1) The study analyzes the syn-rift architecture and depositional patterns in the Tanjore sub-basin of the Cauvery Basin through seismic facies analysis and integration of well data.
2) Four syn-rift units were identified, representing deposition during different stages of rift evolution - early rift, rift climax, and late rift. Unit 2, deposited during the rift climax stage, has good source rock potential, while Units 3 and 4 from the late rift stage contain favorable reservoir facies.
3) Preliminary 2D petroleum system modeling along a cross-section indicates potential hydrocarbon accumulation areas within the syn-rift sediments.
King's geomorphic model is based on the evolution of idealized hill slopes through four stages - waxing slope, free face, debris slope, and waning slope or pediment. The model involves the parallel retreat of scarps and formation of pediments, resulting in the development of a pediplain landscape over multiple cycles of scarp retreat and pedimentation. Each cycle progresses through youth, mature, and old stages similar to Davis' cycle of erosion. The model was developed based on King's extensive study of landscapes in South Africa.
Davis Theory -William Morris Davis- Geomophology ChapterKaium Chowdhury
William Davis proposed the geographical cycle model to describe the development of landforms over time. The model outlines three stages - youth, maturity, and old age - through which uplifted land passes as erosion shapes the landscape. In the youth stage, steep valleys form through rapid vertical erosion. In maturity, vertical erosion declines as valleys widen, and by old age erosion is primarily lateral as the landscape develops into a low-relief peneplain. Davis' model was influential as a general theory of landform evolution driven by erosion following crustal uplift.
Evolution of Geomorphic theory- Geomorphology ChapterKaium Chowdhury
1. Early theories of landscape evolution included catastrophism and uniformitarianism. Davis later proposed the cycle of erosion, which described fixed stages of landscape development over time.
2. Penck built on Davis's work by proposing ongoing tectonism could influence landscape evolution. He described waxing, uniform, and waning stages of development driven by changing uplift and erosion rates.
3. King further developed these ideas, arguing landscapes evolve through parallel slope retreat and may culminate in a pediment under certain conditions. Modern geomorphology views landscapes as intricate systems influenced by various dynamic factors and processes.
Davis and Penk proposed different models of the cycle of erosion. Davis' model involved three stages - youth, maturity, and old age - where a landscape evolves from high relief to a flat plain over time. Penk emphasized the relationship between uplift and erosion, with landforms resulting from their competition. Later theorists like King and Gilbert built on these ideas but acknowledged no single model explains all landscapes given different environments. While influential, both Davis and Penk's concepts have limitations and underwent criticism regarding assumptions about rates of uplift and erosion.
1. The geographical cycle of erosion recognizes that landscapes undergo planation over time through erosion processes, eventually reducing relief to a minimum.
2. William Davis defined the cycle as having three stages - youth, maturity, and old age - based on changes in erosion rates and landscape morphology.
3. Walther Penck modified Davis' model by proposing that erosion and uplift occur continuously in interaction, and that landscape evolution depends on their relative rates.
Davis Theory -William Morris Davis- Geomophology ChapterKaium Chowdhury
William Morris Davis proposed the concept of the geographical cycle to describe the evolution of landforms over time. The cycle involves three stages - youth, maturity, and old age - as uplifted landmasses are eroded by streams and weathering. In the youth stage, streams rapidly deepen valleys through vertical erosion. In maturity, lateral erosion of valleys widens them, and relief decreases. Finally, in old age erosion is minimal and the landscape evolves into a low-relief peneplain. Davis's model emphasized the role of time in landform development but was criticized for oversimplifying geological processes like upliftment. It remained influential but was later replaced by models considering dynamic equilibrium.
A deep groundwater origin for recurring slope lineae on MarsSérgio Sacani
The recurring slope lineae on Mars have been hypothesized to originate from snow melting, deliquescence, dry flow or shallow
groundwater. Except for the dry flow origin, these hypotheses imply the presence of surficial or near-surface volatiles, placing
the exploration and characterization of potential habitable environments within the reach of existing technology. Here we present observations from the High Resolution Imaging Science Experiment, heat-flow modelling and terrestrial analogues, which
indicate that the source of recurring slope lineae could be natural discharge along geological structures from briny aquifers
within the cryosphere, at depths of approximately 750 m. Spatial correlation between recurring slope lineae source regions and
multi-scale fractures (such as joints and faults) in the southern mid-latitudes and in Valles Marineris suggests that recurring
slope lineae preferably emanate from tectonic and impact-related fractures. We suggest that deep groundwater occasionally
surfaces on Mars in present-day conditions.
1) The study analyzes the syn-rift architecture and depositional patterns in the Tanjore sub-basin of the Cauvery Basin through seismic facies analysis and integration of well data.
2) Four syn-rift units were identified, representing deposition during different stages of rift evolution - early rift, rift climax, and late rift. Unit 2, deposited during the rift climax stage, has good source rock potential, while Units 3 and 4 from the late rift stage contain favorable reservoir facies.
3) Preliminary 2D petroleum system modeling along a cross-section indicates potential hydrocarbon accumulation areas within the syn-rift sediments.
King's geomorphic model is based on the evolution of idealized hill slopes through four stages - waxing slope, free face, debris slope, and waning slope or pediment. The model involves the parallel retreat of scarps and formation of pediments, resulting in the development of a pediplain landscape over multiple cycles of scarp retreat and pedimentation. Each cycle progresses through youth, mature, and old stages similar to Davis' cycle of erosion. The model was developed based on King's extensive study of landscapes in South Africa.
Davis Theory -William Morris Davis- Geomophology ChapterKaium Chowdhury
William Davis proposed the geographical cycle model to describe the development of landforms over time. The model outlines three stages - youth, maturity, and old age - through which uplifted land passes as erosion shapes the landscape. In the youth stage, steep valleys form through rapid vertical erosion. In maturity, vertical erosion declines as valleys widen, and by old age erosion is primarily lateral as the landscape develops into a low-relief peneplain. Davis' model was influential as a general theory of landform evolution driven by erosion following crustal uplift.
Evolution of Geomorphic theory- Geomorphology ChapterKaium Chowdhury
1. Early theories of landscape evolution included catastrophism and uniformitarianism. Davis later proposed the cycle of erosion, which described fixed stages of landscape development over time.
2. Penck built on Davis's work by proposing ongoing tectonism could influence landscape evolution. He described waxing, uniform, and waning stages of development driven by changing uplift and erosion rates.
3. King further developed these ideas, arguing landscapes evolve through parallel slope retreat and may culminate in a pediment under certain conditions. Modern geomorphology views landscapes as intricate systems influenced by various dynamic factors and processes.
Davis and Penk proposed different models of the cycle of erosion. Davis' model involved three stages - youth, maturity, and old age - where a landscape evolves from high relief to a flat plain over time. Penk emphasized the relationship between uplift and erosion, with landforms resulting from their competition. Later theorists like King and Gilbert built on these ideas but acknowledged no single model explains all landscapes given different environments. While influential, both Davis and Penk's concepts have limitations and underwent criticism regarding assumptions about rates of uplift and erosion.
1. The geographical cycle of erosion recognizes that landscapes undergo planation over time through erosion processes, eventually reducing relief to a minimum.
2. William Davis defined the cycle as having three stages - youth, maturity, and old age - based on changes in erosion rates and landscape morphology.
3. Walther Penck modified Davis' model by proposing that erosion and uplift occur continuously in interaction, and that landscape evolution depends on their relative rates.
