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... The community consists of the Sporovibrio desulfuricans, 163 cellulose bacteria, Clostridium, of green organisms, certain bluegreens (Phormidium) and Euglenids (Eutreptia viridis), further several protozoa and nematodes. The origin of the black mud is not as Hecht (1933) and Correns (1939) still seem to believe, 164 the decomposition of proteins as Dorothy ...
... 164 In Section 6 Baas Becking referred to Hecht (1933). Reference to Correns (1939, p. 209-210). ...
Lourens Baas Becking (1895-1963) was a Dutch plant physiologist, trained in the Botanical Laboratory of Utrecht University. After graduating in 1919, he worked in America at Stanford University, where he obtained his Doctor’s degree in 1921. From 1928, he was Herzstein Professor of Biology and Director of the Jacques Loeb Physiological Laboratory at the Hopkins Marine Station in Palo Alto. In 1931, he became Professor of General Botany at the University of Leiden. There, he and his staff and students continued to work on the research of microorganisms under extreme saline conditions. In 1939, he was appointed Director of the institutes of the Botanic Garden at Buitenzorg (Bogor) in the Dutch East Indies (Indonesia). In May 1940, when the war broke out, he was in Leiden to retire from his professorship. The war prevented his return to his family and the institutes in the East Indies. Baas Becking made several failed attempts to escape to England. These resulted in imprisonments by the German occupying authorities in Scheveningen (1940-1941) and in Utrecht and the German Zuchthaus in Siegburg (1944-1945). An ordeal that he barely survived due to the inhuman situation in the penitentiary and typhus. In July and August 1944, as a prisoner of the German Kriegsmarine in Utrecht, he wrote in seven weeks a manuscript of Geobiology, an essay on the relationship between living organisms and the earth. It was an update of his earlier ideas. Baas Becking had been inspired by Lawrence Henderson’s The Fitness of the Environment (1913), Victor Moritz Goldschmidt's Der Stoffwechsel der Erde (1922) and Grundlagen der quantitativen Geochemie (1933), Alfred J. Lotka’s Elements of Physical Biology (1924) and Vladimir Vernadsky’s La Géochimie (1924). They were with Frank W. Clarke’s The Data of Geochemistry (1916), sources for his perception of The Universality of Life in 1927, which integrated Vernadsky’s concepts of biosphere and geosphere. Long before James Lovelock and Lynn Margulis defined the Gaia hypothesis in the early 1970s, Baas Becking discussed Gaia or Life and Earth in his inaugural address in 1931. In this tract he also succinctly summarised the ubiquity hypothesis, borrowed from the work of Martinus Beijerinck, as “Everything is everywhere, but the Milieu selects.” The biological “law” was further elaborated in Geobiologie of inleiding tot de milieukunde (1934, English version 2016, Baas Becking’s Geobiology). In the Utrecht prison Baas Becking wrote his scientific testament. In the ten years since the publication of Geobiologie, he “wished to do justice to the work that was performed in Leiden by so many workers”, in an English textbook. With a limited access to scientific literature, he wrote the manuscript Geobiology in a ledger in a barely legible handwriting. The document reflected his vast biological knowledge and his idea of mutual dependence of vital-units (cells, tissues, organs, organism, communities), either of a parasitic, mutualistic or commensalistic character. This relationship was elaborated in his model of symbiosis. His description of the role of man in Geobiology is a personal complaint of a geobiologist over the disastrous treatment of the earth by man. With his concept of “dissipation”, he introduced a material analogue for “the entropy lowering capacity of living systems”. It summarised his conviction that the human intellect and life condition were attributes of free will. Although Geobiology (1944) remained unfinished and had major gaps, it still is an inspiring memoir of a scientist who records his enlightened vision on the relationship between life and earth. In this issue of Geochemical Perspectives the manuscript of Geobiology is integrally transcribed, annotated, edited and introduced by Dr. Alexander J.P. Raat, who graduated in 1974 in Leiden as a plant physiologist. The transcript is published with the original illustrations. A sketch of Baas Becking’s life and works is part of the introduction. The annotation and introduction refer to many of his published and unpublished studies. Among these is an unpublished, further updated and revised version of Geobiology, which he completed in 1953 in Australia.
... The results of such studies have been used to constrain, in some cases even resolve, the phylogenetic affinities of fossil problematica. Taphonomic studies investigating the fossilization potential of cnidarians have been undertaken previously (Walcott, 1898;Schwarz, 1932;Wagner, 1932;Hecht, 1933;Häntzschel, 1937;Schäfer, 1941;Wiman, 1943;Linke, 1956;Kornicker and Conover, 1960;Schäfer, 1962;Hertweck, 1966;Thiel, 1971;Müller, 1984Müller, , 1985Bruton, 1991;Rohznov, 1998 Kear, 1993a, b, 1994;Kear et al., 1995;Hof and Briggs, 1997;Davis and Briggs, 1998;Sansom et al., 2010). In contrast to other groups, especially arthropods and chordates (Briggs and Kear, 1993b;Hof and Briggs, 1997;Sansom et al., 2010), decay experiments have contributed little to models of how key cnidarian groups are likely to appear as fossils. ...
... One of the major steps towards establishing reliable guidelines for the identification of cnidarian fossils is obviously the accumulation of taphonomic data from members of extant Cnidaria. Studies dealing with the taphonomy of diploblastic, gelatinous organisms and more specifically, Cnidarians have been extremely few in number, although there is a long history of such research -scattered over the last 100 years (Schwarz, 1932;Wagner, 1932;Hecht, 1933;Häntzschel, 1937;Schäfer, 1941;Wiman, 1943;Linke, 1956;Kornicker and Conover, 1960;Schäfer, 1962;Hertweck, 1966;Thiel, 1971;Müller, 1984Müller, , 1985Bruton, 1991;Rohznov, 1998 Among the exclusively polypoid anthozoans that supposedly represent the most ancestral cnidarian morphology (Bridge et al., 1992;Matus et al., 2006;Han et al., 2010;Osigus et al., 2013), the entirely soft-bodied actinians have enormous potential for experimental taphonomic studies. No such studies of these have been undertaken previously and it remains unclear why they are underrepresented and probably 'underrecognized' in the fossil record. ...
