Timing of deformation phases within the South Finland shear zone, SW Finland

The Palaeoproterozoic Svecofennian crust in southern and central Fennoscandia was established about 1.8 Ga ago after a prolonged history of accretion and intrusion. During late stages of the Svecofennian orogeny, deformation was partitioned into several crustal-scale shear zones in present-day Finland, Sweden and Estonia. One such major ductile deformation zone, ‘the South Finland shear zone’ (SFSZ) extends for almost 200 km through the Åland archipelago in southwestern Finland, and further along the southern and southwestern coast of Finland. This more than a kilometer wide transpressional zone appears to have been repeatedly reactivated. The deformation started with a period of regional, ductile dextral shearing of igneous rocks, producing striped granodioritic and tonalitic gneisses. The ductile phases are locally overprinted and followed by ductile to semi-ductile deformation evidenced by mylonite zones of variable width. The last stage of tectonic activity along the shear zone is recorded by pseudotachylites. Within this study, we dated zircons (SIMS U–Pb) and titanites (ID-TIMS U–Pb) from eight rock samples, and two pseudotachylite whole-rock samples (⁴⁰Ar/³⁹Ar) in order to reconstruct the deformation and (re)activation history of the shear zone.The results suggest that the medium-grained gneisses underwent three distinct deformation phases separated by time intervals without regional deformation. The ductile deformation within the study area initiated at 1.85 Ga. A second, more intensive deformation phase existed around 1.83 Ga, by which the shear zone was already well developed. Finally, the last ductile event is recorded by 1.79 Ga metamorphic titanites in relatively granoblastic granitoid gneisses that nevertheless already display protomylonitic textures, suggesting the initiation of large-scale mylonitisation around or soon after this time. The age of a pseudotachylite sample and, hence, the brittle deformation is bracketed between 1.78 and 1.58 Ga based on the age of pegmatites cut by pseudotachylites as well as ⁴⁰Ar/³⁹Ar minimum ages for the pseudotachylite, respectively. The data imply that the rocks within the study area entered the ductile–brittle transition zone due to rapid cooling and exhumation of the crust after 1.79 Ga.     

Weichselian in Finland before 15,000 B. P.

A historical review is given of the stratigraphic and chronological research of the Weichselian glaciation in Finland. Submorainic interglacial organogenic deposits have been found in Finnish Lapland and Ostrobothnia. Radiocarbon analyses give ages of over 50,000 years B.P. and the microfissil assemblages indicate climatic conditions that are more fovourable than at present. Interstadial deposits with radiocarbon ages of 42,000 to over 50,000 years B.P. contain fossil assemblages in dicating a poorer climate than at present. A tentative correlation of the Weichselian stratigraphy by various authors is presented.     

The deglaciation of Finland after 10,000 B. P.

Various concepts of the deglaciation of Finland are presented in the form of a historical review. The suggestions of an early (12,000–10,000 B.P) deglaciation of eastern and northern Finland are considered to be erroneous. A map depicting the ice recession as successive ice-marginal lines is presented. According to radiocarbon dates the Finnish territory was entirely deglaciated slightly after 9000 B. P.     

Metasomatic depletion of Ni-Cu-Fe sulphides,Vammala Mine,Finland

Summary Migmatite-derived granitic melt dilationally intruded a 1.89 Ga Ni-Cu-Fe sulphide-bearing peridotite layer. A reduction of in situ ore grade resulted from the 5–15% volume increase. Alteration zones of amphibole-phlogopite, after peridotite, separate the once-granitic dykes from the now-serpentinized peridotite. The mass-gains and -losses of the peridotite-to-zonereal transition are studied in terms of the serpentinized peridotite-to-zoneapparent transition. Ni, Cu, FeO and S were overall mass-loss components during the metasomatic exchange between the peridotite and the granitic melt. However, the components were retained but redistributed (internally remobilised) in the outer zones, but transferred into the dyke from the innermost zone (externally remobilised). Because theextent of theexternal remobilisation was on the scale of centimetres to metres, sulphides were not lost from the volume encompassing the peridotite and dykes. In contrast to dilation, remobilisation did not adversely influencein situ ore grade at stopeor mine-scales.

