Weichselian till stratigraphy in borings from northern Falster, Denmark

A detailed lithological and petrographical investigation of 102 borings across the island of Falster, Denmark, shows that four till-beds can be distinguished. The borings are on both sides of the recessional ice border line of the G-stage of the Young Baltic Ice. The stratigraphy indicates that the morphological petrographical parameters show regional significance in differentiating the two uppermost tills. The upper one is referred to the Weichselian Young Baltic advance on the basis of stone counts and till fabrics. The lower one is referred to the Weichselian Northeast advance on the basis of stone counts and the orientation of a chalk floe. In one boring additional till-beds were recognized, one of which referred to the Weichselian Old Baltic advance, because of the clast petrography and content of reworked Eemian foraminifera. The lowermost till is interpreted as being of Saalean age on the basis of the counts of the tine gravel fraction (3–5 mm). The landscape is dominated by the morphology produced by the Northeast Ice advance, whereas the later Young Baltic advance had only a drumlinizing effect.     

Foraminiferal faunas of the Quaternary Hostrup Clay from northern Jutland, Denmark

One profile and four short borings were analyzed. A marine Quaternary deposit, here called the Hostrup Clay, was found. The two dominant species in the Hostrup Clay were Elphidium excavatum , forma clavata and Cassidulina crassa , whereas characteristic accessory species were Protelphidium orbiculare in the lower clayey part of the deposit, and Buccella frigida, Elphidiuni albiumbilicatum , and E. subarcticum together with P. orhiculare in the upper more sandy part. The Hostrup Clay faunas were compared with assemblages from other marine Quaternary deposits. The present deposit is probably correlatable with the lower part of the marine sequence of the Inder Bjergum borings at Ribe, which is supposed to be of Holsteinian Interglacial age. However, as the foraminiferal faunas indicate a climatic succession from arctic to probably boreo-arctic conditions, the Hostrup Clay, together with the corresponding cold part of the marine Quaternary sequence in the Ribe-Esbjerg region, may represent the Lateglacial part of the preceding Glacial Period, i.e. the Elsterian.     

Titan-aegirine from early Tertiary ash layers in northern Denmark

Microprobe analyses on a xenocrystic suite of salites, aegirine-augites, aegirines, titan-aegirines and acmites from a lower Tertiary ash layer in northern Denmark are presented. The sodic pyroxenes show an unusual titan-enrichment and up to 42 mol.% of the component $\text{NaTi}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}{}^{\mathrm{4+}}\text{M}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}{}^{\mathrm{2+}}\text{Si}{}_3\text{O}{}_6\text{(}\text{M = Fe}{}^{\mathrm{2+}}\text{,}\text{Mn or Mg}\text{)}$, is estimated. Optical absorption measurements show no evidence for Ti³⁺. The titan-aegirines were formed during late to post-magmatic crystallization in a system with a high Ti⁴⁺/Fe²⁺ ratio and were followed by acmite showing enrichment in jadeite. Comparison with experimentally investigated titan-aegirine indicates crystallization far below the Mn₂O₃Mn₃O₄f₀₂ buffer.     

Deformation of soft sandy sediments during deglaciation and subsequent emergence of land areas; examples from northern Karelia, Finland

A variety of deformation structures in sandy sediments are described, the origin of which may be ascribed to the escape of excess pore-water from liquefied and fluidized sediments in response to density instabilities created by external and/or internal loading. A number of deformations found in exposed nearshore sediments of an artificially drained lake provide an explanatory model according to which rapid drops in water level during the development of waterway systems in connection with post-glacial land uplift are suggested in many cases to have served as creational environments for soft sediment deformation. Other favourable circumstances in glaciated areas were obviously offered by the complex melting and sedimentation mechanisms which occurred in the envionment of the retreating ice-margin.     

Postglacial relative sea‐level rise in the Limfjord region,northern Jutland,Denmark

A new core drilled at Nørrekær Enge, Løgstør, Denmark, shows terrestrial lake and bog sediments lying beneath 10 m of marine sediments. Pollen analysis, ¹⁴C dating and sedimentary observations show that these sediments relate to an ancient lake basin that was flooded when the rising sea levels reached 8.0 m b.s.l. This new study has allowed a review of previous data relating to shoreline displacement from the Limfjord region of northern Jutland, Denmark. Here we present a new shoreline displacement curve spanning the period between c. 11 700 and 7700 cal. a BP and built upon the Nørrekær Enge data and data from seven other boreholes and excavations from the Limfjord region. A previous shoreline displacement curve for this region suggested a very rapid relative sea‐level rise of 3 to 5 m 100 a^?1 whereas this new curve suggests a much slower rise of around 1 m 100 a^?1, similar to global rates.     

