Refugee communities of Carbonicola

Hardy, Peter G. & Broadhurst, Frederick M. 1978 04 IS: Refugee communities ofCarbonirola
Sparse elongate forms of the non-marine bivalve Carbonirola are associated with an abundance of trace fossils comprising resting traces (Cubichnia) referable to Lockeia , trails (Repichnia) and escape shafts (Fugichnia), all in arenaceous sediments of the Upper Carboniferous. Associated organic-rich argillaceous sediments contain the well-known, abundant and highly variable Carbonirola body fossil faunas. The latter we interpret (in common with other workers) as the remains of shells preserved in what was the typical life environment (characterized by muddy sediments and slow rates of sedimentation). The elongate shells associated with escape shafts we interpret as the only form of Carbonicola capable of escape upwards from burial by rapid sedimentation. For such fugitives from preexisting 'established communities' we propose the term 'refugee community'.     

A Late Holocene Pollen and Charcoal Record from La Selva Biological Station, Costa Rica

Pollen and charcoal analysis of a 5.9-m-long sediment profile from a swamp on an alluvial terrace on the edge of La Selva biological station, Costa Rica (10°26'23" N, 84°00'24" W, 36 m asl), documents three millennia of human and natural disturbance within a lowland tropical rain forest. The record indicates that the highly diverse rain forest that presently surrounds the Cantarrana swamp regrew following forest clearing and maize agriculture that ended only a few centuries ago. The first maize pollen appears in sediments deposited ∼1070 calendar-year BP. Older sediments below the 'maize zone' contain macroscopic charcoal, abundant microscopic charcoal, and possible pollen indicators of forest clearance, perhaps signaling local cultivation of root crops that left no pollen in the sediments. Interpretation of local archaeology indicates that La Selva reserve may have been most heavily populated during the El Bosque and La Selva regional archaeological phases from 2250–950 yr BP. However, the distribution of maize pollen in the sediments is clear evidence that the reserve was also occupied during the later La Cabaña phase (950–400 yr BP), from which few artifacts have yet surfaced. Natural forest disturbance from treefalls and stream dynamics, and hydrological shifts associated with late-Holocene climate variability, form a backdrop to the human land-use history preserved in the Cantarrana sediment profile.     

Étude des macro-, méso- et micro-charbons du site épigravettien de Mezhyrich (Ukraine) : données taphonomiques et anthracologiques

This paper is the state of the art of charcoal signal studies (macro-, meso- and micro-charcoal) that have been carried out at the Epigravettian settlement of Mezhyrich. This work took part of the French ANR project “Mammouths”. Charcoal signals have been found in both natural and archaeological (pits and activity areas) deposits that have been sampled during the 2007–2008 archaeological excavations. This study aims at discussing the natural versus anthropic causes of those charcoal signals. Microscopic charcoal have been observed and quantified from loess sediments; they are probably the consequence of regional fire regimes. Charcoal signals found in archaeological layers would be mainly caused by human activities. The major charcoal signal is observed within the microscopic part of the archaeological sediments and thereby underlines the intensity of taphonomic processes. The identification of wood charcoal shows that birch and willow were located along the riverbanks, which provides further discussion of prehistoric fuel management in Pleniglacial context.     

Evidence of recurrent wildfire from the Permian coal deposits of India: Petrographic,scanning electron microscopic and palynological analyses of fossil charcoal

In India hitherto fossil charcoal has been reported from Kashmir, Damodar Basin, and Mahanadi Basin. This work documents recurrent Cisuralian wildfire based on the occurrence of fossil charcoal from India. The authors used petrographical, palynological and SEM studies to analyze the anatomy of charred wood fragments and temperature of their formation. The fossil charcoal has been retrieved from the Cisuralian coal bearing subsurface sediments of Lower Barakar Formation (Artinskian) from Auranga Coalfield of Damodar Basin. Evidences of recurrent wildfire have been observed by the occurrence of charcoal at four levels of clastic sediments in Borehole 2N. The charcoal was subjected to petrographical, palynological and SEM studies to understand the burning temperature, fuel source and plant anatomy respectively. Petrographic studies indicate high frequency of semifusinite vis-à-vis fusinite having reflectance values ranging from 2.87% to 4.1%. The majority of the fusinite reflectance values fall in the range of 2.9%–3.5% indicating the temperature of formation of these charcoals to be at approximately 500°C. High temperature is also indicated by homogenization of cell walls under SEM. They also reveal fungal infestation and degradation in all charcoal samples. Moderate to high degree of preservation of charcoal indicates lesser transportation/post-depositional degradation suggesting a hypo-autochthonous nature. The botanical affinity of recovered spores and pollen suggest that the hinterland was dominated by gymnosperms and sub-dominated by filicopsids, sphenopsids, and lycopsids which contributed to the fuel source.     