Davis Theory -William Morris Davis- Geomophology ChapterKaium Chowdhury
William Morris Davis proposed the concept of the geographical cycle to describe the evolution of landforms over time. The cycle involves three stages - youth, maturity, and old age - as uplifted landmasses are eroded by streams and weathering. In the youth stage, streams rapidly deepen valleys through vertical erosion. In maturity, lateral erosion of valleys widens them, and relief decreases. Finally, in old age erosion is minimal and the landscape evolves into a low-relief peneplain. Davis's model emphasized the role of time in landform development but was criticized for oversimplifying geological processes like upliftment. It remained influential but was later replaced by models considering dynamic equilibrium.
A deep groundwater origin for recurring slope lineae on MarsSérgio Sacani
The recurring slope lineae on Mars have been hypothesized to originate from snow melting, deliquescence, dry flow or shallow
groundwater. Except for the dry flow origin, these hypotheses imply the presence of surficial or near-surface volatiles, placing
the exploration and characterization of potential habitable environments within the reach of existing technology. Here we present observations from the High Resolution Imaging Science Experiment, heat-flow modelling and terrestrial analogues, which
indicate that the source of recurring slope lineae could be natural discharge along geological structures from briny aquifers
within the cryosphere, at depths of approximately 750 m. Spatial correlation between recurring slope lineae source regions and
multi-scale fractures (such as joints and faults) in the southern mid-latitudes and in Valles Marineris suggests that recurring
slope lineae preferably emanate from tectonic and impact-related fractures. We suggest that deep groundwater occasionally
surfaces on Mars in present-day conditions.
This document discusses using concepts of chaotic mixing to understand the South American monsoon. It presents a methodology to identify Lagrangian Coherent Structures (LCSs) in atmospheric flows using finite-time Lyapunov exponents calculated from back-trajectories. The method is applied to the South American monsoon to analyze seasonal and intraseasonal mechanisms. Seasonally, LCSs vary in key regions like the ITCZ and SACZ depending on interactions between circulations. Intraseasonally, LCS events are linked to rainfall anomalies during events like the MJO or SALLJ. The placement and orientation of LCSs may influence moisture transport and monsoon rainfall on different timescales.
The document discusses various concepts related to plate tectonics and volcanic landforms. It describes plate tectonics theory including evidence for seafloor spreading and subduction. It also discusses plate boundaries, mechanisms of volcanism, types of volcanic landforms such as shield volcanoes and calderas, and volcanic hazards.
This document discusses sedimentary basins, including their definition, formation, and analysis. Key points:
- Sedimentary basins form in low areas of the crust where sediments accumulate due to tectonic activity that creates relief. They range in size from hundreds of meters to ocean basins.
- Tectonics is the primary control on sedimentation, affecting factors like sediment supply and depositional environment. Sedimentation also influences tectonics by increasing lithospheric loading.
- Basins can be formed by processes including faulting, thermal subsidence of extended lithosphere, and flexural subsidence caused by loading of the lithosphere.
- Analyzing features of sedimentary
Coautor. Presenta análisis de elevación y modelos de una paleolínea de costa abandonada hace 10 ka, al interior del Complejo Volcánico Laguna del Maule. Este complejo presenta la mayor concentración de riolitas postglaciales (<25 ka) del hemisferio sur. La paleolínea registra deformación producto de actividad inflacionaria al interior del complejo. A partir de ésta, se estima el volume de magma inyectado al interior del reservorio <10 ka. Para el artículo completo, favor contactarme.
The document outlines cycles of climatic change during the Quaternary period, including glacial and interglacial periods. It discusses the Eemian/Sangamon interglacial 130,000-115,000 years ago, the Early-Middle Weichselian/Wisconsin glacial period 115,000-50,000 years ago, and the Last Glacial Maximum 20,000-18,000 years ago. During glacial periods, continental ice sheets grew and sea levels dropped globally. Interglacials were warmer with higher sea levels. Reconstructions show the extent of ice sheets and changes in ocean temperatures over this timeframe.
Assessing How Rock Type and Relative Erosion Rate Control the Concentration o...Miguel Frias
While gully density increases with moderate relative uplift rates, this trend does not continue into the highest uplift regions, possibly due to dense vegetation obstructing mapping. Gully density is greater in basins underlain primarily by mudstone versus sandstone/conglomerate, as mudstones are more susceptible to weathering. Relative erosion rate, as approximated by depth of incision, does not significantly impact gully density across the study area. Rock type appears to exert more control on gully formation than relative erosion rate.
This document summarizes the normal cycle of erosion by fluvial processes. It describes the three stages: youth, mature, and old. In the youth stage, the river flows steeply, forming V-shaped valleys, gorges, and waterfalls through vigorous erosion. In the mature stage, the river gradient decreases and deposition begins, forming landforms like meanders, ox-bow lakes, and floodplains. In the old stage, the river gradient is low and deposition dominates, forming deltas at the river's mouth. The ideal cycle ends with the formation of a peneplain, but crustal instability prevents most landscapes from reaching this final stage.
Samec - Regression analysis of relations among main Quaternary environmental ...swenney
This document analyzes relationships between environmental change indicators during the Quaternary period using regression analysis. It uses proxy data from loess/paleosol sequences in China, deep sea sediments in the east Pacific, and ice cores from East Antarctica to represent glacial/interglacial cycles. Exploratory analysis, interpolation, and multiple regression methods were used to analyze relationships between the proxy records over the middle to late Pleistocene. Results found weaker correlations between soil properties and climate cycles compared to other proxies. Logistic regression also suggested temporal variability in relationships between climate change factors and sediment properties.
The document discusses the water cycle and movement of water on and below Earth's surface. It describes key processes like infiltration, transpiration, precipitation, evaporation, and runoff. It also explains surface water features such as streams, valleys, floods, and drainage basins. Finally, it covers groundwater topics like aquifers, wells, springs, and karst topography.
This document summarizes several hypotheses for subsidence at passive continental margins:
1) The gravity loading hypothesis attributes subsidence to sediment loading replacing lower density seawater.
2) The thermal hypothesis proposes that lithospheric cooling after rifting and crustal thinning causes thermal contraction and subsidence.
3) The crustal thinning hypothesis suggests the lower continental crust flows plastically towards the upper mantle during rifting, contributing to subsidence.
A seminar on basin evolution and tectonicsPramoda Raj
This seminar discusses sedimentary basin evolution and tectonics. It introduces sedimentary basin formation and classification, including different basin types that form under extensional, collisional, and transtensional tectonic settings. Specific examples of basin evolution models and controls on relative sea level changes are provided. Important sedimentary basins in India are also outlined.
This study analyzed sediment transport and bed material composition in a 16-mile section of the San Joaquin River in California. Sediment samples were taken from three locations along the river between 2011-2012 during high and low flow periods. Results showed a downstream fining trend in bed material. One location showed coarsening during low flows, possibly due to erosion of fine sediments from floodplains or mining pits during high flows. Rouse number calculations indicated sediment mobility increases with discharge. The study concludes increases in discharge do not necessarily correspond to downstream coarsening of deposited sediments.
1) Glacial Lake Missoula formed during the last ice age when an ice dam blocked the Clark Fork River, causing a huge lake to form. The lake drained catastrophically when the ice dam failed, carving out features like ripple marks and waterfalls.
2) These floods discharged at rates over 600 times the modern Amazon River and formed huge ripple marks up to 30 meters tall. Analysis of sediment layers indicates periods of both low and high energy deposition from the filling and draining of the lakes.
3) Flood waters from Lake Missoula entered a second ice-dammed lake, Glacial Lake Columbia, and found outlets through channels now known as the Channeled Sc
Sedimentary basins form in distinct tectonic settings and can be classified based on their formation mechanism and characteristics. The key basin types include rift basins, which form during continental breakup; foreland basins, which form during continent-continent collisions; and arc-trench basins, which form in subduction zones. Each basin type has features that make it suitable for trapping hydrocarbons, such as thick sediment sequences, varying thermal histories, and structural traps associated with the tectonic setting. Rift basins and foreland basin peripheral bulges in particular are highly prospective for oil and gas accumulations.
