Lara Heister - Academia.edu (original) (raw)

Papers by Lara Heister

Proceedings of the 7th Unconventional Resources Technology Conference, 2019

European Addiction Research

Access to full text and tables of contents, including tentative ones for forthcoming issues: www.... more Access to full text and tables of contents, including tentative ones for forthcoming issues: www.karger.com/ear_issues 80 Longitudinal Mapping of Gyral and Sulcal Patterns of Cortical Thickness and Brain Volume Regain during Early Alcohol

SE ALASKA EXHUMATION OF THE COAST MOUNTAINS BATHOLITH DURING THE GREENHOUSE TO ICEHOUSE TRANSITIO... more SE ALASKA EXHUMATION OF THE COAST MOUNTAINS BATHOLITH DURING THE GREENHOUSE TO ICEHOUSE TRANSITION IN SOUTHEAST ALASKA: A MULTIDISCIPLINARY STUDY OF THE PALEOGENE KOOTZNAHOO FM. Faculty: Cameron Davidson (Carleton College), Karl Wirth (Macalester College), Tim White (Penn State University) Students: Lenny Ancuta, Jordan Epstein, Nathan Evenson, Samantha Falcon, Alexander Gonzalez, Tiffany Henderson, Conor McNally, Julia Nave, Maria Princen

Journal of Geoscience Education, 2007

Ocean drilling and land-based studies in Southeast and West Greenland have identified a hiatus in... more Ocean drilling and land-based studies in Southeast and West Greenland have identified a hiatus in volcanic activity lasting ~2 Ma, marking a "quiet" interval between arrival of the ancestral Iceland plume beneath Pangaea (Phase I: ~62-58 Ma) and seafloor spreading in the North Atlantic (Phase II: ~56-54 Ma). Larsen et al. (1999, Geol.Soc., Lond. 156) have argued that coal-bearing sediments between the lower and middle formations on the Faeroe Islands also mark a pause in volcanic activity between Phase I and Phase II. They correlate this stratigraphic interval across the Atlantic basin to the East Greenland margin. We have examined in detail the boundary between lavas of the Nansen Formation and Milne Land Formation on the East Greenland margin where the specific correlation was made. The horizon between these formations, along the northeastern shore of Nansen Fjord (68° N, 30° W), is a 10 m thick, well-exposed volcanogenic deposit. Thirteen oriented samples were collected...

The vanadium to scandium ratio (V/Sc) for basalts from mid-ocean ridge (MOR) and arc environments... more The vanadium to scandium ratio (V/Sc) for basalts from mid-ocean ridge (MOR) and arc environments has been proposed as a proxy for fO2 conditions during partial melting (e.g. [1] and [2]). Contrary to barometric measurements of the fO2 of primitive lavas, the V/Sc ratio of the upper mantle at mid-ocean ridges and arcs is similar, leading previous authors to propose that the upper mantle has uniform redox potential and is well-buffered. We have attempted to broaden the applicability of the V/Sc parameter to plume-influenced localities (both oceanic and continental), where mantle heterogeneities associated with recycled sediments, mafic crust, and metasomatized mantle, whether of shallow or deep origin, exist. We find that primitive basalts from the North Atlantic Igneous Province (NAIP), Hawaii (both the Loa and Kea trends), Deccan, Columbia River, and Siberian Traps show a range of V/Sc ratios that are generally higher (average ~9) than those for MOR (average ~ 6.7) or arc (average ...

Weathering of basalts, tephras and related sediments produces clay and iron oxide/hydroxide miner... more Weathering of basalts, tephras and related sediments produces clay and iron oxide/hydroxide minerals in reddened layers referred to as interbasaltic paleosols, boles or laterites. We suggest that these "redbeds" present throughout the flood basalt stratigraphy of the North Atlantic Igneous Province preserve relatively continuous isotopic records of terrestrial climate change in the Cenozoic. The use of tephras in paleoclimate characterization is particularly encouraged by strong chemical weathering patterns showing a decrease in SiO2 and increase in Al2O3 + Fe2O3 of up to 40-50 wt% relative to whole rock basalt compositions (SiO2 = 45-50 wt%; Al2O3 + Fe2O3 = 15-25 wt%). Furthermore, up to 80% of the weathered tephras are composed of secondary minerals, mostly smectite, hematite, and iron oxy-hydroxides with minor calcite and zeolites in pore spaces and fractures. Our objective is to measure values of deltaD and delta18O of clay minerals and crystalline mixtures of hematite...

