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The Bravaisberget Formation of southern Spitsbergen (the youngest formation of the Sassendalen Group; Middle Triassic–Carnian) comprises a succession of organic-rich and sandy phosphogenic deposits that developed in a marginal part of the Svalbard basin, in response to a high biological productivity event in the Barents Shelf. The basin margin was bounded on the southwest by the elevated structure of the SÝrkapp-Hornsund High. North of the high, the subsiding shelf bottom stretched from southern to western Spitsbergen. The organic-rich, fine-grained sedimentation that gave rise to the formation of the Passhatten Member extended southward after the Anisian transgression; it reached the topmost part of the SÝrkapp -Hornsund High during the maximum flooding of the basin in the early Ladinian. The sudden appearance of deltaic deposits of the Karentoppen Member directly after the maximum flooding was a consequence of short-lived tectonic activity of the SÝrkapp -Hornsund High and the adjacent land area. Reworking and redistribution of the deltaic sediments during the Ladinian brought about the formation of shallow-marine clastic facies of the Somovbreen Member. Decreasing depositional rates close to the Middle-Late Triassic boundary led to a regional hiatus and the formation of a condensed phosphorite horizon at the top of the Somovbreen Member. The sedimentation of the Bravaisberget Formation ended in the early Carnian. The youngest siliciclastic and spiculitic sediments of the Van Keulenfjorden Member were deposited in southern and western Spitsbergen in shallow- to marginal-marine environments.

The connecting ring in the Recent Nautilus is composed of two layers: a fibrous, organic inner layer, and a porous, spherulitic-prismatic outer layer. The organic layer is an uncalcified continuation from the nacreous layer of the septal neck. In the Mesozoic nautilids Cymatoceras and Paracenoceras from Madagascar, that have the Nautilus type of siphuncles, the inner fibrous-organic layer of the connecting ring has been destroyed by diagenesis. The outer spherulitic-prismatic layer is twice as thick as in Nautilus, which indicates that, in addition to jet-powered swimming, they also used short-term buoyancy changes for vertical migrations, and that the mode of life of these nautilids was somewhat different from that of the Recent Nautilus. Moreover, the Madagascar nautilids lack the auxiliary ridge by which the connecting ring in Nautilus is firmly attached to the inner surface of the preceding septal neck. The siphuncle in Nautilus can therefore withstand a much higher hydrostatic pressure than that in t...

A bio-magnetostratigraphy for the Lower Triassic is constructed, using the ammonoid biostratigraphy from arctic Boreal successions. Combined thermal and alternating field demagnetisation determines the Triassic magnetic field polarity in 86% of specimens, with 36% showing linear trajectory line-fits and the remainder great circle trends towards the characteristic magnetisation. Mean pole directions for the Deltadalen (=50°, φ=159°, dp/dm=3.9°/5.1°), Lusitaniadalen (=56°, φ=163°, dp/dm=4.4°/5.4°) and Vendomdalen (=57°, φ=143°, dp/dm=4.4°/5.4°) members fall close to the European Lower Triassic apparent polar wander path. Mean directions for two of these member-means pass the reversal test. The remanence is predominantly carried by magnetite. The polarity stratigraphy, when integrated with the ammonoid and meager conodont data is similar to that determined from successions in the Sverdrup Basin (Canada). The Permian-Triassic boundary post-dates a pronounced palynofloral turnover, and pre-dates a short duration reverse magnetozone (LT1n.1r). In the correlated Shangsi section (in S. China) LT1n.1r occurs after the FAD of H. parvus, but in the arctic is within the Otoceras boreale Zone. The late Griesbachian to early Smithian is mostly reverse polarity, with three normal polarity intervals, overlain by mid and late Smithian normal polarity. The Spathian contains four reverse polarity intervals, the oldest one within the early Spathian with the remainder in the late Spathian. Transition into the Anisian is within the uppermost reverse magnetozone, a feature documented in other sections of this age. The polarity pattern is correlated to other marine sections, indicating the robustness of the bio-magnetostratigraphic composite and its utility in calibrating Lower Triassic time.

Conodont faunas are described from Triassic sections of Svalbard, and their occurrences are locally correlated with established ammonoid zones. With a synthesis of previous conodont-based publications, the current work presents a taxonomically up-to-date compilation of conodont data for the Triassic of Svalbard that is used to construct a conodont-based biochronology, indexed to the current lithostratigraphic nomenclature. Twenty-eight taxa spanning the earliest Griesbachian to the earliest Carnian are presented in a range chart. The examined conodont faunas are correlated with well-established conodont zonations of the Canadian Arctic, and in turn also form the basis for regional correlations.

