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Articles 1 - 14 of 14
Full-Text Articles in Geology
Sedimentary Dna And Molecular Evidence For Early Human Occupation Of The Faroe Islands, Lorelei Curtin, William J. D’Andrea, Nicholas L. Balascio, Sabrina Shirazi, Beth Shapiro, Gregory A. De Wet, Raymond S. Bradley, Jostein Bakke
Sedimentary Dna And Molecular Evidence For Early Human Occupation Of The Faroe Islands, Lorelei Curtin, William J. D’Andrea, Nicholas L. Balascio, Sabrina Shirazi, Beth Shapiro, Gregory A. De Wet, Raymond S. Bradley, Jostein Bakke
Geosciences: Faculty Publications
The Faroe Islands, a North Atlantic archipelago between Norway and Iceland, were settled by Viking explorers in the mid-9th century CE. However, several indirect lines of evidence suggest earlier occupation of the Faroes by people from the British Isles. Here, we present sedimentary ancient DNA and molecular fecal biomarker evidence from a lake sediment core proximal to a prominent archaeological site in the Faroe Islands to establish the earliest date for the arrival of people in the watershed. Our results reveal an increase in fecal biomarker concentrations and the first appearance of sheep DNA at 500 CE (95% confidence interval …
Unusual Intraclast Conglomerates In A Stormy, Hot-House Lake: The Early Triassic North China Basin, Kaixuan Ji, Paul B. Wignall, Jeff Peakall, Jinnan Tong, Daoliang Chu, Sara B. Pruss
Unusual Intraclast Conglomerates In A Stormy, Hot-House Lake: The Early Triassic North China Basin, Kaixuan Ji, Paul B. Wignall, Jeff Peakall, Jinnan Tong, Daoliang Chu, Sara B. Pruss
Geosciences: Faculty Publications
Early Triassic temperatures were some of the hottest of the Phanerozoic, sea-surface temperatures approached 40°C, with profound consequences for both the sedimentology and faunal distributions in the oceans. However, the impact of these temperatures in terrestrial settings is unclear. This study examines shallow lacustrine sediments from the Lower Triassic succession of North China. These consist of diverse fluvial to shallow lacustrine sandstones and also spectacular, coarse conglomerates composed of diverse, intraformational clasts reworked from the interbedded sediments. The conglomerate beds can show inverse grading and high angle, flat-pebble imbrication in their lower part and vertically orientated flat pebbles in their …
Investigating Strike-Slip Faulting Parallel To The Icelandic Plate Boundary Using Boundary Element Models, Anna E.R. Pearson, John P. Loveless
Investigating Strike-Slip Faulting Parallel To The Icelandic Plate Boundary Using Boundary Element Models, Anna E.R. Pearson, John P. Loveless
Geosciences: Faculty Publications
Most faults in Iceland strike roughly parallel to the divergent plate boundary, a part of the North American-Eurasian plate boundary, which would be expected to lead to primarily normal faulting. However, several studies have observed a significant component of rift-parallel strike-slip faulting in Iceland. To investigate these fault kinematics, we use the boundary element method to model fault slip and crustal stress patterns of the Icelandic tectonic system, including a spherical hotspot and uniaxial stress that represents rifting. On a network of faults, we estimate the slip required to relieve traction imposed by hotspot inflation and remote rifting stress and …
A New Phosphatized Ophiuroid From The Lower Triassic Of Nevada And Its Position In The Evolutionary History Of The Ophiuroidea (Echinodermata), Ben Thuy, Vivienne Maxwell, Sara B. Pruss
A New Phosphatized Ophiuroid From The Lower Triassic Of Nevada And Its Position In The Evolutionary History Of The Ophiuroidea (Echinodermata), Ben Thuy, Vivienne Maxwell, Sara B. Pruss
Geosciences: Faculty Publications
The Lower Triassic fossil record of brittle stars is relatively rich, yet most records published to date are based on poorly preserved or insufficiently known fossils. This hampers exhaustive morphological analyses, comparison with recent relatives or inclusion of Early Triassic ophiuroid taxa in phylogenetic estimates. Here, we describe a new ophiuroid from the Lower Triassic of Nevada, preserved as phosphatized skeletal parts and assigned to the new taxon Ophiosuperstes praeparvus gen. et sp. nov Maxwell, V. Pruss. S.B. This unusual preservation of the fossils allowed for acid-extraction of an entire suite of dissociated skeletal parts, including lateral arm plates, ventral …
The Sedimentary Geochemistry And Paleoenvironments Project, Úna C. Farrell, Rifaat Samawi, Savitha Anjanappa, Roman Klykov, Oyeleye O. Adeboye, Heda Agic, Anne Sofie C. Ahm, Thomas H. Boag, Fred Bowyer, Jochen J. Brocks, Tessa N. Brunoir, Donald E. Canfield, Xiaoyan Chen, Meng Cheng, Matthew O. Clarkson, Devon B. Cole, David R. Cordie, Peter W. Crockford, Huan Cui, Tais W. Dahl, Lucas D. Mouro, Keith Dewing, Stephen Q. Dornbos, Nadja Drabon, Julie A. Dumoulin, Joseph F. Emmings, Cecilia R. Endriga, Tiffani A. Fraser, Robert R. Gaines, Richard M. Gaschnig, Timothy M. Gibson, Geoffrey J. Gilleaudeau
The Sedimentary Geochemistry And Paleoenvironments Project, Úna C. Farrell, Rifaat Samawi, Savitha Anjanappa, Roman Klykov, Oyeleye O. Adeboye, Heda Agic, Anne Sofie C. Ahm, Thomas H. Boag, Fred Bowyer, Jochen J. Brocks, Tessa N. Brunoir, Donald E. Canfield, Xiaoyan Chen, Meng Cheng, Matthew O. Clarkson, Devon B. Cole, David R. Cordie, Peter W. Crockford, Huan Cui, Tais W. Dahl, Lucas D. Mouro, Keith Dewing, Stephen Q. Dornbos, Nadja Drabon, Julie A. Dumoulin, Joseph F. Emmings, Cecilia R. Endriga, Tiffani A. Fraser, Robert R. Gaines, Richard M. Gaschnig, Timothy M. Gibson, Geoffrey J. Gilleaudeau
Geosciences: Faculty Publications
No abstract provided.
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 …