Upper Tithonian Assemblages of Different Faunal Provinces

The paleobiogeographic history of Mesozoic ammonites is marked by the repeated alternation of high degrees of provincialism and cosmopolitanism. The peak of ammonite provincialism occurred during the Late Jurassic and Early Cretaceous (Gordon, 1976). Different names were given for the Upper Jurassic stages in different regions because of this high endemism, i.e., Tithonian in the Tethyan and Indo-

Shaly facies

Calcareous facies Sandstone facies i-'Iotrigonia v-sripta I. beyschlagi Ammonite bands

Shaly facies

Dominantly sandy facies

Sand/Shale facies t t Í

Calcareous facies Sandstone facies

Basalt

Shale Oolite

Medium Sandstone Coarse Sandstone

Fig. 17.2 Stratigraphic section showing the position of the Late Tithonian ammonites in Kutch (vertical thickness not to scale).

i-'Iotrigonia v-sripta I. beyschlagi Ammonite bands

Pacific realms, Portlandian in southern England and Paris, and Volgian in Russia. Even within provinces, subprovinces can still be recognized, e.g., in the Mediterranean (see Cecca, 1999).

Because of the endemism of Tithonian ammonites, interprovincial correlation is a challenge and forms the focus of recent paleobiogeographic research (see references below). This has greatly improved our understanding of Tithonian ammonites, their paleobiogeography, oceanographic barriers, and migrational routes. Paleobiogeographic terminology is still in a state of flux and suffers from nomen-clatural chaos because of the subjectivity involved (see for details Westermann, 2000a, b; Cecca and Westermann, 2003) and inherent complexity of the paleobio-geographical patterns (Dommergues, 2005, personal communication). We here try to follow the paleobiogeographic classification used by the leading workers (Riccardi, 1991; Enay and Cariou, 1997, 1999; Cecca, 1999, 2000; Zakharov and Rogov, 2003) of Tithonian ammonites and include the standardized terminology as suggested by Westermann (2000a, b; 2005, personal communication) and Cecca and Westermann (2003) within parentheses. Following is a discussion of recent research results on the occurrences of Late Tithonian genera ("leiostracans" excluded) in different non-Boreal provinces/regions. A summary of results is presented in Table 17.1.

Table 17.1 List of Late Tithonian ammonite genera in different non-Boreal provinces/realms. x = present; * = genus survived the Jurassic-Cretaceous boundary.

IndoMadagascar

Mediterranean

Andean

Caribbean

Austral (Indo-Pacific)

Anavirgatites

x

-

-

-

-

Andalusphinctes

-

x

-

-

-

Aspidoceras

x

x

x

x

x

Aulacosphinctes

x

x

x

x

x

Aulacosphinctoides

x

-

-

-

x

Baeticoceras

-

x

-

-

-

Berriasella*

x

x

x

x

x

Blanfordiceras

x

-

x

-

x

Bochianites

-

x

-

x

-

Corongoceras

x

x

x

x

x

Curdubiceras

-

x

-

-

-

Dalmasiceras

-

x

-

-

-

Danubisphinctes

-

x

-

-

-

Dickersonia

-

-

x

x

-

Djurjuriceras

x

x

x

-

-

Durangites

x

x

-

x

-

Haploceras

x

x

-

x

-

Hemisimoceras

x

x

-

-

-

Hemispiticeras

-

-

x

-

-

Hildoglochiceras

x

-

-

-

-

Himalayites

x

x

x

-

x

Kossmatia

-

x

-

x

x

Lamencia

-

x

-

-

-

Lytogyroceras

-

x

-

-

-

Lytohoplites'

x

-

x

x

x

Malbosiceras

-

x

-

-

-

Mazaplites

-

-

-

x

-

Micracanthoceras

x

x

x

x

-

Moravisphinctes

-

x

-

-

-

Nebrodites

x

-

-

-

-

Negreliceras

-

x

x

x

-

Neolissoceras

x

x

-

-

-

Neoperisphinctes

-

x

-

-

-

Oloriziceras

-

x

-

-

-

Oxylenticeras

-

x

-

-

-

Paraulacosphinctes

-

x

-

-

-

Paraboliceras

-

-

-

-

x

Parapalliceras

-

x

-

-

-

Table 17.1 (continued)

