No abstract

. Magma influx and mixing in the Bjerkreim-Sokndal layered intrusion, South Norway: evidence from the boundary between two megacyclic units at Storeknuten. Lithos, 29:311-325.The Bjerkreim-Sokndal layered intrusion belongs to the Proterozoic anorthositic province in the Rogaland area of southern Norway. The northwestern part of the intrusion comprises a ca. 6 km-thick Layered Series made up of megacyclic units (MCU) arranged in a syncline; each megacyclic unit reflects the influx of fresh magma into the chamber. The boundary between megacyclic units III and IV has been studied in detail at Storeknuten on the southern flank of the syncline. The megacyclic units can be subdivided into a series of cumulate stratigraphic zones; the interval from the top of zone IIIe to the base of zone IVd is exposed in the Storeknuten area. Modally layered plagioclase-hypersthene-ilmenite-magnetite-augite-apatite cumulates belonging to zone IIIe are overlain by 30 m of massive plagioclase-rich rocks (commonly containing ilmenite and/or hypersthene) constituting zone IVa. The entry of cumulus olivine defines the base of zone IVb (dominantly plagioclase-olivine-ilmenite cumulates) which is about 100 m thick. Many of the olivines are partly or completely replaced by Ca-poor pyroxene/Fe-Ti oxide symplectites. This massive leucotroctolitic zone is overlain by modally layered, laminated plagioclasehypersthene-ilmenite cumulates of zone IVc. The successive entry of magnetite, apatite (accompanied by Ca-rich pyroxene) and inverted pigeonite defines zones IVd, e and f respectively. The entry of Kfeldspar (accompanied by Fe-rich olivine) defines the base of a jotunitic transition zone which passes upwards into mangerites and quartz mangerites.There is a compositional regression through zone IVa. The upper part of zone IIIe has Ca-poor pyroxene with about En68, plagioclase with An44-48 and a Sr-isotope ratio of about 0.7062, while the base of zone IVb has olivine with Fo75 together with En78, An53 and 0.7050 respectively. Similar reversals are shown by the minor element compositions of plagioclase and Fe-Ti oxides. Sr-isotope ratios increase systematically up through zone IVb (reaching 0.7058 in zone IVd) while An% and Sr in plagioclase and Ni and Cr in Fe-Ti oxides decrease. Olivine compositions vary unsystematically and are believed to have changed their Fe:Mg ratios as a result of trapped liquid shift.The magma residing in the chamber when the influx at the base of megacyclic unit IV took place was compositionally zoned, and assimilation of gneissic country rock at the roof had resulted in the St-isotope ratio increasing up through the magma column. The new magma had a Sr-isotope ratio of about 0.7050 while the resident magma had a ratio of 0.7062 at the floor, increasing upwards. The new magma mixed with the basal layer(s) of the compositionally zoned resident magma and crystallization of this hybrid magma during influx and mixing produced the compositional regression in zone IVa. When magma influx

Jensen, J . C. 1984. On the polarization and innervation of the pars inferior sensory epithelia of the herring labyrinth. (Zoological Laboratory, University of Aarhus, Denmark.) -Acta 2001. (Stockh.) 65, 61-74.The macula sacculi and the macula lagenae of the herring, Clupea harengus L., were examined by light microscopy. the macula lagenae is large compared ti1 what is normal among non-ostariophysan fishes. the morphological polarization of the hair cells in the inferior maculae shows a pattern which is similar to that usually seer; in teleoit fishes. The fibres in the nerves supplying the macula sacculi and the macula lagenae were counted and their diameters measured. The ramulus saccularis is divided in two separate ramuli innervating populations of hair cells with different morphological polarization. The saccular rostra1 nerve trunk contains 180CL2300 fibres, with 1300-1800 fibres in the caudal nerve trunk. The lagenar nerve is composed of 2100-4000 fibres. The fibre diameters are 1-14 pm in all ramuli. Silver staining of the nerve axoplasm reveals a unique differentiation of the maculae, which can be divided into a central area surrounded by a peripheral part.

Jensen, J. C. 1994. Structure and innervation of the inner ear sensory organs in an otophysine fish, the upside-down catfish (Synodontis nigriventris David).-Acta Zoologica (Stockholm) 75: 14S160.All the sensory epithelia of the inner ear in the upside-down catfish (Synodontis nigriventris David) were examined by light microscopy. The morphology of the membranous labyrinth and the orientation of the hair cells is similar to what has been found in other otophysine fishes. The sensory cells are of variable size both inter-and intraepithelially; particularly the macula sacculi is equipped with heterogeneous receptors. Regional differences in the hair cell density are presented for all the otolith organs plus the papilla neglecta. Nerve stainings reveal regional differentiation. The central areas are innervated by stout and stubbly nerve endings intermingled with a few thin nerve fibres while the peripheral parts are reached exclusively by thin axons. In the anterior region of the macula sacculi are found unique cup-shaped axon terminations which surround the basal parts of a single or a few sensory cells. The number and diameter range of the myelinated nerve fibres as well as the hair celVaxon ratio are presented. Electron microscopy demonstrates the presence of unmyelinated axons in all inner ear nerve ramuli.