University of Victoria, Canada
November 30, 2021
Towards a more holistic understanding of microfossil records and evolution.
In this talk I will attempt to discuss both the evolutionary record of microfossils and their impact on the marine sedimentary record. For a long time, micropaleontological study was silo’d into individual groups; foram workers study forams, radiolarian workers study radiolarians. I will discuss recent efforts to analyze these groups together, showing findings from examining a series of Plio-Pleistocene records of foram size and carbonate mass accumulation, and another study using PyRate to look at the macroevolutionary rates of all four of the main groups (diatoms, radiolarians, calcareous nannofossils, and planktic foraminifera). Lastly, I’ll discuss a current effort working to take data from the IODP sources and move it into two existing databases (Macrostrat and the Paleobiology Database), and our hopes to extend this line of research.
University of St Andrews, UK
November 23, 2021
Constraining the role of the Southern Ocean in glacial CO2 drawdown
Atmospheric CO2 has varied in pace with glacial-interglacial cycles over the past 800,000 years, largely due to shifts in carbon partitioning between the deep ocean and the atmosphere. The Southern Ocean is thought to play an important role in these changes, as it is a region of intense upwelling and ventilation of carbon-rich deep waters today; however, the exact mechanism by which it influenced CO2 during glacial periods is unclear. Here I will present reconstructions of pH in the Antarctic Zone of the Southern Ocean over the last glacial cycle which show an increase in sea-surface pH (reduction in CO2) at glacial inception. These data suggest that a shift in regional circulation patterns reduced the ventilation of carbon-rich deep waters, contributing to the transition to a glacial state.
Penn State University, USA
November 16, 2021
Tracking Anoxia in Ancient Oceans: Insights from uranium isotopes
The redox state of the oceans strongly influences organic carbon burial, habitability for marine biota, and biogeochemical cycling of nutrients and critical redox-sensitive elements.
There are various methods for reconstructing oxygenation and deoxygenation through Earth history: Of these, inorganic geochemical proxies offer the potential to track redox conditions across a range of temporal and spatial scales. In particular, uranium isotopes ( 238 U/ 235 U) have emerged as a useful tool for reconstructing the redox conditions of the Earth’s oceans. Variations in 238 U/ 235 U, particularly when recorded in carbonate sediments, can track global trends in marine
oxygenation and de-oxygenation. Rapid development continues to refine the accuracy of interpretations of 238 U/ 235 U records. In this talk, I will discuss two case studies: one of how U
isotopes can help eluciate the end-Permian mass extinction and another of how diagenetic modeling can help advance interpretations of these records.
Hebrew University of Jerusalem, Israel
November 9, 2021
@ 1600 UTC
Development of new foraminiferal proxies for paleochemistry of the oceans
Trace elements are incorporated into the CaCO 3 shells of foraminifera and are widely used as paleo-environmental proxies. These elements are measured as El/Ca ratio in the shell, and are dependent on their respective El/Ca ratios in seawater (and also on temperature, carbonate chemistry etc.). However, seawater Ca concentration (Ca sw ) has
a short resident time (~1 Myr) and its concentration in the ocean varied significantly during the Phanerozoic. Since Na sw has a long residence time (55-260 Myr), foraminiferal Na/Ca can be used as a proxy for past Ca sw concentrations throughout the Cenozoic. To evaluate this working hypothesis, we performed a series of laboratory culture experiments on the large benthic foraminifer Operculina ammonoides, an extant relative of the Eocene Nummulites. Furthermore, the paleo-concentrations of other major and minor elements may then be calculated relative to the Ca in the shells.
