Coprecipitation of alkali metal ions with calcium carbonate

The coprecipitation of alkali metal ions (Li⁺, Na⁺, K⁺ and Rb⁺) with calcium carbonate has been studied experimentally and the following results have been obtained:

• 1.(1) Alkali metal ions are more easily coprecipitated with aragonite than with calcite.
• 2.(2) The relationship between the amounts of alkali metal ions coprecipitated with aragonite and their ionic radii shows a parabolic curve with a peak located at Na⁺ which has approximately the same ionic radius as Ca²⁺.
• 3.(3) However, the amounts of alkali metal ions coprecipitated with calcite decrease with increasing ionic radius of alkali metals.
• 4.(4) Our results support the hypothesis that
  • 4.1.(a) alkali metals are in interstitial positions in the crystal structure of calcite and do not substitute for Ca²⁺ in the lattice, but
  • 4.2.(b) in aragonite, alkali metals substitute for Ca²⁺ in the crystal structure.
• 5.(5) Magnesium ions in the parent solution increase the amounts of alkali metal ions (Li⁺, Na⁺, K⁺ and Rb⁺) coprecipitated with calcite but decrease those with aragonite.
• 6.(6) Sodium-bearing aragonite decreases the incorporation of other alkali metal ions (Li⁺, K⁺ and Rb⁺) into the aragonite.

     

Development of engineering geology in western United States

Geologic concepts and scientific-technical guidance for the planning-design and construction of engineered works was recognized in Europe by the 1800s and by the early 1900s in North America. This early geologic knowledge and experience provided the rudimentary principles that guided practitioners of the 19th century in serving the emerging projects in western United States. Case studies review the scientific-technical lessons learned and the legacy of geologic principles established in the planning and construction of major civil, mining, and military engineered works in the western states. These contributions to GeoScience knowledge and engineering geology practice include:

• •Tunnels and aqueducts across active fault zones, beneath young volcanic features, groundwater-charged faults, and land subsidence mitigation.
• •Controversial foundation design, Folsom and Auburn dams, Golden Gate Bridge.
• •Protective underground construction chambers, safety dependent geologic setting.
• •Geologic mapping as database management leasing, maintenance railroad trackway.
• •Causeway Great Salt Lake, geo-risks calculated, mitigated ‘as-constructed’.
• •Nuclear powerplants seismic design.
• •Urban Land-Use, on-going processes, acceptable geo-risks.
• •Dwelling Insurance, insuree's responsibilities.
• •Selecting technique/method to mitigate risk, preferably based on extensive database, evaluation of characteristics and historical origin adverse features/conditions that constitute a geo-risk.

     

Aridification — Climate change in South-Eastern Europe

Climatic change in SE Europe can be characterized by the term aridification, which means increasing semi-aridity, manifested in an increase of mean annual temperature and at the same time in a decrease in the yearly precipitation.The paper deals with research results obtained within the framework of the MEDALUS II project (funded by the Commission of the European Communities). The project had the following objectives:

• 1.(i) Assessment of the impact of global change on the climate of the investigated area, including possible future climates.
• 2.(ii) Physical processes of aridification, including studies of groundwater level change, soil moisture profile dynamics, soil development, vegetation change and soil erosion.
• 3.(iii) Land use change, involving research on present land use and suggestions for the future.

Various methods were applied with respect to the different research objectives.

• 1.(i) Statistical analysis of climatic oscillations and computer runs of climatic scenarios,
• 2.(ii) Analysis of ground water data, mapping and analysis of soils and vegetation, assessment of present and future soil, and
• 3.(iii) Land capability assessment through ranking environmental conditions according to the demands of the most widely grown arable crops in Hungary.

According to our results i) the average annual warming during the last 110 years was +0.0105 °C, and precipitation decreased by 0.917 mm/year; ii) a decline of −2 to −4 m in the annual mean groundwater level can be detected in the most sensitive areas, with gradual lowering of the water table in alkali ponds; complete desiccation of some of them severs the direct contact between groundwater and salt-affected soils, the solonchak soil dynamics cease, helophile and hygrophile plant associations disappear, and consequent changes in the soil erosion regime are likely to lead to disastrous erosion in the future; iii) the climatic changes induce a transformation in land use from arable crops to plantations, starting with orchards.     

