Organic Matter-rich Sediments Research Articles

An open ocean record of the Toarcian oceanic anoxic event

Abstract. Oceanic anoxic events were time intervals in the Mesozoic characterized by widespread distribution of marine organic matter-rich sediments (black shales) and significant perturbations in the global carbon cycle. These perturbations are globally recorded in sediments as carbon isotope excursions irrespective of lithology and depositional environment. During the early Toarcian, black shales were deposited on the epi- and pericontinental shelves of Pangaea, and these sedimentary rocks are associated with a pronounced (ca. 7 ‰) negative (organic) carbon isotope excursion (CIE) which is thought to be the result of a major perturbation in the global carbon cycle. For this reason, the lower Toarcian is thought to represent an oceanic anoxic event (the T-OAE). If the T-OAE was indeed a global event, an isotopic expression of this event should be found beyond the epi- and pericontinental Pangaean localities. To address this issue, the carbon isotope composition of organic matter (δ13Corg of lower Toarcian organic matter-rich cherts from Japan, deposited in the open Panthalassa Ocean, was analysed. The results show the presence of a major (>6 ‰) negative excursion in δ13Corg that, based on radiolarian biostratigraphy, is a correlative of the lower Toarcian negative CIE known from Pangaean epi- and pericontinental strata. A smaller negative excursion in δ13Corg (ca. 2 ‰) is recognized lower in the studied succession. This excursion may, within the current biostratigraphic resolution, represent the excursion recorded in European epicontinental successions close to the Pliensbachian/Toarcian boundary. These results from the open ocean realm suggest, in conjunction with other previously published datasets, that these Early Jurassic carbon cycle perturbations affected the active global reservoirs of the exchangeable carbon cycle (deep marine, shallow marine, atmospheric).

Petrography and carbonate isotope stratigraphy from MIS AND-1B core, Antarctica: Evidence of the early Pliocene warming event

A large portion of ANDRILL (ANtarctic geological DRILLing) core AND-1B recovered in the Western Ross Sea and spanning the early Pliocene has been investigated in order to obtain a detailed carbonate isotope record from Antarctic margin sediments through the early Pliocene warming event. Petrographic observations and mineralogical analyses reveal the authigenic nature of the carbonate and small proportions of Fe and Mg incorporated within the calcite lattice. High productivity conditions testified by ~ 80 m-thick diatomite interval (383 to 460 mbsf) well fit with the composite nature of the authigenic carbonate generally characterizing organic matter-rich sediments. As is known, sediments from the Polar Region are generally poor in carbonate. Although in the investigated portion of AND-1B core the carbonate seldom exceeds 5% in content, an automated Carbonate Preparation Device was used to obtain a high-resolution stable isotope dataset. Paleoenvironmental conditions characterized by high organic matter flux are supported by negative δ 13C values suggesting a contribution of isotopically light biogenic CO 2 during the carbonate precipitation. As to δ 18O, even if melting glaciers are thought to be responsible for depletion in 18O composition, the isotope record exhibits long- and short-term trends. Analysis of the long-term trend constrains the Pliocene warming climax in an interval between 400–450 mbsf highlighting that most of the event is not documented because of a 800 kyr hiatus. The short-term trend documents the influence of obliquity controlling the annual insolation, but also that of precession-linked cyclicity seldom documented at high latitude.

The potential of the Phytotoxkit microbiotest for hazard evaluation of sediments in eutrophic freshwater ecosystems

