Holocene humidity fluctuations in Sweden inferred from dendrochronology and peat stratigraphy

Tree-ring and peat stratigraphy data were examined back to 5000 BC in order to identify and compare humidity changes in Fennoscandia. The temporal variation in distribution of Scots pine ( Pinus sylvestris L.) was used as a measure of past lake-level fluctuations in central Sweden. The chronology, which spans 2893 BC–AD 1998 with minor gaps in AD 887–907 and 1633–1650 BC and with additional floating chronologies back to 4868 BC, was cross-dated and fixed to an absolute timescale using a chronology from Torneträsk, northern Sweden. The peat stratigraphy from the Stömyren peat bog, south-central Sweden, was transformed into humification indices to evaluate humidity changes during the past 8000 years. The peat chronology is established by four tephra datings and eight ¹⁴C datings. Synchronous periods of drier conditions, interpreted from regeneration and the mortality pattern of pine, tree-ring chronology and peat humification, were recognized at c. 4900–4800 BC, 2400–2200 BC, 2100–1800 BC, 1500–1100 BC, AD 50–200, AD 400–600 and AD 1350–1500. Possible wetter periods were encountered at 3600–3400 BC, 3200–2900 BC, 2200–2100 BC, 1700–1500 BC, 1100–900 BC, 100 BC-AD 50, AD 200–400, AD 750–900 and AD 1550–1700. The wet and dry periods revealed by the tree rings and peat stratigraphy data indicate considerable humidity changes in the Holocene.     

A standard profile for Littorina transgressions in western Skåne, South Sweden

The investigation is based on diatem- and pollen analyses of a main profile from the ancient lagoon Barsebäcksmossen. The chronology is bared on C¹⁴-^-dating.
Seven transgressions are indicated, viz. 5200–4800 B.C., 4600–4400 R.C., 4150–3900 B.C., 3800–3700 B.C., 3600–3500 B.C., 3100–2950 H.C. and 2050–1850 B.C. Thc trangressions 4150–3900 B.C., 3800–3700 B.C. and 3600–3500 B.C. may only represent fluctuations during a 'complex' transgresssion. The transgresssion in Barsebäcksmtrssen are correlated with the transgresssion established by Berglund in the Baltic Sea and by Mörner in the Kattegatt sea.
A change in the date of the pollen-zone boundary AT 1/AT 2 from 4500–4600 B.C. to 5200 B.C. is proposed.     

DRIFTlNG CONTINENTS AND COLLIDING PARADIGMS: PERSPECTIVES ON THE GEOSCIENCE REVOLUTION

1990, $35.00, xiii+286 pp, Indiana University Press, Bloomington. ISBN 0–253–35405–6.     

SCIENCE & THE NAVY: THE HISTORY OF THE OFFICE OF NAVAL RESEARCH

1990, xvi+142 pp., $24.95 (hbk) ISBN 0–691–07847–5 Princeton University Press, Princeton, NJ.     

Heavy Mineral Placer Deposits of Ekakula Beach, Gahiramatha Coast, Orissa, India

Abstract: Ilmenite, hematite, garnet, monazite, zircon, rutile, magnetite, sillimanite, pyroxene and amphibole from the beach sands of Ekakula, Gahiramatha coast, Orissa, India are reported here for the first time. Their total concentration varies from 26. 4 to 100%. Ilmenite, monazite and zircon are between 100 and 300 um in size and are well rounded in shape. Ilmenite-hematite intergrowth is common. Ilmenite has 50. 02–54. 73% TiO₂, 42. 42–46. 90% FeO (total Fe) and small amounts of Al, Mn, Mg, Ca, Ba, Si, V, Cr, and Zn. The bulk samples contain 10. 63–41. 42 % TiO₂, 6. 15–26. 07 % FeO, 5. 86–16. 75 % Fe₂O₃, 7. 41–61. 74 % SiO₂, 1. 39–12. 83% A1₂O₃, 0. 32–4. 97% CaO, 0. 53–4. 24% P₂O₅, 0. 17–3. 27% MgO, 0. 15–2. 97% Na₂O, 0. 07–2. 34% K₂O, and 0. 05–0. 71% V₂O₅ together with appreciable amounts of La, Ce, Pr, Nd, Sm, Eu, Y, U, Th, Zr, and trace amounts of Pb, Zn, Cu, Ni, Co, and Cr. Khondalite, charnockite, calc-silicate granulite, leptynite, migmatite, gneiss, basic granulite and pegmatite of the Eastern Ghats appear to be the major source for the above heavy mineral assemblages. The samples are amenable to gravity and magnetic methods of beneficiation.     

