Sedimentmikrobioiogie und ihre geologischen Aspekte

The influence of bacteria on recent sediments was first discussed in 1885, whenFischer andGazert were discussing the cycle of substances in the sea as well as in sediments. The influence of bacteria on the cycling of C, N, S, P in recent sediments and the open sea was soon accepted by marine geologists. Nevertheless, only very few experiments have, so far, shown more than qualitative and quantitative data collection in various restricted areas. This is due to the extensive and complicated chain of reactions on the surface of sediments and in the sediment itself. Biologists are asking for the amount of organic and inorganic matter which is reworked and released to the sea. Geologists usually emphasize the amount of substances which are sedimentated. For biologists the sediment is only part of their dominant ecosystem (the sea). While, for geologists the “sea” is only furnishing and influencing their first range system sediment. How much then, are bacteria involved in the slow process of conversion from a recent sediment to sedimentary rocks? Bacteria influence more or less strongly and to a more or less advanced degree of diagenesis:

1. The organic matter in sediments and the final form in which it is found.
2. The anions CO₃ ^2?, NO₃ ^?, OH-, SO₄ ^2?, PO₄ ^3? as well as their intermediate stages and the resulting minerals.
3. The cations H⁺, NH₄ ⁺, Ca²⁺, Fe²⁺, Fe³⁺, and a series of metals which are dissolved or precipitated by microbial activities as for example Fe, Mn, Cu, Ag, V, Co, Mo, Ni, U, Se, Zn.
4. The equilibrium of silicium. At least diatoms and radiolarians are precipitating silica, while other reactions which have been proved are not yet shown to influence marine sediments.
5. p_H-values and oxidation-reduction potentials of the sediment.
6. The composition of interstitial waters.
7. The surface activity of minerals, since bacteria are growing especially on particle surfaces.
8. The energy content and temperature of sediments.
9. The texture of fine grained sediments.
10. The fossilization of microfauna, macrofauna and trace fossils.

Sedimentology and mineralogy may also influence the bacterial activities and the composition of the microflora within sediments. Methods and problems of sediment microbiology are demonstrated by some investigations in the German Bay (North Sea) in connection with the first German Underwater Station (UWL). Ecological work proves to be difficult in various directions. The main cause of difficulties in microbiological work on sediments are the great variety of different factors influencing the environment (microbial, chemical, physical, mineralogical), the difficulty of taking representative samples, and the small amount of data which has been collected so far.     

Hydrological and hydrochemical studies in the permafrost drainage basin of Oobloyah Valley,N-Ellesmere Island,NWT, Canada

During the “Heidelberg-Ellesmere-Island-Expedition” to Oobloyah Valley, N-Ellesmere Island, NWT, Canada in 1978 the summerly water balance of this high arctic catchment area with continuous permafrost was investigated. The following results will be presented:

1. Three hydrogeological areas with different physical parameters, thawing depths and drainage are distinguished and studied on slope I, II and slope III.
2. The climatic situation of summer 1978 was mainly influenced by the change of radiating and cloudy periods. Due to air temperatures (2 m above ground), which never went below 0°C, these periods regulated the thawing of the glaciers and the respective run-off.
3. Most of the winterly snow cover melted before July, thereafter soil thawing and its drainage began. In none of the sediments the latter reached field capacity.
4. Considering the course of daily discharge and soil water balance the three studied streams were characterized by the “Dry-Weather-Discharge-Line”, DWL, of Peri-Creek the “Radiation-Weather-Discharge-Line”, RWL, and the “Cloudy-Weather-Discharge-Line”, CWL, of Nukapingwa River and Heidelberg River.
5. The periglacial streams never had a measurable sediment load not even during snow melt, whereas the glacial and mixed glacial-periglacial streams as Nukapingwa River and Heidelberg River showed a sediment drift depending on their run-off. Only in Peri-Creek the ion concentrations were correlated to discharge.
6. Precipitation (snow plus rain) add up to 51% of the summerly water balance. The glaciers contributed up to 48%, and the actual evapotranspiration is only 1%.

