Earth Sciences Commons^™

A Model Of Icewedge Polygon Drainage In Changing Arctic Terrain, Vitaly Zlotnik, Dylan R. Harp, Elchin E. Jafarov, Charles J. Abolt

Department of Earth and Atmospheric Sciences: Faculty Publications

As ice wedge degradation and the inundation of polygonal troughs become increasingly common processes across the Arctic, lateral export of water from polygonal soils may represent an important mechanism for the mobilization of dissolved organic carbon and other solutes. However, drainage from ice wedge polygons is poorly understood. We constructed a model which uses cross-sectional flow nets to define flow paths of meltwater through the active layer of an inundated low-centered polygon towards the trough. The model includes the eects of evaporation and simulates the depletion of ponded water in the polygon center during the thaw season. In most simulations, …

Diagnostic Analysis Of Bank Storage Effects On Sloping Floodplains, Xiuyu Liang, Vitaly Zlotnik, You‐Kuan Zhang, Pei Xin

Department of Earth and Atmospheric Sciences: Faculty Publications

Stream bank storage effects during floods have received limited attention, despite the significant role of such floods in aquifer water budgets. One reason is the complexity of geometry of the problem, which commonly has been treated numerically. Using a simple model in a domain with moving boundary, a semianalytical solution for bank storage effects is proposed to account for stream stage hydrograph, floodplain slope, and aquifer parameters. The results extend classic solutions by Cooper and Rorabaugh (1963, https://doi.org/10.3133/wsp1536J) for idealized vertical streambanks but applied to realistic floodplain cross sections. The accuracy of the semianalytical solution is verified by a one‐dimensional …

Assessing Agricultural Risk Management Using Historic Crop Insurance Loss Data Over The Ogallala Aquifer, Julian Reyes, Emile Elias, Erin M.K. Haacker, Amy Kremen, Lauren Parker, Caitlin Rottler

Department of Earth and Atmospheric Sciences: Faculty Publications

Much of the agricultural production in the Ogallala Aquifer region relies on groundwater for irrigation. In addition to declining water levels, weather and climate-driven events affect crop yields and revenues. Crop insurance serves as a risk management tool to mitigate these perils. Here, we seek to understand what long-term crop insurance loss data can tell us about agricultural risk management in the Ogallala. We assess patterns and trends in crop insurance loss data from the U.S. Department of Agriculture Risk Management Agency. Indemnities, or insurance payments, totaled $22 billion from 1989–2017 for the 161 counties that overlie the Ogallala Aquifer. …

Disdrometer, Polarimetric Radar, And Condensation Nuclei Observations Of Supercell And Multicell Storms On 11 June 2018 In Eastern Nebraska, Matthew S. Van Den Broeke

Department of Earth and Atmospheric Sciences: Faculty Publications

Disdrometer and condensation nuclei (CN) data are compared with operational polarimetric radar data for one multicell and one supercell storm in eastern Nebraska on 11 June 2018. The radar was located ~14.3 km from the instrumentation location and provided excellent observation time series with new low-level samples every 1–2 min. Reflectivity derived by the disdrometer and radar compared well, especially in regions with high number concentration of drops and reflectivity <45 dBZ. Differential reflectivity also compared well between the datasets, though it was most similar in the supercell storm. Rain rate calculated by the disdrometer closely matched values estimated by the radar when reflectivity and differential reflectivity were used to produce the estimate. Concentration of CN generally followed precipitation intensity for the leading convective cell, with evidence for higher particle concentration on the edges of the convective cell associated with outflow. The distribution of CN in the supercell was more complex and generally did not follow precipitation intensity.

Mod$$At: A Hydro-Economic Modeling Framework For Aquifer Management In Irrigated Agricultural Regions, Mani Rouhi Rad, Erin M.K. Haacker, Vaishali Sharda, Soheil Nozari, Zaichen Xiang, A. Araya, Venkatesh Uddameri, Jordan Suter, Prasanna Gowda

Department of Earth and Atmospheric Sciences: Faculty Publications

In this paper, we introduce a hydro-economic modeling framework for the management of groundwater re- sources that are used for irrigated agricultural production. The model, MOD$$AT, can be used to study the costs of aquifer depletion and the net benefits of specific aquifer management policies. MOD$$AT is composed of three components, namely, an economic component, a hydrologic component and an agronomic component. A main goal of this paper is to introduce the hydro-economic model and describe how it can be transferable to different contexts. With this objective in mind, we describe model components step-by-step so that the process of integration …

Data Generated During The 2018 Lapse-Rate Campaign: An Introduction And Overview, Gijs De Boer, Adam Houston, Et Al.