Chemical modelling of kerogens

Models of kerogens belonging to the three classical Types have been represented at the following evolution stages:

• •-beginning of diagenesis (sensu-stricto),
• •-beginning of catagenesis,
• •-end of catagenesis.

Chemical models are drawn, using analytical data obtained on natural samples: elemental analysis, electron microscopy, ¹³C NMR, thermogravimetry, functional analysis and pyrolysis.In order both to get a statistical representation and make comparisons easier, the same molecular weight of about 25,000 has been chosen for the different models of kerogens at the beginning of the diagenesis stage.     

Seismic patterns in Northern China and the characteristics of the epicentral distribution of the medium strong earthquakes before the large events

In this paper, the seismic pattern in Northern China from 30 ° to 42 ° N latitude and 104 ° to 125 ° E longitude, and the characteristics of the epicentral distribution before large events are presented. The results suggest that:

• 1.(1) the earthquakes in the region are mainly located in the orthogonal curvilinear network formed by the seismic belts;
• 2.(2) the larger earthquakes (M ⩾6) occurred mainly in the nodal regions of this grid:
• 3.(3) the strike of the fracture planes of the earthquakes coincided with the directions of the seismic belts;
• 4.(4) the pattern of medium strong earthquakes (M ⩾ 4.7) prior to thirteen large earthquakes (M⩾ 7) are analysed to be of three types:
  • 4.1.(a) mainly arranged along the two intersecting belts,
  • 4.2.(b) randomly distributed,
  • 4.3.(3) forming seismic gaps.

A theoretical basis and rules for drawing the orthogonal grid is presented, and an idea for the prediction of the sites of future earthquakes in Northern China is suggested.     

Influence of upwelling Zechstein sulphate on the concentration and isotope signature of sedimentary sulphides in a fluvioglacial sand aquifer

Very low concentrations of total S, mainly sedimentary sulphides, were quantitatively extracted from Quaternary sands of the Elbe Basin, using HNO₃, Br₂ and HCl, to distinguish 3 aquifer zones:

• •an upper aerobic section, containing low concentrations (only a few ppm) of non-sulphidic S compounds,
• •the central and lower part of the aquifer, dominated by ³⁴S-depleted sedimentary Fe sulphides, formed by reduction of infiltrating SO₄, derived from groundwater recharge, and
• •the lowest 5–10 m of the aquifer, containing high concentrations of ³⁴S-enriched sulphides.

The latter originated from dissolved Zechstein SO₄, which was reduced during upwelling through the organic-rich Tertiary aquiclude. H₂S and HS⁻ reacted and precipitated with Fe and other metal ions shortly after migration into the C_org-poor Quaternary aquifer. The sulphides yield valuable information concerning the ascent of confined saline solutions from isolated Zechstein evaporites inside the “Mühlberger Graben”, which is covered by Cenozoic sediments and whose extension and boundaries are therefore not well defined. Only a few locations, close to faults and geological windows, show deep-water admixture sufficiently strong to cause visible changes in hydrochemistry and isotopic ratios of SO₄ and DIC directly above the base of the Quaternary. Sulphides showing different origins may possibly be used in other areas to provide information concerning underlying geology and hydrodynamics.     

Measurements and interpretations of36Cl in groundwater,Milk River aquifer,Alberta, Canada

The³⁶Cl/Cl ratios of 12 groundwater samples from the Milk River aquifer were determined by accelerator mass spectrometry. Using known Cl concentrations,³⁶Cl concentrations were deduced. Approximately linear relations were observed between the logarithm of the³⁶Cl concentration, the Cl concentration, and the distance from the recharge area along two flow paths. The results are discussed in two approaches:

• (1)in an interpretation of the linear relation between logarithm of the³⁶Cl concentration and Cl concentration excluding and includingin situ production of³⁶Cl;
• (2)in a diffusion model. The increase of the Cl concentration with the distance from the recharge area is considered to be due to diffusion of Cl from the underlying confining Colorado shale to the aquifer.