     

Zersetzung von Kalk-Alkali-Gesteinen im rezenten Fumarolengebiet auf Nea Kameni/Santorin/Griechenland

In the present phase of the volcanic activity on Nea Kameni / Santorini / Greece the calc-alkalic volcanic rocks are decomposed by H₂O, CO₂ and SO₂ gases of about 100 °C. Using a method ofGresens (1967) for the determination of gains and losses of compounds five different processes could be distinguished:

1. leaching of compounds
2. enrichment of Ca as gypsum
3. increase of Fe₂O₃ (6%–11%), TiO₂ (0,8%–3%) and Zr
4. enrichment of Al₂O₃ (15%–29%), TiO₂ (0,8%–1,5%) and K
5. increase of Al₂O₃ (15%–26%), Fe₂O₃ (6%–9%), TiO₂ (0,8%–1,3%), Sr, Ba, Pb and Zr

Finally a model for the process of decomposition of calc-alkalic volcanic rocks by sulfuric acid was developed.     

Ein Beitrag zur Vulkanologie Süd-Perus

The Nevado Coropuna (6400 m/19 500 ft) is the largest and highest volcano of Peru and is situated 150 km NW of the town of Arequipa at a distance of 110 km from the Pacific coast. Results of a thorough petrographic study are presented including microprobe and radiometric measurements.

1. The constituent rocks building up the Coropuna volcano are lavas and rhyodacitic ash flows intercalated between older and younger lavas at the foot of the cone. The volcanic edifice rests on older ignimbrite sheets (14 m. y.) exposed only in the surrounding valleys.
2. The lavas are typically latite-andesites which contain some normative quartz in the groundmass. Plagioclase has 37–47% An. The depth of the phenocryst crystallization is calculated at 8–12 km based on the equilibrium between plagioclase, clinopyroxene and groundmass.
3. The Coropuna volcano has existed since the Late Miocene (5 m. y.). Approximately 2 m. y. ago a catastrophic explosion produced large rhyodacitic ignimbrite deposits around the foot of the mountain. Thereafter the effusion of lavas was dominant through Holocene times with the latest lavas becoming slightly more acidic (62% SiO₂).
4. 30–40 km to the W and SW of the Coropuna some outliers of the coastal batholites are exposed. Both their radiometric age (Cretaceous, 97 m. y.) and their chemical composition are in disagreement with the notion of these granodioritic to gabbroic rocks as the intrusive equivalents of the young volcanics.

     

Paläoklima und paläoozeanische Verhältnisse im SW-Pazifik während der letzten 6 Millionen Jahre (DSDP - Site 594, Chatham Rücken, östlich Neuseeland)

Detailed sedimentological investigations were performed on sediments from DSDP-Site 594 (Chatham Rise, east of New Zealand) in order to reconstruct the evolution of paleoclimate and paleoceanographic conditions in the Southwest Pacific during the last 6 million years. The results can be summarized as follows:

1. High accumulation rates of biogenic opal and carbonate and the dominance of smectites in the clay fraction suggest increased oceanic productivity and an equable dominantly humid climate during the late Miocene.
2. During Pliocene times, decreasing contents of smectites and increasing feldspar/quartz ratios point to an aridification in the source area of the terrigenous sediments, culmunating near 2.5 Ma. At that time, accumulation rates of terrigenous components distinctly increased probably caused by increased sediment supply due to intensified atmospheric and oceanic circulation, lowered sea level, and decreased vegetation cover.
3. A hiatus (1.45 to 0.73 Ma) suggests intensified intermediate-water circulation.
4. Major glacial/interglacial cycles characterize the upper 0.73 Ma. During glacial times, oceanic productivity and terrigenous sediment supply was distinctly increased because of intensified atmospheric and oceanic circulations and lowered sea level, whereas during interglacials productivity and terrigenous sediment supply were reduced.
5. An increased content of amphibols in the sediments of Site 594 indicates increased volcanic activities during the last 4.25 Ma.

     

Zur Genese der Migmatite des Beaume-Tales (Mittlere Cévennen,Dép. Ardèche)

Samples of micaschists, gneisses, and migmatites from a sequence of metamorphic subfacies of the Gévennes Médianes (Dép. Ardèche, France) are characterized chemically by

1. a high and only slightly varying Al₂O₃ content (m.v.=17.5₇ wt.-%, stand, dev.=1.804, var. coeff.=0.103).
2. a negligible variation of the molar MgO/MgO+FeO ratio (m.v.=0.504, stand. dev.= 0.066, var. coeff.=0.130), and
3. an insignificant variation of the molar CaO/CaO + Na₂O ratio (m.v.=0.360, stand. dev.=0.014, var. coeff.=0.039).

