Organic Ooze Research Articles

Sedimentological and palaeohydrological characterization of Late Pleistocene and Holocene tufa mound palaeolakes using trenching methods in the Spanish Pyrenees

AbstractLakes developed in the inner depressions of tufa mounds are rare geomorphic features and still poorly understood. Sedimentation in this unusual type of endorheic lake with a very restricted catchment area is highly sensitive to environmental and hydrological changes. The Isona tufa mound complex, north‐eastern Iberian Peninsula, is associated with the discharge zone of a confined artesian aquifer and comprises 11 tufa mounds consisting of an annular rimstone enclosing a central depression filled with lake deposits. Data gathered from trenches excavated in four palaeolakes located within three different morphostratigraphic units permitted a precise analysis of the geometrical characteristics and stratigraphic relationships of the deposits and provided a sedimentation model for the Late Quaternary infilling of the spring‐fed lakes. The work illustrates that trenches allow a precise characterization of the stratigraphic arrangements, lateral facies changes and deformation structures, which are not apparent in studies relying solely on borehole records, and facilitate sampling for dating and geochemical analyses. The five sedimentary facies described represent different evolutionary stages of the lakes, including: (i) carbonate‐rich palustrine deposits probably related to periods with strong hydrological seasonality; (ii) massive highly bioturbated organic ooze; (iii) banded organic carbonate‐rich facies associated with an increase in the regional effective moisture; (iv) fine‐grained quartz‐rich aeolian/slope‐wash sediments; and (v) colluvial facies deposited following the desiccation of the lakes located at higher altitudes. Geochemical and sedimentological analyses of the lacustrine sequences provided information on the palaeohydrological evolution of the Isona tufa mound complex and the palaeoenvironmental conditions of the area over the last 28 ka. Radiometric dating suggests that deposition occurred simultaneously at ca 22 ka in palaeolakes situated at different elevations. A drop in the piezometric level prompted by the opening of springs at lower altitudes probably caused the deactivation of the upper springs and the desiccation of the lakes. Arid conditions prevailed in the area during the Late Glacial and the early Holocene (28·0 to 8·5 ka bp). More humid conditions recorded from 8·5 to 4·2 ka and again since 1·7 ka are in accordance with palaeoenvironmental reconstructions available in the Western Mediterranean since the Last Glacial Maximum.