James Cook University, Australia
November 2, 2021
@ 2100 UTC
Burning questions: exploring human-environment interactions in late Holocene savanna fires in northern Australia
How do we find signs of Indigenous cultural burning in palaeofire records, especially in fire-prone
ecosystems like savannas? The answer may be a combination of methods we already have. This
seminar presents a multi-proxy 4600-year palaeofire record from a previously unstudied region of
northern Australia, looking at relative fire intensity paired with other measures to find human
Iowa State University
October 26, 2021
Carbon-Sulfur Coupling and Temporal Frequencies of Hydrocarbon Seeps in the Gulf of Mexico: Insights
from Authigenic Carbonate Geochemistry
Continental margins of the Gulf of Mexico (GoM) are often characterized by sites with natural seepage of
methane and other hydrocarbons from subsurface reservoirs towards the seafloor. These seepage sites
have a significant impact on the geology and biology of seabed facilitated through complex, microbially
mediated biogeochemical processes. Modern hydrocarbon seepage sites will allow us to examine the
seepage induced biogeochemical signatures imprinted onto the sedimentary record and thereby sedimentary-proxy development to recognize past seep records as well as the broader biogeochemical implication of these geosphere-biosphere interactions.
This talk will present results from investigation on carbon-sulfur (C-S) coupling and temporal frequency of hydrocarbon seeps in the GoM using the stable carbon isotopes (δ 13 C carbonate ), sulfur isotopes (δ 34 S sulfide
minerals ), and radioactive U-Th dates obtained from authigenic carbonate rocks formed at seep sites. Key
results suggested that (i) asphalt seepage has been ongoing for thousands of years in the southern GoM, at
least since 13.5 ka, and (ii) Sulfate-driven anaerobic oxidation of methane and crude oil produces distinguishable δ 13 C DIC and δ 34 S sulfide signatures. The latter observation further enabled developing a novel template based on δ 13 C CaCO3 vs. δ 34 S CRS cross plot to distinguish oil and methane seeps from sediment
Friedrich Alexander Universität Erlangen-Nürnberg
October 19, 2021
Big equipment, tiny structures: A multi-analytical approach to unravelling the conodont conundrum.
The increasing ease of access and technological advances of equipment such as scanning electron microscopes (SEM), synchrotron light sources and micro CTs have revolutionised microanalysis in several fields. Techniques like Secondary Electron Microscopy (SE), Energy-Dispersive X-ray Spectroscopy (EDX/EDS) and Electron Backscatter Diffraction (EBSD) are utilised to help decipher physical and chemical properties of fossils on a micro scale. Applying these methods to fossil material can unlock secretes regarding an organism’s function and ecology. Conodonts are microscopic teeth from eel-like vertebrates that are abundant from the Cambrian to Triassic and are constantly utilised in the fields of biostratigraphy and geochemistry, but their ecology remains poorly understood. Here we highlight how the utilisation of a multi-analytical approach can make observations on chemical composition and structure, which have helped address several enigmas revolving around the ecology, function, biomineralisation of these tiny teeth.
Hassan II University of Casablanca, Morocco
October 12, 2021
Tracking climate variability and environment changes of carbonate mounds sediments in the western Mediterranean over the last 14,000 years
The palynology based on dinoflagellate cysts has been widely applied to the upper Pleistocene-Holocene Mediterranean sediments. However, no palynological studies on the sediments associated with the cold-water coral carbonate mounds observed in the western Mediterranean have been undertaken. The analysis of the microfossils (dinoflagellate cysts and pollen) in marine sediments, taken from the Moroccan margin of the Alboran Sea during the MD194 “Gateway” Eurofleets oceanographic expedition in 2013, is the topic of this research. The dinoflagellate cyst assemblages provide a credible record of paleoenvironmental and paleoclimatic development over the interval: Bölling/Alleröd – upper Holocene with a clear dominance over the continental fraction, which despite their low representativity, is proving to be a valuable tool for the paleoclimate interpretation.
Liverpool John Moore’s University, UK
October 5, 2021
A Deep Dive into Dinosaur Heteropody
Why are the forefeet and hindfeet of some quadrupedal dinosaurs such starkly different sizes and shapes? This phenomenon, known as extreme heteropody, is explored in the contexts of centre of mass position, underfoot pressure, trackway preservation, and the unique evolutionary history of these animals from bipedal ancestors to quadrupedal giants. Is there a biomechanical explanation for this phenomenon or do the answers lie elsewhere?