The Na₂O and K₂O values of the migmatite samples are respectively 14 and 30% higher than those of the samples of the neighbouring gneisses and schists. The concentrations of all other major elements of the migmatites are within the variation limits determined for the gneisses and schists. Samples displaying initial migmatization have the following petrography:

1. The light-coloured portions of the migmatites (leueosome) contain alkalifeldspar, plagioclase, and quartz, the dark-coloured ones (melanosome) are always free of alkalifeldspar and contain, besides ferromagnesian constituents, both plagioclase and quartz.
2. The plagioclase of the melanosome has a remarkably higher An-content (An30–40mol.-%) than that one of the leueosome (An 9–14 mol.-%).

These observations seem to represent petrographic evidence that leueosome and melanosome have been in a restite-melt-relation at a temperature that just reached or slightly exceeded the value necessary to produce the beginning of melting. In addition, major element analyses of separated leueosome portions of samples displaying the petrography mentioned above have been undertaken. Normative Qz ∶ Ab: Or-ratios calculated from these analyses vary within very narrow limits about the average value of Qz ∶ Ab ∶ Or=36 ∶ 31 ∶ 33. Using the diagrams of von Platen (1965) concerning the crystallization of granitic melts the petrographic findings can be verified from analytical results, i.e. the migmatites of the Beaume valley are considered to be products of minimum temperature melting of the gneisses which still occur unaltered in adjoining areas of lower metamorphic grade.     

The Araguainha astrobleme/Central Brazil

The following facts have supported the origin of the Araguainha circular structure in Central Brazil by a meteoritic impact:

1. the almost circular contour
2. the impact-morphologic sequence including a central uplift, ring walls and a basin rim of escarpments
3. outcrops of suevites and mixed breccias
4. the evidence of shock metamorphism
5. the presence of shatter cones, and
6. negative anomalies of the total intensity of the magnetic field at the center of the ring structure.

     

Clay-lead sorption relations

Bays, lagoons, and estuaries are sites where normal physicochemical processes result in accumulations of sediment and certain chemicals. Changes in water velocity and chemistry, and chemical interactions of sediment, biota, and water are factors that contribute to concentrating trace metals in coastal and lake sediments. To evaluate whether lead concentration is affected by mineralogy, kaolinite, illite, montmorillonite, and a zeolitic tuff were suspended in 10 and 20 mg/l concentrations of lead solutions [Pb(NO₃)₂] which were pH-adjusted incrementally through a range of 2.5 to 11.0. Samples were centrifuged after 24 hours to separate liquid from suspended sediment. Sediment-free solutions were run as controls. Lead concentrations were determined by atomic adsorption spectrophotometry. Results indicate that montmorillonite (Wyoming Bentonite) particles serve as lead adsorption nuclei over a broad pH range. Maximum sorption occurs as the solution reaches a pH of about 7.5. The kaolinite clay from Georgia strongly adsorbs trace amounts of lead at pH ranging from 3.0 to 4.5, where up to 95 percent of the lead is adsorbed by the clay. Little adsorption difference was found between the Fithian illite clay and zeolitic tuff from the Nevada Test Site in comparison to sediment-free solutions which were pH-adjusted. In concentrations of 10 to 20 mg/l montmorillonite and kaolinite clays serve as nucleation sites capable of adsorbing up to 95 percent of trace concentrations of lead within 24 hours. It appears that accumulations of lead in coastal lake and estuarine sediments are significantly influenced by:

1. pH changes which occur as river and coastal waters mix resulting in precipitation of lead, and
2. sorption of lead by suspended clays.

     

Kyanite eclogites

Prior experimental work has shown that in the laboratory the mineralogy of eclogites is sensitive to the ratio of CaO ∶ MgO ∶ FeO and that the reaction pyroxene + kyanite?garnet + quartz proceeds to the right at high pressures in rocks rich in magnesium and to the left in rocks rich in calcium and iron. Typical basalts crystallized at high pressure never contain kyanite. The chemistry and mineralogy of a large number of naturally occurring eclogites show they belong to three classes.