Synchronicity of the Paleocene Eocene Thermal Maximum (PETM) at 55.5 Ma and voluminous eruption o... more Synchronicity of the Paleocene Eocene Thermal Maximum (PETM) at 55.5 Ma and voluminous eruption of the of the central east Greenland (CEG) flood basalts has lead authors to find a causal relationship between these two events. However, age constraints within the thick CEG volcanic succession are spare and often are associated with large uncertainties or based on samples with poor stratigraphic control. Based on new Ar-Ar ages combined with chemostratigraphic relationships within the CEG succession, we constrain the timing of the PETM to a restricted portion of the CEG volcanic stratigraphy with the Geike Plateau Formation. As such the PETM occurs at the height of effusive volcanism and limited pyroclastic activity. The outpouring of large volumes of basaltic magma by fissure-fed eruptions could have contributed large volumes of SO2 to the atmosphere, likely contributing to cooling, rather than global warming as recorded by the PETM. Likewise, there is no evidence for CO2-rich volcani...

A 2-megawatt TRIGA reactor, now owned and operated by UC Davis as a research facility, was especi... more A 2-megawatt TRIGA reactor, now owned and operated by UC Davis as a research facility, was especially designed and built by the USAF with a large L/D for neutron-beam radiography of aircraft parts. More recent efforts in computed tomography (CT) have established capabilities of 3-D imaging of a broad range of geological materials, including textured igneous rocks up to 10's cm in size. Neutron-beam imaging is complementary to X-ray CT, especially because of the high neutron cross-sections for many light elements that are not easily detected by X-rays. Our goal is to optimize neutron-beam CT techniques for quantitative studies of igneous textures and mineralogy. To this end, we have made improvements in both image acquisition and data processing. Specifically, we have measured the attenuation coefficient for diabase for beam-hardening corrections. We have characterized the dark charge contribution and developed new strategies for flat field corrections. We have increased our samp...

The transition from continental to flood basalt volcanism in central east Greenland is uniquely p... more The transition from continental to flood basalt volcanism in central east Greenland is uniquely preserved at Nansen fjord. This critical interval is composed of evolved tholeiites of the Lower Volcanics (LV) overlain by 5-7 meters of basaltic pyroclastic material, followed by picrites of the Milne Land Formation (MLF). Unaltered clinopyroxene (cpx) from the pyroclastic deposit offer a means to geochemically

... This central volcano activity and the volumetrically significant pyroclastic and effusive con... more ... This central volcano activity and the volumetrically significant pyroclastic and effusive continentalflood volcanism in the Greenland–Faeroes region could ABSTRACT Acknowledgements 1 10 100 1000 La Ce Pr Nd PmSm Eu Gd Tb Dy Ho Er Tm Yb Ro ck /C ho nd rite s Lu ...

Lithos, 2008

Sixteen 40Ar–39Ar ages are presented for alkaline intrusions to appraise prolonged post-breakup m... more Sixteen 40Ar–39Ar ages are presented for alkaline intrusions to appraise prolonged post-breakup magmatism of the central East Greenland rifted margin, the chronology of rift-to-drift transition, and the asymmetry of magmatic activity in the Northeast Atlantic Igneous Province. The alkaline intrusions mainly crop out in tectonic and magmatic lineaments orthogonal to the rifted margin and occur up to 100 km inland. The

Journal of the Geological Society, 2001

Stratigraphic, geochemical and mineralogical characterization of pyroclastic deposits on the Gron... more Stratigraphic, geochemical and mineralogical characterization of pyroclastic deposits on the Gronau West Nunatak of East Greenland indicates that both alkaline and basaltic tephras occurred during the eruption of flood basalts associated with the opening of the North Atlantic ocean in the early Tertiary. Within the exposed section of Gronau West Nunatak, c. 1 km thick representing c. 1.6 Ma, 17 of the horizons are phreatomagmatic basaltic tephras. Near the top of the section, an alkaline tuff was dated at 53.8 0.3 Ma by 40 Ar/ 39 Ar method. This tuff contains a distinctive mineralogy (sanidine, Mgkatophorite, aegirine) and geochemistry (melt inclusion compositions, and trace and rare earth element abundances) that indicate it was erupted from the Gardiner melanephelinite-carbonatite volcanic complex located 175 km to the SE, which was active from c. 55 to 52 Ma. The alkaline tuff can be correlated to age-equivalent, compositionally similar alkaline pyroclastic horizons reported in North Atlantic sediment cores and in outcrops in Northern Europe, making it an important regional time-stratigraphic marker. This study indicates that North Atlantic explosive volcanic events were prevalent, regionally widespread, and originated in East Greenland during continental rifting, suggesting the need for reappraisal of the impact of North Atlantic volcanism on climate change during the early Tertiary.