The fossil record of soft-bodied cnidarians is poor; they are known best from various
Konservat-Lagerstätten. Numerous supposed cnidarian taxa have been erected
without adequate consideration that the morphology preserved is, in part, a function
of the specimens’ taphonomy. This thesis combines analysis of fossils and the results
of decay experiments, to establish the first comprehensive protocols for the
identification of fossil cnidarians.
Preservation of medusae in Jurassic lithographic limestones occurs as a combination
of mould and steinkern(s), the latter represent sedimentary infills of internal cavities
within the body formed at the time of, and after, death. Which features form, and
which are exposed on the plane of splitting through the fossil subsequently, is linked
to the taxon’s biology, plus the sediment consistency at the time of death.
Changes in the morphology of the sea anemone Actinia equina are extremely
variable during decay; their hydrostatic skeleton deforms readily and collapses in an
unpredictable manner. The preservation potential of a characteristic feature, their
tentacles, is limited; they may not be extended at the time of death. The ectoderm is
shed readily (‘delamination’), after which the structure of the mesogloea and internal
anatomy becomes more pronounced. The morphology of a living anemone, a
smooth-surfaced tentacular body, is unlikely to be the typical condition found among
fossils.
During decay of the medusa Aurelia aurita, loss of the mesogloea and reduction of
the outer tissues to a sticky residue results in the collapse of the medusa to a near
two-dimensional structure, and its adhering to the floor of the experimental vessel, as
a highly distinctive ‘sticker’.
Disparate body plans among Cnidaria make it difficult to erect a generalised
taphonomic model; more experimental analogues are needed. The volume and
structure of the mesogloea is an important variable that will control much of the
taphonomic variation among taxa. There appears to be a large element of
unpredictability inherent in the decay of diploblastic taxa. Illustrating this, distinctly
different taphomorphs of the Jurassic potential hydrozoan medusa Palaequorea
rygoli were generated from the simultaneous mass stranding of living specimens.
... Fe values reflect the overall low clay content (Reineck, 1982). At the very base, sediments contain abundant calcium sulphate minerals (gypsum, anhydrite) that are known to precipitate where calcareous seawater is mixed with sulphuric acid (e.g., from decay of organic matter in [semi-]terrestrial environments; Hecht, 1933). An increased basal S content may reflect a relative enrichment by microbial reduction of sea water sulphides (Schroeder & Brümmer, 1968), decreasing towards the top. ...
In 1362 AD, a major storm surge drowned wide areas of cultivated medieval marshland along the north‐western coast of Germany and turned them into tidal flats. This study presents a new methodological approach for the reconstruction of changing coastal landscapes developed from a study site in the Wadden Sea of North Frisia. First, we deciphered long‐term as well as event‐related short‐term geomorphological changes, using a geoscientific standard approach of vibracoring, analyses of sedimentary, geochemical and microfaunal palaeoenvironmental parameters and radiocarbon dating. In a next step, Direct Push (DP)‐based Cone Penetration Testing (CPT) and the Hydraulic Profiling Tool (HPT) were applied at vibracore locations to obtain in situ high‐resolution stratigraphic data. In a last step, multivariate linear discriminant analysis (LDA) was successfully applied to efficiently identify different sedimentary facies (e.g., fossil marsh or tidal flat deposits) from the CPT and HPT test dataset, to map the facies’ lateral distribution, also in comparison to reflection seismic measurements and test their potential to interpolate the borehole and CPT/HPT data. The training dataset acquired for the key site from coring and DP sensing finally allows an automated facies classification of CPT/HPT data obtained elsewhere within the study area. The new methodological approach allowed a detailed reconstruction of the local coastal landscape development in the interplay of natural marsh formation, medieval land reclamation and storm surge‐related land losses.
... As a result of sediment compaction or tectonic pressure, vertebrate fossils may be distorted, i.e. fossil bones may be cracked or even plastically deformed (Müller 1992). Experiments of Hecht (1933) have shown that bones buried together with meat may become decalcified during decomposition and may react plastically when forces were applied. As plastic deformations of fossils are sometimes difficult to detect, they represent a major source of uncertainty for taxonomy. ...
As having evolved on the stem line of mammals, the taxonomy and phylogeny of therapsids (Synapsida) are of special interest with respect to early mammalian evolution. Due to the fact that in most cases soft tissue of fossil vertebrates is not preserved, species can only be distinguished by diagnosis of morphological features of the skeleton. Moreover, investigations of vertebrate fossils are often obstructed, because internal cranial anatomy is usually hidden and parts of the fossils may be embedded in stone matrix. As a consequence, most species of non-mammalian synapsids were only defined on the basis of external skeletal features. Our investigations on Diictodon skulls (Therapsida, Anomodontia) show that non-destructive methods are very useful to clearly distinguish fossil species. We, therefore, propose using modern non-destructive techniques such as neutron tomography, synchrotron tomography, and micro-computed tomography (μCT) as standard tools for the investigation and virtual reconstruction of fossils and to include features of the internal cranial anatomy into morphological descriptions and phylogenetic analyses of fossil vertebrates.
... Shells and skeletons are rarely in chemical equilibrium with the interstitial fluids of the sediment, which lead to dissolution (Chave 1967;Lawrence 1968;Brachert & Dullo 2000). Dissolution can start as early as death of an organism and its burial into the sediment (Hecht 1933;Aller 1982). The propensity of individual shell to dissolution depends on its size, microstructure and mineralogy (Martin differences of biodiversity recorded among litholofacies have also been approached at regional level by the comparison of taxon associations from lithified and unlithified lithologies from the middle Eocene of Paris Basin (Lutetian: Vanves, Nanterre, Damery, Ferme de l'Orme, Chaussy, Grignon and Villiers-Saint-Frédéric; Bartonian: Baron), Aquitaine Basin (Bartonian: Blaye and Gironde) and Italy (Lutetian: San Giovanni Ilarione, Verona). ...
