University of Birmingham
August 31, 2021
Volcanism, weathering, and the changing carbon cycle – Linking C, Sr, Li, Os and Ca isotope dynamics in an Earth system model
Weathering, erosion and volcanism shape the long-term evolution of climate and biogeochemical cycling at Earth’s surface and changes in these processes thus need to be considered when reconstructing past Earth system states and long-term climatic changes. Yet, they are difficult to reconstruct based on traditional stable isotope systems, and are instead reconstructed using the isotope systems of metals such as strontium (Sr), lithium (Li), osmium (Os) and calcium (Ca). Commonly, isotopic shifts of these four elements in the geologic record are interpreted with isotope-mixing, tracer-specific box models because of their long residence times in the ocean. However, these models often lack mechanistic links between the cycling of the four metals and other geochemically relevant elements, particularly carbon, which complicates the reconstruction of internally-consistent Earth system states. Here, I present our new implementation of Sr, Li, Os and Ca isotope cycling into the Earth system model cGENIE. The model offers the possibility to study these metal systems at equilibrium and under perturbations alongside other biogeochemical cycles and therefore provides a novel tool to understand environmental change in the context of changing geologic processes. Through example simulations I will demonstrate how this new tool can be applied to investigate Sr, Li, Os and Ca isotope dynamics in different Earth system configurations and during environmental change.
University Dar es Salaam, Tanzania
August 24, 2021
Hominin Plant landscapes at Oldupai Gorge, Tanzania (2-1.1Ma)
Hominin adaptations to changing environments and increasing aridity in East Africa are central to current palaeoanthropological debate, particularly regarding the Oldowan- Acheulian transition. Reconstructions of past vegetation landscapes require a multi-disciplinary approach
that includes paleoethnobotany, archaeology, and geoarchaeology to illustrate long term
environmental trends observed in sedimentary sequences. Olduvai Gorge (Tanzania) contains bedded deposits of recognized value to address questions such as the habitat types that existed during 2.0 Ma, and along palaeo-lake Oldupai during the deposition of upper Bed II (1.5-1.1
Ma). This talk will focus on the key aspects related to hominin plant landscapes during Bed I and Bed II times in relation to available niches that attracted hominin occupations to these localities.
Centro para la Integración en Paleobiología, Universidad Autónoma de Madrid (CIPb-UAM)
August 17, 2021
Quantitative Paleobotany: keys to the study of the vegetation of the past
The study of plant fossils must deal with a series of problems related to the loss of information during fossil production, transport, and fossilization. Most of the plants found in the fossil record are fragmented, and therefore whole plant reconstructions are complicated. Also, remains that have been transported can induce to error in the interpretation of the original vegetation. When plant organs are abscised, the rest of the plant continues to live, and therefore the calculation of the number of individual plants is problematic if the longevity of their leaves and their seasonal cycle are unknown. Quantitative methods used to analyze fossil ferns from four exceptional Lower Cretaceous localities from Europe have proven to aid in the comprehension of fossil plants and their autecology, giving us a few “brush-strokes” of the landscape of the past.
August 10, 2021
Reorganizations of Pliocene hydroclimate inferred from organic geochemical proxies
Geologic evidence suggests drastic reorganizations of subtropical terrestrial hydroclimate during past warm intervals, including the mid-Piacenzian Warm Period (MP, 3.3 to 3.0 Ma). Despite having a similar to present-day level of atmospheric CO2, existing geologic evidence suggests that the MP featured much wetter conditions on subtropical continents. Here, I present evidence from models and proxies that explore the causes of MP terrestrial hydroclimate. In particular, I present new hydrogen isotopic analysis of leaf waxes that shed light on hydroclimate changes in western North America, where waxes reflect changes in the character and seasonality of past rainfall. Comparison of these results to a hierarchy of model simulations reveals new perspectives on the potential drivers of subtropical hydroclimate change in the Pliocene.
Information Sciences Institute
University of Southern California
August 03, 2021
AI in the paleogeosciences: progress, challenges, and opportunities
“The past is the key to the future.” In a seminal paper from the 1980’s, Bruce Doe recognized the importance of the then emergent field of paleoclimatology to decisions federal agencies would have to make in the face of rising greenhouse gases concentrations. The promise of paleoclimatology is two-folds: (1) to assess the current climate change in the context of climate variations across the decades and centuries, and (2) to validate climate
model outputs. But it wasn’t until recently, with advances in geoinformatics, that paleoclimatology could fully fulfill its promises.
In this talk, I will walk through examples of how advances in artificial intelligence have benefited the paleogeosciences, and in particular paleoclimatology. I will demonstrate how knowledge representation and has helped with the day-to-day work of paleoclimatologists by
broadening access to data and to automated cutting-edge data analytic tools.
