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Articles 31 - 60 of 219
Full-Text Articles in Geology
A Global Set Of Subduction Zone Earthquake Scenarios And Recurrence Intervals Inferred From Geodetically Constrained Block Models Of Interseismic Coupling Distributions, Shannon E. Graham, John P. Loveless, Brendan J. Meade
A Global Set Of Subduction Zone Earthquake Scenarios And Recurrence Intervals Inferred From Geodetically Constrained Block Models Of Interseismic Coupling Distributions, Shannon E. Graham, John P. Loveless, Brendan J. Meade
Geosciences: Faculty Publications
The past 100 years have seen the occurrence of five (Formula presented.) earthquakes and 94 (Formula presented.) earthquakes. Here we assess the potential for future great earthquakes using inferences of interseismic subduction zone coupling from a global block model incorporating both tectonic plate motions and earthquake cycle effects. Interseismic earthquake cycle effects are represented using a first-order quasistatic elastic approximation and include (Formula presented.) of interacting fault system area across the globe. We use estimated spatial variations in decadal-duration coupling at 15 subduction zones and the Himalayan range front to estimate the locations and magnitudes of potential seismic events using …
Evaluating Models For Lithospheric Loss And Intraplate Volcanism Beneath The Central Appalachian Mountains, Maureen D. Long, Lara S. Wagner, Scott D. King, Rob L. Evans, Sarah E. Mazza, Joseph S. Byrnes, Elizabeth A. Johnson, Eric Kirby, Maximiliano J. Bezada, Esteban Gazel, Scott R. Miller, John C. Aragon, Shangxin Liu
Evaluating Models For Lithospheric Loss And Intraplate Volcanism Beneath The Central Appalachian Mountains, Maureen D. Long, Lara S. Wagner, Scott D. King, Rob L. Evans, Sarah E. Mazza, Joseph S. Byrnes, Elizabeth A. Johnson, Eric Kirby, Maximiliano J. Bezada, Esteban Gazel, Scott R. Miller, John C. Aragon, Shangxin Liu
Geosciences: Faculty Publications
The eastern margin of North America has been shaped by a series of tectonic events including the Paleozoic Appalachian Orogeny and the breakup of Pangea during the Mesozoic. For the past ∼200 Ma, eastern North America has been a passive continental margin; however, there is evidence in the Central Appalachian Mountains for post-rifting modification of lithospheric structure. This evidence includes two co-located pulses of magmatism that post-date the rifting event (at 152 and 47 Ma) along with low seismic velocities, high seismic attenuation, and high electrical conductivity in the upper mantle. Here, we synthesize and evaluate constraints on the lithospheric …
Tectonic Transport Directions, Shear Senses And Deformation Temperatures Indicated By Quartz C‐Axis Fabrics And Microstructures In A Nw‐Se Transect Across The Moine And Sgurr Beag Thrust Sheets, Caledonian Orogen Of Northern Scotland, Richard D. Law, J. Ryan Thigpen, Sarah E. Mazza, Calvin A. Mako, Maarten Krabbendam, Brandon M. Spencer, Kyle T. Ashley, Robin A. Strachan, Ella F. Davis
Tectonic Transport Directions, Shear Senses And Deformation Temperatures Indicated By Quartz C‐Axis Fabrics And Microstructures In A Nw‐Se Transect Across The Moine And Sgurr Beag Thrust Sheets, Caledonian Orogen Of Northern Scotland, Richard D. Law, J. Ryan Thigpen, Sarah E. Mazza, Calvin A. Mako, Maarten Krabbendam, Brandon M. Spencer, Kyle T. Ashley, Robin A. Strachan, Ella F. Davis
Geosciences: Faculty Publications
Moine metasedimentary rocks of northern Scotland are characterized by arcuate map patterns of mineral lineations that swing progressively clockwise from orogen‐perpendicular E‐trend-ing lineations in greenschist facies mylonites above the Moine thrust on the foreland edge of the Caledonian Orogen, to S‐trending lineations at higher structural levels and metamorphic grades in the hinterland. Quartz c‐axis fabrics measured on a west to east coast transect demonstrate that the lineations developed parallel to the maximum principal extension direction and therefore track the local tectonic transport direction. Microstructures and c‐axis fabrics document a progressive change from top to the N shearing in the hinterland …
Cenomanian–Turonian Oceanic Anoxic Event (Oae2) Imprint On The Northwestern Part Of The Adriatic Carbonate Platform And A Coeval Intra-Platform Basin (Istria And Premuda Island, Croatia), Vlatko Brčić, Bosiljka Glumac, Mihovil Brlek, Ladislav Fuček, Martina Šparica Miko
Cenomanian–Turonian Oceanic Anoxic Event (Oae2) Imprint On The Northwestern Part Of The Adriatic Carbonate Platform And A Coeval Intra-Platform Basin (Istria And Premuda Island, Croatia), Vlatko Brčić, Bosiljka Glumac, Mihovil Brlek, Ladislav Fuček, Martina Šparica Miko
