Carnian Norian Research Articles

MESOZOIC THRIPS AND EARLY EVOLUTION OF THE ORDER THYSANOPTERA (INSECTA)

Abstract The oldest known thrips, order Thysanoptera, are described from the Late Triassic of Virginia and Kazakhstan: Triassothrips virginicus Grimaldi and Fraser, new genus and species (Cow Branch Formation: Carnian), and Kazachothrips triassicus Shmakov, new genus and species (Tologoy Formation: Carnian–Norian). Prior to this the oldest definitive thysanopterans were from the Late Jurassic of Kazakhstan (Kimmeridgian), some 80 My younger. Well-preserved, relatively complete, wing venation indicates the Triassic thrips are phylogenetically the basalmost thysanopterans, and their venation even allows identification and homologizing the highly reduced veins in Recent thrips. Another basal thrips is described from mid–Cretaceous (Turonian) amber of New Jersey, Cretothrips antiquus Grimaldi, new genus and species, which is similar to several Recent genera of Aeolothripidae. A phylogenetic hypothesis of basal relationships in Thysanoptera based on wing venation supports a basal relationship for Aeolothripida...

Upper Triassic carbonate deposits of Seram (Indonesia): palaeogeographic and geodynamic implications

The Upper Triassic limestones of central and western and Seram, were deposited on an extensive carbonate platform, already identified in various localities all around the Banda Sea: Sinta Ridge, central–east Sulawesi, Buru, Misool and the Wombat Plateau (off NW Australia). The Triassic deposits are found in the parautochthonous, as well as in the allochthonous series of Seram; the facies of the two series are of Gondwanian–Australian type in the Parautochthonous and of Laurussian–Asian type in the Allochthonous. The Asinepe Limestone (=Manusela Formation), on which this study is based, has been considered as part of the allochthonous series. The Triassic reefal lithotypes can be divided into four main facies, as follows: (1) the boundstone facies forming the buildup cores; (2) the oncolitic grainstone-rudstone facies, indicating high energy conditions; (3) foraminiferal packstone-grainstone facies, characteristic of moderate to high energy conditions; and (4) the foraminiferal-megalodont mudstone facies, inferred to have accumulated in a quiet lagoonal environment. Forming the buildup cores of about 4 m long, 2 m high; they are separated by depressions filled with reef detrital sands; The Asinepe Limestone was deposited during the Late Triassic (Carnian–Norian to Rhaetian). This range is corroborated by foraminiferal and palynological data, and the coral framebuilders give evidence for a Norian–Rhaetian age. There is a some consensus that Seram and the Island of Buru, located west of Seram, belong to the same tectonic block (Seram-Buru Block). According to geochemical and geodynamic interpretations, the Seram-Buru Block is derived from Irian Jaya or from Papua New Guinea. The palynological results are consistent with reconstructions that place the Seram-Buru Block in a palaeogeographic zone distinct from that of Sulawesi, and therefore from the Kolonodale Block. For these reasons, it is here proposed that, during the Upper Triassic, the Seram-Buru Block and the Kolonodale Block were two separated entities, the former located in a more tropical position than the latter. In addition, the Seram palynological association shows a composite microflora of the warm Onslow and the cold Ipswich-types, suggesting that the Seram microcontinent moved progressively to the north and crossed the boundary between the temperate and the warm subequatorial belts at one point in the Late Triassic–Early Jurassic.

Carnian–Norian biomagnetostratigraphy at Silická Brezová (Slovakia): correlation to other Tethyan sections and to the Newark Basin

Correlations of Upper Triassic magnetic stratigraphies from Tethyan sections have been hampered by difficulties with conodont biostratigraphy and taxonomy, and discontinuous sedimentation, particularly in the ‘Hallstatt Limestones’ of Turkey and Austria. The magnetic stratigraphy and conodont biostratigraphy from the Upper Carnian to Upper Norian limestones exposed at Silická Brezová (Slovakia) can be correlated to other Tethyan sections and to the continental succession in the Newark Basin. The resulting correlations help to resolve some of the apparent discrepancies in existing conodont zonations, and result in a revised correlation to North American terrestrial vertebrate and palynological zones. The correlations imply that the Norian–Rhaetian boundary lies within Newark polarity zone E17r at ∼207 Ma. The Carnian–Norian boundary lies close to the base of Newark polarity zone E7r at ∼226 Ma. This implies durations for the Norian and Rhaetian stages of 19 Myr and 7 Myr, respectively.