Flow velocities ranging between 0.04 and 0.14 m/a, and ages of the groundwater between 0.6 and 2 Ma are obtained at a distance of 80 km from the recharge area.     

Nature of particulate organic matter in the River Indus,Pakistan

Suspended sediments from the Indus River collected during 1981 through 1983 were analyzed for POC and its constituent fractions including amino acids, amino sugars and sugars. Percentage of POC decreased with increasing suspended matter concentrations, which suggested dilution of organic matter by mineral matter.The concentrations of amino acids, amino sugars and sugars varied, respectively, between 180 and 2000 μg/l, 5 and 125 μg/l, and 60 and 1100 μg/l. Their contributions to POC varied between 2 and 60% for amino acids and amino sugars, and between 2 and 15% for sugars. They were high during low sediment discharge (February to June), and low during high sediment discharge (August and September). Suspended sediments associated with high sediment discharge periods were characterized by low ratios of:

• 1.(i) aspartic acid:β-alanine
• 2.(ii) glutamic acid:γ-aminobutyric acid
• 3.(iii) amino acids:amino sugars
• 4.(iv) hexoses:pentoses. These and the relative distribution pattern of the monosaccharides such as galactose, arabinose, mannose and xylose indicated that, not only dilution, but also differences in the sources and processes affect the POC transport in the Indus River. These result in transport of biodegraded organic matter during high sediment discharge periods: this appears to be common to other major rivers of the region, with depositional centers in deep sea areas. These rivers, with their high sediment loads, could contribute up to 8 to 11% of the global annual organic carbon burial in marine sediments.

     

A quantitative fluorescence technique for evaluating thermal maturity: Instrumentation and examples

Fluorescence microscopy is useful not only for identifying most of the oil-prone organic matter (macerals) in sedimentary rocks and coals but also for assessing their thermal maturities (ranks). This report introduces a violet-light excitation system which induces more than one order of magnitude stronger fluorescence intensity that the commonly used UV-light excitation system. The red/green quotient from violet-light excited fluorescence, Q_v, of sporinite can be easily measured using this system. Several examples using coal and cuttings samples are presented to demonstrate the use of this technique for evaluating the thermal maturities of coals and sedimentary rocks.From the results of our studies we conclude that:

• 1.(1) Violet-light excited fluorescence from sporinites can be routinely measured to assess thermal maturity.
• 2.(2) Spectral (Quantitative) fluorescence technique is useful for evaluating thermal maturity when samples are poorly polished or deficient in vitrinite.
• 3.(3) Visual (Strew-mounted) kerogen slides can not be used for fluorescence measurements unless a non-fluorescent mounting medium is used.

     

Chondrules in the Murray CM2 meteorite and compositional differences between CM-CO and ordinary chondrite chondrules

Bulk compositions were determined by broad-beam electron microprobe analysis for thirteen of the least aqueously altered chondrules in Murray (CM2). These and literature data reveal compositional differences between CM-CO and ordinary chondrite (OC) chondrules:

• 1.(a) CO chondrules are richer in refractory lithophiles and poorer in Cr, Mn and volatile lithophiles than OC chondrules; much lower refractory lithophile abundances in CM chondrules resulted from aqueous alteration,
• 2.(b) in CM-CO chondrites, abundances of refractory lithophiles are higher in nonporphyritic than porphyritic chondrules, whereas in H-L-LL3 chondrites the converse is true,
• 3.(c) Cr ranges are greater and Cr and Mn correlate more strongly in chondrules in CM-CO than in H-L-LL3 chondrites.

We find evidence for two important lithophile precursor components of CM-CO chondrite chondrules:

• 1.(1) pyroxene- and refractory-rich, FeO-poor;
• 2.(2) olivine-rich, refractory and FeO-poor.

The occurrence of a few FeO-rich chondrules attests to a third component similar to matrix: olivine- and FeO-rich, refractories not characterized. The first two components differ from those inferred for OC chondrules, consistent with formation at different locations. The pyroxene- and refractory-rich, FeO-poor lithophile precursor component probably formed by an incomplete evaporation of presolar silicates that brought these materials into the enstatite stability field.     

