SPITICERAS, TETHYS, TITHONIEN, BERRIASIEN, ]~Lt~VATION EUSTATIQUE, EXPANSION FAUNIQUE.

328

6~ oo' 6 9°Ioo ' 7 4 oo' 7Cioo' 7~ oo'

I " -"~"-~ ~ F"? INDIA o F K A C . C . . \

.~ ~ ~ ,_Pntcham . . . . . . . ( : DELHI " " ' - ~ " f

:::::::.'::i: ~ t

E 0 ¢ E NE ~//f/////~.~" ~'~DECCAN ,RAP ~ ~ ~ ~

JURASSICICRE TACEOUS ~/ / '~ / /~ ~ / " ' / / / j ~ ~ - / ' / ' / / / / / / / / / ~ DO, ¢1oo ' ¢1oo, ,01oo , doo'

21 2~ od

Figure 1 - S c h e m a t i c geological m a p of K a c h c h h wi th impor- t a n t localities. Carte gdologi- que schEmatique de Kachchh avec les localitds principales.

I N T R O D U C T I O N

The ammonoid rich Middle and Upper Jurassic sedimentary sequence of Kachchh (Fig. 1) has been known for over one hundred and fifty years as a classic Jurassic sequence on the southern margin of the Tethys. The early ammonoid systematic studies although without the desired stratigraphic precision go back to Sowerby (1840), Waagen (1871, 1873-75) and Spath (1924, 1927- 33) which made the Kachchh Jurassic sequence famous all over the world as of primary impor- tance in context of the Jurassic strat igraphy and ammonoid fauna. In recent years, ammonoid studies in the Kachchh Jurassic have been revived under rigorest possible stratigraphic precision and these have resulted into several fold impro- vement in the stratigraphic resolution (Cariou & Krishna 1988 ; Cariou et al. 1990 ; Krishna 1983, 1984, 1987, 1991 ; Krishna & Cariou 1986, 1990 ; Krishna & Pa thak 1989, 1991, 1993 ; Krishna & Thierry 1987 ; Krishna & Westermann 1985, 1987 ; Krishna et al. 1983, 1988).

L I T H O S T R A T I G R A P H I C F R A M E W O R K

UMIA FORMATION ( r e v i s e d )

RATROL FORMATION (revised)

CIIARI FORMATION

PATCJlAM FORMATION

BIIII.J MEMBER

UKRA MEMBER

GHIJNER I MEMBER

IIMIA MF.M g ER

UPPER MEMBER

MI DDLE MEMBER

I.OWER MEMBER

DIIOSA OOLITE MEMBER

UPPER MEMBER

MIDDLE MEMBER

LOWER MEMBER

RAIMALRO MEMI]ER

t;ADAPATA MEMI~ER

FLACSTONE MEMBER

BABIA CLIFF MEMBER

KALADOflNGAR MEMBER

DINGY MEMBER

The li thostratigraphic framework of the Jurassic- Cretaceous sedimentary sequence of Kachch_h basin of Western India includes a succession of four well established lithostratigraphic units : Pat- cham Formation (Bajocian to Bathonian), Chari Formation (Lower Callovian to Middle Oxfor- dian), Katrol Formation (late Lower Kimmerid- gian to Lower Berriasian), Umia Formation (late Upper Tithonian to Albian locally even possibly extending to Upper Turonian) in ascending order in the name of Stoliczka 1869 (published in Waa- gen 1873 due to untimely death of Stoliczka) (Fig. 2). The Jurassic/Cretaceous boundary beds

Figure 2 - Mesozoic l i t hos t r a t i g r aph i c f r a m e w o r k in Kachchh . Lithostratigraphie du MEsozoique de Kachchh.

referred in the text are included in the Upper Member of the Katrol Formation in Western Kachchh (Sahera, Mundhan, Lakhapur) and in the Basal Member (Umia Member) of the Umia Formation in Eastern Kachchh sections (Ler - Katrol and Ler - Ghunwari). The relevant lithoco- lumns and correlations are indicated in figure 3.