Department of Earth and Atmospheric Sciences: Faculty Publications

Unmanned aircraft systems (UASs) offer innovative capabilities for providing new perspectives on the atmosphere, and therefore atmospheric scientists are rapidly expanding their use, particularly for studying the planetary boundary layer. In support of this expansion, from 14 to 20 July 2018 the International Society for Atmospheric Research using Remotely piloted Aircraft (ISARRA) hosted a community flight week, dubbed the Lower Atmospheric Profiling Studies at Elevation – a Remotely-piloted Aircraft Team Experiment (LAPSE- RATE; de Boer et al., 2020a). This field campaign spanned a 1-week deployment to Colorado’s San Luis Valley, involving over 100 students, scientists, engineers, pilots, and outreach coordinators. …

Assessing The Hierarchy Of Long-Term Environmental Controls On Diatom Communities Of Yellowstone National Park Using Lacustrine Sediment Records, Victoria Chraibi, Sherilyn C. Fritz

Department of Earth and Atmospheric Sciences: Faculty Publications

An ecosystem’s ability to maintain structure and function following disturbance, defined as resilience, is influenced by a hierarchy of environmental controls, including climate, surface cover, and ecological relationships that shape biological community composition and productivity. This study examined lacustrine sediment records of naturally fishless lakes in Yellowstone National Park to reconstruct the response of aquatic communities to climate and trophic cascades from fish stocking. Sediment records of diatom algae did not exhibit a distinct response to fish stocking in terms of assemblage or algal productivity. Instead, 3 of 4 lakes underwent a shift to dominance by benthic diatom species from …

Surficial Fractures In The Navajo Sandstone, South-Western Usa: The Roles Of Thermal Cycles, Rainstorms, Granular Disintegration, And Iterative Cracking, David Loope, Garrison R. Loope, Caroline M. Burberry, Clinton Rowe, Gerald C. Bryant

Department of Earth and Atmospheric Sciences: Faculty Publications

Deep (> 5 m) sheeting fractures in the Navajo sandstone are evident at numerous sites in southern Utah and derive from tectonic stresses. Strong diurnal thermal cycles are, however, the likely triggers for shallow (< 0.3 m) sheeting fractures. Data from subsurface thermal sensors reveal that large temperature differences between sensors at 2 and 15 cm depth on clear summer afternoons are as great as those that trigger sheeting fractures in exposed California granite. Extensive polygonal patterns in the Navajo sandstone are composed of surface-perpendicular fractures and were produced by contractile stresses. Numerous studies have shown that porewater diminishes the tensile strength of sandstone. Based on our thermal records, we propose that cooling during monsoonal rainstorms triggers polygonal fracturing of temporarily weakened rock. On steep outcrops, polygonal patterns are rectilinear and orthogonal, with T-vertices. Lower-angle slopes host hexagonal patterns (defined by the dominance of Y-vertices). Intermediate patterns with rectangles and hexagons of similar scale are common. We posit that outcropping fractures are advancing downward by iterative steps, and that hexagons on sandstone surfaces (like prismatic columns of basalt) have evolved from ancestral orthogonal polygons of similar scale. In lava flows, fractures elongate intermittently as they follow a steep thermal gradient (the source of stress) as it rapidly moves through the rock mass. In our model, a steep, surficial thermal gradient descends through unfractured sandstone, but at the slow pace of granular disintegration. Through time, as the friable rock on stable slopes erodes, iterative cracking advances into new space. Hexagonal patterns form as new fractures, imperfectly guided by the older ones, propagate in new directions, and vertices drift into a configuration that minimizes the ratio of fracture length to polygon area.

Spatial And Temporal Ecological Uniqueness Of Andean Diatom Communities Are Correlated With Climate, Geodiversity And Long-Term Limnological Change, Xavier Benito, Annika Vilmi, Melina Luethje, Maria Laura Carrevedo, Marja Lindholm, Sherilyn C. Fritz

Department of Earth and Atmospheric Sciences: Faculty Publications

High-elevation tropical lakes are excellent sentinels of global change impacts, such as climate warming, land-use change, and atmospheric deposition. These effects are often correlated with temporal and spatial beta diversity patterns, with some local communities contributing more than others, a phenomenon known as local contribution to beta diversity (LCBD) or ecological uniqueness. Microorganisms, such as diatoms, are considered whole-ecosystem indicators, but little is known about their sensitivity and specificity in beta diversity studies mostly because of the lack of large spatial and temporal datasets. To fill this gap, we used a tropical South American diatom database comprising modern (144 lakes) …