Lithification is stressed as a major bias for the palaeobiodiversity evaluation. Although this bias is
often discussed in the literature, it has rarely been quantified. This work offers a first estimation of
diagenesis impact over mollusc diversity record for a single bed of the “Falunière” of Grignon (middle Lutetian, France). This bed possesses the particularity of displaying two lithological facies: one lithified and the other unlithified, both from a same taphocoenosis. Mollusc diversities of three unlithified and three lithified samples have been compared (1453 specimens among 131 species). The comparison was made possible by the construction of rarefaction curves extrapolated for 30 samples and the introduction of two indexes: the eDG (extrapolated Diagenesis Gap) that gives a value of diversity loss between two facies and the STD (sampling/diagenesis bias threshold) that gives the threshold (in number of samples) after which eDG can be estimated. The analysis reveals that nearly 80% of species richness is not recorded in the lithified facies, and that loss can reach 100% for species smaller than 2 mm. The bias linked to specimen sizes is discussed, both for large and small shells. The differences of biodiversity recorded among litholofacies have also been approached at regional level by the comparison of taxon associations from lithified and unlithified lithologies from the middle Eocene of Paris Basin (Lutetian: Vanves, Nanterre, Damery, Ferme de l’Orme, Chaussy, Grignon and Villiers-Saint-Frédéric; Bartonian: Baron), Aquitaine Basin (Bartonian: Blaye and Gironde) and Italy (Lutetian: San Giovanni Ilarione, Verona). A revaluation of biodiversity estimates of San Giovanni Ilarione that consider lithification bias suggests that the Tethyan regions housed similar or higher species richness than the Paris Basin during the Lutetian, which does not agree with a raw data comparison but which would better fit with the hypothesis of a biodiversity hotspot in the western Tethys. Any future comparisons of the biodiversity from distinct regions or time intervals have to consider the conditions of preservation and the lithification bias.
... Our measured rates in these short-term experiments are, however, within the range of other previous measurements of shell degradation. In an early study of shell dissolution Hecht (1933) showed that, immediately after death, mollusc shells may lose 25% of their mass in a matter of weeks. Driscoll (1970) found mass loss rates of up to 16% per year of shells in Buzzard's Bay, MA, attributed largely to boring organisms. ...
Oyster shell is a crucial component of healthy oyster reefs. Shell planting has been a main component of oyster restoration efforts in many habitats and has been carried out on scales from individual and grassroots efforts to multiagency efforts across entire estuaries. However, the cycling and lifetime of the shell that makes up the bulk of an oyster reef has only recently received attention, and most of the work to date has focused on the role of epi- and endobionts on shell degradation. Here we report findings from a laboratory study in which we manipulated pH in a flow-through control system using water from the mesohaline mouth of the Patuxent River to measure dissolution rates of intact oyster shell. Shells from the Eastern oyster (Crassostrea virginica Gmelin 1791) with three different legacies were exposed to 4 levels of pH that encompass a range typical of the mesohaline waters of the Chesapeake Bay (similar to 7.2-7.9 on the NBS scale). Mass loss over a 2-wk period was used to measure dissolution rate on 3 shell legacies: fresh, weathered, and dredged. We found that pH and shell legacy had significant effects on shell dissolution rate, with lower pH increasing dissolution rate. Fresh shell had the highest dissolution rate, followed by weathered then dredged shell. Dissolution rates were significantly different among all 4 pH treatments, except between the lowest (similar to 7.2) and the next lowest (similar to 7.4); however, shells lost mass even under noncorrosive conditions (similar to 7.9). We discuss the implications of our findings to ongoing efforts to understand shell budgets and cycling in oyster reef habitat, the interaction of biological and geochemical agents of shell degradation, and the complexity associated with shell carbonate cycling in the unique milieu of the oyster reef.
... (2) Chemical destruction was studied experimentally by Klähn (1932), Hecht (1933) and Chave et al. (1962). Solubility of the shells depends on the mineral composition of the shell and the chemistry of the water which surrounds it. ...
CONTENTS Introduction...................... 4 I Description of the area............ 5 Topography................................................ 5 Climate........................5 Hydrography: Tides and currents................... 9 Temperature and salinity......... 11 Oxygen........... 12 Turbidity........... 14 Sediments : Grain-size........... 14 Organic carbon content........ 16 Summary.............. 19 II Methods.............. 19 Discussion of methods........... 20 Mollusc-assemblages............ 25 III The Rio Ulla and Umia.......... 25 Fauna and environment..... ..... 25 Important species............ 31 Comparison with other areas.......... 32 Transport.............. 32 IV The marginal zone............ 32 The environment............. 32 The marginal fauna............ 33 Important species............ 34 Other skeletal remains........... 42
... The close association of concretions with fossils and organic matter suggested that the decomposition of the latter played a crucial role in the concretion-forming process. A possible mechanism for such relation was demonstrated by Hecht (1933) who showed that upon decomposition of fish, nitrogen is released in the form of ammonia or amines, thus raising the pH. This may then lead to the precipitation of CaCO3: NH3 + Ca 2+ + HCO3--+ CaCO3 + NH4 ÷ Berner (1968) further investigated this possibility, carrying out laboratory experiments in which anaerobic bacterial decomposition of fish resulted both in an increase in pH and in precipitation of Ca 2+ from solution. ...
Carbonate concretions of variable sizes occur in the upper member of the Senonian (Upper Cretaceous) Mishash formation in Israel. Eight concretions and their surrounding country rocks were examined in the field, in thin sections and by X-rays. The isotopic composition of carbon and oxygen in the carbonates, the amount of acid insoluble residue, as well as the concentrations of P2O5, Ca, Mg, Sr and Fe were determined. Other concretions and country rocks were analyzed for oxygen and carbon isotopes only.The concretions are composed of almost pure, microsparitic calcite, whereas the country rocks are porcellanitic-phosphoritic chalks. Compared with the surrounding rocks, the concretions are strongly enriched in 12C and are depeleted in insoluble residue, P2O5, SiO2, Fe, Sr and Mg.It is postulated that the concretions were formed by addition of CaCO3 to sites of anaerobic decomposition of organic matter, while CaCO3 was mobilized in the surrounding sediments, in which aerobic decomposition of organic matter prevailed.Several consequences of this model are considered, concerning the quantitative volume changes, as well as the distribution of SiO2 and Mg between concretions and country rocks.
