Scientific Webinars

Fates of World Major River-Derived Sediments to the Sea: Along-shore vs Cross-shelf Transport

Dr J. Paul Liu – North Carolina State University

Recent extensive geological and geophysical surveys over the world major river-dominated sea margins indicate that many rivers have developed largest proximal subaqueous deltas, with asymmetrical prodelta lobes, and elongated or detached distal masses of sediment. For example, the Amazon River’s sediment disperses >1500 km along the shore within the water depths of 60-70 m, and reaching the Orinoco River mouth; The Yangtze River sediment has transported ~800 km along the shore into the Taiwan Strait, and Yellow River sediment is deposited more than 700 km into the south Yellow Sea. Beyond the proximal depocenters near their river mouth, both the Yangtze and Yellow systems have developed a 40-m thick distal mud depocenters. The Mekong-derived sediment has also extended >250 km southwestwardly to the tip of the Ca Mau Peninsula, forming a distal mud depocenter up to 22 m thick, and extending into the Gulf of Thailand. Other major river systems, like the Irrawaddy, Mississippi, Nile, Po, Rhone, Pearl, Red, also have a large longshore-transported distal deposit with some typical underwater clinoform features. Only a few of the world major rivers are able to disperse their sediment directly or indirectly to the deep sea through the attached shelf canyon systems, like the Congo and Ganges-Brahmaputra.I will describe the unexpected discovery of pore fluids that, for the first time, appear to represent a direct archive of ancient seawater and to preserve the salinity and isotopic ratios of seawater from a past glacial period, likely the Last Glacial Maximum. These pore fluids were extracted from sediment cores from the Maldives Inner Sea, drilled in 2015 during IODP (International Ocean Discovery Program) Expedition 359 and penetrating late Oligocene to modern sediments. The composition of these fluids carries implications for glacial ocean circulation, water-rock interaction in platform systems, and preservation of carbonate sedimentary geochemistry.

An archive of glacial seawater and implications for carbonate platform sediments

Dr Clara Blättler – University of Chicago

I will describe the unexpected discovery of pore fluids that, for the first time, appear to represent a direct archive of ancient seawater and to preserve the salinity and isotopic ratios of seawater from a past glacial period, likely the Last Glacial Maximum. These pore fluids were extracted from sediment cores from the Maldives Inner Sea, drilled in 2015 during IODP (International Ocean Discovery Program) Expedition 359 and penetrating late Oligocene to modern sediments. The composition of these fluids carries implications for glacial ocean circulation, water-rock interaction in platform systems, and preservation of carbonate sedimentary geochemistry.

Always a White Christmas in the Bahamas: Ocean Chemistry & Hydrodynamics Focus Mud Production on GBB

Dr Sam Purkis – University of Miami

Whitings, or occurrences of fine-grained carbonate within the water column, have been observed in modern environments with salinities ranging from fresh to marine conditions, and thick deposits of lime mud are described throughout the geological record. Despite their ubiquity, the trigger for whitings has been a conundrum under debate for more than eighty years. This talk will review the trigger for whitings atop the Great Bahama Bank and call upon hydrodynamic simulation and geochemical modelling to explore the diverse triggers of the lime mud factory. The results have implications for the interpretation of whitings mud in the geological record, including the geochemical signatures within it.

A microbial ecosystem in the 3.48 Ga Dresser Formation, Pilbara, Australia

Dr Nora Noffke – Old Dominion University

The Archean Pilbara Block in Australia is known to host some of the oldest fossils in Earth history. This presentation focuses on microbially induced sedimentary structures (MISS) in clastic sabkha deposits of the Dresser Formation. Similarities of modern and fossil MISS suggest that already in the early Archean time complex microbial ecosystems existed.

The genesis of limestone-marl alternation on trial – testing an environmental proxy

Dr Theresa Nohl – Friedrich-Alexander University

The genesis of rhythmically alternating carbonate lithologies is a fundamental process which is not fully understood. In this presentation different models for their genesis, biases introduced by diagenetic processes, and solutions to handle data extracted from limestones and marls are discussed.