Recent and subrecent sedimentary conditions in the southern part of the North Sea–Baltic Sea transition

The recent rate of net sedimentation (0–5mm/yr) in the southern Kattegat is to a high degree governed by resuspension. In shallow areas (10–25 m) there is no or very little sedimentation. Sediments here are sandy lag sediments with a low content of organic matter (0.5–3.0%), nitrogen (0–0.1%) and phosphorus (0.01–0.05%). In deep water (30–60 m) the sediments are clays or fine silts and generally have high contents of organic matter (3.0–10.8%), nitrogen (0.1–0.34%) and phosphorus (0.05–0.10%). Shallow water sediments are relatively well sorted because of resuspension of fine material, which is transported to deeper water. Here the sorting becomes poor because relatively coarser material is supplied during exceptional storm events. Discrimination on erosion/transport bottoms and on depositional bottoms was based on resuspension calculations, grain-size parameters and Passegas (1964) CM diagrams. The IG/N ratio was an useful additional tool. From the sediment content of CaCO₃ it is suggested that recent sedimentation in the deeper parts of southern Kattegat is less influenced by contributions from the North Sea than it was during the early Holocene.     

熊耳山—外方山矿集区中生代Au-Mo成矿系统

熊耳山—外方山矿集区位于秦岭造山带之华北板块南缘,经历了复杂的碰撞造山过程,成矿时间跨度大,成矿强度高,成矿作用多样。复合造山过程和相应的成矿作用已被深入研究,但成矿系统的划分和叠加成矿作用尚需研究。本文将熊耳山—外方山矿集区发育的Au-Mo矿床划分为造山型Mo矿床、斑岩型Mo矿床、岩浆热液脉型Mo矿床、造山型Au矿床和岩浆热液型Au矿床5个类型,对应5种成矿系统：(1)造山型Mo矿床形成于250~227 Ma的同碰撞环境和227~194 Ma的后碰撞环境,为变质热液萃取壳源Mo成矿;(2)斑岩型Mo矿床形成于163~135 Ma的洋陆俯冲环境和135~116 Ma的岩石圈减薄环境,为岩浆热液携带幔源或壳源Mo成矿;(3)岩浆热液脉型Mo矿床形成于227~194 Ma的后碰撞环境,为岩浆热液携带幔源Mo成矿;(4)造山型Au矿床在三叠纪发生了预富集作用,主要形成于163~135 Ma的洋陆俯冲环境和135~103 Ma的岩石圈减薄环境,为变质热液萃取壳源Au成矿;(5)岩浆热液型Au矿床仅形成于135~103 Ma的岩石圈减薄环境,为岩浆热液携带壳源Au成矿。矿集区主要存在两种叠加成矿作用,即不同构造背景下多种成矿系统的叠加和同一构造背景下不同成矿系统的叠加。     

Comparison of Internal Structures of Marine Manganese Deposits of Hydrogenetic, Diagenetic and Hydrothermal Origins

Abstract: Detailed microscopic observation, combined with X-ray diffraction and EPMA analyses of samples from marine manganese deposits of three different origins, suggests that characteristic internal structures are inherent in each manganse mineral; vernadite (δ–MnO₂), buserite (10Å–manganate) and todorokite (10Å–manganate).     