Triassic temnospondyls of the Pranhita–Godavari basin, India

The Pranhita–Godavari (P–G) basin of central India has yielded Early, Middle and Late Triassic temnospondyl families. Bracyops laticeps, the type for the family Brachyopidae was first described from the Lower Triassic ‘Mangli Beds’ of the northernmost extension of the P–G basin. In the northern and central parts of the P–G basin itself, the Middle Triassic Yerrapalli Formation has Stanocephalosaurus rajareddyi, a paracyclotosaurid, and the Upper Triassic Maleri Formation has Buettneria maleriensis, a metoposaurid and two other chigutisaurid taxa, Compsocerops cosgriffi and Kuttycephalus triangularis. A critical review of Triassic temnospondyls of the P–G basin indicates that the affinities of S. rajareddyi and K. triangularis are somewhat uncertain and discovery of further material is necessary to establish their relationships among similar temnospondyls of the world. It is also noted that B. maleriensis is displaced by the two chigutisaurid genera and species at the Carnian–Norian boundary. Thus, P–G basin is unique in having Pangaean metoposaurids and exclusively Gondwanan chigutisaurids in successive faunal zones within the same formation. Significantly, the end of Carnian is marked by the demise of metoposaurids in India as well as in Africa and Europe. In North America, their size appears to have diminished during that time.

Integrated Upper Carnian to Lower Norian biochronology and implications for the Upper Triassic magnetic polarity time scale

We summarize the ammonoid, conodont and halobiid biochronology of the Upper Carnian to Lower Norian, based on a discussion of data in the Alps, Sicily, Balkans, Turkey, Himalayas and Timor. With this integrated biostratigraphic scale, the Pizzo Mondello section (Sicily) can be recalibrated and the Carnian–Norian boundary more precisely located there. As a result, the magnetostratigraphy of this section is now in good agreement with previous results from Turkey, although the latter series are more condensed. Cross-correlation of available magnetostratigraphic data from marine Tethyan sections allow us to construct a composite Upper Carnian to Upper Norian geomagnetic polarity time scale (GPTS). This GPTS leads us to question previously proposed magnetobiostratigraphic and chronostratigraphic correlations within the Upper Triassic Newark non-marine sedimentary sequence.

Earliest evidence of dinosaurs from central Gondwana : Raath M.A., Memoirs - Queensland Museum, 1996, 39/3 (703–709)

Dinosaur footprints found in an outcrop of the Caturrita Formation (Rio Grande do Sul State, Southern Brazil), associated with a diverse and well preserved record of fauna and flora, reopen the debate about its exclusive Triassic age. The studied footprints were identified as Eubrontes isp. and are interpreted as having been produced by large theropod dinosaurs. The morphological characteristics and dimensions of the footprints are more derived than those commonly found in the Carnian–Norian, and are more consistent with those found during the Rhaetian–Jurassic. The trackmaker does not correspond to any type of dinosaur yet known from Triassic rocks of Brazil. Recent studies with the paleofloristic content of this unit also support a more advanced Rhaetian or even Jurassic age for this unit.

Geology of the Cadwallader Group and the Intermontane–Insular superterrane boundary, southwestern British Columbia

Several lower Mesozoic, fault-bounded units separate the Intermontane and Insular superterranes in southwestern British Columbia. Detailed study of one of these Mesozoic units, the Cadwallader Group, helps clarify the boundary between the superterranes and establish the tectonic evolution of southwestern British Columbia. The Cadwallader Group is the oldest unit in an Upper Triassic through Middle Jurassic volcanic and sedimentary tectono-stratigraphic terrane. Two formations, the Pioneer and the Hurley, compose the Cadwallader Group; the previously recognized Noel Formation is no longer considered valid. The Pioneer Formation contains pillow basalt, flows, and basalt breccia. Siltstone, sandstone, conglomerate, and minor amounts of limestone megabreccia and basalt belonging to the Hurley Formation conformably overlie the Pioneer. The Hurley spans latest Carnian or earliest Norian to middle Norian time. Two episodes of deformation affected the Cadwallader, and a thrust fault separates the group from slightly younger clastic rocks of the Tyaughton Group. Similarities in clastic rocks indicate the Tyaughton was deposited on the Cadwallader; together the units form the Cadwallader terrane. Basalts and clastic rocks in the terrane record deposition in or near a Carnian to earliest Norian volcanic arc. Volcanism waned later in the Norian, but presence of the arc is preserved in the clastic rocks.Oceanic rocks of the Middle Triassic to Middle Jurassic Bridge River terrane became juxtaposed with the Cadwallader terrane in Middle Jurassic time, after which the terranes functioned as a single tectonic block. Contrasting volcanic histories suggest that the Cadwallader terrane was not accreted to the Intermontane superterrane until Middle Jurassic or Early Cretaceous time, although the similar tectonic settings of Stikinia and the Cadwallader terrane allow a common earlier history. The Cadwallader terrane is not part of either the Alexander terrane or Wrangellia, and so the inboard margin of the Insular superterrane must lie west of the Cadwallader terrane.