Progradation geometries of carbonate platforms: examples from the Triassic of the Dolomites, northern Italy

Various types of progradation of Triassic carbonate platforms are described from the Dolomites of the Southern Alps. The internal and external geometric relationships are exposed in spectacular natural sections and, moreover, their scale (500–1000 m of thickness) is such that they can be compared with features found in seismic profiles. The different types of progradation are controlled by a number of factors which, normally, interact with each other. These factors include: rate of basinal sedimentation, rate of subsidence, width of the platform, depth of the surrounding basin and eustatic variations of sea-level. Progradation is not a continuous process but episodic. Moments of massive debris input, during which the platform advances, alternate with long periods of negligible progradation, during which basinal sediments accrete and onlap the toe of slope. Upper boundary relationships of the prograding platforms include offlap, toplap and erosional truncation. Lower boundary relationships are horizontal, climbing and descending progradations. A variety of phenomena and circumstances have caused the cessation of progradation of the Triassic platforms. They include volcanism, collapse of margins, drowning (rapid relative rise of sea-level), subaerial exposure (relative fall of sea-level) and, probably, a natural decay of the system. In the Triassic of the Dolomites, two main progradation models can be put forward: in the Ladinian model, progradation took place simultaneously with aggradation (relative rise of sea-level), whereas the characteristic feature of the Carnian model is toplap (relative stillstand of sea-level).     

Elsterian‐Holsteinian deposits at Kås Hoved,northern Denmark: sediments,foraminifera, ostracods,and stable isotopes

The coastal cliff section at Kås Hoved in northern Denmark represents one of the largest exposures of marine interglacial deposits in Europe. High‐resolution analyses of sediments, foraminifera, ostracods, and stable isotopes (oxygen and carbon) in glacial‐interglacial marine sediments from this section, as well as from two adjacent boreholes, are the basis for an interpretation of marine environmental and climatic change through the Late Elsterian‐Holsteinian glacial‐interglacial cycle. The overlying glacial deposits show two ice advances during the Saalian and Weichselian glaciations. The assemblages in the initial glacier‐proximal part of the marine Late Elsterian succession reveal fluctuations in the inflow of sediment‐loaded meltwater to the area. This is followed by faunal indication of glacier‐distal, open marine conditions, coinciding with a gradual climatic change from arctic to subarctic environments. Continuous marine sedimentation during the glacial‐interglacial transition is presumably a result of a large‐scale isostatic subsidence caused by the preceding extended Elsterian glaciation. The similarity of the climatic signature of the interglacial Holsteinian and Holocene assemblages in this region indicates that the Atlantic Ocean circulation was similar during these two interglacials, whereas Eemian interglacial assemblages indicate a comparatively high water temperature associated with an enhanced North Atlantic Current. The foraminiferal zones are correlated with other Elsterian‐Holsteinian sites in Denmark, as well as those in the type area for the Holsteinian interglacial in northern Germany and the southern North Sea. Correlation of the NW European Holsteinian succession with the marine isotope stages MIS 7, 9 or 11 is still unresolved.     

Groundwater salinity in Greve, Denmark: determining the source from historical data

Elevated salinity in groundwater (over 250?mg/l chloride) in a fractured chalk aquifer in the municipality of Greve, Denmark, has been attributed to seawater intrusion from the Baltic Sea, resulting in the closure of a number of wells nearest to the coastline. However, a recent study in eastern Denmark shows that the salinity could also be from ancient connate pore waters. Historical chemistry data from bulk-water samples collected from wells have been used to determine the source. The sample data were studied with respect to their historical changes and temporal trends in chloride, carbonate, sulfate, sodium, potassium, magnesium, and calcium. Wells in the southern third of the municipality are relatively low in sodium and carbonate and high in chloride and calcium/magnesium, indicating waters undergoing saline intrusion. Wells in the northern two-thirds of the municipality are high in carbonate and sodium, but low in chloride and calcium/magnesium, indicating a freshening of the aquifer. This is confirmed by the temporal trends in chloride, where chloride levels in the northern wells remain constant, whereas in the south, chloride increases as abstraction continues. Therefore close monitoring for seawater intrusion should be conducted in the southern third of the municipality.     