Polymetallic Mineralization at the Suttsu Vein-type Deposit, Southwestern Hokkaido, Japan

Abstract. The Suttsu polymetallic vein-type deposit, hosted by tuff, tuff breccia and shale of the Miocene Kunnui Formation and propylitized hornblende-augite andesite, is located in southwestern Hokkaido, Japan. It has been exploited and explored for Cu, Pb, Zn and Ag until 1962.
In this study, we examined K-Ar ages, ore mineralogical characteristics and fluid inclusions to obtain new data for the deposit.
The K-Ar ages on sericite indicate that the polymetallic mineralization occurred in Late Miocene (8.1–5.7 Ma). The polymetallic banded ore from the Ohkubo vein is characterized by an abundance of Au, Ag, Sn, Bi, in, Se and Te. These metals are mainly ascribed to electrum (30.3–37.8 atom% Ag), Se-bearing pavonite (8.5–9.5 wt% Se), gustavite-lillianite solid solution, Se-bearing bismuthinite (5.0–5.3 wt% Se), kawazulite, cassiterite, Sn-bearing chalcopyrite (3.3–4.2 wt% Sn), In-bearing stannite, stannite-chalcopyrite solid solution, and In- and Sn-bearing sphalerite (2.6–8.4 wt% In and 1.8–4.3 wt% Sn), occurring in narrow bands of the ore. The In- and Sn-bearing sphalerite likely forms a sphalerite-roquesite-stannite solid solution with the contents of roquesite and stannite being about 2–9 and 2-A mole%, respectively. Temperatures and salinities (in wt% NaCl equiv.) of the ore fluids are estimated to be 180-250C and 3–4 wt%, respectively. The Sn-bearing chalcopyrite therefore probably precipitated metastably. The geologic and mineralogical features suggest that pre-Tertiary basement rocks rich in organic material underlie the Miocene Kunnui Formation nearby the deposit and that they contributed to local and temporary reduction of magnetite-series magmas favorable for the early stage tin-polymetallic mineralization.     

Granulite facies metamorphism in the Mallee Bore area, northern Harts Range: implications for the thermal evolution of the eastern Arunta Inlier, central Australia

The Mallee Bore area in the northern Harts Range of central Australia underwent high-temperature, medium- to high-pressure granulite facies metamorphism. Individual geothermometers and geobarometers and average P–T  calculations using the program Thermocalc suggest that peak metamorphic conditions were 705–810 °C and 8–12 kbar. Partial melting of both metasedimentary and meta-igneous rocks, forming garnet-bearing restites, occurred under peak metamorphic conditions. Comparison with partial melting experiments suggests that vapour-absent melting in metabasic and metapelitic rocks with compositions close to those of rocks in the Mallee Bore area occurs at 800–875 °C and >9–10 kbar. The lower temperatures obtained from geothermometry imply that mineral compositions were reset during cooling. Following the metamorphic peak, the rocks underwent local mylonitization at 680–730 °C and 5.8–7.7 kbar. After mylonitization ceased, garnet retrogressed locally to biotite, which was probably caused by fluids exsolving from crystallizing melts. These three events are interpreted as different stages of a single, continuous, clockwise P–T  path. The metamorphism at Mallee Bore probably occurred during the 1745–1730 Ma Late Strangways Orogeny, and the area escaped significant crustal reworking during the Anmatjira and Alice Springs events that locally reached amphibolite facies conditions elsewhere in the Harts Ranges.     

A practical guide to the study of glacial sediments

Evans, D. J. A. & Benn, D. I. (eds.) 2004: A Practical Guide to the Study of Glacial Sediments . Edward Arnold, London, 266 pp. ISBN 0–340–75959–3 (pb). GBP 19.99.     