莱州湾中国对虾生长特性及其空间分布

PDF HTML阅读 XML下载 导出引用 引用提醒 莱州湾中国对虾生长特性及其空间分布 DOI: 10.5846/stxb201404290854 作者: 作者单位: 山东省海洋资源与环境研究院,山东省海洋资源与环境研究院,山东省海洋资源与环境研究院 作者简介: 通讯作者: 中图分类号: 基金项目: 山东省渔业资源增殖效果评价(SD2012-2014); 莱州湾中国对虾资源增殖管理优化控制模拟研究(ZR2013DQ016); 水生动物营养与饲料'泰山学者'岗位 (TS200651036)经费 The growth characteristics and spatial distribution of Fenneropenaeus chinensis in Laizhou Bay Author: Affiliation: Shandong Marine and Fishery Research Institute,Shandong Marine and Fishery Research Institute,Shandong Marine and Fishery Research Institute Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:根据2010年5月-10月调查资料,对山东莱州湾中国对虾(Fenneropenaeus chinensis)的资源状况、生长特性及其空间分布进行了研究。莱州湾放流前本底调查资料表明,目前山东莱州湾中国对虾捕捞产量主要来源于增殖放流,且在一定条件下捕捞产量与放流数量成正相关关系。依据2010年中国对虾生物学数据,应用R语言命令对中国对虾体长体重关系和体长生长方程进行了拟合,并对拟合系数进行了显著性检验,结果表明中国对虾体长与体重系数a、b处于显著水平(P < 0.05),中国对虾体长生长方程拟合系数K、t0、L∞处于极显著水平(P < 0.001),故拟合效果明显,获得为中国对虾生长参数雌虾为K=0.0226、t0=37.45d、L∞=200.77 mm、W∞=80.50 g、tr=85.18d(8月4日),雄虾为:K=0.0419、t0=40.25d、L∞=145.81 mm、W∞=23.37 g、tr=67.24d(7月18日),与20世纪80年代相比,中国对虾个体明显减小,生长速度加快,生长拐点提前了1个月。另外,根据大面调查体长数据,对各个站位体长组出现频率进行Ward聚类分析,利用R语言聚类树的融合水平值定义划分水平,选择具有最大跳跃的分组水平,将中国对虾虾群大致可分为两个组群,河口组和深水组,同时按照各体长组的多度值大小,探讨了各组内具有代表性的分类体长组,结果表明,河口组的中国对虾以体长125-135 mm为主,深水组以体长115-125 mm和105-115 mm为主,河口组个体明显大于深水组;河口组分布区入海河流较多,饵料生物丰富,以软泥底质为主,有利于中国对虾的摄食和前期保护,深水组分布于莱州湾中东部,蟹类资源相对较高,且以沙质底质为主,对中国对虾的生长与保护产生一定的影响。 Abstract:We conducted bottom surveys in Laizhou Bay between May and October 2010 and determined the catch rates, growth characteristics, and spatial patterns of Fenneropenaeus chinensis. We found that the catch rates of F. chinensis had mainly improved because of stock enhancement, and these rates were occasionally positively correlated with the number of individuals released. The data obtained were used to generate length-weight relationship curves and body-length growth curves; these curves were fitted using R (version 3.0.2), and the significance of the fitted factors was tested. The factors a and b of the equation used to calculate the length-weight relationships were significant at P < 0.05), and the factors K, t0, and L∞ of the von Bertalanffy growth equation were significant at P < 0.001). The growth parameters of F. chinensis caught on August 4 and July 18, 2010, were as follows:♀:K= 0.0226, t0 = 37.45 d, L∞= 200.77 mm, W∞ = 80.50 g, and tr = 85.18 d; ♂:K = 0.0419, t0 = 40.25 d, L∞ = 145.81 mm, W∞ = 23.37g, and tr = 67.24 d, respectively. These findings suggest that, compared with the individuals caught in the 1980s, those in the present study were remarkably smaller, showed accelerated growth, and the turning point for the growth curve had advanced by about a month. In addition, the data for body length collected during a large-scale survey at 32 stations were analyzed using hierarchical clustering. Analysis of the results of clustering using R language with the highest likelihood suggest the existence of two assemblages of F. chinensis in the surveyed waters:the estuarine group and the deep-water group. The F. chinensis communities were analyzed according to their body length. The abundance value of representative method showed that the estuarine group mainly consisted of individuals having a length of 125-135 mm, whereas the deep-water group included individuals having lengths of 115-125 mm and 105-115 mm. This suggests that individuals of the estuarine group were bigger than those of the deep-water group. The estuarine group was mainly found in rivers that have abundant food sources, and the bottom material was mainly composed of organic ooze, which provided protection to F. chinensis. In contrast, the deep-water group was located in the middle-east region of Laizhou Bay, which has rich crab resources, and the bottom material was mainly composed of sand. These factors influenced the growth and protection of F. Chinensis in deep waters. 参考文献 相似文献 引证文献

Taxonomy and Distribution of Isoetes valida

constitutes an earlier valid name for I. caroliniana. This emergent aquatic, diploid quillwort is known from nine states along the Appalachian Mountains and Pied- mont, growing in cold streams, mountain woodland ponds and in the saturated organic ooze of springs from central Pennsylvania to northeastern Alabama. It exhibits a distribution similar to several other endemic Appalachian pteridophytes. Disjunct populations are also known from the Coastal Plain of southeastern Alabama and Delaware. Although similar in appearance to I. engel- mannii, I. is typically distinguished by its raggedly reticulate megaspore ornamentation, its velum covering 50% or more of the unmarked sporangium wall, and spinulose microspores. George Engelmann (1867) described engelmannii A. Braun var. val- ida Engelm. (Isoetaceae) from a series of specimens collected between 1862 and 1867 by William Canby and Thomas Porter in Pennsylvania and adjacent Delaware. All material collected up until the publication date was labelled by Engelmann and others as Isoetes valida or Isoetes Engelm., ined., indicating that he initially considered this to be an undescribed species. In his treatment for the fifth edition of Gray's Manual of Botany (Engelmann, 1867), however, he revised that opinion in favor of a varietal designation. Al- though included in some subsequent nineteenth century treatments of I. en- gelmannii (e.g., Engelmann, 1882), var. was largely overlooked or con- sidered taxonomically insignificant by later taxonomists. Clute (1905), how- ever, almost casually raised it to species level in the belief that it and I. xea- tonii R. Dodge were synonymous. This interpretation was rejected by all subsequent investigators and I. (Engelm.) Clute was not even mentioned as a synonym of I. engelmannii in the review papers of Pfeiffer (1922) and Reed (1965). When Alvah A. Eaton described I. engelmannii var. caroliniana A.A. Eaton from material collected in the southern Appalachian mountains, he made no mention of Engelmann's earlier varietal segregates of I. engelmannii (Eaton, 1900). Eaton hinted that I. engelmannii var. caroliniana might well be a dis- tinct species, but he published no more on the subject. Pfeiffer (1922), Reed (1965), and Boom (1982) followed Eaton's conservative position in considering this a southeastern endemic variety of I. engelmannii. Individual author's in- terpretations of range and morphology varied widely, however, resulting in many specimens of several taxa being labelled with this name. Eaton's original suspicions that I. caroliniana warranted species status have been supported by recent investigations involving Scanning Electron Micros- copy (SEM) and allozyme electrophoresis (Duff and Evans, 1992; Luebke,

