Ammonite Succession Research Articles

MID-CARBONIFEROUS AMMONOID BIOSTRATIGRAPHY, SOUTHERN NYE COUNTY, NEVADA: IMPLICATIONS OF THE FIRST NORTH AMERICANHOMOCERAS

Abstract The Scotty Wash Formation on the Nevada Test Site (NTS), southern Nye County, Nevada has produced the first North American representatives of the globally significant index ammonoids Homoceras s.s. and Isohomoceras s.s. and contains the only ammonoid succession across an uninterrupted mid-Carboniferous boundary sequence known in North America. Four ammonoid assemblages can be recognized at NTS that are homotaxial with the reference successions for the middle and upper Arnsbergian (E2) and Chokierian (H1) Stages, Namurian Series, in western Europe, and their equivalents worldwide. The upper Mississippian (Chesterian) portions of the NTS sections yield assemblages referable to a Eumorphoceras girtyi Ammonoid Biozone, representing the middle Arnsbergian Stage (E2b), followed by a Delepinoceras thalassoide Ammonoid Biozone, equivalent to the upper Arnsbergian Stage (E2c). The latter ammonoid biozone also occurs in the Imo and Rhoda Creek Formations of Arkansas and Oklahoma, requiring reassignment of ...

Early Emsian ammonoids from the eastern Anti-Atlas (Morocco) and their succession

From 20 sections in the Tafilalt (eastern Anti-Atlas, Morocco), 13 early Emsian ammonoid species of the families Mimosphinctidae, Mimoceratidae, Teicherticeratidae, Mimagoniatitidae, and Auguritidae have been discovered. The following taxa are newly described:Chebbites n. gen.,Chebbites reisdorfi n. sp.,Chebbites undosus n. sp.,Gracilites maghribensis n. sp., Palaeogoniatitinae n. subfam.,Irdanites n. gen.,Irdanites kaufmanni n. sp.,Irdanites korni n. sp.,Lenzites gesinae n. sp.,Weyeroceras n. gen.,Weyeroceras angustus n. sp. In addition, specimens ofErbenoceras solitarium, Metabactrites formosus, andRuanites obliquecostatus are described and figured from Morocco for the first time. The ammonoid generaConvoluticeras, Erbenoceras, Mimosphinctes, Palaeogoniatites, Talenticeras, andTeicherticeras and the families Mimosphinctidae, Mimoceratidae, Teicherticeratidae, and Mimagoniatitidae are reviewed.Taskanites andLaganites are regarded as subjective junior synonyms ofConvoluticeras. In Morocco, the early Emsian ammonoid succession differs from what can be expected from a phylogenetic point of view. Several species belonging to different families of various phylogenetic stages appear within one stratigraphical unit. In contrast to previous opinions however,Gyroceratites laevis appears stratigraphically earlier thanMimagoniatites fecundus, which agrees in this case with the phylogenetic succession of the taxa. Stratigraphical data from early Emsian ammonoids are still insufficient as basis for a more detailed stratigraphical subdivision of the early Emsian.

The Earliest Jurassic psiloceratids in the Eastern Tethyan Himalaya, South Tibet

Recent collection of ammonites in the Germig area, South Tibet, allows the establishment of an Early to Middle Hettangian psiloceratids succession, documenting the Planorbis and Liasicus Zones. Five ammonite assemblages, ranging from the Planorbis to Laqueus Subzone have been recognized. They are the Neophyllites sp.– Psiloceras ex. gr. pacificum ass., the Psiloceras cf. polymorphum– Psiloceras cf. pacificum ass., Caloceras crassicostatum– Psiloceras distinctum ass., Kammerkarites cf. haploptychus ass. and Discamphiceras silberlingi ass. The Lower and Middle Hettangian ammonite succession together with the Rhaetian Choristoceras cf. marshi (Hauer) offers a basis for the study of the Triassic and Jurassic boundary section, only recently known of in the Eastern Tethyan Himalaya.

A hiatus of 8 my durationin the Middle Jurassic with ammonite succession in Tethyan Himalaya (South Tibet)

Abstract Middle Jurassic ammonites collected in situ from the Lanongla sections, Lanongla, South Tibet allow the precise dating of the ferruginous Oolite beds and the underlying limestone beds in this area. A large hiatus of 8 million-year duration in South Tibet is well documented by the ammonite succession. Revision of sea-level changes curve in Tibet during the Middle Jurassic is proposed; the high sea-level stands below and above the disconformity are dated as Humphriesianum Zone (late Early Bajocian) and Orbis Zone (early Late Bathonian), respectively.

