Distribution Of Particulate Organic Matter Research Articles

The riphean sedimentary basins of the Eastern Siberia province and their petroleum potential

From their location in the regional pattern of the Eastern Siberia Province, their style and their evolutionary history, the Riphean sedimentary basins are divided into two groups: “marginal cratonic” and “intracratonic”. The first group includes basins of “pericratonic troughs”, “fore-deeps” and “marginal transverse aulacogens”. They are characterized by a definite division into structural stages according to both characteristics of the individual formations and interbedding of rocks with different lithology. Within sequences, there is a complex combination of formations such as black-shale, and flyschlike, volcanoclastic-terrigenous, carbonate and others. The second group incorporates “aulacogenic” and platform intracratonic sedimentary basins. The main features of aulacogen-type sedimentary basin structure are due to their rift origin and style of subsequent development. The early stages are marked by an alternation of volcanoclastic-terrigenous and volcanoclastic-carbonate rocks. There is rythmic interbedding of terrigenous and terrigenous-carbonate rocks up-section. Depositional environments in sedimentary basins of platform depression have been controlled to a large extent by the structural-dynamic setting of the final stages in the formation of adjacent pericratonic troughs and intracratonic aulacogens. The succession consists mainly of terrigenous-carbonate and carbonate-terrigenous units, i.e., products of erosion and re-deposition of Early Riphean complexes and ancient basement. Distribution of particulate organic matter and its catagenetic transformation indicate rather high petroleum-generating potential for the Riphean. Regional development of high-quality seals (upper Vendian argillaceous evaporite-carbonate units and Lower Cambrian salts) greatly favors preservation of hydrocarbon accumulation. Three groups of hydrocarbon reservoirs are differentiated based on structural-tectonic, lithologic-formational and geochemical features. Hydrocarbon fields of considerable commercial importance have been discovered for the first time in world exploration practice in the Riphean of the East Siberian Province. These should lead to the re-evaluation of the hydrocarbon potential of late Proterozoic basins on other continents.

Spatial Heterogeneity of Nutrients and Organic Matter in Lake Ontario

During spring, Lake Ontario was vertically homogeneous except for the bottom 2 m where soluble reactive silica (SRS) and temperature (TEMP) were significantly (p < 0.05) elevated and dissolved oxygen was depleted. With stratification, soluble reactive phosphorus (SRP) and total filtered phosphorus, SRS, and nitrate-plus-nitrite were depleted in the epilimnion due to phytoplankton uptake. Total unfiltered phosphorus (TP) and ammonia (NH3) exhibited higher epilimnetic concentrations, the former being attributed to tributary inputs which were maintained throughout the stratified period, even though inputs from Niagara River served to dilute the epilimnion. Increased levels of TP, SRP, and SRS were also evident within the nepheloid layer. Horizontal distributions of TP and NH3 were governed by point-source inputs throughout the study period. Distributions of the soluble nutrients were governed by phytoplankton uptake in the spring, point/nonpoint inputs and upwelling in the summer, and differential breakdown of stratification in the fall. Spring distribution of particulate organic matter (POM) was strongly related to nutrient availability and water column stability, while phytoplankton species composition determined fall POM distribution. Significantly higher (p < 0.05) POM levels, detrital content, and productivity were observed nearshore of the thermal bar.

Vertical Succession of Attached Bacteria and Its Relationship to the Distribution of Organic Matter in Seawater

Vertical change of the heterotrophic bacterial community attached to particulate organic matter (POM) was studied in relation to the distribution of POM in the neritic sea of Japan. The analysis of bacterial community was performed by dividing the isolates into five groups: Vibrio (V), Pseudomonas-Alcaligenes (Ps), Acinetobacter-Moraxella (Ac), Chromogenic (C) and Gram-positive (Po) groups. The community structure of attached bacteria was quite different from that of free-living in the ambient seawater. In the water column, the community of attached bacteria showed the distinct vertical succession, which was: Ps→V→(Ps+Ac)→(Ac+C)→Ps. The attached bacteria in the layers where the decomposition of POM proceeded actively had high substrate-decomposing activity, whereas in the deeper layers with limited supply of the “fresh” POM the activity was low. These results suggest that the community of attached bacteria showed the vertical succession with the proceeding of POM decomposition from the community with a high biochemical activity to a low activity, as associated with the change of genera.

Underwater transmittance as a tool in the study of spatial distribution of particulate organic matter

Underwater transmittance as a tool in the study of spatial distribution of particulate organic matter

The depth significance of shales with bituminous laminae

The shales under discussion contain regularly-spaced thin bituminous laminae alternating with mineral layers, which probably represent varves. The distribution of particulate organic matter in the sea is briefly reviewed. Phytoplankton productivity is highest in regions of upwelling and in continental shelf waters, where in addition there is generally a significant proportion of detritus from terrestrial plants and benthonic algae. Only a small fraction of this organic matter reaches the sea floor and of this very little is ultimately preserved in marine sediments, principally as kerogen. The proportions of terrestrial and marine components of the organic matter in sediments can be determined in several ways. The organic content tends to be highest in fine-grained sediments laid down in poorly-oxygenated or anaerobic waters, characteristically in the deeper parts of nearshore basins partly isolated from normal oceanic circulation by sills. Certain sediments laid down in very shallow lagoons may also be rich in organics. No simple relationship of organic content and depth of sea is discernible. In interpreting bituminous shales in the stratigraphic record, comparisons with the present may be somewhat misleading. For long periods in the past the world climate was apparently more equable than today and shallow shelf seas more extensive. It is argued, taking examples from the Jurassic of Europe and the Devonian of North America, that the familiar “barred basin” model may be inapplicable to many bituminous shales in the past, which were relatively shallow-water deposits laid down in quiet but not invariably stagnant water below wave base. Certain geosynclinal graptolitic shales may have been laid down in deep water, though perhaps shallower than the associated greywackes.