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Frank A Corsetti - One of the best experts on this subject based on the ideXlab platform.
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builders tenants and squatters the origins of genetic material in modern Stromatolites
Geobiology, 2021Co-Authors: Victoria A Petryshyn, John R Spear, Emily N Junkins, Blake W Stamps, Jake V Bailey, Bradley S Stevenson, Frank A CorsettiAbstract:Micro-organisms have long been implicated in the construction of Stromatolites. Yet, establishing a microbial role in modern Stromatolite growth via molecular analysis is not always straightforward because DNA in Stromatolites can have multiple origins. For example, the genomic material could represent the microbes responsible for the construction of the Stromatolite (i.e., "builders"), microbes that inhabited the structure after it was built (i.e., "tenants"), or microbes/organic matter that were passively incorporated after construction from the water column or later diagenetic fluids (i.e., "squatters"). Disentangling the role of micro-organisms in Stromatolite construction, already difficult in modern systems, becomes more difficult as organic signatures degrade, and their context is obscured. To evaluate our ability to accurately decipher the role of micro-organisms in Stromatolite formation in geologically recent settings, 16/18S SSU rRNA gene sequences were analyzed from three systems where the context of growth was well understood: (a) an actively growing Stromatolite from a silicic hot spring in Yellowstone National Park, Wyoming, where the construction of the structure is controlled by cyanobacteria; (b) a mixed carbonate and silica precipitate from Little Hot Creek, a hot spring in the Long Valley Caldera of California that has both abiogenic and biogenic components to accretion; and (c) a near-modern lacustrine carbonate Stromatolite from Walker Lake, Nevada that is likely abiogenic. In all cases, the largest percentage of recovered DNA sequences, especially when focused on the deeper portions of the structures, belonged to either the tenant or squatter communities, not the actual builders. Once removed from their environmental context, correct interpretation of biology's role in Stromatolite morphogenesis was difficult. Because high-throughput genomic analysis may easily lead to incorrect assumptions even in these modern and near-modern structures, caution must be exercised when interpreting micro-organismal involvement in the construction of accretionary structures throughout the rock record.
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neoarchean 2 7 ga lacustrine Stromatolite deposits in the hartbeesfontein basin ventersdorp supergroup south africa implications for oxygen oases
Precambrian Research, 2019Co-Authors: N J Beukes, Dylan T Wilmeth, Frank A Corsetti, Stanley M Awramik, Victoria A Petryshyn, Aaron J Celestian, John R SpearAbstract:Abstract The Hartbeesfontein Basin contains the most extensive deposits of Archean lacustrine Stromatolites on the Kaapvaal Craton, with stromatolitic facies occurring over ∼100 km 2 in beds up to 7 m thick. Stromatolitic dolostones and cherts both preserve evidence of microbial processes. Dolomitic Stromatolites have grumelous microspar textures between organic-rich laminae, suggestive of carbonate precipitation within microbial mats. Stromatolitic laminae within chert preserve detrital material beyond the angle of repose, indicating the trapping and binding of grains by microbial mats. Stromatolitic cherts also preserve fenestral textures and filamentous microfossils. Many fenestrae have rounded shapes surrounded by filamentous laminae and appear to have formed in situ within Stromatolite fabrics before lithification. Fenestrae within stromatolitic chert resemble “hourglass-associated fenestrae” noted from recent silica Stromatolites from Yellowstone National Park, and are interpreted to originate from gas bubbles forming within Stromatolite-building mats. The preservation of delicate structures in Hartbeesfontein stromatolitic chert (e.g., filamentous microfossils and gas-related fenestrae) implies rapid lithification of microbial mats, while the mm to cm scale of fenestrae indicate equally rapid rates of microbial gas production. Textural and mineralogical evidence associated with gas-related fenestrae support the presence of oxygenic photosynthesis, which in turn strengthens previous hypotheses on Archean lakes as potential oxygen oases before the Great Oxidation Event.