Microbialitic Structures in Storr's Lake, San Salvador Island, Bahama Islands

The water level in two-meter-deep Storr's Lake, San Salvador Island, fluctuates annually in response to rainfall, groundwater recharge, and evaporation. Although sea water flows in through conduits at high tide and lake waterflows out at low tide, daily lake-level fluctuations have not been observed. Lake water salinity of as little as 38,500 ppm to as great as 93,500 ppm has been measured; water in the lake is density-stratified. Several different microbialitic structures exist in Storr's Lake in well-established zones that apparently are controlled, in large part, by water depth. Thrombolitic microbialites around the lake margin are exposed annually above temporary water levels for intervals of many weeks or months. Crumbly stromatolitic microbialites up to 15 cm tall form an adjacent zone lakeward from the thrombolites; they may be partially emergent above water for extended periods. Next lakeward is a zone of flat-topped, irregular, hard stromatolitic microbialites developed on hard substrates of varying depth but whose tops are impressive in their uniform depth; these structures apparently are never emergent. In deepest water throughout much, but not all, of the central portion of Storr's Lake are columnal stromatolitic structures ranging from 10 to at least 70 cm in height whose tops are consistently 40-50 cm beneath the inferred minimum lake level. Between these columnal structures and ubiquitous throughout the lake beneath water depths of 20-30 cm is an organic ooze as much as 1 m thick that is covered by a soft but coherent alga layer. INTRODUCTION

Sedimentation and erosion in a Chesapeake Bay brackish marsh system

Characteristics of sediment transport and deposition were studied in a Maryland brackish marsh system which has experienced extensive erosion (2300 ha) over the last four decades. Ebb-tide domination of the marsh system contributes to a net output of 720,000 MT of sediment per year (13.8 kg m −2 yr −1). This export allows very little inorganic sediment to reach the interior marsh despite the sporadic high concentrations of total suspended solids in the tidal channels (10–1400 mg l −1). Vertical accretion in these marshes is primarily by peat deposition instead of the accumulation of mineral sediment. 210Pb dating suggests that accretion rates ranging from 1.7 to 3.6 mm yr −1 in the area of active marsh loss probably have not kept pace with sea-level rise since 1940 (3.9 mm yr −1). The reliance on organic sedimentation in the past has resulted in the development of a thin (0.1–0.5 m) consolidated marsh mat over 1–4 m of unconsolidated organic ooze. Erosion typically follows a sequence of incipient deterioration of the mat, possibly associated with heavy grazing activity by muskrats, and subsequent development of interior ponds. Once formed, the ponds slowly enlarge by undifferentiated rotational slumping. When they reach about a hectare in size they rapidly elongate in a NW-SE direction by wind-generated wave undercutting of the mat during major NW-tracking storms. Several hypotheses are presented to explain fundamental reasons why this marsh type is not accreting rapidly enough to keep abreast of apparent sea-level rise.

