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Low temperature and acidic environments encompass natural milieus such as acid rock drainage in Antarctica and anthropogenic sites including drained sulfidic sediments in Scandinavia. The microorganisms inhabiting these environments include polyextremophiles that are both extreme acidophiles (defined as having an optimum growth pH < 3), and eurypsychrophiles that grow at low temperatures down to approximately 4 degrees C but have an optimum temperature for growth above 15 degrees C. Eurypsychrophilic acidophiles have important roles in natural biogeochemical cycling on earth and potentially on other planetary bodies and moons along with biotechnological applications in, for instance, low-temperature metal dissolution from metal sulfides. Five low-temperature acidophiles are characterized, namely, Acidithiobacillus ferriphilus, Acidithiobacillus ferrivorans, Acidithiobacillus ferrooxidans, "Ferrovum myxofaciens," and Alicyclobacillus disulfidooxidans, and their characteristics are reviewed. Our understanding of characterized and environmental eurypsychrophilic acidophiles has been accelerated by the application of "omics" techniques that have aided in revealing adaptations to low pH and temperature that can be synergistic, while other adaptations are potentially antagonistic. The lack of known acidophiles that exclusively grow below 15 degrees C may be due to the antagonistic nature of adaptations in this polyextremophile. In conclusion, this review summarizes the knowledge of eurypsychrophilic acidophiles and places the information in evolutionary, environmental, biotechnological, and exobiology perspectives.

Low temperature and acidic environments encompass natural milieus such as acid rock drainage in Antarctica and anthropogenic sites including drained sulfidic sediments in Scandinavia. The microorganisms inhabiting these environments include polyextremophiles that are both extreme acidophiles (defined as having an optimum growth pH < 3), and eurypsychrophiles that grow at low temperatures down to approximately 4 degrees C but have an optimum temperature for growth above 15 degrees C. Eurypsychrophilic acidophiles have important roles in natural biogeochemical cycling on earth and potentially on other planetary bodies and moons along with biotechnological applications in, for instance, low-temperature metal dissolution from metal sulfides. Five low-temperature acidophiles are characterized, namely, Acidithiobacillus ferriphilus, Acidithiobacillus ferrivorans, Acidithiobacillus ferrooxidans, "Ferrovum myxofaciens," and Alicyclobacillus disulfidooxidans, and their characteristics are reviewed. Our understanding of characterized and environmental eurypsychrophilic acidophiles has been accelerated by the application of "omics" techniques that have aided in revealing adaptations to low pH and temperature that can be synergistic, while other adaptations are potentially antagonistic. The lack of known acidophiles that exclusively grow below 15 degrees C may be due to the antagonistic nature of adaptations in this polyextremophile. In conclusion, this review summarizes the knowledge of eurypsychrophilic acidophiles and places the information in evolutionary, environmental, biotechnological, and exobiology perspectives.

Cryogenian Snowball Earth glaciations are some of the most extreme changes in Earth’s climate through its history. Decades of work have established the global ubiquity of Snowball Earth sedimentary deposits and their synchroneity in time, yet key questions remain concerning the potential causes for global glaciations and their drastically different durations and expressions in the rock record. This dissertation addresses these questions and proposes explanations for the onset of global glaciation and how the abrupt termination of a Snowball event could explain the differences in chemical sediments seen between the two Cryogenian Snowball events. In Chapter 1, I evaluate the emplacement of a large igneous province as a potential trigger for the Sturtian Snowball Earth (717-661 Ma). This work was done in collaboration with Francis A. Macdonald, Mark D. Schmitz, Robert H. Rainbird, Wouter Bleeker, Barra A. Peak, Rebecca M. Flowers, Paul F. Hoffman, Matthew Rioux, and Michael A. Hamilton. Previous geochronology has suggested a rough coincidence of glacial onset with one of the largest magmatic episodes in the geological record, the Franklin large igneous province. I show that chemical abrasion-isotope dilution-thermal ionization mass spectrometry (CA-ID-TIMS) U-Pb geochronology on zircon and baddeleyite from sills associated with the paleo-equatorial Franklin large igneous province in Arctic Canada record rapid emplacement between 719.86 ± 0.21 and 718.61 ± 0.30 Ma ago, 0.9 to 1.6 Ma before the onset of widespread glaciation. Geologic observations and (U-Th)/He dates on Franklin sills are compatible with major post–Franklin exhumation, possibly due to development of mafic volcanic highlands on windward equatorial Laurentia and increased global weatherability. After a transient magmatic CO2 flux, long-term carbon sequestration associated with increased weatherability could have nudged Earth over the threshold for runaway ice-albedo feedback.In Chapter 2, I address whethe

Low temperature and acidic environments encompass natural milieus such as acid rock drainage in Antarctica and anthropogenic sites including drained sulfidic sediments in Scandinavia. The microorganisms inhabiting these environments include polyextremophiles that are both extreme acidophiles (defined as having an optimum growth pH < 3), and eurypsychrophiles that grow at low temperatures down to approximately 4 degrees C but have an optimum temperature for growth above 15 degrees C. Eurypsychrophilic acidophiles have important roles in natural biogeochemical cycling on earth and potentially on other planetary bodies and moons along with biotechnological applications in, for instance, low-temperature metal dissolution from metal sulfides. Five low-temperature acidophiles are characterized, namely, Acidithiobacillus ferriphilus, Acidithiobacillus ferrivorans, Acidithiobacillus ferrooxidans, "Ferrovum myxofaciens," and Alicyclobacillus disulfidooxidans, and their characteristics are reviewed. Our understanding of characterized and environmental eurypsychrophilic acidophiles has been accelerated by the application of "omics" techniques that have aided in revealing adaptations to low pH and temperature that can be synergistic, while other adaptations are potentially antagonistic. The lack of known acidophiles that exclusively grow below 15 degrees C may be due to the antagonistic nature of adaptations in this polyextremophile. In conclusion, this review summarizes the knowledge of eurypsychrophilic acidophiles and places the information in evolutionary, environmental, biotechnological, and exobiology perspectives.

Low temperature and acidic environments encompass natural milieus such as acid rock drainage in Antarctica and anthropogenic sites including drained sulfidic sediments in Scandinavia. The microorganisms inhabiting these environments include polyextremophiles that are both extreme acidophiles (defined as having an optimum growth pH < 3), and eurypsychrophiles that grow at low temperatures down to approximately 4 degrees C but have an optimum temperature for growth above 15 degrees C. Eurypsychrophilic acidophiles have important roles in natural biogeochemical cycling on earth and potentially on other planetary bodies and moons along with biotechnological applications in, for instance, low-temperature metal dissolution from metal sulfides. Five low-temperature acidophiles are characterized, namely, Acidithiobacillus ferriphilus, Acidithiobacillus ferrivorans, Acidithiobacillus ferrooxidans, "Ferrovum myxofaciens," and Alicyclobacillus disulfidooxidans, and their characteristics are reviewed. Our understanding of characterized and environmental eurypsychrophilic acidophiles has been accelerated by the application of "omics" techniques that have aided in revealing adaptations to low pH and temperature that can be synergistic, while other adaptations are potentially antagonistic. The lack of known acidophiles that exclusively grow below 15 degrees C may be due to the antagonistic nature of adaptations in this polyextremophile. In conclusion, this review summarizes the knowledge of eurypsychrophilic acidophiles and places the information in evolutionary, environmental, biotechnological, and exobiology perspectives.

Low temperature and acidic environments encompass natural milieus such as acid rock drainage in Antarctica and anthropogenic sites including drained sulfidic sediments in Scandinavia. The microorganisms inhabiting these environments include polyextremophiles that are both extreme acidophiles (defined as having an optimum growth pH < 3), and eurypsychrophiles that grow at low temperatures down to approximately 4 degrees C but have an optimum temperature for growth above 15 degrees C. Eurypsychrophilic acidophiles have important roles in natural biogeochemical cycling on earth and potentially on other planetary bodies and moons along with biotechnological applications in, for instance, low-temperature metal dissolution from metal sulfides. Five low-temperature acidophiles are characterized, namely, Acidithiobacillus ferriphilus, Acidithiobacillus ferrivorans, Acidithiobacillus ferrooxidans, "Ferrovum myxofaciens," and Alicyclobacillus disulfidooxidans, and their characteristics are reviewed. Our understanding of characterized and environmental eurypsychrophilic acidophiles has been accelerated by the application of "omics" techniques that have aided in revealing adaptations to low pH and temperature that can be synergistic, while other adaptations are potentially antagonistic. The lack of known acidophiles that exclusively grow below 15 degrees C may be due to the antagonistic nature of adaptations in this polyextremophile. In conclusion, this review summarizes the knowledge of eurypsychrophilic acidophiles and places the information in evolutionary, environmental, biotechnological, and exobiology perspectives.