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grain trapping by filamentous cyanobacterial and algal mats implications for Stromatolite microfabrics through time
Geobiology, 2015Co-Authors: Carie M Frantz, Victoria A Petryshyn, Frank A CorsettiAbstract:Archean and Proterozoic Stromatolites are sparry or fine-grained and finely laminated; coarse-grained Stromatolites, such as many found in modern marine systems, do not appear until quite late in the fossil record. The cause of this textural change and its relevance to understanding the evolutionary history of Stromatolites is unclear. Cyanobacteria are typically considered the dominant Stromatolite builders through time, but studies demonstrating the trapping and binding abilities of cyanobacterial mats are limited. With this in mind, we conducted experiments to test the grain trapping and binding capabilities of filamentous cyanobacterial mats and trapping in larger filamentous algal mats in order to better understand grain size trends in Stromatolites. Mats were cut into squares, inclined in saltwater tanks at angles from 0 to 75° (approximating the angle of lamina in typical Stromatolites), and grains of various sizes (fine sand, coarse sand, and fine pebbles) were delivered to their surface. Trapping of grains by the cyanobacterial mats depended strongly on (i) how far filaments protruded from the sediment surface, (ii) grain size, and (iii) the mat's incline angle. The cyanobacterial mats were much more effective at trapping fine grains beyond the abiotic slide angle than larger grains. In addition, the cyanobacterial mats actively bound grains of all sizes over time. In contrast, the much larger algal mats trapped medium and coarse grains at all angles. Our experiments suggest that (i) the presence of detrital grains beyond the abiotic slide angle can be considered a biosignature in ancient Stromatolites where biogenicity is in question, and, (ii) where coarse grains are present within Stromatolite laminae at angles beyond the abiotic angle of slide (e.g., most modern marine Stromatolites), typical cyanobacterial-type mats are probably not solely responsible for the construction, giving insight into the evolution of Stromatolite microfabrics through time.
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dramatic local environmental change during the early eocene climatic optimum detected using high resolution chemical analyses of green river formation Stromatolites
Palaeogeography Palaeoclimatology Palaeoecology, 2014Co-Authors: Carie M Frantz, Victoria A Petryshyn, Pedro J Marenco, Aradhna K Tripati, William M Berelson, Frank A CorsettiAbstract:Abstract The Eocene Green River Formation represents a system of lakes that covered parts of what is now Wyoming, Colorado, and Utah, and captures the Early Eocene Climatic Optimum (EECO, 52–50 million years ago or Ma), the warmest period of the Cenozoic Era, and a period associated with very high levels of atmospheric CO2. Lakes, especially closed basin lakes, can respond dramatically to environmental change because of their sensitivity to precipitation and evaporation. In this study, Stromatolites from the Rife Bed of the Green River Formation are used as fine-scale records of terrestrial paleoenvironmental change during a global hothouse climate, and to investigate how the environmental dynamics within the lake system affected the growth of Stromatolites. The Stromatolites are composed of branching microdigitate columns laminated on the 10–100 μm scale. Laminae are grouped in cm-scale layers that alternate between calcite fan, micritic, and mixed microstructures. The fan layers are depleted in 18O, Na, and Mg/Ca. The micrite layers, in contrast, are comparatively enriched in 18O, Na, and Mg/Ca. The δ13C and δ18O are strongly positively correlated, suggesting the Stromatolites formed in a closed basin lake, consistent with the regional stratigraphy. Additionally, clumped isotope analyses provide the first quantitative values for water temperatures in lake water from the Green River Formation (~ 35 °C for micrite layers and ~ 28 °C for fan layers). Changes in δ18O and sodium ion concentration are likely related to periods of evaporation and recharge, and thus can be used to estimate lake volume change during Stromatolite growth. Two models, one using sodium ion concentrations in a conserved system, the other using Rayleigh fractionation and mixing equations to explain changes in oxygen isotopes, converge upon similar results for lake volume changes, revealing multiple episodes of meter-scale lake level rise and fall during the accretion of the ~ 30 cm thick Stromatolite. Because of the broad, flat bathymetry of the lake, such lake volume and depth changes would have been accompanied by shoreline shifts on the order of tens of kilometers while the Stromatolites were actively growing, challenging the view of a single Stromatolite paleoenvironment in the lake. Therefore, the fan microfabric, interpreted here as abiogenic in nature, formed in cooler waters when the lake was deeper, possibly below a thermocline. In contrast, the micrite microfabric, for which there is evidence of biogenicity, formed when the lake was shallow and warm. The alternation between biogenic and abiogenic microfabrics present in the Rife Bed Stromatolites is hypothesized to result from dramatic changes in lake level influencing the microbiology and chemistry of the waters in which the Stromatolites formed, indicating that Stromatolite growth can occur under disparate conditions and therefore does not necessarily represent a single facies.
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Stromatolite lamination frequency walker lake nevada implications for Stromatolites as biosignatures
Geology, 2012Co-Authors: Victoria A Petryshyn, Frank A Corsetti, William M Berelson, Will Beaumont, Steve P LundAbstract:Lamination in Stromatolites (considered some of the oldest fossils on Earth) is commonly interpreted to record the periodic response of a microbial community to daily, seasonal, or perhaps yearly environmental forcing, but the inability to date ancient Stromatolites precludes an understanding of the lamination formation processes. We use high-resolution 14C dating of Holocene Stromatolites from Walker Lake, Nevada (United States), to construct a record of lamination rate over the course of accretion. Laminae formed with a period of 5.6 ± 1.6 yr/lamination at the base of the structure, 1.6–2.8 ± 1.9 yr/lamination in the middle, and 4.5 ± 0.8 yr/lamination at the top of the laminated portion. The predominant 4−6 yr periodicity indicates that lamination formation is likely more closely related to regional climate forcing (e.g., El Nino–Southern Oscillation) versus the typical diurnal or seasonal changes in microbial mats traditionally assumed for most ancient Stromatolites. Thus, generalizations regarding the influence of microbial mats on Stromatolite lamination and the use of Stromatolites as biosignatures need careful consideration.