The applicability of the Phytotoxkit microbiotest for toxicity assessment of sediments in eutrophic freshwater ecosystems was evaluated. Sediments were collected from Turawa dam reservoir (southwestern Poland) which, for years, has been subjected to a marked nutrient enrichment and heavy metal contamination. The test plant species were exposed to whole sediments, solid phases of sediments, and pore waters. Phytotoxicity was estimated on the basis of seed germination and root elongation measurements, combined into an overall germination index (GI). For pore waters, the majority of GI values were not statistically different from the controls, which was consistent with chemical data. For solid phases and whole sediments, GI values showed diversified effects ranging from growth stimulation to growth inhibition. The results obtained vary depending on the plant species and the type of sediment samples. Generally, tests with solid phases of sediments showed phytostimulation, suggesting that higher amount of nutrients adsorbed on organic matter-rich sediments might conceal the inhibitory impact of heavy metals (Cd, Cr, Cu, Mn, Ni, Pb, and Zn). However, this beneficial impact is indicative of a significant nutrient load and, with respect to aquatic ecosystems, its potential resuspention that might accelerate the reservoir eutrophication. Under appropriate conditions heavy metals exerted stronger negative impact on plants. Tests with whole sediments had a higher acidity (pH5.85) and showed adverse effects, though plant responses vary from inhibition (Lepidium sativum) to stimulation (Sorghum saccharatum). The study demonstrated variability in toxicity of contaminated nutrient-rich sediments as well as effectiveness and usefulness of the Phytotoxkit microbiotest as a practical and reliable tool for evaluation of the hazard of eutrophic ecosystems to higher plants.

Shale gas in Europe: a regional overview and current research activities

Abstract Shale gas is produced from fine-grained siliciclastic sediments that are typically rich in organic carbon. Nearly all shales contain thermal gas generated in situ at mature to overmature levels of thermal alteration, although gas of biogenic origin is also produced from some shales. While shale gas production in the USA began in 1821, it is only in the last few years that it has become widely significant (currently about 8% of the domestic gas). In contrast, European shale gas exploration is still in its infancy. In general, European sedimentary basins offer the best potential for shale gas occurrence because thick, organic matter-rich sediments occur in nearly all Phanerozoic strata. Even so, there is little knowledge about the factors controlling shale gas generation and, more importantly, shale gas production in European basins. These factors are not necessarily the same as those that control commercial shale gas production in the USA. Palaeozoic sediments of Cambrian to Ordovician age are currently being tested for their shale gas potential and productivity in Sweden, as are those of Silurian age in Poland. Moreover, Lower and Upper Carboniferous sedimentary successions from England in the west to Poland in the east probably contain shale gas, but their depth, thickness and thermal maturity may be limiting factors for exploration in continental regions. Lower Carboniferous black shales in the Dniepr–Donets Basin of the Ukraine may also hold a significant potential. Moreover, organic-rich sediments of Oligocene/Miocene age in the Paratethyan Basin may offer shale gas potential, for example in the Pannonian Basin. At present, Upper Jurassic black shales are currently being tested for their shale gas potential in the Vienna Basin. European analogues of known biogenic shale gas systems may occur locally in organic-rich Lower Cretaceous sediments in the North German Basin with gas generation being related to Pleistocene glaciation/deglaciation cycles.

Identification and reliability of microbial aerobic respiration and denitrification kinetics using a single-well push–pull field test

Methods to derive reaction rates of microbial processes are important since these processes are determining many chemical reactions influencing groundwater quality. Thereby, it is not only important to derive the parameters, but also to have a firm idea about the reliability with which these are determined. Analysis of residuals, sensitivity analyses and analysis of joint confidence intervals provide an interesting tool for this purpose. The method is illustrated in this paper using a push–pull test designed to derive aerobic respiration and denitrification. Therefore, a test solution containing dissolved oxygen and nitrate as reactive tracer and bromide as non-reactive tracer was injected in organic matter rich sediment. Afterwards, this test solution was extracted and water quality was monitored. ReacTrans, a finite-difference, axial-symmetric groundwater flow and solute transport model was developed to simulate the test and derive hydraulic, solute transport and chemical parameters. Aerobic respiration and denitrification were simulated with Michaelis–Menten kinetics. Maximum reaction rates (10.4 and 2.4 mmol/ld for aerobic respiration and denitrification respectively) and Michaelis constants (0.14 and 0.1 mmol/l for aerobic respiration and denitrification respectively) were determined. The reliability with which these parameters are derived is indicated by analysis of residuals, sensitivities and joint confidence intervals. This shows that the Michaelis–Menten parameters can be derived reliable with a push–pull test, whereas the test is insensitive to effective porosity and hydraulic conductivity. Because of the small scale of the test, longitudinal dispersivity was very small and therefore unidentifiable.