Hydraulic fracturing has been inferred to trigger the majority of injection-induced earthquakes in western Canada, in contrast to the midwestern United States where massive saltwater disposal is the dominant triggering mechanism. A template-based earthquake catalog from a seismically active Canadian shale play, combined with comprehensive injection data during a 4-month interval, shows that earthquakes are tightly clustered in space and time near hydraulic fracturing sites. The largest event [moment magnitude (MW) 3.9] occurred several weeks after injection along a fault that appears to extend from the injection zone into crystalline basement. Patterns of seismicity indicate that stress changes during operations can activate fault slip to an offset distance of >1 km, whereas pressurization by hydraulic fracturing into a fault yields episodic seismicity that can persist for months.
This thesis mapped and analyzed Cenozoic sedimentary and volcanic units in Huntington Valley, Nevada to understand the depositional history and crustal deformation in the hanging wall above the west-dipping detachment fault bounding the Ruby Mountains-East Humboldt Range metamorphic core complex. Deposition was minor from the Late Cretaceous to Eocene but accelerated in the Middle Miocene with rapid deposition of the Humboldt Formation. Significant westward tilting occurred between 36.8-31.1 Ma and 31.1-16 Ma, likely associated with normal faulting in the adjacent Piñon Range. The findings support recent work showing that major surface-breaking extension occurred in the Middle Miocene in this region rather
This document provides a review of research on reconstructing Late Quaternary to Holocene paleoenvironments in India based on lake and marine sediments. Several key findings are summarized:
1) Studies of Himalayan lake sediments indicate monsoon fluctuations, with a moderate to strong monsoon around 25-17 ka but generally dry conditions during the Last Glacial Maximum. The early Holocene saw a wet climate while the late Holocene was generally dry.
2) Northwest and western India experienced drying around 4,200 years ago that weakened monsoons and caused the collapse of several civilizations like the Harappans. Other records from this region also show fluctuations in lake levels and salinity over the Late Quatern
This document summarizes research on hydrothermal alteration in volcanic rocks on the south flank of Lassen Volcano in California. An active steam-heated system produces low-temperature alteration near surface, while older inactive systems produced zones of intermediate argillic and propylitic alteration. Over 200 rock samples were collected and analyzed to map alteration mineral distributions. Preliminary results identified zones dominated by clay minerals like illite/smectite, chlorite, and montmorillonite indicating both active and fossil hydrothermal systems affected the area.
-Examined features ranging from valley systems in Margaritifer Sinus to inverted topography in Aeolis/Zephyria Plana
-Studied and analyzed MOLA, THEMIS-VIS, OMEGA, MOC, CRISM, HRSC, and CTX imagery
The integrated study characterized the reservoir quality and stratigraphy of the Mowry Shale and Muddy Sandstone in the Powder River Basin. Five depositional facies were identified in the Muddy Sandstone based on core and well log analysis, with the cleanest reservoir sands found in tidal inlet and channel deposits. The overlying Mowry Shale consisted of three parasequences deposited in a restricted shelf environment. Seismic inversion and lithofacies modeling were used to map the facies distributions across the 3D seismic volume. The results provide insights into the stratigraphic framework and reservoir characteristics of the two plays to better assess their exploration potential.
The age and extent of tropical alpine glaciation in the cordillera blanca per...WilJaIn
The article presents new cosmogenic beryllium-10 (10Be) dating of moraines in the Cordillera Blanca mountain range in Peru to develop a chronology of Pleistocene glacial fluctuations in the tropical Andes. 10Be concentrations were measured from boulders on moraines previously identified as belonging to the Laguna Baja, Rurec, and Cojup stades. The oldest moraines yielded dates older than 400,000 years, indicating past glacial maxima pre-dated the last interglacial period. Younger moraines provided dates of approximately 29,000 and 16,500 years ago, suggesting two separate glacial advances during the last glacial
This document discusses using concepts of chaotic mixing to understand the South American monsoon. It presents a methodology to identify Lagrangian Coherent Structures (LCSs) in atmospheric flows using finite-time Lyapunov exponents calculated from back-trajectories. The method is applied to the South American monsoon to analyze seasonal and intraseasonal mechanisms. Seasonally, LCSs vary in key regions like the ITCZ and SACZ depending on interactions between circulations. Intraseasonally, LCS events are linked to rainfall anomalies during events like the MJO or SALLJ. The placement and orientation of LCSs may influence moisture transport and monsoon rainfall on different timescales.
The document discusses various concepts related to plate tectonics and volcanic landforms. It describes plate tectonics theory including evidence for seafloor spreading and subduction. It also discusses plate boundaries, mechanisms of volcanism, types of volcanic landforms such as shield volcanoes and calderas, and volcanic hazards.
This document discusses sedimentary basins, including their definition, formation, and analysis. Key points:
- Sedimentary basins form in low areas of the crust where sediments accumulate due to tectonic activity that creates relief. They range in size from hundreds of meters to ocean basins.
- Tectonics is the primary control on sedimentation, affecting factors like sediment supply and depositional environment. Sedimentation also influences tectonics by increasing lithospheric loading.
- Basins can be formed by processes including faulting, thermal subsidence of extended lithosphere, and flexural subsidence caused by loading of the lithosphere.
- Analyzing features of sedimentary
Coautor. Presenta análisis de elevación y modelos de una paleolínea de costa abandonada hace 10 ka, al interior del Complejo Volcánico Laguna del Maule. Este complejo presenta la mayor concentración de riolitas postglaciales (<25 ka) del hemisferio sur. La paleolínea registra deformación producto de actividad inflacionaria al interior del complejo. A partir de ésta, se estima el volume de magma inyectado al interior del reservorio <10 ka. Para el artículo completo, favor contactarme.
The document outlines cycles of climatic change during the Quaternary period, including glacial and interglacial periods. It discusses the Eemian/Sangamon interglacial 130,000-115,000 years ago, the Early-Middle Weichselian/Wisconsin glacial period 115,000-50,000 years ago, and the Last Glacial Maximum 20,000-18,000 years ago. During glacial periods, continental ice sheets grew and sea levels dropped globally. Interglacials were warmer with higher sea levels. Reconstructions show the extent of ice sheets and changes in ocean temperatures over this timeframe.
Assessing How Rock Type and Relative Erosion Rate Control the Concentration o...Miguel Frias
While gully density increases with moderate relative uplift rates, this trend does not continue into the highest uplift regions, possibly due to dense vegetation obstructing mapping. Gully density is greater in basins underlain primarily by mudstone versus sandstone/conglomerate, as mudstones are more susceptible to weathering. Relative erosion rate, as approximated by depth of incision, does not significantly impact gully density across the study area. Rock type appears to exert more control on gully formation than relative erosion rate.
This document summarizes the normal cycle of erosion by fluvial processes. It describes the three stages: youth, mature, and old. In the youth stage, the river flows steeply, forming V-shaped valleys, gorges, and waterfalls through vigorous erosion. In the mature stage, the river gradient decreases and deposition begins, forming landforms like meanders, ox-bow lakes, and floodplains. In the old stage, the river gradient is low and deposition dominates, forming deltas at the river's mouth. The ideal cycle ends with the formation of a peneplain, but crustal instability prevents most landscapes from reaching this final stage.