Victoria A Petryshyn - One of the best experts on this subject based on the ideXlab platform.
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builders tenants and squatters the origins of genetic material in modern Stromatolites
Geobiology, 2021Co-Authors: Victoria A Petryshyn, John R Spear, Emily N Junkins, Blake W Stamps, Jake V Bailey, Bradley S Stevenson, Frank A CorsettiAbstract:Micro-organisms have long been implicated in the construction of Stromatolites. Yet, establishing a microbial role in modern Stromatolite growth via molecular analysis is not always straightforward because DNA in Stromatolites can have multiple origins. For example, the genomic material could represent the microbes responsible for the construction of the Stromatolite (i.e., "builders"), microbes that inhabited the structure after it was built (i.e., "tenants"), or microbes/organic matter that were passively incorporated after construction from the water column or later diagenetic fluids (i.e., "squatters"). Disentangling the role of micro-organisms in Stromatolite construction, already difficult in modern systems, becomes more difficult as organic signatures degrade, and their context is obscured. To evaluate our ability to accurately decipher the role of micro-organisms in Stromatolite formation in geologically recent settings, 16/18S SSU rRNA gene sequences were analyzed from three systems where the context of growth was well understood: (a) an actively growing Stromatolite from a silicic hot spring in Yellowstone National Park, Wyoming, where the construction of the structure is controlled by cyanobacteria; (b) a mixed carbonate and silica precipitate from Little Hot Creek, a hot spring in the Long Valley Caldera of California that has both abiogenic and biogenic components to accretion; and (c) a near-modern lacustrine carbonate Stromatolite from Walker Lake, Nevada that is likely abiogenic. In all cases, the largest percentage of recovered DNA sequences, especially when focused on the deeper portions of the structures, belonged to either the tenant or squatter communities, not the actual builders. Once removed from their environmental context, correct interpretation of biology's role in Stromatolite morphogenesis was difficult. Because high-throughput genomic analysis may easily lead to incorrect assumptions even in these modern and near-modern structures, caution must be exercised when interpreting micro-organismal involvement in the construction of accretionary structures throughout the rock record.
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neoarchean 2 7 ga lacustrine Stromatolite deposits in the hartbeesfontein basin ventersdorp supergroup south africa implications for oxygen oases
Precambrian Research, 2019Co-Authors: N J Beukes, Dylan T Wilmeth, Frank A Corsetti, Stanley M Awramik, Victoria A Petryshyn, Aaron J Celestian, John R SpearAbstract:Abstract The Hartbeesfontein Basin contains the most extensive deposits of Archean lacustrine Stromatolites on the Kaapvaal Craton, with stromatolitic facies occurring over ∼100 km 2 in beds up to 7 m thick. Stromatolitic dolostones and cherts both preserve evidence of microbial processes. Dolomitic Stromatolites have grumelous microspar textures between organic-rich laminae, suggestive of carbonate precipitation within microbial mats. Stromatolitic laminae within chert preserve detrital material beyond the angle of repose, indicating the trapping and binding of grains by microbial mats. Stromatolitic cherts also preserve fenestral textures and filamentous microfossils. Many fenestrae have rounded shapes surrounded by filamentous laminae and appear to have formed in situ within Stromatolite fabrics before lithification. Fenestrae within stromatolitic chert resemble “hourglass-associated fenestrae” noted from recent silica Stromatolites from Yellowstone National Park, and are interpreted to originate from gas bubbles forming within Stromatolite-building mats. The preservation of delicate structures in Hartbeesfontein stromatolitic chert (e.g., filamentous microfossils and gas-related fenestrae) implies rapid lithification of microbial mats, while the mm to cm scale of fenestrae indicate equally rapid rates of microbial gas production. Textural and mineralogical evidence associated with gas-related fenestrae support the presence of oxygenic photosynthesis, which in turn strengthens previous hypotheses on Archean lakes as potential oxygen oases before the Great Oxidation Event.