Die oberen Schichten des Bodens tragen stets eine äußerst kompliziert zusammengesetzte Bevölkerung von lebenden Organismen, deren Lebensvorgänge dazu beitragen, den biologischen Stoffkreislauf im Gange zu halten und so den Boden zu einem geeigneten Standort für die höheren Pflanzen zu machen. Die gesamte Bodenpopulation umfaßt ein sehr breites Spektrum von Lebensformen, das sich von einzelligen Organismen bis zu Säugetieren (Maulwürfen) und Wurzeln der höheren Pflanzen erstreckt. Hiervon repräsentieren die Mikroorganismen einen sehr wichtigen Bestandteil sowohl rein quantitativ in Form von lebender Masse als auch mit Rücksicht auf die biologische Tätigkeit, die sie entfalten. Die Mikroorganismen des Bodens sind ganz überwiegend pflanzlicher Natur: Bakterien (einschließlich Strahlenpilze), niedere Algen und Pilze (obwohl die höheren Formen der letzteren nicht eigentlich mikroskopisch sind). Hierzu kommen noch tierische Bodenbewohner wie Protozoen, Nematoden und andere niedere Metazoen. Die Mikrobiologie des Bodens im eigentlichen Sinne umfaßt die Kenntnis von der Natur und Identität dieser Organismen, ihrem Vorkommen und ihrer Wirksamkeit im Erdboden selbst. Wie Winogradsky hervorgehoben hat, ist dagegen ihr Verhalten in Reinkultur unter künstlichen Bedingungen streng gesprochen als ein Zweig der allgemeinen Mikrobiologie anzusehen.
This chapter discusses the syndiagenesis–anadiagenesis–epidiagenesis: phases in lithogenesis. Diagenesis of sediments is understood as those physical and chemical changes that the sediment undergoes during and after deposition and lithification, without introduction of great heat or pressure. Three phases of the overall rate process were defined on a temporal and spatial basis. In an ideal model, a dynamic evolution takes place within the constraints of increasing time, depth of burial or exposure, and changing hydrologic-geochemical systems. Syndiagenesis is the early phase, synchronous with deposition and early burial, being strongly influenced by biochemical agencies in a fluid regime dominated by the entrapped waters of the sea- or lake-floor. Anadiagenesis is the deep-burial phase marked by compaction and maturation, strongly influenced by increasing pressure and the upward expulsion or transit of connate waters that are often highly mineralized or saline. Epidiagenesis follows uplift or emergence that brings surficial, meteoric waters into circulation often displacing pre-existing fluids and reversing numbers of geochemical processes. Eustatic fluctuations or tectonism may accelerate or short-circuit the ideal triple-phase evolution.
A new specimen of the protorosaurian diapsid reptile Tanystropheus is described. The specimen was collected at the Valle Serrata locality (Switzerland) and is of Ladinian (Middle Triassic) age. Its study elucidates some issues regarding the anatomy of Tanystropheus to be addressed, and allows to suggest hypotheses about its mode of life. In particular, the specimen is the first one in which the skin and other soft tissues can be described. In particular, wide patches of black phosphatic material, filled with small carbonate spherules are preserved, as it occurs in corpses lying in stagnant water due to decomposition of consistent amount of proteins. This suggests that a huge mass of flesh was present in the caudal part of the body, shifting posteriorly the center of mass of the animal and helping in balancing the weight of the neck even if raised off horizontal plane and out of water. In addition, no evidence of caudal autotomy is present in Tanystropheus and the structure of the tail and of the limbs are consistent with a shoreline habitat rather than with a fully aquatic mode of life.
This chapter discusses taphonomy and paleoecology. It is always refreshing and sometimes informative to look at the same thing from a different point of view. Paleontologists and archaeologists look at the same thing from different points of view, and a comparison of the ways in which practitioners of these two disciplines go about their work can clarify the unique features and common problems of each. Taphonomy is a word coined by the Russian paleontologist I. A. Efremov from the Greek words for tomb or burial—taphos—and for law or systems of laws—nomos—to denote that subdiscipline of paleontology devoted to the study of processes that operate on organic remains after death to form fossil deposits. In common with many other branches of historical science, taphonomy involves two distinct but necessarily related lines of investigation. The first is devoted to studying observable contemporary processes involved in this transition of organic remains from biosphere to lithosphere, focusing on those that produce effects analogous to those traces observed in the fossil evidence. The second is devoted to analysis of the prehistoric evidence in light of findings derived from the first line of investigation. Properly pursued, taphonomy can provide paleoecologists with information about the spatial, temporal, and biological factors involved in the formation of fossil assemblages.
Fossils have been simply defined as traces of ancient life. Paleontology, the study of these remnants, can thus well be thought of as four-dimensional biology [1]. To adapt one description of biology,” the aim of paleontology is to understand the structure, functioning and history of ancient organisms and of populations of such organisms” [2]. Because of the nature of their material, however, paleontologists have often needed information on aspects of modern life that have scarcely interested neontologists. Examples that might be cited are the whole field of actuopaleontology (with close links to forensic medicine — see below), the study of population structures not only of living communities but also of dead assemblages [3], and the detailed morphological study of preservable tissues.
A review of marine sedimentological data leads to a classification of three phases of diagenesis; these are: (a) syndiagenesis (marked by syngenetic authigenesis in two stages, initial or oxidizing and early burial or reducing), that lasts from 1, 000 up to about 100, 000 years and may extend to depths from about 1 to 100 m; (b) anadiagenesis (marked by hypogene authigenesis, i.e., non-magmatic ascending waters and "natural chromatography"), extending from 10 3 to 10 8 years, and 1 to 10, 000 m depth; (c) epidiagenesis (marked by deep meteoric waters and epigene authigenesis) that may by-pass anadiagenesis, due to tectonism, and may extend from 10 3 to 10 9 years, and in depth about 1 to 3, 000 m. Many authigenic minerals formed during different stages of diagenesis may be experimentally duplicated, but much remains to be done.
This paper discusses deposits laid down in tidal areas in which the range of tide is great. The sediments of the Jade near the mouth of the Weser in Germany are taken as an example. They consist mainly of soft mud, but in places contain admixtures of sand. As a general rule, mud is deposited near highwater mark, silty or sandy mud in areas of intermediate water, and fine sand near the position of the water at low tide. In some places the sediments are laminated and cross-bedded. This lamination is not destroyed by burrowing and bottom organisms that live in great profusion on these tidal flats, probably owing to the fact that the sediments are deposited so rapidly that the or-ganisms do not have time to rework them before they are buried by additional deposits. In some places as much as 3 meters of sediment are deposited in a year. The material laid down by tidal waters along the north coast of Germany has the economic advantage of adding arable land to the coast, of increasing the fertility of the soil, and of serving as a therapeutic agent in the form of mud baths.