LAKHAPUR SE OFLER

.B3' E R.

Arg. Loncoc

24 K : a ~ F

MICRACANT 2

2 1 m

T I 19 T H O 17 N I

A N

VIRGATOSPi

RAJNATHI 2

POTTI

329

SW OF LER

A. cf. taverae

Figure 3 - Schematic lithoco- lumns along with demarcation of the Jurassic/Cretaceous boundary at Lakhapur, South- East Ler and South-West Ler. Single lines in between, two successive shale beds indicate very thin sandstones. Coupes

Lakhapur, au SE et au S W de Ler avec indication de la limite Jurassique/Cretacg. Les traits continus entre deux cou- ches successives de shales indi- quent minces niveaux grdseux.

13 HYBONOTU

11

I M M. 7

\ \

\

calc. sandstone med. § coarse sandstone

Lithologically the Upper Member of the Katrol Formation zs dominantly shaly in character throughout the Mainland Kachchh. In the Wes- tern Mainland sections as above the shales in- clude several interbeds of green oolitic glauconitic calcareous, ferruginous marine body fossil bearing sandstones in the lower half starting from the base of the shaly Upper Member, although only three of these bands (more significant) in the Lakhapur section have found special mention in the literature: Most of these bands are rich in body fossils particularly ammonoids of Upper Ti- thonian Micracanthum Zone. In the Mundhan

shale

-50m

i, section 16 such bands with ammonoids have been recorded by us. The ammonoid fauna is domina- ted by the genus Virgatosphinctes while Micra° canthoceras, Aulacosphinctes etc. are relatively scarce. Further zonation on the basis of the Vir- gatosphinctes evolutionary succession is presently in progress. In contrast, in Eastern Kachchh, particularly west of the Kukuma-Hazapar highway, so far no ammonoids have been collected from any part of the shaly Upper Member of the Ka- trol Formation, and instead rare Virgatosphinctes have been collected from two levels of the lower part of the basal Member (Umia Member) of the

330

Umia Formation (about 8 m above the base of Katrol/Umia Formation boundary). This exempli- fies well the diachronous nature of the concerned lithostratigraphic units. The youngest of these two/three Virgatosphinctes levels is found associated with several specimens of Aspidoceras cf. taverai CHECA.

HISTORY OF THE JURASSIC/ CRETACEOUS BOUNDARY IN KACHCHH

The Jurassic/Cretaceous boundary in Kachchh for a long t ime has continued to be tentatively pla- ced within the Umia Formation between the green oolitic glauconitic sediments containing the Upper Tithonian Micracanthum Zone ammonoid fauna, and the overlying ammonoid devoid trigo- nid bivalve bearing medium to coarse grained grit ty sandstone. The tentat ive placement was based on the suggestive Berriasian - Valanginian age of the trigonids in view of the same trigonids in the otherwise independently dated Berriasian - Valanginian sediments in South Africa. Krishna (1991) recorded and described the first ever Ber- riasian ammonoid (Argentiniceras loncochensis (STEUR) from the Kachchh sequence. The ammonoid A. loncochensis (STEUR) has been earlier known only from Central and South America in the basal Berriasian. The discovery obviously led to bet ter precision and revision of the Juras- sic/Cretaceous boundary, although only locally in the Lakhapur section wherefrom came the two specimens of A. loncochensis (STEUR) from the upper- most of the three green oolitic glauconitic levels otherwise long known to contain the Upper Tithonian Micracanthum Zone ammonoids since the works of Waagen and Spath. The Juras- sic/Cretaceous boundary thus was lowered down within the green oolitic glauconitic par t instead of overlying it as tentat ively understood pre- viously. However , it was not possible to demarcate this boundary precisely in the other stratigraphic sections of Kachchh spread over a length of over 100 km in the Mainland Kachchh.