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grain trapping by filamentous cyanobacterial and algal mats implications for Stromatolite microfabrics through time
Geobiology, 2015Co-Authors: Carie M Frantz, Victoria A Petryshyn, Frank A CorsettiAbstract:Archean and Proterozoic Stromatolites are sparry or fine-grained and finely laminated; coarse-grained Stromatolites, such as many found in modern marine systems, do not appear until quite late in the fossil record. The cause of this textural change and its relevance to understanding the evolutionary history of Stromatolites is unclear. Cyanobacteria are typically considered the dominant Stromatolite builders through time, but studies demonstrating the trapping and binding abilities of cyanobacterial mats are limited. With this in mind, we conducted experiments to test the grain trapping and binding capabilities of filamentous cyanobacterial mats and trapping in larger filamentous algal mats in order to better understand grain size trends in Stromatolites. Mats were cut into squares, inclined in saltwater tanks at angles from 0 to 75° (approximating the angle of lamina in typical Stromatolites), and grains of various sizes (fine sand, coarse sand, and fine pebbles) were delivered to their surface. Trapping of grains by the cyanobacterial mats depended strongly on (i) how far filaments protruded from the sediment surface, (ii) grain size, and (iii) the mat's incline angle. The cyanobacterial mats were much more effective at trapping fine grains beyond the abiotic slide angle than larger grains. In addition, the cyanobacterial mats actively bound grains of all sizes over time. In contrast, the much larger algal mats trapped medium and coarse grains at all angles. Our experiments suggest that (i) the presence of detrital grains beyond the abiotic slide angle can be considered a biosignature in ancient Stromatolites where biogenicity is in question, and, (ii) where coarse grains are present within Stromatolite laminae at angles beyond the abiotic angle of slide (e.g., most modern marine Stromatolites), typical cyanobacterial-type mats are probably not solely responsible for the construction, giving insight into the evolution of Stromatolite microfabrics through time.
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dramatic local environmental change during the early eocene climatic optimum detected using high resolution chemical analyses of green river formation Stromatolites
Palaeogeography Palaeoclimatology Palaeoecology, 2014Co-Authors: Carie M Frantz, Victoria A Petryshyn, Pedro J Marenco, Aradhna K Tripati, William M Berelson, Frank A CorsettiAbstract:Abstract The Eocene Green River Formation represents a system of lakes that covered parts of what is now Wyoming, Colorado, and Utah, and captures the Early Eocene Climatic Optimum (EECO, 52–50 million years ago or Ma), the warmest period of the Cenozoic Era, and a period associated with very high levels of atmospheric CO2. Lakes, especially closed basin lakes, can respond dramatically to environmental change because of their sensitivity to precipitation and evaporation. In this study, Stromatolites from the Rife Bed of the Green River Formation are used as fine-scale records of terrestrial paleoenvironmental change during a global hothouse climate, and to investigate how the environmental dynamics within the lake system affected the growth of Stromatolites. The Stromatolites are composed of branching microdigitate columns laminated on the 10–100 μm scale. Laminae are grouped in cm-scale layers that alternate between calcite fan, micritic, and mixed microstructures. The fan layers are depleted in 18O, Na, and Mg/Ca. The micrite layers, in contrast, are comparatively enriched in 18O, Na, and Mg/Ca. The δ13C and δ18O are strongly positively correlated, suggesting the Stromatolites formed in a closed basin lake, consistent with the regional stratigraphy. Additionally, clumped isotope analyses provide the first quantitative values for water temperatures in lake water from the Green River Formation (~ 35 °C for micrite layers and ~ 28 °C for fan layers). Changes in δ18O and sodium ion concentration are likely related to periods of evaporation and recharge, and thus can be used to estimate lake volume change during Stromatolite growth. Two models, one using sodium ion concentrations in a conserved system, the other using Rayleigh fractionation and mixing equations to explain changes in oxygen isotopes, converge upon similar results for lake volume changes, revealing multiple episodes of meter-scale lake level rise and fall during the accretion of the ~ 30 cm thick Stromatolite. Because of the broad, flat bathymetry of the lake, such lake volume and depth changes would have been accompanied by shoreline shifts on the order of tens of kilometers while the Stromatolites were actively growing, challenging the view of a single Stromatolite paleoenvironment in the lake. Therefore, the fan microfabric, interpreted here as abiogenic in nature, formed in cooler waters when the lake was deeper, possibly below a thermocline. In contrast, the micrite microfabric, for which there is evidence of biogenicity, formed when the lake was shallow and warm. The alternation between biogenic and abiogenic microfabrics present in the Rife Bed Stromatolites is hypothesized to result from dramatic changes in lake level influencing the microbiology and chemistry of the waters in which the Stromatolites formed, indicating that Stromatolite growth can occur under disparate conditions and therefore does not necessarily represent a single facies.