Disease, overharvesting, and pollution have impaired the role of bivalves on coastal ecosystems, some to the point of functional extinction. An underappreciated function of many bivalves in these systems is shell formation. The ecological significance of bivalve shell has been recognized; geochemical effects are now more clearly being understood. A positive feedback exists between shell aggregations and healthy bivalve populations in temperate estuaries, thus linking population dynamics to shell budgets and alkalinity cycling. On oyster reefs a balanced shell budget requires healthy long-lived bivalves to maximize shell input per mortality event thereby countering shell loss. Active and dense populations of filter-feeding bivalves couple production of organic-rich waste with precipitation of calcium carbonate minerals, creating conditions favorable for alkalinity regeneration. Although the dynamics of these processes are not well described, the balance between shell burial and metabolic acid production seems the key to the extent of alkalinity production vs. carbon burial as shell. We present an estimated alkalinity budget that highlights the significant role oyster reefs once played in the Chesapeake Bay inorganic-carbon cycle. Sustainable coastal and estuarine bivalve populations require a comprehensive understanding of shell budgets and feedbacks among population dynamics, agents of shell destruction, and anthropogenic impacts on coastal carbonate chemistry.
Decomposition of non-amine compounds, such as lactate, by the anaerobic bacterium Desulfovibrio desulfuricans produces a change in the chemistry of the surrounding fluids. Empirical studies demonstrate the following: 1.(1) D. desulfuricans are tolerant of alkaline pH-values (maximum pH = 9.2 for the strain used).2.(2) Growth results in the lowering of pH to values near neutrality.The factors which control this lowering in pH are release of CO2 and the establishment of a proton gradient across the cell membrane. This energy-yielding metabolic process may make a significant contribution towards carbonate dissolution reactions and diagenetic reactions involving silica. These include silicification of Precambrian microorganisms, nucleation of chert nodules, and the replacement of sulfate minerals by silica.
The Souedie oil field is situated in northeastern Syria. Main reservoir is the Upper Cretaceous Massive Limestone which can be subdivided into zone A, B and C. Fine-grained calcarenites (biomicrites and biopelsparites) predominate in zone A. Minor secondary dolomites are intercalated. Recrystallized calcilutites (biomicrites and biopelsparites) prevail in zone B. Zone C is mainly composed of secondary dolomite.
The porosity of the Massive Limestone ranges from 2 to 22 per cent. The permeability, however, is low (0 to 50 md).
The reservoir rocks were deposited within the mobile shelf of the Mesopotamian trough at the margin of a bank. Zone A can be divided into bank and slope facies by means of bedding features, grain size distribution and mineral content.
Dolomites of Lower Cretaceous and Lower Jurassic age were briefly investigated.
Thirteen amino acids (glycine, alanine, valine, serine, threonine, arginine, aspartic acid, glutamic acid, methionine, cystine, tyrosine, proline and histidine) were isolated from 21 carbonate rock and 2 oil samples and analyzed quantitatively. The total amount of amino acids is lower in the rock than in the oil specimens. The calcilutites of zone A and B contain less amino acids than the calcarenites. Secondary dolomites deviate in their quantitative composition from the surrounding limestones. Consequently dolomitization influences the distribution of amino acids. A relationship between depth of burial and amino acid distribution was not observed.
Seven carbohydrates (galactose, glucose, mannose, arabinose, xylose, ribose, and rhamnose) were detected in the oil specimens. The total amount of carbohydrates is higher than the total amount of amino acids.
In addition more experimental work is suggested.
Typical taphonomic features of the fish of the Solnhofen Plattenkalk are discussed with regard to the palaeoenvironment.This environment can be characterized as a hostile, hypersaline and dysaerobic bottom zone with less saline surface waters which allowed for the existence of life, though the organic production rate was low. Current activity on the sea floor was minimal. Monsoonal storms were probably responsible for the sudden death of many fish. These storms also brought the carbonate ooze which was deposited very rapidly by suspension fallout. Characteristic of the diagenesis of the Solnhofen Plattenkalk is the formation of a sticky surface coating and a relatively early solidification.RésuméLes mécanismes taphonomiques des poissons des Calcaires en Plaquettes de Solnhofen sont discutés en relationavec le milieu de dépôt. Celui-ci se caractérise par un tranche d'eau inférieure, hypersaline, mal oxygénée et azoique, et une tranche d'eau supérieure moins salée et aérée qui permettait la vie bien que la production organique ait été peu considérable. L'activité de courants était minimale sur le fond. Des tempêtes de mousson furent probablement responsables de la mort brusque d'une grande partie des poissons. Elles apprortèrent aussi la boue calcaire qui fut déposée très rapidement à partir des particules en suspension (“Flinze”). Deux traits typiques pour la diagenèse des Calcaires en Plaquettes de Solnhofen sont, d'une part, la formation d'un voile résistant adhérant à la surface de la boue calcaire et, d'autre part une induration précoce.
The increasing eutrophication of tidal flat soils on the North Sea coast and the appearance of "black spots" gave rise, to this study. The aim was to find pedobiochemical indicators for the development of "black spots": Artificially eutrophicated soils were compared with untreated soils in the field and laboratory. The pH values of the artificially eutrophicated and natural soils often differed by nearly one unit. The treated soils mostly showed lower redox potentials (similar to -300 mV) than the untreated samples (similar to -250mV). The mean sulfate concentrations were 2.2 mM in the eutrophicated laboratory soils and 13:1 mM in the eutrophicated field soils, compared with 12.5 mM and 20.2 mM in the untreated ones. Consequently, the SO42-:Cl- ratios and SO42- differences were lower in the treated soils. Non-eutrophicated soils showed methane concentrations of < 5 nmol cm(-3), whereas the eutrophicated soils showed up to 217.0 nmol cm(-3) in the field and 479.1 nmol cm(-3) in the laboratory. Differences between field and laboratory data were mainly due to a continuous sulfate supply and reoxidation process only possible in the field. Although all parameters showed differences between the eutrophicated and untreated soils, only the methane data did not overlap with their interquartile ranges. Those of the untreated soils were 2-7 nmol cm(-3) and those of the treated were 12-360 nmol cm(-3). Thus, threshold values can be defined. Methane concentrations of approximately > 10 nmol cm(-3) refer to the beginning eutrophication process and those in the range of > 100 nmol cm(-3) to advanced processes, phenologically forming "black spots'".