Methodological and practical aspects of the presentation and interpretation of microscopic charcoal data from lake sediments

Analysis of microscopic charcoal particles is a useful part of palaeoecological research and is mostly used in conjunction with pollen analysis. However, there is considerable variation in the methodology of charcoal analyses. This paper considers various methods for the analysis of microscopic charcoal and the presentation of charcoal data in the context of a study of the upper sediments of two lakes Estonia. The results are evaluated by comparing both the pollen and charcoal data with documentary evidence of forest fires over the past 60 years. Indications of fires both varying in extent and at different distances from the lakes are evaluated in both the pollen and charcoal diagrams. The results suggest that the total area curve for charcoal particles per unit mass of sediment dry matter (cm² g⁻¹) provides the best indicator of forest fires. Fires in the study area are reflected differently in the charcoal and pollen curves. It is suggested that the charcoal data have the potential to indicate disturbance at a greater distance from the coring site than indicated by the pollen data. Received February 5, 2002 / Accepted August 14, 2002     

Syndesmorion gen. nov.—A coenobial alga of Chlorococcalean affinity from the continental Permian-Triassic deposits of Dalongkou section, Xinjiang Province, China

Abundant algal remains, represented by at least five different types of coenobia, have been recovered from continental sediments of the upper lower Guodikeng Formation, from the North Limb of Dalongkou Anticline, Xinjiang Province, China. Some of these forms have been recognized in assemblages from lower Triassic sediments of Poland, Germany, and Australia. The preservation of the Chinese material shows that all these planar, coenobial morphotypes belong to one natural species within the Order Chlorococcales. They are assigned to the genus Syndesmorion gen. nov., type species S. stellatum (Fija?kowska) comb. nov. Algal remains, described as Bijugum by Wood and Turnau in 2001, from the Devonian of Poland are planer and have comparable elongate coenobia but lack star-shaped and reticulate coenobia of Syndesmorion gen. nov. and so the genera are maintained separately.     

Novel Application of Confocal Laser Scanning Microscopy and 3D Volume Rendering toward Improving the Resolution of the Fossil Record of Charcoal

Variations in the abundance of fossil charcoals between rocks and sediments are assumed to reflect changes in fire activity in Earth’s past. These variations in fire activity are often considered to be in response to environmental, ecological or climatic changes. The role that fire plays in feedbacks to such changes is becoming increasingly important to understand and highlights the need to create robust estimates of variations in fossil charcoal abundance. The majority of charcoal based fire reconstructions quantify the abundance of charcoal particles and do not consider the changes in the morphology of the individual particles that may have occurred due to fragmentation as part of their transport history. We have developed a novel application of confocal laser scanning microscopy coupled to image processing that enables the 3-dimensional reconstruction of individual charcoal particles. This method is able to measure the volume of both microfossil and mesofossil charcoal particles and allows the abundance of charcoal in a sample to be expressed as total volume of charcoal. The method further measures particle surface area and shape allowing both relationships between different size and shape metrics to be analysed and full consideration of variations in particle size and size sorting between different samples to be studied. We believe application of this new imaging approach could allow significant improvement in our ability to estimate variations in past fire activity using fossil charcoals.     