Samec - Regression analysis of relations among main Quaternary environmental ...swenney
This document analyzes relationships between environmental change indicators during the Quaternary period using regression analysis. It uses proxy data from loess/paleosol sequences in China, deep sea sediments in the east Pacific, and ice cores from East Antarctica to represent glacial/interglacial cycles. Exploratory analysis, interpolation, and multiple regression methods were used to analyze relationships between the proxy records over the middle to late Pleistocene. Results found weaker correlations between soil properties and climate cycles compared to other proxies. Logistic regression also suggested temporal variability in relationships between climate change factors and sediment properties.
The document discusses the water cycle and movement of water on and below Earth's surface. It describes key processes like infiltration, transpiration, precipitation, evaporation, and runoff. It also explains surface water features such as streams, valleys, floods, and drainage basins. Finally, it covers groundwater topics like aquifers, wells, springs, and karst topography.
This document summarizes several hypotheses for subsidence at passive continental margins:
1) The gravity loading hypothesis attributes subsidence to sediment loading replacing lower density seawater.
2) The thermal hypothesis proposes that lithospheric cooling after rifting and crustal thinning causes thermal contraction and subsidence.
3) The crustal thinning hypothesis suggests the lower continental crust flows plastically towards the upper mantle during rifting, contributing to subsidence.
A seminar on basin evolution and tectonicsPramoda Raj
This seminar discusses sedimentary basin evolution and tectonics. It introduces sedimentary basin formation and classification, including different basin types that form under extensional, collisional, and transtensional tectonic settings. Specific examples of basin evolution models and controls on relative sea level changes are provided. Important sedimentary basins in India are also outlined.
This study analyzed sediment transport and bed material composition in a 16-mile section of the San Joaquin River in California. Sediment samples were taken from three locations along the river between 2011-2012 during high and low flow periods. Results showed a downstream fining trend in bed material. One location showed coarsening during low flows, possibly due to erosion of fine sediments from floodplains or mining pits during high flows. Rouse number calculations indicated sediment mobility increases with discharge. The study concludes increases in discharge do not necessarily correspond to downstream coarsening of deposited sediments.
1) Glacial Lake Missoula formed during the last ice age when an ice dam blocked the Clark Fork River, causing a huge lake to form. The lake drained catastrophically when the ice dam failed, carving out features like ripple marks and waterfalls.
2) These floods discharged at rates over 600 times the modern Amazon River and formed huge ripple marks up to 30 meters tall. Analysis of sediment layers indicates periods of both low and high energy deposition from the filling and draining of the lakes.
3) Flood waters from Lake Missoula entered a second ice-dammed lake, Glacial Lake Columbia, and found outlets through channels now known as the Channeled Sc
Sedimentary basins form in distinct tectonic settings and can be classified based on their formation mechanism and characteristics. The key basin types include rift basins, which form during continental breakup; foreland basins, which form during continent-continent collisions; and arc-trench basins, which form in subduction zones. Each basin type has features that make it suitable for trapping hydrocarbons, such as thick sediment sequences, varying thermal histories, and structural traps associated with the tectonic setting. Rift basins and foreland basin peripheral bulges in particular are highly prospective for oil and gas accumulations.
Hydraulic fracturing has been inferred to trigger the majority of injection-induced earthquakes in western Canada, in contrast to the midwestern United States where massive saltwater disposal is the dominant triggering mechanism. A template-based earthquake catalog from a seismically active Canadian shale play, combined with comprehensive injection data during a 4-month interval, shows that earthquakes are tightly clustered in space and time near hydraulic fracturing sites. The largest event [moment magnitude (MW) 3.9] occurred several weeks after injection along a fault that appears to extend from the injection zone into crystalline basement. Patterns of seismicity indicate that stress changes during operations can activate fault slip to an offset distance of >1 km, whereas pressurization by hydraulic fracturing into a fault yields episodic seismicity that can persist for months.
This thesis mapped and analyzed Cenozoic sedimentary and volcanic units in Huntington Valley, Nevada to understand the depositional history and crustal deformation in the hanging wall above the west-dipping detachment fault bounding the Ruby Mountains-East Humboldt Range metamorphic core complex. Deposition was minor from the Late Cretaceous to Eocene but accelerated in the Middle Miocene with rapid deposition of the Humboldt Formation. Significant westward tilting occurred between 36.8-31.1 Ma and 31.1-16 Ma, likely associated with normal faulting in the adjacent Piñon Range. The findings support recent work showing that major surface-breaking extension occurred in the Middle Miocene in this region rather
This document provides a review of research on reconstructing Late Quaternary to Holocene paleoenvironments in India based on lake and marine sediments. Several key findings are summarized:
1) Studies of Himalayan lake sediments indicate monsoon fluctuations, with a moderate to strong monsoon around 25-17 ka but generally dry conditions during the Last Glacial Maximum. The early Holocene saw a wet climate while the late Holocene was generally dry.
2) Northwest and western India experienced drying around 4,200 years ago that weakened monsoons and caused the collapse of several civilizations like the Harappans. Other records from this region also show fluctuations in lake levels and salinity over the Late Quatern
This document summarizes research on hydrothermal alteration in volcanic rocks on the south flank of Lassen Volcano in California. An active steam-heated system produces low-temperature alteration near surface, while older inactive systems produced zones of intermediate argillic and propylitic alteration. Over 200 rock samples were collected and analyzed to map alteration mineral distributions. Preliminary results identified zones dominated by clay minerals like illite/smectite, chlorite, and montmorillonite indicating both active and fossil hydrothermal systems affected the area.
-Examined features ranging from valley systems in Margaritifer Sinus to inverted topography in Aeolis/Zephyria Plana
-Studied and analyzed MOLA, THEMIS-VIS, OMEGA, MOC, CRISM, HRSC, and CTX imagery
The integrated study characterized the reservoir quality and stratigraphy of the Mowry Shale and Muddy Sandstone in the Powder River Basin. Five depositional facies were identified in the Muddy Sandstone based on core and well log analysis, with the cleanest reservoir sands found in tidal inlet and channel deposits. The overlying Mowry Shale consisted of three parasequences deposited in a restricted shelf environment. Seismic inversion and lithofacies modeling were used to map the facies distributions across the 3D seismic volume. The results provide insights into the stratigraphic framework and reservoir characteristics of the two plays to better assess their exploration potential.
The age and extent of tropical alpine glaciation in the cordillera blanca per...WilJaIn
The article presents new cosmogenic beryllium-10 (10Be) dating of moraines in the Cordillera Blanca mountain range in Peru to develop a chronology of Pleistocene glacial fluctuations in the tropical Andes. 10Be concentrations were measured from boulders on moraines previously identified as belonging to the Laguna Baja, Rurec, and Cojup stades. The oldest moraines yielded dates older than 400,000 years, indicating past glacial maxima pre-dated the last interglacial period. Younger moraines provided dates of approximately 29,000 and 16,500 years ago, suggesting two separate glacial advances during the last glacial
The document discusses evidence that supports the existence of ancient supercontinents. It describes geological studies in Africa that have found similarities in rock formations and drainage patterns across the continent, indicating the landmasses were once joined. Specifically, research on the African Rift Valley has uncovered matching volcanic rocks and river systems on either side of the rift that align with the theory of continental drift. Additionally, the same alkaline rock formations found in Africa are also seen in the boundaries of other ancient continents like Greenland and India, providing further evidence they were once attached as part of a supercontinent.
This document summarizes research on the Yellowstone hotspot and the Yellowstone-Snake River Plain volcanic system. Key points include:
1) The linear progression of increasingly older silicic volcanic centers along the Snake River Plain provides evidence of the track of the Yellowstone hotspot as the North American plate moved over it.
2) Features like elevated topography, seismicity, and normal faulting surround the aseismic Snake River Plain in a "bow-wave" pattern, relating to the effects of the hotspot.
