Yassine Ait Brahim
Mohammed VI Polytechnic University, Morocco
May 24, 2022
Speleothem based records of hydro-climate variability in Northwest Africa on orbital-millennial scales: Potential implications on pre-historic modern human populations
Paleoclimate information is still lacking in key regions to understand the functioning of some of the main components of Earth’s climate system. In NW Africa, the use of speleothems as a natural archive of past environmental and climate changes gained considerable interest in recent years. However, the published paleoclimate evidence in this region is still limited to the Holocene, whereas speleothems have a promising potential to span the past climate change throughout the Pleistocene with a high resolution.
In this presentation, we will talk about our published speleothem paleoclimate reconstructions that span the Holocene in Morocco, as well as our ongoing work and preliminary results during the last glacial cycle and throughout the Middle Pleistocene. We will highlight the advantage of using multi-proxy and high-resolution records in paleoclimate research and we will discuss the tug-of-war between the westerly winds belt and the African Monsoon in North Africa, the climate history of the Sahara, and the human-climate interactions across multiple timescales.
Team JOIDES Resolution
May 17, 2022
Special Event: Paleo-research at sea while on board JOIDES Resolution
For two months, scientists aboard JOIDES Resolution for Expedition 390 (South Atlantic Transect I) will be coring through sediment and drilling into ocean crust near the Mid-Atlantic Ridge to collect samples that will advance our knowledge in the chemical/physical changes in our ocean crust as it ages over time, how microscopic marine organisms living in marine sediment and rock have varied in abundance and diversity, and what records from the ocean floor can tell us about changes in climate from tens of millions of years ago
Three early career researchers (see details below) on board JOIDES Resolution Expedition 390 (South Atlantic Transect I). They will broadcast live from the ship and discuss how scientific ocean drilling provides the material to advance our knowledge of deep ocean environments past and present. This session will also include a tour of the ship and share what it is like to live and work at sea for two months. Website: https://joidesresolution.org/expedition/390/
We will also be joined by the cruise Onboard Outreach Officer – Dr. Laura Guertin (Penn State Brandywine, USA)
- Andrew McIntyre is a palaeoceanographer, interested in how ocean circulation and the climate has changed throughout the geological past, especially over the last 66 million years. He utilizes the geochemistry of microfossils found within marine sediments to reconstruct the evolution of water masses over time. Andrew is a PhD Candidate/Post Doctoral Research Associate in Palaeoceanography in the School of Environment, Earth & Ecosystem Sciences at The Open University, United Kingdom
- Claire Routledge is a calcareous nannofossil palaeontologist who studies the response of plankton to changes in climate and ocean conditions in the past. This is her second expedition as she has previously sailed on IODP Expedition 355 to the Arabian Sea. Claire is a Postdoctoral researcher in the Institute of Geosciences at the University of Kiel in Germany
- Yi Wang is a geochemist and paleoceanographer studying past oceanic oxygenation changes. She works with sediment and water samples.
Yi is a Postdoctoral Researcher in Geology & Geophysics at Woods Hole Oceanographic Institution in the USA
Université Grenoble Alpes, France
May 10, 2022
Investigating the early life on Earth with nanoscale X-ray synchrotron imaging
Deciphering the earliest records of life on Earth is a challenging undertaking, particularly regarding the undisputed identification of Precambrian microbial signatures that have been altered during deep time. Fossil microorganisms, in particular, have micrometric dimensions, simple morphologies, and a high degree of mineralization, that altogether challenge conventional analytical methods. In this talk I present how we are investigating some of the oldest fossil microorganisms and better understanding their fossilization processes using
synchrotron 3D nanoimaging. Obtaining both morphological and electron density information
at the ultracellular level is providing us unprecedented information Precambrian specimens, and also shedding light on nanoscale geochemical pathways. This 3D nanopaleontology is
allowing us to reassess early life records, with contribution also for astrobiology and the
search of fossil signatures in Mars.
