Bradley D. Cramer
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View article: Teaching Aquitard Concepts With Field‐Based High‐Resolution Head Profile Learning Activities
Teaching Aquitard Concepts With Field‐Based High‐Resolution Head Profile Learning Activities Open
Aquitards play critical roles in a variety of hydrogeologic processes. Despite their importance, coverage of aquitards in introductory hydrogeology textbooks is generally limited. This paper provides examples of classroom and field activit…
View article: Semi-automated correlation of Silurian well-logs across Gotland, Sweden, using Dynamic Time Warping with Barycenter Averaging
Semi-automated correlation of Silurian well-logs across Gotland, Sweden, using Dynamic Time Warping with Barycenter Averaging Open
Studies of the Silurian sequence on Gotland have significantly advanced our understanding of Silurian climate dynamics, with much of the research focusing on small outcrops and short cores. Gotland has an extensive network of abandoned oil…
View article: Defining the Sheldon Creek Formation, a Middle Wisconsinan (MIS 3) till in Iowa, USA
Defining the Sheldon Creek Formation, a Middle Wisconsinan (MIS 3) till in Iowa, USA Open
A pre‐Late Wisconsinan, post‐Illinoian, till sheet has long been recognized in north‐central Iowa, but has not been formally recognized or defined until now. Early researchers referred to these deposits as the ‘Tazewell’, and the term ‘She…
View article: Expansion of Reducing Marine Environments During the Ireviken Biogeochemical Event: Evidence From the Altajme Core, Gotland, Sweden
Expansion of Reducing Marine Environments During the Ireviken Biogeochemical Event: Evidence From the Altajme Core, Gotland, Sweden Open
New δ 34 S py (pyrite) and δ 34 S CAS (carbonate‐associated sulfate) across the Llandovery‐Wenlock boundary (∼432 Ma) provide evidence for the expansion of reduced marine environments during the Ireviken Biogeochemical Event. This event co…
View article: Evolution of Atmospheric O2 Through the Phanerozoic, Revisited
Evolution of Atmospheric O2 Through the Phanerozoic, Revisited Open
An oxygen-rich atmosphere is essential for complex animals. The early Earth had an anoxic atmosphere, and understanding the rise and maintenance of high O2 levels is critical for investigating what drove our own evolution and for assessing…
View article: Chronostratigraphic correlation of the Upper Silurian Salina Group for the Michigan and Appalachian Basins through coupled (δ13Ccarb) chemostratigraphy and subsurface geophysical analyses
Chronostratigraphic correlation of the Upper Silurian Salina Group for the Michigan and Appalachian Basins through coupled (δ13Ccarb) chemostratigraphy and subsurface geophysical analyses Open
The Upper Silurian Salina Group of eastern North America is well known for its thick evaporite successions and hydrocarbon resources. These strata have been assigned to numerous chronostratigraphic schemes within Ohio and Michigan and are …
View article: Nanomechanical variability in the early evolution of vertebrate dentition
Nanomechanical variability in the early evolution of vertebrate dentition Open
View article: A sequence of temporally separated element peaks; the fingerprint of a biogeochemical event initiated by sedimentary exhalative (SEDEX) brine expulsion
A sequence of temporally separated element peaks; the fingerprint of a biogeochemical event initiated by sedimentary exhalative (SEDEX) brine expulsion Open
<p>The Ireviken Biogeochemical Event (IBE) consists of the Ireviken Extinction Event (IEE) and is superseded by the Ireviken positive d13Ccarb Excursion (ICIE). During the Ireviken Extinction Event 80% of the conodont species and 50%…
View article: An expanded stratigraphic record of the Devonian-Carboniferous boundary Hangenberg biogeochemical Event from Southeast Iowa (U.S.A.)
An expanded stratigraphic record of the Devonian-Carboniferous boundary Hangenberg biogeochemical Event from Southeast Iowa (U.S.A.) Open
The Devonian-Carboniferous boundary in the type area of the Mississippian subsystem (tri-state area of Iowa, Illinois, and Missouri) has been historically difficult to identify. Many of the localities contain similar lithologies and strati…
View article: Decoupling δ13Ccarb and δ13Corg at the onset of the Ireviken Carbon Isotope Excursion: Δ13C and organic carbon burial (forg) during a Silurian oceanic anoxic event
Decoupling δ13Ccarb and δ13Corg at the onset of the Ireviken Carbon Isotope Excursion: Δ13C and organic carbon burial (forg) during a Silurian oceanic anoxic event Open
Paired records of δ13Ccarb and δ13Corg across the Llandovery-Wenlock boundary demonstrate asynchronous behavior during the onset of the Ireviken Biogeochemical Event (IBE). The extremely high-resolution data produced from the Altajme Core,…
View article: GSA Statement on Diversity and a Challenge to the Society, Geoscience Departments, and the Geoscience Community at Large
GSA Statement on Diversity and a Challenge to the Society, Geoscience Departments, and the Geoscience Community at Large Open
View article: Ontogenetic variability in crystallography and mosaicity of conodont apatite: implications for microstructure, palaeothermometry and geochemistry
Ontogenetic variability in crystallography and mosaicity of conodont apatite: implications for microstructure, palaeothermometry and geochemistry Open
X-ray diffraction data from Silurian conodonts belonging to various developmental stages of the species Dapsilodus obliquicostatus demonstrate changes in crystallography and degree of nanocrystallite ordering (mosaicity) in both lamellar c…
View article: Silurian conodont biostratigraphy of the east-central Appalachian Basin (eastern USA): Re-examination of the C.T. Helfrich Collection
Silurian conodont biostratigraphy of the east-central Appalachian Basin (eastern USA): Re-examination of the C.T. Helfrich Collection Open
