Rossana Martini

Synchrony of the Central Atlantic magmatic province and the Triassic-Jurassic boundary climatic and biotic crisis

The evolution of life on Earth is marked by catastrophic extinction events, one of which occurred ca. 200 Ma at the transition from the Triassic Period to the Jurassic Period (Tr-J boundary), apparently contemporaneous with the eruption of the worlds largest known continental igneous province, the Central Atlantic magmatic province. The temporal relationship of the Tr-J boundary and the provinces volcanism is clarified by new multidisciplinary (stratigraphic, palynologic, geochronologic, paleomagnetic, geochemical) data that demonstrate that development of the Central Atlantic magmatic province straddled the Tr-J boundary and thus may have had a causal relationship with the climatic crisis and biotic turnover demarcating the boundary.

Triassic pelagic deposits of Timor: palaeogeographic and sea-level implications

Abstract In West Timor, Triassic deposits are found in the Parautochthonous Complex, as well as in the Allochthonous series of Sonnebait. A detailed biostratigraphic investigation, integrating field observations and facies analysis, allowed the reconstruction of a synthetic lithostratigraphic succession for the Upper Triassic; a stratigraphic transition from Carnian shales to Upper Norian–Rhaetian limestones is also shown by this study. The fossil content predominantly originates from an open marine environment; lithostratigraphic Units A–E are dated on the basis of radiolaria and palynomorphs, and Unit H, on ammonites and conodonts. The presence of pelagic bioclasts, together with normal grading, horizontal laminations, and current ripples, is indicative of a distal slope to basin environment. The ammonite rich condensed limestone of Unit H was deposited on a ‘pelagic carbonate plateau’ exposed to storms and currents. The organic facies have been used as criteria for biostratigraphy, palaeoenvironmental interpretation, and sequence stratigraphy. The palaeontological analysis of the Triassic succession of West Timor is based on the investigation of radiolaria and palynomorphs, in the marls and limestones of Units A–E, and also on ammonites and conodonts in the condensed limestone of Unit H. Units A and B are Carnian (Cordevolian) in age, based on the occurrence of the palynomorph Camerosporites secatus , associated with ‘ Lueckisporites ’ cf. singhii , Vallasporites ignacii , Patinosporites densus and Partitisporites novimundanus . Unit C is considered as Norian, on the basis of a relatively high percentage of Gliscopollis meyeriana and Granuloperculatipollis rudis. Unit D contains significant palynomorphs and radiolaria; the organic facies, characterized by marine elements, is dominated by the Norian dinocysts Heibergella salebrosacea and Heibergella aculeata ; the radiolaria confirm the Norian age. They range from the lowermost Norian to the lower Upper Norian. Unit E also contains radiolaria, associated in the upper part with the well-known marker of the Upper Norian, Monotis salinaria . For Unit E, the radiolaria attest to a Lower to Upper Norian age based on the occurrence of Capnodoce and abundant Capnuchosphaera ; the upper part is Upper Norian to Rhaetian based on the presence of Livarella valida . Finally, the blocks of condensed limestone with ammonites and conodonts of Unit H allowed the reconstruction of a synthetic stratigraphic succession of Upper Carnian to Upper Norian age. Our stratigraphic data lead to the suggestion that the Allochthonous complex, classically interpreted as a tectonic melange of the accretionary prism of the Island Arc of Banda, is a tectonically dismembered part of a Triassic lithostratigraphic succession.

Middle permian (midian) foraminiferal assemblages from the batain plain (Eastern Oman): Their significance to neotethyan paleogeography

Exceptionally rich Permian fusulinid assemblages, varying in age from Yakhtashian to Dzhulfian, were found in reworked limestone blocks from conglomerates of the Aseelah Unit, recently defined in the Batain Plain and dated possibly as Upper Triassic. This paper only deals with the Middle Permian, Midian (= Capitanian) microfaunas from the conglomerates. The Aseelah Unit is found associated with the Triassic Sal Formation, tectonically overlying the Qarari Unit, and is dated as Middle to Late Permian based on ammonoid assemblages and conodonts. The boulders of the Aseelah Unit are composed of exclusively Permian skeletal limestones in a sandy matrix; the limestones were deposited on a shallow marine shelf environment from the southern Neotethys. The Qarari Unit is interpreted as a hemipelagic series deposited on the distal slope of the Arabian carbonate platform. The Midian foraminifers from the Batain Plain are similar to some assemblages of Transcaucasia, of the Abadeh area (Iran), of SW Turkey (Taurus Mountains), and some, especially the Neoschwagerinidae, exhibit affinities with microfaunas of the eastern Tethys terranes of Japan. However, similar Neoschwagerinid assemblages were not found in any significant area of the Arabian Peninsula (Oman Mountains, Huqf-Haushi area, and Khuff area).