Lithostratigraphy of the Late Saalian to Middle Weichselian Skærumhede Group in Vendsyssel, northern Denmark

The Quaternary sedimentary succession in Vendsyssel, northern Denmark, contains a unique, high‐resolution record of the last interglacial and glacial periods. There is still much debate, however, about the timing and ice extent in this southwestern part of the Scandinavian Ice Sheet, particularly during the Middle Weichselian. In this study, a detailed lithostratigraphical subdivision is established for the Late Saalian to Middle Weichselian Skærumhede Group on the basis of numerous, up to 250 m deep, boreholes in Vendsyssel. The sediments mainly consist of marine clays, glaciolacustrine sediments and tills, and the total thickness of the Skærumhede Group is up to 140 m. Marine intervals have been used as stratigraphical marker units to separate the formations indicative of ice‐sheet activity in Vendsyssel, and the timing of the events has been constrained by a large number of optically stimulated luminescence (OSL) and radiocarbon ages. The Skærumhede Group is subdivided into seven formations and two members, reflecting shifts between marine and terrestrial sedimentation caused by fluctuations of the Scandinavian Ice Sheet and changes in sea level. The lowermost Skærumhede Till Formation was deposited directly on top of the bedrock during the Warthe advance c. 160–140 kyr BP. Above, there are fine‐grained marine sediments, subdivided into the Lower, Middle and Upper Skærumhede Clay Formations. The marine formations are separated by the Brønderslev Formation related to the Sundsøre ice advance from the north c. 65–60 kyr BP, and the Åsted Formation, deposited during the Ristinge advance from an east–southeastern direction c. 55–50 kyr BP. The uppermost formation in the group is the Lønstrup Klint Formation, which is an upwards‐coarsening sequence of mainly glaciolacustrine sediments deposited prior to the Kattegat advance c. 30–29 kyr BP. The new evidence from Vendsyssel has shown that the Skærumhede Group covers a large area, and that it can be used as a regional stratigraphical marker horizon. Furthermore, it contributes to a better understanding of the timing and extent of glacial events during the Late Saalian to Middle Weichselian in southwest Scandinavia.     

Sr and Nd isotope data from the fluorspar district of Asturias, northern Spain

The origin and age of the hydrothermal fluids related to the precipitation of fluorite, barite and calcite in the Villabona, La Collada and Berbes localities (Asturias fluorspar district, N Spain) have been evaluated from Sr and Nd radiogenic isotopes. Sr isotope data (⁸⁷Sr / ⁸⁶Sr = 0.7081 to 0.7096) are compatible with mixing between seawater and a more evolved groundwater that interacted with the basement. From Nd isotopes in fluorite, an isochron age of 185 ± 29 Ma (Lower Jurassic) was obtained, consistent with other hydrothermal events in the Iberian Peninsula and Europe. These constraints are essential to proceed with a quantitative model for the genesis of the mineralization that includes fluid and heat flow together with reactive transport of solutes.     

Marine glacial and interglacial stratigraphy in Vendsyssel, northern Denmark: foraminifera and stable isotopes

The marine Quaternary of Vendsyssel has been studied in a series of new boreholes in the area, and the climatic development is discussed on the basis of foraminiferal assemblages and stable isotopes. The foraminiferal zones are correlated with previously published records from northern Denmark, and the spatial local and regional distribution is discussed in details based on the new evidence. The new data show that the marine sedimentation in Vendsyssel was not continuous from the Late Saalian to the Middle Weichselian, as previously thought. For example, there is indication of a hiatus at our key site, Åsted Vest in the central part of Vendsyssel, at the transition between regional foraminiferal zones N4 and N3, i.e. at the Late Saalian (MIS 6) – Eemian (MIS 5e) transition. The hitherto most complete Early Weichselian succession (zone N2) in Vendsyssel is presented from Åsted Vest. Deposits from the Early Weichselian sea‐level lowstands (MIS 5d and 5b) may, however, be missing in parts of the area. Two major breaks in the marine deposition during the Middle Weichselian represent glacial advances into northern Denmark. The first event occurred just after deposition of the regional foraminiferal zone N2 (late MIS 4), and the second event in the middle part of zone N1 (early MIS 3). Zone N1 is succeeded by a series of non‐marine units deposited during the sea‐level lowstand of the Weichselian maximum glaciation (late MIS 3 and MIS 2), including deeply incised tunnel valleys, which have been refilled with non‐marine sediments during the Late Weichselian. Vendsyssel was inundated by the sea again during the Late Weichselian, at c. 18 kyr BP. Subsequently, the marine conditions were gradually changed by forced regression caused by local isostatic uplift, and around the Weichselian–Holocene transition most of Vendsyssel was above sea level. A continuous deposition across the Late Weichselian–Holocene boundary only occurred at relatively deep sites such as Skagen. The environmental and climatic indications for Vendsyssel are in accordance with the global sea‐level curve, and the Quaternary record is correlated with the oxygen isotope record from the NorthGRIP ice core, as well as the marine isotope stages.     