1. Kyanite-free magmatic eclogites, rich in magnesium, from:
2. kimberlites
3. dunites and serpentinites.
4. Kyanite-bearing eclogites and grosspydites rich in CaO and low in FeO with intermediate MgO from:
5. kimberlites
6. gneisses.
7. Kyanite-free eclogites of metamorphic origin rich in iron with low magnesium and intermediate amounts of calcium from:
8. glaucophane schists
9. gneisses.

     

Kationenaustausch an Plagioklasen

A series of K-plagioclases have been produced metastably by ion-exchanging the plagioclases in KCl-melt. Chemical analyses and re-exchange experiments (with NaCl-melt) have proved that the K-plagioclases are truly isomorphous with plagioclases. Because of their isomorphous nature it was possible to mix them in different proportions and homogenise them, thereby producing ternary feldspars of different compositions in the system Or-Ab-An. A comparative study of the lattice constants of plagioclases, their K-equivalents and the different ternary feldspars calculated using powder data leads to the following conclusions:

1. It is possible to dertermine by X-ray methods the anorthite content of a plagioclase to an accuracy of ±1% An.
2. The influence of the ionic size of the bigger cations Na, Ca, and K and that of order/disorder are different on different lattice constants and it is possible to distinguish these two effects.
3. The b-parameter indicates a definite structural change in plagioclases at about 25–30% An.
4. It is possible to predict the average Al/Si-distributions in the four different positions T_1(o), T_1(m), T_2(o) and T_(m) of all plagioclases of all stable structural states, using the c-parameter of their K-equivalents.

     

Tonminerale in normalsedimenten,hydrothermal beeinflu\ten sedimenten und Erzschlämmen des Roten Meeres

From 14 deeps and other regions of the Red Sea totally 226 samples from 28 cores recovered during the VALDIVIA cruises (1971, 1972) were investigated according to their clay mineral content (<2μm resp. < 6.3 μm) after carbonate dissolution. Three facies groups are to distinguish:

1. normal sediments: dominance of chlorite, kaolinite, illite, small amounts of smectite and sepiolite. Two palygorskite types are present only in a few samples.
2. normal sediments with hydrothermal influence: clay mineral paragenesis similar like that of normal sediments; but increase of smectite and presence of goethite in each sample; partly small contents of talc.
3. heavy metal deposits: dominance of iron-bearing smectite, partly with amorphous components resp. pure ore mineral assemblages with authigenic silicates (talc, quartz, opal, chrysotile, sepiolite, palygorskite, chlorite).

Crystallinity of the clay and ore minerals is independent from sedimentary overburden. Sepiolite shows in small amounts a wide distribution; palygorskite₂ (d₁₁₀=11.3 Å) yields locally an increased concentration in the range of pteropod layers cemented by aragonite. The environment of ore deposits is characterized by iron-bearing smectite besides the ore minerals.     

Geochemistry and origin of granitic rocks,Scourian Complex,NW Scotland

Concordant granite sheets from the granulite facies Scourian Complex, N.W. Scotland exhibit the following features:

1. a common planar fabric with their host pyroxene granulites;
2. the presence of an exsolved ternary feldspar phase;
3. a low-pressure, water-saturated minimum composition;
4. K/Rb ratios (450–1,350) distinctly higher than most upper crustal granites but similar to the surrounding granulites;
5. low absolute concentrations of the rare earth elements (REEs), light REE enrichment, and large positive Eu anomalies.

It is proposed that the granite sheets have originated by anatexis of gneisses undergoing granulite facies metamorphism — gneisses that were already essentially dry and depleted in incompatible elements. Their unusual trace element chemistry may be explained by either disequilibrium melting and/or sub-solidus reequilibration of the granite sheets with the surrounding gneisses. Isotopic and trace element data suggest that cross-cutting, potash-rich pegmatites represent reworking of the granite sheets during a later amphibolitization.     