July 27, 2021
Fossil preservation in the Fezouata Shale with implications in understanding the early stages of the Ordovician Radiation
The Fezouata Shale (Early Ordovician, Morocco) is a unique site that preserved a diverse assemblage of soft parts at the transition between the Cambrian Explosion and the Ordovician Radiation. Herein, classical sedimentological approaches and a large spectrum of microanalyses techniques are applied to investigate the preservation of this assemblage. Fossils from the Fezouata Shale share the same mode of preservation with Cambrian Burgess Shale-type sites defined by carbonaceous compressions and accessory authigenic mineralization. However, the mechanism of preservation (e.g., flow dynamics) is different. Using probabilistic approaches, it is shown that the mechanism for soft part preservation in the Fezouata Shale under-preserved fully cellular taxa such as jellyfishes while preserving equally different modes of life (i.e., endobenthic, epibenthic/nektobenthic, and planktonic/nektonic). This is not observed within the Walcott Quarry (Cambrian, Canada), one of the most famous fossil sites, in which the mechanism for exceptional preservation allowed for the conservation of entirely cellular taxa while underestimating the nekton. Accounting for these preservational biases made it possible to investigate community assembly within the Fezouata Shale and draw conclusions highlighting the complex initial stages of the Ordovician Radiation.
July 20, 2021
Reconstructing paleo-Oxygen Minimum Zones from the shells of low-oxygen tolerant planktic foraminifera
The presence and extent of low-oxygen waters helps regulate global climate and marine nutrient cycles and can define habitats. Observations over the past decades suggest that low-oxygen regions, including mid-depth Oxygen Minimum Zones (OMZ), are expanding in response to our changing climate. However, understanding the long-term trajectory and future of OMZ environments has been limited by fairly sparse reconstructions of their geologic past. Expanding the role of planktic foraminifera as proxies for these pelagic environments has the potential to change this. I will present results from recent work with living and fossil planktic foraminifera to (1) demonstrate the presence of planktic foraminifera in the modern OMZ, and (2) apply findings from modern OMZ-affiliated foraminifera (shell morphology and stable isotope) to the question of vertical positioning of the glacial-Holocene OMZ in the Eastern Equatorial Pacific. The resulting record supports the deglacial expansion of the Eastern Equatorial Pacific OMZ, and a restructuring of mid-water oxygenation and carbon content from the glacial to the Holocene.
Smithsonian Tropical Research Institute
July 13, 2021
The end-Cretaceous extinction and the early evolution of Neotropical rainforests
The ecological catastrophe at the end-Cretaceous had devastating effects on terrestrial ecosystems worldwide. Plant fossils indicate varying rates of extinction and recovery from across the globe, nonetheless, biases in the plant fossil record from tropical latitudes have limited our understanding of the long-lasting effects of the end-Cretaceous on tropical forest communities.
In this talk, I will present analyses of >50,000 pollen occurrences and >6000 fossil leaves from localities in Colombia that document plant extinction and recovery of tropical forests resulting from the end-Cretaceous event. Plant diversity declined by 45% at the Cretaceous-Paleocene boundary and did not recover for ~ 6 million years. Pre-extinction rainforests were a mix of ferns, flowering plants and conifers that grew forming open canopies, and sheltered diverse plant-insect interactions. After the extinction, these communities became replaced with Paleocene rainforests that closely resembled modern Neotropical rainforests in plant composition and in having a closed, multistratal canopy structure dominated by flowering plants. These results show that the end-Cretaceous event triggered an anomalously long interval of low plant diversity in the tropics and led to the assembly of today’s most diverse terrestrial ecosystem.
University of Texas
July 6, 2021
Swift and sustained silicate weathering response in floodplains during the Paleocene-Eocene
Thermal Maximum: Insights from the Bighorn Basin, Wyoming, USA
During the Paleocene-Eocene Thermal Maximum (PETM), rates of silicate weathering are thought to increase and offset the rapid and massive input of CO2 into the atmosphere and ocean.
However, limited quantitative evidence exists of the silicate weathering response on continents to the PETM. Here we show that silicate weathering intensity in the Bighorn Basin, Wyoming (USA) increased
during the PETM and remained high during at least the initial stage of recovery, even as atmospheric pCO2 decreased. Through analyzing the Li isotope composition of overbank sedimentary deposits and
basin-bounding source rocks, we find that soils that formed farthest from ancient river channels are more sensitive to changes in climate than near-channel soils, demonstrating that the secular change is
at least in part controlled by in situ floodplain weathering. The simplest explanation for these changes relates to increased mean annual temperature, pCO2 , and seasonal fluctuations in water table height, all
of which promote mineral dissolution and precipitation reactions. Although the sensitivity to climate from weathering on hillslopes is well accepted, these findings newly demonstrate that weathering in
floodplains also responds to climate change.