Comments on the development of rifts and transform faults during continental breakup; examples from the Gulf of Aden and northern Red Sea

A number of basins are observed to extend inland from the coasts on both sides of the Gulf of Aden. The basins are orientated at approximately right angles to the spreading direction and intersect the coasts at the meeting of sheared and rifted continental margins. They appear to be grabens, one wall of which is continuous with the half graben of the neighbouring rifted margin. It is suggested that these were once parts of a number of discrete rifts arranged en-echelon along a zone of lithospheric weakness during the early opening of the Gulf of Aden, which became redundant when transform faults formed. The proposed development of rifts and transform faults is similar to that of a spreading centre, transform fault, spreading centre pattern developed in the freezing wax model of Oldenburg and Brune (1975). The Gulf of Suez at the northern end of the Red Sea is interpreted in a similar way since it has a number of features in common with the basins in the continents adjacent to the Gulf of Aden.     

Late Hercynian–Mesozoic thinning in the Alboran domain: metamorphic data from the northern Rif, Morocco

In the Alboran domain, two crustal-thickening late-orogenic extension cycles are superposed. The importance of the late Alpine thinning of the Alpujarride-Sebtide crustal section on top of the Beni Bousera peridotites is discussed here in metamorphic petrological terms. The Alpine metamorphism operated first under a HP–LT gradient, and reached the eclogite facies in the Permian–Triassic phyllites, before retrogression under a high geothermal gradient. A contrasting, higher temperature metamorphism characterizes the pre-Permian section, reaching the HP-granulite facies at the bottom of the crustal section. By reference to the western European setting, the granulites relate to the Hercynian orogeny, as supported by the isotopic ages of the enclosed, armoured monazite crystals. Thus, thinning of an overthickened crust might have occurred there during the late Hercynian extension and Tethyan opening, before being reactivated during the late Oligocene.     

Vegetation change based on SPOT-VGT data from 1998 to 2007, northern China

Dynamic change of vegetation in northern China from 1998–2007 was explored, based on SPOT-VGT data. The results showed that the NDVI can effectively monitor vegetation change, but also the mean multi-year NDVI maximum of 0.10 basically can be considered as the threshold of vegetation cover in northern China, and those places with smaller than or equal to the threshold value mainly were covered by deserts, Gobi and lakes, salinization lands, glaciers, snow patches and bare mountains, etc. The change trends of vegetation where sub-region C and D were affected by east-Asia monsoon were similar with the characteristics of first decreasing, later increasing and finally slowly decreasing; the difference lies in that sub-region C maintained a lower vegetation state, and sub-region D reached a higher state. The vegetation change of sub-region A was anomalous with smaller fluctuation. The change trend of vegetation of sub-region B was not only extremely unstable, but also the change extent was huge. As far as the whole of northern China is concerned, vegetation has not demonstrated obvious improvement since these ecological construction and protection projects, and the area of vegetation degradation still is much larger than that of vegetation improvement from 1998 to 2007, but there was a bigger spatial difference. Field investigation and remote sensing monitoring reveal that vegetation has obviously been improved in the agro-grazing mixing zone and to the south, as well as many oases in the northwestern arid zone, while vegetation still has worsened in the steppes, especially the Ulanqab steppe, Hunshandake Sandy Land, the region along the Sino–Mongolia border within Xilingol Meng, Hulunbeir Sandy Land and the northern Tianshan mountain region in Xinjiang. Human activities only obviously showed success in local regions. The compelling challenges of restoring the eco-environment are still immense, especially in the northern grazing zone of China.     

