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Post-depositional migration of elements during diagenesis in brown clay and turbidite sequences in the northeast Atlantic
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D. Submarine Geology and Geophysics
those species, 'time scales of 103-10~ years may encompass so few generations that evolutionary processes...may be completely inhibited.' This hypothesis may explain the observed scarcity of recently evolved species among these corals and the extensive intraspecific variation. The environmental instability also may have accelerated speciation among corals with shorter generation times. Biol. Dept., Univ. of Calif. Santa Cruz, Calif. 95064, USA. (msg)
DI20. Sedimentary processes (deposition, diagenesis, etc.) 84:6078 Colley, S., J. Thomson, T.R.S. Wilson and N.C. Higgs, 1984. Post-depositional migration of elements during diagenesis in brown clay and turbidite sequences in the northeast Atlantic. Geochim. cosmochim. Acta, 48(6): 1223-1235. In one core, a long turbidite section emplaced 330 kya is overlain by clay. Organic oxidation apparently has proceeded downward from the turbidite top, maintaining a U concentration peak below the oxidation front marked by a colour change. Vanadium and Cu behave similarly, but upward migration of the redox-sensitive metals Mn and Ni is seen. In the second core an 8 cm turbidite section was emplaced ~170 kya in a clay column. Organic consumption appears complete, but evidence for diagenetic effects is found in a 16 cm compositional alteration 'halo' of the underlying pelagic clay. Fe(II) has been enriched and the hydrogenous component of Mn, Co, Ni and Cu removed from the pelagic clay to form the halo. Inst. of Oceanogr. Sci., Brook Rd., Wormley, Godalming, Surrey GU8 5UB, UK. 84:6079 Manheim, F.T., 1981/82. Geochemistry of mangauese carbonates in the Baltic Sea. Stockh. Contr. Geol., 37:145-159.
Anomalous carbonate-enriched sediments reported (Munthe 1894) in deep basins of the Baltic Sea have been found to contain Mn-enriched carbonates of a previously unknown kind. These carbonates are preferentially deposited in the finest-grained, organic-rich Holocene sediments. Precipitation of these carbonates is triggered by excess Ca released from underlying sediments by exchange reactions due to encroachment of saline pore fluid on clayey glacial lake (Ancylus) sediments. USGS, Woods Hole, Mass. 02543, USA.
OLR (1984) 31 (12).
84:6080 McCoy, F.W., D.J. Stanley (comments), S.R. Troelstra, G.T. Klaver, H.U ten Haven and D. Jongsma (reply), 1984. Matters arising. [Discussion of] formation of sapropels in the Tyro Basin. Nature, Lond., 309(5970):727-728. 84:6081 Morris, R.J., M.J. McCartney and P.P.E. Weaver, 1984. Sapropelic deposits in a sediment from the Guinea Basin, South Atlantic. Nature, Lond., 309(5969):611-614. Sapropelic layers (>0.5% organic carbon) have been discovered in a recent sediment core from a deep-water site in the Guinea Basin. It is thought most unlikely that stagnant conditions could prevail in the water column at this site. Preliminary analyses suggest that the organic-rich deposits are a direct result of increased productivity in the overlying water column, the most recent occurring ~ 18,000 yr ago and coinciding with the last glacial maximum. Inst. of Oceanogr. Sci., Brook Rd., Wormley, Godalming, Surrey GU8 5UB, UK.
DI30. Sediments (rocks, formations, type, composition, etc.) 84:6082 Chen, Min-Pen, 1983. Physical properties and depositional environments of continental slope sediments, southern Talwan Strait. Acta oceanogr. taiwan., 14:42-63. (In Chinese, English abstract.) 84:6083 Eyles, C.H. and Nicholas Eyles, 1984. Giaciomarine sediments of the Isle of Man as a key to Late Pleistocene stratigraphic investigations in the Irish Sea Basin. Geology, geol. Soc. Am., 12(6): 359-364. Dept. of Geol., Univ. of Toronto, Toronto, Ont. M5S 1A3, Canada. 84:6084 Lazur, Yu.M., I.M. Varentsov and V.V. Yermilov, 1984. Volcanogenic copper and zinc minerals of Early Cretaceous deposits in the central northwestern Pacific, Deep Sea Drilling Project, Leg 62. Chemic Erde, 43(2): 129-137.