THE PRESENT STUDY (Fig. 3)

Our extensive studies of last few years (1987 onwards) as part of a collaborative project under the sponsorship of the Insti tute of Petroleum Ex- ploration (Oil and Natural Gas Commission, In- dia) have resulted in the discovery of Juras- sic/Cretaceous boundary ammonoids in a few additional sections. The taxon Spiticeras cf. ducale (MATHERON) (single specimen) was discovered in the same bed and section which had earlier yielded A. loncochensis (STEUR), while two other im- portant sections in the Ler-Katrol region of East- ern Mainland Kachchh have yielded Aspidoceras cf. taverai CHECA. These two Eastern Mainland Kachchh sections lying respectively South-East and South-West of the village Ler on the Kuku- ma-Hazapar highway have yielded several specimens of Aspidoceras (more than one species in- clusive of microconch and macroconch) in more than one well defined levels within a small thick- ness of 1 m. The section south-east of Ler provi- des the Aspidoceras examples nearly exclusive of any other ammonoid fauna except for indetermi- nate virgatosphinctin/berriasellid fragments. The section southwest of Ler designated as Ler-Ghun- wari section interestingly includes several good specimens of Virgatosphinctes in association with Aspidoceras in the lowest of these Aspidoceras bearing levels. The Spiticeras cf. ducale (MATHE- RON) has been already known from the Indian Himalaya and a few South European localities particularly South-East France. In view of the ammonoids associated with Spiticeras cf. ducale (MATHERON) in South-East France, it has been assigned to the basal Berriasian with possible ex- tension up to Upper Berriasian. On the other hand Aspidoceras cf. taverai CHECA has been created and described recently from the basal Berriasian sediments of Subbetic Spain (Checa 1985 ; Checa et al. 1986). The Aspidoceras in par- ticular and aspidoceratids in general are a Medi- terranean stock with near continuous record from the Lower Kimmeridgian to Lower Berriasian in the Mediterranean province (Arkell 1956). The aspidoceratids have been studied in detail recently in Spain (Checa 1985 ; Checa et al. 1986) for

PLATE 1

Fig. 1 -Aspidoceras cf. taverai CHECA, Macroconch, 11545, septate, Bed 32, Unnamed zone, Basal Berriasian, South-East of Ler. a, vue latdrale (x 1) ; b, vue ventrale (x 1). Macroconque.

Fig. 2 - Aspidoceras cf. taverai CHECA, Macroconch, 11546, septate, Bed 33, Unnamed zone, Basal Berriasian, South-East of Ler. a, vue latdrale (x 1) ; b, vue ventrale (x 1). Macroconque.

Fig. 3 - Spiticeras cf. ducale (MATHERON), Macroconch, 10001, septate, Bed 28, Unnamed zone (equivalent) to west Tethyan Jacobi Zone), two km. North-East of Lakhapur (x 45). Macroconque, rue latdrale.

P1. 1 Geob io s J . K r i s h n a , D.B, P a t h a k & B. P a n d e y M.N. n ° 17

' ~ Z = = = ~ - - ~ u ~ % - ~ ~ ' ~ . ~ , ~ . . . . . . . ~ •

,~t-----:-~ ~i~_ ~ .

3

la

1L

332

their phylogenetic evolution. On the other hand the genus Aspidoceras has been found restricted (through several examples) mostly to the Upper Kjmmeridgian in the Indian subcontinent as a whole. Very few additional levels have been found with very rare aspidoceratids of the Titho- nian in Himalaya and Pakistan (Spath 1927-33). It is emphasized that the Aspidoceras occurrence in the Indian subcontinent has been only episodic and rare in comparison to their continuous record in the Mediterranean province. Moreover the aspidoceratids, whenever present in an Indo-East- African assemblage, always constitute only a mi- nor element of the total ammonoid fauna, which otherwise consists mainly of elements geographi- cally restricted to the Indo-East-African faunal province. On the basis of the basal Berriasian age of A. cf. taverai CHECA in the Subbetic Spain, the youngest level of the 1 m thick stratigraphic in- terval in the above mentioned two sections of the Eastern Mainland Kachchh is also assigned to basal Berriasian, while the immediately under- lying sediments with Virgatosphinctes are considered to mark the Upper Tithonian. Thus, it is now possible to demarcate the Jurassic]Creta- ceous boundary precisely for the first time in Kachchh in many sections at least over one hundred km apart.