Geosciences: Faculty Publications
The Cenomanian–Turonian boundary (CTB) on the intra-Tethyan Adriatic Carbonate Platform (AdCP) is generally characterised by a transition between microbially laminated and/or bioclastic limestones to calcisphere-rich massive limestone with bioturbated intervals, organic-rich interbeds, firmgrounds, as well as neptunian dikes, carbonate turbidites, tempestites and slumped structures. Compilation of the results from two study sites in the northwestern part of the AdCP and from previous research (on Istria Peninsula and islands in the Adriatic Sea in Croatia) provides a more complete overview of geological events and paleoenvironmental conditions that transformed the formerly contiguous shallow-marine environments during this time period. For the first time, …
An Early Triassic Small Shelly Fossil-Style Assemblage From The Virgin Limestone Member, Moenkopi Formation, Western United States, Vivienne Maxwell, Ben Thuy, Sara B. Pruss
An Early Triassic Small Shelly Fossil-Style Assemblage From The Virgin Limestone Member, Moenkopi Formation, Western United States, Vivienne Maxwell, Ben Thuy, Sara B. Pruss
Geosciences: Faculty Publications
Small shelly fossils (SSFs) are minute fossils moulded or replaced by apatite, and less commonly, other minerals like glauconite and iron oxides. This taphonomic mode is best known from Cambrian deposits, though some occurrences occur across geological time. Instances of small shelly-style preservation were found in insoluble residues from the Lower Triassic Virgin Limestone Member exposed in southern Nevada, the western United States, a second such occurrence known from this unit. Fossil steinkerns of tiny brachiopods, echinoid spines and ophiuroids are fluorapatite, with scarce phosphatic internal moulds of bivalves and two replaced ostracods. In contrast, the crinoid ossicles, almost all …
Slip And Strain Accumulation Along The Sadie Creek Fault, Olympic Peninsula, Washington, W. Cody Duckworth, Colin B. Amos, Elizabeth R. Schermer, John P. Loveless, Tammy M. Rittenour
Slip And Strain Accumulation Along The Sadie Creek Fault, Olympic Peninsula, Washington, W. Cody Duckworth, Colin B. Amos, Elizabeth R. Schermer, John P. Loveless, Tammy M. Rittenour
Geosciences: Faculty Publications
Upper-plate faulting in the Olympic Peninsula of Washington State results from relative motion of crustal blocks within the Cascadia forearc and earthquake cycle processes along the Cascadia subduction zone. We reconstruct fault slip rates since ∼14 ka on the Sadie Creek fault (SCF), north of the Olympic Mountains, using airborne lidar and field mapping of surficial deposits and landforms and optically stimulated luminescence and radiocarbon dating. The SCF is a ≥14 km-long northwest-striking, subvertical, dextral strike-slip fault with a subordinate dip-slip component. Laterally, offset debris flow channels cut into Late-Pleistocene and younger surfaces show dextral slip of 4.0–24.5 m and …
Revised Fractional Abundances And Warm-Season Temperatures Substantially Improve Brgdgt Calibrations In Lake Sediments, Jonathan H. Raberg, David J. Harning, Sarah E. Crump, Gregory De Wet, Aria Blumm, Sebastian Kopf, Áslaug Geirsdóttir, Gifford H. Miller, Julio Sepúlveda
Revised Fractional Abundances And Warm-Season Temperatures Substantially Improve Brgdgt Calibrations In Lake Sediments, Jonathan H. Raberg, David J. Harning, Sarah E. Crump, Gregory De Wet, Aria Blumm, Sebastian Kopf, Áslaug Geirsdóttir, Gifford H. Miller, Julio Sepúlveda
Geosciences: Faculty Publications
Distributions of branched glycerol dialkyl glycerol tetraethers (brGDGTs) are frequently employed for reconstructing terrestrial paleotemperatures from lake sediment archives. Although brGDGTs are globally ubiquitous, the microbial producers of these membrane lipids remain unknown, precluding a full understanding of the ways in which environmental parameters control their production and distribution. Here, we advance this understanding in three ways. First, we present 43 new high-latitude lake sites characterized by low mean annual air temperatures (MATs) and high seasonality, filling an important gap in the global dataset. Second, we introduce a new approach for analyzing brGDGT data in which compound fractional abundances (FAs) …
Ancient Plant Dna Reveals High Arctic Greening During The Last Interglacial, Sarah E. Crump, Bianca Fréchette, Matthew Power, Sam Cutler, Gregory De Wet, Martha K. Raynolds, Jonathan H. Raberg, Jason P. Briner, Elizabeth K. Thomas, Julio Sepúlveda, Beth Shapiro, Michael Bunce, Gifford H. Miller
Ancient Plant Dna Reveals High Arctic Greening During The Last Interglacial, Sarah E. Crump, Bianca Fréchette, Matthew Power, Sam Cutler, Gregory De Wet, Martha K. Raynolds, Jonathan H. Raberg, Jason P. Briner, Elizabeth K. Thomas, Julio Sepúlveda, Beth Shapiro, Michael Bunce, Gifford H. Miller
