Ammonite Taxa Research Articles

UPPER TRIASSIC (NORIAN) CEPHALOPODS FROM THE EKRASAR FORMATION (SHEMSHAK GROUP) OF NORTHERN ALBORZ, IRAN

The following ammonoid and nautiloid taxa are described for the first time from the Upper Triassic succession (Ekrasar Formation, Shemshak Group) of northern Alborz, Iran: Arcestes sp., Arcestes ( Pararcestes ?) sp., Thisbites cf. agricolae Mojsisovics, Stikinoceras cf. kerri Mc Learn, Giesbachites sp., Griesbachites cf. pseudomedleyanus Diener, Griesbachites cf. himalayanus Wang & He, and Proclydonautilus ? sp. Palaeobiogeographically, the studied ammonoids are Tethyan in character, and stratigraphically attributed to the lower Lower Norian ( Guembelites jandianus Zone, possibly also Malayites paulckei Zone). The biostratigraphic data of this study demonstrate the diachronous base of the Shemshak Group: it is older in the northern Alborz (lower Lower Norian), but younger in Central Iran and probably also in the southern Alborz (Middle Norian).

Lower Cretaceous (Berriasian-Aptian) biostratigraphy of the Neuquén Basin

Abstract The Berriasian-Aptian succession in the Neuquén Basin is mainly marine in the lower part and non-marine in the upper portion. A detailed ammonite zonation is presented for the Berriasian-?Early Barremian interval. While some ammonite taxa are endemic, others are widely distributed and there are several levels where correlation can be suggested with the ‘standard’ stages and zones of the Tethyan Mediterranean area. Several nannofossil bioevents are recognized, and these provide evidence for correlation with Tethyan areas. Correlations suggested by both groups are reasonably consistent. Berriasian-Aptian palynomorphs include both terrestrial and marine forms. Several terrestrial assemblages can be recognized, but the marine forms are mainly long-ranging taxa, especially in the Agrio Formation.

The Vöhrum section (northwest Germany) and the Aptian/Albian boundary

Prior to 1947, the Aptian/Albian boundary was placed at the base of the Nolaniceras nolani ammonite Zone. From (Trav. Lab. Géol. Fac. Sci. 26 (1947) 17), until (Cret. Res. 20 (1999) 609), the base of the Albian stage has been taken at the first appearance of the ammonite Leymeriella ( Proleymeriella) schrammeni, a species known only from a limited area of northwest Germany. The early succession of Leymeriella and its relationship with ammonite taxa from the underlying Hypacanthoplites jacobi ammonite Zone can only be determined in the northwest German sections, all of which are ephemeral clay pits. Thus, the definition of the base of the Albian on these criteria cannot be used in a global context. The positioning of the boundary has been the subject of intense discussion in the last years. After the second International Symposium on Cretaceous Stage Boundaries in 1995 (Bull. Inst. R. Sci. Nat. Belgique, Sci. Terre 66 (1996) 45). (Cret. Res. 20 (1999) 609) lowered the boundary to the base of his Hypacanthoplites rubricosus ammonite Subzone without describing a global boundary stratotype section. (Cret. Res. 21 (2000) 591) raised the boundary to the alleged first occurrence (FO) of Leymeriella tardefurcata in a permanent section, but neither proposals can be accepted globally (Cret. Res. 23 (2002) 1). (Cret. Res. 22 (2001) 677) supported by (Cret. Res. 23 (2002) 1), suggested a radical solution by raising the boundary to the base of the geographically widespread Lyelliceras lyelli ammonite Subzone, currently the base of the Middle Albian. In order to document accurately the classical northwest German succession of the Aptian/Albian boundary, a detailed multidisciplinary study has been made of a new section at Vöhrum (clay pit no. 4) with respect to its content of calcareous nannofossils, benthic foraminifera, planktonic foraminifera, ostracods, ammonites, as well as its clay mineralogy, gamma ray signature and tuff geochemistry. The ammonite succession, in particular the Callizoniceras–Leymeriella lineage, is discussed in detail. The FO of Leymeriella ( Proleymeriella) schrammeni anterior, 0.65 m below a tuff horizon near the base of the section is taken as the Aptian/Albian boundary in the classical German sense. Sections in France are discussed and the Leymeriella lineage is reviewed.