Sulfur and oxygen isotope study of sulfate reduction in experiments with natural populations from Fællestrand, Denmark

This study investigates the sulfur and oxygen isotope fractionations of dissimilatory sulfate reduction and works to reconcile the relationships between the oxygen and sulfur isotopic and elemental systems. We report results of experiments with natural populations of sulfate-reducing bacteria using sediment and seawater from a marine lagoon at Fællestrand on the northern shore of the island of Fyn, Denmark. The experiments yielded relatively large magnitude sulfur isotope fractionations for dissimilatory sulfate reduction (up to approximately 45‰ for ³⁴S/³²S) with higher δ¹⁸O accompanying higher δ³⁴S, similar to that observed in previous studies. The seawater used in the experiments was spiked by addition of ¹⁷O-labeled water and the ¹⁷O content of residual sulfate was found to depend on the fraction of sulfate reduced in the experiments. The ¹⁷O data provides evidence for recycling of sulfur from metabolic intermediates and for an ¹⁸O/¹⁶O fractionation of ∼25-30‰ for dissimilatory sulfate reduction. The close correlation between the ¹⁷O data and the sulfur isotope data suggests that isotopic exchange between cell water and external water (reactor water) was rapid under experimental conditions. The molar ratio of oxygen exchange to sulfate reduction was found to be about 2.5. This value is slightly lower than observed in studies of natural ecosystems [e.g., Wortmann U. G., Chernyavsky B., Bernasconi S. M., Brunner B., Böttcher M. E. and Swart P. K. (2007) Oxygen isotope biogeochemistry of pore water sulfate in the deep biosphere: dominance of isotope exchange reactions with ambient water during microbial sulfate reduction (ODP Site 1130). Geochim. Cosmochim. Acta71, 4221-4232]. Using recent models of sulfur isotope fractionations we find that our combined sulfur and oxygen isotopic data places constraints on the proportion of sulfate recycled to the medium (78-96%), the proportion of sulfur intermediate sulfite that was recycled by way of APS to sulfate and released back to the external sulfate pool (∼70%), and also that a fraction of the sulfur intermediates between sulfite and sulfide were recycled to sulfate. These parameters can be constrained because of the independent information provided by δ¹⁸O, δ³⁴S, δ¹⁷O labels, and Δ³³S.     

Thermochemical and pressure-volume-temperature systematics of data on solids,examples: Tungsten and MgO

Data systematization using the constraints from the equation $$Cp = Cv + \alpha _P {}^2V_T K_T T$$ where C _p, C _v, α _p, K _T and V are respectively heat capacity at constant pressure, heat capacity at constant volume, isobaric thermal expansion, isothermal bulk modulus and molar volume, has been performed for tungsten and MgO. The data are $$K_T (W) = 1E - 5/(3.1575E - 12 + 1.6E - 16T + 3.1E - 20T^2 )$$ $$\alpha _P (W) = 9.386E - 6 + 5.51E - 9T$$ $$C_P (W) = 24.1 + 3.872E - 3T - 12.42E - 7T^2 + 63.96E - 11T^3 - 89000T^{ - 2} $$ $$K_T (MgO) = 1/(0.59506E - 6 + 0.82334E - 10T + 0.32639E - 13T^2 + 0.10179E - 17T^3 $$ $$\alpha _P (MgO) = 0.3754E - 4 + 0.7907E - 8T - 0.7836/T^2 + 0.9148/T^3 $$ $$C_P (MgO) = 43.65 + 0.54303E - 2T - 0.16692E7T^{ - 2} + 0.32903E4T^{ - 1} - 5.34791E - 8T^2 $$ For the calculation of pressure-volume-temperature relation, a high temperature form of the Birch-Murnaghan equation is proposed $$P = 3K_T (1 + 2f)^{5/2} (1 + 2\xi f)$$ Where $$K_T = 1/(b_0 + b_1 T + b_2 T^2 + b_3 T^3 )$$ $$f = (1/2)\{ [V(1,T)/V(P,T)]^{2/3} - 1\} $$ $$\xi = ({3 \mathord{\left/ {\vphantom {3 4}} \right. \kern-\nulldelimiterspace} 4})[K'_0 + K'_1 \ln ({T \mathord{\left/ {\vphantom {T {300}}} \right. \kern-\nulldelimiterspace} {300}}) - 4]$$ where in turn $$V(1,T) = V_0 [\exp (\int\limits_{300}^T {\alpha dT)]} $$ . The temperature dependence of the pressure derivative of the bulk modulus (K′₁) is estimated by using the shock-wave data. For tungsten the data are K′₀ = 3.5434, K′₁ = 0.032; for MgO K′₀ = 4.17 and K′₁ = 0.1667. For calculating the Gibbs free energy of a solid at high pressure and at temperatures beyond that of melting at 1 atmosphere, it is necessary to define a high-temperature reference state for the fictive solid.