Experimental Study of Trace Metal Chemistry in Soft-Water Lakes at Different pH Levels

The biogeochemistry of Hg, Zn, Co, Fe, Mn, Cr, V, Th, Ba, Cs, As, and Se in two soft-water lakes of the Canadian Shield was investigated by means of carrier-free γ-emitting isotopes introduced into limnocorrals in which the pH of the water was varied from 6.8 to 5.1. The residence times of the radionuclides in the water were determined, and the partitioning of the nuclides among different metal-binding agents in the water and sediments was studied with the aid of membrane filtration, dialysis, solvent extractions, and fractionation on Sephadex columns.Metal behaviour varied systematically with metal properties. Metals of high crystal field stabilization energy, high electronegativity, or small ionic radius were most readily scavenged by&gt; 0.45 μm suspended particles and dispersed colloids in the water, disappeared most rapidly from the water column, and were preferentially accumulated by sedimentary binding agents, including organic substances. Which property of a metal had the dominant effect on metal behavior depended on environmental factors, such as the ambient pH and the nature of the binding agents. Thus, Hg was removed fairly rapidly from the water at pH 6.7–6.8 owing to its high electronegativity but was removed more slowly than any other metal at pH 5.1 owing to its large ionic radius.Most metals were strongly chemisorbed or complexed by mud and organic ooze, and only Ba could be redissolved by cation exchange. Therefore, 0.1 N NaOH and 0.1 N or 1 N HCl were more efficient extractants than H2O, 1 N CaCl2, or benzene/methanol, and the metals were largely nonextractable by any of these solvents. The major NaOH-extractable metal-binding agents were the higher molecular weight fractions of a group of organic (probably humic) substances characterized by a UV absorption band at [Formula: see text]. The affinity of metals for the highest molecular weight "humic" (NaOH-extractable) substances increased with electronegativity, being greatest for Hg. Hg and Se were nonextractable by HCl but were the elements most readily extracted by NaOH, implying exceptionally strong covalent bonding by humic matter. The more electropositive metals were more readily extracted by HCl than by NaOH, suggesting weaker, less highly covalent bonding or preferential sorption by acid-soluble hydrated oxides.Acidification of lake water to pH 5.1 interfered with accumulation of Hg and other metals by organic ooze, probably owing in part to interference with the deposition or formation of the complexing agents with the 265 nm absorption band. Acidification also lowered the concentration of NaOH-extractable colloidal phosphate in the ooze but had no effect on NaOH-extractable orthophosphate content.Key words: metals, lakes, chemistry, pH, humic matter, organic matter, phosphorus, radioactive tracers, acidification

Distribution of autotrophic nitrifying bacteria in a polluted river (the Passaic).

The abundance of nitrifying bacteria, determined by most-probable-number procedures, within habitats of the Passaic River was as follows: rooted aquatic plants greater than algae approximately equal to rocks greater than sediments greater than greater than water. On the average, NH4+ oxidizers were 540-fold more abundant in the topmost 1 cm of sediment than in the water, and NO2- oxidizers were 250-fold more abundant. The population densities in this surface sediment at two nearby stations, one with a predominantly mineral stream bed and the other an organic ooze, did not differ significantly. Large numbers of nitrifiers were present to a depth of about 5 cm in a mineral sediment core.

The Effects of Thermal Pollution on the Egg Survival of Lake Whitefish (Coregonus Clupeaformis [Mitchill

Abstract Lake Wabamun, located approximately 64 km west of Edmonton, Alberta, has two thermal electric generating stations situated upon it which utilize lake water for cooling purposes. The fishery for lake whitefish (Coregonus clupeaformis [Mitchill]) in the lake is important due to its high commercial and sport value. Since lake whitefish eggs require low temperatures throughout the winter for successful incubation, and since the major spawning area in the lake is located across a small bay from one of the power plants, it was feared that the heated water discharge would reduce lake whitefish egg survival on the spawning grounds. Since the whitefish are subject to heavy fishing pressure in the lake, it was thought that such a reduction in egg survival might cause a gradual reduction in the whitefish population. During preliminary fishery investigation in the lake it was discovered that large numbers of lake whitefish were spawning on an organic ooze substrate in the heated area. To determine the survival of eggs spawned on the ooze substrate in one of the heated areas , and also on the major spawning grounds (a rock and sand shoal), fertilized lake whitefish eggs were incubated in situ in enclosed trays in these areas and at control sites located in the portion of the lake not influenced by the power plants. The effects of substrate type, water temperature, and siltation on egg survival and their relation to the heated water discharge areas are discussed.