Geosciences: Faculty Publications
Summer warming is driving a greening trend across the Arctic, with the potential for large-scale amplification of climate change due to vegetation-related feedbacks [Pearson et al., Nat. Clim. Chang. (3), 673–677 (2013)]. Because observational records are sparse and temporally limited, past episodes of Arctic warming can help elucidate the magnitude of vegetation response to temperature change. The Last Interglacial ([LIG], 129,000 to 116,000 y ago) was the most recent episode of Arctic warming on par with predicted 21st century temperature change [Otto-Bliesner et al., Philos. Trans. A Math. Phys. Eng. Sci. (371), 20130097 (2013) and Post et al., Sci. Adv. …
A Reference Section For The Otavi Group (Damara Supergroup) In Eastern Kaoko Zone Near Ongongo, Namibia, P.F. Hoffman, Sara B. Pruss, C.L. Blättler, E.J. Bellefroid, B.W. Johnson
A Reference Section For The Otavi Group (Damara Supergroup) In Eastern Kaoko Zone Near Ongongo, Namibia, P.F. Hoffman, Sara B. Pruss, C.L. Blättler, E.J. Bellefroid, B.W. Johnson
Geosciences: Faculty Publications
A reference section for the Otavi Group (Damara Supergroup) in the East Kaoko Zone near Ongongo is proposed and described. The section is easily accessible, well exposed, suitable for field excursions, and well documented in terms of carbonate lithofacies, depositional sequences and stableisotope chemostratigraphy. The late Tonian Ombombo Subgroup is 355 m thick above the basal Beesvlakte Formation, which is not included in the section due to poor outcrop and complex structure. The earlymiddle Cryogenian Abenab Subgroup is 636 m thick and the early Ediacaran Tsumeb Subgroup is 1020 m thick. While the section is complete in terms of formations …
Coral Gardens Reef, Belize: A Refugium In The Face Of Caribbean-Wide Acropora Spp. Coral Decline, Lisa Greer, Tara Clark, Tanner Waggoner, James Busch, Thomas P. Guilderson, Karl Wirth, Jian-Xin Zhao, H. Allen Curran
Coral Gardens Reef, Belize: A Refugium In The Face Of Caribbean-Wide Acropora Spp. Coral Decline, Lisa Greer, Tara Clark, Tanner Waggoner, James Busch, Thomas P. Guilderson, Karl Wirth, Jian-Xin Zhao, H. Allen Curran
Geosciences: Faculty Publications
Caribbean Acropora spp. corals have undergone a decline in cover since the second half of the twentieth century. Loss of these architecturally complex and fast-growing corals has resulted in significant, cascading changes to the character, diversity, and available eco spaces of Caribbean reefs. Few thriving Acropora spp. populations exist today in the Caribbean and western North Atlantic seas, and our limited ability to access data from reefs assessed via long-term monitoring efforts means that reef scientists are challenged to determine resilience and longevity of existing Acropora spp. reefs. Here we used multiple dating methods to measure reef longevity and determine …
Controls On The Formation Of Microbially Induced Sedimentary Structures And Biotic Recovery In The Lower Triassic Of Arctic Canada, Paul B. Wignall, David P.G. Bond, Stephen E. Grasby, Sara B. Pruss, Jeffrey Peakall
Controls On The Formation Of Microbially Induced Sedimentary Structures And Biotic Recovery In The Lower Triassic Of Arctic Canada, Paul B. Wignall, David P.G. Bond, Stephen E. Grasby, Sara B. Pruss, Jeffrey Peakall
Geosciences: Faculty Publications
Microbially induced sedimentary structures (MISS) are reportedly widespread in the Early Triassic and their occurrence is attributed to either the extinction of marine grazers (allowing mat preservation) during the Permo-Triassic mass extinction or the suppression of grazing due to harsh, oxygenpoor conditions in its aftermath. Here we report on the abundant occurrence of MISS in the Lower Triassic Blind Fiord Formation of the Sverdrup Basin, Arctic Canada. Sedimentological analysis shows that mid-shelf settings were dominated by deposition from cohesive sand-mud flows that produced heterolithic, rippled sandstone facies that pass down dip into laminated siltstones and ultimately basinal mudrocks. The absence …
Solving The Bermuda Mystery: An Island That Tells A Story Of A New Way To Form Volcanoes, Sarah E. Mazza
Solving The Bermuda Mystery: An Island That Tells A Story Of A New Way To Form Volcanoes, Sarah E. Mazza
Geosciences: Faculty Publications
Bermuda’s explosive past has changed how geologists think about the processes that make volcanoes. The chemical composition of the lavas analyzed in this study indicate that Bermuda ‘tapped’ a geologically young, volatile rich layer in the mantle, unlike anything previously known.