Heterochrony in fringeheads (Neoclinus) and amplification of an extraordinary aggressive display in the Sarcastic Fringehead (Teleostei: Blenniiformes)

The Sarcastic Fringehead (Neoclinus blanchardi, Teleostei) exhibits an extreme version of a common aggressive display, the “gaping display,” in which an open mouth is presented toward an opponent. Males of this species have extremely long jaws that extend posteriorly well past the posterior margin of the head and are flared laterally during the gaping display. In this study, we explored morphological traits related to this extraordinary display in this and related species of blennies. Morphological modifications include enlargement of the buccopalatal membrane, elongation of the maxilla via an uncalcified posterior extension, and evolution of a novel hinge between the anterior maxilla and lacrimal bones permitting lateral movement of the upper jaw. Geometric morphometry using the truss network system, thin‐plate spline, and PCA of three closely related species of Neoclinus indicate that the elongate maxilla of N. blanchardi most likely evolved via acceleration (faster growth compared to outgroups) and hypermorphosis (continued growth to a larger body size), both forms of peramorphic heterochrony. Coloration and fluorescence of the buccopalatal membrane may also serve to amplify the extraordinary gaping display of the Sarcastic Fringehead.     

Pre-industrial particulate emissions and carbon sequestration from biomass burning in North America

Spatial trends in pre-industrial biomass burning emissions for eastern North America were reconstructed from sediment charcoal data. Petrographic thin sections were prepared from varved lake sediments along a transect of sites extending from NW Minnesota eastward to NE Maine. Results showed an exponential decline in charcoal abundance with distance east from the prairie/forest border. This result quantifies burning along the broad climate/vegetation gradient from xeric woodland to mesic eastern deciduous forest. Post-settlement charcoal accumulation showed no such geographic pattern, varying from site-to-site, likely reflecting local variability in land use and combustion sources. Results suggest the total emissions of large (> 10 m diameter) charcoal particles decreased by a factor of three during the twentieth century.     

Pre-Quaternary wood decay ‘caught in the act’ by fire – examples of plant-microbe-interactions preserved in charcoal from clastic sediments

The fossil record contains abundant evidence for the activity of microorganisms in the form of characteristic decay structures within fossil plant remains. Despite an abundance of charcoal in many sedimentary environments, there is little published evidence of such decay structures within charcoal from pre-Quaternary clastic deposits. The present contribution presents some examples of pre-Quaternary charcoal from clastic sediments which exhibit pre-charring decay structures, stratigraphically reaching from the Permian up to the Oligocene. Examples include specimens affected by the principle types of wood rot known from modern ecosystems (i.e. brown-rot, white rot and soft-rot) as well as a peculiar decay pattern resembling an atypical type of white-rot, which is only rarely known from modern wood. Theoretically there are different, so far hypothetical, scenarios which could be used to explain the scarcity of published reports on such material. Besides taphonomical biases directly influencing the sedimentary record of charcoal towards material not affected by microbial decay, it is conceivable that the lack of reports of such material from pre-Quaternary clastic deposits represents a, maybe unintentional, bias introduced by scientists working on pre-Quaternary charcoal.     

The phosphorus status of sediments in a hypertrophic impoundment (Hartbeespoort Dam): implications for eutrophication management

The phosphorus status and distribution of sediments in a hypertrophic water supply reservoir (Hartbeespoort Dam) were investigated, with a view to assessing the role of sediments in counteracting the effects of reduced external phosphorus loading as a restoration measure. In comparison with similar water bodies in South Africa, the sediments in Hartbeespoort Dam contained high levels of both total and potentially mobile phosphorus. The potentially mobile fraction constituted about 60% of the total phosphorus content of the sediments, compared with about 11% in other reservoirs. The excessive eutrophication of Hartbeespoort Dam is clearly reflected in the phosphorus status of the sediments. Sediment distribution in the impoundment was found to be extremely heterogeneous, due to the combined influences of morphometry, hydrology and an imbalance in the nutrient loads entering via rivers at remote points in the water body. It is concluded that sufficient mobile phosphorus has accumulated in the sediments to prolong the response time of the impoundment to phosphorus load reductions. Since phosphorus release from sediments is dependent on dynamic processes not addressed in this study, the extent of the delays in trophic response to load reduction cannot be estimated.     