Hyperspectral imaging in sedimentary rocks at core and outcrop scale

Dr Hilary Corlett – MacEwan University

Full characterization of drill core and outcrops is time-consuming and requires multiple analytical techniques. Hyperspectral imaging can provide high-resolution spectra that may be interrogated for continuous mineralogical data, total organic carbon, and crystal size, to aid in strategizing an effective approach to sampling. Shortwave infrared (SWIR – 1 to 2.4 µm) and longwave (LWIR; 8 to12 µm) spectral imagery of shale drill core at a sub-millimeter per pixel scale reveals previously undetected trace fossils and sedimentary structures as well as distinct populations of amorphous and crystalline silica. Hyperspectral imaging can also be performed on outcrops and cliff faces, and is particularly useful in highlighting diagenetic phases in carbonates, where mimetic replacement and a lack of colour variation between mineral phases can result in an incomplete assessment of paragenesis. In an example of Cambrian dolomites from Western Canada, SWIR is used on an outcrop almost entirely composed of dolomite to detect individual phases, based on composition and crystal size.

Mixed siliciclastic-carbonate deposits: scales and heterogeneities

Dr Domenico Chiarella – Royal Holloway, University of London

Mixed siliciclastic-carbonate sediments result from the interaction of a siliciclastic input and a coeval carbonate production. Mixed deposits consist of a suite of different types of mixing between the two components, from bed to stratigraphic scales, producing a high vertical and lateral lithological variability. Although mixed deposits are very diffuse in the geological record, studies about these deposits are scrappy and not well encoded. Accordingly, mixed deposits can represent a labyrinth for researchers who want to investigate them for the first time. The aim of the talk is to highlight main aspects and their peculiarities.

Supercritical flows: the sedimentology of the illustrious upper flow-regime

Dr Arnoud Slootman – King Fahd University of Petroleum &Minerals

Bedforms are the morphological patterns on the sediment bed originating from coherent structures in fluid flows. The classical grouping of bedforms into the lower and upper regimes follows the transition from subcritical to supercritical flow as the Froude number passes a critical value. The revival of academic interest in supercritical flows and their products over the past two decades is attributed to the most recent addition to the supercritical palette: cyclic steps. This alternating pattern of subcritical and supercritical flow results from the flow overstepping the boundary between stable and unstable behaviour as predicted by the Vedernikov number. Waves at the upper flow boundary are key to understanding the transitions between the stable subcritical (ripples and dunes), stable supercritical (antidunes) and unstable supercritical (cyclic steps) regimes. In this talk we review our knowledge on the sedimentological aspects of supercritical flows and explore which questions remain to be answered.

Chasing earthquake and volcanism signals in a deep marine channel: the Hikurangi Channel New Zealand

Dr Lorna Strachan – University of Auckland

The deep marine Hikurangi Channel, located off the east coast of New Zealand, is a colossus. More than four times longer than any other located at an active continental margin, this trench-axis conduit can be traced for ~2000 km. Rapid continental uplift and frequent earthquakes associated with Hikurangi Subduction Margin and volcanic eruptions in the Taupō Volcanic Zone, together with active temperate weather systems mean that vast amounts of terrestrial, volcanic and shelfal sediment, nutrients, and (today) pollutants, are focussed through several canyons that feed the Hikurangi Channel. Recurrent powerful, sediment-laden underwater flows, known as turbidity currents, over the last 40,000 years, have left a remarkable and highly expanded greater than 100 m thick turbidite record that is allowing us to unravel the earthquake and volcanic signal of this margin over Quaternary timescales. Here I will discuss results from a large group of researchers working on understanding the Quaternary sedimentary systems of the Hikurangi Subduction margin. This will include preliminary results from IODP site 1520, together with multiple Holocene aged short cores (< 10 m thick).