Tracing Dehydration And Melting Of The Subducted Slab With Tungsten Isotopes In Arc Lavas, Sarah E. Mazza, Andreas Stracke, James B. Gill, Jun Ichi Kimura, Thorsten Kleine
Tracing Dehydration And Melting Of The Subducted Slab With Tungsten Isotopes In Arc Lavas, Sarah E. Mazza, Andreas Stracke, James B. Gill, Jun Ichi Kimura, Thorsten Kleine
Geosciences: Faculty Publications
Tungsten is strongly incompatible during magmatic processes and is fluid mobile in subduction zones. Here we show that W isotope fractionation in arc lavas provide a powerful new tool for tracing slab dehydration and melting in subduction zones. Geochemically well characterized, representative arc-lavas from three subduction zones were chosen for this study to evaluate W isotope fractionation under different sub-arc conditions. Arc-lavas from SW Japan are produced by subducting a young, hot slab, and lavas from the volcanic front and rear arc of the Sangihe and Izu arcs are produced during subduction of a cold slab. The heaviest W isotope …
Holocene And Last Interglacial Climate Of The Faroe Islands From Sedimentary Plant Wax Hydrogen And Carbon Isotopes, Lorelei Curtin, William J. D'Andrea, Nicholas Balascio, Genevieve Pugsley, Gregory De Wet, Raymond Bradley
Holocene And Last Interglacial Climate Of The Faroe Islands From Sedimentary Plant Wax Hydrogen And Carbon Isotopes, Lorelei Curtin, William J. D'Andrea, Nicholas Balascio, Genevieve Pugsley, Gregory De Wet, Raymond Bradley
Geosciences: Faculty Publications
The Last Interglacial period (LIG) is Earth's most recent globally warm period and is analogous in some ways to projected future global warming. However, questions remain regarding the state of the climate during the LIG in the North Atlantic, a region that is extremely sensitive to changes in oceanic and atmospheric circulation. Here, we present hydrogen and carbon isotope (δD and δ13C) records from a suite of plant wax biomarkers preserved in Holocene and LIG lacustrine sediments from the North Atlantic Faroe Islands and interpret them as qualitative proxies for temperature and hydroclimate variability. These data are used to directly …
Mercury Chemostratigraphy Across The Cambrian Series 2 – Series 3 Boundary: Evidence For Increased Volcanic Activity Coincident With Extinction?, L. E. Faggetter, P. B. Wignall, S. B. Pruss, D. S. Jones, S. Grasby, M. Widdowson, R. J. Newton
Mercury Chemostratigraphy Across The Cambrian Series 2 – Series 3 Boundary: Evidence For Increased Volcanic Activity Coincident With Extinction?, L. E. Faggetter, P. B. Wignall, S. B. Pruss, D. S. Jones, S. Grasby, M. Widdowson, R. J. Newton
Geosciences: Faculty Publications
Flood basalt volcanism represented by the Kalkarindji Province (Australia) is temporally associated with a trilobite mass extinction at the Cambrian Series 2 – Series 3 boundary, providing one of the oldest potential links between volcanism and biotic crisis in the Phanerozoic. However, the relative timing of flood basalt volcanism (Kalkarindji Province, Australia) and the trilobite extinctions, first recorded in North America, is not known. Mercury (Hg) enrichment in the sedimentary record provides a potential proxy for volcanism which may facilitate improved chronologies of eruption and extinction. Here we report mercury records for three sections from mid-shelf strata of the Great …