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Metasomatische Verarmung von Ni-Cu-Fe Sulfiden, Vammala Mine, Finnland

Zusammenfassung Eine granitische Schmelze aus Migmatiten intrudierte eine 1.89 Ga alte Ni-Cu-Fe Sulfid-führende Peridotitlage. Die Volumenzunahme von 5 bis 15% führte zu einer Reduktion derin situ Erzgehalte. Umwandlungszonen von Amphibol-Phlogopit, die aus dem Peridotit hervorgegangen sind, trennen die ehemals granitischen Gänge von dem jetzt serpentinisierten Peridotit. Massengewinne und -verluste der realen Übergangszonen werden auf Basis der serpentinisierten scheinbaren Übergänge untersucht. Ni, Cu, FeO and S waren Massenverlust-Komponenten wdhrend des metasomatischen Austausches zwischen dem Peridotit und der granitischen Schmelze. Die Komponenten wurden jedoch behalten aber umverteilt (intern remobilisiert) in den äußeren Zonen, aber in den inneren Zonen wurden sie in den Gang transferiert (externe Remobilisation). Weil das Ausmaiß der externen Remobilisation im Maßstab von Zentimetern bis Metern lag, wurden Sulfide aus dem Volumen der Peridotite und Gänge nicht abgeführt. Im Gegensatz zu Aufweitung hat Remobilisation keinen negativen Einfluß auf denin situ Erzgehalt auf dem Maßstab von Abbauen oder ganzen Bergwerken.

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With 4 Figures     

Geochemical Atlas of Finland: preliminary aspects

During 1984 and 1985, the Geological Survey of Finland carried out regional geochemical mapping of till, at a scale of 1:2,000,000, as part of a programme to produce data for the first Geochemical Atlas of Finland. The Atlas is designed to give comprehensive background information on the distribution of elements in rocks, soils, and the surficial environment.     

The amphibolite-granulite facies transition in West Uusimaa, S.W. Finland. A fluid inclusion study

This work presents the results of a fluid inclusion study of an amphibolite-granulite facies transition in West Uusimaa, S.W. Finland. Early fluid-inclusions in the granulite facies area are characteristically carbonic (CO₂), in contrast to predominantly aqueous early inclusions in the amphibolite facies area. These early inclusions can be related to peak metamorphic conditions (750-820°C and 3-5 kbar for peak granulite facies metamorphism). Relatively young CO₂ inclusions with low densities (<0.8g/cm³) indicate that the first part of the cooling history of the rocks was characterized by a near isothermal uplift.
N₂-CH₄ inclusions, with compositions ranging between pure CH₄ and pure N₂ (Raman spectral analysis), were found in the whole area. They are probably syn- or even pre-early inclusions. Only nearly critical homogenizing inclusions have been found (low density). Pressure estimates, based on densities of early fluid inclusions, show that the rapid transition of amphibolite towards granulite facies metamorphism is virtually isobaric. Granulite facies metamorphism in West Uusimaa is a thermal event, probably induced by the influx of hot, CO₂-bearing fluids.     

Application of till geochemistry to gold exploration, Ilomantsi, Finland

The Archean bedrock of the Ilomantsi area consists of narrow greenstone belts between dome-like granitoids. The main tectonic phases are isoclinal folding, dragging of isoclinal folds around subvertical axes and regional faulting. Conspicuous anomalies of As, Au, Mo and W were revealed in the course of regional geochemical mapping of till, which led to more detailed studies in Ilomantsi. The data presented in this study are based mainly on the results of 2960 till samples collected by light percussion drill at local scale (16 samples/km²), but also on the results of regional (1 sample/4 km²) and detailed (100–400 samples/km²) sampling and on rock samples collected from outcrops. The analytical methods most commonly used were emission spectrometry, atomic absorption spectrophotometry and spectrometry.The results indicate that the lowest part of the basal till is dominated by local debris and that the geochemistry of the till reflects well the underlying bedrock. The highest Au values exist near the contacts of tonalite and supracrustal rocks. Arsenic follows intimately the directions of faulting. The anomalous contents of W and Mo are restricted to the southern part of the 15-km² Kuittila tonalite. Potassium, Na and Ca form conspicious anomalies in till, cutting both the supracrustal rocks and the granitoids. Local studies revealed in the Kuittila tonalite a notable network of Mo- and W-bearing quartz veins restricted to tensional zones of main fault directions, which are cut by gold-bearing shear zones and quartz vein nets. These shear zones are of en echelon type and they are silicified, sericitized, tournalinized, Na-depleted and partly carbonitized. The hosting tonalite is intensely biotitized. These metasomatic features of the bedrock can be correlated to the wider anomalies of K, Na and Ca in till. The implication is that significant migration of mobile elements has taken place in the bedrock of the study area and that, in places, gold has participated in these processes.     