Proceedings of the 7th Unconventional Resources Technology Conference, 2019

European Addiction Research

Access to full text and tables of contents, including tentative ones for forthcoming issues: www.... more Access to full text and tables of contents, including tentative ones for forthcoming issues: www.karger.com/ear_issues 80 Longitudinal Mapping of Gyral and Sulcal Patterns of Cortical Thickness and Brain Volume Regain during Early Alcohol

SE ALASKA EXHUMATION OF THE COAST MOUNTAINS BATHOLITH DURING THE GREENHOUSE TO ICEHOUSE TRANSITIO... more SE ALASKA EXHUMATION OF THE COAST MOUNTAINS BATHOLITH DURING THE GREENHOUSE TO ICEHOUSE TRANSITION IN SOUTHEAST ALASKA: A MULTIDISCIPLINARY STUDY OF THE PALEOGENE KOOTZNAHOO FM. Faculty: Cameron Davidson (Carleton College), Karl Wirth (Macalester College), Tim White (Penn State University) Students: Lenny Ancuta, Jordan Epstein, Nathan Evenson, Samantha Falcon, Alexander Gonzalez, Tiffany Henderson, Conor McNally, Julia Nave, Maria Princen

Journal of Geoscience Education, 2007

Ocean drilling and land-based studies in Southeast and West Greenland have identified a hiatus in... more Ocean drilling and land-based studies in Southeast and West Greenland have identified a hiatus in volcanic activity lasting ~2 Ma, marking a "quiet" interval between arrival of the ancestral Iceland plume beneath Pangaea (Phase I: ~62-58 Ma) and seafloor spreading in the North Atlantic (Phase II: ~56-54 Ma). Larsen et al. (1999, Geol.Soc., Lond. 156) have argued that coal-bearing sediments between the lower and middle formations on the Faeroe Islands also mark a pause in volcanic activity between Phase I and Phase II. They correlate this stratigraphic interval across the Atlantic basin to the East Greenland margin. We have examined in detail the boundary between lavas of the Nansen Formation and Milne Land Formation on the East Greenland margin where the specific correlation was made. The horizon between these formations, along the northeastern shore of Nansen Fjord (68° N, 30° W), is a 10 m thick, well-exposed volcanogenic deposit. Thirteen oriented samples were collected...

The vanadium to scandium ratio (V/Sc) for basalts from mid-ocean ridge (MOR) and arc environments... more The vanadium to scandium ratio (V/Sc) for basalts from mid-ocean ridge (MOR) and arc environments has been proposed as a proxy for fO2 conditions during partial melting (e.g. [1] and [2]). Contrary to barometric measurements of the fO2 of primitive lavas, the V/Sc ratio of the upper mantle at mid-ocean ridges and arcs is similar, leading previous authors to propose that the upper mantle has uniform redox potential and is well-buffered. We have attempted to broaden the applicability of the V/Sc parameter to plume-influenced localities (both oceanic and continental), where mantle heterogeneities associated with recycled sediments, mafic crust, and metasomatized mantle, whether of shallow or deep origin, exist. We find that primitive basalts from the North Atlantic Igneous Province (NAIP), Hawaii (both the Loa and Kea trends), Deccan, Columbia River, and Siberian Traps show a range of V/Sc ratios that are generally higher (average ~9) than those for MOR (average ~ 6.7) or arc (average ...

Weathering of basalts, tephras and related sediments produces clay and iron oxide/hydroxide miner... more Weathering of basalts, tephras and related sediments produces clay and iron oxide/hydroxide minerals in reddened layers referred to as interbasaltic paleosols, boles or laterites. We suggest that these "redbeds" present throughout the flood basalt stratigraphy of the North Atlantic Igneous Province preserve relatively continuous isotopic records of terrestrial climate change in the Cenozoic. The use of tephras in paleoclimate characterization is particularly encouraged by strong chemical weathering patterns showing a decrease in SiO2 and increase in Al2O3 + Fe2O3 of up to 40-50 wt% relative to whole rock basalt compositions (SiO2 = 45-50 wt%; Al2O3 + Fe2O3 = 15-25 wt%). Furthermore, up to 80% of the weathered tephras are composed of secondary minerals, mostly smectite, hematite, and iron oxy-hydroxides with minor calcite and zeolites in pore spaces and fractures. Our objective is to measure values of deltaD and delta18O of clay minerals and crystalline mixtures of hematite...

