Courtney Sprain

University of Florida | UF · Department of Geological Sciences

Palaeomagnetic field intensity measurements, derived from rocks with ages that span geological time, provide a crucial constraint on the evolution of Earth’s deep interior and its magnetic environment. The palaeointensity database PINT has been updated to version v.8.0.0 and includes palaeointensity site-mean records spanning an interval from 50 ka...

The Mesozoic Dipole Low (MDL) is a period, covering at least ∼80 My, of low dipole moment that ended at the start of the Cretaceous Normal Superchron. Recent studies of Devonian age Siberian localities identified similarly low field values a few tens of million years prior to the Permo-Carboniferous Reverse Superchron (PCRS). To constrain the lengt...

The Cretaceous-Paleogene boundary (KPB) in the Hell Creek area of Montana is recognized in several places by an iridium anomaly, which is typically identified at or very near the lithological contact between the Hell Creek Formation and the Tullock Member of the Fort Union Formation. Previous work in the area has argued that organic carbon isotope...

Plain Language Summary Earth's magnetic field varies on a wide range of timescales, from less than a year to hundreds of millions of years and longer. Such variations are produced by the complex fluid dynamic processes in the liquid iron core, which are generally studied using three‐dimensional computer simulations. While these simulations reproduc...

Plesiadapiform mammals, as stem primates, are key to understanding the evolutionary and ecological origins of Pan-Primates and Euarchonta. The Purgatoriidae, as the geologically oldest and most primitive known plesiadapiforms and one of the oldest known placental groups, are also central to the evolutionary radiation of placentals and the Cretaceou...

Multiple scaling schemes for cosmogenic nuclide production rates have been developed for the late Quaternary, the period over which most cosmogenic nuclide measurements are applicable. Applications of cosmogenic nuclide measurements on longer timescales to address questions regarding landscape evolution and surface exposure durations are becoming m...

Despite significant progress in paleomagnetic research over the last century, the origin, evolution, and long-term behavior of the geomagnetic field remains poorly understood. One significant open question is when and how the inner core nucleated. Since geomagnetic field behavior is thought to be linked to thermal evolution in the core, scientists...

A defining characteristic of the recent geomagnetic field is its dominant axial dipole which provides its navigational utility and dictates the shape of the magnetosphere. Going back through time, much less is known about the degree of axial dipole dominance. Here we use a substantial and diverse set of 3D numerical dynamo simulations and recent ob...

A defining characteristic of the recent geomagnetic field is its dominant axial dipole which provides its navigational utility and dictates the shape of the magnetosphere. Going back through time, much less is known about the degree of axial dipole dominance. Here we use a substantial and diverse set of 3D numerical dynamo simulations and recent ob...

Deccan Traps flood basalt volcanism affected ecosystems spanning the end‐Cretaceous mass extinction, with the most significant environmental effects hypothesized to be a consequence of the largest eruptions. The Rajahmundry Traps are the farthest exposures (~1,000 km) of Deccan basalt from the putative eruptive centers in the Western Ghats and henc...

Determining the strength of the ancient geomagnetic field is vital to our understanding of the core and geodynamo, but obtaining reliable measurements of the paleointensity is fraught with difficulties. Over a quarter of magnetic field strength estimates within the global paleointensity database from 0 to 5 Ma come from Hawaii. Two previous studies...

The 40Ar/39Ar dating method is among the most versatile of geochronometers, having the potential to date a broad variety of K-bearing materials spanning from the time of Earth’s formation into the historical realm. Measurements using modern noble-gas mass spectrometers are now producing 40Ar/39Ar dates with analytical uncertainties of ∼0.1%, thereb...

We studied two partly overlapping sections in limestones in southern Cumbria, to constrain a magnetostratigraphy through most of the Visean (Fig. 1, 4) (early Carboniferous), Meathop quarry and Trowbarrow quarry. The Visean in this area is roughly 650 m thick and is composed of grainstones, packstones and wackestones, with minor amounts of shale. A...

Long-term temporal variations of the magnetic field (timescales >10 Myr), characterized from paleomagnetic data, have been hypothesized to reflect the evolution of Earth's deep interior and couplings between the core and mantle. By tying observed changes in the paleomagnetic record to mechanisms predicted from numerical geodynamo simulations, we ha...

Deccan Traps continental flood basalt eruptions spanned the Cretaceous-Paleogene mass extinction, erupting over a million cubic kilometers of basalt over a total duration of approximately a million years. The environmental consequences of flood basalt eruptions depend on the timing and amount of volatile release; eruption rates are thus needed to e...

The global paleointensity database for 65-200 Ma was analyzed using a modified suite of paleointensity quality criteria (QPI) such that the likely reliability of measurements is assessed objectively and as consistently as possible across the diverse dataset. This interval was chosen because of dramatic extremes of geomagnetic polarity reversal freq...

Large Igneous Provinces (LIPs) impact climate through the release of CO2 and SO2. The climate effects of these volatiles, particularly SO2, are highly dependent on the rate of emission, and thus high-resolution LIP eruptive fluxes can predict potential climate impacts – assuming eruptive degassing is the primary form of volatile release. While main...

Summarize the results from Cumbria, on 2 sites: Meathop and Trowbarrow quarry, the Magnetic measurements on Carboniferous limestones.