The Burgess Shale (Middle Cambrian) polychaetes Canadia spinosa Walcott,
Burgessochaeta setigera (Walcott) gen. nov. and Peronochaeta dubia
(Walcott) gen. nov. are redescribed on the basis of Walcott's type
specimens and on much additional material. Two new polychaetes
Insolicorypha psygma gen. et sp. nov. and Stephenoscolex argutus gen. et
sp. nov. are described. A poorly preserved specimen of unknown generic
affinity is described as type A. The polychaetes are preserved as thin
films that adhere to both sides of the split in the rock so that part
and counterpart may be available. In C. spinosa, B. setigera and I.
psygma, parts of the bodies such as the fascicles of setae are separated
by thin layers of sediment that apparently seeped in during turbulent
transport in turbidites or mudflows. The bodies therefore lie on two or
more planes of microbedding and the factors that control exposure across
a specimen are discussed. Aspects of the palaeoecology of the Burgess
Shale are reviewed, including the distance the biota was transported
prior to burial, the reasons for the exquisite preservation, and the
effects of sedimentary compaction. C. spinosa was characterized by broad
notosetae that extended across the dorsum, and large fascicles of
neurosetae. Lobate branchiae were situated in the inter-ramal spaces.
The prostomium bore a pair of elongate tentacles and the straight gut
had an eversible unarmed proboscis. Several lines of evidence suggest
that C. spinosa was an active benthonic swimmer. B. setigera was
peculiar in possessing identical notosetae and neurosetae along the
entire body. Long anterior tentacles, possibly of peristomial origin,
may have been used in feeding. Indirect evidence indicates that B.
setigera inhabited a burrow which it might have excavated with its
proboscis. P. dubia may also have burrowed but it had uniramous
parapodia bearing simple and acicular setae. The prostomium bore a pair
of short appendages. I. psygma had extended neuropodia bearing cirri and
elongate setae. The notopodia were reduced and cirri appear to have been
wanting. The peculiar prostomium carried a pair of appendages. I. psygma
is regarded as a pelagic polychaete. S. argutus possessed uniramous
parapodia with simple stout setae. The bilobed prostomium bore at least
one pair, and perhaps three pairs, of short appendages. Type A was the
largest of the Burgess Shale polychaetes and had prominent setae on at
least the anterior section of the body. Type A was a sediment eater but
the feeding habits of the other polychaetes are uncertain. Particular
attention is given to the influence of decay on the Burgess Shale
polychaetes. To place the Burgess Shale polychaetes in some geological
perspective other Cambrian worms, including a polychaete from the Spence
Shale of Utah, are briefly redescribed and the late Precambrian
(Ediacarian) worms Dickinsonia, Spriggina and Marywadea are assessed.
Contrary to the findings of other workers, no convincing evidence for
placing these latter worms in the polychaetes is forthcoming.
Sedimentmikrobioiogie und ihre geologischen Aspekte
Oxygen is a bio-limiting element for metazoa and one of the most important factors influencing species diversity and abundance in the marine realm. Equally, the absence of oxygen is generally considered to be essential for the inhibition of microbial decay and the formation of organic-rich sediments. As such, the determination of depositional palaeo-oxygenation values of ancient rocks has become a fundamental quest for the palaeoecologist and mudrock sedimentologist. In this paper the development of the tripartite anaerobic-dysaerobic-aerobic terminology for oxygen-related biofacies and the recent additions of the exaerobic and poikiloaerobic biofacies are reviewed. The new, non-genetic, oxygen-restricted biofacies (ORB) scheme is also presented. Chemosymbiotic life strategies have been suggested to be important in many extinct black shale taxa but a glance at modern chemosymbionts casts doubt on the significance of this mode of life in ORB. A review of lowest dysaerobic benthic forms throughout the Phanerozoic reveals the repeated occurrence of a few morphologies almost exclusively derived from the brachiopods and bivalves. Geochemical indices of palaeo-oxygen levels are also reviewed.
The recent renaissance in the development of criteria for the determination of palaeo-oxygen values has led to the recognition of a considerably greater variety of dysaerobic biofacies in the geological record. This is illustrated with two case studies, the first, from the celebrated Burgess Shale of British Columbia, shows a depositional environment dominated by a fluctuating oxycline. The second case study, from widely separated earliest Triassic marine sections, illustrates the possibility of a widespread (global) dysoxic event at this time.
constraints reveal that the opisthotonic posture is not a peri-but a postmortem phenomenon. By analysing the timeline of decomposition, it is possible to recognise different stages of decay, depending on the varying decay resistance of soft tissues. Adipocere formation must have blocked further decay until embedding was completed by minimal sedimen-tation. Analyses of the palaeoenvironment of the basins of the Solnhofen Archipelago show that the conditions of deposition of individual basins cannot be considered to be similar, even inside the same time frame. Therefore, a gen-eralised approach of looking at the depositional setting must be excluded. Assumptions by Faux and Padian (2007) that the accepted palaeoenvironmental reconstruction of the Solnhofen Fossillagerstätte has to be questioned in the light of the opisthotonic posture hypothesis enforce the need for a review of palaeoecological factors of the Franconian Plat-tenkalks from a taphonomic perspective.
The first edition of this chapter provided a brief review of the geochemistry of carbonate minerals, summarized general aspects of their thermodynamics and the kinetics of their precipitation and dissolution, and then used the natural division between deep-sea marine carbonates (chalks and pelagic muds) versus shoal-water carbonates (skeletal and nonskeletal materials) to organize details of the formation, distribution, and subsequent diagenetic alteration of these phases. A substantial focus in this treatment was thus the description of the behavior and fate of carbonate minerals in natural settings. In this chapter, this latter material appears largely unchanged. The aim in this revision is not simply to trudge through calcite, dolomite, and magnesite rate equations, detailed reviews of which are available elsewhere; instead, the intent is to provide background for the selective discussion of recent work on carbonate mineral surfaces (mostly calcite).
