CONODONTS OF THE LOWERMOST TRIASSIC OF SPITI, AND NEW ZONATION BASED ON NEOGONDOLELLA SUCCESSIONS

Conodonts from the lowermost Triassic Otoceras woodwardi beds and adjacent strata of Spiti are described and compared with Permian-Triassic (P-T) boundary bed faunas from elsewhere. A new pelagic zonation based on Neogondolella is introduced: the interval characterized by N. carinata-N. taylorae is subdivided into three parts based on successive first appearances of N. meishanensis, N. krystyni Orchard n. sp. and N. discreta Orchard and Krystyn n. sp., the nominal species of three successive zones. The development of these Griesbachian species involves a progressive morphological change in the configuration of the axial part (blade-carina-cusp) of the pectiniform elements. The pelagic conodont zonation is intercalibrated with the parallel zonation based on species of Hindeodus and Isarcicella, and with ammonoid faunas from Spiti, other Himalayan localities, and the Arctic. The meishanensis Zone embraces the parvus Zone and part of the overlying staeschei Zone. Strata containing O. woodwardi in Spiti carry the indices to the staeschei and krystyni zones. The Neogondolella conodont fauna associated with Otoceras differs from that of the latest Permian Changshing Limestone of China, but resembles that from the P-T boundary transition beds at Meishan, where a meishanensis Zone of restricted scope occurs beneath the parvus datum. The faunal change which introduces the characteristic Neogondolella species of the N. carinata-N. taylorae fauna occurs at the base of the P-T boundary transition beds at Meishan, the proposed boundary stratotype. Slightly above this level, the disappearance of most Neogondolella species and the introduction of new Hindeodus species coincides with a change in conodont biofacies rather than an extinction event. In the Spiti sections, the N. carinata-N. taylorae fauna, associated at first with H. parvus (as in Selong, Tibet), persists through the entire Griesbachian. Indices of the three Neogondolella zones are also recognized in the Salt Range and the Canadian Arctic. Four new conodont species are described: Neogondolella discreta, N. kazi, N. krystyni, and N. nassichuki.&nbsp

THE MIDDLE SMITHIAN (EARLY TRIASSIC) AMMONOIDS OF GORNJI BRČELI (SOUTHERN MONTENEGRO)

A rich Early Triassic (Smithian) ammonoid fauna discovered near the village of Gornji Brčeli (southern Montenegro) is unique for the Early Triassic of the western Tethys. The Smithian there is represented by a series of several tens of meters thick brown-red to grey-green marls and clays with intercalated, mica-rich, thin dark grey sandstones, and subordinate occurence of redeposited oolitic limestone. The fossils have been collected as scree material over a few square meters but are considered as contemporaneous since no unnatural association (condensation) was detected. The ammonoid assemblage is represented by 15 species, belonging to the genera Aspenites, Cordillerites, Dieneroceras, Abrekites, Owenites, Pseudaspenites, Pseudosageceras, Truempyceras, Wyomingites, Hanielites, Galfettites, Parahedenstroemia, Lingyunites and Pseudoflemingites, and can, by the presence of Owenites zitteli Smith, be correlated with the late Middle Smithian Nyamalites angustecostatus beds of the southern Tethys, the upper Owenites koeneni beds of South China or the Owenites beds of North America. Taxonomic composition of the ammonoid assemblage shows great similiarity with those of Spiti (India), NW Guangxi (China) and Nevada (USA), but also some with those of Salt Range (Pakistan) and Timor. A markedly dominance of involute, oxycone and platycone morphologies distinguishes the Gornji Brčeli fauna from other contemporaneous faunas and points to specific palaeoecological environmental conditions. Previously, three new species were described from this locality and in the present paper one more is added (Parahedenstroemia? tatjanae). Two species hitherto considered as synonyms (Abrekites arthaberi and Owenites zitteli) are revised and treated as valid based on new material from Gornji Brčeli

LATE CARNIAN-EARLY NORIAN AMMONOIDS FROM THE GSSP CANDIDATE SECTION PIZZO MONDELLO (SICANI MOUNTAINS, SICILY)