Geologische und geochemische Untersuchungen im Zentralgneis und in der Greiner Schiefer Serie (Zillertaler Alpen,Tirol)

Geologic, petrological and geochemical investigations have been carried out in the western part of the “Zillertaler Alpen”. Important results are:

1. The premetamorphic material of the Greiner series consists of conglomerates, breccias, arcosic-sandstones or greywackes, bituminous shales, volcanic lavas and tuffs.
2. The southern part of the “Zentralgneis” shows a differentiation trend from alkaline granite to quarzdiorite with predomination of granodiorite.
3. Chemical relationships of granodiorite to its restitic inclusions allow the supposition of a palingenetic origin of the granitic rocks.
4. At least two stages of metamorphism can be differentiated.
5. Parts of the Greiner series, covered by triassic metasediments, are supposed to be of Permian age. A lower age boundary can not yet be given.
6. Some vertical, northeast striking faults with throws of more than 1 or 2 kilometers produced southward verging drag folds.
7. Geodynamic aspects, revealed from regional metamorphism and tectonics, are discussed.

     

Comparison between “magnetic” and sedimentary fabric in graded and cross-laminated sand layers,Southern California

Paleocurrent directions can be reconstructed by determining optically the preferred orientation of longest grain axes of sediments; this can be estimated by measuring the anisotropy of magnetic susceptibility (Rees, 1965). In order to check the applicability of both methods, the orientation of large- and small-scale sedimentary structures (cross-bedding, sole markings, grain orientation) was compared with the “magnetic fabric” of some sand and silt layers of different ages and origins:

1. Rosario Formation (Late Cretaceous), La Jolla: thin siltstone layers with small-scale current-ripple cross-lamination;
2. Monterey and Topanga Formations (Miocene, Los Angeles Basin): graded and laminated sandstone beds (“turbidites”);
3. Holocene submarine La Jolla Fan: graded and cross-laminated sand layers (Rees, v.Rad &Shepard, 1968).

Most of the investigated sand layers have a “primary-style” magnetic fabric, characterized by well-grouped, horizontal maximum susceptibility axes, sometimes slightly imbricated upcurrent, minimum susceptibilities normal to the bedding, and intermediate values of the factor q (about 0.1–0.5), suggesting moderately strong current conditions during deposition. The orientation of maximum susceptibility axes correlates with the directions of sand transport, inferred from cross-lamination foresets and sole markings (a). Also conventional optical grain orientation measurements give very similar directions as maximum susceptibilities (b). In Recent deep-water sand layers (c) cross-lamination foresets and maximum susceptibility axes are parallel, and influenced by the local morphology (e. g. fan-valley axis). Since current-parallel orientation of the longest grain axes and maximum susceptibility axes is prevailing in deep-water sands, the magnetic method is a useful tool for palcocurrent analysis. Characteristic differences of the magnetic fabrics from different depositional environments may also give clues to the mechanisms of sediment transport.     

The sedimentation of copper-bearing shales (Kupferschiefer) in the sudetic foreland

The profile of the copper-bearing shales (Kupferschiefer) displays 3 types of lithological developments of the Sudetic Foreland:

in reduction facies: with the notably diminishing of participation of clay minerals and organic substance from bottom to top.

Many horizons of concentration of copper, lead and zinc are present.

in oxidation facies: where marley shales are forming, the metals decrease to trace contents.

in intermediate zones, from reduction facies to oxidation facies shales, the lithological formation is changing and the greatest variability is encountered in the intensity of metal contents.

The concentrations of copper sulphides occur in lagoonal areas in which an oxigen deficiency was associated with a great amount of organic matter. The beds formed in the oxidation facies represent the coastal zones of an open sea basin where the influence of inflow and outflow were considerable.     

Gehlenite stability in the system CaO-Al2O3-SiO2-H2O-CO2

P, T, \(X_{{\text{CO}}_{\text{2}} }\) relations of gehlenite, anorthite, grossularite, wollastonite, corundum and calcite have been determined experimentally at P _f =1 and 4 kb. Using synthetic starting minerals the following reactions have been demonstrated reversibly

1. 2 anorthite+3 calcite=gehlenite+grossularite+3 CO₂.
2. anorthite+corundum+3 calcite=2 gehlenite+3 CO₂.
3. 3anorthite+3 calcite=2 grossularite+corundum+3CO₂.
4. grossularite+2 corundum+3 calcite=3 gehlenite+3 CO₂.
5. anorthite+2 calcite=gehlenite+wollastonite+2CO₂.
6. anorthite+wollastonite+calcite=grossularite+CO₂.
7. grossularite+calcite=gehlenite+2 wollastonite+CO₂.