The Influence Of Isolated Thunderstorms And The Low-Level Wind Field On Nocturnally Migrating Birds In Central North America, Matthew S. Van Den Broeke, Timothy J. Gunkel

Department of Earth and Atmospheric Sciences: Faculty Publications

Seasonal bird migration occurs on large spatial scales and is influenced by many factors including weather conditions. Weather can include thunderstorms, which may force migrants to land or cause them to reroute a migration path. In this study, a sample of isolated thunderstorms was analyzed from the domains of three weather radars in the central United States to test hypotheses regarding the influence of thunderstorms on the distribution of migrants. Migrating bird density was often reduced in the wake of storms, and this wake reduction was typically more pronounced for larger, more intense and faster- moving storms, particularly in eastern …

The Influence Of Isolated Thunderstorms And The Low-Level Wind Field On Nocturnally Migrating Birds In Central North America, Matthew V.D. Broeke, Timothy J. Gunkel

Department of Earth and Atmospheric Sciences: Faculty Publications

Seasonal bird migration occurs on large spatial scales and is influenced by many factors including weather conditions. Weather can include thunderstorms, which may force migrants to land or cause them to reroute a migration path. In this study, a sample of isolated thunderstorms was analyzed from the domains of three weather radars in the central United States to test hypotheses regarding the influence of thunderstorms on the distribution of migrants. Migrating bird density was often reduced in the wake of storms, and this wake reduction was typically more pronounced for larger, more intense and faster- moving storms, particularly in eastern …

Controls On Channel Deposits Of Highly Variable Rivers: Comparing Hydrology And Event Deposits In The Burdekin River, Australia, Jan Alexander, Christopher M. Herbert, Christopher R. Fielding, Kathryn J. Amos

Department of Earth and Atmospheric Sciences: Faculty Publications

Discharge event frequency, magnitude and duration all control river chan- nel morphology and sedimentary architecture. Uncertainty persists as to whether alluvial deposits in the rock record are a time-averaged amalgam from all discharge events, or a biased record of larger events. This paper investigates the controls on channel deposit character and subsurface strati- graphic architecture in a river with seasonal discharge and very high inter- annual variability, the Burdekin River of north-east Australia. In such rivers, most sediment movement is restricted to a few days each year and at other times little sediment moves. However, the maximum discharge magnitude does …

End-Permian (252 Mya) Deforestation, Wildfires And Flooding—An Ancient Biotic Crisis With Lessons For The Present, Vivi Vajda, Stephen Mcloughlin, Chris Mays, Tracy D. Frank, Christopher R. Fielding, Allen Tevyaw, Veiko Lehsten, Malcolm Bocking, Robert S. Nicoll

Department of Earth and Atmospheric Sciences: Faculty Publications

Current large-scale deforestation poses a threat to ecosystems globally, and imposes substantial and prolonged changes on the hydrological and carbon cycles. The tropical forests of the Amazon and Indonesia are currently undergoing deforestation with catastrophic ecological consequences but widespread deforestation events have occurred several times in Earth’s history and these provide lessons for the future. The end-Permian mass-extinction event (EPE; ∼252 Ma) provides a global, deep-time analogue for modern deforestation and diversity loss. We undertook centimeter-resolution palynological, sedimentological, carbon stable-isotope and paleobotanical investigations of strata spanning the end- Permian event at the Frazer Beach and Snapper Point localities, in the …

Crustal Architecture Of The Northwestern And Central Gulf Of Mexico From Integrated Geophysical Analysis, Irina Filina

Department of Earth and Atmospheric Sciences: Faculty Publications

The tectonic history of the Gulf of Mexico (GOM) is a subject for ongoing debate. The nature of the crust in the northwestern and central parts of the basin remains poorly understood. Joined interpretation of two 2D seismic cross sections—GUMBO1 and GUMBO2—with potential fields (gravity and magnetics) constrained with available well data allows testing various hypotheses about the subsurface structures and crustal architecture in the study area. In the northwestern GOM, two contradicting hypotheses about the nature of the crust were tested—exhumed mantle versus a thinned and intruded continental crust resulted from magma-rich rifting. The nature of the crust was …