A series of dramatic oceanic and atmospheric events occurred in the immediate aftermath of the Marinoan “snowball Earth” meltdown ∼635 My ago. However, at the 10-to 100-ky timescale, the order, rate, duration, and causal-feedback relationships of these individual events remain nebulous. Nonetheless, rapid swings in regional marine sulfate concentrations are predicted to have occurred in the aftermath of a snowball Earth, due to the nonlinear responses of its two major controlling fluxes: oxidative weathering on the continents and pyrite burial in marine sediments. Here, through the application of multiple isotope systems on various carbon and sulfur compounds, we determined extremely 13C-depleted calcite cements in the basal Ediacaran in South China to be the result of microbial sulfate reduction coupled to anaerobic oxidation of methane, which indicates an interval of high sulfate concentrations in some part of the postmeltdown ocean. Regional chemostratigraphy places the 13C-depleted cements at the equivalent of the earliest Ediacaran 17O-depletion episode, thus confining the timing of this peak in sulfate concentrations within ∼50 ky since the onset of the deglaciation. The dearth of similarly 13C-depleted cements in other Proterozoic successions implies that the earliest Ediacaran peak in marine sulfate concentration is a regional and likely transient event.

The addition of carbon dioxide (CO2) in the atmosphere due to human activities is the main driver of global warming. How much the Earth will warm in the future is often represented by the Earth's equilibrium climate sensitivity (ECS), the long-term temperature response considering the effect of climate feedbacks after an abrupt and sustained doubling of atmospheric CO2 from pre-industrial concentration. Assessing ECS is critical as it is one of the most relevant metric to evaluate global temperature change by 2100 in a fast warming climate. However, there have been considerable difficulties in constraining ECS for more than a century. In recent years, there has been a focus on alternative lines of evidence to elicit ECS, such as the study of past climates. The work of this thesis investigates the evidence on ECS and climate feedbacks obtained from paleoclimates. In our studies, we use past climate reconstructions and climate modelling to estimate ECS out of the cold Last Glacial Maximum (LGM) and the warm Pliocene. Our work focuses on the statistical relationship existing between simulated past temperatures and ECS following the emergent constraint theory, and how the physics of modelled paleoclimates can affect such relationship. We explore further how climate feedbacks behave and depart from a linear behaviour in extreme cold conditions by performing simulations of snowball Earth states. This thesis demonstrates that both LGM and Pliocene are relevant candidates to elicit ECS and highlights the contribution of paleoclimates in understanding modern and future climate change. In particular, we show that the Pliocene is a robust constraint on ECS under the emergent constraint theory despite large observational uncertainties. Our estimate of ECS using the most recent generation of climate models is 4.8 K, which lies in the high end of previous assessment from Pliocene evidence. On the contrary, the LGM constraint is weak due to substantial differences in ice sheet for

The addition of carbon dioxide (CO2) in the atmosphere due to human activities is the main driver of global warming. How much the Earth will warm in the future is often represented by the Earth's equilibrium climate sensitivity (ECS), the long-term temperature response considering the effect of climate feedbacks after an abrupt and sustained doubling of atmospheric CO2 from pre-industrial concentration. Assessing ECS is critical as it is one of the most relevant metric to evaluate global temperature change by 2100 in a fast warming climate. However, there have been considerable difficulties in constraining ECS for more than a century. In recent years, there has been a focus on alternative lines of evidence to elicit ECS, such as the study of past climates. The work of this thesis investigates the evidence on ECS and climate feedbacks obtained from paleoclimates. In our studies, we use past climate reconstructions and climate modelling to estimate ECS out of the cold Last Glacial Maximum (LGM) and the warm Pliocene. Our work focuses on the statistical relationship existing between simulated past temperatures and ECS following the emergent constraint theory, and how the physics of modelled paleoclimates can affect such relationship. We explore further how climate feedbacks behave and depart from a linear behaviour in extreme cold conditions by performing simulations of snowball Earth states. This thesis demonstrates that both LGM and Pliocene are relevant candidates to elicit ECS and highlights the contribution of paleoclimates in understanding modern and future climate change. In particular, we show that the Pliocene is a robust constraint on ECS under the emergent constraint theory despite large observational uncertainties. Our estimate of ECS using the most recent generation of climate models is 4.8 K, which lies in the high end of previous assessment from Pliocene evidence. On the contrary, the LGM constraint is weak due to substantial differences in ice sheet for

The addition of carbon dioxide (CO2) in the atmosphere due to human activities is the main driver of global warming. How much the Earth will warm in the future is often represented by the Earth's equilibrium climate sensitivity (ECS), the long-term temperature response considering the effect of climate feedbacks after an abrupt and sustained doubling of atmospheric CO2 from pre-industrial concentration. Assessing ECS is critical as it is one of the most relevant metric to evaluate global temperature change by 2100 in a fast warming climate. However, there have been considerable difficulties in constraining ECS for more than a century. In recent years, there has been a focus on alternative lines of evidence to elicit ECS, such as the study of past climates. The work of this thesis investigates the evidence on ECS and climate feedbacks obtained from paleoclimates. In our studies, we use past climate reconstructions and climate modelling to estimate ECS out of the cold Last Glacial Maximum (LGM) and the warm Pliocene. Our work focuses on the statistical relationship existing between simulated past temperatures and ECS following the emergent constraint theory, and how the physics of modelled paleoclimates can affect such relationship. We explore further how climate feedbacks behave and depart from a linear behaviour in extreme cold conditions by performing simulations of snowball Earth states. This thesis demonstrates that both LGM and Pliocene are relevant candidates to elicit ECS and highlights the contribution of paleoclimates in understanding modern and future climate change. In particular, we show that the Pliocene is a robust constraint on ECS under the emergent constraint theory despite large observational uncertainties. Our estimate of ECS using the most recent generation of climate models is 4.8 K, which lies in the high end of previous assessment from Pliocene evidence. On the contrary, the LGM constraint is weak due to substantial differences in ice sheet for

The addition of carbon dioxide (CO2) in the atmosphere due to human activities is the main driver of global warming. How much the Earth will warm in the future is often represented by the Earth's equilibrium climate sensitivity (ECS), the long-term temperature response considering the effect of climate feedbacks after an abrupt and sustained doubling of atmospheric CO2 from pre-industrial concentration. Assessing ECS is critical as it is one of the most relevant metric to evaluate global temperature change by 2100 in a fast warming climate. However, there have been considerable difficulties in constraining ECS for more than a century. In recent years, there has been a focus on alternative lines of evidence to elicit ECS, such as the study of past climates. The work of this thesis investigates the evidence on ECS and climate feedbacks obtained from paleoclimates. In our studies, we use past climate reconstructions and climate modelling to estimate ECS out of the cold Last Glacial Maximum (LGM) and the warm Pliocene. Our work focuses on the statistical relationship existing between simulated past temperatures and ECS following the emergent constraint theory, and how the physics of modelled paleoclimates can affect such relationship. We explore further how climate feedbacks behave and depart from a linear behaviour in extreme cold conditions by performing simulations of snowball Earth states. This thesis demonstrates that both LGM and Pliocene are relevant candidates to elicit ECS and highlights the contribution of paleoclimates in understanding modern and future climate change. In particular, we show that the Pliocene is a robust constraint on ECS under the emergent constraint theory despite large observational uncertainties. Our estimate of ECS using the most recent generation of climate models is 4.8 K, which lies in the high end of previous assessment from Pliocene evidence. On the contrary, the LGM constraint is weak due to substantial differences in ice sheet for

