Mo-clay Research Articles

New stalked and sessile cirripedes from the Eocene Mo Clay, northwest Jutland (Denmark)

ABSTRACT New taxa of thoracican cirripedes are recorded from the Eocene Mo Clay of northwest Jutland, Denmark, namely Stipilepas molerensis Carriol n. gen., n. sp., a scalpelliform gooseneck barnacle, and Plesiobrachylepas jutlandica Carriol n. gen., n. sp., a brachylepadomorph sessile form. This material is of importance in that the former not only represents the first extinct example of the tribe Ashinkailepadini, it also is the second fossil neolepadine, while the latter adds to the diversity of the family Brachylepadidae, which previously embraced only three genera. The geological context of these taxa is outlined and their phylogenetic interest discussed.

TWO NEW PARROTS (PSITTACIFORMES) FROM THE LOWER EOCENE FUR FORMATION OF DENMARK

Abstract: Two new fossil psittaciform birds from the Lower Eocene ‘Mo Clay’ (Fur Formation) of Denmark (c. 54 Ma) are described. An unnamed specimen is assigned to the extinct avian family of stem‐group parrots, Pseudasturidae (genus and species incertae sedis), while a second (Mopsitta tanta gen. et sp. nov.) is the largest fossil parrot yet known. Both specimens are the first fossil records of these birds from Denmark. Although the phylogenetic position of Mopsitta is unclear (it is classified as family incertae sedis), this form is phylogenetically closer to Recent Pstittacidae than to other known Palaeogene psittaciforms and may, therefore, represent the oldest known crown‐group parrot.

Paleogene volcanic ash layers in the Danish Basin: compositions and source areas in the North Atlantic Igneous Province

The Paleogene mo clay basin in Denmark contains ca. 200 layers of mostly well-preserved volcanic ash. Of these, ca. 77 layers have been analysed for major and trace elements by X-ray fluorescence spectrometry (XRF), 22 for rare-earth elements (REE), and 11 for Sr and Nd isotopes. The ‘negative’ ash series (layers −39 to −1) comprise tholeiitic basalt, crustally contaminated trachyte, and rhyolite; alkaline basalt, trachybasalt, trachyte, and rhyolite; and Ti-rich nephelinite and phonolite. The ‘positive’ ash series (layers +1 to +140) comprise enriched tholeiitic ferrobasalt and two rhyolite layers. The ferrobasalts form one comagmatic group; however, oscillations are seen up-section between less-enriched and more-enriched compositions, as indicated by variations in Zr/Nb, REE contents, and isotope compositions, suggesting heterogeneities in the mantle source. Two samples of Eocene ash from Greifswalder Oie in northern Germany are identical to the positive series ashes. By comparison of the ash compositions with other rocks from the North Atlantic Igneous Province, probable source areas can be identified. Four stages of deposition can be distinguished. In stage 1 (layers −39 to −22), basalts and rhyolites were sourced from centres on the NW European shelf. In stage 2 (layers −21b to −15), trachytes and rhyolites were still sourced from centres on the shelf, whereas the strongly alkaline layers could all have originated in the Gardiner Complex in East Greenland. In stage 3, alkali basalts (layers −13 to −11) may be the products of a failed or propagating part of the opening oceanic rift. In stage 4 (layers +1 to +140), we suggest that the comagmatic suite of voluminous ferrobasalts were sourced from a gigantic volcanic system representing the nascent Proto-Iceland within the opening ocean. The cataclysmic character of stage 4 can be understood if the areas of extremely high magma production associated with the Proto-Icelandic mantle plume, which had until then produced the large subaerial flood basalts in Greenland, at this time moved away from the continent and into the sea-covered opening rift, thus switching the bulk of volcanism from effusive to explosive. When Proto-Iceland finally emerged, the explosive activity abated again.

Insekten aus der Fur-Formation von Dänemark (Moler, ob. Paleozän / unt. Eozän?) 8. Zwei neue Vertreter der Chrysopidae (Neuroptera)

Insekten aus der Fur-Formation von Dänemark (Moler, ob. Paleozän / unt. Eozän?) 8. Zwei neue Vertreter der Chrysopidae (Neuroptera)

Clay Mineralogy of some Lower Tertiary (Paleogene) Sediments from Denmark

108 samples from the Paleogene rocks of Denrnark were examined by standard X-ray techniques and their clay suites form the basis of the present study. The X-ray data have permitted a three-fold mineralogical zonation of the Danish Paleogene.The oldest zone (Zone I) is characterized by a high montmorillonite content, minor or trace amounts of illite and segregated mixed-layer clay minerals and the absence of kaolinite. The boundaries of Zone I coincide with the Paleocene Series. The clay minerals are detrital and are derived from a carbonate terrain bordering the Fennoscandian massif. Diagenetic changes in the marine environment and segregation by sorting and floculation are important factors accounting for the high montmorillonite content.A middle zone (Zone Il) is characterized by the predominance of amorphous material. Minor amounts of montmorillonite, illite and kaolinite are present and represent alteration produets of volcanic ash. Zone II is restricted to the Mo Clay Formation.The youngest zone (Zone III) contains variable amounts of montmorillonite, illite, kaolinite and random mixed-layer montmorillonite-illite. The boundaries of Zone III appear to extend from the lower Eocene to the Miocene. The clay minerals of Zone III are products of the alteration of the volcanic material of the Fennoscandian massif. Changes in the conditions of the source area and the physical environment of deposition account for the mineralogical variations.