Metamorphic evolution of the southern part of the Hidaka belt, Hokkaido, Japan

Abstract The Hidaka metamorphic terrane in the Meguro-Shoya area, Hokkaido, Japan is divided into four progressive metamorphic zones: A—biotite zone; B—cordierite zone; C—cordierite–K-feldspar zone; and, D—sillimanite–K-feldspar zone of the andalusite–sillimanite facies series type of metamorphism. The metamorphic grade ranges from the higher temperature part of the greenschist facies (zone A) through the amphibolite facies (zones B and C) to the lower temperature part of the granulite facies (zone D). The zone boundaries intersect the bedding planes at high angles. P–T conditions estimated are 450–550°C and 2 kbar for zone A, 550–600°C and 2–2.5 kbar for zone B, 600–650°C and 2.5–3 kbar for zone C and 650–750°C and 3–4 kbar for zone D. The metapelites of zone D were partially melted.
At the later stage of the regional metamorphism which is early Oligocene to early Miocene in age, cordierite tonalite and biotite tonalite intrusives associated with segments of the highest grade rocks (zone D) were emplaced into the lower temperature part of the regional metamorphic rocks, giving rise to a contact metamorphic aureole. The thermally metamorphosed terrain (zone C') belongs to the amphibolite facies and its P–T conditions are estimated to have been 550–700°C and 2 kbar.
The P–T–t paths of the Hidaka metamorphism show a thickening–heating–uplifting process. The metamorphism is inferred to have taken place beneath an active island arc accompanied by partial melting of the crust.     

P–T paths in the Handöl area, central Scandinavia: record of Caledonian accretion of outboard rocks to the Baltoscandian margin

The Seve–Köli Nappe Complex is widespread in the Scandinavian Caledonides and is composed of units representing parts of the Baltoscandian margin (Seve Nappes) now overlain by magmatic–sedimentary rocks (Köli Nappes) derived from west of this margin. The metamorphic evolution of Köli and Seve units has been studied in the Handöl area, central Scandinavian Caledonides, where a fragmented ophiolite with cover sequence in the lower Köli units is thrust over the higher grade Seve units. Thermobarometry constrains metamorphic conditions to 490–570° C/950–600 MPa, with a slight downwards increase in grade, for the lower Köli (Bunnerviken lens), 520–620° C/1000–600 MPa for the upper Seve (Täljstensvalen Complex), 630–740° C/750–650 MPa for the middle Seve (Snasahögarna Nappe) and 480–600° C/1150–1000 MPa for the lower Seve (Blåhammarfjället Nappe).
P–T paths during garnet growth have been constructed for all units, except the highest grade middle Seve. These paths record heating at the base of the Köli and cooling in the underlying Seve units. Pressure increase during garnet growth is indicated for all units leading to anticlockwise P–T paths in the Seve. The results imply thermal convergence with time for all units and spatial convergence in metamorphic grade in the Köli. It is suggested that the contrasting metamorphic histories on either side of the Seve–Köli boundary resulted from the emplacement of relatively colder Köli rocks on top of relatively hotter Seve rocks and that emplacement of structurally higher units contributed to the increase in pressure.     

成都金沙遗址距今3000年的古气候探讨

成都金沙遗址位于成都西郊金沙村,可能是商代晚期至西周时期（约公元前11世纪–前770年）古蜀国的都邑所在地。本文分析了金沙遗址两个探方WT7908和IT8305的31个孢粉样品,探方IT8305孢粉组合表明：蕨类植物孢子占60.3%,草本被子植物花粉占24.8%,木本裸子和被子植物花粉占14.2%,水生植物花粉相对较少,仅占0.7%。蕨类植物主要以蹄盖蕨科、水龙骨科和凤尾蕨属为主,草本植物中野牡丹科占绝对优势,木本裸子和被子植物中主要以松属和桦木属为主,水生植物主要包括双星藻、鸭跖草科和香蒲属。成都平原在这个时期的气候分为两个阶段,前期阶段的气候属于亚热带温暖湿润气候,平原上生长着茂盛的草本植物和蕨类植物;后期阶段的气候虽然还属于亚热带气候,但较前期更加湿热,气温和降雨量都比前期要高。定量分析和重建了金沙遗址距今3000年的古气候：年均温17.7–19.8ºC、最热月均温21.7–28.6ºC、最冷月均温11.5–11.9ºC、年较差12.1–14.9ºC、年降雨量993.3–1113.3 mm、最大月降雨量224.6–268.1 mm、最小月降雨量6.9–14.1 mm。成都地区3000年前的年均温比现在要高1.7–2.8ºC,而年降雨量基本和现在一致。     