3) Geophysical data like low seismic velocities, high heat flow, and geoid anomalies provide further evidence that the Yellowstone system is fed by a mantle plume originating hundreds
This document summarizes a study of fluid exchange between a subducting slab and mantle wedge in the Guatemala Suture Zone. Samples of schist, jadeitite, and eclogite were analyzed to understand the chemical composition of the mantle wedge and subducting slab. Zoning in mica crystals was examined using an optical microscope, electron probe microanalysis, and laser ablation-ICPMS to provide a chemical history of fluid events. Zoning was observed in mica from the schist and jadeitite samples but not the eclogite, suggesting the eclogite experienced fewer fluid events. Analyzing mica zoning provides insight into the chemical exchange between subducting slabs and mantle wedges.
Formation of lunar surface water associated with high-energy electrons in Ear...Sérgio Sacani
Solar wind implantation is thought to be one of the primary mechanisms in
the formation of water (OH/H2O) on the surface of the Moon and possibly
on the surface of other airless bodies. The lunar nearside spends ~27% of
its daytime in Earth’s magnetotail where the solar wind flux is reduced
by as much as ~99%. However, no correlated decrease in surficial water
content has yet been seen on the lunar nearside. Here we report abundance
observations of lunar surficial water on the nearside at different stages
during the Moon’s passage through Earth’s magnetotail. We find that the
water abundance at lunar mid-latitudes substantially increases in the dusk
and dawn magnetosheath when the solar wind flux increases, yet remains
nearly constant across the central magnetotail. We suggest that although
we have confirmed the importance of the solar wind as a major source of
fast water production on the Moon, hitherto unobserved properties of the
plasma sheet properties may also play an important role.
The divergent fates of primitive hydrospheric water on Earth and MarsSérgio Sacani
The document summarizes research comparing how Earth and Mars differently sequestered early surface water into their mantles. It finds that hydrated Martian basalts can structurally bind about 25% more water than terrestrial basalts, and retain it to greater depths within Mars. Calculations suggest over 9% of the Martian mantle may contain hydrous minerals from surface reactions, versus only about 4% for Earth's mantle. Additionally, hydrated Martian crust experiences little density change upon hydration or dehydration, allowing efficient overplating and burial in Mars' early stagnant-lid tectonic regime. This provided an important sink for Martian surface water and a mechanism for oxidizing its mantle. In contrast, Earth
This document describes experiments simulating volcanic flooding on the Moon using lunar topography data. Three similarly sized regions were artificially flooded: 1) heavily cratered terrain, 2) Hertzsprung basin, and 3) the Central Highlands. As flooding progressed, small craters were buried first followed by larger craters. Comparing the results from point source and ubiquitous flooding showed little difference in the volume of lava added or changes to crater size distributions over time. The experiments provide insights into estimating lava volumes involved in large scale resurfacing events on terrestrial planets.
This document summarizes active continental margins, where a continental plate overrides an oceanic plate being subducted. It focuses on the Andes as the archetypal example, describing three volcanic zones (northern, central, southern). The central zone contains thicker Precambrian crust and produces more silica-rich magmas compared to island arcs. Active volcanism occurs where subduction is steep (~30°) but not where aseismic ridges cause shallow subduction (<10°). Magmas result from mantle and crustal melting, interacting with continental crust, giving them distinct geochemical signatures. Large batholith belts were emplaced during periods of uplift and erosion when subduction shallows.
In situ radiometric_and_exposure_age_dating_of_the_martian_surfaceSérgio Sacani
The document summarizes research on the Sheepbed mudstone sample collected by the Curiosity rover in Gale crater on Mars. Key points:
- Potassium-argon dating of the mudstone yielded an age of 4.21 ± 0.35 billion years, consistent with the expected antiquity of rocks in Gale crater.
- Cosmogenic neon-21, helium-3, and argon-36 isotopes in the mudstone yielded concordant surface exposure ages of 78 ± 30 million years, indicating recent exposure by wind erosion rather than during initial transport and deposition.
- The mudstone's composition and mineralogy suggest it has not been heated above 200°C and may preserve
1) The study mapped an area in southern Margaritifer Terra, Mars containing 5 large impact craters to understand the geologic history and role of water.
2) The craters showed evidence of alluvial fans, aeolian deposits, and fluvial erosion indicating water once flowed on the surface. Older fans within Crater 1 suggest the presence of an ancient lake.
3) Overall, the features revealed the area experienced impact cratering, mass wasting, and fluvial erosion and deposition from water in the past like rainfall, snowmelt, or groundwater. Mapping helped decipher the complex geologic processes that shaped the landscape over time.
This study analyzes samples from the 2010 and 2006 eruptions of Mount Merapi in Indonesia to understand the processes leading to the much larger 2010 eruption. Petrological analysis reveals complex magmatic processes involving multiple storage zones within the volcano. A deep reservoir at 30 km likely generated basaltic andesite magmas. Shallower zones at 13 km and below 10 km recorded decreasing water contents and gas exsolution. The 2010 eruption was driven by a much larger intrusion of gas-rich magma from depth that overwhelmed shallower crystal-rich zones, allowing rapid ascent with gases intact. This contrasts 2006 where intrusions were smaller and slowed by crystals, filtering gases.
The Wyoming Province is a unique Archean craton characterized by several key features: (1) it has remnants of crust as old as 4.0 Ga, with zircons containing xenocrysts up to 3.8 Ga old; (2) its lower crust is unusually thick, up to 25 km, and has persisted largely unchanged for nearly 3.0 Ga; (3) its Mesoarchean magmatic record shows involvement with even older crust, evidenced by its distinctive Pb isotope signatures.
The Wyoming Province is a unique Archean craton characterized by several key features: (1) it has evidence of ancient crust dating back to 4.0-3.8 Ga in the form of xenocrysts and detrital zircons, (2) it has a thick, high velocity lower crust and keel that has resisted subduction for nearly 3.0 Ga, and (3) its Mesoarchean magmatic record shows involvement with even older crust through its distinct Pb isotopic signatures.
This document provides information on Prospecting License C-66 located in northwest Guyana. The license area shows potential for gold mineralization. Historical mining in the area has recovered gold from alluvial deposits and quartz veins. Geological mapping indicates the license area contains metasediments and metavolcanics from the Lower Proterozoic Mazaruni Supergroup intruded by younger granites. Limited geochemical sampling within the license area has identified one anomalous area with gold values between 25-38 ppb. The regional geology and structures controlling gold mineralization in the area are not well defined due to thick tropical weathering and limited exposure and data.
The document provides an overview of mantle plumes and hotspots. It discusses that mantle plumes are columns of hot material rising from deep within the mantle, and hotspots are the surface expression of these plumes seen as volcanic regions. Hotspots have distinct geochemical signatures and are unrelated to tectonic plate boundaries. They can form hotspot tracks as the tectonic plate moves over them, leaving age-progressive volcanic chains. While hotspots were thought to be fixed in the mantle, evidence now suggests they may move slowly relative to each other over geologic timescales. Mantle plumes provide an explanation for various volcanic and tectonic phenomena seen in the interiors of tectonic plates.
This thesis studied the history of dune activity along the Elkhorn River in northeastern Nebraska. Twenty-four optical luminescence ages from dunes revealed periods of activity less than 120 years ago, around 410-630 years ago, around 1000 years ago, and around 3,800 to 5,800 years ago. These periods align with some but not all major dune activation events in the Nebraska Sand Hills. The dunes likely formed due to drought-induced changes in sediment supply from the Elkhorn River, demonstrating that megadroughts had impacts beyond the Sand Hills.