Synchronicity of the Paleocene Eocene Thermal Maximum (PETM) at 55.5 Ma and voluminous eruption o... more Synchronicity of the Paleocene Eocene Thermal Maximum (PETM) at 55.5 Ma and voluminous eruption of the of the central east Greenland (CEG) flood basalts has lead authors to find a causal relationship between these two events. However, age constraints within the thick CEG volcanic succession are spare and often are associated with large uncertainties or based on samples with poor stratigraphic control. Based on new Ar-Ar ages combined with chemostratigraphic relationships within the CEG succession, we constrain the timing of the PETM to a restricted portion of the CEG volcanic stratigraphy with the Geike Plateau Formation. As such the PETM occurs at the height of effusive volcanism and limited pyroclastic activity. The outpouring of large volumes of basaltic magma by fissure-fed eruptions could have contributed large volumes of SO2 to the atmosphere, likely contributing to cooling, rather than global warming as recorded by the PETM. Likewise, there is no evidence for CO2-rich volcani...

A 2-megawatt TRIGA reactor, now owned and operated by UC Davis as a research facility, was especi... more A 2-megawatt TRIGA reactor, now owned and operated by UC Davis as a research facility, was especially designed and built by the USAF with a large L/D for neutron-beam radiography of aircraft parts. More recent efforts in computed tomography (CT) have established capabilities of 3-D imaging of a broad range of geological materials, including textured igneous rocks up to 10's cm in size. Neutron-beam imaging is complementary to X-ray CT, especially because of the high neutron cross-sections for many light elements that are not easily detected by X-rays. Our goal is to optimize neutron-beam CT techniques for quantitative studies of igneous textures and mineralogy. To this end, we have made improvements in both image acquisition and data processing. Specifically, we have measured the attenuation coefficient for diabase for beam-hardening corrections. We have characterized the dark charge contribution and developed new strategies for flat field corrections. We have increased our samp...

The transition from continental to flood basalt volcanism in central east Greenland is uniquely p... more The transition from continental to flood basalt volcanism in central east Greenland is uniquely preserved at Nansen fjord. This critical interval is composed of evolved tholeiites of the Lower Volcanics (LV) overlain by 5-7 meters of basaltic pyroclastic material, followed by picrites of the Milne Land Formation (MLF). Unaltered clinopyroxene (cpx) from the pyroclastic deposit offer a means to geochemically

... This central volcano activity and the volumetrically significant pyroclastic and effusive con... more ... This central volcano activity and the volumetrically significant pyroclastic and effusive continentalflood volcanism in the Greenland–Faeroes region could ABSTRACT Acknowledgements 1 10 100 1000 La Ce Pr Nd PmSm Eu Gd Tb Dy Ho Er Tm Yb Ro ck /C ho nd rite s Lu ...

Lithos, 2008

Sixteen 40Ar–39Ar ages are presented for alkaline intrusions to appraise prolonged post-breakup m... more Sixteen 40Ar–39Ar ages are presented for alkaline intrusions to appraise prolonged post-breakup magmatism of the central East Greenland rifted margin, the chronology of rift-to-drift transition, and the asymmetry of magmatic activity in the Northeast Atlantic Igneous Province. The alkaline intrusions mainly crop out in tectonic and magmatic lineaments orthogonal to the rifted margin and occur up to 100 km inland. The

Journal of the Geological Society, 2001

Stratigraphic, geochemical and mineralogical characterization of pyroclastic deposits on the Gron... more Stratigraphic, geochemical and mineralogical characterization of pyroclastic deposits on the Gronau West Nunatak of East Greenland indicates that both alkaline and basaltic tephras occurred during the eruption of flood basalts associated with the opening of the North Atlantic ocean in the early Tertiary. Within the exposed section of Gronau West Nunatak, c. 1 km thick representing c. 1.6 Ma, 17 of the horizons are phreatomagmatic basaltic tephras. Near the top of the section, an alkaline tuff was dated at 53.8 0.3 Ma by 40 Ar/ 39 Ar method. This tuff contains a distinctive mineralogy (sanidine, Mgkatophorite, aegirine) and geochemistry (melt inclusion compositions, and trace and rare earth element abundances) that indicate it was erupted from the Gardiner melanephelinite-carbonatite volcanic complex located 175 km to the SE, which was active from c. 55 to 52 Ma. The alkaline tuff can be correlated to age-equivalent, compositionally similar alkaline pyroclastic horizons reported in North Atlantic sediment cores and in outcrops in Northern Europe, making it an important regional time-stratigraphic marker. This study indicates that North Atlantic explosive volcanic events were prevalent, regionally widespread, and originated in East Greenland during continental rifting, suggesting the need for reappraisal of the impact of North Atlantic volcanism on climate change during the early Tertiary.