The typical mineral forms of heavy metals were finely dispersed sulphides of Fe, Cu and Zn. The native alloys of Cu + Zn (orichalch) were less important; they are present in the volcanoclastic components and formed during the reduction stage of basalt evolution. Fe, Cu and Zn sulphides were formed during postsedimentary transformations of sediments enriched in organic matter and in metals
D. Submarine Geology and Geophysics
those species, 'time scales of 103-10~ years may encompass so few generations that evolutionary processes...may be completely inhibited.' This hypothesis may explain the observed scarcity of recently evolved species among these corals and the extensive intraspecific variation. The environmental instability also may have accelerated speciation among corals with shorter generation times. Biol. Dept., Univ. of Calif. Santa Cruz, Calif. 95064, USA. (msg)
DI20. Sedimentary processes (deposition, diagenesis, etc.) 84:6078 Colley, S., J. Thomson, T.R.S. Wilson and N.C. Higgs, 1984. Post-depositional migration of elements during diagenesis in brown clay and turbidite sequences in the northeast Atlantic. Geochim. cosmochim. Acta, 48(6): 1223-1235. In one core, a long turbidite section emplaced 330 kya is overlain by clay. Organic oxidation apparently has proceeded downward from the turbidite top, maintaining a U concentration peak below the oxidation front marked by a colour change. Vanadium and Cu behave similarly, but upward migration of the redox-sensitive metals Mn and Ni is seen. In the second core an 8 cm turbidite section was emplaced ~170 kya in a clay column. Organic consumption appears complete, but evidence for diagenetic effects is found in a 16 cm compositional alteration 'halo' of the underlying pelagic clay. Fe(II) has been enriched and the hydrogenous component of Mn, Co, Ni and Cu removed from the pelagic clay to form the halo. Inst. of Oceanogr. Sci., Brook Rd., Wormley, Godalming, Surrey GU8 5UB, UK. 84:6079 Manheim, F.T., 1981/82. Geochemistry of mangauese carbonates in the Baltic Sea. Stockh. Contr. Geol., 37:145-159.
Anomalous carbonate-enriched sediments reported (Munthe 1894) in deep basins of the Baltic Sea have been found to contain Mn-enriched carbonates of a previously unknown kind. These carbonates are preferentially deposited in the finest-grained, organic-rich Holocene sediments. Precipitation of these carbonates is triggered by excess Ca released from underlying sediments by exchange reactions due to encroachment of saline pore fluid on clayey glacial lake (Ancylus) sediments. USGS, Woods Hole, Mass. 02543, USA.
OLR (1984) 31 (12).
84:6080 McCoy, F.W., D.J. Stanley (comments), S.R. Troelstra, G.T. Klaver, H.U ten Haven and D. Jongsma (reply), 1984. Matters arising. [Discussion of] formation of sapropels in the Tyro Basin. Nature, Lond., 309(5970):727-728. 84:6081 Morris, R.J., M.J. McCartney and P.P.E. Weaver, 1984. Sapropelic deposits in a sediment from the Guinea Basin, South Atlantic. Nature, Lond., 309(5969):611-614. Sapropelic layers (>0.5% organic carbon) have been discovered in a recent sediment core from a deep-water site in the Guinea Basin. It is thought most unlikely that stagnant conditions could prevail in the water column at this site. Preliminary analyses suggest that the organic-rich deposits are a direct result of increased productivity in the overlying water column, the most recent occurring ~ 18,000 yr ago and coinciding with the last glacial maximum. Inst. of Oceanogr. Sci., Brook Rd., Wormley, Godalming, Surrey GU8 5UB, UK.
DI30. Sediments (rocks, formations, type, composition, etc.) 84:6082 Chen, Min-Pen, 1983. Physical properties and depositional environments of continental slope sediments, southern Talwan Strait. Acta oceanogr. taiwan., 14:42-63. (In Chinese, English abstract.) 84:6083 Eyles, C.H. and Nicholas Eyles, 1984. Giaciomarine sediments of the Isle of Man as a key to Late Pleistocene stratigraphic investigations in the Irish Sea Basin. Geology, geol. Soc. Am., 12(6): 359-364. Dept. of Geol., Univ. of Toronto, Toronto, Ont. M5S 1A3, Canada. 84:6084 Lazur, Yu.M., I.M. Varentsov and V.V. Yermilov, 1984. Volcanogenic copper and zinc minerals of Early Cretaceous deposits in the central northwestern Pacific, Deep Sea Drilling Project, Leg 62. Chemic Erde, 43(2): 129-137.
The typical mineral forms of heavy metals were finely dispersed sulphides of Fe, Cu and Zn. The native alloys of Cu + Zn (orichalch) were less important; they are present in the volcanoclastic components and formed during the reduction stage of basalt evolution. Fe, Cu and Zn sulphides were formed during postsedimentary transformations of sediments enriched in organic matter and in metals