Porphyry deposits of the Urals: Geological framework and metallogeny

Most of the Cu (± Mo,Au) porphyry and porphyry-related deposits of the Urals are located in the Tagil-Magnitogorsk, East-Uralian Volcanic and Trans-Uralian volcanic arc megaterranes. They are related to subduction zones of different ages:

• (1)Silurian westward subduction: Cu-porphyry deposits of the Birgilda-Tomino ore cluster (Birgilda, Tomino, and Kalinovskoe) and the Zeleny Dol Cu-porphyry deposit;
• (2)Devonian Magnitogorsk eastward subduction and the subsequent collision with the East European plate: deposits and occurrences are located in the Tagil (skarn-porphyry Gumeshevskoe etc.) and Magnitogorsk terranes (Cu-porphyry Salavat and Voznesenskoe, Mo-porphyry Verkhne-Uralskoe, Au-porphyry Yubileinoe etc.), and probably in the Alapaevsk-Techa terrane (occurrences of the Alapayevsk-Sukhoy Log cluster);
• (3)Late-Devonian to Carboniferous subduction: deposits located in the Trans-Uralian megaterrane. This includes Late-Devonian to Early Carboniferous Mikheevskoe Cu-porphyry and Tarutino Cu skarn-porphyry, Carboniferous deposits of the Alexandrov volcanic arc terrane (Bataly, Varvarinskoe) and Early Carboniferous deposits formed dew to eastward subduction under the Kazakh continent (Benkala, etc.).
• (4)Continent-continent collision in Late Carboniferous produced the Talitsa Mo-porphyry deposit located in the East Uralian megaterrane.

Porphyry mineralization of the Magnitogorsk megaterrane shows an evolving relationship from gabbro-diorite and quartz diorite in the Middle Devonian (Gumeshevskoe, Salavat, Voznesenskoe) to granodiorite-plagiogranodiorite in the Late Devonian (Yubileinoe Au-porphyry) and finally to granodiorite in the Carboniferous (Talitsa Mo-porphyry) with a progressive increase in total REE, Rb and Sr contents. This corresponds to the evolution of the Magnitogorsk terrane from a volcanic arc which gave place to an arc-continent collision in the Famennian.     

Mineralogy and petrology of alkaline granophyric xenoliths from the Thorsmörk ignimbrite,southern Iceland

The Thorsmörk ignimbrite, southern Iceland, contains a suite of granophyre xenoliths displaying magmatic or high-temperature sub-solidus mineral assemblages. These granophyres are consanguineous with the erupting comenditic magma. Four types of mineral assemblages are distinguished:

• 1.(A) oligoclase, edenitic hornblende, salitic pyroxene, magnesian biotite, magnetite and sphene;
• 2.(B) oligoclase, manganoan to sodic ferro-augite, fayalite, richterite, ilmenite and magnetite;
• 3.(C) anorthoclase, ferrohedenbergite to aegirine hedenbergite, ilmenite, magnetite and (riebeckite);
• 4.(D) cryptoperthite, aegirine hedenbergite to (aegirine), aenigmatite, arfvedsonite, ilmenite and magnetite.

Geothermometry shows that the xenoliths have crystallized between 900°C and 500°C at moderate oxygen fugacities, just above the FMQ buffer. It is further demonstrated that a hot vapour phase heavily charged with sodium and halogens, played a major role in the late sub-solidus crystallization of the different types.     

Compositions and textures of relic forsterite in carbonaceous and unequilibrated ordinary chondrites

Several percent of the olivine in the C2, C3 and unequilibrated ordinary chondrites (UOC) can be distinguished by blue cathodoluminescence (CL) and an unusual composition for forsterite. This olivine has the following textural features:

• 1.(1) forms cores in single olivine grains;
• 2.(2) shows subhedral to euhedral boundaries against rim olivine;
• 3.(3) rarely contains inclusions;
• 4.(4) has embayments containing olivine like that of the rim;
• 5.(5) occurs within chondrules especially in UOC meteorites.