The document summarizes volcanic activity in northern central Peru from the Cretaceous to present. It describes three groups of volcanic rocks separated in time and space: 1) The Albian Casma Group volcanic rocks which filled the Casma Basin in a deep sea environment during crustal extension. 2) The Calipuy Group volcanics from 53-15 Ma erupted during a period of extension. 3) The younger Miocene-Pliocene Yungay volcanic rocks associated with major batholith intrusion during transtensional faulting. Although the volcanic rocks are calc-alkaline, crustal extension played a fundamental role in their genesis, whereas their relation to contemporaneous subduction is less clear.
Western US volcanism due to intruding oceanic mantle driven by ancient Farall...Sérgio Sacani
The origin of late Cenozoic intraplate volcanism over the western United States is debated. One important reason is the lack
of a clear understanding of the mantle dynamics during this volcanic history. Here we reconstruct the mantle thermal states
beneath North America since 20 million years ago using a hybrid inverse geodynamic model with data assimilation. The model
simultaneously satisfies the past subduction kinematics, present mantle tomographic image and the volcanic history. We find
that volcanism in both the Yellowstone volcanic province and the Basin and Range province corresponds to a similar eastwardintruding
mantle derived from beneath the Pacific Ocean and driven mostly by the sinking Farallon slab below the centraleastern
United States. The hot mantle that forms the Columbia River flood basalt and subsequent Yellowstone–Newberry
hotspot tracks first enters the western United States through tears within the Juan de Fuca slab. Subsequent coexistence of the
westward asthenospheric flow above the retreating Juan de Fuca slab and eastward-propagating mantle beyond the back-arc
region reproduces the bifurcating hotspot chains. A similar but weaker heat source intrudes below the Basin and Range around
the southern edge of the slab, and can explain the diffuse basaltic volcanism in this region. According to our models, the putative
Yellowstone plume contributes little to the formation of the Yellowstone volcanic province.
Similar to Vanessa Swenton's Sigma Xi 2021 Research Showcase PowerPoint Presentation (20)
ESA/ACT Science Coffee: Diego Blas - Gravitational wave detection with orbita...Advanced-Concepts-Team
Presentation in the Science Coffee of the Advanced Concepts Team of the European Space Agency on the 07.06.2024.
Speaker: Diego Blas (IFAE/ICREA)
Title: Gravitational wave detection with orbital motion of Moon and artificial
Abstract:
In this talk I will describe some recent ideas to find gravitational waves from supermassive black holes or of primordial origin by studying their secular effect on the orbital motion of the Moon or satellites that are laser ranged.
Authoring a personal GPT for your research and practice: How we created the Q...Leonel Morgado
Thematic analysis in qualitative research is a time-consuming and systematic task, typically done using teams. Team members must ground their activities on common understandings of the major concepts underlying the thematic analysis, and define criteria for its development. However, conceptual misunderstandings, equivocations, and lack of adherence to criteria are challenges to the quality and speed of this process. Given the distributed and uncertain nature of this process, we wondered if the tasks in thematic analysis could be supported by readily available artificial intelligence chatbots. Our early efforts point to potential benefits: not just saving time in the coding process but better adherence to criteria and grounding, by increasing triangulation between humans and artificial intelligence. This tutorial will provide a description and demonstration of the process we followed, as two academic researchers, to develop a custom ChatGPT to assist with qualitative coding in the thematic data analysis process of immersive learning accounts in a survey of the academic literature: QUAL-E Immersive Learning Thematic Analysis Helper. In the hands-on time, participants will try out QUAL-E and develop their ideas for their own qualitative coding ChatGPT. Participants that have the paid ChatGPT Plus subscription can create a draft of their assistants. The organizers will provide course materials and slide deck that participants will be able to utilize to continue development of their custom GPT. The paid subscription to ChatGPT Plus is not required to participate in this workshop, just for trying out personal GPTs during it.
The technology uses reclaimed CO₂ as the dyeing medium in a closed loop process. When pressurized, CO₂ becomes supercritical (SC-CO₂). In this state CO₂ has a very high solvent power, allowing the dye to dissolve easily.
Describing and Interpreting an Immersive Learning Case with the Immersion Cub...Leonel Morgado
Current descriptions of immersive learning cases are often difficult or impossible to compare. This is due to a myriad of different options on what details to include, which aspects are relevant, and on the descriptive approaches employed. Also, these aspects often combine very specific details with more general guidelines or indicate intents and rationales without clarifying their implementation. In this paper we provide a method to describe immersive learning cases that is structured to enable comparisons, yet flexible enough to allow researchers and practitioners to decide which aspects to include. This method leverages a taxonomy that classifies educational aspects at three levels (uses, practices, and strategies) and then utilizes two frameworks, the Immersive Learning Brain and the Immersion Cube, to enable a structured description and interpretation of immersive learning cases. The method is then demonstrated on a published immersive learning case on training for wind turbine maintenance using virtual reality. Applying the method results in a structured artifact, the Immersive Learning Case Sheet, that tags the case with its proximal uses, practices, and strategies, and refines the free text case description to ensure that matching details are included. This contribution is thus a case description method in support of future comparative research of immersive learning cases. We then discuss how the resulting description and interpretation can be leveraged to change immersion learning cases, by enriching them (considering low-effort changes or additions) or innovating (exploring more challenging avenues of transformation). The method holds significant promise to support better-grounded research in immersive learning.
When I was asked to give a companion lecture in support of ‘The Philosophy of Science’ (https://shorturl.at/4pUXz) I decided not to walk through the detail of the many methodologies in order of use. Instead, I chose to employ a long standing, and ongoing, scientific development as an exemplar. And so, I chose the ever evolving story of Thermodynamics as a scientific investigation at its best.
Conducted over a period of >200 years, Thermodynamics R&D, and application, benefitted from the highest levels of professionalism, collaboration, and technical thoroughness. New layers of application, methodology, and practice were made possible by the progressive advance of technology. In turn, this has seen measurement and modelling accuracy continually improved at a micro and macro level.
Perhaps most importantly, Thermodynamics rapidly became a primary tool in the advance of applied science/engineering/technology, spanning micro-tech, to aerospace and cosmology. I can think of no better a story to illustrate the breadth of scientific methodologies and applications at their best.
The cost of acquiring information by natural selectionCarl Bergstrom
This is a short talk that I gave at the Banff International Research Station workshop on Modeling and Theory in Population Biology. The idea is to try to understand how the burden of natural selection relates to the amount of information that selection puts into the genome.
It's based on the first part of this research paper:
The cost of information acquisition by natural selection
Ryan Seamus McGee, Olivia Kosterlitz, Artem Kaznatcheev, Benjamin Kerr, Carl T. Bergstrom
bioRxiv 2022.07.02.498577; doi: https://doi.org/10.1101/2022.07.02.498577
hematic appreciation test is a psychological assessment tool used to measure an individual's appreciation and understanding of specific themes or topics. This test helps to evaluate an individual's ability to connect different ideas and concepts within a given theme, as well as their overall comprehension and interpretation skills. The results of the test can provide valuable insights into an individual's cognitive abilities, creativity, and critical thinking skills
The debris of the ‘last major merger’ is dynamically youngSérgio Sacani
The Milky Way’s (MW) inner stellar halo contains an [Fe/H]-rich component with highly eccentric orbits, often referred to as the
‘last major merger.’ Hypotheses for the origin of this component include Gaia-Sausage/Enceladus (GSE), where the progenitor
collided with the MW proto-disc 8–11 Gyr ago, and the Virgo Radial Merger (VRM), where the progenitor collided with the
MW disc within the last 3 Gyr. These two scenarios make different predictions about observable structure in local phase space,
because the morphology of debris depends on how long it has had to phase mix. The recently identified phase-space folds in Gaia
DR3 have positive caustic velocities, making them fundamentally different than the phase-mixed chevrons found in simulations
at late times. Roughly 20 per cent of the stars in the prograde local stellar halo are associated with the observed caustics. Based
on a simple phase-mixing model, the observed number of caustics are consistent with a merger that occurred 1–2 Gyr ago.