A possible long-term CO 2 sink through submarine weathering of detrital silicates

The weathering of silicate minerals exposed on the continents is the largest sink of atmospheric CO2 on time scales of millions of years. The rate of this process is positively correlated with global mean temperature and atmospheric CO2 concentration, resulting in a negative feedback that stabilizes Earths’ climate (Berner, 2004). Detrital silicates derived from the physical denudation of the continents are a major component of marine sediments (Li and Schoonmaker, 2003). However, their geochemical behaviour is poorly understood and they are considered to be unimportant to the long-term carbon cycle. We show that in organic matter-rich sediments of the Sea of Okhotsk detrital silicates undergo intense weathering. This process is likely favoured by microbial activity, which lowers pore water pH and releases dissolved humic substances, and by the freshness of detrital silicates which originate from the cold, poorly weathered Amur River basin. Numerical simulations of early diagenesis show that submarine weathering rates in our study area are comparable to average continental weathering rates (Gaillardet et al., 1999). Furthermore, silicate weathering seems to be widespread in organic matter-rich sediments of continental margins, suggesting the existence of a significant CO2 sink there. These findings imply a greater efficiency of the silicate weathering engine also at low surface temperatures, resulting in a weakening of the negative feedback between pCO2, climate evolution and silicate weathering.

Composition and applied sedimentology of salt from brines of the Mamfe Basin, Cameroon

Salts produced using brines of the Mamfe Basin were analysed by XRD for their mineral composition and ICP-MS for minor element composition. Halite (NaCl) and dolomite (CaMg (CO 3) 2) constitute the major minerals with minor impurities from Mo and Cd in the chlorides and Sc and Cu in the carbonates. The mineral composition is evidence of dissolution of evaporites with parent brine of marine origin. Other elements analysed are suggested to be adsorbed to these salts and result from water–rock interaction. The elements partitioned based on their correlation to other elements are suggested to derive from sulphates including barite for Ba, sulphides for Pb, Zn, silicates for Zr, Mn and oxides for V, Cr. The electrical conductance of the brines is related to the salt yield by the equation; M = 9 × 10 − 4 E− 3.27, and it can be used to estimate salt yield throughout the year. Over 1200 tons of salt consisting dominantly of grade I halite are lost annually as brines across the basin. Purification is required for some minor elements including Ba, Pb, Hg and Cd for use as a condiment. A genetic relation between the parent brine, sulphide minerals and organic matter-rich sediments is proposed.

Mercury- and Silver-Rich Ferromanganese Oxides, Southern California Borderland: Deposit Model and Environmental Implications

