Eckart Håkansson

Wandel Sea Basin — The North Greenland equivalent to Svalbard and the Barents Shelf

Recent investigations of the North Greenland Wandel Sea Basin confirm, to a large extent, previous assumptions of a parallel development with Svalbard and the Barents Shelf. Deposits from the Wandel Sea Basin have now been recorded in a coastal belt in North Greenland almost 500 km in length, but in many parts their distribution is limited and/or highly patchy. A composite sequence totalling well over 7 km has been recorded, which gives evidence for a complex depositional and structural history of the basin encompassing the Carboniferous to Tertiary interval. Depositional environments in the Carboniferous to Triassic, as well as in the Palaeocene, compare well with the situation recorded in Svalbard. The later Mesozoic history of the two areas deviates to varying degrees, and there is some evidence that the North Greenland development may be more closely paralleled in the Barents Shelf area than in onshore Svalbard. Late Jurassic to early Cretaceous deposition testifies to the separation of smaller basin units; however, the presence of thick late-Cretaceous on-shore sequences in North Greenland constitutes the most conspicuous difference from Svalbard. During the late Cretaceous, several pull-apart basins were filled and deformed in a dextral strike-slip mobile belt, largely paralleling the subsequent suture between Greenland and Svalbard. The type of deposition in individual basins varies widely. Some contain fluvial-deltaic and marine sediments whereas a single basin is dominated by continental vulcanogenic sediments and extrusives. Severe post- Palaeocene thermal alteration centrally in the Wandel Sea Basin constitutes the last major event so far recorded in North Greenland.

Jurassic and Cretaceous palaeogeography and stratigraphic comparisons in the North Greenland-Svalbard region

We present sedimentological comparisons and stratigraphical correlations of the Jurassic and Cretaceous epicontinental shelf deposits of Svalbard and updated descriptions of the shallow-marine North Greenland sediments of East Peary Land and Kronprins Christians Land (Kilen). The Callovian to Volgian Agardhfjellet Formation of Svalbard is correlated to the lower part of the Ladegårdsåen Formation on East Peary Land, and to the Birkelund Fjeld, Splitbæk, and Kuglelejet formations of Kronprins Christian Land (Kilen). The Berriasian to Hauterivian Rurikfjellet Formation (Svalbard) correlates with the Dromledome and Lichen Ryg formations from Kilen and the middle part of the Ladegårdsåen Formation from East Peary Land. The Galadriel Fjeld Formation from Kilen and the upper part of the Ladegårdsåen Formation (East Peary Land) are comparable to the Helvetiafjellet and Carolinefjellet formations of Svalbard. These comparisons between Svalbard and North Greenland are combined with stratigraphical information from neighbouring regions in palaeogeographical reconstructions. Five selected time slices are presented within a setting of the most recent plate tectonic reconstructions for the area.

Sexual versus asexual dispersal in clonal animals: examples from cheilostome bryozoans

The relative numbers of sexually and asexually recruited colonies and the proportion of brooding zooids were determined in 26 species of cheilostome bryozoans of Late Cretaceous and Early Tertiary ages. Asexual reproduction seems to be much more widespread than previously realized, although its relative importance is related to growth habit. Arborescent species of these fossil assemblages reproduce mainly asexually via fragmentation; encrusting species reproduce sexually via motile larvae. Free-living species use both methods; some reproduce sexually, whereas other species have enhanced the ability to break and reproduce predominantly asexually. Mode of reproduction was stable over a period of 3 m.y. in all species except the vinelike Columnotheca cribrosa. In this species both the proportion of asexual recruits and brooding zooids varied in accord with environmental parameters. In all cases populations dominated by asexual propagation had a significantly lower proportion of brooding zooids than populations dominated by sexual propagation.

First Permo-Carboniferous conodonts from North Greenland

Upper Palaeozoic conodonts are described for the first time from the North Greenland Wandel Sea Basin. In eastern Peary Land, the Moscovian species Idiognathodus incurvus and the Kasimovian—Gzhelian I. magnificus occur in the Upper Carboniferous Foldedal Formation, while an assemblage from the lower part of the succeeding Kim Fjelde Formation suggests deposition in the Upper Artinskian Neostreptognathodus pequopensis—N . clarki Zone. These datings confirm the existence in the northern part of the Wandel Sea Basin of the pronounced early Permian hiatus previously recognized in Holm Land and Amdrup Land in the southern part of the basin. The single conodont specimen found at Prinsesse Ingeborg Halvo further corrobates the local absence of this regional hiatus in the central part of the Wandel Sea Basin.