The early and middle Triassic ammonoid succession of the Himalayas in western and central Nepal Part 5. Systematic studies of the early Ansian

The early and middle Triassic ammonoid succession of the Himalayas in western and central Nepal Part 5. Systematic studies of the early Ansian

The early and middle Triassic ammonoid succession of the Himalayas in western and central Nepal

The early and middle Triassic ammonoid succession of the Himalayas in western and central Nepal

Observations on the lithostratigraphy and ammonite succession of the Aptian (Lower Cretaceous) Lower Greensand of Chale Bay, Isle of Wight, UK

A revised lithostratigraphy is given for parts of the Atherfield Clay and Ferruginous Sands Formations (Lower-Upper Aptian) of the Lower Greensand Group of the standard section in Chale Bay, Isle of Wight, retaining in essence the classic nomenclature of Fitton. Changes in zonal and subzonal boundaries are proposed on the basis of new collections of ammonites obtainedin situ. The Upper Lobster Beds Member of the Atherfield Clay is detached from the Subzone ofDeshayesites callidiscusand placed in a separate Subzone ofDeshayesites annelidusat the top of the Zone ofD. forbesi. The influx ofMegatyloceras, Cheloniceras, PseudosaynellaandSinzoviaat this level has palaeogeographic implications, pointing to the opening of a marine link with the Paris Basin and confirming the Upper Lobster Beds as a transgressive horizon. The upper part of the Scaphites Beds Member of the Ferruginous Sands, previously included in thedeshayseiZone, is transferred to the Subzone ofDufrenoyia transitoria, at the base of the Zone ofTropaeum(T.)bowerbanki, on the strength of the occurrence therein of species ofTropaeumandDufrenoyia.Tropaeumis not present below thebowerbankiZone as now defined; its primitive ancyloceratoid (hooked) forms such asT. (T.)hillsiihave limited biochronological value, persisting alongside the criocone (spiral) species of thebowerbankiZone and giving rise to a local horizon ofT. (T.)pseudophillsiat the bottom of the Upper Crioceras Beds (basal Upper Aptian). A more precise delimitation of the Walpen Clay & Sands from the Upper Crioceras Beds is made and the junction of these two members of the Ferruginous Sands is reaffirmed as the Lower/Upper Aptian boundary, coinciding with the junction of the Zones ofT. (T.)bowerbankiandEpicheloniceras martiniodes. Bed-by-bed collecting across the boundary shows thatEpichelonicerascan no longer be taken as the prime biostratigraphical marker for the base of the Upper Aptian; greater significance is given to the extinction ofDufrenoyia. The sources of the genusVectisitesand some species ofAmmonitocerasandCaspianites, hitherto fixed only vaguely in the column, are pinpointed in themartinioidesZone. The horizon ofTropaeum(T.)drewiis confirmed as high in thebowerbankiZone (meyendorffiSubzone) and the validity of a ‘drewiZone’ at the base of the German Upper Aptian (=base of Middle Aptian, Kemper, 1995) is questioned. In a review of the Lower/Upper Aptian boundary, it is suggested that the German stratum be called the Horizon ofCicatrites?tenuinodosusand placed tentatively at the top of the Lower Aptian. These and other changes in ammonite nomenclature are explained in the systematic notes.

Le Jurassique supérieur du bassin de la Volga: biostratigraphie des faunes d'ammonites et corrélations avec les zonations standards européennes

The detailed ammonite succession of the Upper Jurassic of the Middle Volga basin is described using six sections including the lectostratotype of the Volgian formation. A new precise biostratigraphic scheme, which comprises 19 ammonite zones, is suggested for the Russian platform. Many biostratigraphic equivalences between the Russian ammonite zonation and both Boreal and sub-Mediterranean provinces are proposed. On the Kimmeridgian Stage, the identification of seven Western European ammonite horizons is an outstanding correlation. The possible correlations between Volgian, Portlandian and Tithonian are discussed. We emphasize the necessity of a new definition of the Jurassic-Cretaceous boundary.