Pleistocene Glacial History Of The New Zealand Subantarctic Islands, Eleanor Rainsley, Chris S.M. Turney, Nicholas R. Golledge, Janet M. Wilmshurst, Matt S. Mcglone, Alan G. Hogg, Bo Li, Zoë A. Thomas, Richard Roberts, Richard T. Jones, Jonathan G. Palmer, Verity Flett, Gregory De Wet, David K. Hutchinson, Mathew J. Lipson, Pavla Fenwick, Ben Hines, Umberto Binetti, Christopher J. Fogwill
Pleistocene Glacial History Of The New Zealand Subantarctic Islands, Eleanor Rainsley, Chris S.M. Turney, Nicholas R. Golledge, Janet M. Wilmshurst, Matt S. Mcglone, Alan G. Hogg, Bo Li, Zoë A. Thomas, Richard Roberts, Richard T. Jones, Jonathan G. Palmer, Verity Flett, Gregory De Wet, David K. Hutchinson, Mathew J. Lipson, Pavla Fenwick, Ben Hines, Umberto Binetti, Christopher J. Fogwill
Geosciences: Faculty Publications
The New Zealand subantarctic islands of Auckland and Campbell, situated between the subtropical front and the Antarctic Convergence in the Pacific sector of the Southern Ocean, provide valuable terrestrial records from a globally important climatic region. Whilst the islands show clear evidence of past glaciation, the timing and mechanisms behind Pleistocene environmental and climate changes remain uncertain. Here we present a multidisciplinary study of the islands-including marine and terrestrial geomorphological surveys, extensive analyses of sedimentary sequences, a comprehensive dating programme, and glacier flow line modelling-to investigate multiple phases of glaciation across the islands. We find evidence that the Auckland Islands …
Experimental Preservation Of Muscle Tissue In Quartz Sand And Kaolinite: Supplemental Information, Sharon A. Newman, Mirna Daye, Sirine C. Fakra, Matthew A. Marcus, Mihkel Pajusalu, Sara B. Pruss, Emily F. Smith, Tanja Bosak
Experimental Preservation Of Muscle Tissue In Quartz Sand And Kaolinite: Supplemental Information, Sharon A. Newman, Mirna Daye, Sirine C. Fakra, Matthew A. Marcus, Mihkel Pajusalu, Sara B. Pruss, Emily F. Smith, Tanja Bosak
Geosciences: Faculty Publications
Siliciclastic sediments of the Ediacaran Period contain exceptionally preserved fossils of macroscopic organisms, including three-dimensional casts and molds commonly found in sandstones and siltstones and some two-dimensional compressions reported in shales. The sporadic and variable associations of these exceptionally preserved macroscopic fossils with pyrite, clay minerals, and microbial fossils and textures complicate our understanding of fossilization processes. This hinders inferences about the evolutionary histories, tissue types, original morphologies, and lifestyles of the enigmatic Ediacara biota. Here, we investigate the delayed decay of scallop muscles buried in quartz sand or kaolinite for 45 days. This process occurs in the presence of …
New Source-To-Sink Approach In An Arctic Catchment Based On Hyperspectral Core-Logging (Lake Linné, Svalbard), Antonin Van Exem, Maxime Debret, Yoann Copard, Charles Verpoorter, Gregory De Wet, Nicolas Lecoq, Philippe Sorrel, Alan Werner, Steven Roof, Benoit Laignel, Michael Retelle
New Source-To-Sink Approach In An Arctic Catchment Based On Hyperspectral Core-Logging (Lake Linné, Svalbard), Antonin Van Exem, Maxime Debret, Yoann Copard, Charles Verpoorter, Gregory De Wet, Nicolas Lecoq, Philippe Sorrel, Alan Werner, Steven Roof, Benoit Laignel, Michael Retelle
Geosciences: Faculty Publications
No abstract provided.