Several articulated, but incomplete, acanthodians from the Bunga Beds (late Givetian/early Frasnian) of the southern coast of New South Wales are tentatively identified as ischnacanthids. Heads are missing from all three prepared specimens. They exhibit the following characters: two dorsal fin spines; long, slender scapulocoracoids; slender, relatively deeply inserted, unpaired fin spines; minute scales with a fairly smooth, flat, crown; and an increase in size of normal body scales towards the tip of the tail. The fish are preserved in black, finely laminated shales, which were probably deposited as deep water, lacustrine sediments. The rarity, burial conditions, and headless state of the Bunga Beds acanthodians indicate that they might have died in shallow water, sunk to the bottom, refloated by gas‐induced buoyancy, with the heads lost while drifting out to deeper waters, where the bodies finally sank to a scavenger‐free, anaerobic substrate.
Lithogenesis of the Steinmiihl Limestone of the Arrach Quarry (Jurassic, Austria)
The Upper Jurassic Steinmuhl Limestone Group on its type section (Arrach Quarry, Lower Austria) is subdivided into the following four members:
These various sedimentary units represent a gradual change in the environments during sedimentation. The sequence sets in with the Filament Limestone. It possibly represents a sublittoral Lamellibranchiata debris and is of Callovian (?)age. Though the marine deposition continued without interruption to the Upper Jurassic, the environment changed markedly. The sea became deeper and the Filament Limestones were followed by pelagic-bathyal Radiolaria Siliceous Limestones. A distinct difference in the degree of subsidence within the Upper Jurassic geosyncline led to the formation of bathyal furrows and swells. Over the latter the calcilutite Saccocoma and Calpionella Limestones with mainly pelagic fossils were deposited in Kimmeridgian and Port- landian. Their thickness is small, for currents swept much sediment into the deeper furrows, in which the Oberalm stratas arose in great thickness at this time.
Ten suites of 16 common types of invertebrate hard parts were placed in acid baths for 24 hours to determine relative rates and common styles of dissolution. Skeletal mineralogies included aragonite and both high-magnesium and low-magnesium calcite. Hard parts included barnacle cxoskelctons, cchinoid tests, gastropod opercula and gastropod and bivalve shells. Calcitic barnacle plates dissolved most rapidly, aragonitic and high magnesium calcitic hard parts showed intermediate rates, and the calcitic shells of the oyster dissolved at the lowest rate. The surface area to weight ratio of the hard parts correlated (r=0.650) significantly with the hard part's rate of dissolution. Skeletal remains with a high surface area to weight ratio dissolved faster than those with a low surface area to weight ratio. Skeletal porosity and mineralogy appeared to be responsible for additional variation in the rate of dissolution. The effect of the surface area to weight ratio is sufficient to overcome the effect of mineralogy. Dense, compact aragonitic hard parts can persist longer than porous, thin calcitic remains. Typical features associated with skeletal degradation include development of chalky textures, thinning of distal margins, surface etching and formation of holes in bivalve muscle scars. Such features may aid in the recognition of partial dissolution of skeletal remains in the rock record. □Taphonomy, paleoecology, fossil-diagenesis.
A bstract
All sorts of organic matter preserved under anaerobic conditions and transformed in reducing environments may form components of natural crude oils; such oils are linked to sapropel deposits by their contents in porphyrins and trace metals.
The influence of domestic sewage on intertidal sand and mud flat benthic communities has been studied at three minor outfalls around the North Sea island of Sylt (F. R. Germany) and at the main outfall of Vancouver, B. C. (Canada). During high tide, domestic waste water was found at the water surface due to its lower specific gravity. Consequently, O2 depletion and salinity decrease occured mainly in surface waters. Oxygen deficiency prevailed in the sediment-water layer, when settled sewage particles were re-suspended by strong tidal currents. This resulted in anaerobic conditions at the sediment surface for up to 40% of the day. Substantial pH decrease and increase in seston load of the water were observed only along the sewage channels and around the outlets when large quantities of sewage were discharged. The amount of particulate organic material increased up to 10% and more in muddy sediments due to sedimentation of sewage sludge. Considerable eutrophication of the mud flats resulted from nutrient load of the sewage and from decomposition of faecal material deposited on the sediments. The vertical distribution of microalgae in the sediment was not influenced by sewage. Primary productivity of microalgae on the sediment surface was positively correlated with the degree of pollution. In heavily and mediumly polluted zones, heterotrophic bacterial production exceeded primary production rates at the sediment surface. Compared with unpolluted intertidal flats the number of macrobenthic species was not reduced in polluted mud flats. In regard to overall species abundance, the macrofauna associations of the disposal area showed three distinct zones: (1) Heavy pollution around the outfall resulted in a degradation zone either without benthic invertebrates or with a very low density of individuals; (2) medium polluted areas were characterized by a zone of maximum density; (3) with decreasing or diminishing pollution the number of individuals returned to normal values (background values). The distribution of species within these zones indicated a significant difference between the response of the channel fauna and the flat fauna to pollution: while the number of species increased continously inside the channels with decreasing pollution, the species variety of the tidal flats was positively correlated with the number of individuals. The diversity of the benthos inside the channels was negatively correlated with the degree of pollution, whereas the diversity indices for the fauna on the tidal flats increased quickly from the centre of pollution, remained at a high level in the medium polluted zone, and decreased again to the area of diminishing pollution. The number of dominating species in the sewage channel increased from the outlet towards the low-tide level, with ratios of 0.9 to 0.33; on the flats the number remained constant throughout the three zones, with maximum ratios of 0.5, demonstrating that no qualitative changes for the macrobenthos of intertidal flats result from domestic sewage disposals. In polluted intertidal flats the macrobenthos is dominated by muddy-sand species whose adaptability to varying sedimentary factors, such as grain size distribution and content of organic material (coefficients of variability: 50.7 and 45.7%, respectively), is relatively high compared with mud and sand species. A special indicator community for polluted intertidal areas does not exist. Intensified waste-water treatment prior to discharge reduced the size of the degradation zone around the outfalls while it simultaneously caused a lower density of the macrobenthos in the medium polluted zone.