New Universities and their cities, the case of Vaasa, Finland

University activities began in Finland in 1640 when the University of Turku was founded. Later it was transferred to Helsinki, the new capital of Finland. The turn of the century saw the emergence of new university level institutions in Helsinki and Turku. The explosion of the Finnish university system took place after the Second World War. Now there are 20 university level institutes. Consequently the access to university studies and other services has improved greatly. The university centre of Vaasa belongs to the new wave of universities founded from 1960 on. In the city there are now 4 units, one Finnish speaking, two Swedish speaking and one bilingual. This reflects the language structure of the area. All of the universities have had their individual development features. The Finnish speaking University of Vaasa is the biggest one. The main impact of the Vaasa universities is the participation in the rising of the level of education in Finland and its effect on economy and other development. The research institute of Vaasa University has served the surrounding areas and nation through applied research projects. The continuing education centre has served the areas firms with many kinds of tailored courses for the management. In the humanistics influence has been through specialised language courses and multilingual immersion. A newspaper university is one of the new forms of impact. The city has an Academic axis going through the innermost part of the city. It is divided clearly into two Finnish and one Swedish speaking area.     

Thermoluminescence dating of sediments from Oulainen and Vimpeli, Ostrobothnia, Finland

Mean ages of 94 ka and 121 ka were obtained at Oulainen for two sand layers situated above and below an organic deposit previously correlated with the Brörup interstadial. At Vimpeli, TL dates obtained for sand layers embedded in an organic deposit suggest an age for this deposit of 107 ka. The uncertainty in this result is considerable, however. Problems encountered in dating these sediments and the reliability of the results are discussed.     

Airfreight: Geographical patterns and economics. Forecasting models with an example from Finland

In my paper I will try to give some geographical and economical aspects on the recent development of airfreight.Some models for forecasting will be presented, especially three made by (i) DOUGLAS Aircraft's RD; (ii) IATA Freight Traffic Forecasts and (iii) A trend model modified in my department. These three models will be applied and compared with special respect to Finnish airfreights during the 80's.     

Geospeedometry of metamorphic rocks: examples in the Rantasalmi-Sulkava and Kiuruvesi areas, eastern Finland. Biotite–garnet diffusion couples

Compositional zoning in biotite–garnet pairs in metamorphic rocks from eastern Finland has been studied. The Mg profiles in the garnet side of biotite–garnet crystal pairs have been interpreted by means of Lasaga's theory (geospeedometry). However, the binary interdiffusion equations are first reformulated by starting from a ternary system and using the lattice fixed frame of reference. This frame of reference gives the fluxes directly by means of the numbers of diffusing ions, which helps to check the 1-dimensionality of the analysis assumed in Lasaga's theory. It is also shown that the recently argued effect of the third cation Ca is negligible in our samples. We were able to investigate satisfactory profiles in three samples from different areas. The values for the cooling rate are a few degrees per million years if the diffusion data obtained by Freer are adopted. The cooling rates are in agreement with recent estimates based on the K–Ar ages on biotite in the same areas.     

Loveringite from the koitelainen layered intrusion,Northern Finland

Summary Conditions favouring the crystallization of loveringite, (Ca, REE) (Ti, Fe, Cr)₂₁ 0₃₈ in Koitelainen were sustained from the base of the lower zone to the upper part of the main zone. Loveringite is most common in rocks with much intercumulus quartz, potassium feldspar, and phlogopite, and is accompanied by accessories such as zircon, chlorapatite, baddeleyite and thorite. It is particularly common among pyroxene cumulates in the upper part of the lower zone. Here, and apparently also in plagioclaseorthopyroxene-clinopyroxene cumulates of the main zone, loveringite occurs as a cumulus phase. The presence of Cr in the intercumulus liquid is not essential to the stability of loveringite; instead, petrographic evidence and the presence of incompatible elements (Zr, Hf, REE, U, Th) contained in loveringite point to the crucial role of crustal contaminants. Loveringite crystallized in parts of the magma chamber heavily contaminated by acid crustal anatectic melt, and eventually settled from density flows loaded with cumulus crystals. Postcumulus reactions produced concentric ilmenitezircon mantles around loveringites and thus contributed to the compositional heterogeneity of the mineral. We suggest that much of the loveringite that once crystallized in layered intrusions may have been consumed through postcumulus reactions. Loveringite is easy to detect under the reflected light microscope and can be readily distinguished from rutile, chromite and ilmenite, but not from some other members of the crichtonite group. The composition of the Koitelainen loveringite is comparable to that of other occurrences. The spectral reflectance values are 2–3% lower as compared to ilmenite. The reflectance data indicate that the mineral is anisotropic. The VHN₁₀₀ values, 792–933, are significantly higher than those published heretofore.[/p]