Palaeomagnetic and biostratigraphic data were obtained for the latest Ladinian and most of the Carnian (Botneheia Formation to basal Kapp Toscana Group), from two sections in central Spitsbergen (Svalbard archipelago). Thermal and alternating field (AF) demagnetization reveals a magnetization of both normal and reversed polarities. The mean directions pass reversal and fold tests and are similar to other European Late Triassic palaeopoles. One of the sections displays 15° of vertical-axis, clockwise, tectonic rotation on a decollement in the underlying Botneheia Formation. The magnetostratigraphy is dominated by normal polarity in the uppermost Botneheia Formation and into the Tschermakfjellet and basal De Geerdalen formations. A substantial hiatus characterizes the Ladinian–Carnian boundary in central Spitsbergen, so reverse magnetozones, identified in Tethyan sections near this boundary, are absent. Magnetostratigraphic correlation, along with palynostratigraphic constraints, indicates that most of the De Geerdalen Formation is Lower Carnian. The magnetostratigraphy and palynology indicates that the Isfjorden Member (upper unit of the De Geerdalen Formation) is probably mid-Carnian in age. Change in the lithological architecture in the Isfjorden Member, compared with the underlying parts of the De Geerdalen Fm, suggests a hiatus near the base of the member, which may represent a mid-Carnian unconformity, not previously recognized on Spitsbergen.

Ostracods were found in two pieces of Baltic amber for the first time. The animals belong to the freshwater genus Cyclocypris. Since Baltic amber was formed during Eocene times in southern Scandinavia, the age of the specimens is estimated at 42–54 million years. As aquatic organisms, ostracods are seldom trapped in amber; it is considered that one specimen, already dead and dried, was either blown onto sticky resin on a plant stem, or washed there by a high flood level, while the other was probably splashed, alive, in a drop of water against the flowing resin, again probably during a flood. Associated faunal remains, including other crustaceans, suggest a coastal palaeoenvironment with some marine as well as freshwater influence.

The Vikinghøgda Formation (250 m) is defined with a stratotype in Deltadalen-Vikinghøgda in central Spitsbergen. The Vikinghøgda Formation replaces the Vardebukta and Sticky Keep Formations of Buchan et al. (1965) and the lower part of the Barentsøya Formation of Lock et al. (1978) as extended geographically by Mørk, Knarud et al. (1982) in central Spitsbergen, Barentsøya and Edgeøya. The formation consists of three member: the Deltadalen Member (composed of mudstones with sandstones and siltstones), the Lusitaniadalen Member (dominated by mudstones with thin siltstone beds and some limestone concretions) and the Vendomdalen Member (composed of dark shales with dolomite interbeds and nodules). The Lusitaniadalen and Vendomdalen members replace the former Sticky Keep Formation/ Member in the siirne areu. The Vikinghøda Formation can be followed through central and eastern Spitsbergen to Barentøya and Edgeøya and includes all sediments between the chert-rich Kapp Starostin Formation (Permian) and the organic-rich shales of the Botneheia Formation (Middle Triassic). The subdivision into three members is also reflected in the organic carbon content and palynofacies. Upwards, each succeeding member becomes more distal, organic-rich and oil-prone than the one below. The Vikinghøda Formation is well-dated by six ammonoid zones, although the transitional beds between the Deltadalen and Lusitaniadalen members lack age diagnostic macrofossils. Corresponding palynozonation and magnetustratigraphy have also been determined. The overall stratigraphical development correlates well with other key Triassic areas in the Arctic, although intervals in the late Dienerian and early Smithian may be condensed or missing.

Material from shallow cores drilled through the uplifted and truncated deposits near the Svalis Dome in the Barents Sea contains Lower and Middle Triassic palynomorphs and ammonoids. Eight miospore assemblage zones have been established in this paper, and six of them are calibrated by ammonoids: Svalis‐1 is dated by ammonoids of the late Griesbachian commune Zone. The assemblage is recovered from the Havert Formation overlying the Permian limestone. Svalis‐2 is dated by ammonoids to the late Smithian tardus Zone. The deposits belong to the lower and middle parts of Klappmyss Formation. The unit represents the transgressive systems tract of a Smithian‐early Spathian T‐R Sequence. Svalis‐3 is recorded from the youngest part of Klappmyss Formation which is missing age conclusive faunal evidence. The palynological assemblage is correlated as early Spathian in age. The deposits represent the regressive systems tract of the Smithian‐early Spathian T‐R Sequence. Svalis‐4 is recovered from rocks deposite...