University of Wyoming, United States
May 3, 2022
Elevation and climate records from Quaternary volcanic glass in the Ecuadorian Andes
Hydrogen isotope (δD) values of hydrated volcanic glass serve as a record of paleometeoric water and thus can be utilized in reconstructions of both paleoclimate and paleoelevation. We tested the applicability of volcanic glass δD values to paleoaltimetry in Pleistocene to Holocene (220–0 ka) hydrated volcanic glasses from ignimbrites deposited over a large (~4 km) elevation range spanning the Pacific coastal forearc and Andean magmatic arc of Ecuador (0°–1.5°S). The investigated ignimbrites were deposited during different climate conditions including cool glacial and warm interglacial climates. Data reveal robust isotope-elevation relationships that support the use of volcanic glass δD values in paleoaltimetry. Systematically lower δD values of glasses deposited during cooler climate conditions highlights exciting potential applications of the method to paleoclimate studies.
Harvard University, United States
26 April, 2022
Getting Crabby With It: On the Origins and Evolution of True Crabs
True crabs (Brachyura) are among the most iconic, speciose, and anatomically disparate groups of
crustaceans, whose origins and phylogenetic relationships remain unresolved. In this talk I present new, exceptionally-preserved fossils that shed light on the origins and evolution of crab-like forms (carcinization), and multiple convergent losses of a typical ‘crabby’ body plan (decarcinization) associated with the repeated invasions of novel environments (e.g., infaunal realm, pelagic zone). Although brachyurans originated in the Early Jurassic, it was during the Cretaceous Crab Revolution
when they underwent a major radiation, drastic anatomical experimentation, and conquered non-marine environments (e.g., land, freshwater) worldwide, leading to the modern groups seen today.
Federal University of Espirito Santo, Brazil
19 April, 2022
Taphonomy of aquatic insects from the Crato Formation Lagerstätte of Brazil under an actualistic look
The Crato Formation, a Konservat-Lagerstätte located in northeast Brazil’s Araripe Basin, is one of the most interesting fossiliferous deposits in the world. It represents a lacustrine paleoenvironment, which preserves a diverse entomofauna of the Cretaceous. The freshwater taxa from this unit are especially informative, however, they are still understudied. So far, most of the studies with fossil mayflies (Ephemeroptera), dragonflies and damselflies (Odonata) of the Crato Formation focused only on its taxonomy. Although aquatic insects from this deposit are ideal for taphonomical studies, especially some autochthonous mayflies’ groups. In this talk, I will present recently collected actualistic data that we have been using to assess taphonomical patterns of those aquatic insects of the Crato Formation, as well as the clues about the studied paleoenvironment that such data can provide.
University of California Santa Barbara
12 April, 2022
Time machine conservation: Reconstructing historical shark communities on coral reefs using dermal denticle assemblages
Sharks have often shown remarkable resilience to extinction over geological time, but in the blink of an eye, humans have pushed many shark populations worldwide to the brink of collapse. Without historical baselines to document what has been lost, it is challenging to implement meaningful management targets informed by natural variability and understand how the loss of these important predators has transformed ecosystems. In this talk, I will discuss how fossil shark scales (dermal denticles) can be used to reconstruct shark communities on coral reefs over the last several millennia. I will first introduce the methods we refined to isolate, identify, and interpret denticles preserved in the recent fossil record. I will then present two case studies that highlight how denticle assemblages can be leveraged to quantify variability in reef shark abundances before human impact and assess their resilience in the face of ongoing overfishing. These retrospective data, in turn, can provide valuable local context for recent shark declines and recovery potential.
Imperial College London
5 April, 2022
Was Thwaites Glacier smaller than present in the Holocene? Insights from cosmogenic nuclides in subglacial bedrock
Thwaites Glacier, roughly the size of Florida, contains enough ice to raise global sea level by about 0.65 metres. Along with neighbouring glaciers, Thwaites is undergoing the largest changes of any ice-ocean system in Antarctica, including rapid grounding line retreat. Most of our understanding of the history of glaciers like Thwaites is based on records of when they were larger than present. As Thwaites is getting smaller, we want to know if and when it has been smaller than present in the past, and under what environmental conditions. The talk will describe how we use cosmogenic nuclides in subglacial bedrock to shed light on the past of Thwaites Glacier.