MORPHOLOGY AND DISTRIBUTION OF COLLETERS AND CRYSTALS IN RELATION TO THE TAXONOMY AND BACTERIAL LEAF NODULE SYMBIOSIS OF PSYCHOTRIA (RUBIACEAE)

Earlier investigators established that a finger-like colleter with elongate axial cells and a palisade epidermis is the standard type in the Rubiaceae. This type, with some variation, also prevails in Psychotria, based on a worldwide anatomical survey of vegetative buds from herbarium specimens of 296 species (about 50 % of total). It is virtually the only type found outside of continental Africa. Among African species, it is most common in subgenus Psychotria, with mostly nodule-free species. In subgenus Tetramerae, with only leaf-nodulated species, there is a strong tendency toward brushlike and dendroid colleters in which epidermal cells are extremely elongate and separated from each other. It is speculated that this change in colleter morphology associated with presence of nodule bacteria may be correlated with a change in secretion product more suitable for support of bacteria. Three morphological forms of crystal occur: raphides, styloids, clustered crystals. They may occur singly or in combination. Several patterns and trends were noted in crystal distribution that could be of taxonomic significance.     

Stromatolites and basin analysis: an example from the upper proterozoic of northwestern Canada

Stromatolites have been used for inter-basinal biostratigraphic correlation, rock-stratigraphic correlation within individual sedimentary basins and for palaeoecological studies of various kinds. In the northern part of Victoria Island stromatolites are abundant in the uppermost part of the Gelenelg Formation, which is the lowest unit of the upper Proterozoic Shaler Group. Measurable attributes of these stromatolites include elongate mounds, intermound channel fillings, ridges and grooves, elongate collumns and inclined columns. In a widespread stromatolitic bank that forms the upper part of the Glenelg Formation, and also in stromatolites of the overlying Reynolds Point Formation, several of these features show a preferred orientation in a northeasterly direction. Herringbone cross-beds in associated sandy oolitic limestones show a northeast—southwest bimodal-bipolar distribution that is probably related to tidal activity. This similarity of directional features suggests that the stromatolite orientations are also likely to have been tidally influenced. If each stromatolitic bank were deposited diachronously then the northeasterly preferred orientation may be explained as being due to tidal currents active at a migrating shoreline that trended in a northwest-southeast direction. Alternatively, if, in the absence of metazoan competitors, the stromatolite builders contemporaneously occupied a large part of the basin floor, their northeasterly orientation may reflect tidal currents parallel to the length of an elongate embayment of the Precambrian sea, analogous in many ways to the present-day Persian Gulf. Such an interpretation, involving parallelism between coastline and elongate stromatolites, would differ from those of most earlier reports, in which elongate stromatolites have generally been assumed to have been oriented normal to the ancient shoreline.     

The proterozoic and earliest cambrian trace fossil record; patterns, problems and perspectives

The increase in trace fossil diversity across the Neoproterozoic-Cambrianboundary often is presented in terms of tabulations of ichnogenera.However, a clearer picture of the increase in diversity andcomplexity can be reached by combining trace fossils into broadgroups defined both on morphology and interpretation. This alsofocuses attention on looking for similarites between Neoproterozoicand Cambrian trace fossils. Siliciclastic sediments of the Neoproterozoicpreserve elongate tubular organisms and structures of probablealgal origin, many of which are very similar to trace fossils.Such enigmatic structures include Palaeopascichnus and Yelovichnus,previously thought to be trace fossils in the form of tightmeanders. A preliminary two or tripartite terminal Neoproterozoic tracefossil zonation can be be recognized. Possibly the earliesttrace fossils are short unbranched forms, probably younger thanabout 560 Ma. Typical Neoproterozoic trace fossils are unbranchedand essentially horizontal forms found associated with diverseassemblages of Ediacaran organisms. In sections younger thanabout 550 Ma a modest increase in trace fossil diversity occurs,including the appearance of rare three-dimensional burrow systems(treptichnids), and traces with a three-lobed lower surfaces.     

Dimorphism in methane seep-dwelling ecotypes of the largest known bacteria

We present evidence for a dimorphic life cycle in the vacuolate sulfide-oxidizing bacteria that appears to involve the attachment of a spherical Thiomargarita-like cell to the exteriors of invertebrate integuments and other benthic substrates at methane seeps. The attached cell elongates to produce a stalk-like form before budding off spherical daughter cells resembling free-living Thiomargarita that are abundant in surrounding sulfidic seep sediments. The relationship between the attached parent cell and free-living daughter cell is reminiscent of the dimorphic life modes of the prosthecate Alphaproteobacteria, but on a grand scale, with individual elongate cells reaching nearly a millimeter in length. Abundant growth of attached Thiomargarita-like bacteria on the integuments of gastropods and other seep fauna provides not only a novel ecological niche for these giant bacteria, but also for animals that may benefit from epibiont colonization.     