Mercury- and silver-enriched ferromanganese oxide crusts were recovered at water depths of 1,750 to1,300 m from La Victoria knoll, located about 72 km off the coast of northern Baja California. No other ferromanganese precipitate found so far in the modern ocean basins is similarly enriched in Hg and Ag. The precipitates consist of submetallic gray, brecciated, Mn oxide layers overlain by brown earthy, laminated Fe-Mn oxide crusts. Both oxide types are rich in Hg (to 10 ppm) and Ag (to 5.5 ppm). The Mn-rich layers are composed of δMnO 2 , with lesser amounts of 10A and 7A manganates, whereas the Mn phase in the Fe-Mn crusts is solely δMnO 2 . The Fe phase in both layers is X-ray amorphous. Established criteria for distinguishing hydrothermal versus hydrogenetic crusts indicate that the Mn-rich layers are predominantly of low-temperature hydrothermal origin, whereas the Fe-Mn crusts are hydrogenetic, although there is some overlap in the source of chemical components in both types. La Victoria knoll is uplifted continental basement rock with basalt, andesite, and schist cropping out at the surface; the knoll may have an intrusive core. The Hg and Ag were derived from leaching by hydrothermal fluids of organic matter-rich sediments in basins adjacent to La Victoria knoll and, to a lesser extent, from continental basement rocks underlying the knoll and adjacent basins. Both rock types are notably enriched in Ag and Hg. Faults were the main fluid transport pathway, and hydrothermal circulation was driven by high heat flow associated with thinned crust. Other elements derived from the hydrothermal fluids include Tl, Cd, Cr, and Li. The main host for Hg and Ag is FeOOH, although MnO 2 likely hosts some of the Ag. Minor sulfide and barite also may contain small amounts of these metals. Possible analogs in the geologic record for this deposit type are found in the Basin and Range province of the western United States and Mexico. The discovery highlights the fact that fluids circulating along faults in the offshore California borderland are transporting potentially toxic metals (Hg, Ag, Tl, As, Cd, Cr, Pb, and Ni) and depositing them on and just below the ocean floor.

Stabilization of N‐Compounds in Soil and Organic Matter Rich Sediments: What Is the Difference?

AbstractFor Abstract see ChemInform Abstract in Full Text.

DEPÓSITO DE CAULIM DE TIJUCAS DO SUL (MINA FAZENDINHA, TIJUCAS DO SUL - PR)

The Tijucas do Sul sedimentary basin, about 45Km south of Curitiba (PR), is the largest deposit of kaolinitic clay from southern Brazil, containing estimated ore resources of 200 Mt. The basin developed on a gneissic and migmatitic basement and is being filled by sediments provided by the weathering and erosion of granites, volcano-sedimentary rocks and basalts. It contains quaternary agglomerates, sands, clays and clayish silts, deposited on fluvial flood plain and, subordinately, lacustrine environments. The intense lixiviation of superficial and shallow sediments by meteoric water acidified by organic matter rich sediments, is generating kaolinite and gibbsite, by feldspar desilicification, and gibbsite by kaolinite desilicification. The advanced aluminization of shallow and superficial sediments generated large quantity of gibbsite + kaolinite nodules. Chemical data suggests that this process occurred at least three other times, on periods when the paleo-surface of the sedimentary pile was exposed to weathering for long periods, which caused desilicification and kaolinization also of clay layers presentely buried. Black clays (AP facies) are the only with distinct chemical characteristics, outstanding by their high organic matter and Y contents and their ceramic properties, similar to ball clays. The < 0,04 mm granulometric fraction of sediments contains 45 to 75% kaolinite, 2 to 41% quartz, 1 to 8% gibbsite and 1 to 10% titanium oxides (ilmenite + anatase + “other oxides”). Ti and Fe are incorporated by clay minerals, due to their high grade of crystalline structural disorder, or occur as micro-fragments of minerals brought in from basalt dikes. Kaolinite crystallinity is low to very low and crystals with b axis disordered are the most frequent. These structural characteristics related to the low degree of diagenesis and to the desilicification of kaolinites. MEV-EDS analysis indicated the absence of halloysite and the predominance of detritic, < 0.5 mm, kaolinites over the “book-like” autigenic ones. Octahedrally shaped, high Ti micro crystals, probably anatase, occur mixed with clay minerals.

