University of Colorado, Denver, United States
September 6, 2022
How do we practice, develop and support graduate field leadership skills?
Completing a field season successful and safely can be a critical element of completing a graduate degree for many scientists in the natural sciences. Few graduate programs, however, provide explicit training or support for developing the myriad of skills that may be required to lead a field season. We surveyed the natural sciences community, asking some of the following questions: what are “good” field leadership skills? How can we incentivize and support developing strong field leadership skills in graduate students? This talk explores the survey results, and provides suggestions for current graduate students, faculties, programs and scientific societies.
Jagiellonian University, Poland
September 13, 2022
Burrows and footprints in post-glacial dune sands: a window onto faunal and environmental change in Holocene Europe
Burrows, tracks, and other life traces in the sedimentary record may be easily overlooked, but often provide some of the only evidence of the presence and activities of animals which inhabited or passed through an area. Excavation of Holocene dune deposits, particularly in the eastern part of the European Sand Belt, reveal a variety of examples, including buried terrestrial invertebrate burrows, mammal hoof prints and human footprints. They provide intriguing clues as to how the fauna and landscape of the region was shaped by both natural and anthropogenic forces over the past several millennia.
Aarhus University, Denmark
September 27, 2022
Orbital forcing of African climate across time and space
The African environment has fluctuated throughout the Cenozoic, drastically altering the landscape where our early human ancestors lived, moved, and evolved. Climate oscillations may be a key to the evolutionary response to ecosystem change, and it is clear that cycles in the Earth’s orbit are a significant driver of these changes. However, due to the lack of long, highly-resolved, records of terrestrial paleoclimate, there are remaining questions pertaining to the dominant drivers of climate variability, how these cycles changed through shifts in global boundary conditions, and the differing responses to orbital cycles across the continent. Here, I present a compilation of orbitally-resolved leaf wax biomarker records from various lacustrine and marine archives to piece together the history of climate variability in Africa.
Texas A&M University, USA
October 11, 2022
Untapped potential of archaeal lipids beyond ocean temperature reconstructions
Marine ammonia-oxidizing archaea (AOA) are chief autotrophic ammonia oxidizers in marine settings, playing an important role in marine nitrogen and carbon cycling. Glycerol dialkyl glycerol tetraethers (GDGTs) are archaeal membrane lipids that are ubiquitous in marine sediments and can be preserved for hundreds of millions of years. These lipids are commonly used as a proxy for past ocean temperatures but rarely used to study paleoecology and the evolution of marine AOA themselves. Here, I present our recently published work in which two distinct distributions of GDGTs—‘thermal’ vs. ‘nonthermal’ behaviors—were identified from modern-day archives. We then utilized unsupervised clustering models to extract these diagnostic patterns of modern AOA ecology from ancient marine records. The new perspective from our work carries important implications for marine nitrogen and carbon cycles in past oceans and the reconstruction of GDGT-based ocean temperatures.
George Washington University, USA
October 18, 2022
Vegetation structure in modern African ecosystems : Implications for hominin paleoenvironmental reconstruction
Environmental change is considered a key driver of human evolution and several hypotheses have been proposed to explain the outcomes of proposed environmental changes. One approach to testing these hypotheses is reconstructing the paleoenvironment of hominin bearing sites and looking for evidence of temporal change across sites. However, most paleoenvironmental reconstructions from hominin fossil bearing sites indicate a “mosaic habitat” which simply means a mix of habitat types. Thus, to better under the paleoenvironmental context of hominin evolution and make more refined habitat reconstructions, my research is focused on studying modern African ecosystems and applying the knowledge garnered to the fossil record. In this talk, I present my work on woody cover in modern African ecosystems using stable carbon isotope data from surface soils, and herbivore diet and relative abundance. Then, I will discuss my research on the diet of fossil herbivores and paleosols from the Shungura Formation, a hominin fossil site in eastern Africa.