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Loveringit aus dem Intrusiv-Komplex von Koitelaineen, Nordfinland

Zusammenfassung In der Koitelainen-Intrusion waren während der magmastichen Etwitcklung der Gesteine der älower zone" und ämain zone" die Bedingungen für die Bildung von Loveringit, (Ca, REE) (Ti, Fe, Cr)₂₁ O₃₈, erfüllt, der in Gesteinen mit Quarz, Kalifeldspat und Phlogopit als Interkumulus, häufig auftritt. Sein Vorkommen ist eng verknüpft mit akzessorischen Mineralen wir Zirkon, Chlorapatit, Baddeleyit und Thorit. Ebenso häufig wurde Loveringit in den Pyroxen-Kumulaten der älower zone" und in PlagioklasOrtho-und Klinopyroxen-Kumulaten der ämain zone" als Kumulus-Phase gefunden. Die Anwesenheit von Cr in der Interkumulus-Schmelze ist kein wesentlicher Faktor für die Stabilität des Loveringits. Vielmehr zeigen petrologische Hinweise und die Konzentration der inkompatiblen Elemente (Zr, Hf, seltene Erden, U, Th) in Loveringit die entscheidende Rolle der krustalen Kontamination des Magmas bei seiner Bildung an. Es kristallisierte in Teilbereichen der Magmenkammer, die durch krustale anatektische Schmelze stark kontaminiert war. Reaktionen während der Postkumulusphase führten zur Bildung von konzentrischen Ilmenit-Zirkon-Säumen um Loveringitkristalle und bewirken eine chemische Inhomogenität sowie teilweise Aufläsung des Minerals. Aufgrund dieser Beobachtungen wird vermutet, daß ein großer Teil der in älayered intrusions" einmal kristallisierten Loveringite bei Reaktionen in der Postkumulusphase von der Schmelze wieder konsumiert wurde. Die chemische Zusammensetzung des Loveringits von Koitelainen ist mit der aus anderen Vorkommen vergleichbar. Mikroskopisch läßer sich anhand seiner Reflexionsdaten ohne weiteres von den Begleitmineralen Rutil, Chromit und Ilmenit unterscheiden. Die spektrale Reflexion von Loveringit ist 2–3% niedriger als bei Ilmenit. Die VHN_1OO-Werte mit 792–933 sind im Vergleich zu den bisher publizierten Daten wesentlich höher.

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With 7 Figures     

The 2003 earthquake swarm in Anjalankoski, south-eastern Finland

During May 2003 a swarm of 16 earthquakes (M_L = 0.6–2.1) occurred at Anjalankoski, south-eastern Finland. The activity lasted for three weeks, but additional two events were observed at the same location in October 2004. A comparison of the waveforms indicated that the source mechanisms and the hypocentres of the events were nearly identical.A relative earthquake location method was applied to better define the geometry of the cluster and to identify the fault plane associated with the earthquakes. The relocated earthquakes aligned along an ENE–WSW trending zone, with a lateral extent of about 1.0 km by 0.8 km. The relative location and the waveform-modelling of depth sensitive surface wave (Rg) and S-to-P converted body wave (sP) phases indicated that the events were unusually shallow, most likely occurring within the first 2 km of the surface. The revised historical earthquake data confirm that shallow swarm-type seismicity is characteristic to the area.The focal mechanism obtained as a composite solution of the five strongest events corresponds to dip-slip motion along a nearly vertical fault plane (strike = 250°, dip = 80°, rake = 90°). The dip and strike of this nodal plane as well as the relocated hypocentres coincide with an internal intrusion boundary of the Vyborg rapakivi batholith.The events occur under a compressive local stress field, which is explained by large gravitational potential energy differences and ridge-push forces. Pore-pressure changes caused by intrusion of ground water and/or radon gas into the fracture zones are suggested to govern the swarm-type earthquake activity.     