N2-fixing cyanobacteria supplied nutrient N for Cretaceous oceanic anoxic events

Research Article| October 01, 2004 N2-fixing cyanobacteria supplied nutrient N for Cretaceous oceanic anoxic events Marcel M.M. Kuypers; Marcel M.M. Kuypers 1Department of Marine Biogeochemistry and Toxicology, Royal Netherlands Institute for Sea Research, P.O. Box 59, 1790 AB Den Burg, Netherlands Search for other works by this author on: GSW Google Scholar Yvonne van Breugel; Yvonne van Breugel 1Department of Marine Biogeochemistry and Toxicology, Royal Netherlands Institute for Sea Research, P.O. Box 59, 1790 AB Den Burg, Netherlands Search for other works by this author on: GSW Google Scholar Stefan Schouten; Stefan Schouten 1Department of Marine Biogeochemistry and Toxicology, Royal Netherlands Institute for Sea Research, P.O. Box 59, 1790 AB Den Burg, Netherlands Search for other works by this author on: GSW Google Scholar Elisabetta Erba; Elisabetta Erba 2Department of Earth Sciences, University of Milan, “A. Desio,” via L. Mangiagalli 34, 20133 Milano, Italy Search for other works by this author on: GSW Google Scholar Jaap S. Sinninghe Damsté Jaap S. Sinninghe Damsté 3Department of Marine Biogeochemistry and Toxicology, Royal Netherlands Institute for Sea Research, P.O. Box 59, 1790 AB Den Burg, Netherlands Search for other works by this author on: GSW Google Scholar Author and Article Information Marcel M.M. Kuypers 1Department of Marine Biogeochemistry and Toxicology, Royal Netherlands Institute for Sea Research, P.O. Box 59, 1790 AB Den Burg, Netherlands Yvonne van Breugel 1Department of Marine Biogeochemistry and Toxicology, Royal Netherlands Institute for Sea Research, P.O. Box 59, 1790 AB Den Burg, Netherlands Stefan Schouten 1Department of Marine Biogeochemistry and Toxicology, Royal Netherlands Institute for Sea Research, P.O. Box 59, 1790 AB Den Burg, Netherlands Elisabetta Erba 2Department of Earth Sciences, University of Milan, “A. Desio,” via L. Mangiagalli 34, 20133 Milano, Italy Jaap S. Sinninghe Damsté 3Department of Marine Biogeochemistry and Toxicology, Royal Netherlands Institute for Sea Research, P.O. Box 59, 1790 AB Den Burg, Netherlands Publisher: Geological Society of America Received: 02 Jan 2004 Revision Received: 27 May 2004 Accepted: 31 May 2004 First Online: 02 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (2004) 32 (10): 853–856. https://doi.org/10.1130/G20458.1 Article history Received: 02 Jan 2004 Revision Received: 27 May 2004 Accepted: 31 May 2004 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Marcel M.M. Kuypers, Yvonne van Breugel, Stefan Schouten, Elisabetta Erba, Jaap S. Sinninghe Damsté; N2-fixing cyanobacteria supplied nutrient N for Cretaceous oceanic anoxic events. Geology 2004;; 32 (10): 853–856. doi: https://doi.org/10.1130/G20458.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract The abundance of specific membrane lipids, 2-methylhopanoids, indicates that cyanobacteria played a key role in the seemingly global deposition of black shales during the early Aptian (ca. 120.5 Ma) and late Cenomanian (ca. 93.5 Ma) oceanic anoxic events. Organic matter–rich sediments deposited during these events are characterized by a 15N content typical of newly fixed N2, indicating that cyanobacterial N2 fixation was the main source for nutrient N. We propose that denitrification and anaerobic ammonium oxidation effectively cut off the return of nutrient N from the anoxic deep waters to the photic zone in the oceans, giving N2-fixing cyanobacteria a competitive advantage over algae during these oceanic anoxic events. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Organic matter preservation and sulfur uptake in sediments from the continental margin off Pakistan