We also compare the observed phase-space distribution to FIRE-2 Latte simulations of GSE-like mergers, using a quantitative
measurement of phase mixing (2D causticality). The observed local phase-space distribution best matches the simulated data
1–2 Gyr after collision, and certainly not later than 3 Gyr. This is further evidence that the progenitor of the ‘last major merger’
did not collide with the MW proto-disc at early times, as is thought for the GSE, but instead collided with the MW disc within
the last few Gyr, consistent with the body of work surrounding the VRM.
Vanessa Swenton's Sigma Xi 2021 Research Showcase PowerPoint Presentation
1. Assessing the space
and time trends in
Miocene co-CRBG
rhyolites and rhyolites
of the High Lava Plains
trend in eastern
Oregon
SIGMA XI RESEARCH PRESENTATION 2021
VANESSA SWENTON
2. Miocene rhyolite
volcanism of the
Pacific NW can be
summarized as
occurring in 3 primary
volcanic fields:
1) co-Columbia River
Basalt Group
(CRBG) rhyolites
2) Rhyolites of the
Yellowstone-Snake
River Plain (YSRP)
track
3) Rhyolites of the
High Lava Plains
(HLP)
1
3. co-CRBG rhyolites
~17.3–15 Ma
Y-SRP rhyolites
14 Ma to present
co-CRBG rhyolites
are a result
ponding and
radially spreading
of rising mantle
plume material
NE-younging YSRP
rhyolites are a
product of the
North American
plate migrating
over the stationary
Yellowstone plume
tail
2
4. co-CRBG rhyolites
~17.3–15 Ma
HLP rhyolites
<12 Ma
Numerous models
attempt to explain
the NW-younging
HLP rhyolites as being
a result of either:
Buoyancy-driven
westward plume
spreading
Or
Evolving dynamics of
the subducting
Cascadia slab (no
plume involvement)
Y-SRP rhyolites
14 Ma to present
3
5. Jordan et al. (2004)
Camp (2019); Camp and Wells (2021)
Examples of HLP Models that
Involve the Plume
Plume material ponds around
the craton boundary beneath
the North American plate
producing co-CRBG rhyolites
Buoyancy-driven westward
spreading of plume material melts
the crust, producing HLP rhyolites
4
6. Examples of HLP Models that
do Not Involve the Plume
Ford et al. (2013)
Hawley and Allen (2019)
Mantle convection is induced by
slab rollback and trench
migration, which heats the crust
to produce rhyolites
Mantle rises buoyantly through a
westward propagating slab tear,
where it then melts the crust to
product HLP rhyolites
5
7. A lack of regional
~15–12 Ma
rhyolites (an
apparent ~3 m.y.
eruptive hiatus)
and their limited
spatial overlap led
previous
researchers to
conclude HLP and
co-CRBG rhyolite
provinces were a
result of separate
and distinct
magmatic and
tectonic processes
6
co-CRBG rhyolites
~17.3–15 Ma
HLP rhyolites
<12 Ma
8. Compilation mapping from Ferns et al. (1993a; 1993b), Greene et al. (1972), Webb et al. (2018)
However, this interpretation was developed with an incomplete
dataset, as ~33 of the total ~50 rhyolite eruptive centers in the area
where the 2 provinces overlap had yet to be dated.
Thus, the
relationship of
the two
provinces
remained
unclear.
7
9. 8
Geochemical data (XRF) from previous
studies* reveals the significant compositional
variability among regional rhyolites.
There does not appear to be a strong correlation
between age and composition among regional
rhyolites.
With a limited geochemical and geochronological
dataset, it is uncertain whether there is a definitive
distinction between older, co-CRBG rhyolites and
younger rhyolites of the HLP.
*Compilation of XRF data from numerous previous studies
Blue symbols = >15 Ma
Yellow symbols = <12 Ma
Red symbols = Precise age unknown
All centers are rhyolite lavas unless otherwise noted in legend.
10. Our goal was to fill critical gaps in the regional
comprehensive space-time record in order to refine current
models or generate a new model that accurately describes
the processes that generated the HLP volcanic trend and
the relationship of the HLP and co-CRBG provinces.
9
11. The Yellowstone plume is most likely involved
in CRBG volcanism, Earth’s youngest flood
basalt province.
Understanding the magmatic and tectonic
processes involved in generating co-CRBG and
HLP rhyolites has the potential to refine our
understanding of the dynamics of mantle
plume spreading and plume-lithosphere
interactions, a process that impacts our planet
at a global scale.
10
12. Whole rock geochemical signatures
via XRF and ICP-MS at WSU**
SEM and Petrography at PSU**
Precise 40Ar/39Ar dating of sanidine phenocrysts at OSU
Methods
These data on 26 previously unanalyzed
rhyolites* allowed us to correlate or distinguish
rhyolites and complete the comprehensive
space-time record of regional rhyolites.
*Ages are pending for 3 additional rhyolites
**Geochemical data is a component of this chapter of my dissertation research
but is the primary focus of a separate publication and is not discussed in this
presentation.
11
13. A Previously Unrecognized Periodicity in Regional Miocene Rhyolite Volcanism
Compilation of ages from this study and numerous previous studies
16.3–14.4 Ma
Associated with CRBG eruptions
12.1–9.6 Ma
Emplaced primarily where HLP province
and co-CRBG rhyolites overlap
7.3–5.2 Ma
In the central and westernmost HLP
12
Cumulative Age Distribution of 100 Distinct Regional Silicic Centers
Relatively gradual onset period starting at ~17.5 Ma
Relatively gradual onset period starting at ~9.0 Ma
Addition of our new ages reveals 3 distinct
pulses of rhyolite volcanism
14. A Previously Unrecognized Periodicity in Regional Miocene Rhyolite Volcanism
Compilation of ages from this study and
numerous previous studies
16.3–14.4 Ma
Peak eruptive activity began
with the 16.29 Ma* Beulah
Reservoir rhyolite and
waned after the 14.37 Ma*
Strawberry Rhyolite
12.1–9.6 Ma
Initiated with
eruption of the
12.05 Ma* Beaty’s
Butte rhyolite and
waned with eruption
of the 9.63 Ma*
Devine Canyon Tuff
7.3–5.2 Ma
Peak eruptive activity
began with eruption of the
7.28 Ma* ‘Horse
Mountain, north’ rhyolite
and waned after eruption
of the 5.17 Ma* Bug Butte
top rhyolite
13
We refined the previously observed ~16.5–15
Ma eruptive episode to 16.3–14.4 Ma and
~15–12 Ma eruptive hiatus to 14.4–12.1 Ma
~2.3 m.y.
eruptive
hiatus
~0.6 m.y.
eruptive
hiatus
*age from a previous study
15. Observed lack of an expected pulse of mafic volcanism ~13–11 Ma
Compilation of ages from this study and numerous previous studies
Regional mafic volcanism
Bar height (y-axis) of no assigned value
Voluminous
outpouring of CRBG
flood basalts
Dispersed eruptions of the Owyhee
Basalts, Tims Peak basalt, and
Keeney Sequence
Episodes of basalt volcanism within the central and
western HLP
Unlike the 16.3–14.4 Ma rhyolite episode, there is no prominent pulse of
mafic magmatism immediately prior to onset of 12.1–9.6 Ma rhyolites
(Bin width of 0.5 m.y.)