Measurement And Characterization Of Infrasound From A Tornado Producing Storm, Brian R. Elbing, Christopher E. Petrin, Matthew Van Den Broeke

Department of Earth and Atmospheric Sciences: Faculty Publications

A hail-producing supercell on 11 May 2017 produced a small tornado near Perkins, Oklahoma (35.97, –97.04) at 2013 UTC. Two infrasound microphones with a 59-m separation and a regional Doppler radar station were located 18.7 and 70 km from the tornado, respectively. Elevated infrasound levels were observed starting 7min before the verified tornado. Infrasound data below ~5Hz was contaminated with wind noise, but in the 5–50 Hz band the infrasound was independent of wind speed with a bearing angle that was consistent with the movement of the storm core that produced the tornado. During the tornado, a 75 dB peak …

Integrated Imaging: A Powerful But Undervalued Tool, Irina Filina, Ed K. Biegert, Luise Sander, Victoria Tschirhart, Neda Bundalo, Cara Schiek-Stewart

Department of Earth and Atmospheric Sciences: Faculty Publications

Following the 2018 SEG Annual Meeting, the Gravity and Magnetics Committee held a postconvention workshop titled “Integrated Imaging.” The half-day workshop attracted nearly 50 participants from various backgrounds. Three primary objectives of the workshop were to explore the nonseismic toolbox, highlight real examples of integrated projects that benefited (or did not benefit) from nonseismic data, and provide geoscientists from all backgrounds a learning opportunity to see how they might optimize the value of their imaging projects via integration with relatively low-cost nonseismic methods. The workshop had a highly interactive format that differed from traditional presentation-based settings. After eight brief case …

La Evolucion De Glaciares De Escombros Y Morenas En La Cuenca Del Rio Blanco, Mendoza, William J. Wayne

Department of Earth and Atmospheric Sciences: Faculty Publications

RESUMEN: La subcuenca del río Blanco en el cordón del Plata, que incluye los valles de Angostura y Vallecitos, tiene 85 km², de los cuales 4.7 km² son de glaciares de escombros activos, 7.4 km" de glaciares de escombros fósiles y morrenas. Los dos valles con rumbo al sureste son erosionados en rocas volcánicas y contienen largas lenguas de glaciares de escombros que se extienden hasta los 3.300 m. Los dos valles con rumbo al este tuvieron glaciares hasta tiempos recientes y en uno de ellos aún existe un glaciar cubierto. Los glaciares de escombros en …

Using Artificial Neural Networks To Predict Future Dryland Responses To Human And Climate Disturbances, C.E. Buckland, R.M. Bailey, D.S.G. Thomas

Department of Earth and Atmospheric Sciences: Faculty Publications

Land degradation and sediment remobilisation in dryland environments is considered to be a significant global environmental problem. Given the potential for currently stabilised dune systems to reactivate under climate change and increased anthropogenic pressures, identifying the role of external disturbances in driving geomorphic response is vitally important. We developed a novel approach, using artificial neural networks (ANNs) applied to time series of historical reactivation-deposition events from the Nebraska Sandhills, to determine the relationship between historic periods of sand deposition in semi-arid grasslands and external climatic conditions, land use pressures and wildfire occurrence. We show that both vegetation growth and sediment …

The Influence Of Fetch On The Holocene Thermal Structure Of Hidden Lake, Glacier National Park, Jeffery R. Stone, Jasmine E. Saros, Trisha L. Spanbauer

Department of Earth and Atmospheric Sciences: Faculty Publications

We use three-dimensional modeling of the basin of Hidden Lake, Montana, to assess the influence of effective fetch on diatom-inferred changes in mixing depths throughout the Holocene. The basin of Hidden Lake is characterized by a complex morphometry; for example, three-dimensional modeling of the lake basin indicates that a decrease in lake level of 2 m would result in complete isolation of the deepest part of the lake basin from the rest of the lake. Our model suggests that small changes in the lake surface elevation at Hidden Lake would produce threshold-like responses in effective fetch, which in turn would …

Testing Pyroxenite Versus Peridotite Sources For Marine Basalts Using U-Series Isotopes, Lynne J. Elkins, Bernard Bourdon, Sarah Lambart

Department of Earth and Atmospheric Sciences: Faculty Publications

Geochemically enriched signatures in global oceanic basalts have long indicated a heterogeneous mantle source, but the role of lithologic heterogeneity in producing mantle partial melts, particularly fertile pyroxenite rocks, remains unclear. Uranium-series disequilibria in basalts are particularly sensitive to the increased garnet mode and melting rates of pyroxenite rocks, making the system a useful indicator of mantle lithologic heterogeneity in the melt region for oceanic basalts. Here we summarize evidence for the presence and importance of pyroxenite rocks in the upper mantle and their role in melt generation of mid-ocean ridge basalts and ocean island basalts, with a synthesis of …