The bulk and molecular geochemical characteristics of a suite of kerogens isolated from organic matter-rich sediments from the Pakistan margin has been characterised by elemental analysis, Rock-Eval pyrolysis and pyrolysis-gas chromatography (Py-GC). Special attention was given to the geochemistry of alkylthiophenes which are thought to reflect the incorporation of sulfur into organic matter (OM) in the context of early diagenetic sulfate reduction. Organically bound sulfur comprises up to 60% of total sedimentary sulfur. The weight ratios for organic sulfur (S org) over organic carbon (C org) varies from 0.01 in some of the recently deposited sediments to 0.11 in older samples. The results show that sulfur incorporation into organic matter occurs primarily within the upper few meters of the sediments. The amount of sulfur which can be incorporated into the organic matter clearly depends on the quality of OM. The hydrogen index values [HI; which characterise the total amount of generated hydrocarbon equivalents of the pyrolysate (in mg HC equiv./g C org)] are related to the extent of reworking of organic matter either in the water column or at the sediment-water interface or to remineralization processes by sulfate reduction itself which is strongly controlled by the availability of reactive iron. High quality organic matter characterised by elevated HI values is capable of sequestering higher amounts of sulfur [as expressed by the thiophene content, which represent the organically bound sulfur of the pyrolysate (in mg/g C org)]. As indicated by the ratio of thiophenes versus HI, which characterises the proportion of thiophenes in the total pyrolysate, sulfurisation of organic matter seems to be terminated at a ratio of 0.01.

Origin of the Kupferschiefer polymetallic mineralization in Poland

The Kupferschiefer ore series, between the Lower Permian (Rotliegendes) terrestrial redbeds/volcanics and the Upper Permian (Zechstein) marine sequence, is developed as dark-grey organic matter-rich and metal sulphide-containing deposits (reduced zone) and as red-stained organic matter-depleted and iron oxide-bearing sediments (oxidized zone = Rote Faule). The transition zone from oxidized to reduced rocks occurs both vertically and horizontally. This zone is characterized by sparsely disseminated remnant copper sulphides within hematite-bearing sediments, replacements of copper sulphides by iron oxides and covellite, and oxide pseudomorphs after framboidal pyrite. These textural features and copper sulphide replacements after pyrite in reduced sediments imply that the main oxide/sulphide mineralization postdated formation of an early-diagenetic pyrite. Hematite-dominated sediments locally contain enrichments of gold and PGE. The Kupferschiefer mineralization resulted from upward and laterally flowing fluids which oxidized originally pyritiferous organic matter-rich sediments to form hematitic Rote Faule areas, and which emplaced base and noble metals into reduced sediments. It is argued that long-lived and large-scale lateral fluid flow caused the cross-cutting relationships, expansion of the hematitic alteration front, redistribution of noble metals at the outer parts of oxidized areas, and the location of copper orebodies directly above and around oxidized and gold-bearing areas. The Rote Faule may be a guide to favourable areas for both the Cu-Ag and new Au-Pt-Pd Kupferschiefer-type deposits.

Redox stratification and heavy metal partitioning in Avicennia-dominated mangrove sediments: a geochemical model

Mangrove forest sediments can provide a sink for trace metals because the mangroves create a baffle that promotes the accumulation of fine-grained organic matter-rich sediment, which is usually sulphidic due to the presence of sulphate-reducing bacteria. Direct adsorption, complexing with organic matter, and the formation of insoluble sulphides all contribute to the trapping of metals. The concentration and chemical speciation of the metals are influenced by the distribution of geochemically distinct horizons within the sediment. In horizons with a pH>7 and an Eh<−150 mV (reduction horizons), metals are largely present as sulphide-bound species, whereas in horizons with a pH<7 and an Eh>+100 mV (oxidation horizons), most metals are present as exchangeable or oxide-bound species. In most cores, two oxidation and two reduction horizons can be recognised, but dark mottles of low Eh (<−150 mV) sediment can be found in the oxidation horizons, and orange–brown halos of high Eh (>+100 mV) sediment can be found around mangrove roots and burrows in the reduction horizons. The depth to each horizon, differs between cores and can change in response to seasonal shifts in the position of the water table. A model is presented that accounts for the development of the oxidation and reduction horizons within the Avicennia-dominated mangrove forest sediment and describes the major controls on metal cycling within the sediment.