This report presents the results of taphofacies analyses of shelly cheniers (mollusk-dominated lag-concentrations) from the
tidal flats of northeastern Baja California, Mexico. The three generations of moderm (formed during last 70 years), submodem
(younger than 1,500 BP), and subfossil (5,000–2,000 BP) cheniers can be distinguished by their position relative to the shoreline,
their topography, and the radiocarbon-age of their shells. The generations differ in the duration and complexity of their
taphonomic history. Sixty-one samples from nine localities were collected to test the utility of the taphofacies approach
for studying chenier-type shell deposits. The three chenier generations, although all dominated by the bivalve molluskMulinia coloradoensis, differ significantly in their taxonomic composition due to taphonomic and/or biologic factors. The taphofacies analysis
included 4,334 specimens ofM. coloradoensis described by nine taphonomic variables. Univariate analysis of those variables indicated that the shells that accumulated
in the cheniers are little-affected by biological processes (bioerosion, encrustation), and moderately affected by physical
processes (fragmetation, cracking, peeling, edge preservation). Only the luster features of shells (external luster, internal
luster, and internal features) vary substantially and consistently with chenier age —a result of subaerial weathering. Multivariate
taphofacies analysis discriminates the three generations of cheniers even when the poorly preservable luster variables are
excluded from the analysis. This suggests that taphofacies discrimination is possible for fossil cheniers. The shells collected
from the chenier surface have substantially poorer preservation than shells from the subsurface, indicating that taphonomic
degradation in the chenier plain environment is a surface phenomenon. Chenier plain shelly assemblages are taphonomically
distinct from assemblages formed in other marine environments: they have a very low frequency of macroscopically recognizable
bioerosion and encrustation. The existence of preservable taphonomic differences between the cheniers that differ in their
age (i.e., duration of preburial history), suggests that fossil lag concentrations may be useful in detecting incompleteness
gradients along stratigraphic boundaries. A ‘taphonomic clock’—a correlation between a ‘time-sincedeath’ and shell preservation—was
found only for luster features, taphonomic attributes that are unlikely to be preserved in the fossil record.
Ausgehend von den Mineralisationen, welche Fossilien der unterdevonischen Dachschiefer des Hunsrückschiefers zeigen, wird
das bisherige Bild von den mutmaßlichen Prozessen, die sich bei der Fossileinbettung und Diagenese des umgebenden Gesteins
abgespielt haben, geprüft und ergänzt.
Es zeigt sich, daß die fossilerhaltende Gunst dieser Schiefer von einer frühdiagenetischen Hartteil-Verkiesung und-Verquarzung
sowie Konkretionsbildung bewirkt wird. Unter den Konkretionsmineralen spielen Phosphorite eine wichtige Rolle. Solide Kalkgerüste
wie die der Korallen besaßen von vornherein einen gewissen Schutz gegen die Verdrückung.
Der Ton wurde rntgenographisch, mikroskopisch und mit der Differentialthermoanalyse untersucht. Aus den Ergebnissen von Beobachtungen in der Natur und petrographischen Untersuchungen an den Geoden knnen Einzelheiten ber ihre Entstehung abgeleitet werden. Insbesondere wird gezeigt, da aus dem Karbonatgehalt der Geoden der Wassergehalt des Tones zur Zeit der Bildung der Geoden auf einfache Weise berechnet werden kann. Die Minerale in den Geodenspalten, insbesondere der Whewellit, werden beschrieben und in eine Ausscheidungsfolge gegliedert. Die Bildung und Anreicherung der Minerale in den Geodenspalten wird auf Lslichkeitserhhung durch hheren Druck im Ton im Vergleich zu dem in den Geodenspalten zurckgefhrt.
Skeletonized organic remains display various modes of occurrence which may be used to better understand the sedimentary dynamics of strata within which they occur. Aspects of skeleton biostratinomy and early diagenesis are distributed nonrandomly within the stratigraphic record and, therefore, are useful in discriminating taphonomic facies. For purposes of taphonomic comparisons, skeletonized marine taxa are reduced to five generally defined types: massive, arborescent, univalved bivalved, and multielement. Different skeletal types display different attributes which reflect specific responses to physical, chemical, and/or biological processes. The taphonomic properties of disarticulation, reorientation and sorting, fragmentation, corrosion and abrasion, skeletal dissolution, and early diagenesis display patterns which are predictable with respect to a variety of inter-related physico-chemical parameters. These can be quantified through indices which evaluate relative frequencies of occurrence.
The post-mortem fate of shells added by natural mortality to modern death assemblages was studied to determine the importance of taphonomic loss during the initial stages of the formation of a fossil assemblage. Individuals are added to the living community in pulses, usually by larval settlement. These input pulses usually are followed by discrete input pulses into the death assemblage. The decay of these discrete input pulses in the death assemblage can be used to measure the rate of taphonomic loss as expressed by the half-life of a pulse. For instance, if a species has a half-life of 125 days and the input pulse begins with 500 individuals, then the number of shells remaining after one half-life (125 days) is 250 shells. At two sites on the Texas coast, the longest half-lives did not exceed one year for any of the 13 species which produced input pulses during the study period. Little net addition to the death assemblage could be detected in spite of the transitory addition of hundreds of shells as input pulses. These rapid decay rates show that death assemblages do not accumulate at the rate at which organisms die. Some species, such as the infaunal bivalve Tagelus plebeius, did not decay measurably. We predict that decay rates drop substantially with depth in the sediment so that individuals which die at depth or are rapidly reworked below the sediment surface have a greater chance of preservation. The final composition of death assemblages is probably little related to the actual numerical input from the potentially preservable component of the living community.
The contribution of fish studies to palaeoecology generally takes the form of (1) inference from analogies in modern fish faunas and (2) fish taphonomy—the pattern of death and dispersal of bones. (1) Modern fish faunas and associated organisms provide taxonomic, ecological, or functional analogues for interpretation of ancient limiting factors and behaviors. These inferences presume taxonomic conservatism. They also presume functional relationships between morphological form and feeding mode or habitat. They become weak with increased geologic age or phyletic distance between ancient subject and modern anaogue. (2) Fish taphonomy may contribute information about limnology, community composition, life history, mortality, depositional environment, and preservation. Taphonomic reconstruction of ecology and preservation depends on the applicability of analogous processes in modern ecology and l limnology.In aquatic taphonomy, temperature is the most important factor in determining the fate of a carcass. Above about 16°C (depending on depth and pressure), most carcasses are made buoyant by bacterial decay gases and are transported to the surface where they may decay further and fall piecemeal into deepwater environments, or drift to beach environments where wave energy disarticulates, abrades, and scatters the bones. Below about 16°C, most carcasses remain on the bottom until buried; they may be disturbed by scavengers, depending on oxygen concentration in the hypolimnion.
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