Spatiotemporal Changes In Extreme Precipitation And Its Dependence On Topography Over The Poyang Lake Basin, China, Xianghu Li, Qi Hu

Department of Earth and Atmospheric Sciences: Faculty Publications

Spatiotemporal changes in extreme precipitation at local scales in the context of climate warming are overwhelmingly important for prevention and mitigation of water-related disasters and also provide critical information for effective water resources management. In this study, the variability and trends of extreme precipitation in both time and space in the Poyang Lake basin over the period of 1960–2012 are analyzed. Also, changes in precipitation extremes with topography are investigated, and possible causes are briefly discussed. ,e results show that extreme precipitation over the Poyang Lake basin is intensified during the last 50 years, especially the increasing trends are more …

Sensitivity Of Potential Groundwater Recharge To Projected Climate Change Scenarios: A Site-Specific Study In The Nebraska Sand Hills, Usa, Zablon A. Adane, Vitaly A. Zlotnik, Nathan R. Rossman, Tiejun Wang, Paolo Nasta

Department of Earth and Atmospheric Sciences: Faculty Publications

Assessing the relationship between climate forcings and groundwater recharge (GR) rates in semi-arid regions is critical for water resources management. This study presents the impact of climate forecasts on GR within a probabilistic framework in a site-specific study in the Nebraska Sand Hills (NSH), the largest stabilized sand dune region in the USA containing the greatest recharge rates within the High Plains Aquifer. A total of 19 downscaled climate projections were used to evaluate the impact of precipitation and reference evapotranspiration on GR rates simulated by using HYDRUS 1-D. The analysis of the decadal aridity index (AI) indicates that climate …

Effects Of The Sea Breeze Circulation On Soil Temperature Over Kuwait Using In Situ Observations And The Ecmwf Model, Hussain Alsarraf, Matthew V.D. Broeke, Hala Aljassar

Department of Earth and Atmospheric Sciences: Faculty Publications

Background: The mesoscale circulation over Kuwait is an important influence on changes in surface temperatures and soil temperatures.

Introduction: This paper presents two common summertime atmospheric features over Kuwait linking wind circulation to soil temperatures.

Methods: In this study, we use the European Centre for Medium-range Weather Forecasts ECMWF reanalysis ERA-Interim dataset to investigate effects of the synoptic scale and mesoscale circulations.

Results: The results show that a large-scale pressure gradient in summer typically leads to northerly winds over Kuwait, while a weak synoptic-scale pressure gradient leads to light easterly humid winds from the Persian Gulf, consistent with a mesoscale …

Defining The Morphological Quality Of Fossil Footprints. Problems And Principles Of Preservation In Tetrapod Ichnology With Examples From The Palaeozoic To The Present, Lorenzo Marchetti, Matteo Belvedere, Sebastian Voigt, Hendrik Klein, Diego Castanera, Ignacio Díaz-Martínez, Daniel Marty, Lida Xing, Silverio Feola, Ricardo N. Melchor, James O. Farlow

Department of Earth and Atmospheric Sciences: Faculty Publications

The morphology of fossil footprints is the basis of vertebrate footprint ichnology. However, the processes acting during and after trace fossil registration which are responsible for the final morphology have never been precisely defined, resulting in a dearth of nomenclature. Therefore, we discuss the concepts of ichnotaphonomy, ichnostratinomy, taphonomy, biostratinomy, registration and diagenesis and describe the processes acting on footprint morphology. In order to evaluate the morphological quality of tetrapod footprints, we introduce the concept of morphological preservation, which is related to the morphological quality of footprints (M-preservation, acronym MP), and distinguish it from physical preservation (P-preservation, acronym PP), which …

Plant Root Systems Preserved In The Permian Cedar Mesa Sandstone At Moki Dugway, Southeastern Utah, David Loope

Department of Earth and Atmospheric Sciences: Faculty Publications

Rooted green plants represent the base of the food chain for most terrestrial ecosystems, but, compared to animal burrows, root systems are relatively rarely recognized in ancient sedimentary rocks. Plant roots that penetrate unconsolidated sand dunes, especially those containing not only quartz grains, but also abundant grains of calcite (CaCO₃), are commonly replaced by fine crystals of calcite (Klappa, 1980). These structures (known by geologists as rhizoliths from the Greek for “root rock”) are one form of calcite cemented soil and sediment called caliche (Figure 1). Caliche crystallizes well above the water table and its calcite crystals are …