Small Shelly Fossil Preservation And The Role Of Early Diagenetic Redox In The Early Triassic, Sara B. Pruss, Nicholas J. Tosca, Courcelle Stark
Small Shelly Fossil Preservation And The Role Of Early Diagenetic Redox In The Early Triassic, Sara B. Pruss, Nicholas J. Tosca, Courcelle Stark
Geosciences: Faculty Publications
Minute fossils from a variety of different metazoan clades, collectively referred to as small shelly fossils, represent a distinctive taphonomic mode that is most commonly reported from the Cambrian Period. Lower Triassic successions of the western United States, deposited in the aftermath of the end-Permian mass extinction, provide an example of small shelly style preservation that significantly post-dates Cambrian occurrences. Glauconitized and phosphatized echinoderms and gastropods are preserved in the insoluble residues of carbonates from the Virgin Limestone Member of the Moenkopi Formation. Echinoderm plates, spines and other skeletal elements are preserved as stereomic molds; gastropods are preserved as steinkerns. …
Thermobarometry Of The Moine And Sgurr Beag Thrust Sheets, Northern Scotland, Sarah E. Mazza, Calvin Mako, Richard D. Law, Mark J. Caddick, Maarten Krabbendam, John Cottle
Thermobarometry Of The Moine And Sgurr Beag Thrust Sheets, Northern Scotland, Sarah E. Mazza, Calvin Mako, Richard D. Law, Mark J. Caddick, Maarten Krabbendam, John Cottle
Geosciences: Faculty Publications
In the Caledonides of northern Scotland temperatures of metamorphism (Tm) and deformation (Td) progressively increase structurally up section in the Moine thrust sheet at the foreland edge of the Scandian (mid Silurian) orogenic wedge. However, the thermal history of the structurally overlying, more hinterland positioned thrust sheets is less well known. This study focuses on determining Td and Tm for both the central/upper part of the Moine thrust sheet and the lower part of the overlying Sgurr Beag thrust sheets in the middle of the Northern Highlands Terrane. Preserved microstructures and quartz c-axis fabric opening angles in the Moine and …
Contribution Of Benthic Processes To The Growth Of Ooids On A Low-Energy Shore In Cat Island, The Bahamas, Giulio Mariotti, Sara B. Pruss, Roger E. Summons, Sharon A. Newman, Tanja Bosak
Contribution Of Benthic Processes To The Growth Of Ooids On A Low-Energy Shore In Cat Island, The Bahamas, Giulio Mariotti, Sara B. Pruss, Roger E. Summons, Sharon A. Newman, Tanja Bosak
Geosciences: Faculty Publications
Ooids are typically found in frequently reworked coastal sediments, and are thought to accrete by inorganic chemical precipitation around moving grains. The high organic content and the presence of biosignatures, however, suggest that ooids interact with benthic microbial communities. Here, we investigate the role of benthic processes on ooid growth on a leeward shore of Cat Island, The Bahamas. Polished ooids are present in the surf zone, whereas dull ooids and grapestones are present in microbially colonized sediments seaward of the surf zone. Wave hydrodynamics and sediment transport modeling suggest that microbially colonized sediments are mobilized at monthly time scales. …
Sequence Stratigraphy, Chemostratigraphy And Facies Analysis Of Cambrian Series 2 - Series 3 Boundary Strata In Northwestern Scotland, Luke E. Faggetter, Paul B. Wignall, Sara B. Pruss, Yadong Sun, Robert J. Raine, Robert J. Newton, Mike Widdowson, Michael M. Joachimski, Paul M. Smith
Sequence Stratigraphy, Chemostratigraphy And Facies Analysis Of Cambrian Series 2 - Series 3 Boundary Strata In Northwestern Scotland, Luke E. Faggetter, Paul B. Wignall, Sara B. Pruss, Yadong Sun, Robert J. Raine, Robert J. Newton, Mike Widdowson, Michael M. Joachimski, Paul M. Smith
Geosciences: Faculty Publications
Globally, the Series 2 - Series 3 boundary of the Cambrian System coincides with a major carbon isotope excursion, sea-level changes and trilobite extinctions. Here we examine the sedimentology, sequence stratigraphy and carbon isotope record of this interval in the Cambrian strata (Durness Group) of NW Scotland. Carbonate carbon isotope data from the lower part of the Durness Group (Ghrudaidh Formation) show that the shallow-marine, Laurentian margin carbonates record two linked sea-level and carbon isotopic events. Whilst the carbon isotope excursions are not as pronounced as those expressed elsewhere, correlation with global records (Sauk I - Sauk II boundary and …
Interseismic Coupling-Based Earthquake And Tsunami Scenarios For The Nankai Trough, Hannah Baranes, Jon D. Woodruff, John P. Loveless, M. Hyodo
Interseismic Coupling-Based Earthquake And Tsunami Scenarios For The Nankai Trough, Hannah Baranes, Jon D. Woodruff, John P. Loveless, M. Hyodo
Geosciences: Faculty Publications
Theoretical modeling and investigations of recent subduction zone earthquakes show that geodetic estimates of interseismic coupling and the spatial distribution of coseismic rupture are correlated. However, the utility of contemporary coupling in guiding construction of rupture scenarios has not been evaluated on the world’s most hazardous faults. Here we demonstrate methods for scaling coupling to slip to create rupture models for southwestern Japan’s Nankai Trough. Results show that coupling-based models produce distributions of ground surface deformation and tsunami inundation that are similar to historical and geologic records of the largest known Nankai earthquake in CE 1707 and to an independent, …