Skye Yunshu Tian
University of Hong Kong
22 March 2022 @ 0900 UTC
Collapse and recovery of the shallow-marine ecosystem during the
Paleocene-Eocene Thermal Maximum
The Paleocene-Eocene Thermal Maximum (PETM), one of the best analogies to ongoing anthropogenic warming, triggered prominent and dynamic responses in global marine ecosystems. Compared with relatively well-studied deep-sea records of the PETM, shallow-marine biotic changes during this abrupt and transient hyperthermal event are much less understood yet equally important. Here I’m going
to present my recent work on a shallow-marine microfaunal record from Maryland, eastern United States, to document a clean-cut disturbance-recovery pattern of the
shallow-marine ecosystem during the PETM. With birth-death modeling that estimates local diversity dynamics, we discovered peak of species extirpation and
diversification predating the onset and at the final recovery phase of the PETM, respectively. Paleoecological analyses based on benthic ostracods reveal that bathymetric habitat compression due to extreme warmth and oxygen minimum zone expansion caused species extirpation during the peak PETM, and the shallow-marine ecosystem partially recovered from the PETM disaster with the introduction of new
Princeton University, United States
15 March 2022 @ 1500 UTC (US daylight savings)
Contracted oxygen-deficient zones during Cenozoic climate optima (Live Only!)
Over recent decades, the oxygen-deficient zones (ODZs) of the ocean have expanded, affecting marine ecosystems. However, their response to future global warming is poorly understood. In this talk, I discuss the response of ODZs during two periods of the past characterized by prolonged warmth: the Middle Miocene and Early Eocene climate optima (MMCO and EECO). I present new foraminifers-bound nitrogen isotope (FB-δ15N) data from Pacific ODP Site 872 and Atlantic DSDP Site 516. The new FB-δ15N data combined with existing data from Kast et al. (2019) are used to reconstruct the history of ODZ hosted water column denitrification across the Cenozoic. The results show decreased water column denitrification during both the MMCO and EECO indicating that ODZs were contracted, not expanded during these two periods of prolonged warmer climate. Timing of the denitrification decrease was closely coupled to high latitude warming and reduced meridional sea surface temperature gradients indicating that climate was the main driver of the observed changes. Possible causes for the decline in denitrification and corresponding reduction in ODZs include (i) a reduction in wind-driven equatorial upwelling and primary productivity, and/or (ii) an increase in deep-ocean ventilation.
University of Edinburgh, UK
March 8, 2022
The Rhynie chert in 3D, new insights into the earliest preserved terrestrial ecosystem
The 407 million-year-old Rhynie chert provides a unique window into an Early Devonian ecosystem teeming with life. Studies of the Rhynie chert over the last 100 years have provided enormous insights into early land plants, animals, fungi and a rich microbial community. However, there are still many unknowns about the Rhynie chert, most notably the macroscale features of the ecosystem. 3D digital reconstruction techniques provide a key resource for extracting new information from the Rhynie chert and the talk will describe how these techniques are changing our understanding of plant rooting systems.
March 1, 2022
Jurassic Giants: Exploring the Ecology and Evolution of Teleosauroids (Crocodylomorpha;
Teleosauroids, a group of Early Jurassic to Early Cretaceous crocodylomorphs, have long been thought of as relatively conservative compared to their sister taxa, the whale-like
metriorhynchids. However, this is far from the truth; they’ve been found to be very diverse in terms of morphology, habitat and feeding ecology. As such, they represent some of the most
successful, numerous and globally-distributed fossil crocodylomorphs. In addition, new work is now being done to examine teleosauroid biomechanics, growth/size distribution and ontogeny.