Cut, Fill, Repeat: Slot Canyons Of Dry Fork, Kane County, David Loope

Department of Earth and Atmospheric Sciences: Faculty Publications

The slot canyons of southern Utah (figure 1) have become popular destinations for hikers, climbers, and photographers. For most of these canyons, the geology is simple: sediment carried by flowing water abrades a thick, homogeneous sandstone. As time passes, the rate of down-cutting is rapid compared to the rate of cliff retreat. End of story. The strange abundance and configuration of the slot canyons along Dry Fork Coyote (a tributary of Coyote Gulch and the Escalante River), however, have a convoluted geologic history that is climate-driven and involves canyon cutting, canyon filling, and more canyon cutting.

Multi-Proxy Constraints On The Significance Of Covariant Δ13c Values In Carbonate And Organic Carbon During The Early Mississippian, Amanda M. Oehlert, Peter K. Swart, Gregor P. Eberli, Samantha Evans, Tracy D. Frank

Department of Earth and Atmospheric Sciences: Faculty Publications

This study investigates the covariation between carbonate and organic δ¹³C values in a proximal to distal transect of four outcrops in the Madison Limestone in the Western United States Rockies, combined with δ³⁴S values of carbonate associated sulphate, the concentration of acid-insoluble material and measurements of total organic carbon. These new geochemical datasets not only allow for an evaluation of carbon isotope covariance during one of the largest perturbations to the global carbon cycle over the past 550 Myr, but also constrain the cause of the excursion in carbonate δ¹³C values. The results support …

The Origin Of Shinarump Wonderstone, Hildale, Washington County, Richard Kettler, David Loope

Department of Earth and Atmospheric Sciences: Faculty Publications

Southern Utah’s “wonderstone” is Shinarump sandstone, variably cemented and stained with iron oxide, forming intricate patterns reminiscent of landscapes. It is cut and sold as absorbent drink coasters and decorative objects, and is seen in rock shops across the country. The wonderstone pattern comprises thick bands of iron oxide mineralization that fills pore space (referred to as iron oxide cement or IOC) and more delicate bands of iron oxide mineralization that coats sand grains but does not fill pore space (referred to as iron oxide stain or IOS) (figure 1).

The wonderstone pattern is of interest to geologists because it …

Crustal Structure Of Mesozoic Rifting In The Northeastern Gulf Of Mexico From Integration Of Seismic And Potential Fields Data, Mei Liu, Irina Filina, Paul Mann

Department of Earth and Atmospheric Sciences: Faculty Publications

We have investigated the crustal structure of a 400 km wide zone of thinned continental crust in the northeastern Gulf of Mexico (GOM) using gravity and magnetic modeling along two deeply penetrated seismic transects. Using this approach, we identify two zones of prominent, southward-dipping reflectors associated with 7–10 km thick, dense, and highly magnetic material. Previous workers have interpreted the zones as either coarse clastic redbeds of Mesozoic age that are tilted within half-grabens or seaward-dipping reflectors of magmatic origin. Both seismic reflection lines reveal a 10 km thick and 67 km wide northern zone of high density near the …

Age And Pattern Of The Southern High-Latitude Continental End-Permian Extinction Constrained By Multiproxy Analysis, Christopher R. Fielding, Tracy D. Frank, Stephen Mcloughlin, Vivi Vajda, Chris Mays, Allen P. Tevyaw, Arne Winguth, Cornelia Winguth, Robert S. Nicoll, Malcom Bocking, James L. Crowley

Department of Earth and Atmospheric Sciences: Faculty Publications

Past studies of the end-Permian extinction (EPE), the largest biotic crisis of the Phanerozoic, have not resolved the timing of events in southern high-latitudes. Here we use palynology coupled with high-precision CA-ID-TIMS dating of euhedral zircons from continental sequences of the Sydney Basin, Australia, to show that the collapse of the austral Permian Glossopteris flora occurred prior to 252.3 Ma (~370 kyrs before the main marine extinction). Weathering proxies indicate that floristic changes occurred during a brief climate perturbation in a regional alluvial landscape that otherwise experienced insubstantial change in fluvial style, insignificant reorganization of the depositional surface, and no …