Paulian Dumitrica

Catalogue of Mesozoic Radiolarian Genera. Part 2: Jurassic-Cretaceous

ABSTRACT The catalogue of Mesozoic radiolarian genera is a revision of all described genera with re-illustration of their type species. This project was organized under the auspices of the International Association of Radiolarian Paleontologists (Inter-Rad), and was carried out by the Mesozoic Working Group. This is the second of two contributions, this one devoted to the Jurassic-Cretaceous period. It contains 581 genera with re-illustration of their type species. This part shares 30 genera in common with the Triassic catalogue, most of which arose in the Carnian, Norian and Rhaetian. The sharp difference manifested between the Triassic fauna and the Jurassic-Cretaceous fauna is so evident that it justifies two independent catalogues. A comparable division between the Jurassic and Cretaceous could not be justified however, because of the similarity of the fauna, and by the greater number of genera crossing the Jurassic-Cretaceous boundary which is three times that for the Triassic-Jurassic boundary. A distinct characteristic of Jurassic-Cretaceous genera is the high number of nomina dubia (up to 131), contrary to the low number in the Triassic interval. This reflects, in part, the influence of Haeckelian taxonomy in earlier research on Jurassic-Cretaceous faunas prior to the application of SEM techniques.The Mesozoic Working Group has carefully reviewed and re-examined the taxonomy of all available genera, their family assignment and stratigraphic ranges. Following careful comparisons, 91 genera were declared as synonyms. The review has noted 26 homonyms which were duly notified to their corresponding authors, and were corrected previous to the publication of this catalogue. In spite of this effort, unfortunately nine homonyms still remain. Two invalid nominal genera and two nomina nuda are also reported. The systematic revisions have validated 341 genera for the Jurassic-Cretaceous interval. At the end of this catalogue 24 additional photographs are presented as support for those genera having a poor original illustration of the type species.

Subduction, ophiolite genesis and collision history of Tethys adjacent to the Eurasian continental margin: new evidence from the Eastern Pontides, Turkey

This paper presents several types of new information including U–Pb radiometric dating of ophiolitic rocks and an intrusive granite, micropalaeontological dating of siliceous and calcareous sedimentary rocks, together with sedimentological, petrographic and structural data. The new information is synthesised with existing results from the study area and adjacent regions (Central Pontides and Lesser Caucasus) to produce a new tectonic model for the Mesozoic–Cenozoic tectonic development of this key Tethyan suture zone. The Tethyan suture zone in NE Turkey (Ankara–Erzincan–Kars suture zone) exemplifies stages in the subduction, suturing and post-collisional deformation of a Mesozoic ocean basin that existed between the Eurasian (Pontide) and Gondwanan (Tauride) continents. Ophiolitic rocks, both as intact and as dismembered sequences, together with an intrusive granite (tonalite), formed during the Early Jurassic in a supra-subduction zone (SSZ) setting within the İzmir–Ankara–Erzincan ocean. Basalts also occur as blocks and dismembered thrust sheets within Cretaceous accretionary melange. During the Early Jurassic, these basalts erupted in both a SSZ-type setting and in an intra-plate (seamount-type) setting. The volcanic-sedimentary melange accreted in an open-ocean setting in response to Cretaceous northward subduction beneath a backstop made up of Early Jurassic forearc ophiolitic crust. The Early Jurassic SSZ basalts in the melange were later detached from the overriding Early Jurassic ophiolitic crust. Sedimentary melange (debris-flow deposits) locally includes ophiolitic extrusive rocks of boninitic composition that were metamorphosed under high-pressure low-temperature conditions. Slices of mainly Cretaceous clastic sedimentary rocks within the suture zone are interpreted as a deformed forearc basin that bordered the Eurasian active margin. The basin received a copious supply of sediments derived from Late Cretaceous arc volcanism together with input of ophiolitic detritus from accreted oceanic crust. Accretionary melange was emplaced southwards onto the leading edge of the Tauride continent (Munzur Massif) during latest Cretaceous time. Accretionary melange was also emplaced northwards over the collapsed southern edge of the Eurasian continental margin (continental backstop) during the latest Cretaceous. Sedimentation persisted into the Early Eocene in more northerly areas of the Eurasian margin. Collision of the Tauride and Eurasian continents took place progressively during latest Late Palaeocene–Early Eocene. The Jurassic SSZ ophiolites and the Cretaceous accretionary melange finally docked with the Eurasian margin. Coarse clastic sediments were shed from the uplifted Eurasian margin and infilled a narrow peripheral basin. Gravity flows accumulated in thrust-top piggyback basins above accretionary melange and dismembered ophiolites and also in a post-collisional peripheral basin above Eurasian crust. Thickening of the accretionary wedge triggered large-scale out-of-sequence thrusting and re-thrusting of continental margin and ophiolitic units. Collision culminated in detachment and northward thrusting on a regional scale. Collisional deformation of the suture zone ended prior to the Mid-Eocene (~45 Ma) when the Eurasian margin was transgressed by non-marine and/or shallow-marine sediments. The foreland became volcanically active and subsided strongly during Mid-Eocene, possibly related to post-collisional slab rollback and/or delamination. The present structure and morphology of the suture zone was strongly influenced by several phases of mostly S-directed suture zone tightening (Late Eocene; pre-Pliocene), possible slab break-off and right-lateral strike-slip along the North Anatolian Transform Fault. In the wider regional context, a double subduction zone model is preferred, in which northward subduction was active during the Jurassic and Cretaceous, both within the Tethyan ocean and bordering the Eurasian continental margin.