Naima El bani Altuna
UiT – The Arctic University of Norway, Norway
October 25, 2022
Sea ice-ocean coupling during Heinrich Stadials in the Nordic Seas
Arctic warming in the same rates as present-day climate change have occurred during abrupt climate oscillations during the last glacial period, when the climate oscillated in a few decades from cold long-lasting stadials to warm and shorter interstadials. Even though Arctic sea-ice variability is known to be a key element in amplifying the effect of such an abrupt atmospheric warming, it is still poorly understood what drives changes in the sea-ice cover. Sea ice works as a lid insulating the ocean from the atmosphere, and vice versa, and it is therefore sensitive to changes both from the atmosphere and from the ocean. Here, we reconstructed and investigated the relationship between bottom water temperature (BWT) measured on benthic foraminifera tests and sea-ice biomarker data (IP25, HBI III and calculated sea-ice indicators) at millennial-timescales during Marine Isotope Stages 3 and 2 in core HH15-1252PC, retrieved from a water depth of 1,273 west of Svalbard in the northern Nordic Seas. Our findings reveal two distinct scenarios with generally open-ocean conditions during warm interstadials and extensive sea-ice cover during cold stadials. The comparison between sea-ice biomarkers and BWT during Heinrich Stadials shows a tight linkage between both variables, with rapid reductions in spring sea-ice coincident with drops of BWT. This study thus provides new insights into the close coupling between BWT and sea-ice cover in the Nordic Seas at millennial-timescales.
University of New South Wales, Australia
November 01, 2022
Early Earth biosignatures and the search for life on Mars
NASA’s current Mars rover, Perseverance, is exploring Jezero Crater, which is
more than 3.5 billion years old. Research from Early Earth, and other palaeoenvironmental
analogues, help inform the search for life on Mars. Biosignatures are means by which we
search for signs of extant and/or fossilised ancient life and are broadly defined as an object,
substance, and/or pattern whose origin specifically requires a biological agent. In this talk, I
will discuss how organic biosignatures can help us increase reliability when detecting
possible signs of life. I will focus on chemical fossils in rocks from the 3.5 Ga Dresser
formation, from the Pilbara Craton, Western Australia, as well as analogues from the
younger geological record. The Dresser Formation holds some of the oldest, most
convincing evidence for life on Earth. I will also showcase education and outreach in the
area, both in terms of in-person field trips, and in immersive virtual field experiences. This
presentation will underscore the importance of a thorough contextual understanding of life
in interpreting biosignatures on ancient Earth and possibly other planetary bodies.
University of Virginia, USA
November 08, 2022
Differential impacts of subglacial bed conditions on paleo-ice flow and subglacial processes
Glacier flow across landscapes is impacted by subglacial conditions, such as the presence of meltwater, variable topography, and differences in bed lithology. Streamlined subglacial bedforms are oriented in the direction of ice flow, having formed at the base of warm glaciers, and provide the opportunity to assess glacier sensitivity to subglacial conditions across broad spatiotemporal scales. Here, I present statistical and spatial analyses of several thousand subglacial bedforms across the deglaciated northern hemisphere. Changes to streamlined bedform morphologies are used to determine systematic controls on ice-bed interactions and processes across landscapes with variable topographic and lithologic settings. Findings presented in this work provide analogues for warm-based ice flow of contemporary glacial systems — settings where we know little about the active conditions and processes due to the difficult-to-reach location of the subglacial environment.
University of Southampton, UK
November 22, 2022
Developmental plasticity in the fossil record: a case study of planktonic foraminifera
Developmental plasticity, the process where a single genotype can produce multiple phenotypes depending on the environment, increases phenotypic variation available for selection. However, its effects on long-term evolution are poorly understood because most fossils don’t preserve their developmental stages. Foraminifera are an exception: they preserve their entire ontogeny, and their shell chemistry reflects the environment they grew in. Using ecological models, three-dimensional growth parameters and environmental reconstructions, we show that both internal constraints and environmental fluctuations influence shell size and shape in three closely related species. All species respond differently, suggesting that the speciation process overrides internal constraints.
Pontifical Catholic University of Chile
November 29, 2022
Late Quaternary extinction in South America: different approaches, one quest
By the end of the Pleistocene the world lost a great number of large terrestrial mammal species in what is known as the Late Quaternary Extinction event (LQE). South America was one of the most affected continents losing over an 80% of terrestrial mammal species weighing over 44 kg. The discussion about the causes of extinction remains open, with anthropogenic impacts and climate changes as possible drivers in the center of the debate. Here I’ll present how we have worked and are working to elucidate some aspects of the LQE in South America.