The Early and Middle Triassic ammonoid succession of the Himalayas in Western and Central Nepal Part 3. Late Middle Scythian ammonoids

The Early and Middle Triassic ammonoid succession of the Himalayas in Western and Central Nepal Part 3. Late Middle Scythian ammonoids

The Early and Middle Triassic ammonoid succession of the Himalayas in Western and Central Nepal Part 2. Systematic Studies of the Early Middle Scythian

The Early and Middle Triassic ammonoid succession of the Himalayas in Western and Central Nepal Part 2. Systematic Studies of the Early Middle Scythian

The Anisian ammonoid succession of the Nepal Himalaya

Anisian ammonoid sequences are well developed in central Nepal, north of the Annapurna Range, extending from the Manang district through Puchenpra Ridge, Plateau of lakes, Mesokanto Pass, to the Kali Gandaki Valley. The earliest and most significant faunules are developed in two zones, in the Kaisang, Tangje, and Thorong Members of the upper Gungdang Formation. The older zone is dominated by Grambergia, and also contains species of Ananorites, Tienjunites, Qilianshanites, Pearylansites,and Sturia? with other genera. The upper zone contains over 30 species, with Lenotropites, Beyrichitids, Arctohungarites, Norites, Longobardites, Epiczekanowskits, Stenopopanoceras and Neopopanoceras? These zones overlie a late Scythian faunule with Keyserlingites, Dagnoceras, Prohungrites, Nordophiceras and Svalbardiceras etc, placed in turn above a rich ammonoid faunule with Subcolumbites, Dinarites, Paranoritoides, Eophyllites, Albanites and other genera.
 The Kaisang-Thorong zones are followed by a suite of ammonoids belonging to the Paracrochordiceras Zone; or Aegean Stage, generally regarded in recent years as indicating basal Anisian. Thus the Nepal sequence indicates the presence of a post-Scythian, pre-Aegean stage, here informally named Manasluan, after Mt. Manaslu , which is prominent west of the type section for both stratigraphic and biostratigraphic entities, on the southeast ridge of Mt. Chulu. The Manasluan stage is poorly developed world-wide, but may be represented, in part, by the so-called Lenotropites qinghaiensis faunule of central Qighai, and Neopopanoceras haugi Zone of California and Nevada.
 The Paracrochordiceras Zone of Nepal is represented by two successive faunules with some 20 species in the Phukung Menmber at the top of the Gungdang Formation and in the overlying lower Mukut Group, and includes two species of Paracrochordiceras. The Bithynian Stage follows, with a meagre, Gymnites depauperatus faunule, succeeded by a rich Paradanubites-Holandites-Aristoptychites-Gymnites assemblage of over 30 species. Several of the species are shared with Diener's "Lower Muschelkalk" Ammonoids from the northwest Himalaya, and some of the species are found also in Diener’s "Upper Muschelkalk" Keyserlingites is present at this level, as reported by Diener in his "Lower Muschelkalk" Nepal evidence suggests that this genus, or species very close to this genus, range from the Subcolumbites level in Nepal, i.e. late Scythian, into middle Anisian, or Bithynian. North American authorities have endeavoured to impose a short range for Keyserlingites, as latest Scythian, but this appears to be wrong. Their interpretation of the Scythian-Anisian boundary therefore has to be substantially re-evaluated.
 In the younger Mukut Group of the Annapurna region there is a possibility of having Bulogites and Balatonites, indicating the presence of Pelsonian Stage. Apart from this, Ladinian ammonoids have also been found, encouraging further study. From the Mukut of (northwest Nepal) in west Dolpo, equivalent of Diener's Upper Muschelkalk," or Illyrian Stage, with Paraceratites of the trinodosus format, and Pseudodanubites, Hollandites, Beyrichites, Gangadharites, Bulogites, Ptyshites, Discoptydhites, Monophyllites and other genera have been collected.
 These studies indicate that Anisian of Nepal is moderately well developed, and offer sequences particularly significant for the Scythian-Anisian boundary, and lower Anisian. They also help resolve the long­ standing dispute over the age of Keyserlingites, which has clouded understanding of the Anisian and Scythian for several decades.