Brooklyn College (CUNY)
September 28, 2021
Doing Justice to the Incredible Biodiversity of Ammonites: Mathematical and Visual Perspectives.
In both scientific literature and paleoart, ammonites have been depicted as deceptively uniform for decades, if not longer. Primitive planispirals and outlandish heteromorphs are reconstructed to behave much the same as one another, and worse, very different genera are often labeled with the
indiscriminate moniker “ammonite”. Modern cephalopods have similar hard parts but wildly diverse soft-tissue morphologies, behaviors, and environments—with such variation in shells, paleoenvironments, and buccal remains, why do we treat ammonites as all looking and behaving the
same? Using modern discoveries for soft-tissue anatomy, stable-isotope ratios, and buccal masses of
different types of ammonites, it is possible for paleoartists to extrapolate how specific ammonites may have lived and appeared—as well as just how diverse they truly were. Another new line of defense against the outdated, monochrome view of ammonites is in their sutures, which are strikingly different from each other and certainly evolved from a wide variety of different pressures (though their exact function is still the subject of debate). Sutures can be examined as fractal objects, and a newly discovered tendency of all ammonite sutures occurring in just one portion of them—the lateral lobe and next saddle, or LLS—allows for larger sample sizes, but may also open the door to previously unanswered questions about ontogeny. Finally, we use LLS to once again the ages-old question of whether suture geometry is a reliable indicator of needed taxonomic revision.
University of Vermont
September 21, 2021
The Story of Camp Century: the Fossil Ecosystem Under Ice
Understanding the past behavior of the Greenland Ice Sheet is critical for predicting its response to future climate warming and contribution to sea-level rise. Our team has analyzed sediment at the bottom of the Camp Century ice core, collected in northwestern Greenland in the early 1960s. The sediment, frozen under nearly 1.4 km of ice, contains well-preserved fossil plants and leaf waxes from tundra ecosystems that emerged during at least two ice-free warm periods in the past few million years. I will discuss the multiple lines of evidence this sediment contains for the existence and timing of past ice-free events in northwestern Greenland and the implications for past contributions to sea level from the Greenland Ice Sheet.
James Madison University
September 14, 2021
New Insights into Nascent C4-Grass Habitats from the Early Miocene of Eastern Africa
Modern tropical grasslands and savannas are dominated by vegetation that uses the Hatch-Slack (C4) photosynthetic pathway, which has advantages over Calvin Cycle (C3) photosynthesis in a variety of environmental and climatic situations. The proliferation of C4 plants was globally diachronous throughout the Neogene and likely involved unique combinations of biotic and abiotic forcings on regional scales within a backdrop of declining atmospheric CO2. In this talk, new discoveries of early Miocene (17-16 Ma) C4 biomes from eastern Africa will be discussed, with focus on landscape processes and paleoclimate conditions. This work has revealed two surprising findings: 1) early hominoid communities existed across a wide variety of climate and vegetation space, and 2) C4 plants were locally abundant 6-10 million years prior to their late Miocene proliferation on the African continent.
University of West Indies
September 7, 2021
The biogeography of “breas”: contextualizing the taphonomy, ecology, and diversity of Trinidad’s asphaltic fossil record
Fossiliferous asphaltic sites are rare with the exception of the findings from Rancho La Brea site of California, USA. In the neotropics, such deposits represent opportunities for preservation in otherwise challenging tropical climates. The Caribbean island of Trinidad contains the second largest natural asphalt deposit in the world and has a fragmentary record of brief excavations in the early-mid 1900s which coincided with crude oil exploration. We integrated information from multiple collections databases with archival research and compiled the first comprehensive Pleistocene faunal record for terrestrial Trinidad. Mammalian orders included Cingulata, Pilosa, Proboscidea and Rodentia, with genera that are ecologically consistent with the former savanna connection of Trinidad and Venezuela. Using this information, we infer the Quaternary biogeographic and paleoenvironmental history of Trinidad. Our study contributes both to our understanding of the paleoecology of the Caribbean and northern South America, as well as “tar pits” globally.