The addition of carbon dioxide (CO2) in the atmosphere due to human activities is the main driver of global warming. How much the Earth will warm in the future is often represented by the Earth's equilibrium climate sensitivity (ECS), the long-term temperature response considering the effect of climate feedbacks after an abrupt and sustained doubling of atmospheric CO2 from pre-industrial concentration. Assessing ECS is critical as it is one of the most relevant metric to evaluate global temperature change by 2100 in a fast warming climate. However, there have been considerable difficulties in constraining ECS for more than a century. In recent years, there has been a focus on alternative lines of evidence to elicit ECS, such as the study of past climates. The work of this thesis investigates the evidence on ECS and climate feedbacks obtained from paleoclimates. In our studies, we use past climate reconstructions and climate modelling to estimate ECS out of the cold Last Glacial Maximum (LGM) and the warm Pliocene. Our work focuses on the statistical relationship existing between simulated past temperatures and ECS following the emergent constraint theory, and how the physics of modelled paleoclimates can affect such relationship. We explore further how climate feedbacks behave and depart from a linear behaviour in extreme cold conditions by performing simulations of snowball Earth states. This thesis demonstrates that both LGM and Pliocene are relevant candidates to elicit ECS and highlights the contribution of paleoclimates in understanding modern and future climate change. In particular, we show that the Pliocene is a robust constraint on ECS under the emergent constraint theory despite large observational uncertainties. Our estimate of ECS using the most recent generation of climate models is 4.8 K, which lies in the high end of previous assessment from Pliocene evidence. On the contrary, the LGM constraint is weak due to substantial differences in ice sheet for

There is now much geological evidence that the Earth was fully glaciated during several periods in the geological past (about 700Myr ago) and attained a so-called Snowball Earth (SBE) state. Additional support for this idea has come from climate models of varying complexity that show transitions to SBE states and undergo hysteresis under changes in solar radiation. In this paper, we apply large-scale bifurcation analyses to a novel, fully-implicit Earth System Model of Intermediate Complexity (I-EMIC) to study SBE transitions. The I-EMIC contains a primitive equation ocean model, a model for atmospheric heat and moisture transport, a sea ice component and formulations for the adjustment of albedo over snow and ice. With the I-EMIC, high-dimensional branches of the SBE bifurcation diagram are obtained through parameter continuation. We are able to identify stable and unstable equilibria and uncover an intricate bifurcation structure associated with the ice-albedo feedback. Moreover, large-scale linear stability analyses are performed near major bifurcations, revealing the spatial nature of destabilizing perturbations.

The Trezona carbon isotope excursion is recorded on five different continents in platform carbonates deposited prior to the end-Cryogenian Marinoan glaciation (>635 Ma) and represents a change in carbon isotope values of 16–18‰. Based on the spatial and temporal reproducibility, the excursion previously has been interpreted as tracking the carbon isotopic composition of dissolved inorganic carbon in the global ocean before the descent into a snowball Earth. However, in modern restricted shallow marine and freshwater settings, carbon isotope values have a similarly large range, which is mostly independent from open ocean chemistry and instead reflects local processes. In this study, we combine calcium, magnesium, and strontium isotope geochemistry with a numerical model of carbonate diagenesis to disentangle the degree to which the Trezona excursion reflects changes in global seawater chemistry versus local shallow-water platform environments. Our analysis demonstrates that the most extreme carbon isotope values (∼-10‰ versus +10‰) are preserved in former platform aragonite that was neomorphosed to calcite during sediment-buffered conditions and record the primary carbon isotope composition of platform-top surface waters. In contrast, the downturn and recovery of the Trezona excursion are recorded in carbonates that were altered during early fluid-buffered diagenesis and commonly are dolomitized. We also find that the nadir of the Trezona excursion is associated with a fractional increase in siliciclastic sediments, whereas the recovery from the excursion correlates with a relative increase in carbonate. This relationship suggests that the extreme negative isotopic shift in platform aragonite occurred in concert with periods of increased input of siliciclastic sediments, changes in water depth, and possibly nutrients to platform environments. Although the process for generating extremely negative carbon isotope values in Neoproterozoic platform carbonates remai

The Trezona carbon isotope excursion is recorded on five different continents in platform carbonates deposited prior to the end-Cryogenian Marinoan glaciation (>635 Ma) and represents a change in carbon isotope values of 16–18‰. Based on the spatial and temporal reproducibility, the excursion previously has been interpreted as tracking the carbon isotopic composition of dissolved inorganic carbon in the global ocean before the descent into a snowball Earth. However, in modern restricted shallow marine and freshwater settings, carbon isotope values have a similarly large range, which is mostly independent from open ocean chemistry and instead reflects local processes. In this study, we combine calcium, magnesium, and strontium isotope geochemistry with a numerical model of carbonate diagenesis to disentangle the degree to which the Trezona excursion reflects changes in global seawater chemistry versus local shallow-water platform environments. Our analysis demonstrates that the most extreme carbon isotope values (∼-10‰ versus +10‰) are preserved in former platform aragonite that was neomorphosed to calcite during sediment-buffered conditions and record the primary carbon isotope composition of platform-top surface waters. In contrast, the downturn and recovery of the Trezona excursion are recorded in carbonates that were altered during early fluid-buffered diagenesis and commonly are dolomitized. We also find that the nadir of the Trezona excursion is associated with a fractional increase in siliciclastic sediments, whereas the recovery from the excursion correlates with a relative increase in carbonate. This relationship suggests that the extreme negative isotopic shift in platform aragonite occurred in concert with periods of increased input of siliciclastic sediments, changes in water depth, and possibly nutrients to platform environments. Although the process for generating extremely negative carbon isotope values in Neoproterozoic platform carbonates remai

The beginning of the Ediacaran Period (∼635 Ma) is marked by conspicuous dolostone units that cap Marinoan glacial deposits worldwide. The extent and sedimentary characteristics of the cap dolostones indicate that anomalous carbonate over-saturation coincided with deglacial sea-level rise and ocean warming. However, the geochemical variability within cap dolostones, both between continents, across single continental margins, and within individual stratigraphic sections has been difficult to reconcile with depositional models. Using a compilation of new calcium and magnesium isotope measurements in Marinoan cap dolostone successions worldwide, we show that the geochemical variability can be explained by early diagenetic dolomitization of aragonite along a spectrum of fluid- and sediment-buffered conditions. Dolostones from the outer platform formed under fluid-buffered conditions, whereas dolostones on the inner platform and foreslope environment formed under sediment-buffered conditions. This spatial pattern of dolomitizing conditions is consistent with buoyant recirculation of glacial seawater within carbonate platforms driven by the deglacial sea-level rise and development of a meltwater surface ocean. Using a numerical diagenetic model to evaluate the geochemical differences between sediment- and fluid-buffered cap dolostone units, we constrain the chemical and isotopic composition of both the dolomitizing fluid (glacial seawater [δ13C ∼ 0–2‰]), the meltwater lens (δ13C ∼−11‰), and the primary aragonite sediment (δ13C ∼−6 to −3‰). These model end-members do not imply that primary geochemical variability did not exist but demonstrates that it is not necessary to change the chemistry of seawater to explain the global stratigraphic variability in the geochemistry of basal Ediacaran cap dolostones. Our results provide a novel framework for understanding the geochemical variability of cap dolostone units, including large excursions

The Great Unconformity, a profound gap in Earth's stratigraphic record often evident below the base of the Cambrian system, has remained among the most enigmatic field observations in Earth science for over a century. While long associated directly or indirectly with the occurrence of the earliest complex animal fossils, a conclusive explanation for the formation and global extent of the Great Unconformity has remained elusive. Here we show that the Great Unconformity is associated with a set of large global oxygen and hafnium isotope excursions in magmatic zircon that suggest a late Neoproterozoic crustal erosion and sediment subduction event of unprecedented scale. These excursions, the Great Unconformity, preservational irregularities in the terrestrial bolide impact record, and the first-order pattern of Phanerozoic sedimentation can together be explained by spatially heterogeneous Neoproterozoic glacial erosion totaling a global average of 3-5 vertical kilometers, along with the subsequent thermal and isostatic consequences of this erosion for global continental freeboard.

The Kamoa copper deposit (759 Mt, 2.67% Cu at 1% cut-off) is one of the largest copper deposits in the central African copperbelt. Mineralisation at Kamoa is hosted by the Cryogenian ‘grand conglomérat’, which was deposited in an intracratonic rift and its sub- basins associated with the break-up of Rodinia, and is equated to the ‘Sturtian’ glaciation, the oldest of the Neoproterozoic glacial events. Using detrital zircon geochronology, the provenance of synglacial and underlying pre-glacial units is compared, to evaluate the temporal dynamics of the sediment supply at Kamoa. The detrital zircon age distributions suggest that the ‘grand conglomérat’ was derived from locally exposed basement of the Mesoproterozoic Kibaran Supergroup and from significant recycling of underlying pre-glacial units, with minor contributions from distal, primary source areas. The stratigraphic differences in the distribution of zircon age populations of the strata at Kamoa may reflect changes in glacial dynamics or of rifting during deposition of the ‘grand conglomérat’. A Neoproterozoic zircon age population ~700 Ma is probably derived from rift-related volcanic rocks and is significant because it repositions the timing of mid-Neoproterozoic rifting in the Katangan basin and the maximum depositional age of the ‘grand conglomérat’. The new age constraints suggest that the midNeoproterozoic ‘Sturtian’ glaciation was globally diachronous.