First occurrence and stable isotope composition of authigenic γ-MnS in the central Gotland Deep (Baltic Sea)

The occurrence of authigenic γ-MnS in organic matter-rich sediments of the central Gotland Deep is reported for the first time. The hexagonal manganese sulfide was found in a thin sediment layer with an approximate age of 1130 years and has an isotopic composition of δ 34S ≈ − 13%. vs. V-CDT. This indicates that the bonded sulfur is derived from the anaerobic microbial reduction of pore water sulfate. SEM analysis reveals that γ-MnS occurs as idiomorphic crystals of about 200 μm length and 150 μm width, much larger than the diameters of co-existing calcian rhodochrosite globules (~6 μm). It is suggested that formation of γ-MnS took place in a diagenetic environment which was locally free from reactive iron.

Regulation of microbial phenanthrene mineralization in sediment samples by sorbent-sorbate contact time, inocula and gamma irradiation-induced sterilization artifacts

Time-dependent diffusion and/or sorption reactions were proposed as a mechanism for protecting polycyclic aromatic hydrocarbons (PAHs) in surface and subsurface sediments from a coal tar waste-contaminated field site. 14 C-labeled phenanthrene was aged in both subsurface sand and organic matter-rich seep sediments that had previously been sterilized by gamma irradiation. After aging periods ranging from 0 to 28 d, the sediments were dispensed to replicate vials and inoculated with site-derived phenanthrene-degrading microorganisms (with and without previous enrichment on phenanthrene), and cumulative 14 CO 2 production was measured. When pure culture and mixed inocula originated from the seep sediments, phenanthrene mineralization from sand sediment samples was retarded with longer aging periods. However, when a mixed inoculum originating from the sand sediments was tested, aging of the phenanthrene had only a slight or no effect on its rate or extent of mineralization. Thus, the susceptibility of phenanthrene to biodegradation varied with the source of the microbial inocula. When gamma-irradiated seep sediments were the sorbent, all mineralization of 14 C phenanthrene was eliminated. Several hypotheses were tested for explaining this sorbent-dependent inhibition of phenanthrene metabolism. Gamma radiation-induced changes in the sorptive properties of the seep sediment seemed to be the cause.

A Sensitive Method Using 4-Methylumbelliferyl-β-Cellobiose as a Substrate To Measure (1,4)-β-Glucanase Activity in Sediments

A sensitive method to measure (1,4)-beta-glucanase activity in organic matter-rich sediments, using 4-methyl-umbelliferyl-beta-cellobiose as a substrate, is described. beta-Glucosidases, which were also able to hydrolyze this substrate, were inhibited with d-glucono-delta-lactone. The produced 4-methylumbelliferone was recovered quantitatively out of the sediment by an extraction with 80% ethanol. An inhibition experiment with known substrates or inhibitors suggested that at least 59% of the measured activity could be explained by enzymes of the exo-(1,4)-beta-glucanase type and that the contribution of endo-(1,4)-beta-glucanases was minor. Results of the inhibition experiment also suggested that the measured activity was of bacterial origin in the sediment used. First results of field measurements are given for the sediment from the reed bed of Lake Gooimeer.

Organic matter accumulation in the bottom sediments and its regulatory aspects in the southern basin of Lake Biwa

Approximately 14 million people get their drinking and industrial water from the most southern part of Lake Biwa. This shallow region, however, has been eutrophicated severely from year to year by nutrients loading from both the surrounding inflowing rivers and the north basin. Sedimented solids of the surface layer of bottom sediments are stirred up very frequently by strong winds and waves in this shallow region. Moreover, the water quality has been deteriorated by the release of nutrients from the surface layer of bottom sediments in which organic matter has accumulated. For the period 1989 to 1990, the suspended solids content had a close correlation with the COD value, and the T-N and T-P concentrations in the water of inflowing rivers to the basin. T-N release rate from the surface layer of bottom sediments ranged from 6.3 to 213.8 mg m-2 d-1 and the release load was 936 kg d-1 for the entire 58 km2 of the south basin. On the other hand, T-P release rate ranted from 0.91 to 3.56 mg m-2 d-1 and the total release load was approximately 69 kg d-1 in the basin. Suction dredging of organic matter rich sediments was carried out in the basin to improve the water quality. Removed sediments were used after processing for various kinds of construction materials, such as bricks for pavement, walls of domestic houses, and ornamental materials of public buildings.