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Stromatolite lamination frequency walker lake nevada implications for Stromatolites as biosignatures
Geology, 2012Co-Authors: Victoria A Petryshyn, Frank A Corsetti, William M Berelson, Will Beaumont, Steve P LundAbstract:Lamination in Stromatolites (considered some of the oldest fossils on Earth) is commonly interpreted to record the periodic response of a microbial community to daily, seasonal, or perhaps yearly environmental forcing, but the inability to date ancient Stromatolites precludes an understanding of the lamination formation processes. We use high-resolution 14C dating of Holocene Stromatolites from Walker Lake, Nevada (United States), to construct a record of lamination rate over the course of accretion. Laminae formed with a period of 5.6 ± 1.6 yr/lamination at the base of the structure, 1.6–2.8 ± 1.9 yr/lamination in the middle, and 4.5 ± 0.8 yr/lamination at the top of the laminated portion. The predominant 4−6 yr periodicity indicates that lamination formation is likely more closely related to regional climate forcing (e.g., El Nino–Southern Oscillation) versus the typical diurnal or seasonal changes in microbial mats traditionally assumed for most ancient Stromatolites. Thus, generalizations regarding the influence of microbial mats on Stromatolite lamination and the use of Stromatolites as biosignatures need careful consideration.
Carie M Frantz - One of the best experts on this subject based on the ideXlab platform.
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grain trapping by filamentous cyanobacterial and algal mats implications for Stromatolite microfabrics through time
Geobiology, 2015Co-Authors: Carie M Frantz, Victoria A Petryshyn, Frank A CorsettiAbstract:Archean and Proterozoic Stromatolites are sparry or fine-grained and finely laminated; coarse-grained Stromatolites, such as many found in modern marine systems, do not appear until quite late in the fossil record. The cause of this textural change and its relevance to understanding the evolutionary history of Stromatolites is unclear. Cyanobacteria are typically considered the dominant Stromatolite builders through time, but studies demonstrating the trapping and binding abilities of cyanobacterial mats are limited. With this in mind, we conducted experiments to test the grain trapping and binding capabilities of filamentous cyanobacterial mats and trapping in larger filamentous algal mats in order to better understand grain size trends in Stromatolites. Mats were cut into squares, inclined in saltwater tanks at angles from 0 to 75° (approximating the angle of lamina in typical Stromatolites), and grains of various sizes (fine sand, coarse sand, and fine pebbles) were delivered to their surface. Trapping of grains by the cyanobacterial mats depended strongly on (i) how far filaments protruded from the sediment surface, (ii) grain size, and (iii) the mat's incline angle. The cyanobacterial mats were much more effective at trapping fine grains beyond the abiotic slide angle than larger grains. In addition, the cyanobacterial mats actively bound grains of all sizes over time. In contrast, the much larger algal mats trapped medium and coarse grains at all angles. Our experiments suggest that (i) the presence of detrital grains beyond the abiotic slide angle can be considered a biosignature in ancient Stromatolites where biogenicity is in question, and, (ii) where coarse grains are present within Stromatolite laminae at angles beyond the abiotic angle of slide (e.g., most modern marine Stromatolites), typical cyanobacterial-type mats are probably not solely responsible for the construction, giving insight into the evolution of Stromatolite microfabrics through time.
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dramatic local environmental change during the early eocene climatic optimum detected using high resolution chemical analyses of green river formation Stromatolites
Palaeogeography Palaeoclimatology Palaeoecology, 2014Co-Authors: Carie M Frantz, Victoria A Petryshyn, Pedro J Marenco, Aradhna K Tripati, William M Berelson, Frank A CorsettiAbstract:Abstract The Eocene Green River Formation represents a system of lakes that covered parts of what is now Wyoming, Colorado, and Utah, and captures the Early Eocene Climatic Optimum (EECO, 52–50 million years ago or Ma), the warmest period of the Cenozoic Era, and a period associated with very high levels of atmospheric CO2. Lakes, especially closed basin lakes, can respond dramatically to environmental change because of their sensitivity to precipitation and evaporation. In this study, Stromatolites from the Rife Bed of the Green River Formation are used as fine-scale records of terrestrial paleoenvironmental change during a global hothouse climate, and to investigate how the environmental dynamics within the lake system affected the growth of Stromatolites. The Stromatolites are composed of branching microdigitate columns laminated on the 10–100 μm scale. Laminae are grouped in cm-scale layers that alternate between calcite fan, micritic, and mixed microstructures. The fan layers are depleted in 18O, Na, and Mg/Ca. The micrite layers, in contrast, are comparatively enriched in 18O, Na, and Mg/Ca. The δ13C and δ18O are strongly positively correlated, suggesting the Stromatolites formed in a closed basin lake, consistent with the regional stratigraphy. Additionally, clumped isotope analyses provide the first quantitative values for water temperatures in lake water from the Green River Formation (~ 35 °C for micrite layers and ~ 28 °C for fan layers). Changes in δ18O and sodium ion concentration are likely related to periods of evaporation and recharge, and thus can be used to estimate lake volume change during Stromatolite growth. Two models, one using sodium ion concentrations in a conserved system, the other using Rayleigh fractionation and mixing equations to explain changes in oxygen isotopes, converge upon similar results for lake volume changes, revealing multiple episodes of meter-scale lake level rise and fall during the accretion of the ~ 30 cm thick Stromatolite. Because of the broad, flat bathymetry of the lake, such lake volume and depth changes would have been accompanied by shoreline shifts on the order of tens of kilometers while the Stromatolites were actively growing, challenging the view of a single Stromatolite paleoenvironment in the lake. Therefore, the fan microfabric, interpreted here as abiogenic in nature, formed in cooler waters when the lake was deeper, possibly below a thermocline. In contrast, the micrite microfabric, for which there is evidence of biogenicity, formed when the lake was shallow and warm. The alternation between biogenic and abiogenic microfabrics present in the Rife Bed Stromatolites is hypothesized to result from dramatic changes in lake level influencing the microbiology and chemistry of the waters in which the Stromatolites formed, indicating that Stromatolite growth can occur under disparate conditions and therefore does not necessarily represent a single facies.