The ugly duckling of coastal environments: Microtidal meanders and their deposits; A lesson from the Venice Lagoon (Italy)

Massimiliano Ghinassi – Università degli Studi di Padovav

Sedimentology of tidal meanders has received comparably much less attention than that of river meanders, and facies models for tidal point bars were developed in the shade of their fluvial counterparts, driven by the simplistic assumption that tidal and fluvial meanders are characterized by similar planform morphologies and dynamics, together with accretional and erosional processes along the inner and outer bank, respectively. This general lack of attention for tidal meanders runs parallel with their scarce documentation in the ancient record, a knowledge gap that contrasts with their widespread incidence in modern coastal plains, where they play a fundamental control on landscape evolution. Knowledge about tidal meanders and their deposits is even weaker when considering those developed in coastal regions characterized by a microtidal regime (e.g Mediterranean Basin, Gulf of Mexico and the Baltic Sea). The Venice Lagoon (Northeastern coast of Italy) includes a wide spectrum of meandering channels developed in a microtidal regime, and provides a unique laboratory to investigate their morphodynamic evolution and the related sedimentary products. The Venice Lagoon has a total surface of about 550 km2 and represents the largest brackish water body of the Mediterranean Basin. The Lagoon has an elongated shape trending NE-SW and has mean water depth of tidal flat and subtidal platform of about 1.5 m. It is connected to the sea through three inlets, where the maximum water excursion is ±0.75 m around Mean Sea Level. Nowadays, the Lagoon does not receive any relevant fluvial sediment supply, and is surrounded by densely-vegetated saltmarshes. Tidal channels are up to 15 m deep and form a complex network that drains saltmarshes, tidal flats and adjacent subtidal platforms. This talk will provide an overview on morphological and sedimentological processes concurring to shape these channels and build up related pointbar bodies. Specifically, it will illustrate planform geometries and migration rates of channel bends developed at different scales, and will depict depositional geometries developed under the interaction between lateral migration and vertical aggradation. The signature of tidal processes will be shown and compared with that recorded in deposits accumulated where tidal range is higher. Finally, stratal architecture and sedimentary facies distribution in subtidal pointbars will be also described.

The evolution of the Patagonian Ice Sheet from 35 ka to the Present Day (PATICE)

Dr Bethan Davies – Royal Holloway University of London

The Patagonian Ice Sheet was an ice sheet characterised by a wide variety of environments, including glaciolacustrine, land-terminating lowland lobes, high mountain glaciers and glaciomarine environments. It dammed large lakes that grew as it receded, which were an important control on ice dynamics. Here we present an overview of the variety of sediment-landform assemblages produced, and use these together with 1669 published ages to reconstruct Patagonian Ice Sheet evolution over the last 35,000 years, from the Last Glacial Maximum to the present day. We use these datasets to untangle the climatic and ice dynamical controls on ice recession, and find that current recession, driven by a persistent negative phase of the Southern Annular Mode, is exceptional within the Holocene.

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Advent of the Anthropocene Epoch ~1950 CE: Quantifying Drivers and Impacts

Jaia Syvitski – University of Colorado

Human energy expenditure in the Anthropocene (starting ~1950CE) is ~22 zetajoules (ZJ), and exceeds all human energy expended across the prior 11,700 years of the Holocene (at ~14.6 ZJ), largely through the combustion of fossil fuels. The global warming effect during the Anthropocene is more than an order of magnitude greater still. Global human population and their productivity and energy consumption are highly correlated and with most changes impacting the global environment: number of large dams; shrimp farming; industrial production of plastic, cement, ammonia, copper, gypsum, salt, iron, steel, sulfur, helium, aluminum; mineral species; atmospheric gases (CO2, N2O, CH4); terrestrial freshwater budgets; and surface temperatures, sea levels, and ice masses. This extraordinary outburst of energy and productivity demonstrates how it is that the Earth System in the past 70 years has departed from its Holocene state, forcing abrupt physical, chemical and biological changes to the Earth’s stratigraphic record that can be used to justify the proposal for naming a new epoch – the Anthropocene.