Tectonic Evolution of Western Patagonia and Hydrocarbon Habitats

In Devonian times, Western Patagonia was a Pericratonic Foreland basin. The rift-like, faulted platform underwent several marine transgressions-regressions related to tectonic episodes occurring mainly from Hercynian to Andean (Pyrenaic) times that modified the extension and nature of sedimentation in the region, due to the evolution of the Pacific Plate and Margin, and the accretion of successive acidic magmatic arcs. The marine sequences that flooded Patagonia, uneven in extension, shifted from North to South in accordance with differential subsidence in this margin, particularly in the three main sedimentary embayments: Neuquen, San Jorge and Magellan-Malvinas. Transversal ridges, following ancestral transtensional features, rejuvenated during the Atlantic opening separate these embayments. Marine sequences evolved into restricted circulation oxygen poor seas, whose organic matter rich sediments originated hydrocarbon source rocks, identified in the three most important basinal complexes of Patagonia. The beginning of the Andean Orogeny and the emplacement of the Andean Batholith, hindered the Pacific marine presence in western Patagonian basins. Subsequently, an Eastern elongated region-wide subsidence allowed the accumulation of molasse-like sequences over most foredeep sediments in the region, creating several hydrocarbons habitats grouped as follows: Neuquen: Proven: Liassic-Aptian; Potential: Triassic; San Jorge: Proven: U. Jurassic-L. Cretaceous; Unproven: L. Paleozoic-L. Jurassic; Magellan/Malvinas: Proven:more » L. Cretaceous; Unproven: Jurassic-U. Cretaceous During Laramic time, Atlantic highstand sea levels flooded a great part of Extra Andean Patagonia, while the Andean Chain started rising with an active magmatic arc.« less

Sequence Stratigraphy of Cambrian Economic Phosphorites and Organic Matter-Rich Shales, Georgina Basin, Australia

Sequence stratigraphic relationships in clastic- and carbonate-dominated sedimentary systems are comparatively well known. In these systems maximum flooding surfaces are often characterized by organic matter-rich sediments, glauconite, and phosphatic hardgrounds. This model explains the repeated occurrence of minor amounts of phosphate in the sedimentary record. However, it does not account for the large reserves of sedimentary phosphorite found in phosphate deposits of Cambrian, Ordovician, Permian, Cretaceous, and Miocene age. In Australia, economic phosphorites and their associated organic matter-rich shales, of Middle Cambrian age, accumulated in an intracratonic setting in the Georgina basin. The economic phosphorites occur in the lowermost two stratigraphic sequences of the basin and coincide with a period of major inundation of the continent. In each sequence the phosphorites are restricted to the upper parts of retrogradational parasequence sets of the transgressive system tract. In deeper water, drowned-platform and -ramp settings, micritic limestones, phosphatic hardgrounds, and organic matter-rich shales with benthonic and planktonic faunal components accumulated in dysaerobic environments. Further down the depositional slope and in subsequent parasequences, laminated organic matter-rich shales with TOC contents up to 16%, lacking benthonic but hosting planktonic faunal elements, accumulated in anaerobic conditions. Thus, economically significant phosphate deposits in the Georgina basinmore » are the shallow-water, laterally equivalent facies of the weakly phosphatic and glauconitic dolomitic limestones and organic matter-rich shales, characteristic of the deeper water-condensed section.« less