The Triassic ammonoid Czekanowskites rieberi displays a covariation of morphological charac ters, which is rather common in ammonoids. Its morphological spectrum ranges from laterally compressed, involute, weakly ribbed forms to depressed, semiinvolute, strongly ribbed forms. In order to study this covariation, fifteen axially cut specimens have been analyzed by means of image analysis, which allows us to obtain the ontogenetic record of radii, area and perimeter of the individual whorl cross-sections. A logarithmic model of growth has been applied. Our data indicate that, owing to the covariation, the radii from the origin to the venter and to the umbil ical seam of a given whorl section vary inversely in order to maintain the relative position of the center of gravity of the whorl cross-section both throughout the ontogeny of single specimens and within the population. This influences hydrostatic parameters, such as the position of the center of mass and the orientation and stability of the shell. Since the ontogenetic record of the angular length of the body chamber is not known, we have calculated those hydrostatic varia bles using two mutually exclusive assumptions: (1) the angular length of the body chamber was constant throughout ontogeny and (2) the volume of the body chamber grew monotonically with the revolution angle. Fluctuations of the three hydrostatic variables were always less important in the first assumption. In any case, the spectrum of, for example, theoretical orien tations is comparable to those observed in the species of present-day Nautilus. The range of adult body-chamber length observed in C. rieberi is much narrower than the theoretical adult body-chamber length calculated under the second assumption which indicates that a certain control over this parameter existed in the natural population, probably in order to maintain a narrow range in orientation and stability. The excess or deficit in soft-body weight was probably compensated by inverse variations in shell-wall weight. The main conclusion is that, despite the extreme morphological variability, hydrostatic and, possibly, hydrodynamic properties of the population remained within narrow limits.

Die ersten Funde fossiler Ciliaten werden aus der Unter-Trias (Oberes Spathium) von Spitzbergen beschrieben. Die ehemals aus Pseudochitin bestehenden Gehause der Ciliaten sind fruhdiagnetisch in Apatit umgewandelt worden und so erhalten geblieben. Die fossilen Formen (Triadopercularia spitzbergensis n.g. n.sp. undTriacola ostracodarum n.g. n.sp.) gehoren zur Ciliaten-Ordnung Peritrichida (Sessilia) und konnen aufgrund ihrer Gehause-Morphologie in rezente Familien eingeordnet werden. Auf den ungewohnlichen Ablauf der Fossilisation, der zur Erhaltung der zarten, winzigen Formen fuhrte, und auf die palaobiologische Deutung der Funde wird speziell eingegangen.

The ammonoid species Czekanowskites rieberin.sp. from the Lower Anisian of Arctic Siberia (River Olenek) shows an enormous range of intraspecific variability. The 700 investigated specimens are packed in one single concretion. They are all adult with preserved living chambers and apertural structures. Morphologically they range from keeled smooth suboxycones with narrow umbilicus, through feebly ribbed platycones with a little wider umbilicus, to subcadicones with relatively wide umbilicus and straight ribs with bullae. The morphological variation is continuous; all specimmh belong to a single genetically linked population, variants of one biospecies. This phenomenon, which is quite common in boreal Triassic ammonoid faunas, has in the past led to serious taxonomic oversplitting. It presents a serious challenge to current ideas about a close correlation between modeof life and shell morphology in arnmonoids.□Amntonoidea, boreal Triassic, ecology. Siberia, variability.

Extraordinarily well-preserved ammonoids from the Boreal Triassic of Svalbard and NE-Siberia are described, in which the original aragonite of the shell had been replaced by apatite during very early stages of diagenesis. Because of subsequent calcite cementation of the phragmocones, it is possible to dissolve the chamber contents. This allows three-dimensional observations at different ontogenetic stages. The most remarkable features, however, are preserved organic sheets in the ammonoid phragmocones which are normally readily destroyed. Nearly all specimens examined show phosphatized membranes lining the septal surfaces and the inner shell wall. These membranes are most probably homologous to thin protein layers in the phragmocone of the recentNautilus, where they are termed the pellicle. They play an important part in the buoyancy control when the chamber liquid is no longer in direct contact with the siphuncular tube. In a number of specimens, a complicated system of formerly organic sheets which close off single compartments from the main chamber volume are preserved within the phragmocone. Depending on type and position of these layers in an ammonoid chamber, three different groups may be distinguished: 1. siphuncular sheets, 2. transverse sheets, and 3. horizontal sheets. The interpretation of the presence of these sheets leads to new conclusions concerning the functional morphology of the shell, especially related to questions of buoyancy, locomotion, and mode of life. Descriptions of similar structures within Permian goniatitids and Volgian ammonites indicate, that cameral sheets are not restricted to our Triassic species, but are a more general feature. They were probably present in most ammonoids, but have rarely been preserved.