Sedimentology, stratigraphy, and micropalaeontology of the Upper Triassic reefal series in Eastern Sulawesi (Indonesia)

An Upper Triassic (Upper Norian-Rhaetian) carbonate complex, composed of open marine to reefal deposits, has been investigated for the first time in Eastern Sulawesi. The age is based on the occurrence of benthic foraminifera, and also of the Upper Sevatian to Rhaetian conodont Misikella posthernsteini Kozur and Mock. Palynological assemblages contain Upper Triassic-Lower Jurassic palynomorphs. The scleractinian coral Retiophyllia seranica and the chaetetid sponge Blastochaetetes intabulata, together with Solenoporacean algae, are the main framebuilders of the reefal facies. The entire carbonate series, composed of conodont bearing limestones, reefal deposits, and intertidal/supratidal cryptalgal laminites, shows a general regressive trend from a marginal to an inner platform environment. The relationship between microfaunal distribution and sequence analysis is discussed. The Upper Triassic foraminifers and palynomorphs of Eastern Sulawesi show affinities to microfaunas of the Australian-Indonesian southern Tethyan domain, and the general organisation of the platform should be investigated through further studies from Banda Sea dredgings.

Upper Triassic shallow water limestones in the Sinta Ridge (Banda Sea, Indonesia)

Ten rock samples were dredged during the Banda Sea I cruise in the northern slope of the Sinta Ridge, which separates the North and South Banda basins. Some of the samples are limestones from a very shallow marine environment, with Upper Norian (to Rhaetian?) benthic Foraminifera. Similarities with eastern Sulawesi, Buru and Seram are consistent with an independant Upper Triassic block and the origin of the Banda Sea microcontinents is questionable.

Upper Triassic Tethyan Carbonates off Northwest Australia (Wombat Plateau, ODP Leg 122)

SummaryLeg 122 of the Ocean Drilling Program (ODP) recovered Upper Triassic (Carnian to Rhaetian) sediments at the sediment-starved passive continental margin off Northwestern Australia.The early-rift series at the Wombat Plateau, a northern sub-plateau of the Exmouth Plateau, consists of Upper Triassic fluviodeltaic siliciclastics and shallow-marine carbonates including reefal facies. Twenty-five microfacies types could be distinguished.These sequences are capped by an erosional ‘post-rift unconformity’ with a 70 m.y. hiatus during the Jurassic. The Wombat Plateau bears only a thin post-rift sedimentary cover of Cretaceous to Cenozoic age.The Carnian and Norian sequences are dominated by fluviodeltaic sediments that contain many carbonate intercalations. Their frequency and the kind and amount of allochems allow the reconstruction of a storm-influenced deltaic to prodeltaic environment with restricted estuarine (intradeltaic) lagoons and high-energy carbonate sand shoals in front of the delta lobes.The presence of the foraminifersTriasina oberhauseri andTriasina hantkeni in Sites 762 and 764 indicate a Norian to Rhaetian age. The reefal platform can be differentiated in a lagoon to patch reef environment with abundant Aulotortidae, and a patch reef to shelf zone with smaller foraminifers.The ‘Rhaetian’ starts with a global sequence boundary. Several shallowing-upward cycles from bioturbated wackestones to dolomitic algal bindstones suggest a shallow-subtidal to intertidal environment at Site 761. Typical reef development was observed at the more “distal’ Site 764. The limestone-marl alternations of the open marine shelf grade into local bioclastic and oolitic grainstones, which are the base for the incipient carbonate buildup. Calcisponge patch reefs developed into coral reefs. Several cycles characterize a ‘catch-up’ system grading into a ‘keep-up’ carbonate system. The reef growth ended abruptly with the second sequence boundary (211 Ma afterHaq et al., 1987), coinciding with the worldwide latest Rhaetian sea level fall, followed by renewed transgression.By comparison with Upper Triassic carbonates of the western Tethys (e.g., the Northern Calcareous Alps), several microfacies types could be combined to characteristic facies units: biolithite facies, different reef talus types, grapestoneoncoid facies, and calcareous algae-foraminifera detritus facies showing the reef-backreef/fore-reef-lagoon transitions.Detailed investigations of microfacies, wireline logs and high-resolution seismics allow the determination of depositional sequences (sequence stratigraphy). We distinguish influences of regional or global tectonics and/or eustatic sea-level changes. The results show that regional tectonic movements are of minor importance in the Rhaetian and that theHaq et al. (1987) cycle chart could also be used at the passive margin of Northwest Australia.