Surface Sediments in Lake Tahoe, California-Nevada

ABSTRACT Core and grab samples from 40 sites in Lake Tahoe and from six major tributaries were analyzed for mineral and biogenic components and for texture. Clay and silt fractions were analyzed by X-ray diffraction. Sand and gravel were stained to differentiate feldspars, and mineral composition was visually estimated. In addition. the relative abundance of diatoms and pollen was estimated. The areal distribution of volcanic constituents of sand and gravel fractions reflects volcanic sources in the north and northwest parts of the basin. Volcanic areas contribute montmorillonite to clay fractions whereas vermiculite and chloritic intergrades are characteristic weathering products of granitic sources. Two distinct types of sediment are present. Pollen-rich diatomaceous ooze (organic ooze) is characterized by the following: (a) abundant diatoms and pollen; (b) chloritic intergrades in the clay fraction; (c) all samples from flat-lying, well stratified beds. The other sediment type (non-organic) is typified by: (a) diatoms and pollen rare or absent; (b) vermiculite/mica/montmorillonite clay fraction; (c) not present in flat-lying beds; (d) texturally more varied than organic ooze. Non-organic samples represent still-exposed depositional products of the Tioga (?) glaciation, reflecting relatively rapid erosion and slumping into deeper parts of the basin. The principal source of non-organic material was the west side where volcanic rocks constitute about half of the area. In contrast, organic ooze samples result from relatively passive post-glacial fluvial erosion. The relative abundance of biogenic components in organic ooze reflects low depositional rates and the clay fraction, rich in chloritic intergrades, points to the dominance of granitic source rocks in the present basin-wide source.

The Mahurangi Limestone from Puketotara Peninsula, Northland, New Zealand

Abstract The Mahurangi Limestone (Oligocene) on Puketotara Peninsula, is a highly deformed, whitish grey, fine-grained rock that typically lacks distinct bedding and identifiable macrofossils. It is faulted against the Waitemata Group (Miocene) and is probably overlain by the Onerahi Chaos-breccia (Upper Tertiary — Quaternary?). The basal contact was not seen. Petrographically the rock is an argillaceous biomicrite containing both terrigenous and organic grains “floating” in an argillaceous, micritic matrix that is seen to be composed mainly of coccoliths under an electron microscope. The limestone is believed to have accumulated as an organic ooze in a sub-tropical, marine environment the depth of which is unknown. The terrigenous grains appear to have been derived from an igneous and sedimentary terrain. In the Lower Miocene, volcanic-rich sediments of the Waitemata Group were deposited on top of the limestone which was later sheared and faulted, this deformation possibly being related to the Upper Tert...

Tropical Lakes, Copropel, and Oil Shale

During a long-continued study of the lacustrine beds of the Eocene Green River Formation, an attempt was made to interpret past events from observation of present-day processes. After a search of some 40 years, four lakes have been found that are producing a kind of organic ooze judged to be a modern analogue of the precursors of rich oil shale. Two of the lakes are in central Africa and two are in Florida. All four are shallow. The ooze in all four is predominantly algal, entirely in the form of minute fecal pellets, and does not decay in warm, wet, oxidizing environments. Several of the most unusual, mummified microorganisms found in the oil shale of the Green River are illustrated as testament to the inference that the organic oozes also were resistant to decay. Studies to determine why these algal oozes do not decay are in progress, but as yet no satisfactory explanation is available.

Chloroplast in Spirogyra From the Green River Formation of Wyoming

A remarkable assemblage of micro-organisms, mostly algae, was found in a thin stratum of exceptionally rich oil shale from the Wilkins Peak Member of the Green River Formation of Eocene age. In this microflora is an almost perfectly preserved germling cell of Spirogyra, which still contains its spiral chloroplast. The cell is turgid and the dark-colored chloroplast appears to be suspended in a nearly colorless, transparent matrix. The preservation indicates that either the cell wall successfully resisted destructive attack by bacteria or saprophytic fungi or that, by chance, it actually was not attacked. The fact that this cell has retained its rounded, turgid form during the full compaction of the enclosing sediments implies that the cell wall was permeable enough so that virtually perfect hydrostatic balance was maintained between the fluids within and outside the cell. Certain other algal cells were flattened to a mere film and cracked radially. The organic ooze in which these organisms were preserved must have remained plastic during the whole process of compaction. This inference is supported by the fact that the thin varves in other nearby oil shale layers were distorted (locally) into sharply pointed peaks by the growth of shortite crystals. Such peaks would surely have lost their sharp crests had they formed before compaction had been completed.

