Plenarist Abstracts

Contourites and mixed depositional systems: a paradigm for deepwater sedimentary environments

F. Javier Hernández Molina

Andalusian Earth Sciences Institute (IACT), Spanish Research Council (CSIC), Granada, Spain.
 

Along-slope bottom currents and a series of secondary oceanographic processes interact at different scales to form sedimentary deposits referred to as contourite and mixed (turbidite-contourite) depositional systems. Recent proliferation of both academic and industry research on deep-marine sedimentation documents significant advances in the understanding of these systems, but most non-specialists remain unaware of the features in question and how they form. Contourites and mixed depositional systems represent a major domain of continental margin and adjacent abyssal plain sedimentation in many of the world's oceans. They also appear in Palaeozoic, Mesozoic and Cenozoic stratigraphic sections. The growing interest in these systems has led to a refined but still evolving understanding of them. In addition to resolving their exact origins and evolutionary trajectories, research must also continue to ascertain their role in deep-sea ecosystems, geological hazards, environmental policy and economic development. Key gaps in understanding persist regarding their formation, their function in oceanographic systems and their evolution over time.
This Plenary Session summarises current conceptual paradigms for contourite and mixed depositional systems, lists global geographic examples of these systems and discusses their identification and interpretation in terms of diagnostic features as they appear in 2D and 3D seismic datasets and at sedimentary facies scale. It also considers the role that bottom currents play in shaping the seafloor and controlling the sedimentary stacking patterns of deepwater sedimentary successions. The growing interest in, and implications of, contourite and mixed depositional systems demonstrates that these systems represent significant deep-marine sedimentary environments. Combined efforts of researchers, industry partners and policy-makers can help advance understanding and responsible stewardship of deepwater depositional systems.
 

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Sustainable mining of critical raw materials: opportunities and obstacles for geoscientists

 Karen Hudson-Edwards

Camborne School of Mines and Environment and Sustainability Institute, University of Exeter, Penryn, UK.

The 'green' energy transition away from carbon-based fuels is driving a resurgence in mining because Earth materials are needed in renewable technologies such as battery-driven vehicles, solar panels and wind turbines. These technologies require specialist materials, many of which are known as Critical Raw Materials (CRMs). CRMs have high economic importance and a high supply risk. Variable CRM lists have been defined by different countries and regions (US, EU, Canada, Australia, etc.) but the lists often include metals such as Li, Co, REE and tungsten, and materials such as graphite and fluorspar. Globally, significant exploration and development of CRM deposits is in progress, with the aim of mining many of these to increase the supply of CRMs. To reduce the negative aspects of mining, and to respond to pressures from consumers, many companies have adopted a 'sustainable mining' policy to undertake mining that is profitable and maximises the flow of resources into circulation while protecting the environment and human rights and health. This presentation outlines opportunities and obstacles for geoscientists with respect to sustainable mining of CRMs. Opportunities include developing geomodels for previously understudied CRM orebodies and working in multidisciplinary teams to deliver innovation technologies and procedures along the whole mining value chain for the industry. Time constraints and integration of natural, engineering and social science research are some of the obstacles that will be discussed. Overall, geoscientists have a major leading role to play in the global sustainable mining of CRMs.
 

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The birth of the modern ocean and its first 180 million years of crises, speciations and extinctions

Elisabetta Erba
Università di Milano

 

Along with diatoms, cyanobacteria, and dinoflagellates, coccolithophores are key marine functional groups responsible for primary productivity, energy transfer, export of biogenic particles, and exchanges with the atmosphere. Coccolithophores are the most abundant calcifying organisms in the oceans, and their fossils are key for tracking global climate-ocean changes. The evolutionary history of calcareous nannoplankton, reconstructed from nannofossil records, shows increased diversity through the Mesozoic.
The rise of coccolithogenesis is a profound ecological innovation in the ocean ecosystem. Early Triassic nannofossils from South China help understand the circumstances prompting (or allowing) phytoplankton to mineralize calcite, marking the birth of the modern ocean. Coccolithophore origination shortly after the Permian mass extinction reset marine ecosystems, forcing biota to adapt to extreme climatic and chemical conditions and novel niches. The onset of coccolithogenesis began a long and successful evolutionary history of coccolithophores that influenced oceanic ecosystem dynamics, biochemical processes, and sedimentation. The geological history of coccolithophores indicates Mesozoic evolution characterized by increasing diversity, punctuated by speciations, "mass" extinctions, and turnovers that led to 25 coccolith/nannolith families and 5 groups Incertae sedis, peaking before the end-Cretaceous mass extinction.
Times of accelerated rates or drops in nannofossil diversification correlate with global changes in the geosphere, hydrosphere, and atmosphere, linking evolutionary patterns to environmental perturbations. Significant events in Mesozoic nannoplankton origination and evolution align with changes in CO2 concentrations, nutrient availability, ocean chemistry, and climate. Global environmental changes are interconnected with Earth's processes, and biosphere evolution should be linked to the Earth's interior. However, it is challenging (and contentious) single out causes triggering coccolithophore evolution and calcification; a combination of environmental changes likely drives evolutionary innovations and stability.
Mesozoic coccolithophore biodiversity and calcification patterns can assess their resilience: calcareous nannoplankton as a whole showed high resistance to global disturbances maintaining diversity and recovering post-disturbances, while individual taxa varied in resilience. Calcification patterns reveal moderate to lowered resilience, with different taxa showing varying sensitivity and resistance.
The response of coccolithophores in timing, magnitude, and recovery dynamics aids understanding the potential impacts of current and future global changes on marine ecosystems' adaptability and thresholds leading to ecological crises. Improved chronology of paleobiological and geological events is crucial for understanding evolutionary processes.