The Great Unconformity, a profound gap in Earth's stratigraphic record often evident below the base of the Cambrian system, has remained among the most enigmatic field observations in Earth science for over a century. While long associated directly or indirectly with the occurrence of the earliest complex animal fossils, a conclusive explanation for the formation and global extent of the Great Unconformity has remained elusive. Here we show that the Great Unconformity is associated with a set of large global oxygen and hafnium isotope excursions in magmatic zircon that suggest a late Neoproterozoic crustal erosion and sediment subduction event of unprecedented scale. These excursions, the Great Unconformity, preservational irregularities in the terrestrial bolide impact record, and the first-order pattern of Phanerozoic sedimentation can together be explained by spatially heterogeneous Neoproterozoic glacial erosion totaling a global average of 3-5 vertical kilometers, along with the subsequent thermal and isostatic consequences of this erosion for global continental freeboard.

The Kamoa copper deposit (759 Mt, 2.67% Cu at 1% cut-off) is one of the largest copper deposits in the central African copperbelt. Mineralisation at Kamoa is hosted by the Cryogenian ‘grand conglomérat’, which was deposited in an intracratonic rift and its sub- basins associated with the break-up of Rodinia, and is equated to the ‘Sturtian’ glaciation, the oldest of the Neoproterozoic glacial events. Using detrital zircon geochronology, the provenance of synglacial and underlying pre-glacial units is compared, to evaluate the temporal dynamics of the sediment supply at Kamoa. The detrital zircon age distributions suggest that the ‘grand conglomérat’ was derived from locally exposed basement of the Mesoproterozoic Kibaran Supergroup and from significant recycling of underlying pre-glacial units, with minor contributions from distal, primary source areas. The stratigraphic differences in the distribution of zircon age populations of the strata at Kamoa may reflect changes in glacial dynamics or of rifting during deposition of the ‘grand conglomérat’. A Neoproterozoic zircon age population ~700 Ma is probably derived from rift-related volcanic rocks and is significant because it repositions the timing of mid-Neoproterozoic rifting in the Katangan basin and the maximum depositional age of the ‘grand conglomérat’. The new age constraints suggest that the midNeoproterozoic ‘Sturtian’ glaciation was globally diachronous.

Water is a primary driver of the physical, geochemical and biological evolution of the Earth. The near-surface hydrosphere (exosphere) includes the atmosphere, cryosphere (glacial and polar ice), the biosphere, surface water, groundwater, and the oceans. The amounts of water in these various reservoirs of the hydrologic cycle have likely varied significantly over the past 700 Ma, with the cryosphere and continental biosphere reservoirs likely showing the most dramatic variations relative to the modern. For example, 700 Ma, during snowball-Earth conditions, the planet may have been almost entirely enveloped in ice, whereas throughout much of the Phanerozoic, greenhouse conditions predominately prevailed and the Earth had a much smaller cryosphere. Similarly, before about 444 Ma and the proliferation of land plants, the continental biosphere reservoir would have effectively non-existent. However, today, plants play a critical role in storage and transfer of water within the hydrologic cycle. Because the amount of water in the exosphere is thought to have remained relatively constant during the past 700 Ma, variations in the amounts of water held by the in the various exogenic reservoirs exert concomitant effects on other reservoirs in the exosphere. We present a conceptual and numerical model that examines variations in the amount of water in the various reservoirs of the near-surface hydrologic cycle (exosphere) during the past 700 Ma and quantify variations in the rates of exchange of water between these reservoirs in deep time. Variations in the sizes of major reservoirs are primarily controlled by changes in global average temperature, and the movement of water between the atmosphere, surface water, and ocean reservoirs varies in concert with the waxing and waning of the cryosphere. We find that variations in the sizes of major reservoirs are primarily controlled by changes in global average temperature, and the flux of water between the atmosphere, surface water

Water is a primary driver of the physical, geochemical and biological evolution of the Earth. The near-surface hydrosphere (exosphere) includes the atmosphere, cryosphere (glacial and polar ice), the biosphere, surface water, groundwater, and the oceans. The amounts of water in these various reservoirs of the hydrologic cycle have likely varied significantly over the past 700 Ma, with the cryosphere and continental biosphere reservoirs likely showing the most dramatic variations relative to the modern. For example, 700 Ma, during snowball-Earth conditions, the planet may have been almost entirely enveloped in ice, whereas throughout much of the Phanerozoic, greenhouse conditions predominately prevailed and the Earth had a much smaller cryosphere. Similarly, before about 444 Ma and the proliferation of land plants, the continental biosphere reservoir would have effectively non-existent. However, today, plants play a critical role in storage and transfer of water within the hydrologic cycle. Because the amount of water in the exosphere is thought to have remained relatively constant during the past 700 Ma, variations in the amounts of water held by the in the various exogenic reservoirs exert concomitant effects on other reservoirs in the exosphere. We present a conceptual and numerical model that examines variations in the amount of water in the various reservoirs of the near-surface hydrologic cycle (exosphere) during the past 700 Ma and quantify variations in the rates of exchange of water between these reservoirs in deep time. Variations in the sizes of major reservoirs are primarily controlled by changes in global average temperature, and the movement of water between the atmosphere, surface water, and ocean reservoirs varies in concert with the waxing and waning of the cryosphere. We find that variations in the sizes of major reservoirs are primarily controlled by changes in global average temperature, and the flux of water between the atmosphere, surface water

The first significant buildup in atmospheric oxygen, the Great Oxidation Event (GOE), began in the early Paleoproterozoic in association with global glaciations and continued until the end of the Lomagundi carbon isotope excursion ca. 2,060 Ma. The exact timing of and relationships among these events are debated because of poor age constraints and contradictory stratigraphic correlations. Here, we show that the first Paleoproterozoic global glaciation and the onset of the GOE occurred between ca. 2,460 and 2,426 Ma, ∼100 My earlier than previously estimated, based on an age of 2,426 ± 3 Ma for Ongeluk Formation magmatism from the Kaapvaal Craton of southern Africa. This age helps define a key paleomagnetic pole that positions the Kaapvaal Craton at equatorial latitudes of 11° ± 6° at this time. Furthermore, the rise of atmospheric oxygen was not monotonic, but was instead characterized by oscillations, which together with climatic instabilities may have continued over the next ∼200 My until ≤2,250-2,240 Ma. Ongeluk Formation volcanism at ca. 2,426 Ma was part of a large igneous province (LIP) and represents a waning stage in the emplacement of several temporally discrete LIPs across a large low-latitude continental landmass. These LIPs played critical, albeit complex, roles in the rise of oxygen and in both initiating and terminating global glaciations. This series of events invites comparison with the Neoproterozoic oxygen increase and Sturtian Snowball Earth glaciation, which accompanied emplacement of LIPs across supercontinent Rodinia, also positioned at low latitude.