Parabilliceratoides

-

-

-

-

x

Parodontoceras

-

-

x

x

-

Pectinatites

-

-

x

-

-

Phanerostephanus

x

-

-

-

-

Proniceras

x

x

-

-

x

Protacanthodiscus

x

x

x

-

-

Protancyloceras

x

-

-

-

-

Pseudoargentiniceras

-

x

-

-

-

Pseudodiscosphinctes

-

x

-

-

-

Pseudoinvoluticeras

x

-

x

-

-

Pseudolissoceras

-

-

x

x

x

Salinites

-

-

-

x

-

Schaiveria

-

x

-

-

-

Simoceras

-

-

x

-

-

Simolytoceras

-

x

-

-

-

Simosphinctes

-

x

-

-

-

Simplisphinctes

-

x

-

-

-

Spiticeras'

x

-

x

-

x

Suarites

-

-

-

x

-

Subalpinites'

-

x

-

-

-

Subdichotomoceras

x

x

-

-

x

Substeueroceras

-

x

x

x

x

Substreblites*

-

x

-

-

-

Subthurmannia*

-

x

-

-

-

Tithopeltoceras

x

x

-

-

-

Umiaites

x

-

-

-

-

Vinalesites

-

-

x

x

-

Virgatosphinctes

x

-

x

-

x

Wichmanniceras

-

-

x

-

-

Windhauseniceras

-

-

x

-

-

Zittelia

-

x

-

-

-

The Indo-Madagascan Province was well established since the Middle Jurassic (Arkell, 1956). During the Tithonian, the most fossiliferous regions are Kutch (Spath, 1927-1933), Baluchistan (Fatmi, 1972; Fatmi and Zeiss, 1994), and Madagascar (Collignon, 1960). The other areas included Somalia and Tanzania, from which only a few genera have been reported (see Enay and Cariou, 1997; Cecca, 1999). The Himalayan faunas, which show "sub-austral" affinity (Indo-Pacific of Westermann, 2000a, b) (see Enay and Cariou, 1997), are not included in this province. Previously it was believed (e.g., Cecca, 1999) that the Indo-Madagascan Late Tithonian ammonites were less diverse. The recent discoveries of several new ammonite genera from Kutch now reveal that this province is the second most diverse (see Table 17.1). Kutch, northwest Pakistan, and Madagascar together include 27 genera (Table 17.2) under four families: Olcostephanidae, Neocomitidae, Himalayitidae, and Aspidoceratidae.

Like other provinces, the Indo-Madagascan Province initially also shows well-marked endemism. The Early Tithonian is characterized mainly by many species of

Table 17.2 Late Tithonian ammonite genera present in three different regions ofthe Indo-Madagascan Province. Symbols are same as in Table 1.

Kutch

Madagascar

NW Pakistan

Anavirgatites

-

x

-

Aspidoceras

-

-

x

Aulacosphinctes

x

x

x

Aulacosphinctoid

x

x

x

Berriasella*

-

x

-

Blandfordiceras

-

-

x

Corongoceras

x

x

-

Djurdjuriceras

-

x

-

Durangites

x

-

-

Haploceras*

x

-

x

Hemisimoceras

-

x

-

Hildoglochiceras

-

x

x

Himalayites

x

x

x

Lytohoplites*

-

x

-

Micracanthoceras

x

x

x

Nebrodites

x

-

-

Neolissoceras'

-

x

x

Phanerostephanus

-

x

-

Proniceras

-

x

x

Protacanthodiscus

-

-

x

Protancyloceras*

-

x

-

Spiticeras'

-

x

x

Subdichotomoceras

-

-

x

Tithopeltoceras

x

-

-

Umiaites

x

-

-

Virgatosphinctes

x

x

x

Virgatosphinctes (see Spath, 1927-1933). Endemism is so pronounced that even some leiostracans (e.g., Pterolytoceras) were exclusive to this province and Spiti Himalayas (Shome and Roy, 2006). Endemism became somewhat blurred, however, due to the invasion of many cosmopolitan forms during the Late Tithonian marine transgression (Haq et al., 1987; Hallam, 1992). The subfamily Virgatosphinctinae continued, but younger forms included a new stock having large body size (authors' personal observation).

In the Mediterranean Province, Late Tithonian ammonite assemblages are known only from a few areas in southern Spain, Italy, and France (see Cecca, 1999). Like Kutch, this province also experienced considerable reduction of the habitat due to regression, especially in the southern European platform and epicontinental basins (Fourcade et al., 1991; Cecca, 1999). However, southern Spain is highly fossiliferous and includes 33 genera (see Tavera, 1985). This is also the highest level of ammonite diversity in any region of the world during the Late Tithonian.

The Mediterranean assemblage was dominated by genera belonging to mainly three families. "Perisphinctidae" showed renewed diversity (Tavera, 1985) and included 11 genera. The "Berriasellidae" were also equally diverse with 11 genera (Tavera, 1985). Additionally, Simoceratidae, which is typical of the Mediterranean facies during the Early Tithonian, persisted. Olcostephanidae and Opellidae were represented by sparse genera.