A small collection of ammonoids from the Upper Triassic Scillato Formation at Pizzo Mondello (Agrigento, Sicily) is studied. The specimens were collected in a framework of a project aimed at providing an integrated high-resolution bio-chronostratigraphic support to the Upper Carnian-Norian magnetostratigraphic scale defined at this site, that is located in an historical area from which G.G. Gemmellaro collected the Upper Triassic of ammonoids monographed at the beginning of the XX century. The specimens from Pizzo Mondello were bed-by-bed sampled and represent the first collection of Upper Triassic ammonoids described from Sicily since Gemmellaro time. Quite several levels of the Pizzo Mondello section yielded ammonoids, but very few levels have provided more than one specimen. Due to the scarcity of specimens the taxonomic analysis has been complex because Gemmellaro, who described 166 new species, did not explain the variability of many of his taxa. Sixsteen taxa belonging to eleven genera are described. They include Placites sp. ind., Discotropites plinii (Mojsisovics), Anatropites sp., Microtropites cf. paronai, Metathisbites cf. affinis, Hyattites aff. praefloridus, Projuvavites boehmi (Gemmellaro), Projuvavites inflatus (Gemmellaro), Gonionotites cf. italicus, Gonionotites aff. recuperoi, Dimorphites noricus n. sp., Dimorphites selectus Mojsisovics, Dimorphites sp., Pregriesbachites n. gen. , P. bukowskii (Gemmellaro), Discophyllites insignis. Among the new taxa, Dimorphites noricus n. sp. formalizes the nomen nudum “Dimorphites n. sp. 1” quoted in literature for several years, that is index of the lowest subzone of the Norian stage.The small collection document the Discotropites plinii and Gonionotites italicus subzones of the uppermost Carnian Spinosus Zone and the Dimorphites noricus and D. selectus subzones of the Jandianus Zone, the first zone of the Lower Norian. This chronostratigraphic classification firmly tie the Pizzo Mondello succession to the Tethyan chronostratigraphic scale, and is crucial for the calibration of the Halobia and conodont bioevents identified in the section. The chronostratigraphic correlations based on ammonoids of the Pizzo Mondello section with Feuerkogel (Austria), Jomsom (Nepal), West Union Canyon (Nevada, USA) and Black Bear Ridge (British Columbia, Canada) is discussed. These are the most complete ammonoid-bearing sections in the world spanning the Carnian/Norian boundary, but all of them show a discrete distribution of ammonoid-bearing beds across the boundary. Ammonoid will not provide the primary marker event for the definition of the GSSP of the Norian, but they are crucial for the selection of the most significant events.

LITHOSTRATIGRAPHY, CONODONT BIOSTRATIGRAPHY AND DEPOSITIONAL ENVIRONMENT OF THE MIDDLE DEVONIAN (GIVETIAN) TO EARLY CARBONIFEROUS (TOURNAISIAN) LIPAK FORMATION IN THE PIN VALLEY OF SPITI (NW INDIA)

