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Articles 1 - 9 of 9
Full-Text Articles in Physical Sciences and Mathematics
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.