Leanza (1981) and Riccardi (1991) have analyzed the Upper Tithonian ammonite assemblages of the Andean Province. Three main fossiliferous areas are northwestern South America, central-western South America, and southern South America. Their faunas are fairly homogeneous, but the similarity coefficient index varies from place to place (Riccardi, 1991). Each area includes Andean endemic genera which help in establishing intraprovincial correlation. Altogether, 25 genera have been recognized in this province. Assemblages in southern South America are slightly distinct in the sense that they show closer affinity with "Austral" New Zealand and "Ethiopean" (=Indo-Madagascan, described here) Madagascar. Even at the species level, this affinity is evident especially during the Late Tithonian (see below).

The Caribbean Province was first proposed by Westermann (1984) and Taylor et al. (1984) who used the term for the Middle Jurassic assemblages. On the basis of ammonite assemblages, Myczyiisky and Pszczolkowski (1994) suggested that this province was also well established during Late Jurassic and Early Cretaceous times. The province includes faunas of Cuba and Mexico.

The Tithonian ammonites of Cuba are moderately diverse. Myczynsky and Pszczolkowski (1994) reported 13 genera from eight families. They are dominated by the cosmopolitan forms and some endemic taxa at the species level (see Cecca, 1999). The assemblages show mixed provincial characters dominated by Mediterranean faunas. However, geographically wide ranging genera like Corongoceras, Himalayites, Durangites, and Aulacosphinctes Uhlig, which are now described from Kutch (Shome et al., 2004), are also present. Myczynsky (1989) mentioned many species of Virgatosphinctes including V. denseplicatus, which is a typical Indo-Madagascan form. However, Cecca (1999), and previously Enay (1972) and Callomon (in Hillebrandt et al., 1992), doubted the generic affiliation of this Cuban form.

In Mexico, ammonite assemblages show a fair degree of homogeneity (Imlay, 1939; Verma and Westermann, 1973; Oloriz et al., 1999) with the Cuban taxa. Verma and Westermann (1973) described altogether nine genera, including Kossmatia Uhlig, a genus not found in Cuba but typical of the "Austral Province" (Indo-Pacific Realm) (Enay and Cariou, 1997).

The Austral Realm (Indo-Pacific) covers east peri-Gondwanan areas including Antarctica (Thomson, 1980, 1982; Riccardi, 1991), New Zealand (Stevens, 1997), and Papua New Guinea (Indonesia) (Riccardi, 1991) and extends up to the Himalayas (see Enay and Cariou, 1997; Westermann, 2000b). This is a less diverse region as far as the Late Tithonian ammonites (14 genera) are concerned. Other than the Himalayas, Tithonian ammonites are poorly known from the rest of the areas. Recently, Enay and Cariou (1997, 1999) reported seven genera under three families, i.e., Olcostephanidae, Neocomitidae, and Himalayitidae from Spiti in India and the Nepal Himalayas. They mentioned that Himalayan forms are characterized by endemic taxa, which show some degree of Austral affinity. The family Neocomitidae dominates the assemblage and includes three genera, Berriasella Uhlig, Blanfordiceras Cossmann, and Corongoceras.

Panboreal Superrealm ammonites are high latitude faunas living in the areas north of 45-50° N (Westermann, 2000a; Zakharov and Rogov, 2003). This belt was well established since the Middle Jurassic and correlation, therefore, between the Volgian and Tithonian is still a problem. However, during the Late Jurassic, Boreal-Tethyan ammonites show latitudinal shifts time and again, and thermally anomalous assemblages have been found in many Boreal areas indicating a northward migration of several Tethyan genera (see Zakharov and Rogov, 2003; and references therein).

The composition of Boreal ammonite assemblages during the latest Jurassic differs greatly from the contemporary Kutch faunas, which are essentially Tethyan in affinity. We follow Zakharov and Rogov (2003) in dividing the Panboreal Superrealm into four realms, Boreal West Europe (Northwestern Europe), Boreal East Europe (Volga Basin and Russian Platform), Boreal Pacific (Chukotka-Canadian Province and Primorje), and Boreal Eastern Pacific (British Columbia and California). We present the boreal data in a later section, to show diversity and extinction intensity. The genera characteristic of these regions are listed in Table 17.3 (Arkell, 1956; Arkell et al., 1957; Wright et al., 1996; Cecca, 1999; and Zakharov and Rogov, 2003; and references therein).

Was this article helpful?

0 0

Post a comment