This collection of papers on the Boreal Triassic grew from a conference in 2002, which was initiated as part of the networking activities linked to the International Geosciences Project (IGCP) 467—Triassic Time and Trans-Panthalassa Correlations—from an original suggestion by Mark Hounslow and Mike Orchard of the International Union of Geological Sciences Subcommission on Triassic Stratigraphy. The aim of the conference was to provide insight on improved Low- to High-Latitude correlations, and a greater regional understanding of the Arctic Triassic successions. Around 30 participants were expected, in part drawn by the prospect of visiting Spitsbergen and its Triassic outcrops—a once in a lifetime opportunity for many.

An integrated biomagnetostratigraphic study of the latest Early Triassic to the upper parts of the Middle Triassic, at Milne Edwardsfjellet in central Spitsbergen, Svalbard, allows a detailed correlation of Boreal and Tethyan biostratigraphies. The biostratigraphy consists of ammonoid and palynomorph zonations, supported by conodonts, through some 234 m of succession in two adjacent sections. The magnetostratigraphy consists of 10 substantive normal— reverse polarity chrons, defined by sampling at 150 stratigraphic levels. The magnetization is carried by magnetite and an unidentified magnetic sulphide, and is difficult to fully separate from a strong present-day-like magnetization. The biomagnetostratigraphy from the late Olenekian (Vendomdalen Member) is supplemented by data from nearby Vikinghogda. The early and middle Anisian has a high sedimentation rate, comprising over half the ca. 140-m thickness of the Botneheia Formation, whereas the late Anisian and lower Ladinian is condensed into about 20 m. The two latest Boreal Ladinian ammonoid zones are absent as a result of erosional truncation below the Tschermakfjellet Formation. Correlation with Tethyan biomagnetostratigraphies shows the traditional base of the Boreal Anisian (base of the Grambergia taimyrensis Zone) precedes the base of the Anisian (using definitions based on the De? sli Caira section in Romania). The Boreal upper Anisian Gymnotoceras rotelliforme and Frechites nevadanus ammonoid zones correlate with most of the Tethyan Pelsonian and Illyrian substages. The base Ladinian defined in the Tethyan global boundary stratotype and point (GSSP) is closely equivalent to the traditional base of the Boreal Ladinian at the Intornites oleshkoi Zone. The latest Olenekian—early Anisian magnetic polarity time scale is refined using the Spitsbergen data.

Investigations on ammonoid assemblages from the boreal Triassic of NE-Siberia and Spitsbergen allow to give information on ecology. Special attention is drawn to the enormous, intraspecific variation and its consequences for ammonoid ecology and taxonomy.

Die Schriftleitung der Pal~iontologischen Zeitschrift wies uns auf die M6glichkeit einer Erwiderung auf den Diskussionsbeitrag von Herrn G.E.G. WESTEnMANN (Hamilton, Ontario) beziiglich unserer Publikation ,,Organic components in phragmocones of Boreal Triassic ammonoids .... , Pal~iont. Z. 65: 269-303 (1991) hin. Wir sind diesem Angebot erst nach einigem Z6gern nachgekommen, da wir derartige ,,Diskussionen,, weder fiir zeitgem~if~ noch fiir nutzbringend erachten. Basiert doch die gesamte These von Herrn WESTEnraANN darauf, dat~ er nicht >,glauben,, kann, daf~ es sich bei den von uns beschriebenen phosphatisierten Lamellen in Ammonoideen-Phragmokonen um Ausscheidungen des Mantel-Epithels handelt. Er halt diese Strukturen f/Jr mehr ,,zufiillige, daher unregelm~it~ige Bildungen,, und deutet sie als ,,Riickst~inde von getrocknetem Kammer-Gel,,. Die sich daran anschliet~ende ,Diskussion