Author Posting. © The Author(s), 2015. This is the author's version of the work. It is posted here for personal use, not for redistribution. The definitive version was published in Earth and Planetary Science Letters 437 (2016): 76-88, doi:10.1016/j.epsl.2015.12.040., High concentrations of extraterrestrial iridium have been reported in terminal Sturtian and Marinoan glacial marine sediments and are used to argue for long (likely 3-12 Myr) durations of these Cryogenian glaciations. Reanalysis of the Marinoan sedimentary rocks used in the original study, supplemented by sedimentary rocks from additional terminal Marinoan sections, however, does not confirm the initial report. New platinum group element concentrations, and 187Os/188Os and 3He/4He signatures are consistent with crustal origin and minimal extraterrestrial contributions. The discrepancy is likely caused by different sample masses used in the two studies, with this study being based on much larger samples that better capture the stochastic distribution of extraterrestrial particles in marine sediments. Strong enrichment of redox-sensitive elements, particularly rhenium, up-section in the basal postglacial cap carbonates, may indicate a return to more fully oxygenated seawater in the aftermath of the Marinoan snowball earth. Sections dominated by hydrogenous osmium indicate increasing submarine hydrothermal sources and/or continental inputs that are increasingly dominated by young mantle-derived rocks after deglaciation. Sedimentation rate estimates for the basal cap carbonates yield surprisingly slow rates of a few centimeters per thousand years. This study highlights the importance of using sedimentary rock samples that represent sufficiently large area-time products to properly sample extraterrestrial particles representatively, and demonstrates the value of using multiple tracers of extraterrestrial matter., We are grateful for support from a 2008 WHOI Summer Student Fellowship for CAW. BPE acknowledges financial support from WHOI’s Ocean and Climate Change Institute (CH11320) and U.S. NSF SGER grant EAR-0821878. Fieldwork in NW Canada was licensed by the Aurora Research Institute and supported by a grant to PFH from the Astrobiology Institute of the US National Aeronautics and Space Administration (NASA). Fieldwork in NW Canada and Namibia was supported by grants EAR-9905495 and EAR-0417422 (to PFH) from the US NSF. We thank Jon Husson (Harvard University) and Ricardo Trindade (University of São Paulo, Brazil) for excellent support during fieldwork in Namibia in August of 2005.

Paleogeographic data indicate that the Neoproterozoic Rapitan Group accumulated in two spatially related, silled basins during the first mid-Neoproterozoic glacial episode (ca. 711 Ma), yet the controls on glaciation, reason for basin development, spatio-temporal relationships among stratigraphic units, and constraints on iron formation deposition and distribution in this region and globally at this time have not been adequately explained. The lack of a coherent understanding of the group's regional stratigraphy has been a significant barrier to deciphering the geologic history of this critically important succession. Based on new stratigraphic data, and incorporating the results of a related geochemical study, the Rapitan Group accumulated in tectonically complex sub-basins of a young rift zone. The spatial and temporal dynamics of these sub-basins controlled the grain size, volume, and distribution of detrital sediment (predominantly turbidites and diamictites) deposited during two glacially influenced episodes with ice cover. During an interglacial episode, the rotated, exposed upper surfaces of newly displaced rift blocks directed drainage away from basin margins, precluding significant clastic sediment delivery, and subaqueous margins of outboard tilted fault blocks acted as sills that isolated local bottom water, allowing the accumulation of an entirely hydrogenous succession (jaspilitic and hematitic iron formation). Two strike-parallel normal faults that strongly controlled basin-margin development are prominent thrust faults in the present-day orogen. Syndepositional activity of strike-normal transfer faults segmented the basins along their length, as reflected in pronounced along-strike variations in the presence/absence, thickness, and composition of the three stratigraphic units (Mt. Berg, Sayunei, and Shezal formations), and in the presence or absence of iron formation (locally >100 m thick; top of Sayunei Formation). Differential subsidence in actively

Author Posting. © The Author(s), 2015. This is the author's version of the work. It is posted here for personal use, not for redistribution. The definitive version was published in Earth and Planetary Science Letters 437 (2016): 76-88, doi:10.1016/j.epsl.2015.12.040., High concentrations of extraterrestrial iridium have been reported in terminal Sturtian and Marinoan glacial marine sediments and are used to argue for long (likely 3-12 Myr) durations of these Cryogenian glaciations. Reanalysis of the Marinoan sedimentary rocks used in the original study, supplemented by sedimentary rocks from additional terminal Marinoan sections, however, does not confirm the initial report. New platinum group element concentrations, and 187Os/188Os and 3He/4He signatures are consistent with crustal origin and minimal extraterrestrial contributions. The discrepancy is likely caused by different sample masses used in the two studies, with this study being based on much larger samples that better capture the stochastic distribution of extraterrestrial particles in marine sediments. Strong enrichment of redox-sensitive elements, particularly rhenium, up-section in the basal postglacial cap carbonates, may indicate a return to more fully oxygenated seawater in the aftermath of the Marinoan snowball earth. Sections dominated by hydrogenous osmium indicate increasing submarine hydrothermal sources and/or continental inputs that are increasingly dominated by young mantle-derived rocks after deglaciation. Sedimentation rate estimates for the basal cap carbonates yield surprisingly slow rates of a few centimeters per thousand years. This study highlights the importance of using sedimentary rock samples that represent sufficiently large area-time products to properly sample extraterrestrial particles representatively, and demonstrates the value of using multiple tracers of extraterrestrial matter., We are grateful for support from a 2008 WHOI Summer Student Fellowship for CAW. BPE acknowledges financial support from WHOI’s Ocean and Climate Change Institute (CH11320) and U.S. NSF SGER grant EAR-0821878. Fieldwork in NW Canada was licensed by the Aurora Research Institute and supported by a grant to PFH from the Astrobiology Institute of the US National Aeronautics and Space Administration (NASA). Fieldwork in NW Canada and Namibia was supported by grants EAR-9905495 and EAR-0417422 (to PFH) from the US NSF. We thank Jon Husson (Harvard University) and Ricardo Trindade (University of São Paulo, Brazil) for excellent support during fieldwork in Namibia in August of 2005.

The upper carbonate-rich parts of theWest Congo Supergroup (~1000-560 Ma) fromthe Democratic Republic of the Congo have hitherto been considered as a record of abrupt eustatic and climatic events accompanying glaciation and deglaciation of a Snowball Earth-type Marinoan ice age that was of global extent. These strata have however never been investigated in detail. Results of new sedimentological work at key outcrops over a 1300 km outcrop belt show that pre -and post-Marinoan carbonates are respectively, storm-influenced sediments deposited principally in a midouter-ramp setting, and deep-water slope carbonates (calicturbidites) representing a lobe-fringe or levee-overbank setting. The Upper Diamictite Formation held previously by some to be a subglacial tillite, comprises gravity flows (debrites) deposited in deep water below wave base along the unstable margins of a carbonate ramp. A direct glacial influence on sedimentation for diamictites or any accompanying facies cannot be readily identified. Sedimentary facies reported here primarily record the presence of deep-water submarine to alluvial fan systems related to extensional tectonic processes of the central-southern Macaúbas Basin (now located in Brazil) between 700 Ma and 660 Ma followed by the 630-Ma onset of the pre-collisional magmatic arc in the Araçuaí-West Congo Orogen. No extreme short-lived climatic or eustatic events of a Snowball Earth-type ice age are recorded in the studied succession, which primarily reflects longterm overriding regional tectonic controls resulting in diachronous sedimentation along the western margin of the Congo Craton., SCOPUS: ar.j, info:eu-repo/semantics/published

In the Lower Congo region, the Ediacaran Schisto-Calcaire Subgroup consists of five carbonate-dominated formations (C1 to C5). They record tectono-eustatic sea-level fluctuations controlled by several short-time extensional tectonic events occurred in the whole basin, followed by the development of the Araçuaï-West Congo Orogen between 630. Ma and 560. Ma. The uppermost units of the C2 Formation, i.e. C2d and C2e members, consist of open marine to peritidal/sabkha cycles of 1-4. m in thickness formed during in a Highstand Systems Tract (HST). The unexposed transition between the C2 and C3 formations is interpreted as a 'final' HSTphase which initiated the burial of the carbonate ramp by prograding siliciclastics or an early Transgressive Systems Tract (TST) phase. The carbonates of the C3 Formation represent open marine shallowing-upward cycles of 3-8. m in thickness, with deposition at the top of massive oolitic barrier shoals during a TST which flooded the entire the Neoproterozoic West Congo Basin. During the highstand, contributions of river water and land-derived material inputs occured, intermittently according to the semi-arid to arid conditions that prevailed in the restricted inner ramp and in the sabkha facies belts. In term of geochemistry, the disturbed δ13C trends of the post-Marinoan C2 and C3 carbonates rather reflect early diagenetic variations related to (i) the mixing of carbonate rocks with 13C and 18O depleted fluids including decarboxylation during early organic diagenesis and deep burial, or (ii) the meteoric alteration during carbonate stabilization, than temporal signals of the global ocean chemistry. This observation does not negate the stratigraphic utility of δ13C ratios for intrabasinal correlations., SCOPUS: ar.j, info:eu-repo/semantics/published