Pamela R Reid - One of the best experts on this subject based on the ideXlab platform.
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Stromatolite provinces of hamelin pool physiographic controls on Stromatolites and associated lithofacies
Journal of Sedimentary Research, 2019Co-Authors: Miriam S Andres, Pamela R Reid, Erica P Suosaari, Amanda M Oehlert, Phillip E Playford, Carl K Steffensen, Gregory V Suosaari, Gary R Milano, Gregor P EberliAbstract:Recent studies recognized distinct Stromatolite provinces in Hamelin Pool, Western Australia, each with morphologically distinct Stromatolite structures paired with characteristic shelf physiography. In the present paper, we couple detailed lithofacies mapping with Hamelin Pool bathymetry and consider physiography as a control of sedimentation processes, including Stromatolite development. Bathymetric transects, derived from a high-resolution bathymetry map with depths from 0 to 11 meters, allow calculation of slope gradients in the provinces. As in other settings, bathymetry is linked to energy regimes, which in turn appear to be coupled with variations in Stromatolite morphologies and associated lithofacies as follows: (1) low-gradient ramps with low-energy settings are associated with sheet mats and elongate-clustered Stromatolites that exhibit regular spatial patterns, possibly indicative of self-organization; (2) low gradients coupled with high-energy settings resulting from strong winds result in seif Stromatolites with pronounced directional bands; (3) medium to steep gradients coupled with medium to high energy are associated with individual and merged Stromatolites, often with thin basal necks; (4) headlands and promontories where the topography deflects currents are associated with elongate-nested Stromatolites; and (5) medium- to high-energy slopes typically found at promontory edges and shelf margins are dominated by blocky pavement. Observations linking Stromatolite morphology to physiography in a modern microbial system provide insight into the long-lived debate about biology versus environment in controlling Stromatolite morphology. When physiography leads to a high-energy regime, environmental controls are the main factor determining Stromatolite morphology. In contrast, when physiography promotes a low-energy environment, the response of biological communities becomes the main driver of macroscale Stromatolite morphology.
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characterization of the Stromatolite microbiome from little darby island the bahamas using predictive and whole shotgun metagenomic analysis
Environmental Microbiology, 2016Co-Authors: Giorgio Casaburi, Pamela R Reid, Alexandrea A Duscher, Jamie S FosterAbstract:Modern Stromatolites represent ideal ecosystems to understand the biological processes required for the precipitation of carbonate due to their long evolutionary history and occurrence in a wide range of habitats. However, most of the prior molecular work on Stromatolites has focused on understanding the taxonomic complexity and not fully elucidating the functional capabilities of these systems. Here, we begin to characterize the microbiome associated with Stromatolites of Little Darby Island, The Bahamas using predictive metagenomics of the 16S rRNA gene coupled with direct whole shotgun sequencing. The metagenomic analysis of the Little Darby Stromatolites revealed many shared taxa and core pathways associated with biologically induced carbonate precipitation, suggesting functional convergence within Bahamian Stromatolites. A comparison of the Little Darby Stromatolites with other lithifying microbial ecosystems also revealed that although factors, such as geographic location and salinity, do drive some differences within the population, there are extensive similarities within the microbial populations. These results suggest that for Stromatolite formation, 'who' is in the community is not as critical as metabolic activities and environmental interactions. Together, these analyses help improve our understanding of the similarities among lithifying ecosystems and provide an important first step in characterizing the shared microbiome of modern Stromatolites.