The blue olivine is always Fe-poor (0.25 < FeO < 1.0%) and shows the following average and maximum values (%): Al₂O₃ (0.25, 0.5), TiO₂ (0.05, 0.09), CaO (0.5, 0.8), Cr₂O₃ (0.15, 0.5), and MnO (0.02, 0.15); vanadium is present. Within a single olivine and within all blue olivines Al, Ca and Ti are strongly positively correlated as are Mn, Fe, and Cr in olivine surrounding the blue. The blue cores are not zoned but each element shows a marked change at the boundary of the blue with Al showing the most rapid change. These are interpreted as diffusion profiles between rim and core olivine.Textures suggest initial free growth probably from a gas and later addition of olivine by liquid crystallization to form single crystals or chondrules. The unusual olivine composition indicates high temperature growth from a refractory-rich reservoir with Al entering olivine in tetrahedral coordination. Vapor growth is suggested as the process allowing the high minor element levels. The occurrence of blue olivine in all primitive meteorites indicates that it is relic material which was widespread prior to chondrule and hence meteorite formation. Similarities in composition exist between this relic olivine and olivine of cosmic dust and Deep Sea Particles pointing to this olivine being a common component in all primitive extraterrestrial material.     

Ore mineralization related to geological evolution of the Karkonosze–Izera Massif (the Sudetes,Poland) — Towards a model

The Karkonosze–Izera Massif is a large tectonic unit located in the northern periphery of the Bohemian Massif. It includes the Variscan Karkonosze Granite (about 328–304 Ma) surrounded by the following four older units:

• -Izera–Kowary (the Early Paleozoic continental crust of the Saxothuringian Basin),
• -Ještĕd (the Middle Devonian to Lower Viséan sedimentary succession deposited on the NE passive margin of the Saxothuringian Terrane), out of the present study area,
• -Southern Karkonosze (metamorphosed sediments and volcanics filling the Saxothuringian Basin), out of the present study area,
• -Leszczyniec (Early Ordovician, obducted fragment of Saxothuringian Basin sea floor).

The authors present a genetic model of ore mineralization in the Karkonosze–Izera Massif, in which ore deposits and ore minerals occurrences are related to the successive episodes of the geological history of the Karkonosze–Izera Massif:

• -formation of the Saxothuringian Basin and its passive continental margin (about 500–490 Ma)
• -Variscan thermal events:
  • -regional metamorphism (360–340 Ma)
  • -Karkonosze Granite intrusion (328–304 Ma)
• -Late Cretaceous and Neogene-to-Recent hypergenic processes.

The oldest ore deposits and ore minerals occurrences of the Karkonosze–Izera Massif are represented by pyrite and magnetite deposits hosted in the Leszczyniec Unit as well as by magnetite deposit and, presumably, by a small part of tin mineralization hosted in the Izera–Kowary Unit. All these deposits and occurrences were subjected to the pre-Variscan regional metamorphism.Most of the Karkonosze–Izera Massif ore deposits and occurrences are related to the Karkonosze Granite intrusion. This group includes a spatially diversified assemblage of small ore deposits and ore mineral occurrences of: Fe, Cu, Sn, As, U, Co, Au, Ag, Pb, Ni, Bi, Zn, Sb, Se, S, Th, REE, Mo, W and Hg located within the granite and in granite-related pegmatites, in the close contact aureole of the granite and within the metamorphic envelope, at various distances from the granite. Assuming world standards, all these deposits are now uneconomic. Various age determinations indicated that ore formation connected with the Karkonosze Granite might have taken place mostly between about 326 and 270 Ma.The last ore-forming episode in the Karkonosze–Izera Massif is related to hypergenic processes, particularly important in the northern part of the massif, in the Izera–Kowary Unit where some uranium deposits and occurrences resulted from the infiltration of ore solutions that originated from the weathering of pre-existing accumulations of uranium minerals. A separate problem is the presence of oxidation zones of ore deposits and occurrences, both the fossil and the recent.A full list of ore minerals identified in described deposits and occurrences of the Karkonosze–Izera Massif together with relevant, key references is presented in the form of an appendix.     