Four types of septal necks are present in the Ammonoidea: (1) retrochoanitic (entirely projected adapically), (2) modified retrochoanitic (projected adorally or both adorally and adapically on the dorsal side and adapically on the ventral side), (3) amphichoanitic (projected both adorally and adapically), and (4) prochoanitic (entirely projected adorally). Each septal neck is continuous with the rest of the septum and consists primarily of a nacreous layer. A spherulitic-prismatic deposit called the auxiliary deposit commonly appears on the adoral side of the septal neck and covers the inner surface of the nacreous layer. Another spherulitic-prismatic deposit (cuff) may also occur on the adapical side of prochoanitic necks. In all of the Paleozoic suborders except Goniatitina (Prolecanitina, Bactritina, Anarcestina, Agoniatitina, Clymeniina, Gonioclymeniina and Tornoceratina), type 1 necks are present throughout ontogeny (1→1). In the Goniatitina as well as in the Ceratitina, type 1 necks either persist throughout ontogeny (1→1) or develop into type 2 necks (1→2). In the Phylloceratina, type 1 necks are present in early to middle ontogeny, later developing into type 3 necks (1→3). In the Lytoceratina, type 1 necks are only present in very early ontogeny and are immediately replaced by type 4 necks (1→4). In the Ancyloceratina and Ammonitina (with few exceptions), only type 4 necks occur (4→4). Type 1 necks evidently represent the primitive condition. Variation among suborders in the ontogenetic timing of the transformation from the primitive condition to one of the three more derived conditions may be the result of heterochronic processes such as acceleration or predisplacement. However, the pattern of septal neck transformation within suborders is more or less stable and was probably established at the time each suborder originated.

Aus der Unter-Trias (Spathian) von W. Spitzbergen wird eine neue Ostracoden-Sub-familie Triadocypridininae (O. Myodocopida) beschrieben. Samtliche 60 vorliegenden Exemplare sind zweiklappig erhalten. Die ehemals aus Calciumkarbonat bestehende Schalensubstanz ist sekundar in Apatit umgewandelt. Bei einem Teil der Exemplare sind auch die chitinigen Weichkorper-Anhange phosphatisiert und so z.T. hervorragend erhalten geblieben. Neben Teilen der ersten und zweiten Antenne konnten in vielen Fallen die Atemplatte der Maxille und der als Putzfus umgebildete zweite Thorakopode nachgewiesen werden. Einige Exemplare zeigen charakteristische dreilappige Kiemenpaare, die beiderseits am Hinterende des Korpers ansetzen. Bei einer einzigen Form ist sogar das Lateralauge erhalten geblieben. Die hier erstmals fossil beschriebenen Weichkorper-Strukturen sind mit denen der rezenten Vertreter dieser Familie nahezu identisch. Die Fossilisationsbedingungen und die Phosphatisierung, die zu der ausergewohnlichen Erhaltung gefuhrt haben, werden diskutiert.

A b s t r a c t: The present state of knowledge concerning the function of anaptychi, aptychi, and opercula of ammonoids is reviewed. The jaw apparati found associated with the lytoceratid genera Gaudryceras and Tetragonites by KANI~ et al. (1978) and TANABE et al. (1980) and classified as rhynchaptychus type of ammonoidjaws by L~HMANN (1981) are re-interpreted. Morphologically, they are very similar to Nautilus jaws. Their interpretation as allochthonous nautiloid jaws is discussed and considered probable. However, beccublast cell impressions in Gaudryceras and recent Nautilus differ considerably. Further investigations are deemed necessary concerning a) the nature of the anaptychi in Palaeozoic anaptychus assemblages, whether they are opercula or jaw elements; b) the function of the laevaptychi. Their jaw nature is still open to doubt; c) the autochthony of the rhynchaptychus-type lower jaws found in lytoceratid Upper Cretaceous ammonites in Japan.

Weichteilreste in Wohnkammern der AmmonitengattungenArnioceras, Hildoceras, «Oppelia» undPhysodoceras werden beschrieben. Dabei wird besonders auf den Kropfinhalt und daraus folgernd auf die Ernahrungsweise der Ammoniten eingegangen. Die Analyse unserer Funde zeigt, das Foraminiferen, Ostracoden, kleine Ammoniten und Seelilien gefressen wurden.

Nine transgressive-regressive (T-R) cycles have recently been recognized in the Triassic succession of the Sverdrup Basin, Arctic Canada (Embry, 1988). The transgressions which initiated the cycles are dated as earliest Griesbachian, earliest Smithian, late Smithian, earliest Anisian, early Ladinian, earliest Carnian, mid-Carnian, earliest Norian, latest Norian and earliest Jurassic.