In the T, \(X_{{\text{CO}}_{\text{2}} }\) diagram at P _f =1 kb two isobaric invariant points have been located at 770±10°C, \(X_{{\text{CO}}_{\text{2}} }\) =0.27 and at 840±10°C, \(X_{{\text{CO}}_{\text{2}} }\) =0.55. Formation of gehlenite from low temperature assemblages according to (4) and (2) takes place at 1 kb and 715–855° C, \(X_{{\text{CO}}_{\text{2}} }\) =0.1–1.0. In agreement with experimental results the formation of gehlenite in natural metamorphic rocks is restricted to shallow, high temperature contact aureoles.     

Forest condition and forest damages — contribution of remote sensing to different inventory approaches

The development of inventory activities in the field of forest damage assessment and monitoring during the last decade in Germany and the present state are recorded as far as remote sensing has been involved. Any forest inventory is influenced by external factors, and the resulting difficulties for an introduction of new technologies are described. The following tasks and/or methods are discussed:

-global approaches to deforestation monitoring

-working experience from local and regional case studies

-vegetation and vegetation-damage monitoring in ”urban forestry”

-sampling approaches for large areas

-the contribution of spectral signatures and satellite remote sensing to damage assessment

     

The loess-paleosol and related subaereal sequence in Hungary

The loess of type localities is subdivided into 3 subseries on the basis of the paleosols allowing even an Eurasian comparison for their lithostratigraphy.

1. The upper young loess (8–10 m) is most widespread, characterized by 3 sandy loess and 2 intercalated humic loess horizons. The ages of the humic loess horizons H₁, H₂ are c. 16 ka and 20 ka BP, respectively.
2. The lower young loess (15–20 m) contains 4 loess packets and 3 chernozem-like paleosols, usually doubled soil complexes (designated MF, BD, BA). The MF paleosol complex, first member of lower young loess is c. 27–28 ka BP (C¹⁴ and TL dating). The lower young loess is underlain by a brown forest soil and chernozem-like paleosol-assemblage (MB), probably formed during the last interglacial (c. 105–125 ka BP).
3. The old loess (c. 20 m) is generally characterized by 6–7 loess, mainly brown forest soil and 2 interbedded fluvial sand layers. The lowermost old loess member and an ochre-red paleosol lie below the Brunhes-Matuyama boundary (0,73 Ma).
4. The loess is underlain by a subaerial non-loessic sequence (20–40 m) with 5–10 red soils, red clays mostly directly superimposed on and locally interbedded by sand and silty sand. At the base of this sequence of red paleosols usually Uppermost Miocene inland sea deposits are found.

It can be concluded that the reddish paleosol developed under climatic, and in general, ecological conditions (probably warm subhumid with rapid cyclical climatic changes) differing from the cold and semiarid or semidesert environments of typical loess formation. The former conditions were characteristic — from the Lower Pliocene to the Lower Pleistocene — on continental or global scales.     

The structural geology of the Dalradian rocks of Slieve Gamph,Cos. Mayo and Sligo,Western Ireland

The paper presents novel information on the Caledonian orogeny in Ireland. A series of Dalradian (Upper Precambrian-Lower Cambrian) metasedimentary rocks occur as an envelope to a granitic igneous complex at Slieve Gamph, Western Ireland. These metasedimentary rocks have been deformed at several distinct times and evidence is shown for the following sequence of events:

1. formation of major nappe structures and a tectonic slide. The axial-plane traces of the folds probably trended N. E.-S. W.
2. formation of upright, gently plunging folds with axial-plane traces of the folds trending N. E.-S. W. Emplacement of the components of the Slieve Gamph igneous complex.
3. formation of a conjugate set of folds:
   1. Open folds with N. N. E.-S. S. W. trending axial-planes which dip to the east,
   2. Open folds with E.W. trending axial-planes which dip to the north.
4. formation of kink-bands, open and conjugate folds with an axialplane trace trending N. W.-S. E.

Late phase of faulting. No isotopic dates are available for these structural events.