Petrogenesis of Archaean Trondhjemites, Tonalites, and Granodiorites from Eastern Finland: Major and Trace Element Geochemistry

The grey gneisses of eastern Finland form the basement on whichthe Archaean greenstone belts were developed. They are composedof orthogneisses emplaced during two distinct magmatic episodes:2.86 Ga (Kivij?rvi gneisses) and 2.65 (Naavala gneisses). Theirmodal and chemical compositions are those of trondhjemites,tonalites and granodiorites (TTG). Both suites show low-K₂Ocalc-alkaline differentiation trends (trondhjemitic). The aim of this study is to qualify and quantify the successionof different mechanisms by which the TTG series evolved. Theyoungest process was studied first, and the arguments then appliedin order to go back in time to the older ones. For each one,quantification was arrived at with the major elements, and theseresults provided a basis for calculation with the rare earthelements (REE). Finally the whole model was tested with othertrace elements. The petrogenetic model may be summarized as follows: meltingof the upper mantle to form a tholeiitic crust; melting of thesetholeiites transformed into garnet-bearing amphibolites to yieldthe parental magma of the TTG. The residue of the melt consistedof hornblende, plagioclase, clinopyroxene, and garnet with minoramounts of ilmenite and magnetite (10 < F < 30); and fractionalcrystallization of hornblende, plagioclase, and ilmenite withoccasional allanite and/or zircon in small amounts ((1-F) <40). No matter when they were emplaced during the Archaean, all theTTG of this part of the Baltic Shield arose from similar parentalmagmas. The petrogenetic study has shown that garnet and hornblendewere necessarily residual phases during the melting of the Archaeantholeiites. This constraint is very important, as it impliesthat the Archaean geothermal gradients occurring in subduction-zoneswere much higher than in modern times, thus allowing the partialmelting of the subducted oceanic crust.     

Meteorological impacts on the water quality in the Pajuluoma acid sulphate area,W. Finland

Water samples (n = 354) from a small catchment (7.4 km²) covered by acid sulphate soils (pH < 4) were collected during all seasons and all types of hydrological conditions in 1990–2001. The electric conductivity (EC) and pH, i.e. the key indicators of acid sulphate soil impact in the current setting, were determined. Representative daily runoff and precipitation data was available for the whole study period. The 10th and 90th percentiles for EC and pH were 29–140 mS/m and 3.8–4.6, respectively. While the water quality varied remarkably from year to year, and even within seasons, some regularity was found. The water quality was generally worst in late autumn (water temperature < 5 °C) and in spring. Of all seasons the variations were clearly smallest in spring, indicating that most representative samples can be obtained in this season. There were significant correlations between autumn, early winter and spring water quality within hydrological years. Thus acid and metal surges in spring are somewhat predictable. At base flow conditions (runoff about 1 L/s km² or less), the water quality was relatively good in all seasons. Above base flow conditions, the impact of acid sulphate soils tended to slightly increase with increasing runoff and precipitation, especially in early summer, but not in late summer. No significant signs of dilution during flood conditions (up to 100 L/s km²) were found and neither were there any correlations to rising or falling limbs. The severity of individual summer droughts, which in theory should increase the oxidation of S and acidity in the soils, had little or no impact on the water quality in subsequent autumn and spring. On the other hand, there was a remarkable long-term increase in EC and a corresponding decrease in pH (starting in 1995) after a suite of several very dry summers. After that the water quality did not improve even if the dry summers were followed by some wet summers. This indicates that the temporary pool of readily leachable acidity in the soils is fairly large. Moreover, it indicates that the potential shift towards more extreme global weather conditions (with more severe dry spells) may have significant impacts on the water quality in midwestern Finland, a region that is heavily affected by acidity and metals from acid sulphate soils.     

The effect of water depth on ice-proximal glaciolacustrine sedimentation: Salpausselkä I, southern Finland

The morphology and sedimentology of the Salpausselkä I moraine in southern Finland were examined in detail, together with the distribution of associated eskers and the glacial geology of the surrounding area. Marked contrasts in the form and stratigraphy of the moraine suggest that there were differences in the style and pattern of sedimentation along the ice/lake interface. These variations were influenced by the lake water depth and the nature of the subglacial drainage system. Large individual deltas which built up to water level were the product of conduit focused sedimentation. Lower, narrower coalescing fans of finer material were formed at the ice grounding line by sediment fed from a distributed drainage system. Subglacial conduit systems were found to be unstable where marginal water depths were greatest, favouring the development of a distributed drainage system.     