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.

Catalogue of Mesozoic radiolarian genera. Part 1: Triassic

ABSTRACT The Catalogue of Mesozoic radiolarian genera is a revision of all described genera with re-illustration of their type species. This project was organized under the auspices of the International Association of Radiolarian Paleontologists (Inter-Rad), and was carried out by the Mesozoic Working Group. This contribution (Part 1), deals with the Triassic period only. There are 381 known Triassic radiolarian genera. Most have been published since the 1970s following the introduction of scanning electron microscopy (SEM), which enabled good pictures for most type species. For this reason the Triassic period is characterized by a very low number of nomina dubia (only 14), contrary to the higher number in the Jurassic-Cretaceous interval. The Mesozoic Working Group has carefully reviewed and reexamined the taxonomy of all available genera, their family assignment and stratigraphic ranges. Following careful comparisons, 73 genera were declared synonyms. The review has also detected 11 cases of homonymy that were duly notified to their authors, and were corrected previous to the publication of this catalogue; unfortunately one homonym still remains. Two invalid nominal genera are also reported herein. The systematic revisions have validated 282 genera for the Triassic, and of these only 30 genera cross the Triassic-Jurassic boundary. At the end of the catalogue 15 additional photos are presented as support for those genera having a poor original illustration of the type species.

Triassic radiolarian biostratigraphy

Abstract This paper summarizes 30 years of research on the biostratigraphy of Triassic radiolarians and presents a correlation of currently-used radiolarian zonations established in North America, Europe, Japan and Far East Russia. An up-to-date stratigraphic distribution of all hitherto described and still valid Triassic genera is provided. This new range chart consists of 282 genera and allows an accurate dating to substage level. It also clearly manifests general trends in radiolarian evolution through the Triassic. The end-Permian extinction, the most severe extinction in the history of radiolarians, was followed by a long recovery until the early Anisian. The middle and late Anisian were then characterized by a rapid explosion of new morphologies. Maximum generic diversity was attained during the early Carnian, but the first severe extinctions also occurred in the Carnian. A progressive decline of diversity took place through the Norian and Rhaetian, and ended in a mass extinction around the Triassic–Jurassic boundary.

Diversity of radiolarian families through time

The examination of radiolarian biodiversity at the family level through Phanerozoic time reveals some general trends known in other groups of organisms, especially among plankton, while some other trends seem to be quite peculiar. The Permian /Triassic crisis that is one of the most important in the evolution of marine organisms, is marked in radiolarian assemblages by the extinction of two orders (Albaillellaria and Latentifistularia) towards the end of the Permian, and mostly by the tremendous diversification of Spumellaria and Nassellaria in the early-mid Triassic. Radiolarian diversity increased from Cambrian to Jurassic, remained quite stable during the Cretaceous and has decreased slightly since then.

Early Tithonian Saturnalidae (Radiolaria) from the Solnhofen area (Southern Franconian Alb, southern Germany)

