scholarly journals Modelling Deep Biospheres over Deep Geological Time; The Sediment-Hosted Deep Biosphere of the Nankai Trough

2020 ◽  
Author(s):  
Stephen Bowden
Keyword(s):  
Nankai Trough ◽  
Deep Biosphere ◽  
Geological Time

scholarly journals The Carbon-Isotope Record of the Sub-Seafloor Biosphere

Geosciences ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 507 ◽  
Author(s):  
Patrick Meister ◽  
Carolina Reyes
Keyword(s):  
Carbon Isotope ◽  
Carbon Isotopes ◽  
Isotope Fractionation ◽  
Dissolved Inorganic Carbon ◽  
Isotopic Signature ◽  
Enzymatic Reactions ◽  
Deep Biosphere ◽  
Geological Time ◽  
Isotopic Signatures ◽  
Carbon Isotope Fractionation

Sub-seafloor microbial environments exhibit large carbon-isotope fractionation effects as a result of microbial enzymatic reactions. Isotopically light, dissolved inorganic carbon (DIC) derived from organic carbon is commonly released into the interstitial water due to microbial dissimilatory processes prevailing in the sub-surface biosphere. Much stronger carbon-isotope fractionation occurs, however, during methanogenesis, whereby methane is depleted in 13C and, by mass balance, DIC is enriched in 13C, such that isotopic distributions are predominantly influenced by microbial metabolisms involving methane. Methane metabolisms are essentially mediated through a single enzymatic pathway in both Archaea and Bacteria, the Wood–Ljungdahl (WL) pathway, but it remains unclear where in the pathway carbon-isotope fractionation occurs. While it is generally assumed that fractionation arises from kinetic effects of enzymatic reactions, it has recently been suggested that partial carbon-isotope equilibration occurs within the pathway of anaerobic methane oxidation. Equilibrium fractionation might also occur during methanogenesis, as the isotopic difference between DIC and methane is commonly on the order of 75‰, which is near the thermodynamic equilibrium. The isotopic signature in DIC and methane highly varies in marine porewaters, reflecting the distribution of different microbial metabolisms contributing to DIC. If carbon isotopes are preserved in diagenetic carbonates, they may provide a powerful biosignature for the conditions in the deep biosphere, specifically in proximity to the sulphate–methane transition zone. Large variations in isotopic signatures in diagenetic archives have been found that document dramatic changes in sub-seafloor biosphere activity over geological time scales. We present a brief overview on carbon isotopes, including microbial fractionation mechanisms, transport effects, preservation in diagenetic carbonate archives, and their implications for the past sub-seafloor biosphere and its role in the global carbon cycle. We discuss open questions and future potentials of carbon isotopes as archives to trace the deep biosphere through time.

scholarly journals Oxidative sulfur cycling in the deep biosphere of the Nankai Trough, Japan

Geology ◽  
2010 ◽  
Vol 38 (9) ◽  
pp. 851-854 ◽  
Author(s):  
N. Riedinger ◽  
B. Brunner ◽  
M. J. Formolo ◽  
E. Solomon ◽  
S. Kasten ◽  
...  
Keyword(s):  
Nankai Trough ◽  
Sulfur Cycling ◽  
Deep Biosphere

Geological Time

1877 ◽  
Vol 3 (76supp) ◽  
pp. 1212-1212
Author(s):  
T. Mellard Reade
Keyword(s):  
Geological Time

Large-scale mapping of the catenas vegetation in Subarctic tundra

1995 ◽  
pp. 3-21
Author(s):  
S. S. Kholod
Keyword(s):  
Spatial Distribution ◽  
Vegetation Cover ◽  
Large Scale ◽  
Block Diagram ◽  
Abiotic Factors ◽  
Ecological Factors ◽  
Spatial Arrangement ◽  
Geological Time ◽  
Ecological Barriers ◽  
Functional Zones

One of the most difficult tasks in large-scale vegetation mapping is the clarification of mechanisms of the internal integration of vegetation cover territorial units. Traditional way of searching such mechanisms is the study of ecological factors controlling the space heterogeneity of vegetation cover. In essence, this is autecological analysis of vegetation. We propose another way of searching the mechanisms of territorial integration of vegetation. It is connected with intracoenotic interrelation, in particular, with the changing role of edificator synusium in a community along the altitudinal gradient. This way of searching is illustrated in the model-plot in subarctic tundra of Central Chukotka. Our further suggestion concerns the way of depicting these mechanisms on large-scale vegetation map. As a model object we chose the catena, that is the landscape formation including all geomorphjc positions of a slope, joint by the process of moving the material down the slope. The process of peneplanation of a mountain system for a long geological time favours to the levelling the lower (accumulative) parts of slopes. The colonization of these parts of the slope by the vegetation variants, corresponding to the lowest part of catena is the result of peneplanation. Vegetation of this part of catena makes a certain biogeocoenotic work which is the levelling of the small infralandscape limits and of the boundaries in vegetation cover. This process we name as the continualization on catena. In this process the variants of vegetation in the lower part of catena are being broken into separate synusiums. This is the process of decumbation of layers described by V. B. Sochava. Up to the slope the edificator power of the shrub synusiums sharply decreases. Moss and herb synusium have "to seek" the habitats similar to those under the shrub canopy. The competition between the synusium arises resulting in arrangement of a certain spatial assemblage of vegetation cover elements. In such assemblage the position of each element is determined by both biotic (interrelation with other coenotic elements) and abiotic (presence of appropriate habitats) factors. Taking into account the biogeocoenotic character of the process of continualization on catena we name such spatial assemblage an exolutionary-biogeocoenotic series. The space within each evolutionary-biogeocoenotic series is divided by ecological barriers into some functional zones. In each of the such zones the struggle between synusiums has its individual expression and direction. In the start zone of catena (extensive pediment) the interrelations of synusiums and layers control the mutual spatial arrangement of these elements at the largest extent. Here, as a rule, there predominate edificator synusiums of low and dwarfshrubs. In the first order limit zone (the bend of pediment to the above part of the slope) one-species herb and moss synusiums, oftenly substituting each other in similar habitats, get prevalence. In the zone of active colonization of slope (denudation slope) the coenotic factor has the least role in the spatial distribution of the vegetation cover elements. In particular, phytocoenotic interactions take place only within separate microcoenoses of herbs, mosses and lichens. In the zone of the attenuation of continualization process (the upper most parts of slope, crests) phytocoenotic interactions are almost absent and the spatial distribution of vegetation cover elements depends exclusively on the abiotic factors. The principal scheme of the distribution of vegetation cover elements and the disposition of functional zones on catena are shown on block-diagram (fig. 1).

EARTHTIME 2.0, ACCELERATING THE DEVELOPMENT AND APPLICATION OF INTEGRATED METHODOLOGIES FOR THE QUANTIFICATION OF GEOLOGICAL TIME

2017 ◽  
Author(s):  
Daniel Condon ◽  
◽  
Klaudia Kuiper ◽  
Leah E. Morgan ◽  
Paul R. Renne ◽  
...  
Keyword(s):  
Geological Time

THE NEOTOMA PALEOECOLOGY DATABASE: REPRESENTATIONS OF GEOLOGICAL TIME AND GEOCHRONOLOGICAL DATA HOLDINGS

2017 ◽  
Author(s):  
John W. Williams ◽  
◽  
Eric Grimm ◽  
Simon Goring ◽  
Brad S. Singer
Keyword(s):  
Geological Time ◽  
Geochronological Data
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