Intercalibration of Boreal and Tethyan timescales: the magneto-biostratigraphy of the Middle Triassic and the latest Early Triassic from Spitsbergen, Arctic Norway

An integrated bio-magnetostratigraphic 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 ten 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 bio-magnetostratigraphy from the late Olenekian (Vendomdalen Member) is supplemented by data from nearby Vikinghøgda. The early and mid-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 due to erosional truncation below the Tschermakfjellet Formation. Correlation to Tethyan bio-magnetostratigraphies shows the traditional base of the Boreal Anisian (base of G. taimyrensis Zone) precedes the base Anisian (using here definitions based on the Desli Caira section in Romania). The Boreal upper Anisian G. rotelliforme and F. nevadanus ammonoid zones correlate to 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 I. oleshkoi Zone. The latest Olenekian to early Anisian magnetic polarity timescale is refined using the Spitsbergen data

Intraspecific variation of Svalbardiceras spitzbergensis (Frebold) from the Early Triassic (Spathian) of Spitsbergen

The ammonoid species Svalbardiceras spitzbergensis from the latest Early Triassic (Spathian, subrobustus Zone) shows a remarkable intraspecific variation. The more than 400 specimens studied come from one fossiliferous carbonate nodule layer within a sequence of mudstones and clayey siltstones of the Vikinghøgda Formation (Vendomdalen Member), mainly collected in the Sassendalen and Agardhbugta areas in central and eastern Svalbard, respectively. The preservation of the ammonoids is very good, usually with preserved shells and complete body chambers. Morphologically they range from compressed, more or less smooth platycones, with narrow umbilicus, to wide umbilicate, depressed forms with straight, prominent ribs. The morphological variation is continuous: all specimens belong to a single assemblage, and are variants of one biospecies. This phenomenon, which is quite common in Boreal Triassic ammonoid faunas, has in the past led to serious taxonomic oversplitting. Furthermore, this new example presents a serious challenge to current ideas about the close correlation between mode of life and shell morphology of ammonoids

A review of the order Mantophasmatodea (Insecta)

The newly discovered insect order Mantophasmatodea, known from two Recent species in tropical Africa and some fossils in Baltic amber, is reviewed, with all the material currently known being listed. A new genus and species is described: Praedatophasma maraisi Zompro & Adis, n. gen., n. sp. Complete information available at present on habitats and the biology is given

Foreword to the special issue:The Boreal Triassic

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

Tasmanites algae—contributors to the Middle Triassic hydrocarbon source rocks of Svalbard and the Barents Shelf

When moving from west to east across Svalbard, organic geochemical, palynological and sedimentological data from the Middle Triassic dark shales of the Sassendalen Group show an improved quality of hydrocarbon source rock (kerogen type II/III), and an increased abundance of structured algal material, including Tasmanites. Triassic specimens of Tasmanites in palynological residues from Svalbard are generally of small size (500 mm in diameter) are recorded in silty shales and siltstones palynologically dated as being of Ladinian–Carnian age. Similar occurrences are also present in deposits of the Norwegian Barents Sea. Our organic geochemical analyses suggest that Tasmanites is a major source for the hydrocarbons encountered in these rocks. Tasmanites algae are also enriched in Ladinian–Norian deposits in Taimyr, Siberia. The development of a marine embayment, the direction of the ocean currents, the supply of clastic material and freshwater, and the palaeolatitude all show similarities to the conditions in the present Mediterranean, and adjacent Atlantic Ocean. Ecological conditions in the water column (light intensity, nutrient supply and temperature) are expected to have been similar, and favoured the growth and accumulation of Tasmanites. The accumulation of monotypic, large Tasmanites cells in silty shales is explained as a result of contemporaneous recirculation and sorting