Intense glaciation during the end of Cryogenian time (~635 million years ago) marks the coldest climate state in Earth history - a time when glacial deposits accumulated at low, tropical paleolatitudes. The leading idea to explain these deposits, the snowball Earth hypothesis, predicts globally frozen surface conditions and subfreezing temperatures, with global climate models placing surface temperatures in the tropics between -20 °C and -60 °C. However, precise paleosurface temperatures based upon geologic constraints have remained elusive and the global severity of the glaciation undetermined. Here we make new geologic observations of tropical periglacial, aeolian and fluvial sedimentary structures formed during the end-Cryogenian, Marinoan glaciation in South Australia; these observations allow us to constrain ancient surface temperatures. We find periglacial sand wedges and associated deformation suggest that ground temperatures were sufficiently warm to allow for ductile deformation of a sandy regolith. The wide range of deformation structures likely indicate the presence of a paleoactive layer that penetrated 2-4 m below the ground surface. These observations, paired with a model of ground temperature forced by solar insolation, constrain the local mean annual surface temperature to within a few degrees of freezing. This temperature constraint matches well with our observations of fluvial deposits, which require temperatures sufficiently warm for surface runoff. Although this estimate coincides with one of the coldest near sea-level tropical temperatures in Earth history, if these structures represent peak Marinaon glacial conditions, they do not support the persistent deep freeze of the snowball Earth hypothesis. Rather, surface temperatures near 0 °C allow for regions of seasonal surface melting, atmosphere-ocean coupling and possible tropical refugia for early metazoans. If instead these structures formed during glacial onset or deglaciation, then they have

The Neoproterozoic Era, from around 1000 to 570 million years ago, witnessed the widespread deposition of Iron Formations (IFs) in close association with global glaciations. These IFs record distinct iron isotope and rare earth element patterns that allow us to reconstruct their depositional environment. The Fulu Formation of South China is a regional example of a global phenomenon. The Fulu was deposited immediately following the breakup of the Supercontinent Rodinia, which provided a restricted rift basin and contributed to an ample supply of iron. Specifically, iron isotopes and rare earth element profiles point to hydrothermally sourced iron in an oxygen-limited environment as the major driver of deposition for the Fulu Formation.

The Neoproterozoic Era was one of major biotic change against a background marked by fluctuations in oceanic and atmospheric chemistry, formation and rifting of the supercontinent Rodinia, and at least two global glaciations (Snowball Earth events). Presented here are three studies of differing aspects of those biological changes. The first is a systematic study of the diverse and well-preserved, organic-walled microfossil assemblage of the Alinya Formation of eastern Officer Basin, Australia. The use of scanning electron microscopy (SEM) revealed an unexpected level of morphological detail not visible in transmitted light microscopy and led to the recognition of new species and emendation of existing species as well as establishment of degradational sequences. In total, thirty-three taxa are described here including nineteen previously named forms, five newly described species and two new combinations. The second study describes the organic-walled microfossil assemblages from five successions that span the first (Sturtian) glaciation (~717 Ma) and interglacial interval (>635 Ma), and integrates those data with a critical evaluation of primary paleontological literature of units deposited from ~850 to 650 Ma. The described successions from Australia and Svalbard record low species richness throughout this interval and when placed in context of all available body fossil data from the mid-Neoproterozoic, indicate global species richness may have decreased much earlier than previously realized. This finding of temporal decoupling between loss of richness and glacial onset suggests the extinctions previously associated with the Snowball Earth glacial events may not have been glacially driven. The last of these three studies provides a broader view of the early to middle Neoproterozoic biosphere (1 Ga to 635 Ma) and describes application of the CONOP correlation and seriation algorithm to a new database of paleontological, geochemical and radiometric data. Paleobiolog

The Neoproterozoic Era, from around 1000 to 570 million years ago, witnessed the widespread deposition of Iron Formations (IFs) in close association with global glaciations. These IFs record distinct iron isotope and rare earth element patterns that allow us to reconstruct their depositional environment. The Fulu Formation of South China is a regional example of a global phenomenon. The Fulu was deposited immediately following the breakup of the Supercontinent Rodinia, which provided a restricted rift basin and contributed to an ample supply of iron. Specifically, iron isotopes and rare earth element profiles point to hydrothermally sourced iron in an oxygen-limited environment as the major driver of deposition for the Fulu Formation.

The Neoproterozoic Era was one of major biotic change against a background marked by fluctuations in oceanic and atmospheric chemistry, formation and rifting of the supercontinent Rodinia, and at least two global glaciations (Snowball Earth events). Presented here are three studies of differing aspects of those biological changes. The first is a systematic study of the diverse and well-preserved, organic-walled microfossil assemblage of the Alinya Formation of eastern Officer Basin, Australia. The use of scanning electron microscopy (SEM) revealed an unexpected level of morphological detail not visible in transmitted light microscopy and led to the recognition of new species and emendation of existing species as well as establishment of degradational sequences. In total, thirty-three taxa are described here including nineteen previously named forms, five newly described species and two new combinations. The second study describes the organic-walled microfossil assemblages from five successions that span the first (Sturtian) glaciation (~717 Ma) and interglacial interval (>635 Ma), and integrates those data with a critical evaluation of primary paleontological literature of units deposited from ~850 to 650 Ma. The described successions from Australia and Svalbard record low species richness throughout this interval and when placed in context of all available body fossil data from the mid-Neoproterozoic, indicate global species richness may have decreased much earlier than previously realized. This finding of temporal decoupling between loss of richness and glacial onset suggests the extinctions previously associated with the Snowball Earth glacial events may not have been glacially driven. The last of these three studies provides a broader view of the early to middle Neoproterozoic biosphere (1 Ga to 635 Ma) and describes application of the CONOP correlation and seriation algorithm to a new database of paleontological, geochemical and radiometric data. Paleobiolog

Intense glaciation during the end of Cryogenian time (~635 million years ago) marks the coldest climate state in Earth history - a time when glacial deposits accumulated at low, tropical paleolatitudes. The leading idea to explain these deposits, the snowball Earth hypothesis, predicts globally frozen surface conditions and subfreezing temperatures, with global climate models placing surface temperatures in the tropics between -20 °C and -60 °C. However, precise paleosurface temperatures based upon geologic constraints have remained elusive and the global severity of the glaciation undetermined. Here we make new geologic observations of tropical periglacial, aeolian and fluvial sedimentary structures formed during the end-Cryogenian, Marinoan glaciation in South Australia; these observations allow us to constrain ancient surface temperatures. We find periglacial sand wedges and associated deformation suggest that ground temperatures were sufficiently warm to allow for ductile deformation of a sandy regolith. The wide range of deformation structures likely indicate the presence of a paleoactive layer that penetrated 2-4 m below the ground surface. These observations, paired with a model of ground temperature forced by solar insolation, constrain the local mean annual surface temperature to within a few degrees of freezing. This temperature constraint matches well with our observations of fluvial deposits, which require temperatures sufficiently warm for surface runoff. Although this estimate coincides with one of the coldest near sea-level tropical temperatures in Earth history, if these structures represent peak Marinaon glacial conditions, they do not support the persistent deep freeze of the snowball Earth hypothesis. Rather, surface temperatures near 0 °C allow for regions of seasonal surface melting, atmosphere-ocean coupling and possible tropical refugia for early metazoans. If instead these structures formed during glacial onset or deglaciation, then they have

Planetary climate can be affected by the interaction of the host star spectral energy distribution with the wavelength-dependent reflectivity of ice and snow. In this study, we explored this effect with a one-dimensional (1-D), line-by-line, radiative transfer model to calculate broadband planetary albedos as input to a seasonally varying, 1-D energy balance climate model. A three-dimensional (3-D) general circulation model was also used to explore the atmosphere's response to changes in incoming stellar radiation, or instellation, and surface albedo. Using this hierarchy of models, we simulated planets covered by ocean, land, and water-ice of varying grain size, with incident radiation from stars of different spectral types. Terrestrial planets orbiting stars with higher near-UV radiation exhibited a stronger ice-albedo feedback. We found that ice extent was much greater on a planet orbiting an F-dwarf star than on a planet orbiting a G-dwarf star at an equivalent flux distance, and that ice-covered conditions occurred on an F-dwarf planet with only a 2% reduction in instellation relative to the present instellation on Earth, assuming fixed CO(2) (present atmospheric level on Earth). A similar planet orbiting the Sun at an equivalent flux distance required an 8% reduction in instellation, while a planet orbiting an M-dwarf star required an additional 19% reduction in instellation to become ice-covered, equivalent to 73% of the modern solar constant. The reduction in instellation must be larger for planets orbiting cooler stars due in large part to the stronger absorption of longer-wavelength radiation by icy surfaces on these planets in addition to stronger absorption by water vapor and CO(2) in their atmospheres, which provides increased downwelling longwave radiation. Lowering the IR and visible-band surface ice and snow albedos for an M-dwarf planet increased the planet's climate stability against changes in instellation and slowed the descent into global ice co