Nouvelle classificationdes Foraminifères Endothyroïdes du Trias

A systematic revision of the Triassic endothyroid Foraminifera allows to describe the following taxa: Endotebidae,nov. fam., Endotriadidae, nov. fam., Endotebanella, nov. gen., type-species Endothyranella kocaeliensis Dager, 1978a, Endotriada, nov. gen., type-species Endotriada tyrrhenica, nov. gen. nov. sp., Endotriadella, nov. gen., type-species Ammobaculites wirzi Koehn-Zaninetti, 1968. The species Endoteba bithynica, nov. sp., and Endotriada tyrrhenica, nov. gen. nov. sp., are described. The genus Endoteba and various species are emended. Biostratigraphic, paleogeographic and phylogenetic values of the taxa are discussed.

FORAMINIFERA, ALGAE AND CARBONATE MICROPROBLEMATICA FROM THE LATE WUCHIAPINGIAN/DZHULFIAN (LATE PERMIAN) OF PELOPONNESUS (GREECE)

The origin of late Permian olistoliths found in the Glypia Cenozoic flysch must be seeked in regions located to the east of the Parnon Mountain and in units that were more internal to Pindos Unit, especially in the islets of Karavia in the Argolis Gulf, and the Episkopi Formation in Hydra Island, that display probably the largest outcrops of this age. The most interesting olistolith is a bioclastic grainstone. It yields about forty taxa of algae, microproblematica, smaller foraminifers and fusulinids, that are briefly described. Three markers generally not co-occurring are locally associated: Paradunbarula ( Shindella ) shindensis , Hemigordiopsis cf. luquensis and Colaniella aff. minima . The age of the Paradunbarula ( Shindella ) biozone is most probably late Wuchiapingian/Dzhulfian, although other datings have been proposed from late Capitanian to late Changhsingian. Due to this dating of the Shindella zone, the coexistence of the first Colaniella with the last Hemigordiopsis are not late Capitanian/Midian in age, but late Wuchiapingian. The similarities of the Greek microfauna with that of South China and southeastern Pamirs, are incompatible with a larger Paleotethys but support the paleogeographic reconstructions which indicate a close location of these geographic units (Pangea B).

Agglutinated versus microgranular foraminifers: end of a paradigm?

Large benthic agglutinated foraminifers possess subepidermal wall textures similar to the keriothecal textures observed in some Fusulinana. Considering the gap exceeding 50 million years in the record of the first alveolar large agglutinated Mesozoic forms (Textulariana) and their last known Palaeozoic microgranular homologues (Fusulinana), the two groups have been regarded as distinct lineages. The discovery of Wernlina reidae gen. et sp. nov. in Late Triassic carbonate rocks of a Panthalassan terrane questions this assumption. This new form, the earliest unequivocal Mesozoic ‘agglutinated’ alveolar foraminifer, originated from an Endotebidae (Fusulinana). The identification of a Triassic missing link between microgranular and agglutinated foraminifers not only fills the 50 million year gap but also challenges current foraminiferal classification. http://zoobank.org/urn:lsid:zoobank.org:pub:8F01DB56-390C-4D95-A692-9A815338ACFC

The break-up of East Gondwana along the northeast coast of Oman: evidence from the Batain basin

Recent detailed studies on the Batain nappes (northeast coast of Oman), which represent a special part of the so-called ‘Oman Exotics’, have led to a better understanding of the Neotethyan geodynamic evolution. The Batain Exotics bear witness to volcanic activity, sea-level changes, tectonic instability, rifting and oceanization along the Eastern Oman margin during Late Palaeozoic and Mesozoic times. They allow definition of the Batain basin as an aborted Permian branch of Neotethys. This marine basin was created in Early Permian times extending southward to the East African/ Madagascar region and was linked to the Karoo rift system. The presented revised classification of the Batain nappes considers the Batain basin to be no longer a part of the Hawasina basin and the Neotethyan margin proper. We attribute the Batain basin to a Mozambique–Somali–Masirah rift system (Somoma). This system started in Early Permian, times, creating a marine basin between Arabia and India/Madagascar; rifting in the Late Triassic and oceanization during Late Jurassic times led to the separation of East Gondwana.