Hekla 1947, 1845, 1510 and 1158 tephra in Finland: challenges of tracing tephra from moderate eruptions

Several cryptotephra layers that originate from Icelandic volcanic eruptions with a volcanic explosivity index (VEI) of ≤ 4 and tephra volumes of < 1 km³ have previously been identified in Northern Europe, albeit within a restricted geographical area. One of these is the Hekla 1947 tephra that formed a visible fall-out in southern Finland. We searched for the Hekla 1947 tephra from peat archives within the previously inferred fall-out zone but found no evidence of its presence. Instead, we report the first identification of Hekla 1845 and Hekla 1510 cryptotephra layers outside of Iceland, the Faroe Islands, Ireland and the UK. Additionally, Hekla 1158 tephra was found in Finland for the first time. Our results confirm that Icelandic eruptions of moderate size can form cryptotephra deposits that are extensive enough to be used in inter-regional correlations of environmental archives and carry a great potential for refining regional tephrochronological frameworks. Our results also reveal that Icelandic tephra has been dispersed into Finnish airspace at least seven times during the past millennium and in addition to a direct eastward route the ash clouds can travel either via a northerly or a southerly transport pathway.     

Selective sequential dissolution of organic-rich stream sediments from Talvivaara, Finland

Organic-rich stream sediments, a widely used material in geochemical prospecting in Finland, were investigated by analyzing Mn, Fe, Co, Ni, Cu and Zn after a series of selective extractions.Forty-seven organic-rich stream-sediment samples were collected in the vicinity of a sulphide mineralization in Talvivaara, eastern Finland. Loss on ignition of the samples at 500°C was 20–95%. pH of the samples, measured in the water pressed from the samples, was 3.4–6.2 with a mean of 4.2.The < 0.5 mm grain-size fraction was subjected to a sequential extraction as follows: NH₄-acetate for exchangeable cations; cold NH₂OH·HCl for dissolution of Mn oxides; H₂O₂ for destruction of organic material; hot NH₂OH·HCl for dissolution of Fe oxides; HF/HClO₄/aqua regia for dissolving the residue. Each extraction was analyzed by flame AAS for Mn, Fe, Co, Ni, Cu and Zn.Manganese and Co are mostly in exchangeable form and in the residue, while the proportion complexed by the organic components is minimal. Iron and Ni own a lot of exchangeable character although a significant proportion of these elements is complexed by the organic components. Most of Cu is in organic form. Zinc is the element most evenly distributed between extractions.     

Benthic Phosphorus Dynamics in the Gulf of Finland, Baltic Sea

Benthic fluxes of soluble reactive phosphorus (SRP) and dissolved inorganic carbon (DIC) were measured in situ using autonomous landers in the Gulf of Finland in the Baltic Sea, on four expeditions between 2002 and 2005. These measurements together with model estimates of bottom water oxygen conditions were used to compute the magnitude of the yearly integrated benthic SRP flux (also called internal phosphorus load). The yearly integrated benthic SRP flux was found to be almost 10 times larger than the external (river and land sources) phosphorus load. The average SRP flux was 1.25?±?0.56?mmol?m^?2?d^?1 on anoxic bottoms, and ?0.01?±?0.08?mmol?m^?2?d^?1 on oxic bottoms. The bottom water oxygen conditions determined whether the SRP flux was in a high or low regime, and degradation of organic matter (as estimated from benthic DIC fluxes) correlated positively with SRP fluxes on anoxic bottoms. From this correlation, we estimated a potential increase in phosphorus flux of 0.69?±?0.26?mmol?m^?2?d^?1 from presently oxic bottoms, if they would turn anoxic. An almost full annual data set of in situ bottom water oxygen measurements showed high variability of oxygen concentration. Because of this, an estimate of the time which the sediments were exposed to oxygenated overlying bottom water was computed using a coupled thermohydrodynamic ocean?Csea and ecosystem model. Total phosphorus burial rates were calculated from vertical profiles of total phosphorus in sediment and sediment accumulation rates. Recycling and burial efficiencies for phosphorus of 97 and 3%, respectively, were estimated for anoxic accumulation bottoms from a benthic mass balance, which was based on the measured effluxes and burial rates.