Evidence for possible use of plant foods in Palaeolithic and Mesolithic diet from the site of Całowanie in the central part of the Polish Plain

Całowanie site, which supported hunter-gatherer populations from ca. 11 380±95 until 8270±100 B.P., is the major terminal Palaeolithic and early Mesolithic occupation complex of the North European Plain. The archaeological layers are intercalated with biogenic sediments. The remains of plants that probably served as food were recovered from terminal Palaeolithic and early Mesolithic layers. Most of the charred plant remains, apart from wood charcoal, derives from vegetative parenchyma which forms a major part of organs such as root and tuber. Two taxa have been identified on the basis of the anatomy of parenchymatous tissue, namely Sagittaria cf. sagittifolia and Polygonum sp. In addition, several charred seeds and fruits were recovered. This is the first evidence for the probable use of plant foods, other than hazel nuts or water-chestnuts, in the diet of hunter-gatherers in the North European Plain during the Palaeolithic and Mesolithic.     

Larval and juvenile development of Tatia intermedia (Siluriformes: Auchenipteridae)

This study describes the morphology, morphometry and meristic characters of larval and juvenile Tatia intermedia collected in the middle Tocantins River and some of its tributaries. Six larvae of T. intermedia were examined and they have a moderately elongate body, head slightly dorso‐ventrally depressed with a convex snout, small and round eyes and a subterminal mouth. In five juvenile stages observed, the head and eye are relatively smaller than in the larval stage and the snout remains convex and mouth becomes terminal.     

The southern limit of the Mediterranean vegetation in the Sahara during the Holocene

Holocene records from the southern Sahara in Niger allow a reconstruction of the vegetation history and inform us about the former extension of the Mediterranean. Both pollen and charcoal analyses evidenced the direct contact of Sudanian and Saharan savannas during the middle Holocene at about 19°N, whereas at 20°N the transition from the Saharan savanna to the desert was found. In southwestern Libya (26°N) a combination of a Saharan desert vegetation and a semi‐desert Artemisia shrub on the plateaus demonstrated the contact with Mediterranean influenced formations. Regular ash and charcoal layers in middle‐Holocene sediments of the northern Niger prove an early interference of man with the vegetation development. One has to imagine that, in combination with the cattle‐keeping and the later metal production, man could have changed the former northern Sudanian vegetation into the present Sahelian savanna system from the middle Holocene on.     

Effects of zooplankton on sedimentation in pelagic ecosystems: Theory and test in two lakes of the Canadian shield

A simple heuristic theory based on conservation of matter and describing the fate of autotrophic production in pelagic ecosystems was developed to assist in conceptualizing how zooplankton affect sedimentation processes in lakes and oceans. The theory predicted that effects of zooplankton on the fraction of autotrophic incorporation that sediments (the export ratio) will be a function of factors related both to zooplankton digestion and egestion and to tendencies of particulate matter to sediment directly prior to mineralization. As a result, effects of zooplankton grazing on the export ratio were predicted to be site-dependent, a function of physical conditions and zooplankton communities characterizing an ecosystem. The theory was tested by monitoring autotrophic production of C, N, and P, sedimentation of C, N, and P, and zooplankton biomass in two lakes of the Canadian shield characterized by contrasting morphometry and food-web structure. In Lake 110, a small elongate lake protected from wind exposure, export ratios of C, N, and P declined strongly with zooplankton biomass. In contrast, in L240, a larger lake with considerably greater wind exposure, export ratios increased with zooplankton biomass. These results were consistent with predictions of our theory that effects of zooplankton on sedimentation processes will depend on the tendency of particulate matter to directly sediment relative to the tendency of egested materials to sediment. However, no significant differences in relationships between export ratios for C, N, and P and zooplankton biomass were found.