This review paper presents a set of revised global palaeogeographic maps for the 825–540 Ma interval using the latest palaeomagnetic data, along with lithological information for Neoproterozoic sedimentary basins. These maps form the basis for an examination of the relationships between known glacial deposits, palaeolatitude, positions of continental rifting, relative sea-level changes, and major global tectonic events such as supercontinent assembly, breakup and superplume events. This analysis reveals several fundamental palaeogeographic features that will help inform and constrain models for Earth’s climatic and geodynamic evolution during the Neoproterozoic. First, glacial deposits at or near sea level appear to extend from high latitudes into the deep tropics for all three Neoproterozoic ice ages (Sturtian, Marinoan and Gaskiers), although the Gaskiers interval remains very poorly constrained in both palaeomagnetic data and global lithostratigraphic correlations. Second, continental sedimentary environments were dominant in epicratonic basins within Rodinia (>825 Ma to ca. 750 Ma), possibly resulting from both plume/superplume dynamic topography and lower sea-level due to dominantly old oceanic crust. This was also the case at ca. 540 Ma, but at that time the pattern reflects widespread mountain ranges formed during the assembly of Gondwanaland and increasing mean age of global ocean crust.Third, deep-water environments were dominant during the peak stage of Rodinia break-up between ca. 720 Ma and ca. 580 Ma, likely indicating higher sea level due to increased rate of production of newer oceanic crust, plus perhaps the effect of continents drifting away from a weakening superplume. Finally, there is no clear association between continental rifting and the distribution of glacial strata, contradicting models that restrict glacial influence to regions of continental uplift.

The rise in atmospheric oxygen between 2.45 and 2.2 Ga has been linked to the demise of a methane-rich atmosphere and the onset of multiple glaciations, culminating in a possible Snowball Earth. The glacial deposits represent possible global marker horizons, however, their correlation is uncertain because key sedimentary successions are undated, hampering paleoenvironmental reconstructions. Three potentially global glaciations have been proposed based on the correlation of glacial deposits in southern Africa with those in North America. However, it has also been suggested that there were four glaciations and that the youngest was a Snowball Earth event recorded only in South African successions. In situ U–Pb zircon ages for tuffs in southern African and North American successions establish the existence of four glaciations between 2.45 and 2.22 Ga. Geochronological and stratigraphic data demonstrate that the three oldest glaciations predate ~ 2.31 Ga and that the final glaciation, which is only recognized in South Africa, occurred between 2.26 and 2.22 Ga.The new age-calibrated correlations show that a rise in atmospheric oxygen inferred from sulfur isotope data occurred between the second and third glaciations. At 2.31 Ga, the first marine sulfate evaporites were deposited contemporaneously with 13C-enriched carbonates, indicating a direct link between perturbations of the carbon and sulfur cycles and rising atmospheric oxygen. The appearance of “red beds” and oxidized palesols after the third glaciation signals a major increase in atmospheric oxygen levels, which culminated with the fourth glaciation between 2.26 and 2.22 Ga, after which the atmosphere remained irreversibly oxygenated.

The interactive Earth system: biology in geologic, environmental and climate change throughout Earth history. Since life began it has continually shaped and re-shaped the atmosphere, hydrosphere, cryosphere and the solid earth. Subject introduces the concept of "life as a geological agent" and examines the interaction between biology and the earth system during the roughly 4 billion years since life first appeared. Topics include the origin of the solar system and the early Earth atmosphere; the origin and evolution of life and its influence on climate up through and including the modern age and the problem of global warming; the global carbon cycle; and astrobiology.

The interactive Earth system: biology in geologic, environmental and climate change throughout Earth history. Since life began it has continually shaped and re-shaped the atmosphere, hydrosphere, cryosphere and the solid earth. Subject introduces the concept of "life as a geological agent" and examines the interaction between biology and the earth system during the roughly 4 billion years since life first appeared. Topics include the origin of the solar system and the early Earth atmosphere; the origin and evolution of life and its influence on climate up through and including the modern age and the problem of global warming; the global carbon cycle; and astrobiology.

The Neoproterozoic era witnessed at least two severe glaciations and the first emergence of animal phyla. Understanding the triggers for these events relies on the global contextualisation of the prevailing environmental conditions. This in turn requires a solid chronostratigraphic framework which, as yet, remains fragmentary. Here we show that late Neoproterozoic (Ediacaran) marine sediments in the Officer Basin, Australia, deposited during and after a bolide impact (the Acraman event), contain enhanced concentrations of the polycyclic aromatic hydrocarbon coronene, which can be produced by the combustion of biomass. The coincidence of the coronene anomaly with a negative sedimentary carbon isotopic excursion suggests a relationship to combustion processes induced by the Acraman impact. Coronene occurrence at a distance beyond granular impact ejecta, as well as analogies of accompanying phenomena with those linked to the aftermath of the Cretaceous-Tertiary (K-T) extinction event, indicate that pyrogenic compounds formed during the Acraman event are likely to have been deposited across a geographically extensive area. This could provide a valuable chronostratigraphic marker in the form of an Ediacaran molecular ash bed.

This course introduces parallel evolution of life and the environment. Life processes are influenced by chemical and physical processes in the atmosphere, hydrosphere, cryosphere and the solid earth. In turn, life can influence chemical and physical processes on our planet. This course introduces the concept of life as a geological agent and examines the interaction between biology and the earth system during the roughly four billion years since life first appeared.

This course introduces parallel evolution of life and the environment. Life processes are influenced by chemical and physical processes in the atmosphere, hydrosphere, cryosphere and the solid earth. In turn, life can influence chemical and physical processes on our planet. This course introduces the concept of life as a geological agent and examines the interaction between biology and the earth system during the roughly four billion years since life first appeared.

The distributions of 77 Neoproterozoic glacigenic formations are shown on global palaeogeographic maps for 715 Ma (Sturtian), 635 Ma (Marinoan) and 580 Ma (Ediacaran), constructed on grounds independent of palaeoclimatic indicators. The meridional distribution of Sturtian and Marinoan deposits is biased in favour of low palaeolatitudes, whereas Ediacaran deposits are biased in favour of high palaeolatitudes. All carbonate hosted glacigenic formations (n=22) fall within 35 of the palaeoequator. Most (6 of 8) examples of periglacial polygonal sand-wedges occur at palaeolatitudes greater than 30, whereas most (8 of 9) occurrences of large syn-glacial Fe and Fe-Mn deposits lie within 30 of the palaeoequator. Marinoan syndeglacial cap dolostones (n=24) decline in maximum thickness with palaeolatitude, consistent with poleward ice retreat, normal meridional temperature gradients and a small-obliquity orbit. Meridional (N-S) mean orientations of giant wave ripples in Marinoan cap dolostones from different regions (n=10) and absence of zonal (W-E) orientations are consistent with zonal wind-driven waves and not with hurricanes. In general, the results support the validity of the palaeogeographic reconstructions and the pan-glacial character of Sturtian and Marinoan ice ages.