Rôle du climat sur les migrationset la composition des peuplements d'ammonites du Valanginien supérieur du bassin vocontien (S-E de la France)

This study concerns the ammonite succession of the Upper Valanginian of the La Charce (Drôme) and Angles (Alpes de Haute-Provence) sections in the Vocontian trough. We have tried to place the ammonite succession against lithological changes interpreted in terms of relative sea level changes after doing system tract analysis in the Vocontian trough and its surrounding platforms. The main result is the migration of mesogean ammonites during the third order lowstand systems tracts and the migration of boreal forms during the transgressive systems tracts. So, these migrations are not only due to easier communications between both realms, in the open sea environment of the Vocontian trough. We think the climate to be one of the most important factor controlling the migrations. According to these results, lowstands (increase of lime content) would be warmer than transgressive tracts (more marly). The climatic factor would also affect the recorded alternancy of ammonite associations between the limestone beds and marly interbeddings.

Taxonomy and correlation of Lower Triassic (Spathian) segminate conodonts from Oman and revision of some species ofNeospathodus

Exceptionally well preserved Lower Triassic conodonts from Oman include an array ofNeospathodusspecies, many of which are new. Those from the upper Lower Triassic, or Spathian, are described in conjunction with a restudy of conodont type material from Chios, Greece, and an assessment of contemporary collections from Pakistan and western North America. The taxonomic scope of three key species from Chios,Neospathodus homeri, N. triangularis, andN. gondolelloides, is revised. Seven new species are described from Oman:N. abruptus, N. brevissimus, N. brochus, N. crassatus, N. curtatus, N. pusillus, andN. symmetricus;and one new species,N. clinatus, is described from Pakistan. The alliedIcriospathodus collinsoniis also described from Oman. The occurrence and range ofNeospathodusspecies are presented in the context of the ammonoid succession in the Spathian of North America. BothN. homeriandN. triangularis, as revised, have shorter ranges and are more age diagnostic than previously thought.Neospathodus gondolelloidesis a distinct taxon, and not synonymous withChiosella timorensis.Five informal faunal divisions are identified based onNeospathodusand allied species. In ascending stratigraphic order, these are typified byIcriospathodus collinsoni, Neospathodus homeri, N. triangularis, N. symmetricus, andN. gondolelloides.Oman collections represent three of these faunas, which occur also in theColumbitesthroughProhungarites/Subcolumbitesammonoid beds of western U.S.A.

Biostratigraphy of the highest Kimmeridgian and Lower Volgian in Poland

In Poland, the ammonite succession in several continuous and expanded sections makes it possible to recognize the Eudoxus and Autissiodorensis Zones in the Upper Kimmeridgian as well as the Klimovi, Sokolovi, Pseudoscythica and Tenuicostata Zones in the Lower Volgian, and to reconstruct an evolutionary lineage leading from Discosphinctoides through the genera Virgataxioceras, Ilowaiskya and Pseudovirgatites to Zaraiskites.. Some interregional stratigraphical correlations are suggested.

Sinemurian (Lower Jurassic)ammonoid biostratigraphy of the Queen Charlotte Islands, Western Canada

The Sinemurian ammonoid succession of the Queen Charlotte Islands is subdivided into, in assending order, the Canadensis Zone, the “Coroniceras”, Arnouldi, Varians, Harbledownense, and Tetraspidoceras assemblages. The Hettangian-Sinemurian boundar is drawn within the Canadensis Zone, at the first appearance of Badouxia columbiae and Metophioceras div. sp. The Sinemurian-Pliensbachian boundary has not yet been satisfactorily defined as the Tetraspidoceras Assemblage contains elements with both Sinemurian and Pliensbachian affinities. Correlation with the northwest European Standard Zonation as well as with the Mediterranean Province and South America is possible but often ambiguous. The present scheme contributes to the development of a Standard ammonite Zonation for North America.