14
16. New Regional
Miocene Rhyolite
Eruptive Center
Compilation Map
Our new ages conform
to the previously
known NW-younging
HLP trend.
Most of our new ages
are within the 12.1–9.6
Ma episode and lie
within and just outside
of the easternmost
extent of the HLP
province.
Sampling area for
this study
15
Compilation of mapping from numerous
sources. Compilation of ages from this
study and numerous previous studies.
17. A New Model for Miocene Rhyolite Volcanism of eastern Oregon
A new model is needed to address:
1) The ~2.3 m.y. hiatus in rhyolite eruptions
between ~14.4 Ma and 12.1 Ma
2) The strong recommencement of rhyolite
eruptive activity at ~12.1 Ma
16
18. A New Model for Miocene Rhyolite Volcanism of eastern Oregon
Cascadia slab rollback is unlikely the primary
driving force behind the HLP volcanic trend.
Recent seismic studies reveal a highly fragmented slab
beneath North America (e.g., Long, 2016), and describe
fragmentation of the slab and resulting cold anomalies
(Zhou et al., 2018) or a westward-propagating tear in
the slab as the driving force for mantle convection
(Hawley and Allen, 2019).
Most importantly, slab rollback is a phenomena
that is assumed to result in continuous mantle
flux to the crust, and the newly revealed episodic
natural of rhyolite volcanism indicates that this is
not the case.
Hawley and Allen (2019)
Slab fragmentation reduces the plausibility of models
where slab subduction or rollback is the sole or primary
driving mechanism for westward-trending crustal melting
(Long et al., 2009; Ford et al., 2013; Wells and McCaffrey,
2013).
17
19. A New Model for Miocene Rhyolite Volcanism of eastern Oregon
The 14.4–12.1 Ma rhyolite eruptive hiatus
and lack of ~13–11 Ma mafic eruptions may
be correlated to decreased plume flux post-
15 Ma
Migration of the North American craton over the plume
tail at ~15 Ma resulted in the once rapid radial spreading
of plume material to transition into the narrow age-
progressive rhyolite volcanism of the YSRP track to the
east and relatively slow westward spreading initiating in
areas west of the craton boundary (e.g., Camp, 2019;
Camp and Wells, 2021).
Jordan et al. (2004)
Decreased plume flux would decrease basaltic volcanism
and associated rhyolite volcanism, as observed in the
data.
18
20. A New Model for Miocene Rhyolite Volcanism of eastern Oregon
Lack of ~13–11 Ma basalts could also be
attributed to hinderance by regional crust.
Older, widespread, erupted and non-erupted co-CRBG
rhyolites distributed throughout slightly thicker
regional crust of eastern Oregon may have prohibited
basaltic magmas from ascending through the crust to
the surface (Ford and Grunder, 2011; Streck et al.,
2015; Townsend, 2019)
Eastern and central Oregon have been subject to
erosion via Basin and Range extensional faulting over
the past ~10 Ma.
There is a notable lack of precise age and geochemical
data for some exposed <15 Ma regional basalts, some
of which are unnamed, and some are postulated to be
associated with the ~7 Ma Drinkwater Basalt (Greene
et al., 1972).
Lack of ~13–11 Ma basalts does not
necessarily negate their existence.
19
21. A New Model for Miocene Rhyolite Volcanism of eastern Oregon
Our compilation of ages from previous studies found
the third and most recent pulse of rhyolite eruptive
activity to be ~9.0–5.2 Ma, which confirms findings
from previous researchers.
These studies describe the relatively larger distribution area and
lesser frequency of rhyolite eruptions <10 Ma to be a result of the
greater areal distribution of mafic input as it spread westward and
eventually buttressed against eastern side of the thick lithosphere
beneath the Cascade Arc (e.g., Ford et al., 2013)
Enough heated mantle was present to generate the 9.0–5.2 Ma
rhyolites and coeval basalts of the HLP but waned after the material
likely began to cool with increased spreading.
Camp (2019)
Imaging of the low-density anomaly at 75 km depth interpreted as
westward spreading plume that can be seen ponding beneath the
western HLP, just east of the Oregon Cascades.
20
22. A New Model for Miocene Rhyolite Volcanism of eastern Oregon
Pre-existing models of channelized
westward plume spreading fit, but not
entirely with respect to timing.
Camp (2019); Camp and Wells (2021)
Camp and Wells (2021) model where westward
migration of plume material did not occur until the
tail was well established beneath the craton (~12
Ma) would explain a hiatus in rhyolite volcanism in
eastern Oregon.
However, if westward spreading began at ~12 Ma
when the plume tail was as far east as southcentral
Idaho, it would take a substantial amount of time to
migrate to the area where 12.1–9.9 Ma rhyolites
erupted in eastern Oregon.
In addition, these models do not reconcile the significantly
wide distribution of 17.5-14.4 Ma rhyolites, and they do
not address the strong recommencement and
concentrated area of ~12.1-9.6 Ma rhyolite eruptions in
the study area.
21
23. A New Model for Miocene Rhyolite Volcanism of eastern Oregon
At this point in the study, regional fault
systems including the Brothers Fault Zone
(BFZ), Northwest Basin and Range
(NWBR), and a relatively unstudied area
of NNW-trending faults north of Steens
Mountain (SM) appear to be a relevant
piece of the volcanic story and require
further investigation.
Trench et al. (2012)
NWBR extension and rotation of the
Pacific Northwest significantly effect
the region by providing crustal
weaknesses for magmas to
propagate to the surface and can
result in erosion and burial of
volcanic deposits.
Though slab dynamics alone are unlikely to be the driving force
behind HLP rhyolite volcanism, the combination of effects of
rollback, subduction counterflow, NWBR extension, and rotation of
the PNW should be included in a model for the HLP province.
22
24. Conclusions
Decreased mantle flux is likely the
primary mechanism behind the lack of
basaltic volcanism immediately prior to
the 12.1–10.1 Ma rhyolite episode, with
lesser but still notable effects from
hinderance by regional crust, erosion,
and lack of data on regional basalts.
Decreased mantle flux
would result in the lack of
rhyolite eruptions from
14.4 Ma to 12.1 Ma.
Miocene rhyolite volcanism of
the HLP and CRBG provinces in
eastern Oregon occurred in a
step function periodicity, with
three prominent episodes and
two distinct eruptive hiatuses.
23
25. Conclusions
Interpretation of our results is still
ongoing, but we propose a model where
Yellowstone plume spreading was
widespread and likely channelized as early
as ~17.5 Ma, resulting in widespread
~17.5-14.4 Ma rhyolites.
NWBR faulting, PNW rotation, and the
Brothers Fault Zone display how the crust
needed to accommodate significant
extension ~17-10 Ma, which would have
eventually thinned the regional lithosphere
and created crustal weaknesses for basalts to
begin infiltrating the crust again.
24
Either deep plume material itself
or upper mantle heated by the
plume resided in eastern Oregon
as North American migrated over
the tail, but mantle flux
decreased enough to cease
rhyolite eruptions ~14.4-12.1 Ma.
26. Conclusions
The Yellowstone plume is the
likely primary driving
mechanism behind co-CRBG
volcanism. The 12.1-9.6 Ma
episode is a combined effect of
the Yellowstone plume, heated
upper mantle, and extension
of the lithosphere. The 7.3-5.2
Ma episode is primarily a
result of heated upper mantle
and tectonic processes, with
less effect from the
Yellowstone plume.
This model involves interpreting each rhyolite
eruptive episode as separate and distinct,
where pulses are explained primarily by
punctuated mafic inputs into the crust, rather
than models with continuous spreading of
heated mantle, where distinct periods of
eruptive activity are difficult to reconcile.
25