Two-stage decompression in orthopyroxene–sillimanite granulites from Forefinger Point, Enderby Land, Antarctica: implications for the evolution of the Archaean Napier Complex

Magnesian metapelites of probable Archaean age from Forefinger Point, SW Enderby Land, East Antarctica, contain very-high-temperature granulite facies mineral assemblages, which include orthopyroxene (8–9.5 wt% Al₂O₃)–sillimanite ± garnet ± quartz ± K-feldspar, that formed at 10 ± 1.5 kbar and 950 ± 50°C. These assemblages are overprinted by symplectite and corona reaction textures involving sapphirine, orthopyroxene (6–7 wt% Al₂O₃), cordierite and sometimes spinel at the expense of porphyroblastic garnet or earlier orthopyroxene–sillimanite. These textures mainly pre-date the development of coarse biotite at the expense of initial mesoperthite, and the subsequent formation of orthopyroxene (4–6 wt% Al₂O₃)–cordierite–plagioclase rinds on late biotite.
The early reaction textures indicate a period of near-isothermal decompression at temperatures above 900°C. Decompression from 10 ± 1.5 kbar to 7–8 kbar was succeeded by biotite formation at significantly lower temperatures (800–850°C) and further decompression to 4.5 ± 1 kbar at 700–800°C.
The later parts of this P–T evolution can be ascribed to the overprinting and reworking of the Forefinger Point granulites by the Late-Proterozoic ( c . 1000 Ma) Rayner Complex metamorphism, but the age and timing of the early high-temperature decompression is not known. It is speculated that this initial decompression is of Archaean age and therefore records thinning of the crust of the Napier Complex following crustal thickening by tectonic or magmatic mechanisms and preceding the generally wellpreserved post-deformational near-isobaric cooling history of this terrain.     

Physicochemical Environment during the Formation of the Mozumi Skarn-type Pb–Zn–Ag Deposit at the Kamioka Mine, Central Japan: A Thermochemical Study

Abstract: The physicochemical environment during the ore formation of the Mozumi skarn-type Pb–Zn–Ag deposit, Kamioka mine, Central Japan is discussed with silicate phase equilibria using calculated phase diagrams. The mineral assemblages, mineral chemistry, and fluid inclusion data are coupled with thermodynamic calculation to estimate the stability fO2–XCO2condition of the mineral assemblages at each ore formation stage. The skarn was approximated by the model system CaO–A12O3–FeO–SiO2–O2–CO2–H2O including grossular-andradite garnet and clinozoisite-epidote solid solutions. The solid solutions are combined into the calculation using "pseudocompound approximation", and real boundary of the mineral assemblages other than simple activity corrected diagram was provided. The diagrams also show isoplethal contour for garnet and epidote.     

THE CONTINENTAL MANTLE

Oxford Monographs on Geology and Geophysics 1990, 184 pp., £45.00 (hbk) ISBN 019–854496–0 Oxford University Press, Oxford     

Fluctuations of the Deming Glacier and theoretical equilibrium line altitudes during the Late Pleistocene and Early Holocene on Mount Baker, Washington, USA

Kovanen, D. J. & Slaymaker, O. 2005 (May): Fluctuations of the Deming Glacier and theoretical equilibrium line altitudes during the Late Pleistocene and Early Holocene on Mount Baker, Washington, USA. Boreas , Vol. 34, pp. 157–175. Oslo. ISSN 0300–9483.
The Deming Glacier is presently nourished by an ice-cap type accumulation area on Mount Baker (3285 m a.s.l.). The specific meso-scale (>10km) form and isolation of the Mount Baker stratovolcano seem to influence temperature and precipitation gradients (contemporary climate data). These data are used as a reference when calculating paleo-equilibrium-line altitudes (ELAs). Six radiocarbon dates are reported, between 10 680 70 and 10 500 70 ¹⁴C yr BP (12 903–12 183 cal. yr BP) from detrital logs in drift that were buried during an advance of the Deming Glacier (altitude 3230–1158 m) during possibly the Younger Dryas interval. The calculated range of theoretical ELA depressions (ΔELA) relative to modern is 400–355 m using two different methods. Assuming no change in precipitation, ablation-season temperature would have been 2.5–2.2C cooler, which is consistent with other paleoclimatic reconstructions in this region. Alternatively, assuming that the modern reference climate is appropriate, and based on regressions of modern-day glacial conditions, the predicted mean winter precipitation necessary to support the former Deming Glacier was in the order of 200–150% (mean 175%) or 119–86% (mean 103%). This amount of precipitation could result from reinvigorated moisture transport into the North Cascades and increased seasonality at the end of the last glaciation.     