Chloroplast in Spirogyra from the Green River Formation of Wyoming

A remarkable assemblage of micro-organisms, mostly algae, was found in a thin stratum of exceptionally rich oil shale from the Wilkins Peak Member of the Green River Formation of Eocene age. In this microflora is an almost perfectly preserved germling cell of Spirogyra, which still contains its spiral chloroplast. The cell is turgid and the dark-colored chloroplast appears to be suspended in a nearly colorless, transparent matrix. The preservation indicates that either the cell wall successfully resisted destructive attack by bacteria or saprophytic fungi or that, by chance, it actually was not attacked. The fact that this cell has retained its rounded, turgid form during the full compaction of the enclosing sediments implies that the cell wall was permeable enough so that virtually perfect hydrostatic balance was maintained between the fluids within and outside the cell. Certain other algal cells were flattened to a mere film and cracked radially. The organic ooze in which these organisms were preserved must have remained plastic during the whole process of compaction. This inference is supported by the fact that the thin varves in other nearby oil shale layers were distorted (locally) into sharply pointed peaks by the growth of shortite crystals. Such peaks would surely have lost their sharp crests had they formed before compaction had been completed.

Aquatic Biology of the Prairie

General Characteristics. Although much of central United States and Canada is characteristically prairie, the streams of a large part of this region could not, with any justification, be spoken of as prairie streams, since their immediate environment is often heavily wooded. Thus the uplands of Illinois and Indiana are typically prairie, but the valleys through which their streams flow were originally deciduous forest and savannah. The same is true of Missouri and Iowa. As woodlands tend to follow up water courses, it is not until after one has crossed the Missouri River and the eastern part of Kansas and Nebraska, or has gone north into the Dakotas, that one really encounters prairie streams and ponds. Thus the aquatic biology of the prairie is far more restricted geographically than the prairie. Figures 2 and 3, showing Deep Creek of northeastern Kansas, and Peace Creek of central Kansas illustrate the difference between the savannah and prairie streams. The former, flowing between wooded banks, receives shade during the summer and a blanket of dead leaves each fall, which in decomposing, add to the organic ooze or humus of the bottom. This provides food and shelter for a large number of worms, molluscs, insect larvae and other benthic forms, while numerous logs, fallen trees, and masses of roots support their characteristic faunas, rendering the bottom the most productive part of the stream. The prairie stream, on the other hand, receives very little organic matter from the shore. In analyzing mud samples from the bottom of the Big Muddy and Sangamon Rivers in Illinois the author has found as much as 50 to 8o per cent of the dry weight to be organic in nature, while dredgings from the bottom of several prairie streams have shown only gravel, sand, or clay, practically free of organic content. The streams of Eastern Kansas (Fig. 2), form a transition between the typical woodland streams of ' Delivered before the Ecological Society of America in the Symposium on Prairie Ecology, Kansas City, Mo., December 30, 1925. Contribution No. 95 of the Department of Zoology, Kansas State Agricultural College. 2 The author is indebted to her graduate students, Elmer P. Cheatum, Harry G. Walker, and Frank W. Jobes, who took part in most of the field trips. 289

A Contribution to the Origin of the Green River Formation and Its Oil Shale

As a result of the writer's field work on the Green River formation, and his study of the microfossils of the oil shale and of the analogy of the shale with the deposits of modern lakes, there appears to be the following trend in the formation's geologic history: The Green River lakes were formed as relatively stable, shallow, fresh-water bodies; under climatic influence they gradually changed to lakes that periodically filled and evaporated but that supported a luxuriant microflora. In the third stage they became quite strongly alkaline ponds, perhaps playa-like, in the muds of which considerable glauberite crystallized out. In the shallow, expanding and contracting fresh or mildly alkaline lakes of the intermediate stage organic ooze consisting almost wholly of plankton organisms (dominantly microscopic algae) accumulated in large quantities. Bacteria caused active putrefaction of the ooze and evaporation reduced the decaying mass to a syrupy consistency or occasionally to actual dryness. This macerated organic matter was covered by the deposits of the next cycle and subsequently lithified into oil shale.