In order to complete the study of the very rich early Tithonian (Hybonoticeras hybonotum Zone) radiolarian fauna from the Mühlheim Member of the Mörnsheim Formation outcropping in the Solnhofen area, the taxa of the family Saturnalidae are described. Although rather rare, the Saturnalidae of this member contain 14 species, ten of which are new. These species belong to four genera, one of which is new (Moebicircus n. gen.), and two subfamilies (Hexasaturnalinae and Saturnalinae). The taxonomy at generic level of these late Jurassic radiolarians is founded on the basis of the position of the blades along the ring and number and morphology of the spines. Type of spines (simple or forked) has either species level value or none, depending on species. Special attention was given to anomalies, which sometimes are rather frequent, since they can give Information of paleobiological and paleoecological Orders. Among them frequent cases of open ring and additional spines withDicerosaturnalis and Siamese twins skeletons withSpongosaturninus andDicerosaturnalis are to be noted. The authors hope that this new taxonomy will give a better image of the evolution and radiation of the Saturnalidae during the Tithonian.KurzfassungDie Radiolarien-Taxa der Familie Saturnalidae aus dem Unteren Tithon des Mühlheim-Members (Mörnsheim-Formation) aus der Umgebung von Solnhofen werden beschrieben. Sie vervollständigen damit die Studie über die sehr reiche Radiolarien-Fauna derHybonoticeras hybonotum-Zone. Obwohl die Saturnalidae innerhalb des Mühlheim-Members recht selten sind, können 14 Arten (davon 10 neue) dieser Familie zugeteilt werden. Diese 14 Arten wiederum gehören zu vier Gattungen (darunterMoebicircus n. gen.) und zu zwei Unterfamilien (Hexasaturnalinae und Saturnalinae). Die taxonomische Einordnung dieser spätjurassischen Radiolarien auf der Gattungsebene basiert auf der Position der Leisten auf dem Ring und der Anzahl und Morphologie der Stacheln. Die Form der Stacheln (einfach oder gegabelt) ist, je nach Art, von kleinerer oder größerer Bedeutung. Besondere Aufmerksamkeit gehört den ziemlich häufig vorkommenden Anomalien. Sie liefern Informationen über die paläobiologische und die paläoökologische Zuordnung. Häufig sind Fälle mit offenen Ringen und zusätzlichen Stacheln (Dicerosaturnalis) und siamesische Zwillingsskelette vonSpongosaturninus undDicerosaturnalis. Die Autoren hoffen, mit dieser neuen taxonomischen Einteilung zu einem besseren Bild über die Evolution und die Verbreitung der Saturnalidae während des Tithoniums beitragen zu können.

Archaeospicularia, ordre nouveau de radiolaires : une nouvelle étape pour la classification des radiolaires du Paléozoïque inférieur

Abstract A new radiolarian order — Archaeospicularia — is proposed for some Lower Paleozoic radiolarians previously considered to belong to Spumellaria and to Collodaria. It is characterized by a globular shell made of several spicules which can be free, interlocked, or fused to formed a latticed wall. The present paper gives the definition of this order and proposes a first classification. It is supposed that the Archaeospicularia represents the oldest radiolarian group and that in the Lower Paleozoic it gave rise to the orders Entactinaria, Albaillellaria, and probably Spumellaria by the reduction of the number of initial spicules. The origin of this order and its relationships with other groups of organisms with siliceous skeletons are also briefly discussed.

Family Kungalariidae, n. fam., new Mesozoic entactinarian Radiolaria with a nassellarian-type initial spicule

Based on internal structure, a new family of entactinarian radiolarians, the Kungalariidae, is described with three new genera and four species: Kungalaria newcombi, Cachecreekaria californiensis, Transylvanaria devaensis, and T. hattorii. Members of this family have an eccentric internal, nassellarian-type initial spicule with bar MB, rays A, V, L, I, and spine Ax; a medullary shell built above the plane of lateral rays as in the cephalis of many nassellarians; and a spherical to subspherical cortical shell around the medullary shell. This new family is part of a group of Triassic entactinarians structurally intermediate between Entactinaria, or spicule-bearing Spumellaria, and Nassellaria. The new genera and species described occur in the Rhaetian of Queen Charlotte Islands, British Columbia, Aalenian to early-mid Bajocian of central Japan, Cenomanian of California, and Coniacian of Romania.

EARLY LADINIAN RADIOLARIAN FAUNA FROM THE MONTE SAN GIORGIO (SOUTHERN ALPS, SWITZERLAND): SYSTEMATICS, BIOSTRATIGRAPHY AND PALEO(BIO)GEOGRAPHIC IMPLICATIONS

A well-preserved radiolarian fauna was recovered from the lower part of the San Giorgio Dolomite (Monte San Giorgio, UNESCO WHL, Switzerland), belonging to the Eoprotrachyceras curionii Ammonoid Zone (earliest Ladinian). The depositional environment, consisting of an intraplatform basin with restricted circulation, seemingly resulted in an unusual radiolarian assemblage displaying neglegible percentages and very low diversity of Nassellaria. Seventy-three species have been identified and seven new species have been described: Eptingium danieli n. sp., Eptingium neriae n. sp., Parentactinosphaera eoladinica n. sp., Sepsagon ticinensis n. sp., Sepsagon ? valporinae n. sp., Novamuria wirzi n. sp. and Pessagnollum hexaspinosum n. sp. The taxonomic status of the recovered species has been reassessed and four new genera have been introduced: Bernoulliella gen. n., Eohexastylus gen. n., Ticinosphaera gen. n. and Lahmosphaera gen. n. The new radiolarian assemblages, the first so far described from the Monte San Giorgio, supplement further information to the taxa occurring in the uppermost Ladinocampe multiperforata Radiolarian Zone, as yet poorly defined, also confirming the absence of major changes in the radiolarian fauna across the Anisian/Ladinian boundary. The widespread co-occurrence of taxa doubtlessly testifies to the existence, in early Ladinian times, of open-marine connections between the basin of the Monte San Giorgio and the pelagic “Buchenstein” basins of the central and eastern South-Alpine domain and farther afield across the Tethys.