Recently recovered assemblage of late Ediacaran cyanobacteria, phytoplankton and some microfossils of uncertain origin from the subsurface Włodawa Formation on the Lublin Slope in Poland, allowed to extend their stratigraphic ranges and provided a new evidence that more species survived the Cryogenian Period. Numerous other species of unicellular eukaryotes (informally called acritarchs) and prokaryotes (also coenobial and colonial) have been documented in recent years to lived-over to the Ediacaran, enlarging the global list of biota surviving the Neoproterozoic icehouse intervals. This compelling record revives the issue how marine biota could coup with the catastrophic consequences imposed by the global glaciations and/or to what extent the environmental and climatic change reduced the life habitats. For this purpose, the metabolic processes, modes of life and ecologic habitats of the biota are inferred and analyzed. The reviewed biota are autotrophic and aerobic: benthic cyanobacteria, which were solitary and largely colonial, living in functionally complex communities of mat-builders, and planktic and/or facultative benthic eukaryotes, which reproduced also sexually and some had advanced life cycle with alternating vegetative and reproductive generations. The environmental requirements of these microorganisms are well-oxygenated open marine waters in the photic zone, and permanent seafloor substrate for benthic and periodic access to bottom sediment for some planktic species with sexual reproduction to rest the cyst. Such natural habitats must have been preserved throughout the Cryogenian Period, and in a substantial extent (environmental “critical mass”) to sustain viable populations in the lineages that are represented by surviving species. Modern analogues of extraordinary adaptations of diverse biota to extreme conditions have their limitations when applied to the Cryogenian Period. Modern extreme environments (like those in Antarctica) with highly speciali, Neoproterozoic microbial diversification, Neoproterozic Ice Ages

The fossil record of the earliest animals has been enlivened in recent years by a series of spectacular discoveries, including embryos, from the Ediacaran to the Cambrian, but many issues, not least of dating and interpretation, remain controversial. In particular, aspects of taphonomy of the earliest fossils require careful consideration before pronouncements about their affinities. Nevertheless, a reasonable case can now be made for the extension of the fossil record of at least basal animals (sponges and perhaps cnidarians) to a period of time significantly before the beginning of the Cambrian. The Cambrian explosion itself still seems to represent the arrival of the bilaterians, and many new fossils in recent years have added significant data on the origin of the three major bilaterian clades. Why animals appear so late in the fossil record is still unclear, but the recent trend to embrace rising oxygen levels as being the proximate cause remains unproven and may even involve a degree of circularity.

Recently recovered assemblage of late Ediacaran cyanobacteria, phytoplankton and some microfossils of uncertain origin from the subsurface Włodawa Formation on the Lublin Slope in Poland, allowed to extend their stratigraphic ranges and provided a new evidence that more species survived the Cryogenian Period. Numerous other species of unicellular eukaryotes (informally called acritarchs) and prokaryotes (also coenobial and colonial) have been documented in recent years to lived-over to the Ediacaran, enlarging the global list of biota surviving the Neoproterozoic icehouse intervals. This compelling record revives the issue how marine biota could coup with the catastrophic consequences imposed by the global glaciations and/or to what extent the environmental and climatic change reduced the life habitats. For this purpose, the metabolic processes, modes of life and ecologic habitats of the biota are inferred and analyzed. The reviewed biota are autotrophic and aerobic: benthic cyanobacteria, which were solitary and largely colonial, living in functionally complex communities of mat-builders, and planktic and/or facultative benthic eukaryotes, which reproduced also sexually and some had advanced life cycle with alternating vegetative and reproductive generations. The environmental requirements of these microorganisms are well-oxygenated open marine waters in the photic zone, and permanent seafloor substrate for benthic and periodic access to bottom sediment for some planktic species with sexual reproduction to rest the cyst. Such natural habitats must have been preserved throughout the Cryogenian Period, and in a substantial extent (environmental “critical mass”) to sustain viable populations in the lineages that are represented by surviving species. Modern analogues of extraordinary adaptations of diverse biota to extreme conditions have their limitations when applied to the Cryogenian Period. Modern extreme environments (like those in Antarctica) with highly speciali, Neoproterozoic microbial diversification, Neoproterozic Ice Ages

Recently recovered assemblage of late Ediacaran cyanobacteria, phytoplankton and some microfossils of uncertain origin from the subsurface Włodawa Formation on the Lublin Slope in Poland, allowed to extend their stratigraphic ranges and provided a new evidence that more species survived the Cryogenian Period. Numerous other species of unicellular eukaryotes (informally called acritarchs) and prokaryotes (also coenobial and colonial) have been documented in recent years to lived-over to the Ediacaran, enlarging the global list of biota surviving the Neoproterozoic icehouse intervals. This compelling record revives the issue how marine biota could coup with the catastrophic consequences imposed by the global glaciations and/or to what extent the environmental and climatic change reduced the life habitats. For this purpose, the metabolic processes, modes of life and ecologic habitats of the biota are inferred and analyzed. The reviewed biota are autotrophic and aerobic: benthic cyanobacteria, which were solitary and largely colonial, living in functionally complex communities of mat-builders, and planktic and/or facultative benthic eukaryotes, which reproduced also sexually and some had advanced life cycle with alternating vegetative and reproductive generations. The environmental requirements of these microorganisms are well-oxygenated open marine waters in the photic zone, and permanent seafloor substrate for benthic and periodic access to bottom sediment for some planktic species with sexual reproduction to rest the cyst. Such natural habitats must have been preserved throughout the Cryogenian Period, and in a substantial extent (environmental “critical mass”) to sustain viable populations in the lineages that are represented by surviving species. Modern analogues of extraordinary adaptations of diverse biota to extreme conditions have their limitations when applied to the Cryogenian Period. Modern extreme environments (like those in Antarctica) with highly speciali, Neoproterozoic microbial diversification, Neoproterozic Ice Ages

Recently recovered assemblage of late Ediacaran cyanobacteria, phytoplankton and some microfossils of uncertain origin from the subsurface Włodawa Formation on the Lublin Slope in Poland, allowed to extend their stratigraphic ranges and provided a new evidence that more species survived the Cryogenian Period. Numerous other species of unicellular eukaryotes (informally called acritarchs) and prokaryotes (also coenobial and colonial) have been documented in recent years to lived-over to the Ediacaran, enlarging the global list of biota surviving the Neoproterozoic icehouse intervals. This compelling record revives the issue how marine biota could coup with the catastrophic consequences imposed by the global glaciations and/or to what extent the environmental and climatic change reduced the life habitats. For this purpose, the metabolic processes, modes of life and ecologic habitats of the biota are inferred and analyzed. The reviewed biota are autotrophic and aerobic: benthic cyanobacteria, which were solitary and largely colonial, living in functionally complex communities of mat-builders, and planktic and/or facultative benthic eukaryotes, which reproduced also sexually and some had advanced life cycle with alternating vegetative and reproductive generations. The environmental requirements of these microorganisms are well-oxygenated open marine waters in the photic zone, and permanent seafloor substrate for benthic and periodic access to bottom sediment for some planktic species with sexual reproduction to rest the cyst. Such natural habitats must have been preserved throughout the Cryogenian Period, and in a substantial extent (environmental “critical mass”) to sustain viable populations in the lineages that are represented by surviving species. Modern analogues of extraordinary adaptations of diverse biota to extreme conditions have their limitations when applied to the Cryogenian Period. Modern extreme environments (like those in Antarctica) with highly speciali, Neoproterozoic microbial diversification, Neoproterozic Ice Ages

The Upper Neoproterozoic Nantuo and Jiangkou Formations in southern China have commonly been identified as the deposits of glaciations dating back to ~600 Ma and ~720 Ma, belonging to the Marinoan and Sturtian ice-ages, respectively, or the so-called snowball Earth events. In the present study, 44 typical Upper Neoproterozoic to Lower Cambrian sedimentary rock samples, including 16 diamictites, have been collected from 12 stratigraphic sections in Hubei, Hunan, Shanxi, Chongqing, Guizhou and Yunnan Provinces in the Yangtze region, southern China, and analyzed by routine organic geochemical techniques. Except for the diamictites and cap carbonates, most of these rocks have middle to high TOC values of up to 0.16–6.50% in the Cambrian and 0.12–9.37% in the Upper Neoproterozoic rock samples. By contrast, the diamictites and cap carbonates have a TOC range only from 0.01% to 0.13%, 1–2 orders of magnitude lower than those in most of the non-glacial sedimentary rocks, indicating very limited organic productivity in the palaeo-oceanic environment during the snowball Earth era. Phytane and pristane, which are derivatives of Chlorophyll-a, and various steranes, which are biomarkers of eukaryotes, were detected in all the rock samples. There is a tendency for positive correlation between TOC and the concentrations of phytane and/or pristane, therefore, it implies that photosynthetic autotrophs should have been the primary organisms contributing to the sedimentary organic matter in the Yangtze palaeo-ocean.Moreover, the concentrations of phytane plus pristane range from 0.024 ng/g to 0.446 ng/g in most non-glacial sedimentary rocks, and from 0.005 ng/g to 0.076 ng/g in diamictites. The unusually low concentrations of phytane and pristane reveal a very weak photosynthetic process, a restricted euphotic zone and quite limited sunlight within the palaeo-oceanic water column. Even though the productivity of photosynthetic organisms was very low, it can still be inferred that phot