Première zonation par ammonitesdu Jurassique d'Arabie Séoudite, une référence pour la province arabique

The ammonite succession of Saudi Arabia established initially by Arkell (1952), completed by Imlay (1970) and recently refined by Enay & Mangold (1982–1984, 1985) and Enay et al. (1986, 1987a) was constructed largely by reference to the classic zones of Europe. It is now time, therefore, to erect a zonation particular to Saudi Arabia based on its own fauna. The equivalences previously and currently proposed with European faunal succession are somewhat imperfect and uncertain but they give the framework for gauging the zones of the Arabian Province and the reference zones of Submediterranean Europe. The zonal chart is presented as a complete sequence of zones and so does not show the unconformities in the succession nor the lateral distribution of the faunas. The latter are typically those of a shallow platform where the environments are close to the limit of tolerance for ammonites which characterize the Arabian Province. The times of ammonite expansion are: the principal Ermoceras fauna and the Thambites, Tulites, Micromphalites, Pachyerymnoceras and Per. jubailensis faunas. In contrast the Bouleiceras,, Sonniniids, Dhrumaites and Euaspidoceras faunas were more restricted in their distribution. The autochtonous and monotaxonic faunas, often endemic during their diversification phase, all have simplified septa regardless of their general form. Some spread subsequently to North Africa and Europe and/or to the Middle East, the East-African coast, Indian shield and Madagascar where environments were more open. In contrast some rare European forms migrated from time to time via the Southern Tethys, and reduce the provinciality of the Arabian Province. This two-way exchange of faunas makes it possible to correlate albeit imperfectly the zones of the Arabian province, based on index species selected from the most abundant species, with the reference zones of the Submediterranean, albeit imperfectly.

Preliminary remarks on the Hettangian ammonite succession in Queen Charlotte Islands, British Columbia

An essentially continuous Hettangian sequence has been found in Queen Charlotte Islands, British Columbia. Thefaunas present are generally abundant, and diverse but poorly to moderately well preserved. Preliminary study of the ammonoids indicates the presence of genera beginning with a poor Psiloceras fauna at the base and an abundant Badouxia fauna on the Hettangian-Sinemurian boundary. The sequence contains most genera found in the Hettangian faunas of Nevada as well as a few not found there. This section enhances our knowledge of the ranges of Hettangian genera and species in North America.

The Early and Middle Triassic ammonoid succession of the Himalayas in western and central Nepal Part 1. Stratigraphy, classification and Early Scythian ammonoid systematics

The Early and Middle Triassic ammonoid succession of the Himalayas in western and central Nepal Part 1. Stratigraphy, classification and Early Scythian ammonoid systematics

Nouvelles données biostratigraphiques sur les dépots cénomanoturoniens du Nord-Est du fosse de ia Bénoué (Nigéria)

The Upper Cretaceous deposits of the Upper Benue (North-East Nigeria) record regional and local events (sea-level changes, biological successions and tectonic movements) which throw light on the Upper Cenomanian transgression. Evidence of discontinuities and sedimentary assemblages well dated by micropalaeontological data, allows the sedimentary sequence to be interpreted in the context of sequence stratigraphy. The discovery of new ammonite faunas has enabled a more precise definition of the local biostratigraphy and a correlation of this with the standard zonal scheme. In the near future, when they are better known, the ammonite successions recognized in the Upper Benue could enable a retire precise delineation of Cenomanian-Turonian time than that proposed here; this would both complement and help to clarify existing schemes recently proposed for other African areas.

The ammonite succession in the Middle Jurassic of East Greenland

The ammonite sequence in the Middle Jurassic of central East Greenland is the most complete and detailed known in the Arctic so far, and has become a standard of reference for the whole of the Bo real Faunal Province. It is made up of some 37 distinguishable assemblages that characterize a time-ordered succession of discrete faunal horizons. This succession has been pieced together from over 80 recorded sections in Jameson Land lying between Scoresby Sund and Kong Oscars Fjord (70-72°N). It forms the biostratigraphic basis for the regional chronostratigraphy. The faunal assemblages are listed and described by reference to published illustrations in the literature. Faunas 1-23 are of pre-Callovian age and have no elements in common with their contemporaries in the classical regions of Europe. They still cannot be correlated with the European standard pre-Callovian chronozonations. Most of them must be of Bathonian age, although the earliest of them could well be, and probably are, even still Upper Bajocian. The Bathonian-Callovian boundary most probably lies some­where in faunas 24-26, which closely resemble those of the keppleri horizon at the base of the Callovian. Faunas 27-35 span the rest of th􀁋 Lower Callovian, while faunas 36 and 37 are the only evidence of Middle and Upper Callovian. The ammonites from Jameson Land previously described by Spath (I 932) are revised and assigned to their correct horizons. Of 11 new species, only one is formally named: Kepp/erites vardekloeftensis sp. nov., of latest Bathonian age.