The Island Of Amsterdamøya: A Key Site For Studying Past Climate In The Arctic Archipelago Of Svalbard, Jostein Bakke, Nicholas Balascio, Willem G.M. Van Der Bilt, Raymond Bradley, William J. D' Andrea, Marthe Gjerde, Sædís Ólafsdóttir, Torgeir Røthe, Greg De Wet
The Island Of Amsterdamøya: A Key Site For Studying Past Climate In The Arctic Archipelago Of Svalbard, Jostein Bakke, Nicholas Balascio, Willem G.M. Van Der Bilt, Raymond Bradley, William J. D' Andrea, Marthe Gjerde, Sædís Ólafsdóttir, Torgeir Røthe, Greg De Wet
Geosciences: Faculty Publications
This paper introduces a series of articles assembled in a special issue that explore Holocene climate evolution, as recorded in lakes on the Island of Amsterdamøya on the westernmost fringe of the Arctic Svalbard archipelago. Due to its location near the interface of oceanic and atmospheric systems sourced from Arctic and Atlantic regions, Amsterdamøya is a key site for recording the terrestrial response to marine and atmospheric changes. We employed multi-proxy approaches on lake sediments, integrating physical, biogeochemical, and isotopic analyses to infer past changes in temperature, precipitation, and glacier activity. The results comprise a series of quantitative Holocene-length paleoclimate …
Holocene Glacier Activity Reconstructed From Proglacial Lake Gjøavatnet On Amsterdamøya, Nw Svalbard, Gregory A. De Wet, Nicholas L. Balascio, William J. D'Andrea, Jostein Bakke, Raymond S. Bradley, Bianca Perren
Holocene Glacier Activity Reconstructed From Proglacial Lake Gjøavatnet On Amsterdamøya, Nw Svalbard, Gregory A. De Wet, Nicholas L. Balascio, William J. D'Andrea, Jostein Bakke, Raymond S. Bradley, Bianca Perren
Geosciences: Faculty Publications
Well-dated and highly resolved paleoclimate records from high latitudes allow for a better understanding of past climate change. Lake sediments are excellent archives of environmental change, and can record processes occurring within the catchment, such as the growth or demise of an upstream glacier. Here we present a Holocene-length, multi-proxy lake sediment record from proglacial lake Gjøavatnet on the island of Amsterdamøya, northwest Svalbard. Today, Gjøavatnet receives meltwater from the Annabreen glacier and contains a record of changes in glacier activity linked to regional climate conditions. We measured changes in organic matter content, dry bulk density, bulk carbon isotopes, elemental …
Siphons, Water Clocks, Cooling Coffee, And Leaking Capacitors: Classroom Activities And A Few Equations To Help Students Understand Radioactive Decay And Other Exponential Processes, John B. Brady
Geosciences: Faculty Publications
Although an understanding of radiometric dating is central to the preparation of every geologist, many students struggle with the concepts and mathematics of radioactive decay. Physical demonstrations and hands-on experiments can be used to good effect in addressing this teaching conundrum. Water, heat, and electrons all move or flow in response to generalized forces (gradients in pressure, temperature, and electrical potential) that may change because of the flow. Changes due to these flows are easy to monitor over time during simple experiments in the classroom. Some of these experiments can be modeled as exponential decay, analogous to the mathematics of …
Global Plate Motions And Earthquake Cycle Effects, Shannon E. Graham, John P. Loveless, Brendan J. Meade
Global Plate Motions And Earthquake Cycle Effects, Shannon E. Graham, John P. Loveless, Brendan J. Meade
Geosciences: Faculty Publications
The rotations of tectonic plates provide a partial description of the total observed displacements at the Earth’s surface. The estimated number of kinematically distinct plates has increased from 12 in 1990 to 56 in 2010 as a result of the increase in the number of kinematic observables. At length scales <1,000 km, rotation-only plate models are inaccurate because geodetic signals of long-term plate motions are complicated by earthquake cycle effects. Here we present results from a global block model that unifies large-scale plate motions and local earthquake cycle effects at plate boundaries. Incorporating the rotations of 307 distinct plates, elastic strain accumulation from 16 subduction zones and 1.59×107 km2 of fault system area, this model explains 19,664 interseismic GPS velocities at a resolution of 2.2 mm/year. Geodetically constrained fault slip deficit rates yield a cumulative global moment accumulation rate of 1.09 × 1022 N⋅m/year, 12% larger than the average annual coseismic moment release rate from 1900 to 2013. The potential contribution to the total moment rate budget can be estimated from the frequency distribution of the modeled fault slip-deficit rates, which follow an exponential distribution. Integrating this frequency distribution over all possible slip rates indicates that the geologic structures included in this reference global block model account for 98% of the global moment budget. Comparing our results with population distribution, we find that ∼50% of the world’s population lives within 200 km of an active fault with a slip rate >2 mm/year.