Tethyan evolution of Turkey: A plate tectonic approach

The Tethyan evolution of Turkey may be divided into two main phases, namely a Palaeo-Tethyan and a Neo-Tethyan, although they partly overlap in time. The Palaeo-Tethyan evolution was governed by the main south-dipping (present geographic orientation) subduction zone of Palaeo-Tethys beneath northern Turkey during the Permo-Liassic interval. During the Permian the entire present area of Turkey constituted a part of the northern margin of Gondwana-Land. A marginal basin opened above the subduction zone and disrupted this margin during the early Triassic. In this paper it is called the Karakaya marginal sea, which was already closed by earliest Jurassic times because early Jurassic sediments unconformably overlie its deformed lithologies. The present eastern Mediterranean and its easterly continuation into the Bitlis and Zagros oceans began opening mainly during the Carnian—Norian interval. This opening marked the birth of Neo-Tethys behind the Cimmerian continent which, at that time, started to separate from northern Gondwana-Land. During the early Jurassic the Cimmerian continent internally disintegrated behind the Palaeo-Tethyan arc constituting its northern margin and gave birth to the northern branch of Neo-Tethys. The northern branch of Neo-Tethys included the Intra-Pontide, Izmir—Ankara, and the Inner Tauride oceans. With the closure of Palaeo-Tethys during the medial Jurassic only two oceanic areas were left in Turkey: the multi-armed northern and the relatively simpler southern branches of Neo-Tethys. The northern branch separated the Anatolide—Tauride platform with its long appendage, the Bitlis—Pötürge fragment from Eurasia, whereas the southern one separated them from the main body of Gondwana-Land. The Intra-Pontide and the Izmir—Ankara oceans isolated a small Sakarya continent within the northern branch, which may represent an easterly continuation of the Paikon Ridge of the Vardar Zone in Macedonia. The Anatolide-Tauride platform itself constituted the easterly continuation of the Apulian platform that had remained attached to Africa through Sicily. The Neo-Tethyan oceans reached their maximum size during the early Cretaceous in Turkey and their contraction began during the early late Cretaceous. Both oceans were eliminated mainly by north-dipping subduction, beneath the Eurasian, Sakaryan, and the Anatolide- Tauride margins. Subduction beneath the Eurasian margin formed a marginal basin, the present Black Sea and its westerly prolongation into the Srednogorie province of the Balkanides, during the medial to late Cretaceous. This resulted in the isolation of a Rhodope—Pontide fragment (essentially an island arc) south of the southern margin of Eurasia. Late Cretaceous is also a time of widespread ophiolite obduction in Turkey, when the Bozkir ophiolite nappe was obducted onto the northern margin of the Anatolide—Tauride platform. Two other ophiolite nappes were emplaced onto the Bitlis—Pötürge fragment and onto the northern margin of the Arabian platform respectively. This last event occurred as a result of the collision of the Bitlis—Pötürge fragment with Arabia. Shortly after this collision during the Campanian—Maastrichtian, a subduction zone began consuming the floor of the Inner Tauride ocean just to the north of the Bitlis—Pötürge fragment producing the arc lithologies of the Yüksekova complex. During the Maastrichtian—Middle Eocene interval a marginal basin complex, the Maden and the Çüngüş basins began opening above this subduction zone, disrupting the ophiolite-laden Bitlis—Pötürge fragment. The Anatolide-Tauride platform collided with the Pontide arc system (Rhodope—Pontide fragment plus the Sakarya continent that collided with the former during the latest Cretaceous along the Intra Pontide suture) during the early to late Eocene interval. This collision resulted in the large-scale south-vergent internal imbrication of the platform that produced the far travelled nappe systems of the Taurides, and buried beneath these, the metamorphic axis of Anatolia, the Anatolides. The Maden basin closed during the early late Eocene by north-dipping subduction, synthetic to the Inner-Tauride subduction zone that had switched from south-dipping subduction beneath the Bitlis—Pötürge fragment to north dipping subduction beneath the Anatolide—Tauride platform during the later Palaeocene. Finally, the terminal collision of Arabia with Eurasia in eastern Turkey eliminated the Çüngüş basin as well and created the present tectonic regime of Turkey by pushing a considerable piece of it eastwards along the two newly-generated transform faults, namely those of North and East Anatolia. Much of the present eastern Anatolia is underlain by an extensive mélange prism that accumulated during the late Cretaceous—late Eocene interval north and east of the Bitlis—Pötürge fragment.

Upper Triassic salt deposits of the western North Atlantic

The Amoco–Imp–Skelly Osprey H-84 well, located in the Carson Subbasin on the eastern Grand Banks of Newfoundland, penetrated 2054 m of evaporites consisting almost exclusively of halite. These are dated palynologically as Carnian–Norian to Hettangian–Sinemurian and establish the occurrence of Upper Triassic evaporites on the western side of the North Atlantic. A lateral-fractionation model is proposed to explain the progressive decrease in less soluble evaporitic minerals west of the western periphery of Tethys. According to this model, slow and intermittent encroachment of the sea into the developing intracontinental graben system occurred after initial rifting. This encroachment took place in a hot and arid climatic zone and led to the brines becoming progressively depleted in less soluble salts towards the distal margins of the basin system. The similarity in composition of the Upper Triassic evaporitic sequences on the Grand Banks and in the Lusitanian Basin indicates that the two areas were close at this time. This would preclude major rotation of the Iberian Peninsula and the presence of a cratonic arch between the Iberian Peninsula and Grand Banks.