Magnetostratigraphy of Cumbrian Lower Carboniferous

Late Cretaceous records of environmental change suggest that Deccan Traps (DT) volcanism contributed to the Cretaceous-Paleogene boundary (KPB) ecosystem crisis. However, testing this hypothesis requires identification of the KPB in the DT. We constrain the location of the KPB with high-precision argon-40/argon-39 data to be coincident with changes...

Changes in mammalian faunal composition and structure following the Cretaceous- Paleogene mass extinction are central to understanding not only how terrestrial communities recovered from this ecological perturbation but also the evolution of archaic groups leading to extant mammalian clades. Here, we analyzed changes in mammalian local faunas durin...

Palaeomagnetic data from ancient rocks are one of the few types of observational data that can be brought to bear on the long-term evolution of Earth's core. A recent compilation of palaeointensity estimates from throughout Earth history has been interpreted to indicate that Earth's magnetic field strength increased in the Mesoproterozoic (between...

The mass extinction at the Cretaceous- Paleogene boundary marks one of the most important biotic turnover events in Earth history. Yet, despite decades of study, the causes of the Cretaceous-Paleogene boundary crises remain under debate. An important tool that has the capacity to greatly improve our understanding of the events around the Cretaceous...

The history of the Earth's magnetic field, comprised of geomagnetic polarity reversals, secular variation and field strength, is crucial for understanding the geodynamo and planetary evolution. However, the question whether the long-term variations of these basic features of geomagnetic field have been intrinsically related, or they have varied ind...

The Deccan Traps are a continental Large Igneous Province covering large swaths of west-central India, with onshore erupted lava volumes that may have exceeded one million cubic kilometers. Although the total duration of magmatism is a matter of debate, recent geochronological work has demonstrated that the vast majority of volcanism occurred in a...

Paleomagnetism of the North American Midcontinent Rift provides a robust paleogeographic record of Laurentia (cratonic North America) from ca. 1110 to 1070 Ma, revealing rapid equatorward motion of the continent throughout rift magmatism. Existing age and paleomagnetic constraints on the youngest rift volcanic and sedimentary rocks have been interp...

The Deccan Traps are a continental Large Igneous Province covering large swaths of west-central India, with onshore erupted lava volumes that may have exceeded one million cubic kilometers. Although the total duration of magmatism is a matter of debate, recent geochronological work has demonstrated that the vast majority of volcanism occurred in a...

A recent study of the Matuyama–Brunhes (M-B) geomagnetic field reversal recorded in exposed lacustrine sediments from the Sulmona Basin (Italy) provided a continuous, highresolution record indicating that the reversal of the field direction at the terminus of the M-B boundary (MBB) occurred in less than a century, about 786 ka ago. In the sediment,...

Intermediate composition titanohematite, Fe2-yTiyO3 with 0.5 ≤ y ≤ 0.7, is seldom the focus of paleomagnetic study and is commonly believed to be rare in nature. While largely overlooked in magnetostratigraphic studies, intermediate titanohematite has been identified as the dominant ferrimagnetic mineral in an array of Late Mesozoic and Early Cenoz...

Bolide impact and flood volcanism compete as leading candidates for the cause of terminal-Cretaceous mass extinctions. High-precision 40Ar/39Ar data indicate that these two mechanisms may be genetically related, and neither can be considered in isolation. The existing Deccan Traps magmatic system underwent a state shift approximately coincident wit...

An excellent record of environmental and paleobiological change around the Cretaceous-Paleogene boundary is preserved in the Hell Creek and Fort Union Formations in the western Williston Basin of northeastern Montana. These records are present in fluvial deposits whose lateral discontinuity hampers longdistance correlation. Geochronology has been f...

Paleointensity is one of the least deter­mined parameters in geomagnetism, yet this information has the potential to address many fundamental geophysical problems that bear on the evolution of the Earth's core and lower mantle. We test two important hy­potheses that affect our understanding of how paleointensity has changed in Earth's past: (1) the...

Past orbital analogues to the current interglacial, such as Marine Isotope Stage 19c (MIS 19c, ca. 800 ka), can provide reliable reference intervals for evaluating the timing and the duration of the Holocene and factors inherent in its climatic progression. Here we present the first high-resolution paleoclimatic record for MIS 19 anchored to a...

New constraints on the timing of the Cre-taceous-Paleogene mass extinction and the Chicxulub impact, together with a particularly voluminous and apparently brief erup-tive pulse toward the end of the " main-stage " eruptions of the Deccan continental fl ood ba-salt province suggest that these three events may have occurred within less than about a...

Detailed understanding of ecosystem decline and recovery attending the Cretaceous-Paleogene boundary (KPB) mass extinctions is hindered by limited constraints on the pace and tempo of environmental events near the boundary. To mitigate this shortcoming, high-resolution 40Ar/39Ar geochronology was performed on tephras intercalated between fossilifer...

We report a palaeomagnetic investigation of the last full geomagnetic field reversal, the Matuyama-Brunhes (M-B) transition, as preserved in a continuous sequence of exposed lacustrine sediments in the Apennines of Central Italy. The palaeomagnetic record provides the most direct evidence for the tempo of transitional field behaviour yet obtained f...