F A U N A L E X P A N S I O N A N D M I G R A T I O N

It is interpreted here that the episodic presence of the Aspidoceras in the Indian subcontinent is by way of faunal expansion during phases of eustatic rise around the eustatic maxima which allowed the expansion of these relatively warm water ammonoid elements found near equatorial low la- titude regions to relatively cooler regions of the relatively high latitudes on the southern margin of the Tethys like Western India. It may be noticed that Krishna in his many earlier publications has advocated intercommunication and exchange of shallow marine fauna between West India - East Africa on one hand and South/Central Ame- rica on the other hand round the East and South African coastal margin only from Upper Titho- nian onwards. This interpretation has been based on the near absence of common ammonoids between these two regions until the start of Upper Tithonian after which there is noticed sudden presence of many South American genera in the Indian subcontinent of the like of Substeuroceras, Corongoceras, Argentiniceras, Grobericeras, Ne- greliceras etc. This shallow marine corridor round the East and South African coastal margin was a precursor of the oceanic separation between the eastern and western components of the Gondwa-

na super plate sometime later during the Creta- ceous. The present records of Spiticeras cf. ducale (MATHERON) and Aspidoceras cf. taverai CHECA clearly mark a distinct faunal expansion event from the near equatorial northern margin of the Tethys towards south and east to western India on the southern margin of the Tethys. However, unlike the West India - South America shallow marine opening only in the Upper Tithonian, there is evidence of ammonoid faunal exchange both ways (although mostly from north to south) between the northern and southern margins of the Tethys during Bajocian, Bathonian, Callo- vian, Oxfordian, Kimmeridgian and Upper Titho- nlan (Cariou & Hantzpergue 1988 ; Cariou et al. 1990 ; Krishna & Cariou 1986, 1990 ; Krishna & Pathak 1989, 1993). It was only during the Lower Tithonian that the Indian ammonoid fauna attai- ned a near endemic character except for the very rare Hybonoticeras and Hildoglochiceras. This can be explained by way of the tectonically in- fluenced gradual rise of the Kachchh basin in the post Oxfordian global phase of sea level rise during the Kimmeridgian and basal Lower Titho- nian which considerably negated the net effect of the gradual eustatic rise. The Upper Tithonian phase of the eustatic rise again allowed the expansion of the Mediterranean ammonoids to the Indian subcontinent. The above interpretations are also supported by the environmental and se- dimentological characteristics of the relevant sediments.

S Y S T E M A T I C D E S C R I P T I O N

The two basal Berriasian ammonoid taxa A. cf. tavarae CHECA and Spiticeras cf. ducale (MATHE- RON) are described.

Family ASPIDOCERATIDAE Zittel, 1895. Sub family ASPIDOCERATINAE Zittel, 1895. Genus Aspidoceras ZITTEL, 1868. Type species Ammonites rogoznicensis ZEUSCH- NER, 1846. ASPIDOCERAS CF. TAVERAI CHECA (MACRO- CONCH) : pl. 1, fig. la, lb, 2a, 2b.

Mater ia l - 3 specimens numbered 11545, 11546, 11547, one each from beds 32, 33 and 34 from South-East of Ler and 4 specimens numbered 12501, 12502, 12503, 12504 from beds 27 and 28 from South-West of Ler, Kachchh India, entirely septate and moderately preserved.

Loca l i ty - South-East of Ler and South-West of Ler, Kachchh, India.

M e a s u r e m e n t s - Fig. 4.