Bed-by-bed lithostratigraphic sections combined with sequence stratigraphy and conodont biostratigraphy provide new information on the depositional environment and age of the Lipak Formation in the Pin Valley (Spiti). The formation comprises mixed siliciclastic and calcareous sediments at lower levels, richly fossiliferous limestones with two distinct sandstone incursions at higher levels, and dark mudstones followed by a thin siltstone interval. The upper limit of the Lipak Formation is defined by the angular unconformity below the sandstones of the Permian Gechang Formation. Lithologic correlation with sections in upper Lahaul indicates that, in the Pin Valley, the formation has been truncated just below its characteristic gypsum horizon. The lower boundary of the Lipak Formation is gradational from coastal arenites of the Muth Formation; the mappable boundary is drawn at the first appearance of dark carbonaceous, argillaceous siltstone and shale.Sedimentary structures, microfacies and conodont faunas indicate a general shallow marine depositional environment of the Lipak Formation in the Pin Valley; five sequence stratigraphic units have been distinguished. Conodont data demonstrate that the lowest 33 m of the Lipak Formation of the Pin Valley is mid to late Early varcus Subzone with characteristic species of Icriodus and Bipennatus. A previously unrecognised hiatus at c. 33 m above the base, at the boundary of sequence stratigraphic units S1 and S2, represents the interval Middle varcus Subzone to at least the end of the late Famennian Early expansa Zone. Because this hiatus does not correspond to a mappable boundary, no division of the Lipak Formation into named stratigraphic units is suggested, but we refer informally to the sediments represented by cycle S1 as Lipak A, and the sediments represented by cycles S2-S5 as Lipak B. Determination of S1 as Early varcus Subzone provides a maximum age for the gradationally underlying Muth Formation. At 75 m above the base of the composite Lipak Formation section, a 58 cm black to dark grey shale interval within late Famennian fossiliferous limestones conceivably correlates with the Hangenberg Event (end-Middle praesulcata Zone). Younger conodont faunas of the Lipak Formation -dominated by species of Clydagnathus with species of Bispathodus and Pseudopolygnathus also represented- is shown to extend to the mid-Tournaisian Early crenulata Zone.&nbsp

CARNIAN REEF BIOTA FROM A MEGABRECCIA OF THE HAWASINA COMPLEX (AL AQIL, OMAN)

Carnian reef biota and brachiopods of the Misfah Formation (Hawasina complex) from a locality near the town of Al Aqil in Oman are described. A new brachiopod species, Oxycolpella arabica n. sp. is described. The composition of the Carnian reef biota in Oman is similar to those known from the Alpine-Mediterranean region. However, differences exist in the microfauna of reef dwellers, e.g. foraminifers. New stratigraphic data based on reef organisms and conodonts are presented.&nbsp

Proterozoic-like/type basal Triassic microbial build-ups of unusual height in Armenia.

The Griesbachian part of the Marmarasar Formation (Kara Baglyar) [1] in the Zangakatun (Sovetachen) section (Armenia) is characterized by microbial build-ups, spaced from 5 to 20m and surrounded by thin-bedded platy lime mudstone in a deep ramp environment. Above a basal carbonate fan crust follows a succession of thrombolitic domal forms, some of them up to 1.5m thick. The synoptic relief of the thrombolite head is estimated at 40-60cm above the muddy sea bottom. The overturned cone-shaped build-up geometry has a top head diameter up to 8m width consisting of numerous thrombolite domes, and an usual height of up to 15m. The water depth is interpreted below storm wave base and the asymmetrical build-up growth hints to a steady bottom current. Changes in the paleo-environment at the top of the kummeli conodont zone end the thrombolite growth. The overall duration of these post-extinction microbial build-ups is estimated at 700'000 years. Comparable Late Proterozoic Conophyton-Jacutophyton biostromes of the Atar area (Mauritania) [2], grown in apparently similar 80-100m water depth with quiet conditions, also show a high synoptic relief here of more than 2m above sea-bottom and decametric columnar branching build-ups. Due to a similarly large accommodation space the Zangakatun microbial reefs seem to follow the same build-up strategy

Towards a better definition of the Middle Triassic magnetostratigraphy and biostratigraphy in the Tethyan realm

Magnetostratigraphic and biostratigraphic data for the Middle Triassic (Anisian) were obtained from the Han-Bulog facies in the Nderlysaj section from the Albanian Alps and the Dont and Bivera formations in the Dont–Monte Rite composite section from the Dolomites region of northern Italy. The Nderlysaj section is biochronologically bracketed between the late Bithynian and early Illyrian substages (i.e., late-early and early-late Anisian), whereas the Dont–Monte Rite section comprises the late Pelsonian and the early Illyrian substages. The data from Nderlysaj and Dont–Monte Rite, in conjunction with already published data, allow us to construct a nearly complete composite geomagnetic polarity sequence tied to Tethyan ammonoid and conodont biostratigraphy from the late Olenekian (late-Early Triassic) to the late Ladinian (late-Middle Triassic). New conodont data require revision of the published age of the Vlichos section (Greece)