Hot contacts of garnet peridotites in middle/upper crustal levels: new constraints on the nature of the late Variscan high-T/low-P event in the Moldanubian (Central Vosges/NE France)

P–T  paths based on parageneses in the immediate vicinity of former high-temperature contact zones between mantle peridotites and granulitic country rocks of the Central Vosges (NE France) were derived by applying several conventional thermometers and thermobarometric calculations with an internally consistent dataset. The results indicate that former garnet peridotites and garnet–spinel peridotites were welded together with crustal rocks at depths corresponding to 1–1.2 GPa. The temperature of the crustal rocks was about 650–700 °C at this stage, whereas values of 1100 °C (garnet peridotites) and 800–900 °C (garnet–spinel peridotites) were calculated for the ultramafic rocks. After emplacement of the mantle rocks, exhumation of the lower crust took place to a depth corresponding to 0.2–0.3 GPa. The temperatures of the incorporated peridotite slices were still high (900–1000 °C) at this stage. This is indicated by the presence of high- T  /low- P parageneses ( c . 800 °C, 0.2–0.3 GPa) in a small (1–10 m) contact aureole around a former garnet peridotite. Crustal rocks distant to the peridotites equilibrated in the same pressure range at lower temperature (650–700 °C). High cooling rates (10²–10³ °C Ma⁻¹) were calculated for a garnet–biotite rock inclusion in the peridotites and for the crustal rocks at the contact by applying garnet–biotite diffusion modelling. Minimum rates of 0.75–7.5 cm a⁻¹ are required for vertical ascent of rock units (30 km vertical distance) derived from the crust–mantle boundary, resulting in a late Variscan (340 Ma) high- T  /low- P event.     

Evidence from U–Pb zircon and 40Ar/39Ar muscovite detrital mineral ages in metasandstones for movement of the Torlesse suspect terrane around the eastern margin of Gondwanaland

New U–Pb detrital zircon ages from Triassic metasandstones of the Torlesse Terrane in New Zealand are compared with ⁴⁰Ar/³⁹Ar muscovite data and together, reveal four main source components: (i) major, Triassic–Permian (210–270 Myr old) and (ii) minor, Permian–Carboniferous (280–350 Myr old) granitoids (recorded in zircon and muscovite data); (iii) minor, early middle Palaeozoic, metamorphic rocks, recorded mainly by muscovite, 420–460 Myr old, and (iv) minor, Late Precambrian–Cambrian igneous and metamorphic complexes, 480–570 Myr old, recorded by zircon only. There are also Proterozoic zircon ages with no clear grouping (580–1270 Myr). The relative absence of late Palaeozoic (350–420 Myr old) components excludes granitoid terranes in the southern Lachlan Fold Belt (Australia) and its continuation into North Victoria Land (East Antarctica) and Marie Byrd Land (West Antarctica) as a potential source for the Torlesse. The age data are compatible with derivation from granitoid terranes of the northern New England Orogen (and hinterland) in NE Australia. This confirms that the Torlesse Terrane of New Zealand is a suspect terrane, that probably originated at the NE Australian, Permian–Triassic, Gondwanaland margin and then (200–120 Ma) moved 2500 km southwards to its present New Zealand position by the Late Cretaceous (90 Ma). This sense of movement is analogous to that suggested for Palaeozoic Mesozoic terranes at the North American Pacific margin.