333

Aspidoceras cf. tavarae CHECA

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Sp. No. D U H W H/W% Ti/2 To/2 Remarks about body chamber

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

11545 86 22 41 51 80 5 6 Septate

57 15 27 34 79 -

11546 90 30 40 54 74 7 7 Septate

71 21 30 40 75 - -

12501 112.5 46 46 56 82 5 7 Septate

80 30 34 43.5 78 - -

12502 129 47.5 56 69 81 5 6 Septate

95 30.5 41.5 52 78.8 -

12503 86 28 40 51.5 77.6 7 8 Septate

80 25 36 47.5 75.7 6 7

66 23 31 42 73.8 5 7

F i g u r e 4 - M e a s u r e m e n t s o f t h e two s p e c i e s d e s c r i b e d , a b - b r e v i a t i o n s u s e d a r e a s fo l lows: D = D i a m e t e r ; U = U m b i l i c u s ; H = H e i g h t ; W = W i d t h . T i /2 = N u m b e r of i n n e r t u b e r c l e s p e r h a l f w h o r l ; To/2 = N u m b e r of o u t e r t u b e r c l e s p e r h a l f w h o r l . D i m e n s i o n s d e s esp~ces avec a b b r d v i a t i o n s . D = D i a m b - tre ; U = O m b i l i c ; H = H a u - t e u r ; W = E p a i s s e u r . T i / 2 = N o m b r e d e t u b e r c u l e s i n t e r n e s T o ~ 2 = N o m b r e de t u b e r c u l e s ex te rnes .

Spiticeras cf. ducale (MATHERON)

I0001 73 31 25 - - Septate

D e s c r i p t i o n - Size moderate (86 to 129 mm), entirely septate, depressed, moderately evolute, um- bilicus somewhat wide, umbilical wall high and vertical, umbilical shoulder curved to nearly rounded, laterals slightly convex, ventrolateral shoulder rounded, ventre broad and rounded.

Whor l S e c t i o n - Somewhat elliptical and depressed.

O r n a m e n t a t i o n - Shell almost smooth, 2 rows of prominent and distinct tubercles, inner row at umbilical shoulder about 5 to 7 per half whorl, outer row at the middle of the laterals, larger and coarser, widely spaced, about 6 to 7 per half whorl, size and spacing of tubercles increasing with diameter.

Sut u r e - Poorly preserved external saddle high, broad with 2 secondary saddles of unequal sizes and a small secondary lobe, first lateral lobe deep, broad with 3 secondary lobes and 2 saddles.

R e m a r k s - The present examples resemble close- ly Aspidoceras taverai CHECA in shell morphology. volution, whorl section and ornamentation. However, it has not been synonymised with the Spanish species due to the inavailability of com-

parable material, possibilites of which are being explored.

G e o g r a p h i c D i s t r i b u t i o n - The taxon has been recorded for the first time from the Ler-Katrol (South East and South West of Ler), Kachchh, India, while A. taverai CHECA is known so far only from Spain.

Stra t igraph ic Di s tr ibut ion - Unnamed Zone, Basal Berriasian, equivalent of the Tethyan Jaco- bi Zone.

Family OLCOSTEPHANIDAE Haug, 1910. Sub family SPITICERATINAE Spath, 1924. Genus Spiticeras (Negreliceras) DJANELIDZE, 1922. Type Species Ammonites negreli MATHERON, 1880, SD ROMAN, 1838.

SPITICERAS CF. DUCALE (MATHERON) (MACRO- CONCH)" pl. 1, fig. 3.

Materia l - Single fragmentary specimen numbered 10001 from bed 28, Lakhapur section, Kachchh India, entirely septate, moderately preserved.

Loca l i ty - 2 km north of Lakhapur, Western Kachchh, India.

334

M e a s u r e m e n t s - Fig. 4.

D e s c r i p t i o n - Size m o d e r a t e (72 mm), en t i re ly sep ta t e , h igh ly evolute , umbi l i cus s o m e w h a t wide, umbi l ica l wal l gen t ly sloping, umbil ical shou lde r cu rved to n e a r l y rounded , l a t e ra l s nea r - ly f lat , v e n t r o l a t e r a l shou lde r rounded , v e n t r e ar- ched.