Pyritized Cryogenian Cyanobacteria Fossils From Arctic Alaska, Kelsey R. Moore, Tanja Bosak, Francis Macdonald, Kimberly Du, Sharon A. Newman, Daniel J.G. Lahr, Sara B. Pruss
Pyritized Cryogenian Cyanobacteria Fossils From Arctic Alaska, Kelsey R. Moore, Tanja Bosak, Francis Macdonald, Kimberly Du, Sharon A. Newman, Daniel J.G. Lahr, Sara B. Pruss
Geosciences: Faculty Publications
The Cryogenian was a time of climatic extremes, with two extended and severe global glaciations bracketing hothouse conditions. The effect of these extreme climate conditions on ocean chemistry and the marine biosphere remain poorly understood. Most of the previous studies of the fossil record from this interval focus on benthic organisms, with few examples of organisms with an inferred planktonic lifestyle and no firm evidence for photosynthetic organisms. Here, we present helically coiled, straight, and curved fossils composed of fine crystalline or framboidal pyrite in limestone samples from the Ikiakpuk formation of Arctic Alaska. These structures are morphologically identical to …
Influence Of The Megathrust Earthquake Cycle On Upper-Plate Deformation In The Cascadia Forearc Of Washington State, Usa, Jaime E. Delano, Colin B. Amos, John P. Loveless, Tammy M. Rittenour, Brian L. Sherrod, Emerson M. Lynch
Influence Of The Megathrust Earthquake Cycle On Upper-Plate Deformation In The Cascadia Forearc Of Washington State, Usa, Jaime E. Delano, Colin B. Amos, John P. Loveless, Tammy M. Rittenour, Brian L. Sherrod, Emerson M. Lynch
Geosciences: Faculty Publications
The influence of subduction zone earthquake cycle processes on permanent forearc deformation is poorly understood. In the Cascadia subduction zone forearc of Washington State, USA, deformed and incised fluvial terraces serve as archives of longer-term (103–104 yr) strain manifest as both fluvial incision and slip on upper-plate faults. We focus on comparing these geomorphic records in the Wynoochee River valley in the southern Olympic Mountains with short-term (101 yr) deformation driven by interseismic subduction zone coupling. We use optically stimulated luminescence dating and high-resolution elevation data to characterize strath terrace incision and differential uplift across the Canyon River fault, which …
Trilobite Extinctions, Facies Changes And The Roece Carbon Isotope Excursion At The Cambrian Series 2–3 Boundary, Great Basin, Western Usa, Luke E. Faggetter, Paul B. Wignall, Sara B. Pruss, Robert J. Newton, Yadong Sun, Stephen F. Crowley
Trilobite Extinctions, Facies Changes And The Roece Carbon Isotope Excursion At The Cambrian Series 2–3 Boundary, Great Basin, Western Usa, Luke E. Faggetter, Paul B. Wignall, Sara B. Pruss, Robert J. Newton, Yadong Sun, Stephen F. Crowley
Geosciences: Faculty Publications
The mass extinction of the olenellid trilobites occurred around the Cambrian Series 2–Series 3 boundary. Like many other crises, it coincided with a negative carbon isotope excursion but the associated palaeoenvironmental changes remain unclear. To investigate the causal mechanism for this event, we report facies changes, pyrite framboid petrography and carbon isotope values from Cambrian Series 2–Series 3 (traditionally Early–Middle Cambrian) boundary strata of the Carrara Formation (Death Valley region, California) and Pioche Formation (Nevada). These data reveal regionally changing water depths from high-energy, nearshore facies (oolitic grainstone) to more offshore silty marl and finer-grained carbonate mudstone. In the Carrara …