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light dependant biostabilisation of sediments by Stromatolite assemblages
PLOS ONE, 2008Co-Authors: David M Paterson, Miriam S Andres, Pieter T Visscher, Alan W Decho, John F Stolz, Rebecca J Aspden, Mireille Consalvey, Pamela R ReidAbstract:For the first time we have investigated the natural ecosystem engineering capacity of stromatolitic microbial assemblages. Stromatolites are laminated sedimentary structures formed by microbial activity and are considered to have dominated the shallows of the Precambrian oceans. Their fossilised remains are the most ancient unambiguous record of early life on earth. Stromatolites can therefore be considered as the first recognisable ecosystems on the planet. However, while many discussions have taken place over their structure and form, we have very little information on their functional ecology and how such assemblages persisted despite strong eternal forcing from wind and waves. The capture and binding of sediment is clearly a critical feature for the formation and persistence of Stromatolite assemblages. Here, we investigated the ecosystem engineering capacity of stromatolitic microbial assemblages with respect to their ability to stabilise sediment using material from one of the few remaining living Stromatolite systems (Highborne Cay, Bahamas). It was shown that the most effective assemblages could produce a rapid (12–24 h) and significant increase in sediment stability that continued in a linear fashion over the period of the experimentation (228 h). Importantly, it was also found that light was required for the assemblages to produce this stabilisation effect and that removal of assemblage into darkness could lead to a partial reversal of the stabilisation. This was attributed to the breakdown of extracellular polymeric substances under anaerobic conditions. These data were supported by microelectrode profiling of oxygen and calcium. The structure of the assemblages as they formed was visualised by low-temperature scanning electron microscopy and confocal laser microscopy. These results have implications for the understanding of early Stromatolite development and highlight the potential importance of the evolution of photosynthesis in the mat forming process. The evolution of photosynthesis may have provided an important advance for the niche construction activity of microbial systems and the formation and persistence of the Stromatolites which came to dominate shallow coastal environments for 80% of the biotic history of the earth.
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importance of light and oxygen for photochemical reactivation in photosynthetic Stromatolite communities after natural sand burial
Marine Ecology Progress Series, 2007Co-Authors: R G Perkins, Jacco C Kromkamp, Pamela R ReidAbstract:Modern Stromatolites at Highborne Cay, Exuma, Bahamas are formed in a high energy environment, where turbulent mixing of the water column supplies the sand particles that are trapped and bound by microbial phototrophs. The photosynthetic communities consist of cyanobacteria within the surface fabric of the Stromatolite, and surface eukaryotic microalgae (e.g. diatoms and chlorophytes). Due to the turbulent environment, Stromatolites are often buried for periods of weeks or months as a result of sand wave movements. We investigated the tolerance of subsets of the photosynthetic communities in Stromatolites to natural burial processes. Variable chlorophyll fluorescence was used to monitor PSII quantum efficiency and fluorescence kinetics during and after artificial and natural in situ burial. Excavated samples with an intact cyanobacterial community, but lacking surface microalgae, reactivated their quantum efficiency when exposed to both low light and oxygen. Reactivation, indicated by an increase in photochemical efficiency (ΔF/Fm), occurred after 7 to 9 d and 14 to 16 d of natural burial, although reactivation was slower with longer burial. Changes in fluorescence yields indicated that probable state transitions occurred, and we suggest that some form of oxygen dependent process(es) and light were in part responsible for the re-establishment of photochemistry. These processes effectively ‘kick start’ electron transport, and hence protect against photodamage induced by exposure to light after burial. In contrast to the prokaryotic cyanobacterial mats, mats with surface communities dominated by diatoms did not have high tolerance to burial. Two out of 3 samples of diatom mats failed to reactivate after 7 d of burial. The greater ability of cyanobacteria to survive week to month long periods of burial may be an important factor in accounting for the importance of these prokaryotes in Stromatolite construction.
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growth morphologies of modern marine Stromatolites a case study from highborne cay bahamas
Sedimentary Geology, 2006Co-Authors: Miriam S Andres, Pamela R ReidAbstract:Abstract Stromatolites are a uniquely coupled geo-biosphere system, which potentially records important paleoenvironmental and biological information. Characterizing and distinguishing between the biological and physical factors that control Stromatolite morphogenesis, therefore, has important implications for the understanding of modern Stromatolites and the interpretation of ancient systems. This paper documents the occurrence and distribution of Stromatolites with distinct growth morphologies in the Highborne Cay reef system and other locations in Exuma Cays, Bahamas, and explores the relative contributions of physical and biological environmental factors controlling Stromatolite shape. Our observations suggest that macro-scale growth morphologies of Exuma Stromatolites are primarily controlled by accommodation space, hydrodynamics, and sedimentation patterns. The latter are critical for the Stromatolite ecosystem in that the suspended sediment provides grains for trapping and binding and thus Stromatolite accretion. Furthermore, sediment burial removes macroalgae, allowing the prokaryotic community to dominate. Changes in sedimentation patterns and frequency allow for the colonization of Stromatolites by macroalgae and boring macrofauna, which, in time, destroy and degrade the Stromatolite structure.