University of Toronto/Royal Ontario Museum
June 29, 2021
From Weird Wonders to Spaceships: How New Burgess Shale Discoveries are Illuminating the Origin of Arthropods
Few fossil invertebrates can claim greater public enthusiasm than Anomalocaris. Not only is it alien-looking, but the story of its discovery – being pieced together from fragments thought to belong to different animals – is uniquely compelling. It is becoming increasingly clear, however, that Anomalocaris is not simply a one-off oddball. It belongs to a stem group of arthropods, called radiodonts for their distinctive, radial, toothed mouthparts. I will discuss some of the latest findings from the Burgess Shale and their contributions to our knowledge of these rare and enigmatic animals. New sites discovered by crews from the ROM over the past decade have yielded exceptionally well-preserved remains of radiodonts. These new species are no less bizarre than Anomalocaris itself, sporting frontal claws modified into mandible-like jaws or head carapaces shaped like the Millennium Falcon spaceship. Yet, the insights they provide about distributions, modes of life, development, and evolutionary history are helping to transform the radiodonts from inscrutable “weird wonders” to a model clade for understanding the origin of the arthropod body plan.
University of Notre Dame
June 22, 2021
Atmospheric circulation and precipitation patterns in the eastern Mediterranean during the late Quaternary (Marine Isotope Stages 1–5)
Existing proxy records from the eastern Mediterranean illustrate the region’s sensitivity to polar and tropical influences, with large fluctuations in vegetation documented on glacial-interglacial and millennial timescales. However, evidence for the underlying atmospheric mechanisms that drive precipitation variability, and ultimately changes in vegetation, remains sparse. At the Tenaghi Philippon (TP) peatland in northeastern Greece, the molecular distribution and hydrogen isotopic composition (δD) of sedimentary plant waxes can be used to reconstruct paleohydrology and changes in moisture source, thus providing insight into past atmospheric circulation patterns. In this presentation, I will introduce new, preliminary plant wax records from TP that span from ~7–140 ka and document changes in the westerly storm track associated with long-term and abrupt variability of regional forest cover, sapropel deposition periods, and early human migrations.
University of Edinburgh
June 15, 2021
The impact of environmental changes on the brain evolution of rodents and early placental mammals
Mammalian brain evolution has been studied since the late 1800s. More recently, the use of virtual endocasts has improved substantially our understanding of the behaviour of extinct mammals. Ecological factors and cataclysmic events have been seen as potential triggers for evolutionary change. Past studies have shown that adaptation to a new environment may specifically affect the nervous system. Squirrels and their closest relatives are a great model to test the relationship between locomotor behaviour and brain evolution, while early placental mammals can be used to explore the role of the end-Cretaceous extinction in the emergence of the brain of modern groups. The goal of this talk is to provide an overview of new and exciting findings on how the environment may influence brain evolution in placental mammals.
Watch on YouTube
University of Texas Institute for Geophysics
June 8, 2021
The Mid-Cretaceous Oceanic Anoxic Event 2 on the North American Coastal Plain
The Cretaceous was prone to global carbon cycle perturbations characterized by enhanced organic carbon burial and widespread anoxia in the oceans, called Oceanic Anoxic Events (OAEs). The last major global OAE was the Cenomanian-Turonian OAE2, which occurred roughly 94 Ma. Although this event is well known in the deep sea, records from continental margins are less-well developed. In the modern ocean, the majority of organic carbon burial occurs on continental margins, and so the lack of research in these areas in the Cretaceous represents a critical gap in our knowledge of both the drivers and effects of OAEs. This talk synthesizes recent work on OAE2 on the Gulf and Atlantic coastal plains of eastern North America to show the relationship between sea level rise, hydroclimate, and organic carbon burial in these environments. It also summarizes key outstanding questions requiring further investigation.
National Oceanographic Centre
University of Southampton
June 1, 2021
Surface ocean warming and acidification driven by rapid carbon release precedes the Paleocene-Eocene Thermal Maximum
The Paleocene-Eocene Thermal Maximum (PETM) is recognized by a major negative carbon isotope (δ13C) excursion (CIE) signifying an injection of isotopically light carbon into exogenic reservoirs, the mass, source, and tempo of which continues to be debated. Evidence of a transient precursor carbon release(s) is identified in a few localities, although a global signal remains equivocal. Continental shelf sites are advantageous as their relatively high sedimentation rates and limited carbonate dissolution yield expanded marine records, specifically over the CIE onset. I will present foraminiferal δ13C records from a marine continental margin section, which reveal a 1.0–1.5‰ negative pre-onset excursion (POE), and concomitant rise in sea surface temperature of at least 2°C (Mg/Ca paleothermometry). I used novel laser ablation multi-collector ICPMS to analyze δ11B (boron isotope) on individual benthic foraminifera to document a coupled decline in ocean pH. The recovery of both δ13C and pH before the CIE and absence of a POE in deep-sea records suggest very rapid (< ocean mixing timescales) carbon release, followed by recovery driven by deep-sea mixing. The carbon release during the POE is therefore likely much more similar in mass and rate than the main CIE to ongoing anthropogenic emissions.