The world’s most unloved sedimentary structures: a new process model for flutes and tool marks

Professor Jeff Peakall – University of Leeds

Aggradational bedforms, from dunes to cyclic steps, are the subject of dozens of papers each year, producing lots of startling discoveries. These bedforms tell us about the flows that formed them and in turn aid interpretation and prediction. In contrast, sole structures have been almost entirely neglected for 50 years; unloved, ignored, and whose only role is to tell geologists which way the flow went. Here we present a new process model of flutes and tool marks in deep-marine environments that tackles a host of long-standing conundrums, and examines under what flow types these structures form. We finish by looking at the implications of the work including a revised Bouma Sequence diagram.

What can novel mixed sand-mud bedforms tell us about cohesive sediment gravity flow behaviour in the fringe of submarine fans?

Megan Baker – University of Durham

Bedforms are a key tool to reconstruct sedimentary processes in modern and ancient environments. This talk will present novel mixed sand-mud bedforms which have different shapes and sizes compared to pure-sand bedforms, and are found in the fringe of submarine fans. These striking mixed sand-mud bedforms are interpreted to be produced by sediment gravity flows with transient-turbulent fluid dynamics, due to the presence of cohesive clay. The presence and spatial trends in mixed sand–mud bedform types may be an important tool in interpreting fan fringe environments.

A journey through tides in Earth’s History

Professor Mattias Green – Bangor University

The scientific endeavours of the Apollo Lunar missions provided two important, yet apparently contradictory, pieces of information. The lunar rock samples aged the Moon at 4.5Gy, whilst laser ranging measurements of present day lunar recession, facilitated by reflectors left on the Moon, imply an age of only 1.5Gy. It is evident that least one of these estimates must be wrong! We now know that Earth, because of its current continental configuration, has a very energetic tide. Because the dissipation of tidal energy act as a break on Earth’s rotation and thus forces the moon to recede, it is also a first order controller of lunar distance. Is it possible that the motion of continents has changed the tides enough on geological scales to facilitate a weaker tide that can reconcile the two age estimates of the moon? Here, I am hoping to answer this question by going on journey through Earth’s history and estimating the tidal energetics for a series of interesting time slices. I will also touch upon what the consequences may have been for other parts of the Earth system and for other planets.

Salt on Mars: Astrobiological Tombs?

Kathleen C. Benison – West Virginia University

Kathleen is a science team member for Mars 2020, This talk will give an overview of halite and gypsum on Mars and describe their potential to host microorganisms and organic compounds as solid inclusions and within fluid inclusions – as salt minerals on Earth do. The talk will place the search for life in salt minerals on Mars in context of the sample return plan for the Perseverance rover.

Happy Earth Day! The Weird and Wonderful World of Sedimentology

Dr Jon Noad – SediMental Services

Join us as we explore the diverse world of Sedimentology. Drawing from a tranche of past BSRG talks and more, examples will be presented of sedimentary structures in ice and snow, the desert, the sky as well as more conventional settings. Prepare to be baffled by some real head scratchers and wowed by some of Earth’s largest ever structures, and finally head into space to speculate on the sedimentology of exoplanets.

Extreme Events Archives in the Geological Record of Deep-Sea Trenches (EAGER-Deep-Sea)

Dr Michael Strasser – University of Innsbruck

During the webinar we shall report our recent studies to survey and sample the ultra-deep water hadal trenches that allow an unravelling the earthquake history of subduction zones and provide new insight into sediment mass and carbon transfer into the hadal trench – one of the least-explored sedimentary environments on our planet.

Glacial Mars and its Morphological Mysteries

Dr Frances Butcher – University of Sheffield

In the present day, Mars’ mid-to-high latitudes host abundant water ice within diverse and stunning glacial landscapes. In this talk, I will explore the recent history of glaciation and glacial meltwater on Mars, and discuss some of the morphological mysteries that remain.