Upper Jurassic (Oxfordian) Radiolaria from the Sula Islands (East Indies); their taxonomic, biostratigraphic, chronostratigraphic, and paleobiogeographic significance

Other| July 01, 2002 Upper Jurassic (Oxfordian) Radiolaria from the Sula Islands (East Indies); their taxonomic, biostratigraphic, chronostratigraphic, and paleobiogeographic significance Emile A. Pessagno; Emile A. Pessagno University of Texas at Dallas, Programs in Geosciences, Richardson, TX, United States Search for other works by this author on: GSW Google Scholar Donna Meyerhoff Hull Donna Meyerhoff Hull Search for other works by this author on: GSW Google Scholar Micropaleontology (2002) 48 (3): 229–256. https://doi.org/10.2113/48.3.229 Article history first online: 03 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Emile A. Pessagno, Donna Meyerhoff Hull; Upper Jurassic (Oxfordian) Radiolaria from the Sula Islands (East Indies); their taxonomic, biostratigraphic, chronostratigraphic, and paleobiogeographic significance. Micropaleontology 2002;; 48 (3): 229–256. doi: https://doi.org/10.2113/48.3.229 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search nav search search input Search input auto suggest search filter All ContentBy SocietyMicropaleontology Search Advanced Search Abstract This report deals with the Upper Jurassic (lower and middle Oxfordian) Radiolaria of the Sula Islands, Indonesia. The radiolarian assemblage, though abundant and extremely well preserved, is poorly diversified and includes approximately fifty species level taxa. The presence of common Praeparvicingula and rare pantanelliids within the faunal assemblage in association with Austral ammonites suggests that the Sula Islands were situated in the Northern Austral Province (>30 degrees south) during the Oxfordian. This paleolatitude is in keeping with the Gondwanaland origin proposed by some workers. The Sula Island middle Oxfordian assemblage is strikingly similar to that described from the Galice Formation (Smith River subterrane, Klamath Mountains, North America). Some faunal elements described from the Sula Island assemblage are characteristic of the Southern Hemisphere and are only known elsewhere from New Zealand (Aita and Mackie 1992). Three radiolarian taxa were originally described from the Galice Formation in the Northern Hemisphere. No ammonite taxa are in common between the Sula Islands and the Galice Formation. This content is PDF only. Please click on the PDF icon to access. You do not currently have access to this article.

The Middle Cenomanian basal series of Planinica, Western Serbia

Sedimentary rocks of the Upper Cretaceous basal series found at the village of Planinica, Western Serbia, are composed of thick coarse clastics and beds and intercalations of medium- to fine-grained clastics. The series lies transgressively over Jurassic serpentinite and peridotite, and under Upper Miocene marlstone and marly limestone. Sedimentary, petrographic, paleontological, and biostratigraphic characteristics of the basal series are described and its lithological members and their structural features are identified. From medium-grained sandy matrix in thick coarse clastics, two ammonite taxa, four brachiopod taxa (including the new taxa Orbirhynchia oweni and "Terebratula" n. gen. et sp.), and eleven echinoid taxa are described. The brachiopod species Kingena concinna Owen is used in dating the basal series as Middle Cenomanian, whereas limestone fragments in coarse clastics correspond to the Late Albian and Early Cenomanian.

Paleogeographic Implications of High Latitude and Middle Latitude Affinities of the Ammonoid Uraloceras

The ammonoid genus Uraloceras characterized a Lower Permian Boreal paleogeographic realm. Reported Lower Permian Pangaean uraloceras occurrences have a Boreal or high-latitude distribution. Additional Lower Permian occurrences in Alaska, dominated by Boreal species, are compatible with and reinforce the Boreal distribution of the genus. In contrast, a new Uraloceras species from Nevada and from the Yukon, as well as representatives of the genus form Nei Monggol, inhabited regions of lower latitudes. The latter ammonoid faunas, geographically and paleoecologically transitional between boreal and equatorial realms, include the genus Uraloceras as well as abundant other ammonoid taxa and representatives of equatorial perinitid ammonoids. The lower assemblage of Wrangellia terrane in eastern Alaska, consisting of the Lower Permian Mankomen Group (Slana Spur and Eagle Creek formations), contains abundant Uraloceras and Paragastrioceras of high-latitude affinities. Published paleomagnetic data indicate that the Nikolai Greenstone is of equatorial origin, with paleolatitudes 10 to 17{degree}. The Nikolai Greenstone seems to have a far-traveled history incompatible with ammonoid evidence suggesting cool-water setting on the Pangaean continental shelf. A reinterpretation for the origin of Wrangellia or its magnetic signature may be in order. Alternative hypotheses suggest that the Eagle Creek Uraloceras-Paragastrioceras Boreal fauna was scraped off the craton atmore » higher latitudes (possible 30-45{degree}) and carried with Wrangellia to its present location.« less