The conodont biozonation for the Silurian succession in the Appalachian Basin was established by C.T. Helfrich nearly half a century ago.Herein, we reexamined and updated the taxonomy of the conodont fauna and the consequent biozonation of…
View article: Cyclo and chemostratigraphic characteristics of the Middle Silurian in Gotland, Sweden
Cyclo and chemostratigraphic characteristics of the Middle Silurian in Gotland, Sweden Open
<p>The cumulative work of geoscientists over the past decades has shown that the Silurian Period which was once thought as warm and climatically stable time interval is in fact punctuated by numerous paleoenvironmental perturbations …
View article: High-resolution event stratigraphy (HiRES) of the Silurian across the Cincinnati Arch (USA) through integrating conodont and carbon isotope biochemostratigraphy, with gamma-ray and sequence stratigraphy
High-resolution event stratigraphy (HiRES) of the Silurian across the Cincinnati Arch (USA) through integrating conodont and carbon isotope biochemostratigraphy, with gamma-ray and sequence stratigraphy Open
Silurian strata within the tristate area of Indiana, Ohio, and Kentucky have been thoroughly studied for well over a century. Due to rapid facies changes throughout the region numerous lithostratigraphic terminologies were established, man…
View article: Identification of a global sequence boundary within the upper Homerian (Silurian) Mulde Event: High-resolution chronostratigraphic correlation of the midcontinent United States with Sweden and the United Kingdom
Identification of a global sequence boundary within the upper Homerian (Silurian) Mulde Event: High-resolution chronostratigraphic correlation of the midcontinent United States with Sweden and the United Kingdom Open
The upper Homerian Mulde Event was an extinction event that devastated graptolite diversity and occurred before and during the onset of a major perturbation to the global carbon cycle, which is recorded as a double-peaked positive carbon i…
View article: Phanerozoic<i>p</i>O<sub>2</sub>and the early evolution of terrestrial animals
Phanerozoic<i>p</i>O<sub>2</sub>and the early evolution of terrestrial animals Open
Concurrent gaps in the Late Devonian/Mississippian fossil records of insects and tetrapods (i.e. Romer's Gap) have been attributed to physiological suppression by low atmospheric p O 2 . Here, updated stable isotope inputs inform a reconst…
View article: Supplementary material from "Phanerozoic <i>p</i>O<sub>2</sub> and the early evolution of terrestrial animals"
Supplementary material from "Phanerozoic <i>p</i>O<sub>2</sub> and the early evolution of terrestrial animals" Open
Concurrent gaps in the Late Devonian/Mississippian fossil records of insects and tetrapods (i.e. Romer's Gap) have been attributed to physiological suppression by low atmospheric pO2. Here, updated stable isotope inputs i…
View article: Supplementary Data from Phanerozoic <i>p</i>O<sub>2</sub> and the early evolution of terrestrial animals
Supplementary Data from Phanerozoic <i>p</i>O<sub>2</sub> and the early evolution of terrestrial animals Open
Concurrent gaps in the Late Devonian/Mississippian fossil records of insects and tetrapods (i.e. Romer's Gap) have been attributed to physiological suppression by low atmospheric pO2. Here, updated stable isotope inputs i…
View article: Global chronostratigraphic correlation of the Llandovery Series (Silurian System) in Iowa, USA, using high-resolution carbon isotope (&delta;13Ccarb) chemostratigraphy and brachiopod and conodont biostratigraphy
Global chronostratigraphic correlation of the Llandovery Series (Silurian System) in Iowa, USA, using high-resolution carbon isotope (δ13Ccarb) chemostratigraphy and brachiopod and conodont biostratigraphy Open
Chronostratigraphic correlation of Silurian units in Iowa is complicated by complex carbonate depositional environments and poor biostratigraphic control.Carbon isotope (δ 13 C carb ) chemostratigraphy, when integrated with the relatively …
View article: Telychian (Llandovery, Silurian) conodonts from the LaPorte City Formation of eastern Iowa, USA (East-Central Iowa Basin) and their implications for global Telychian conodont biostratigraphic correlation
Telychian (Llandovery, Silurian) conodonts from the LaPorte City Formation of eastern Iowa, USA (East-Central Iowa Basin) and their implications for global Telychian conodont biostratigraphic correlation Open
Waid, Christopher B.T., Cramer, Bradley D. (2017): Telychian (Llandovery, Silurian) conodonts from the LaPorte City Formation of eastern Iowa, USA (East-Central Iowa Basin) and their implications for global Telychian conodont biostratigrap…
View article: Sequence boundaries and chronostratigraphic gaps in the Llandovery of Ohio and Kentucky: The record of early Silurian paleoceanographic events in east-central North America
Sequence boundaries and chronostratigraphic gaps in the Llandovery of Ohio and Kentucky: The record of early Silurian paleoceanographic events in east-central North America Open
New and published data are integrated herein to resolve the age and stratigraphic relationships for problematic strata of the Aeronian and Telychian (Llandovery; Silurian) in Ohio and Kentucky (USA). At least two major depositional sequenc…
View article: High-precision U–Pb zircon age constraints on the duration of rapid biogeochemical events during the Ludlow Epoch (Silurian Period)
High-precision U–Pb zircon age constraints on the duration of rapid biogeochemical events during the Ludlow Epoch (Silurian Period) Open
Precise determinations of the rates and durations of Palaeozoic biogeochemical events are largely unavailable. Here, we present two new high-precision U–Pb (zircon) dates from volcanic ash deposits from the Ludlow Series (Silurian System) …