Laihunite—A new iron silicate mineral

Laihuite reported in the present paper is a new iron silicate mineral found in China with the following characteristics:

1. This mineral occurs in a metamorphic iron deposit, associated with fayalite, hypersthene, quartz, magnetitc, etc.
2. The mineral is opaque, black in colour, thickly tabular in shape with luster metallic to sub-metallic, two perfect cleavages and specific gravity of 3.92.
3. Its main chemical components are Fe and Si with Fe³⁺>Fe²⁺. The analysis gave the formula of Fe Fe _1.00 ³⁺ ·Fe _0.58 ²⁺ ·Mg _0.03 ²⁺ ·Si_0.96O₄.
4. Its DTA curve shows an exothermic peak at 713°C.
5. The mineral has its own infrared spectrum distinctive from that of other minerals.
6. This mineral is of orthorhombic system; space group:C _2h ^/5 ?P2₁/c; unit cell:α=5.813ű0.005,b=4.812ű0.005,c=10.211ű0.005,β=90.87°.
7. The Mössbauer spectrum of this mineral is given, too.

     

The geothermal gradient map of Central Tunisia: Comparison with structural,gravimetric and petroleum data

Five hundred and fifty temperature values, initially measured as either bottom-hole temperatures (BHT) or drill-stem tests (DST), from 98 selected petroleum exploration wells form the basis of a geothermal gradient map of central Tunisia. A “global-statistical” method was employed to correct the BHT measurements, using the DST as references. The geothermal gradient ranges from 23° to 49°C/km. Comparison of the geothermal gradient with structural, gravimetric and petroleum data indicates that:

• 1.(1) the general trend of the geothermal gradient curves reflects the main structural directions of the region,
• 2.(2) zones of low and high geothermal gradient are correlated with zones of negative and positive Bouguer anomalies and
• 3.(3) the five most important oil fields of central Tunisia are located near the geothermal gradient curve of 40° C/km.

Such associations could have practical importance in petroleum exploration, but their significance must first be established through further investigation and additional data.     

Phase equilibria among pumpellyite,lawsonite, epidote and associated minerals in low grade metamorphic rocks

Phase relations of pumpellyite, epidote, lawsonite, CaCO₃, paragonite, actinolite, crossite and iron oxide are analysed on an Al-Ca-Fe³⁺ diagram in which all minerals are projected from quartz, albite or Jadeite, chlorite and fluid. Fe²⁺ and Mg are treated as a single component because variation in Fe²⁺/Mg has little effect on the stability of phases on the diagram. Comparison of assemblages in the Franciscan, Shuksan, Sanbagawa, New Caledonia, Southern Italian, and Otago metamorphic terranes reveals several reactions, useful for construction of a petrogenetic grid:

1. lawsonite+crossite + paragonite = epidote+chlorite + albite + quartz + H₂O
2. lawsonite + crossite = pumpellyite + epidote + chlorite + albite+ quartz + H₂O
3. crossite + pumpellyite + quartz = epidote + actinolite + albite + chlorite + H₂O
4. crossite + epidote + quartz = actinolite + hematite + albite + chlorite + H₂O
5. calcite + epidote + chlorite + quartz = pumpellyite + actinolite + H₂O + CO₂
6. pumpellyite + chlorite + quartz = epidote + actinolite + H₂O

     

Tectonoelectric zonation in the Hellenic Arc

The electrical (apparent) resistivities ρ were measured by means of the magnetotelluric effect at twenty sites in Greece and in two directions, E-W and N-S. In most of the sites, ρ_EW differs considerably from ρ_NS. These results allow the following three zones to be distinguished:

• 1.(1) an external zone along western Greece with ρ_EW >ρ_NS;
• 2.(2) an intermediate zone along the main mountain chain in continental Greece where ρ_Ns >ρ_EW and
• 3.(3) an internal zone in the northern Aegean where ρ_EW >ρ_NS.

The above resistivity zones are compared to data from geotectonic, neotectonic, seismotectonic and in situ stress measurements which all show a similar geometry of zonation almost parallel to the active Hellenic Arc.     

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.