Matthieu Réfrégiers - One of the best experts on this subject based on the ideXlab platform.
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characterization of pustular mats and related rivularia rich laminations in oncoids from the laguna negra lake argentina
Frontiers in Microbiology, 2018Co-Authors: Estela Cecilia Mlewski, Lena Lecourt, Eliana Soto Rueda, Benedicte Menez, Celine Pisapia, Karim Benzerara, Stephan Borensztajn, Frederic Jamme, Fernando Gomez, Matthieu RéfrégiersAbstract:Stromatolites are organo-sedimentary structures that represent some of the oldest records of the early biosphere on Earth. Cyanobacteria are considered as a main component of the microbial mats that are supposed to produce Stromatolite-like structures. Understanding the role of cyanobacteria and associated microorganisms on the mineralization processes is critical to better understand what can be preserved in the laminated structure of Stromatolites. Laguna Negra (Catamarca, Argentina), a high-altitude hypersaline lake where Stromatolites are currently formed, is considered as an analog environment of early Earth. This study aimed at characterizing carbonate precipitation within microbial mats and associated oncoids in Laguna Negra. In particular, we focused on carbonated black pustular mats. By combining Confocal Laser Scanning Microscopy, Scanning Electron Microscopy, Laser Microdissection and Whole Genome Amplification, Cloning and Sanger sequencing, and Focused Ion Beam milling for Transmission Electron Microscopy, we showed that carbonate precipitation did not directly initiate on the sheaths of cyanobacterial Rivularia, which dominate in the mat. It occurred via organo-mineralization processes within a large EPS matrix excreted by the diverse microbial consortium associated with Rivularia where diatoms and anoxygenic phototrophic bacteria were particularly abundant. By structuring a large microbial consortium, Rivularia should then favor the formation of organic-rich laminations of carbonates that can be preserved in Stromatolites. By using Fourier Transform Infrared spectroscopy and Synchrotron-based deep UV fluorescence imaging, we compared laminations rich in structures resembling Rivularia to putatively chemically-precipitated laminations in oncoids associated with the mats. We showed that they presented a different mineralogy jointly with a higher content in organic remnants, hence providing some criteria of biogenicity to be searched for in the fossil record.
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Data_Sheet_1_Characterization of Pustular Mats and Related Rivularia-Rich Laminations in Oncoids From the Laguna Negra Lake (Argentina).PDF
2018Co-Authors: Estela Cecilia Mlewski, Lena Lecourt, Eliana Soto Rueda, Benedicte Menez, Celine Pisapia, Karim Benzerara, Stephan Borensztajn, Frederic Jamme, Fernando Gomez, Matthieu RéfrégiersAbstract:Stromatolites are organo-sedimentary structures that represent some of the oldest records of the early biosphere on Earth. Cyanobacteria are considered as a main component of the microbial mats that are supposed to produce Stromatolite-like structures. Understanding the role of cyanobacteria and associated microorganisms on the mineralization processes is critical to better understand what can be preserved in the laminated structure of Stromatolites. Laguna Negra (Catamarca, Argentina), a high-altitude hypersaline lake where Stromatolites are currently formed, is considered as an analog environment of early Earth. This study aimed at characterizing carbonate precipitation within microbial mats and associated oncoids in Laguna Negra. In particular, we focused on carbonated black pustular mats. By combining Confocal Laser Scanning Microscopy, Scanning Electron Microscopy, Laser Microdissection and Whole Genome Amplification, Cloning and Sanger sequencing, and Focused Ion Beam milling for Transmission Electron Microscopy, we showed that carbonate precipitation did not directly initiate on the sheaths of cyanobacterial Rivularia, which dominate in the mat. It occurred via organo-mineralization processes within a large EPS matrix excreted by the diverse microbial consortium associated with Rivularia where diatoms and anoxygenic phototrophic bacteria were particularly abundant. By structuring a large microbial consortium, Rivularia should then favor the formation of organic-rich laminations of carbonates that can be preserved in Stromatolites. By using Fourier Transform Infrared spectroscopy and Synchrotron-based deep UV fluorescence imaging, we compared laminations rich in structures resembling Rivularia to putatively chemically-precipitated laminations in oncoids associated with the mats. We showed that they presented a different mineralogy jointly with a higher content in organic remnants, hence providing some criteria of biogenicity to be searched for in the fossil record.