W h o r l S e c t i o n - H igh ly compressed .

O r n a m e n t a t i o n - Shel l h igh ly compres sed wi- t h o u t l a t e r a l tuberc les , i n n e r h a l f of t he whor ls w i t h b lun t d i s t a n t p r i m a r y bu l l a t e bulges, f ine a n d close p r o r s i r a d i a t e fa in t secondar ies on the ou te r h a l f of the whor l s r a d i a t i n g f rom the pri- m a r y bu l l a te bulges , con t inuous across the peri- phe ry , p ro jec t ing fo rward on the ven t re , abou t 4 to 5 secondar ies pe r each bu l l a t e bulge.

S u t u r e - Poor ly p rese rved .

R e m a r k s - A m o n g the Kachchh species the pre- sen t t axon is found c o m p a r a b l e and closest to Umiaites minor SPATH in morphology, bu l la te bu lges a n d o r n a m e n t a t i o n , bu t for i ts n a r r o w e r a n d m o r e c o m p r e s s e d whor l sect ion. The p r e sen t species s t rong ly r e s e m b l e s Spiticeras ducale (MA- THERON) in morphology , o r n a m e n t a t i o n , volut ion a n d whor l sect ion. Due to i t s record he re only in a s ingle s e p t a t e f r a g m e n t e d spec imen it is for the p r e s e n t not s y n o n y m i s e d w i th t he F r e n c h species.

G e o g r a p h i c D i s t r i b u t i o n - I t is the f i rs t record of the species f rom Kachchh , India .

S t r a t i g r a p h i c D i s t r i b u t i o n - U n n a m e d Zone equ iva l en t of the Wes t T e t h y a n Jacobi Zone.

C O N C L U S I O N

The p r e s e n t f ind of Spiticeras cf. ducale (MATHE- RON) a t L a k h a p u r a n d Aspidoceras cf. tavarae CHECA a t L e r in sec t ions abou t 100 k m a p a r t p rec ise ly d e m a r c a t e the J u r a s s i c / C r e t a c e o u s b o u n d a r y w i t h i n the M a i n l a n d Kachchh. In addi- t ion A. cf. tavarai CHECA c o m m o n be tween K a c h c h h and Spa in , for the f i rs t t i m e also provi- des long d i s t ance cor re la t ion a t the Ju ras s i c /Cre - t aceous b o u n d a r y b e t w e e n K a c h c h h (of the Indo- E a s t Af r ican province) on the S o u t h e r n m a r g i n of the T e t h y s a n d S p a i n (of the M e d i t e r r a n e a n province) on the N o r t h e r n m a r g i n of the Te t h ys to t he prec is ion of s ingle a m m o n o i d zone.

A c k n o w l e d g e m e n t - The authors record their thankfulness to the Indian institutions namely Council of Scientific and Industrial Research, Oil and Natural

Gas Commission and Banaras Hindu University for diverse support and facilities received from them.

R E F E R E N C E S

ARKELL W.J. 1956 - Jurassic Geology of the World. Edinburgh and London (Oliver and Boyd).

CARIOU E . • KRISHNA J. 1988 - The Tythyan Rei- neckeiinae of Kachchh and Jaisalmer (West India) : systematic biostatigraphic and biogeographic impli- cations. Palaeontographica A., 203 : 149-170.

CARIOU E., KRISHNA J. & ENAY R. 1990 - Dynamique biog6ographique des ammonites t6thysiennes au callovien inf6rieur et corr61ations stratigraphiques entre les marges indienne et europ6enne. Comptes- rendus de l'Acad4mie des Sciences de Paris, 311, 2 : 373-379.

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K R I S H N A J., P A T H A K D.B. & P A N D E Y B. Department of Geology

Banaras Hindu University Varanasi 221 005, India

New Ammonoid evidence for theJurassic/Cretaceous boundary in Kachchh Western India, and long...

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